Title:
PROTECTIVE GAS GENERATING HEATING SYSTEM FOR ASPHALT TANKS
United States Patent 3841303
Abstract:
A protective gas generating heating system for asphalt tanks comprising an oil or gas fired heating tube in a closed, asphalt tank, the heating tube generating predominately carbon dioxide and water vapor as an exhaust gas, an exhaust stack connected at one end to the heating tube and at the opposite end to the inlet of a condensing and cooling coil, a compressor connected at its lower pressure inlet to the outlet of the cooling and condensing coil and at its higher pressure outlet to an accumulator tank, a conduit connecting the accumulator tank to the top of the asphalt tank, and a pressure regulator in the conduit adapted to maintain a predetermined, minimum positive pressure in the asphalt tank.
US Patent References:
Method and apparatus for producing neutral atmosphere in heat treating furnaces
Comstock - July 1938 - 2124764
Circulation of heat treatment atmospheres
Hayes - March 1942 - 2275106
Apparatus for storing and distributing heated asphalt mix
Plumb - February 1967 - 3305138
Hot mix storage bin
Brock - October 1967 - 3348739
ASPHALT MELTING KETTLE
Wollner - March 1970 - 3503382
Method and apparatus for producing neutral atmosphere in heat treating furnaces
Comstock - July 1938 - 2124764
Circulation of heat treatment atmospheres
Hayes - March 1942 - 2275106
Apparatus for storing and distributing heated asphalt mix
Plumb - February 1967 - 3305138
Hot mix storage bin
Brock - October 1967 - 3348739
ASPHALT MELTING KETTLE
Wollner - March 1970 - 3503382
Application Number:
05/391044
Publication Date:
10/15/1974
Filing Date:
08/23/1973
View Patent Images:
Export Citation:
Assignee:
Kimar Corporation (Keyport, NJ)
Primary Class:
Other Classes:
432/23
International Classes:
B01J19/14; B65D90/44; B65D90/22; E01C19/45
Field of Search:
126/343.5A 432/23
US Patent References:
| 3749082 | EXPANSION SYSTEM FOR ASPHALT PLANT OIL HEATER | July 1973 | Brock |
Primary Examiner:
O'dea, William F.
Assistant Examiner:
Ferguson, Peter D.
Attorney, Agent or Firm:
Popper, Bain, Bobis, Gilfillan & Rhodes
Claims:
What is claimed is
1. A protective gas generating heating system for asphalt tanks comprising,
2. A protective gas generating system for asphalt tanks comprising,
3. A protective gas generating system for asphalt tanks comprising,
4. A protective gas generating system for asphalt tanks comprising,
5. A protective gas generating system for asphalt tanks comprising,
6. A protective gas generating system for asphalt tanks comprising,
7. A protective gas generating heating system for asphalt tanks comprising,
8. A protective gas generating heating system for asphalt tanks comprising,
9. A protective gas generating heating system for asphalt tanks comprising,
10. A protective gas generating heating system for asphalt tanks comprising,
1. A protective gas generating heating system for asphalt tanks comprising,
2. A protective gas generating system for asphalt tanks comprising,
3. A protective gas generating system for asphalt tanks comprising,
4. A protective gas generating system for asphalt tanks comprising,
5. A protective gas generating system for asphalt tanks comprising,
6. A protective gas generating system for asphalt tanks comprising,
7. A protective gas generating heating system for asphalt tanks comprising,
8. A protective gas generating heating system for asphalt tanks comprising,
9. A protective gas generating heating system for asphalt tanks comprising,
10. A protective gas generating heating system for asphalt tanks comprising,
Description:
BACKGROUND OF THE INVENTION
Asphalt tanks must be heated in order to maintain the asphalt sufficiently fluid for discharge through appropriate valves and conduits in the bottom of the tank. Asphalt, particularly heated asphalt possesses the inherent quality of forming a virtually solid surface skin at the interface between the top surface of the asphalt and the atmosphere, generally air, at the top of the asphalt tank.
