Title:
CONTINUOUS FLOW BIODIESEL PROCESSOR
Kind Code:
A1


Abstract:
A continuous flow biodiesel processor utilizing high turbulence mixing of oil being processed and a flow-through separation tank with distinct zones and recirculation draw tubes is described, along with methods for using same.



Inventors:
Ames, Randall S. (Valley, WA, US)
Application Number:
11/563680
Publication Date:
08/02/2007
Filing Date:
11/27/2006
Primary Class:
International Classes:
C10L5/00
View Patent Images:
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Primary Examiner:
LEUNG, JENNIFER A
Attorney, Agent or Firm:
WESLEY B. AMES (ESCONDIDO, CA, US)
Claims:
1. A continuous flow biodiesel processor for producing a lower alkyl fatty acid ester biodiesel from a glyceride solution, comprising a high turbulence flow-through processor mixer, a flow-through glycerol/biodiesel separator, wherein said glycerol/biodiesel separator receives output from said processor mixer, wherein glycerol is removed; and a biodiesel cleaner receiving biodiesel separated in said separator tank and removing polar components from said biodiesel.

2. The processor of claim 1, wherein said high turbulence flow-through processor mixer comprises a fluid cavity with proximate opposing surfaces, wherein said opposing surfaces comprise projections, and wherein at least one of said opposing surfaces rotates during use such that there is a relative velocity between said surfaces.

3. The processor of claim 2, wherein said first projections and said second projections bypass during rotation.

4. 4-9. (canceled)

10. The processor of claim 2, wherein said processor mixer comprises a housing and a generally circular rotor therein having a first face and a second face, wherein said rotor comprises a first set of projections on at least one of said first and second faces and said housing comprises a second set of projections on an inner surface proximate to said rotor face comprising said first set of projections.

11. The processor of claim 10, wherein said first set of projections consists essentially of a set of vanes.

12. The processor of claim 11, wherein said vanes include a set of concentric gaps, and said second set of projections include a matching set of concentric rings of projections that fit within said gaps.

13. 13-16. (canceled)

17. The processor of claim 1, wherein said glycerol/biodiesel separator comprises a zonal flow-through separation tank, wherein said tank receives output from said processor mixer; and wherein flow of partially reacted glyceride solution through said tank establishes a mixing zone, a separation zone, and a glycerol accumulation zone and accumulation of glycerol creates a glycerol/biodiesel interface within said tank, and glycerol below said interface is removed;

18. 18-20. (canceled)

21. The processor of claim 17, wherein said zonal flow-through separator tank comprises a tank of sufficient height and proportions that following injection of partially reacted glyceride solution in the top of said tank there is created a substantially stable upper mixed zone, a central stagnant zone, and a lower separated glycerol zone.

22. 22-30. (canceled)

31. The processor of claim 1, wherein said biodiesel cleaner comprises an ionically charged solid phase medium.

32. (canceled)

33. The processor of claim 1, further comprising at least one alcohol separator, wherein said separator removes alcohol from said biodiesel or from said glycerol or both.

34. 34-47. (canceled)

48. A scalable processor for production of biodiesel, comprising a plurality of parallel-linked high turbulence flow-through processor mixers which can be operated or idled independently to produce a biodiesel solution from a glyceride solution; at least one flow-through glycerol/biodiesel separator functionally linked with said mixers to accept a glycerol/biodiesel mixture processed through at least one of said processor mixers; at least one biodiesel cleaner functionally linked with said glycerol/biodiesel separator to separate polar components from said biodiesel solution.

49. (canceled)

50. The processor of claim 48, wherein said high turbulence flow-through processor mixer comprises a fluid cavity with proximate opposing surfaces, wherein said opposing surfaces comprise projections, and wherein at least one of said opposing surfaces rotates during use such that there is a relative velocity between said surfaces.

51. (canceled)

52. The processor of claim 50, wherein said processor mixer comprises a hollow outer housing comprising an inner surface having a plurality of first projections, and a proximate spaced apart inner body having an outer surface comprising a plurality of second projections, wherein said outer housing and said inner body rotate relative to each other.

53. 53-95. (canceled)

96. A processor for production of biodiesel from a glyceride solution comprising a sequentially linked plurality of processor units, wherein each said processor unit comprises a high turbulence flow-through processor mixer; and a residence chamber following said processor mixer; a linked glycerol/biodiesel separator receiving reacted glyceride solution from said processor unit; and a biodiesel cleaner receiving biodiesel from said separator.

97. 97-105. (canceled)

106. The processor of claim 96, wherein said processing system is transportable.

107. The processor of claim 106, wherein said processor units are installed in a volume not exceeding 70 m3.

108. 108-109. (canceled)

110. The processor of claim 96, wherein said high turbulence flow-through processor mixer comprises a fluid cavity with proximate opposing surfaces, wherein said opposing surfaces comprise projections, and wherein at least one of said opposing surfaces rotates during use such that there is a relative velocity between said surfaces.

111. The processor of claim 110, wherein said first projections and said second projections bypass during rotation.

112. 112-124. (canceled)

125. The processor of claim 96, wherein said glycerol/biodiesel separator comprises a zonal flow-through separation tank, wherein said tank receives output from said processor mixer; and wherein flow of partially reacted glyceride solution through said tank establishes a mixing zone, a separation zone, and a glycerol accumulation zone and accumulation of glycerol creates a glycerol/biodiesel interface within said tank, and glycerol below said interface is removed;

126. The processor of claim 125, wherein said zonal flow-through separator tank comprises an upper mixing zone, a middle separation zone separated from said upper mixing zone by a baffle plate, and a lower glycerol accumulation zone.

127. 127-201. (canceled)

Description:

RELATED APPLICATIONS

This application claims the benefit of Ames, U.S. Provisional Appl. 60/740,346 filed Nov. 28, 2005, which is incorporated herein by reference in its entirety, including drawings.

FIELD OF THE INVENTION

The present invention relates to the production of lower alkyl fatty acid esters from glycerides, and in particular to the production of biodiesels.

BACKGROUND OF THE INVENTION

The following discussion is provided solely to assist the understanding of the reader, and does not constitute an admission that any of the information discussed or references cited are prior art to the present invention.

A number of systems for producing alkyl esters from fatty acid solutions have been described. Most such systems are batch processing systems, in which the feed oil is mixed under low or medium mixing rates with a basic catalyst (e.g., NaOH or KOH) and a lower alcohol such as methanol or ethanol. The mixture is placed in reaction and separation tanks where the fatty acids are allowed to react. The product alky esters and glycerin are allowed to separate by gravity and the glycerin is removed from the tank.

A number of systems are described in patent documents. For example, Hooker, U.S. Patent Appl. Publication 2005/0027137 indicates that it describes an “apparatus and method for producing fatty acid alkyl esters from fatty acids derived from vegetable oils and animal fats” in which a mixture is emulsified as a means to reach a completed reaction state in a reaction section and “transesterification occurs when the natural boundary surfaces of the immiscible mixture are enlarged by ultrasonic cavitation in the reaction section and the transesterification is performed at, or near, atmospheric pressure.” (Hooker, Abstract.)

Ergun, U.S. Pat. No. 6,440,057 describes a method for producing fatty acid methyl ester from at least one of vegetable and animal with an alkaline solution dissolved in alcohol to form a mixture and emulsifying the mixture to reach a chemical balance state in a reaction section, wherein fats are transesterified into fatty acid methyl ester, wherein border surfaces of the mixture are enlarged by dynamic turbulence in the reaction section and the transesterification is performed under pressure, and wherein the pressure is reduced during transesterification. The method further includes separating residues from the fatty acid methyl ester in a phase separation section after reaching a chemical balance state.

Certain systems are described that are indicated to produce biodiesel in a continuous flow manner.

Lastella, U.S. Patent Appl. Publ. 2005/0081435 states that it “achieves continuous flow through all the reaction vessels and separation tanks without the need for additional pumps.” Further, the system “preferably employs preferably closed tanks (though preferably not sealed) to provide for methanol recovery, and may include vertical rotating feed tubes having separators and inlet and outlet openings.” (Lastella, paragraph 12.)

Connemann et al. U.S. Pat. No. 5,354,878 describes a process wherein an “oil phase of fatty triglycerides or natural oils or fats containing free fatty acids is subjected to catalytic transesterification”, in which the improvement involves a multistep sequential process of a) introducing a reaction mixture into the top of a reaction column, b) transferring the column transesterification product to a second reactor, c) washing the reaction mixture with an aqueous extractant in a first separator, d) introducing the washed reaction mixture with additional alcohol and catalyst into a third reactor, e) introducing the resulting mixture into a fourth reactor and maintaining the mixture under stirring for a further transesterification forming a reaction product having a degree of transesterification of at least 99.2%, f) introducing the resulting transesterification product and hot, aqueous extractant into a second separator, and g) drying the transesterification product.

Hanna, U.S. Patent Appl. Publ. 2003/0032826 describes a transesterification process for the production of biodiesel, where the process involves introducing the triglycerides and a catalyst into a reaction zone and introducing an alcohol into the feed stream within the reaction zone, where the triglyceride feed stream is characterized by having a Reynolds number of at least about 2100.

Connemann et al., U.S. Patent Appl. Publ. 2005/0204612 describes “a process for the continuous production of biodiesel from a biogenic initial feedstock mixtures containing fat or oil with a high content of free fatty acids, as well as a device for the production of biodiesel.”

SUMMARY OF THE INVENTION

In view of the great demand for oil-based fuels, and in particular for motor vehicle fuels, there is an increasing need for alternatives to petroleum products. One such alternative is biofuels, and particularly biodiesel. Biodiesel is generally produced from oils and/or fats from plant and/or animal origin by esterification of glycerides and/or free fatty acids under basic or acidic conditions in the presence of a lower alkyl alcohol.

The present invention concerns simple systems typically operable at atmospheric pressure (although also adaptable for higher pressures) for producing biodiesel, especially from vegetable oils. These systems provide continuous flow systems, system components, and methods for processing glycerides (e.g., triglycerides) to produce alkyl esters, i.e., lower alkyl fatty acid ester solutions useful as biodiesel, from vegetable and/or animal oils and fats. Certain embodiments of the present systems include a high turbulence processor mixer and/or a functionally linked zonal flow-through separation tank.

Thus, in a first aspect the invention provides a continuous flow biodiesel processor for producing a lower alkyl fatty acid ester biodiesel from a glyceride solution that includes a high turbulence flow-through processor mixer, a glycerol/biodiesel separator (e.g., a zonal flow-through separation tank), and a biodiesel cleaner. In this processor, the glycerol/biodiesel separator receives output (e.g., at least partially reacted glyceride solution mixed with a lower alkoxide in alcohol solution (e.g., methanolic sodium methoxide) or a lower primary alcohol and a catalyst (e.g., a base catalyst such as NaOH or KOH)) from the processor mixer. The biodiesel cleaner receives biodiesel separated in the separator tank and removes contaminants, e.g., polar components such as residual glycerol, unreacted alcohol, water, and/or other components soluble in the alcohol and/or water, from the biodiesel.