The virtually solid skin on the top surface of the asphalt is not dissipated when fresh asphalt is added to the tank through its top. Thus, multiple layers of spaced apart, virtually solid skin are formed as the asphalt tank is refilled from the top, each skin layer descending with the withdrawal of asphalt from the bottom of the tank until it reaches the discharge valves and conduits. The skin thereupon occludes the valves and conduits requiring the asphalt tank to be first emptied of the asphalt above the skin layer and then cleaned.
Surface skins form over varying periods of time dependent upon the type of asphalt involved. In the Roofing Industry, the asphalt has a relatively high melting point with the result that skin forms relatively rapidly resulting in the necessity of cleaning the asphalt tank three to four times per year. In the Road Surfacing Industry, the asphalt has a somewhat lower melting point with the result that skin forms somewhat less rapidly. However, even in the Road Asphalt Industry, tanks must be cleaned approximately once a year.
Because the skin which forms from the contact of air and asphalt will not remelt, raising the temperature of the tank is no avail. If an asphalt tank must be cleaned three or four times a year, present labor costs involve the expenditure of from $3,000.00 to $4,000.00 together with the loss of use of the tank during the down time.
Thus, there is great need for a system which will significantly attenuate or prevent the formation of the relatively solid skin on the surface of asphalt in the tank.
It has been found that atmospheres less reactive then oxygen with the asphalt tend to attenuate the formation of the skin. One such atmosphere is nitrogen. However, nitrogen is relatively expensive and therefore economically undesirable. Additionally, rather expensive nitrogen handling equipment must be employed to use the more economical liquid nitrogen as a source material such equipment involving a vaporizer which permits the liquid nitrogen temperature to rise sufficiently to prevent freezing of the upper surface of the asphalt.
Among the objects and advantages of the present invention is a protective gas generating heating system for asphalt tanks which generates not only the heat necessary to maintain fluidity of the asphalt but also an exhaust gas which is predominately carbon dioxide and water vapor, carbon dioxide being significantly less reactive with asphalt then air. The carbon dioxide exhaust gas from the heat generating means is withdrawn from the tank, compressed and stored in an accumulator tank for return to the top of the tank bearing the asphalt where it is employed to purge the normally present residual air substituting a blanket of non-reactive carbon dioxide.
SUMMARY OF THE INVENTION
A protective gas generating heating system for asphalt tanks comprising a tank, heat generating means in the tank, the heat generating means normally producing an exhaust gas capable of significantly retarding the formation a highly viscose surface skin on the asphalt normally generated by the action of air, an exhaust gas stack connected between the heat generating means and the exterior of the tank, gas compressor means having a low pressure inlet and a high pressure outlet, the low pressure inlet being connected to the exhaust gas stack, an exhaust gas accumulator tank connected to the high pressure outlet of the compressor means, and conduit means connected between the accumulator tank and the interior of the first said tank.
PREFERRED EMBODIMENT OF THE INVENTION
The objects and advantages aforesaid as well as other objects and advantages may be achieved by the protective gas generating heating system for asphalt tanks a preferred embodiment of which is illustrated in the drawings in which:
FIG. 1 is a schematic elevation view of the system.
Referring now to the drawings in detail, the protective gas generating heating system for asphalt tanks comprises an asphalt tank 11 having a gas or oil fired heating tube 12 mounted in the bottom thereof. The heating tube 12 comprises a fuel delivery and ignitor assembly 13 and a fire tube 14. The fire tube 14 heats asphalt 15 by means of direct conduction from the wall thereof to the asphalt and through the asphalt by convection. The heating tube 12 is well known in the Industry and in and of itself needs no further elaboration.
An exhaust gas conduit 16 is connected to the end of the fire tube 14 opposite the fuel delivery and ignitor assembly 13. The exhaust conduit 16 extends generally parallel to the fire tube 14 and then upwardly as a exhaust stack 17 which extends from the fire tube 14 to and through the top 18 of the tank 11.
The exhaust stack 17 extends through an insulating jacket 19 which is closed at its bottom 20 and which is open to the air at its top 21 which extends above the top 18 of the tank 11.