The present components (e.g., high turbulence processor mixers and/or flow-through zonal separator tanks) can be incorporated or combined in a variety of systems and used in various methods. Thus, in a related aspect, the invention concerns a system for production of biodiesel, where the system includes an oil (i.e., glyceride solution) supply (e.g., an oil storage tank), a high turbulence flow-through processor mixer (e.g. as described herein), a glycerol/biodiesel separator (e.g., a flow-through zonal separation tank as described herein) that receives reacted glyceride solution from the processor mixer, a biodiesel cleaner, and a biodiesel receiver.

In another aspect, the invention concerns a scalable processor for production of biodiesel from glyceride solutions; the processor includes a plurality of parallel-linked high turbulence flow-through processor mixers (e.g., as described herein) which can be operated or idled independently, at least one flow-through glycerol/biodiesel separator (e.g., a flow-through zonal separator tank) functionally linked with those processor mixers to accept a glycerol/biodiesel mixture processed through at least one of the processor mixers, and at least one biodiesel cleaner functionally linked with the glycerol/biodiesel separator to separate contaminants, e.g., polar components from the biodiesel solution.

In many cases, the plurality of processor mixers is 2-4, i.e., 2, 3, or 4, processor mixers.

In certain embodiments, the system includes a plurality of separator tanks; the plurality of tanks includes a separate tank functionally linked with each of a plurality of processor mixers (e.g., with each processor mixer); one or more separator tanks is supplemented with one or more centrifuges; one or more separator tanks are replaced with a centrifuge; each separator tank is replaced with a centrifuge.

Processor mixers can also advantageously be linked in a sequential manner with residence chambers between each. Thus, another aspect provides a processor for production of biodiesel from a glyceride solution that includes a sequentially linked plurality of processor units (e.g., 2, 3, 4, 5, 6, 7, 8, 9, 10, 2-5, 6-10, 11-15 sequential units) where each processor unit includes a high turbulence flow-through processor mixer and a residence chamber following the processor mixer. The system further includes a linked glycerol/biodiesel separator receiving processed glyceride solution from the processor unit (which may be integral or separate from the residence chamber), and a biodiesel cleaner receiving biodiesel from the separator.

In certain embodiments, the glycerol separator includes a centrifuge, flow-through separation tank, and/or a cyclone; a plurality of processor units (e.g., each processor unit) include a glycerol separator, such as a separator including or consisting of a centrifuge, a separation tank, and/or a cyclone.

In particular embodiments, the residence chamber includes, consists essentially of, or consists of a pipe; the residence chamber includes a tank; a pipe residence chamber includes internal baffles; flow in a pipe residence chamber is plug flow; the residence time in the residence chamber is 0.5-1.0, 1.0-2.0, 2.0-5.0, 5.0-10.0, 1.0-5.0, 1.0-10.0, or 2.0-7.0 minutes; a processor including pipe residence chamber is operated under pressure greater than 1 atmosphere (e.g., 1.2-2, 2-3, 3-4, 4-6, 6-10, 10-20, 20-50, 50-100, 100-150, 150-200 atmospheres (atm), at least 2, 3, 4, 5, 6, 10, 20, 50, 100, 150, 200 atm).

In particular embodiments, the processor is transportable; the processor units are installed in a volume not exceeding, 5, 10, 20, 30, 40, 50, 60, or 70 m3; the processor units of a transportable processor are installed in a standard 20-foot or 40-foot shipping container; the processor components of a processor are mounted in a volume not exceeding 5, 10, 20, 30, 40, 50, 60, or 70 m3 with the exception of the glyceride solution supply and biodiesel storage, and optionally an alcohol recovery system and a biodiesel cleaner.

In some processors, the processor combines scalable and sequential features. In such aspects or embodiments, the processor includes a plurality of parallel-linked processor mixers that can be operated or idled independently, and at least one of the processor mixers (e.g., 1, 2, 3, 4, or all) is sequentially linked with at least one other processor mixer with a residence chamber between them. In certain embodiments, the scalable feature is as described herein for scalable processors and/or the sequential features are as described herein for sequential processors.

In certain embodiments of the above aspects, the high turbulence processor mixer has a fluid cavity with at least two proximate opposing surfaces. Those opposing surfaces include projections, and at least one of the opposing surfaces rotates during use such that there is a relative velocity between the surfaces. Such rotation can be created by rotation of either surface, or counter-rotation of both. In some designs, the first projections and second projections bypass during rotation.

In particular embodiments, the processor mixer includes a hollow outer housing that has an inner surface having a plurality of first projections, and a proximate spaced apart inner body (located within the hollow outer housing) having an outer surface that has a plurality of second projections, where the outer housing and the inner body rotate relative to each other. In certain embodiments, the inner surface of the outer housing has a first cylindrical surface, and the outer surface of the inner body has a second cylindrical surface; the first and second cylindrical surfaces are separated by an annular gap; rotation is about a common longitudinal cylindrical axis; the longitudinal axis of the second cylindrical surface is offset from the longitudinal axis of the first cylindrical surface; the second cylindrical surface is rotated and the first cylindrical surface is fixed; the relative velocity of the first and second cylindrical surfaces is at least 10, 15, 20, 25, 30, 10-20, 20-30 meters per second (m/s); at least some of the projections (e.g., at least 10%, a majority, or substantially all) include a substantially flat trailing edge surface having sharp corners and oriented substantially perpendicular to the rotation direction; at least some of said projections have a tapering trailing surface (e.g., at least 10%, a majority, or substantially all).

In certain embodiments, the processor mixer includes a housing and a generally circular rotor within that housing. The rotor has a first face and a second face, and the rotor has a first set of projections on at least one of its first and second faces. The housing includes a second set of projections on an inner surface proximate to the rotor face that has the first set of projections. In certain embodiments, the first set of projections includes a set of vanes; the vanes include a set of concentric gaps, and the second set of projections include a matching set of concentric rings of projections that fit within those gaps; the housing also includes a third set of projections on the inner surface proximate the distal ends of the rotor vanes; the rotor vanes also include at least one groove in their distal ends and the housing further includes a third set of projections on the inner surface proximate the distal ends of the vanes and the third set of projections project into that groove; rotation of the rotor is driven by a central shaft driven by an external power unit; rotation of the rotor is magnetically coupled to an external power unit.

In another variant, the processor mixer includes one or more centrifugal pumps (e.g., unmodified pumps). In this usage, the centrifugal pump can (but does not necessarily) provide both pump and mixing function. While a single such pump can be used, it can be advantageous to use a plurality of pumps, in which at least one pump is oriented as a forward acting pump and at least one pump is oriented as a reverse acting pump. These centrifugal pumps should be configured so that there is a net forward flow. Such forward flow can be maintained, for example, by using an independent pump of any appropriate type that has sufficient pressure and flow capacity to overcome the reverse action of any reverse acting centrifugal pumps in the system. Alternatively centrifugal pumps can be arranged such that at least one of those pumps provides a net forward flow, overcoming the sum of the reverse acting pumps. Such arrangements are particularly suitable for the sequential processors described below. In such sequential systems, the pumps can, for example, be arranged in pairs with one pump forward acting and one pump reverse acting, such that the forward acting pump either equals or exceeds the action of the reverse acting pump. In cases where the forward action and reverse action are equal, the forward flow can be provided by an earlier pump in the system that provides a sufficient net forward pumping action.

In certain embodiments, the glycerol/biodiesel separator includes a zonal flow-through separation tank (alone or in conjunction with other separation components), where the tank receives output from the processor mixer (e.g., as described above) and flow of reacted glyceride solution through the tank establishes a mixing zone, a separation zone, and a glycerol accumulation zone. Accumulation of glycerol creates a glycerol/biodiesel interface within the tank, and glycerol below the interface is removed. Such tank can include a secondary recycling draw tube located above and proximate to the glycerol-biodiesel interface, through which partially reacted glyceride solution is drawn.

In particular embodiments, the zonal flow-through separator tank has an upper mixing zone, a middle separation zone separated from said upper mixing zone by a baffle (e.g., a baffle plate), and a lower glycerol accumulation zone; the baffle (e.g., baffle plate) includes a generally horizontal disk with a peripheral, downwardly projecting skirt; the generally horizontal disk is centrally located; the generally horizontal disk is centrally located with a gap between the disk and the wall of the tank; the area of the generally horizontal disk is at least 60%, 70%, 80%, 90%, 60-80%, 70-90%, 80-99% of the internal cross-sectional area of the tank.

In particular embodiments, the zonal flow-through separator tank includes a first tank and a second tank, where the first tank provides a mixed zone (e.g., in which partially reacted glyceride solution is mixed and produces reacted glyceride solution) and the second tank provides a stagnant separation zone in which reacted glyceride solution is not substantially mixed such that glycerol separates from biodiesel.

Also in particular embodiments, the zonal flow-through separator tank includes a tank of sufficient height and proportions that following injection of partially reacted glyceride solution in the top of said tank there is created a substantially stable upper mixed zone, a central stagnant zone, and a lower separated glycerol zone. Such tank dimensions are generally tall and thin such that mixing at the top of the tank does not substantially mix a central portion so that separation can occur, and glycerol accumulates in the bottom portion. Such tank can include a biodiesel port located in the separation zone within a volume defined by a downwardly opening surface (e.g., a circular cylinder open at one end, an open-ended rectangle, a surface of rotation, and the like) where the downwardly opening surface does not occupy such a large fraction of the cross-sectional area of that tank that it acts as a baffle that substantially inhibits mixing below that surface (e.g., occupies less than 60%, 50%, 40%, 30%, 20%, 10% of the tank cross-sectional area.

In particular embodiments, the glycerol/biodiesel separator includes a cyclone; the glycerol/biodiesel separator includes a centrifuge; the glycerol/biodiesel separator includes a cyclone and a flow-through zonal separation tank; the glycerol/biodiesel separator includes a cyclone and at least one centrifuge; the glycerol/biodiesel separator includes a flow-through zonal separation tank and a centrifuge (e.g., where the centrifuge receives output from the middle separation zone of the tank); the glycerol/biodiesel separator includes a plurality of centrifuges.

In certain embodiments of the processor, the biodiesel cleaner includes a washer; the biodiesel cleaner also includes a water/oil separator in which a centrifuge receives the biodiesel and water mixture from the washer and separates the biodiesel from the water and water soluble components; at least 99.5% by volume of the water added in the washer is removed from the biodiesel; the residual water in the biodiesel after processing is less than 0.5%, 0.4%, 0.3%, or 0.2%; the biodiesel cleaner includes a water mixer in which water is mixed with biodiesel to form a biodiesel/water mixture followed by a settling tank in which at least 50%, 60%, 70%, 80%, 90%, or 95% of the water is removed from the biodiesel/water mixture; the biodiesel cleaner includes a water mixer in which water is mixed with biodiesel to form a biodiesel/water mixture followed by a cyclone in which at least 50%, 60%, 70%, 80%, 90%, or 95% of the water is removed from the biodiesel/water mixture; the biodiesel cleaner includes an ionically charged solid phase (e.g., particulate) medium (e.g., MAGNASOL®).

In certain embodiments, the processor further includes at least one alcohol separator where that separator removes alcohol from the biodiesel or from the glycerol or from both; an alcohol separator includes an evaporative separator; the processor also includes an evaporative alcohol separator that removes alcohol from the biodiesel and an evaporative alcohol separator that removes alcohol from the glycerol; an evaporative alcohol separator includes a vacuum evaporator; a vacuum evaporator includes at least one pressurized spray nozzle; an evaporative separator includes a heated vaporizer; a heated vaporizer also includes at least one pressurized spray nozzle; a heated vaporizer also incorporates a vacuum unit (e.g., a vacuum tank); a vacuum and/or heated vaporizer is linked with a condenser; an alcohol separator includes a nanofiltration unit.

In certain embodiments, the processor also includes an oil heater before the processor mixer; mixing of oil in the processor mixer causes at least a 0.1, 0.2, 0.5, 1.0, 2.0, 5.0, 10.0 degree Celsius rise in the temperature of the glyceride solution; the processor is capable of processing at least 10, 20, 30, 40, 50, 80, 100, 200, or 400 liters per minute of glyceride solution; the processor includes a heated vaporizer (e.g., for vaporization of alcohol from biodiesel or glycerol, or for vaporization of water from biodiesel, or for distillation of glycerol) connected with a heat exchanger in which heat is recovered from the material heated in said vaporizer and used to heat a glyceride solution (e.g., an initial feedstock glyceride solution); the processor includes an alcohol recover unit; an alcohol recovery unit includes a vaporizer (e.g., heat and/or vacuum vaporizer) and may include a condenser; an alcohol recovery unit includes a nanofiltration unit.

A related aspect concerns a continuous flow separation tank for separation of components of a liquid mixture that form separate phases. The tank defines a liquid-containing volume, and thus includes a container that has sides, and a closed bottom. The tank also includes a baffle such as a generally horizontal baffle plate (e.g., in the central portion of the container or around the periphery), a low density liquid draw tube located below and proximate to (close to) the baffle plate; and a high density liquid draw tube located proximate to the lower internal terminus of the bottom.

In advantageous embodiments, the baffle plate is configured such that the plate inhibits fluid currents transferring from the mixing zone to the separation zone. Removal of biodiesel and/or glycerol from below the baffle plate will cause a limited current as reacted glyceride solution from the mixing zone moves into the separation zone to replace the withdrawn fluid. Preferably, this current is localized and separated from the biodiesel draw tube (biodiesel port), so that the downward flow of replacement fluid is not directed toward that tube opening. Instead the replacement fluid is directed toward the glycerol biodiesel interface, so that biodiesel rises and/or moves laterally toward the biodiesel draw tube opening while the glycerol continues to sink toward the interface and adds to the separated glycerol. Thus, the biodiesel draw tube opening is placed so that fluid drawn through that tube is enhanced in biodiesel content without the long settling times required for non-partitioned tanks.

In particular embodiments, the bottom includes an inverted cone section, a generally hemispherical section; an arcuate section, a reduced diameter section.

In certain embodiments, the baffle includes a generally horizontal plate. Such baffle plate preferably includes at least a portion that is not perforated. In certain embodiments, the baffle also includes a generally vertical skirt surrounding an area defining a downwardly opening cavity.

Instead of a generally horizontal plate, the baffle can be of other shapes that similarly create an upwelling or lateral migration volume, e.g., creates a downward opening cavity. For example, the baffle may be or include a cone, inverted hemisphere, inverted parabolic surface, inverted arcuate surface, or other downward opening curved surface of rotation. In such cases in which at least a portion of the baffle and/or other surface define a downwardly opening cavity (i.e., defining an upwelling volume), the biodiesel draw tube is typically located above the lower edge of the surface, preferably near the top of the volume. Likewise the baffle may include a perforated surface and a non-perforated, downward-opening surface that is integrated with or located below that perforated surface.

In certain embodiments, the separation tank includes an intermediate draw tube located above and proximate to the interface between the phases formed from the liquid mixture; the sides of the tank include or are in the form of a hollow, generally circular cylinder; the baffle plate includes a horizontal plate portion with a downwardly projecting skirt, e.g., a peripheral skirt; the area of horizontal plate portion is at least 60%, 70%, 80%, 90%, 95% of the horizontal cross-sectional area of the tank at the location of the plate portion; the tank has a liquid capacity of at least 1000, 2000, 3000, 5000, 10,000, 20,000, 40,000 liters.

Another related aspect concerns a high turbulence flow-through processor mixer that includes a fluid cavity with proximate opposing surfaces. Those opposing surfaces include projections, and at least one of opposing surfaces rotates during use such that there is a relative velocity between said surfaces (the opposing surfaces may counter-rotate).

In certain embodiments of the processor mixer, the first projections and second projections bypass during rotation.

In certain embodiments, the processor includes a hollow outer housing that includes an inner surface that has a plurality of first projections, and a proximate spaced apart inner body that has an outer surface that has a plurality of second projections, where the outer housing and the inner body rotate relative to each other; the outer housing includes an inner first cylindrical surface and the inner body includes an outer second cylindrical surface, where the first and second cylindrical surfaces are separated by an annular gap, and the relative rotation is about a common longitudinal cylindrical axis; the second cylindrical surface is rotated and the first cylindrical surface is fixed; the relative velocity of the first and second cylindrical surfaces is at least 2, 5, 10, 20, 30, 40, 50 meters per second (m/s) or is in a velocity range defined by taking any two different specified velocity values as endpoints of the range; at least some of said projections include a substantially flat trailing edge surface having sharp corners and oriented substantially perpendicular to the rotation direction; at least some of the projections include a substantially flat leading edge with sharp corners; at least some of said projections include a tapering trailing surface, e.g., with a flat, curved, or obtuse angled leading surface.

In certain embodiments, the processor mixer includes a housing and a generally circular rotor therein having a first face and a second face, in which the rotor includes a first set of projections on at least one of the first and second faces and the housing includes a second set of projections on an inner surface proximate to the rotor face that has the first set of projections; the first set of projections includes or is essentially a set of vanes (e.g., vanes of the type typically used in centrifugal liquid pumps); the vanes include a set of concentric gaps, and the second set of projections include a matching set of concentric rings of projections that fit within those gaps; the vanes also include at least one groove in their distal ends (i.e., at the periphery of the rotor) and the housing also includes a third set of projections on the inner housing surface proximate to those distal ends, where the third set of projections project into the groove; wherein rotation of the rotor is driven by a central shaft driven by an external power unit; rotation of the rotor is magnetically coupled to an external power unit.

Another related aspect concerns a method for processing a glyceride solution to produce lower alkyl fatty acid esters by continuously processing a glyceride solution in a processor mixer as described herein to produce a fatty acid alkyl ester solution, and separating glycerol from the lower alkyl fatty acid ester solution, and/or by using a zonal flow-through separator tank as described herein to effect such separation. The method can also include the use of other components and steps as described for biodiesel production.

In another related aspect the invention provides a method for modulating output from a biodiesel processor by altering the number and/or selection of processor mixers operating in a scalable biodiesel processor as described herein. Such modulation can be an increase in output by addition of operation of a processor mixer in an operating biodiesel processor and/or by substituting a higher capacity processor mixer for a lower capacity processor mixer. Conversely, such modulation can be a decrease in output by removal of a processor mixer from operation while leaving at least one operating processor mixer and/or by substituting a lower capacity processor mixer for a higher capacity processor mixer.

Yet another related aspect concerns a method of producing a lower alkyl fatty acid ester solution from a glyceride solution by using a sequentially linked plurality of processor units, e.g., in a system as described above, separating glycerol from lower alkyl fatty acid esters in the glycerol separator to produce a lower alkyl fatty acid ester solution, and cleaning said lower alkyl fatty acid ester solution in said biodiesel cleaner.

In particular embodiments, the method also includes the use of an alcohol recovery unit, e.g., an alcohol recovery unit that includes an evaporator and condenser or a nanofiltration unit separating glycerol from the alcohol; alcohol recovered in the alcohol recovery unit is recycled through the processing system.

Another aspect concerns a method for flow-through processing of a glyceride solution to produce a fatty acid alkyl ester solution by continuously mixing the glyceride solution in a processor mixer (e.g., a flow-through high turbulence mixer); extending the reaction in a separation tank; separately removing glycerol, fatty acid alkyl ester solution, and partially reacted glyceride solution from said separation tank; and reprocessing the removed partially reacted glyceride solution together with additional unreacted glyceride solution through the processor mixer and separation tank.

In particular embodiments, the processor mixer and separation tank are as described herein. The system utilized in this method can also include additional components and steps for biodiesel processing, e.g., as described herein.

Another aspect involves a method for separating solution components of a liquid mixture in a biodiesel/glycerol solution where the liquid mixture forms two different phases on standing by injecting partially reacted glyceride solution into a separation tank wherein the tank includes a closed top, a cylindrical central portion, a closed, reduced cross-sectional area bottom portion, an inlet injection tube proximate to the top, a baffle plate in the central portion, a first draw tube below and proximate to the baffle plate, a glycerol phase detector functionally connected to a valved drain tube proximate to the lower interior terminus of the lower portion; extracting glycerol from the bottom of the tank through the valved drain tube, and extracting fatty acid alkyl ester solution from a region in the tank below and proximate to the baffle plate.

The tank may be as described for a zonal separation tank containing a baffle plate as described herein.

The method can also include extracting partially reacted glyceride solution from above and proximate to a glycerol/oil interface in the tank through a second draw tube.

The invention, in another aspect, also provides a method for enhancing the extent of reaction in a biodiesel processor including the continuous process of mixing unreacted glyceride solution with a C1-C3 primary alcohol and a base catalyst (or solution of a lower alkoxide in a C1-C3 primary alcohol) through a high turbulence processor mixer to form a first mixture containing glycerol and biodiesel, separating biodiesel from glycerol in a separation tank, removing biodiesel and glycerol from the separation tank, and removing and mixing partially reacted glyceride solution from the separator tank with unreacted glyceride solution to form a second mixture, passing the resulting second mixture through the high intensity processor mixer together with additional first mixture, passing the reprocessed second mixture combined with first mixture through the separation tank, and continuously repeating the process.

The invention further provides a method for enhancing the reaction level of alcohol in a biodiesel processor. The method involves use of a flow-through biodiesel processor and includes continuously separating a first glycerol/alcohol mixture containing un-reacted alcohol and catalyst from biodiesel, mixing that glycerol/alcohol mixture containing un-reacted alcohol and catalyst with un-reacted (or less-reacted) glyceride solution forming a recycling reaction mixture, and processing the secondary reaction mixture through the processor.