The exhaust stack 17 is connected to an exhaust conduit 22 which is in turn connected to a condensing end cooling coil 23. The condensing and cooling coil may be either air or water cooled and is of a conventional design.
The outlet end 24 of the condensing and cooling coil is connected to an automatic condensate drain 25 which is in turn connected to the low pressure inlet of a compressor 26. The high pressure outlet of compressor 26 is connected through conduit 27 to a high pressure accumulator tank 28. The high pressure accumulator tank 28 is connected through a conduit 29 to the interior of the asphalt tank 11 at its top. A pressure regulating valve 30 is operationally connected to the conduit 29 and is adapted to maintain a constant positive pressure of exhaust gas in the space 31 beneath the top 18 of the tank 11 and above the top surface 32 of the asphalt 15.
As a supplement to the system hereinbefore described, in the event that the supply of exhaust gas in the accumulator tank 28 becomes sufficiently depleted that it can no longer maintain an adequate blanket of exhaust gas in space 31 above the surface 32 of the asphalt 15, a supplemental protective gas generating system 33 may be connected through conduit 34 to conduit 29. The supplemental gas generating system 33 may be another fossil fuel combustion burner system as described with respect to the asphalt tank 11 or some other system capable of generating a compatable protective gas. The protective gas generating heating system for the asphalt tank is preferably operationally connected to controls for the auxiliary generating system 33 so that in the event that there is inadequate pressure in accumulator tank 28, the supplemental system 33 is automatically energized.
In operation, the protective gas generating heating system is energized by energizing the fuel supply and ignitor assembly 13 which generates flame within the fire tube 14. Since the system is heated by combustion of a fossil fuel, the exhaust gas is predominatly carbon dioxide and water vapor with small quantities of carbon monoxide. The exhaust gas passes through exhaust conduit 16 to the exhaust stack 17. The jacket 19 prevents the formation of a skin on the stack 17 which would tend to be generated by reason of its high temperature driving off the lower boiling point constituents of the asphalt. Air circulating through the open top of the jacket 19 cools the jacket to a sufficiently low temperature so as to prevent the formation of an asphalt skin thereon.
The exhaust gas passes from the stack 17 through conduit 22 to a condensing and cooling coil where water vapor condenses out and the temperature of the exhaust gas is significantly lowered. Water condensate is automatically drained through the automatic condensate drain 25 and the water free cooled exhaust gas passes to the low pressure inlet of compressor 26. Compressor 26 raises the pressure of the exhause gas and and passes it through conduit 27 to an accumulator tank 28.
Exhaust gas under positive pressure is automatically fed through pressure regulator 30 to the interior of the tank 11 through conduit 29 passing into the space 31 beneath the top 18 of the tank 11 and the upper surface 32 of the asphalt 15 thereby purging air therefrom through purge valve 35. The predominately carbon dioxide exhaust gas prevents the formation of the nearly solid skin on top of the asphalt 15.
Asphalt is normally added to an inlet valve 36 at the top of the tank 11 and withdrawn through an outlet 37 in the bottom. Under proper operating conditions, the level of asphalt 15 is never lowered to a level below the top of the fire tube 14 otherwise a skin would tend to form on the fire tube due to its high temperature. If the tank 11 is to be drained the fire tube 14 is preferably shut down so that its surface temperature is not so high as to generate a skin as the level of the asphalt descends beneath the level of the fire tube 14. Appropriate controls may be provided to prevent the lowering of the asphalt.
The purge valve 35 is also preferably adapted to maintain at least a slight positive pressure in the tank 11 above the top 22 of the asphalt 15 to prevent unintended air intrusion.
Under normal operating conditions, there is sufficient exhaust gas generated by the heating tube 12 to provide a protective air blanket in space 31 at all times. Nevertheless, an auxiliary protective gas generating heating system as a safeguard.
The foregoing description is merely intended to illustrate an embodiment of the invention. The component parts have been shown and described. They each may have substitutes which may perform a substantially similar function; such substitutes may be known as proper substitutes for the said components and may have actually been known or invented before the present invention.