In general, the method involves taking an alcohol-rich (e.g., methanol- or ethanol-rich) glycerol fraction from a later stage in a multi-step biodiesel production process and utilizing that fraction in an earlier step, either alone or with enrichment with fresh methanol and/or catalyst. The result is that at least most of the alcohol can be reacted without requiring separation of the alcohol from the glycerol and reuse of the alcohol. Such recycling can be performed multiple times in a process. Advantageously, in the last reaction step or set of steps, the alcohol-depleted glycerol can be separated from the reacted glyceride solution and fresh alcohol and/or catalyst added to drive the reaction to completion.

Thus, in particular embodiments, the biodiesel processor includes at least 2 sequentially linked processor mixer and separator pairs. The at least 2 pairs includes at least one first pair and at least one second pair, and the method includes removing a second glycerol/alcohol mixture from a separator in the first pair, adding fresh alcohol and catalyst to partially reacted glyceride solution from a first pair forming a secondary reaction mixture and processing that secondary reaction mixture through a second pair, removing the first glycerol/alcohol mixture containing un-reacted alcohol and catalyst from a separator in the second pair and mixing with un-reacted glyceride solution to form the recycling reaction mixture.

Another aspect of the invention concerns a method for operating a biodiesel processor business. The method involves a supplier providing a biodiesel processor to a third party along with a grant of rights to operate the biodiesel processor. The grant of rights to operate the biodiesel processor is in conjunction with an agreement in which the 3rd party agrees to pay a use fee to the supplier. The method may also include an agreement in which the supplier services the processor and/or agrees to purchase all or part of the production from the processor.

In certain embodiments, the processor is a transportable processor; the processor is installed within a closed container, e.g., a shipping container; the contents of the container are not accessible to the 3rd party; the processor is one described herein; the processor is a sequential processor; the processor is a scalable processor; the processor includes both scalable and sequential features.

Additional embodiments will be apparent from the Detailed Description and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically shows an exemplary biodiesel processor system that includes a processor mixer and a flow-through separation tank. Additional optional processor mixers are also shown; when included such additional processor mixers can make the system into a scalable processor.

FIG. 2 shows a longitudinal cross-section of an exemplary cylindrical design high turbulence processor mixer useful in the present systems.

FIG. 3 shows a cross-section of an exemplary radial design high turbulence processor mixer useful in the present systems, where the cross-section is taken along a plane that includes the axis of rotation of the rotor.

FIG. 4 shows a cross-section of the processor mixer shown in FIG. 3, where the cross-section is taken perpendicular to the axis of rotation of the rotor and just above the surface of the rotor, thereby creating a plan view of the rotor surface.

FIG. 5 schematically shows the processor mixer and reaction/separation portion of a processor system that uses sequential processor mixers with glycerol separation between processor mixers.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention addresses the need for efficient production of biodiesel by providing continuous flow biodiesel processors (i.e., processing systems). In many systems, biodiesel is produced using a transesterification reaction to convert glycerides, especially triglycerides, to lower alkyl esters of the constituent fatty acids and glycerol. Usually the reaction is catalyzed, usually either acid or base catalysis. Of these, basic catalysis is used more often, e.g., using NaOH or KOH. The present processors generally include a high turbulence processor mixer followed by a flow-through glycerol/biodiesel separator, such as a flow-through zonal tank separator.

Such processors can be configured in a number of different ways, including a single processor mixer linked with a single glycerol/biodiesel separator, multiple processor mixers linked in parallel with each processor mixer feeding to a common separator or to a separate separator, and multiple sequential (i.e., series-linked) processor mixers which may have glycerol/biodiesel separators operating following each processor mixer or may have a separator after several or all of the processor mixers.

A number of options for different configurations and options for additional system components are described below.

In order to more clearly explain the present invention, the following terms have the meanings as specified.

The term “alcohol” refers to a compound that consists of an alkyl group bearing a single hydroxyl group, especially a primary hydroxyl group, i.e., a primary alcohol. Examples include methanol and ethanol. Thus, in the context of a biodiesel processor, the term “alcohol separator” refers to a component or set of components that separates alcohol from other components in a particular solution or mixture. The alcohol separator may substantially purify the alcohol or may co-separate the alcohol along with one or more other species (e.g., separate the alcohol with catalyst species from glycerol or from biodiesel).

As used herein in connection with biodiesel production, the terms “alkyl esters”, “alkyl fatty acid esters”, and “fatty acid alkyl esters” refer to alkyl esters of fatty acids, e.g., lower alkyl esters (i.e., “lower alkyl fatty acid esters”) where the lower alkyl moiety has 1-6, (or in narrower embodiments 1-4, 1-3, or 1-2) carbon atoms. Examples include methyl, ethyl, propyl, isopropyl, butyl, sec-butyl, tert-butyl esters, but especially methyl or ethyl esters. Thus, the term “lower alkyl fatty acid ester solution” refers to a solution that is predominantly composed of such esters, but may contain other components, e.g., contaminants.

The term “annular” is used to refer to a ring-like shape or space.

In the context of the present zonal flow-through separation tanks, the term “baffle plate” refers to a partial, usually generally horizontal, barrier within the tank that sufficiently inhibits bulk movement of liquid below the baffle plate such that bulk mixing above the baffle plate is not substantially transmitted to liquid below the plate. More generally, in the context of such tanks, the term “baffle” refers to any structure that inhibits bulk movement of liquid in the tank such that the baffle creates volume zones having separate mixing regimes. In connection with baffle plates, a “downwardly projecting skirt” refers to a generally vertically oriented member that attaches to the generally horizontal barrier at its upper end and together with the baffle plate defines a downwardly opening cavity.

As used herein, the term “biodiesel” refers to a solution of lower alkyl esters of fatty acids. Low amounts of other components may be present, such as low levels of glycerides, free fatty acids, salts of fatty acids, glycerol, alcohol, and/or water.

The term “biodiesel processor” is used herein to refer to a combination reaction and separation system adapted for producing lower alkyl fatty acid esters from glycerides, and separating the reaction products. Additional components may also be included, e.g., pumps, biodiesel washer, glycerol distiller, and the like.

The terms “biodiesel cleaner” and “cleaner” are used herein to refer to a component or system which removes contaminants from a biodiesel solution (lower alkyl fatty acid ester solution), such as residual alcohol, soaps, catalyst, and the like. Such a cleaner may include a washer.

The term “centrifuge” is used in its conventional sense to refer to a machine for separating materials of different density, e.g., liquids that form separate phases or particles from a liquid, using high speed rotation of the fluid, especially in conjunction with rotating mechanical portions of the machine.

In the context of separators, the terms “cyclone” and “cyclonic separator” refer to a device in which cyclonic motion of a fluid produce a low force separation of components having different densities.

As used herein, unless expressly modified the terms “cylinder” and “cylindrical” refer to a right circular cylinder. The terms “cylinder axis”, “cylindrical axis” and “longitudinal cylindrical axis” refer to the central axis of the cylinder.

The terms “flow-through” and “continuous flow” mean that in normal operation, a fluid flows continuously through the referenced system or component without substantial interruption for the duration of the period of operation, such that the output rate is essentially equal to the input rate for the referenced system or component during steady-state operation.

In the context of the present systems and components thereof, the term “functionally linked” indicates that the cited components operate together in the processing of the oil, e.g., that the oil being processed progresses between the components. Unless expressly indicated, it does not require that the components are directly connected to each other (i.e., connected with no intervening component).

The term “glyceride” is used to refer to esters of glycerol (propane-1,2,3-triol) with fatty acids. Such glycerides include mono-, di-, and tri-glycerides (i.e., mono-, di-, and tri-O-acylglycerol).

The term “glyceride solution” refers to a solution that contains predominantly mono-, di-, and tri-glycerides. Usually such a solution contains at least 80, 90, 95, 96, 97, 98, 99, or 99.5% of such glycerides. Such solution may contain low levels of other components, e.g., free fatty acids, waxes, soaps. Typical glyceride solutions useful in biodiesel processing include any of a variety of vegetable oils such as canola, soybean, corn, and rapeseed oils. In the present context, “partially reacted glyceride solution” and “partially reacted reaction mixture” refer to a glyceride solution that has been reacted with other reactants in a biodiesel production reaction but may still retain significant un-reacted glycerides, e.g., at least 10% glycerides by volume, and has not been cleaned. Similarly, the term “reacted glyceride solution” refers to a glyceride solution that has been reacted with other reactants in a biodiesel production reaction, which has not been cleaned and which may, but need not, still include significant un-reacted glycerides.

The terms “glycerol/biodiesel interface” and “glycerol/reacted glyceride solution interface” refer to a bulk liquid phase interface between glycerol and an oil phase in biodiesel processor, e.g., in a separator tank.

In the context of the present biodiesel processors, the term “glycerol/biodiesel separator” refers to a device or combination of devices that substantially separates glycerol from an oil phase, especially biodiesel or a partially reacted glyceride solution. Examples of such glycerol/biodiesel separators include tanks, cyclones, and centrifuges.

In the context of oil mixing, the term “high turbulence” means a mixing regime in which small scale mixing is dominant (over bulk transport). Generally the Reynolds number for such regimes will be at or above 10,000, usually at or above 100,000 or at or above 500,000. In many cases, the turbulence will be such that the turbulence vortices are of sufficiently small scale that viscous heating is substantial, e.g., results in heating in a high turbulence biodiesel processor mixer during normal operating conditions of at least 0.1 degree C.

In the context of the present processor mixers, the term “inner body” refers to a separate three dimension object located within a chamber of an outer portion (e.g., a housing).

In the present context, the term “ionically charged solid phase material” refers to a solid phase material that carries charged moieties that remains as a solid phase when contacted with or suspended in a liquid of interest, e.g., in biodiesel and/or other oils. Thus, the term “ionically charged particulate medium” is an ionically charged solid phase material” that is in particulate form.

In the context of the present processors, the term “housing” refers to a protective cover designed to contain or support a mechanical component, and in particular to contain an inner body where the housing and inner body rotate relative to each other. Such a housing has an inner cavity, i.e., is hollow.

As used herein, the term “nanofiltration” refers to filtration in which the retention size cut-off is small molecule size, e.g., with molecular weight cut-offs from about 50 to about 1000 Daltons. This is distinguished from microfiltration, ultrafiltration, and reverse osmosis (RO).

In the present context, unless expressly indicated to the contrary, the term “oil” or “oil phase” refers to a liquid that is predominantly made up of compounds that contain long chain fatty acids, e.g., glycerides, free fatty acids, and esters of fatty acids.

In the context of the present of the present processors, the term “pipe” refers to a flow channel that has a length of at least 5 times the internal diameter (or average linear dimension normal to the flow path (cross-dimension) for channels that are not circular in cross-section). More often, the length will be at least 10, 20, 40, 60, 80, or 100 times the average cross-dimension. The cross-sectional shape may be any that allows flow of the relevant fluid (e.g., glyceride solution or biodiesel).

As used herein in the context of movement of fluid through a channel (e.g., a pipe, tank, trough, or the like), the term “plug flow” means approximately plug flow, not ideal plug flow. That is, the flow proceeds with roughly the same velocity across the cross-section of the channel, but typically has mixing across the channel. For example, the

In the context of constituents of a liquid solution or mixture, the term “polar components” refers to chemical species in the solution or mixture that are polar (i.e., have a substantial dipole moment) or charged (e.g., a sodium ion).

The term “processor mixer” is used to refer to a component of a biodiesel processor system in which a glyceride solution is mixed together with additional reactants. A “high turbulence processor mixer” or “high intensity processor mixer” is one in which the mixing occurs under conditions of high turbulence, e.g., Reynolds number at or above 10,000. Further, a “high turbulence flow-through processor mixer” is a high turbulence processor mixer which normally operates in a flow-through manner such that the fluid flow rate into the mixer is essentially equal to the fluid flow rate out of the mixer.

In connection with the present processor mixers, the term “projections” refer to convex shape that juts out from a surface, e.g., a housing surface, inner body surface, or rotor face. In relation to such projections from surfaces of processor mixers where opposing surfaces have relative velocity, the term “bypass” means that the tips of projections from one surface extend past the tips of projections from the other surface. In connection with the shapes of such projections, the terms “flat trailing surface” and “substantially flat trailing surface” means that the portion at the back of the projection relative to the rotation direction is substantially flat although it may have minor curvatures, angles, or other deviations from flatness. For example, unless expressly indicated to the contrary, deviations from flatness of less than 1, 2, 5, or 10% of the width of the surface are regarded as substantially flat. Similarly, in connection with the orientation of projections, the term “substantially perpendicular” means that the specified line is approximately perpendicular to a reference line. Unless expressly indicated to the contrary, an angle of 90±20 degrees (e.g., 90±15, 90±10, 90±5 degrees) is regarded as substantially perpendicular. Likewise, the term “tapering trailing surface” means that the portion at the back of the projection has significant extension, e.g., an angular or curved extension, such that it becomes progressively narrower toward its trailing terminus. For example, a projection may have a triangular cross-section with the base forming the leading edge and an acute angle in the trailing direction. Such extension may, for example, be at least 50, 100, 150, or 200% of the maximum width of the projection.

In relation to the present two cylinder processor mixers, the terms “relative rotation rate” and “relative velocity” refer to a rotation rate or rotational velocity defined by taking the rotation rate of one of the cylinders as zero and determining the velocity of the other cylinder using the fixed cylinder frame of reference. Thus, for example, if both cylinders were rotating at the same angular velocity, the relative rotation rate would be zero. Likewise, if each cylinder were rotating at the same rotational speed in opposite directions, the relative rotation rate would be double the rotation rate of either cylinder.

In the context of the present systems, the term “scalable” means that the system is configured such that it includes multiple processor mixers which can individually be operated or removed from operation without preventing operation of other processor mixers in the system. This allows the biodiesel output rate of the system to be varied over a wide range.

In the context of a separator tank in the present invention, the terms “secondary recycling draw tube” and “recycling draw tube” and the like refer to a tube or port in a glycerol/biodiesel zonal separation tank, where the tube is located above the glycerol/biodiesel interface and below the biodiesel draw tube (biodiesel port) such that partially reacted glyceride solution, if present, can be drawn through the tube.

As used in connection with a biodiesel production processor, the term “separator” refers to a component or set of components that substantially isolates or purifies one or more constituent species from a mixture, especially from a liquid mixture. For example, such a separator may remove one or more species from a bulk liquid or may separate a bulk liquid into two or more derivative fluids having significantly different compositions. Thus, an “evaporative separator” utilizes evaporation (i.e., phase change from liquid to vapor) of one or more constituent species as a significant element in the separation. Similarly, a “vacuum separator” or “vacuum evaporator” utilizes a vacuum, i.e., a pressure significantly lower than normal atmospheric pressure, as a significant element in the separation, e.g., to accelerate the transition of a constituent species from liquid to vapor. A “heat vaporizer” or “heated vaporizer” utilizes heat energy as a significant element in the separation, particularly to accelerate the transition from liquid to vapor of a constituent species. Also in the context of phase transition between vapor and liquid, the term “condenser” refers to a component or set of components in which the temperature of a vapor phase is reduced, such that a significant proportion of at least one species in the vapor transitions to a liquid. Also in the context of separators in a biodiesel processor, the term “pressurized spray nozzle” is used to refer to a device that includes at least one small orifice through which a liquid is directed under pressure such that a spray of small droplets is formed, e.g., an aerosol of liquid droplets.

In the context of a biodiesel processor system, the term “separator tank” refers to a tank configured such that when the tank is filled with a solution containing at least two liquids that will separate on standing, the separation will occur, and the tank includes outlets adapted for removal of at least two different fractions. A “flow-through separator tank” is one in which the separation occurs while essentially continuous flow of material into and out of the tank is maintained at essentially equal rates, i.e., steady-state.

In reference to projections in the present processor mixers, the term “set” means one or more. Usually such set is a plurality, e.g., at least 2, 5, 10, 20, or more.

In the context of the present processor mixers that include rotors, the term “vane” refers to any of several usually relatively thin, rigid, flat or curved surfaces radially mounted along an axis, as a blade in a turbine or centrifugal pump, that is turned by or used to turn a fluid. Such vanes may be attached to a disk on one or both sides, or may be located between and attached to two disks.

In a biodiesel production system, the term “washer” refers to components that together introduce water (or other polar solvent) into a biodiesel solution thereby removing water soluble (or soluble in the utilized polar solvent) components (e.g., polar (including charged) components) from the biodiesel, and may include components that removed the added water. In such a washer, a “water mixer” is a component or set of components that adds water to the biodiesel or other oil in a manner that substantial mixing of water with the oil occurs.

In the context of liquid mixtures and solutions in a biodiesel production system, the term “water soluble” indicates that the molecular or ionic species in question has substantial solubility in water at the operating temperature of the system. Such solubility is highly preferably significantly greater in water than in biodiesel, e.g., at least 2× (or at least 5×, 10×, 50×, or 100×) the solubility in biodiesel.

The terms “zonal separation tank”, “zonal flow-through separation tank”, and “flow-through zonal separation tank” are used to mean a separation tank that is designed such that during flow-through operation with solution reacted for producing biodiesel from glyceride solution, 3 distinct zones will be established within the tank: 1) mixing zone, 2) separation zone, and 3) glycerol accumulation zone. In certain embodiments, the separation zone is set off from the mixing zone by a baffle plate, such that there is a relatively stagnant zone below the baffle, and a mixed zone above the baffle. In the context of operation of such tanks, the term “mixing zone” refers to a volume of the tank in which the fluid is continuously mixed. The term “separation zone” refers to a volume of the tank in which mixing is sufficiently small that phase separation between glycerol and the oil (e.g., reacted glyceride solution or biodiesel) will occur and glycerol will migrate to a glycerol accumulation zone under the influence of gravity. The term “glycerol accumulation zone” refers to a volume of the tank in which glycerol separating from the reacted glyceride solution accumulates during phase separation and in response to gravity.

Also in the context of mixing in zonal separation tanks, the terms “stagnant” and “not substantially mixed” indicate that bulk liquid movement within the particular region of the tank is sufficiently low that such movement allows significant separation of glycerol from biodiesel where the glycerol fraction is at least 0.1 g/cm3 denser than the biodiesel fraction.

A. Reagent Supply

The present systems and methods generally utilize conventional chemistries for production of lower alkyl fatty acid ester biodiesels from glyceride solution feedstocks. In most cases, the reaction utilizes a lower primary alcohol, e.g., methanol or ethanol, with a basic catalyst, e.g., NaOH or KOH, or a direct solution of a lower alkoxide in a lower alcohol, e.g., sodium methoxide in methanol (i.e., methanolic sodium methoxide). Other variations on the reaction chemistry can be used, e.g., variations as described in the art, such as acid catalyzed reactions, processes that combine acid catalyzed and base catalyzed reactions, the use of other catalysts, and high pressure reactions (catalyzed or non-catalyzed).

The glyceride solution can come from any of a variety of sources. In many cases, the source is a vegetable oil, e.g., from oil seed (for example, soybean, corn, linseed, peanut, sunflower, castor bean, or canola oil) or palm or coconut oil. Animal fats and/or waste oils can also be used. Certain sources may need early stage treatment to reduce contaminants and/or to reduce the content of free fatty acids.

Thus, the present systems and methods utilize liquid reaction mixtures that generally include a glyceride solution feedstock that is combined with a lower alkyl group donor species (e.g., a lower primarily alcohol such as methanol or ethanol) and usually a catalyst (e.g., NaOH, KOH, sodium methoxide, or potassium methoxide for base catalysis). The feedstock can be pumped or transported by gravity or other force from a reservoir into a processor mixer. The other reagents can be mixed into the glyceride solution in a variety of ways, e.g., using an in-line mixer, using a rapidly stirred mixing tank, using injection into a processor mixer.

In most cases, the glyceride solution, or the reaction mixture will be heated prior to entry into a processor mixer, e.g., to about 60-65 degrees C. Such heating can be accomplished using various heating methods, for example, directly using a heater, e.g., an in-line heater, or using a heat exchanger, e.g., using heat recovered from a heat vaporization process.

Heated glyceride solution or reaction mixture is directed to a processor mixer, e.g., a high turbulence processor mixer as described below.

B. High Turbulence Processor Mixers

In the present systems, a processor mixer is a device in which the reaction mixture is intimately mixed, preferably vigorously (which can generate an emulsion). The present systems can incorporate any of a variety of different processor mixers. In such mixers the esterification reaction is initiated, and in some cases proceeds substantially during passage through the processor mixer. A variety of mixers described in other publications can be used. In addition, advantageously high turbulence processor mixers as described herein can be used in the present systems and methods.

In order to maximize the reaction, it is desirable to dramatically increase the surface area of the phase interface between the non-polar glyceride phase and the polar methanol phase. In advantageous embodiments of the present invention, this is accomplished through very intense physical mixing. To ensure that highly effective mixing has occurred, the mixing can be taken to a level such that appreciable viscous heating occurs during passage of the reaction mixture through the processor mixer, e.g., at least a 0.1 or 0.5 degree Celsius rise in temperature during passage through the mixer (or even a greater temperature rise, for example, at least 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 10.0 Celsius or greater temperature rise). Such intense mixing contributes additional heat energy to the system which can increase the reaction rate, and may also create local high pressure areas in which the reaction rate can be locally increased. While such high intensity, high turbulence mixing is advantageous, excessive mixing can be wasteful of mixing energy.

Two exemplary types of high intensity processor mixers are described herein, but variants and other designs can also be used. One design type utilizes an outer housing with an inner body, with a fluid space between the two. The housing and/or the inner body is rotated such that there is relative rotation between the housing and the inner body. The bulk fluid flow-through the processor mixer occurs through the fluid space generally parallel to the axis of rotation of the housing and/or the inner body. For example, the housing can have an inner surface in the shape of a cylinder, the inner body is a smaller cylinder such that there is a space (e.g., an annular space) between the cylinders, and the two cylinders have parallel longitudinal axes (e.g., a common longitudinal) cylinder axis. The longitudinal axes (e.g., common cylinder axis) are also the rotation axes. The overall direction of bulk flow of the reaction mixture is parallel to the axis of rotation. That is, the glyceride solution flows into one end of the space between the cylinders and exits from the other end, e.g., through apertures in the housing leading to suitable tubes or pipes. The inner and outer cylinders include projections that project into that annular space and may bypass. The relative rotation rate is typically sufficiently high that the speed of the projections passing through the reaction mixture creates highly turbulent conditions in the reaction mixture.

While most such processor mixers are selected to have cylindrical shapes, other shapes can also be used. In such cases, the inner and outer surface projections should pass sufficiently closely to each other that high turbulence conditions are created in the reaction mixture. One such variant would use an outer cylinder, with a polygonal inner body, e.g., a square, pentagonal, or hexagonal body. The inner body can have small projections and/or the polygon corners may provide the projections.

A second type of exemplary design is a processor mixer design that is a centrifugal (or radial) design analogous to a conventional centrifugal pump for liquids. Similar to such pumps, such a mixer includes a housing that has a circular chamber within it (often a flattened circular chamber). Within that circular chamber is located a disk-shaped rotor that includes vanes (or other shape projections) on at least one surface. Opposing projections are located on the facing housing surface. In operation, the fluid enters the housing cavity centrally, typically along the rotational axis of the rotor, and exits the pump through an opening(s) in the periphery of the housing. In most cases, the exit opening is essentially tangential to the periphery. The projections on the rotor and the projections on the housing are located and distributed such that motion imparted to the liquid by the rotor is countered by the projections on the housing.

In some designs, the rotor includes vanes on one surface of the rotor, and the vanes have a concentric series of circular grooves, which may be partial or cut fully to the rotor backing disk. The projections on the facing surface of the housing are distributed in rings such that they can project into the rotor vane grooves. In operation the fluid enters the cavity through the housing centrally to the rotor. The rotating rotor causes the fluid to be accelerated forward and outward. That motion is then interrupted by the first ring of housing projections, significantly slowing outward migration of the fluid and causing intense mixing. As the fluid passes the first ring of housing projections, the next section of vane again accelerates the fluid until it encounters the next ring of housing projections. The process is repeated until the fluid passes the last ring of projections, and passes out through the peripheral opening. An additional groove and corresponding projections can be present in the distal tips of the vanes and the inner peripheral surface of the housing respectively. Processor mixers of this type can be designed to function as combination processor mixer/pump.

In one alternative, the mixer may have counter-rotating rotors with opposing projections on each rotor. The projections can constitute bypassing rings of projections, closely fitting vanes, or other configurations. The projections can be distributed such that they do not impart a net outward fluid flow. In such designs, the fluid is moved through the processor mixer using an external pressure (e.g., from a separate pump). Alternatively, the sets of projections can be sized, shaped, and distributed such that the net fluid motion is outward. In certain embodiments of this design, the projections can be designed and configured such that the net velocity of the fluid causes the processor mixer to also function as a pump.

Such intense mixing, e.g., using the present processor mixers, can create an emulsion, which may be an unstable emulsion. In this context, an “emulsion” is a suspension of small globules of one liquid in a second liquid with which the first does not substantially mix, e.g., the polar lower alkoxy components intimately mixed into the glyceride solution.

The processor mixer size and mixture flow rate can be balanced to establish a desired residence time for the fluid in the mixing zone of the mixer, e.g., a residence time of 1-5, 2-10, 5-20, 10-30, 20-40, 30-60, 60-120 seconds.

Highly intense mixing may also be accomplished or facilitated using ultrasound agitation and/or passage of the glyceride/base/alcohol mixture through a small orifice under pressure (preferably a series of such passages).

C. Biodiesel Separators, Including Flow-Through Separator Tanks

In biodiesel processors that utilize a processor mixer, the system also generally includes a glycerol/biodiesel separator for separating the reaction products, glycerol and biodiesel (lower alkyl fatty acid esters). In most cases, such separators utilize a separation tank, cyclone, and/or centrifuge. Separator tanks are commonly used in biodiesel processor systems to provide additional reaction time and to separate the glycerol from the product esters and unreacted glycerides. In some cases, the solutions in such tanks are subjected to initial low to moderate mixing, followed by a period of very little or no mixing during which glycerol settles to the bottom leaving biodiesel as the upper phase. Such separation typically requires several hours to several days depending on the tank size and the degree of separation desired. However, such long separation times are undesirable because of the limitations on processing capacity (or alternatively the need for many large tanks), as well as the potential for reversal of the reaction.

Thus, the present processors include efficient and rapid flow-through separators to separate glycerol from biodiesel (or partially processed glyceride solution). Certain of the present systems include separator tanks that efficiently separate the glycerol reaction product from the biodiesel product and unreacted oil. In the present system, preferably a glycerol/biodiesel separator tank is used that is configured such that there are distinct zones. In the mixing (usually upper) zone, significant mixing of the solution occurs, in an intermediate separation zone there is little mixing such that separation can proceed, and in the bottom zone the glycerol collects. In preferred systems, as glycerol collects, it is automatically drawn or drained off. Such draining of the glycerol can be controlled to prevent removal of biodiesel solution, e.g., by triggering the removal using a medium buoyancy float valve that floats in glycerol but not in oil.

The different zones can be controlled by internal tank structures. For example, the upper mixing zone can be created by the flow pressure and direction of the incoming reaction mixture; the middle separation zone can be delimited by a baffle at the bottom of the mixing zone and top of the separation zone; and the bottom glycerol accumulation zone includes a tapered or otherwise reduced cross-section portion facilitating glycerol removal, and which also can reduce the bulk interface between the glycerol layer and the oil layer.

As indicated, in such tanks, the bottom section can advantageously be a reduced cross-sectional area portion, e.g., an inverted cone, hemisphere, arcuate section, a reduced cross-section cylinder or other cross-sectional shape with cross-sectional area reduced from the main portion of the tank.

Such tank will incorporate an inlet for reacted glyceride solution (usually in the upper portion of the tank), a biodiesel draw tube (biodiesel port) (typically located in the separation zone), and a glycerol draw tube (glycerol port) in the glycerol accumulation zone (typically near the bottom). Additional ports or tubes may also be incorporated in a particular design. For example, a recycling draw tube may be included, which may be located to satisfy the requirements of the particular system. Examples of locations for recycling draw tubes includes within the mixing zone, and in the separation zone (e.g., close to but above the glycerol/biodiesel interface or high in the separation zone but below the biodiesel draw tube). The recycling draw tube is used to supply a partial volume for reprocessing through a processor mixer. Such reprocessing can be used to increase the extent of conversion of glycerides to biodiesel.

The glycerol draw tube is advantageously located in association with a biodiesel separator structure. Such a biodiesel separator structure can be advantageously constructed such that counter-current migration of biodiesel is involved in movement of biodiesel to the glycerol draw tube. Such counter-current migration can be accomplished by using a surface that defines a downwardly opening cavity. The surface can be of various shapes, e.g., downward opening cylinder, cone, hemisphere or other surface of revolution. The biodiesel draw tube is preferably located within the cavity defined by that surface, preferably at or near the top of that cavity.

The baffle may also be constructed in various ways and may be integrated with the biodiesel separator structure. The baffle inhibits mixing currents from substantially extending from the mixing zone to the separation zone, while permitting migration of reacted glyceride solution into the separation zone. For example, the baffle may be a plate that blocks a substantial portion of the cross-section of the tank (e.g., a centrally located plate), a perforated plate covering the full cross-section of the tank, or a set of vertical plate sections creating a set of vertically oriented passages. The biodiesel separator structure can be integrated with the baffle, e.g., a peripheral skirt or smaller vertically oriented wall sections can be mounted on the lower surface of a baffle plate thereby defining a downwardly opening cavity. Similarly, a peripheral plate can have a downwardly projecting skirt, again defining a downwardly opening cavity. Alternatively the biodiesel separator may be a separate structure located below the baffle. A variety of other such structures (alone or in combination) can also be utilized for the baffle and biodiesel separator structure.

A baffled tank can also be advantageously used in a batch operation. When a baffled tank is used in a batch operation, mixing throughout the tank is maintained by drawing from the glycerol and/or biodiesel ports and recirculating that fluid draw. As soon as the reaction has gone to completion, glycerol-free biodiesel can be drawn from the biodiesel port (the draw tube under the baffle) immediately after bringing the reaction to completion. This is because the biodiesel must travel slowly upward to the draw tube, leaving behind the glycerol. As a result, it is not necessary to allow the whole tank to settle before beginning to draw off biodiesel, thereby saving time. Using a baffled tank in batch mode, the entire operation can be done using minimal electronics (ingredients can be manually measured and added to the batch), and no centrifuges (water wash would remove any residual glycerol). Thus, the invention also concerns the process or method of biodiesel production using such a tank in batch mode.

In other cases, the zonal separation tank utilizes multiple tanks. The reacted glyceride solution enters a mixing tank that typically provides low to moderate mixing, e.g., sufficient to prevent, or at least substantially slow, phase separation. After an interval of mixing, the reacted glyceride solution moves to a second tank in which the liquid is sufficiently still so that mixing currents do not substantially affect the glycerol/biodiesel separation rate. Such a tank may incorporate a baffle(s) (e.g., to quickly still currents associated with inlet flow) and/or biodiesel separator structures (e.g., as described above for baffled tanks).

In yet other cases, a non-baffled tank is utilized that functions as a zonal separation tank. Such tanks are relatively tall and thin such that mixing in the upper section (the mixing zone) is dampened by viscous friction before reaching the lower portions of the tank. As a result, a portion of the tank functions as a separation zone, and the bottom of the tank is the glycerol accumulation zone. Such tanks may advantageously incorporate a biodiesel separator structure (e.g., as described above for zonal separation tanks that include a baffle).

As an alternative, or in conjunction with separator tanks and/or centrifuges, cyclones may be used to provide a substantial separation of glycerol from biodiesel. Thus, for example, a cyclone(s) may be used to provide rapid initial separation removing most of the glycerol, with more complete separation provided using a separation tank or centrifuge. Such rapid removal assists in preventing back reaction.

In other systems, one or more centrifuges can be used to rapidly separate glycerol and biodiesel. Such centrifuges may be incorporated in a system in various ways. For example, centrifuges may provide full separation function, or may be combined with separation tanks and/or cyclones. Thus, a tank may be used to provide initial separation, with a centrifuge(s) used to rapidly complete the separation. Alternatively, a cyclone(s) may provide the initial separation, with the centrifuge(s) completing the separation.

D. Biodiesel Cleaner

A biodiesel production system will typically contain a system for cleaning the biodiesel phase, e.g., to remove residual glycerol, alcohol, and catalyst, following passage through a glycerol/biodiesel separator. Such cleaning can be accomplished using various methods and apparatus such as the following.

1. Phase Separation

A partial cleaning can be accomplished using a phase separation method. For example, the crude biodiesel solution can be allowed to separate for a substantial period of time in a tank and/or can be centrifuged. Such techniques can remove a large fraction of the residual glycerol and methanol, but some of those materials will typically remain in solution in the biodiesel phase. Therefore, for further cleaning it can be beneficial to use one or more other methods as alternatives or supplements.

2. Water Wash

A large proportion of polar contaminants can be removed using a water wash. This is followed by removal of the water, e.g., through a combination of phase separation to remove most of the water (e.g., in a tank, cyclone, and/or centrifuge) usually followed by evaporation (e.g., as described below) to remove the remainder. Such water wash and water removal can be accomplished using methods conventional in biodiesel processing. In some cases, it is desirable to use slightly acidified water for the wash process.

In order to increase the fraction of water removed, it can be beneficial to use multiple centrifuges in series; in such series it may be desired to have the final centrifugation be a high intensity centrifugation, e.g., about 1000×g or greater.

3. Solid Phase Adsorption

Residual contaminants can be removed using solid phase media that adsorb the contaminants to be removed. Such a solid phase media can be mixed in the solution and then settled and/or filtered out, or can be immobilized (e.g., in a column). A material used for such purposes is magnesium silicate, e.g., sold in a powdered form as MAGNASOL® (Ciba Corporation). The adsorbent can then be filtered out of the biodiesel, e.g., filtered at least through a 5 micron filter, or preferably with final filtering through a 1 micron filter. Such solid phase adsorption can be used as the sole cleaning method, as the primary cleaning method with a supplementary second method, or as a supplement to washing.

4. Evaporative Methods

Other methods to remove contaminants include methods utilizing evaporation of at least the more volatile components, e.g., alcohol and/or water. Such evaporative methods can involve conventional techniques, e.g., vacuum evaporative method, with or without generation of aerosol and with or without use of heat. Likewise, the evaporative method may utilize heat, e.g., above the boiling point of the volatile components to be removed. Heating of the solution can be combined with aerosol generation and/or with vacuum.

In a biodiesel production process, such evaporative methods can be used to remove alcohol and/or water from biodiesel or from glycerol. Such removal is advantageous, for example, to clean the respective solution.

In many cases, following vaporization, it is desirable to recondense the vaporized components, e.g., for alcohol recovery. This can be done in step fashion to provide one-step purification. Indeed, while the energy input is large, full distillation can be used, thereby providing simultaneous purification of all components in the solution.

E. Alcohol Extraction and Recovery

In certain systems, it is advantageous to remove and/or recover unreacted alcohol from the crude biodiesel solution and/or the glycerol product. Such alcohol can be obtained essentially purified, or can be co-recovered with catalyst. In the separation of biodiesel from glycerol, generally a large amount of the alcohol and most of the charged components will be carried in the glycerol phase. These species can be substantially removed from the glycerol, for example, using heat and/or vacuum evaporation followed by condensation or using nanofiltration or a combination of those methods.

Evaporative methods using heat for vaporization can be full distillation methods in which all components of the solution are vaporized, and the liquid components re-condensed, or only the more volatile components (e.g., water and alcohol) can be vaporized and re-condensed.

Beneficially, when using heat vaporization, a substantial amount of the heat can be recaptured using heat exchangers. Such heat exchangers can, for example, recover some of the initially generated heat that was not captured in heating the solution and/or to capture heat in conjunction with re-condensation of vaporized liquids. The recaptured heat can be used in heating steps earlier in the biodiesel production process, e.g., to heat the incoming glyceride solution feedstock.

In most cases, when using vacuum evaporation, only the volatile components are evaporated, leaving the glycerol.

In either heat or vacuum evaporative methods, the process can be accelerated by increasing the surface area, e.g., by spraying through an orifice (e.g., a nozzle) to create small droplets (e.g., an aerosol) so that the surface area for evaporation is greatly increased.

As an alternative or as a method used in conjunction with vaporization methods, nanofiltration (NF) can be used to separate solution components based on molecular size (although charge can also participate). In such filtration a final membrane is selected that has a molecular weight cut-off (MWCO) such that a significant percentage of the glycerol is retained and smaller species such as methanol (and preferably small ions) will pass through. (MWCO is commonly defined as the MW at which 90% of a reference species is rejected, i.e., retained.) For example, a membrane with an MWCO of about 50 will retain a large fraction of the glycerol and pass a large fraction of the methanol. Depending on the characteristics of the membrane, the Na, K, and/or OH ions may either pass or be retained. Membranes with slightly larger MWCOs can also be used. For example, a membrane with a MWCO of about 100 will retain a significant fraction of the glycerol; the percentage retained can be increased by multiple passes through such membranes, with each pass resulting in a partial retention (e.g., retention of at least 30, 40, 50, 60, or 70%) and the number of membrane passes selected to result in the desired total separation level. The retentates from the multiple membrane passages can, if desired, be pooled. The methanol, or methanol and catalyst ion solution, can then be reused in the biodiesel process.

In certain system variants, the catalyst is re-used without full purification by evaporating a portion of the glycerol following separation from biodiesel. The glycerol fraction contains catalyst that partitioned into the glycerol phase. Evaporation of the glycerol will also evaporate the alcohol (if not previously evaporated) leaving a solution that is concentrated in catalyst. That concentrate can be diluted with suitable alcohol and re-used in the reaction, where the relatively small amount of glycerol does not prevent reaction of glyceride solution to biodiesel.

F. Exemplary System and Operation

The present systems can be configured in various ways depending on the particular application and the selection of components. Exemplary configurations are described below.

1. Exemplary Systems Having a Processor Mixer and Flow-Through Separation Tank

Certain examples of the present systems include a single processor mixer, a flow-through separation tank, and other accessory components for completing the system. In general, such systems include a high turbulence processor mixer and/or zonal flow-through separation tank as described herein.

A simple but effective exemplary system can include basic components as illustrated in FIG. 1. In operation, alcohol (e.g., methanol) and a 30% sodium methyoxide solution are metered together in the proper proportion from respective sources 20 and 10, then this solution is metered into the flow of raw vegetable oil (e.g., canola oil) from oil source 30. These are mixed using an in-line mixer (not shown in FIG. 1) and passed through a heater 40 to bring the mixture temperature to at least 48.9 degrees C. (120 degrees F.).

This heated mixture then passes through a specially designed processor mixer 50 that emulsifies the alcohol/oil mixture to maximize phase-to-phase contact and thus increase the reaction rate. (Additional processors 70 and 72 are optional. When present they are configured as a scalable system.)

The resulting emulsion then passes through a high-volume recirculation pump 80, through the injection inlet 160 and into the zonal flow-through separator tank 100, which has top 102, cylindrical sides 104, and inverted cone bottom 106. Instead of a single pass, fluid can be recycled for more complete reaction. Such recycling fluid can be drawn from the recirculation intake port 170 near the bottom of the recirculation zone (area 110 on the flow chart), or from the top of the separation zone (area 120 on the flow chart) through the biodiesel port 180. Throttling valves control the source and flow rate of liquid drawn through the recirculation pump.

The emulsified mixture, together with any recirculated liquid is forcefully injected into the center of the top of the tank to effect a mixing and circulating action, thus maintaining a relatively homogenous mixture in zone 110 by preventing alcohol from separating out of the emulsion and floating to the top where it can no longer react with the oil.

Separation zone 120 is a relatively still area created by the baffle plate 130 and attached skirt 140 that allows time for the glycerol that has been released from the oil during the trans-esterification reaction to settle to the glycerol accumulation zone 150 in the bottom of the cone 160 and leave the circulation loop. This is beneficial because the glycerol can back-react with the fatty acid methyl esters (biodiesel, the desired end product) and revert back to glycerides (e.g., vegetable oil), the starting material. Continuously removing the glycerol from the recirculation loop where the reaction is taking place therefore increases the effective reaction rate and extent of reaction by reducing the rate of the reverse reaction. Furthermore, separation of the glycerol allows recovery of alcohol and/or catalyst from the glycerol, such that those components can be re-introduced into the processor at an earlier stage.

The alcohol can be removed following separation of the glycerol, or can be removed (at least partially) prior to the glycerol/biodiesel separation. Removing at least part of the alcohol before such separation increased the density difference between the glycerol phase and the biodiesel phase, which results in a cleaner separation.

Glycerol accumulation zone 150 is a cone shaped area where the glycerol settles while awaiting draining. Glycerol removal is controlled by a float switch activating a solenoid valve (not shown) on the bottom drain 190. The glycerol drained from the bottom of zone 150 flows into the pipe 192 connecting with the vacuum tank 200 for removing methanol from glycerol. The vacuum tank is located such that the head pressure generated by the tall reaction tank is sufficient to push the glycerol through the pipe.

The centrifuge 210 is used to separate any remaining glycerol from the ester solution, i.e., the biodiesel. It separates the biodiesel and residual glycerol into two streams that go to their respective vacuum tanks (200 and 202 respectively) to boil out any residual methanol. The biodiesel and glycerol can be separated from each other before removing the excess methanol in order to prevent the reaction equilibrium from shifting back to the left, or can be removed before such separation (e.g., to assist in creating a good separation of glycerol from the biodiesel).

The methanol (or other alcohol) vapor that is vacuum boiled from both the biodiesel and the glycerol passes through the pump 250 that assisted in it recovery from the vacuum tanks and further passed through a heat exchanger 240 to lower it's temperature to prevent excess evaporation from the storage tank 224.

The biodiesel is pumped by a gear pump (not shown) out of the vacuum tank 200 to the water wash system 230. This system adds water to the biodiesel, agitates them together, and then passes the liquid through a centrifuge to remove the water and water-soluble contaminants. For simplicity the centrifuge following the water wash system is not shown in FIG. 1. After washing, the biodiesel is pumped into a storage tank 220.

The glycerol is pumped directly to storage tank 222 to await further purification, processing, or transport, while the methanol is stored in tank 224 or returned to source tank 20 for reuse.

Two exemplary processor mixer designs that can be utilized in biodiesel processes as illustrated in FIG. 1 (and FIG. 5) are shown in FIGS. 2-4.

FIG. 2 shows a longitudinal cross-section of an exemplary cylindrical design high turbulence processor mixer. Process mixer 500 includes a fixed outer housing 510 with a generally cylindrical cavity and a rotating cylindrical inner body 530. The housing has projections 520 extending toward the inner body, and the inner body has projections 540 extending toward the outer housing. Rotation of the inner body is driven by an external power source via shaft 550, while the opposite end of the inner body is supported by stub shaft 580. During use, fluid is pumped into the processor mixer via inlet tube 560, progresses through the gap between the outer housing and the inner body while being mixed under high turbulence conditions by the action of the sets of projections under rotation of the inner body, and exits through outlet tube 570.

FIG. 3 shows a cross-section of an exemplary radial design high turbulence processor mixer 400 useful in the present systems, where the cross-section is taken along a plane that includes the axis of rotation of the rotor as well as the axial fluid inlet pipe. The processor mixer includes outer housing 410 and inner rotor 420. The rotor is driven from an external power unit via rotor shaft 440. The rotor includes disk 424 and vane projections 422, and the housing includes projections 412. The housing projections and rotor projections are arranged in concentric rings that alternate radially. On the opposite side of the housing from the rotor shaft is fluid inlet pipe 430, with interior channel 432.

FIG. 4 shows a cross-section of the processor mixer shown in FIG. 3, where the cross-section is taken perpendicular to the axis of rotation of the rotor and just above the surface of the rotor, thereby creating a plan view of the rotor surface. In this figure, the dashed circular lines illustrate the paths the housing projections 412 shown in FIG. 3 would describe as the rotor rotates. The rotor projections 422 project from the rotor disk and bypass the housing projections. At the housing periphery is the outlet pipe 450 with interior channel 452 through which the fluid will pass as it exits the processor mixer.

2. Exemplary Scalable Systems Having Parallel Linked Processor Mixers with a Flow-Through Separation Tank

In other exemplary systems, advantageous scalable systems can be constructed in which a plurality of processor mixers are configured such that individual processor mixers can be brought into operation to increase output, or conversely removed from operation to reduce output or to allow for servicing without shutting down the entire system.

Systems of this general type can use a single separator (e.g., flow-through separation tank and/or centrifuge) in common, or may use a plurality of separators, each functionally linked with one or more of the processor mixers.

A schematic example of such a system is shown in FIG. 1 as described above, except that optional processor mixers 70 and 72 are present. The system includes three processor mixers 50, 70, and 72 connected to zonal flow-through separator tank 100. In this system, any of the processor mixers can be shut down while continuing operation of the remainder of the system. If the processor mixers are of equal capacity, this can also be used to cut the production to ⅔ or ⅓ of full capacity (or conversely to double or triple the production rate of a single processor). Of course, using processor mixers of unequal capacities or using larger number of paralleled processor mixers allows other fractional production rates.

3. Exemplary System with Sequential Processor Mixers

Additional exemplary systems incorporate a plurality of sequentially linked processor mixers with a residence chamber following each processor mixer. Each set of processor mixer and residence chamber is termed a processor unit. The system will include at least one separator, such as a separation tank (e.g., a present zonal flow-through separation tank and/or a centrifuge). In operation, each processor mixer imparts high energy turbulent mixing, while the associated residence chamber provides an interval during which reagents in the well-mixed glyceride solution react to form lower alkyl fatty acid esters and glycerol. As regents at the interfaces are depleted and/or products accumulate and/or phases begin to separate, the solution is extensively mixed again in the next processor mixer thereby providing fresh reagent for reaction. By processing in this manner, the total mixing energy can be reduced while retaining a desired rate and extent of reaction without recycling of partially reacted glyceride solution. In such a processor, the alcohol and catalyst reagents can be mixed using a single addition before the first processor mixer, or can be added in increments to maintain an evener concentration of those reagents. That is, alcohol will be consumed in passage through each processor unit, reaction depleting its concentration. The depleted alcohol can be replaced in additions increments bringing the alcohol concentration back to the original or other desired concentration.

Such systems can also include a glycerol/biodiesel separator following each processor mixer (or following a series of processor units), either integrated with or separate from the residence unit. The inclusion of a separator assists in driving the reaction toward biodiesel and glycerol products by inhibiting the reverse reaction. However, such removal also removes alcohol and catalyst that are in solution in the glycerol. Such loss can be compensated by adding excess reagents at the beginning, or preferably by injecting additional reagent during the sequential process, e.g., before the solution enters each processor mixer or directly into the processor mixers.

A residence chamber is sized such that the design flow rate will result in a desired residence time for the glyceride solution in the residence chamber. Such residence time allows the reaction to proceed to a selected extent. After passage through a residence chamber (or simultaneous with such passage) glycerol can be separated from the reacted glyceride solution (or biodiesel), or the mixture can be passed without separation to the next processor unit. Advantageously, removing glycerol assists in driving the reaction to completion.

Addition of alcohol and catalyst can be performed in a single step or incrementally. For example, sufficient alcohol and catalyst can be added to allow effective reaction during passage through the first processor unit. If glycerol is not removed, the catalyst will remain, but an incremental addition of alcohol can be performed to restore the alcohol concentration to a desired level. This process can be repeated until the final processor unit, at which time the glycerol phase is removed, and the biodiesel is passed on for cleaning. Alternatively, if glycerol is removed following passage through the first and/or an intermediate processor unit, that glycerol removal also removes unreacted alcohol and catalyst. Those reactants can be replaced along with replacement of reacted alcohol allowing effective reaction in the subsequent processor unit.

Advantageously, a residence chamber in such configurations is essentially a pipe. Use of pipes allows for compact construction and are also amenable to relatively high pressure operation. For example, while other configurations can be made transportable, high throughput systems in which pipes are used as residence chambers are particularly adaptable to transportable designs (e.g., constructed such that the maximum dimensions and total space occupied by the system are consistent with transport, such as transport by truck or train. For example, systems can be fitted within standard 20 (approximately 34 m3) or 40 foot shipping containers approximately 68 m3), e.g., with all processor units located within one such shipping container. Additional system components, e.g., biodiesel cleaner and/or methanol extractor(s) can be placed in the same or additional shipping container or other space. Typically in transportable processors, the reagent supply, and/or biodiesel and/or glycerol storage are external to the transportable containers, or other transportable structures that hold the active processing components. Transportable processors can even be constructed in more compact configurations, e.g., occupying no more than 5, 10, 15, 20, 25, or 30 m3.

In addition, another major benefit of having the processing units and residence chambers in a container(s) is that the system can be well insulated to conserve energy. Such insulation can be used to conserve energy, even if individual components are left uninsulated, e.g., to increase ease of inspection, maintenance, or repair. Thus, certain of the present processors have uninsulated processor mixers and residence chambers installed within an insulated container(s).

A further advantageous selection is to utilize combination pump/processor mixers (e.g., as described herein). Such selection simplifies the system by reducing the number of different dynamic components.

A schematic example showing a series of processor units in such a sequential arrangement is shown in FIG. 5, illustrating sequential processor 300. In this example, there is a series of three processor units 310, 312, and 314. Each processor mixer is followed by a residence chamber in the form of pipe sections 330, 332, and 334, which have internal baffling to maintain mixing. Following each residence unit is a centrifuge (items 320, 322, and 324) to separate glycerol from biodiesel. Replacement alcohol and catalyst is injected via injection lines 360 and 362 just before the second and third processor mixers. The glycerol separated in each centrifuge is combined in pipe 340 and directed to an evaporative separator 352 in which alcohol is removed from the glycerol and combined with residual alcohol removed from the biodiesel stream in evaporative separator 350 and is re-condensed, passed through pump 372, and passed through heat exchanger 374. The glycerol can be stored in tank 382 or can be cleaned, e.g., by distillation.

Following the final processor unit 314 and residence chamber 334, the biodiesel fraction from the final centrifuge 324 is processed using evaporative separator 350 to remove residual alcohol, passed through centrifuge 326 to separate residual glycerol and associated components, then washed using washer 370. (The glycerol phase removed in centrifuge 326 can alternatively be directed to pipe 340 where it is combined with earlier separated glycerol and passed through evaporative separator 352 to remove any residual alcohol.) The bulk of the wash water is removed using a centrifuge 328. Residual water can be removed using an additional evaporative separator (not shown). The cleaned biodiesel is then directed to storage tank 380.

4. Phase Inversion Separation System

In general, biodiesel systems include separation steps in which phase separation between biodiesel and glycerol is performed. In described systems using basic catalysis, the process typically involves adding 10-30% v/v of methanol or other lower alcohol. The glycerol produced, together with the majority of the excess methanol forms a denser, lower phase, with an upper biodiesel phase.

Alternatively, it is possible to cause a phase inversion in which the glycerol-containing phase is less dense than the oil phase and therefore rises to the top. This can be accomplished by adding a larger excess of the alcohol (at least for methanol and ethanol). Methanol and ethanol are somewhat less dense than most biodiesel (and glyceride solutions). In these cases, a large excess of the alcohol will cause the combined alcohol/glycerol phase to be less dense than the biodiesel so that it forms an upper layer. This procedure can be advantageous because the excess of alcohol reactant helps drive the transesterification to the right (to biodiesel and glycerol products).

However, in order to be economic, recovery of the alcohol is desirable (e.g., for re-use in the biodiesel process). Advantageously, the large amount of un-reacted alcohol is separated from the glycerol and returned for reuse in the process. Such recovery can be accomplished such that the alcohol is substantially purified, e.g., by evaporation and condensation. In this case, the alcohol along with fresh catalyst is added at the beginning or earlier stage of the process. Alternatively, the alcohol can be co-recovered with catalyst, e.g., by use of nanofiltration. In this case, the recovered alcohol/catalyst solution can be used directly, or additional alcohol can be mixed into the solution to create a desired alcohol ratio.

All patents and other references cited in the specification are indicative of the level of skill of those skilled in the art to which the invention pertains, and are incorporated by reference in their entireties, including any tables and figures, to the same extent as if each reference had been incorporated by reference in its entirety individually.

One skilled in the art would readily appreciate that the present invention is well adapted to obtain the ends and advantages mentioned, as well as those inherent therein. The methods, variances, and compositions described herein as presently representative of preferred embodiments are exemplary and are not intended as limitations on the scope of the invention. Changes therein and other uses will occur to those skilled in the art, which are encompassed within the spirit of the invention, are defined by the scope of the claims.

It will be readily apparent to one skilled in the art that varying substitutions and modifications may be made to the invention disclosed herein without departing from the scope and spirit of the invention. For example, variations can be made to the design of a processor mixer and/or the method of separating glycerol from biodiesel. Thus, such additional embodiments are within the scope of the present invention and the following claims.

The invention illustratively described herein suitably may be practiced in the absence of any element or elements, limitation or limitations which is not specifically disclosed herein. Thus, for example, in each instance herein any of the terms “comprising”, “consisting essentially of” and “consisting of” may be replaced with either of the other two terms. The terms and expressions which have been employed are used as terms of description and not of limitation, and there is no intention that in the use of such terms and expressions of excluding any equivalents of the features shown and described or portions thereof, but it is recognized that various modifications are possible within the scope of the invention claimed. Thus, it should be understood that although the present invention has been specifically disclosed by preferred embodiments and optional features, modification and variation of the concepts herein disclosed may be resorted to by those skilled in the art, and that such modifications and variations are considered to be within the scope of this invention as defined by the appended claims.

In addition, where features or aspects of the invention are described in terms of Markush groups or other grouping of alternatives, those skilled in the art will recognize that the invention is also thereby described in terms of any individual member or subgroup of members of the Markush group or other group.

Also, unless indicated to the contrary, where various numerical values are provided for embodiments, additional embodiments are described by taking any 2 different values as the endpoints of a range. Such ranges are also within the scope of the described invention.

Thus, additional embodiments are within the scope of the invention and within the following claims.