Asphalt tanks must be heated in order to maintain the asphalt sufficiently fluid for discharge through appropriate valves and conduits in the bottom of the tank. Asphalt, particularly heated asphalt possesses the inherent quality of forming a virtually solid surface skin at the interface between the top surface of the asphalt and the atmosphere, generally air, at the top of the asphalt tank.
The virtually solid skin on the top surface of the asphalt is not dissipated when fresh asphalt is added to the tank through its top. Thus, multiple layers of spaced apart, virtually solid skin are formed as the asphalt tank is refilled from the top, each skin layer descending with the withdrawal of asphalt from the bottom of the tank until it reaches the discharge valves and conduits. The skin thereupon occludes the valves and conduits requiring the asphalt tank to be first emptied of the asphalt above the skin layer and then cleaned.
Surface skins form over varying periods of time dependent upon the type of asphalt involved. In the Roofing Industry, the asphalt has a relatively high melting point with the result that skin forms relatively rapidly resulting in the necessity of cleaning the asphalt tank three to four times per year. In the Road Surfacing Industry, the asphalt has a somewhat lower melting point with the result that skin forms somewhat less rapidly. However, even in the Road Asphalt Industry, tanks must be cleaned approximately once a year.
Because the skin which forms from the contact of air and asphalt will not remelt, raising the temperature of the tank is no avail. If an asphalt tank must be cleaned three or four times a year, present labor costs involve the expenditure of from $3,000.00 to $4,000.00 together with the loss of use of the tank during the down time.
Thus, there is great need for a system which will significantly attenuate or prevent the formation of the relatively solid skin on the surface of asphalt in the tank.
It has been found that atmospheres less reactive then oxygen with the asphalt tend to attenuate the formation of the skin. One such atmosphere is nitrogen. However, nitrogen is relatively expensive and therefore economically undesirable. Additionally, rather expensive nitrogen handling equipment must be employed to use the more economical liquid nitrogen as a source material such equipment involving a vaporizer which permits the liquid nitrogen temperature to rise sufficiently to prevent freezing of the upper surface of the asphalt.
Among the objects and advantages of the present invention is a protective gas generating heating system for asphalt tanks which generates not only the heat necessary to maintain fluidity of the asphalt but also an exhaust gas which is predominately carbon dioxide and water vapor, carbon dioxide being significantly less reactive with asphalt then air. The carbon dioxide exhaust gas from the heat generating means is withdrawn from the tank, compressed and stored in an accumulator tank for return to the top of the tank bearing the asphalt where it is employed to purge the normally present residual air substituting a blanket of non-reactive carbon dioxide.
SUMMARY OF THE INVENTION
A protective gas generating heating system for asphalt tanks comprising a tank, heat generating means in the tank, the heat generating means normally producing an exhaust gas capable of significantly retarding the formation a highly viscose surface skin on the asphalt normally generated by the action of air, an exhaust gas stack connected between the heat generating means and the exterior of the tank, gas compressor means having a low pressure inlet and a high pressure outlet, the low pressure inlet being connected to the exhaust gas stack, an exhaust gas accumulator tank connected to the high pressure outlet of the compressor means, and conduit means connected between the accumulator tank and the interior of the first said tank.
PREFERRED EMBODIMENT OF THE INVENTION
The objects and advantages aforesaid as well as other objects and advantages may be achieved by the protective gas generating heating system for asphalt tanks a preferred embodiment of which is illustrated in the drawings in which:
FIG. 1 is a schematic elevation view of the system.
Referring now to the drawings in detail, the protective gas generating heating system for asphalt tanks comprises an asphalt tank 11 having a gas or oil fired heating tube 12 mounted in the bottom thereof. The heating tube 12 comprises a fuel delivery and ignitor assembly 13 and a fire tube 14. The fire tube 14 heats asphalt 15 by means of direct conduction from the wall thereof to the asphalt and through the asphalt by convection. The heating tube 12 is well known in the Industry and in and of itself needs no further elaboration.
An exhaust gas conduit 16 is connected to the end of the fire tube 14 opposite the fuel delivery and ignitor assembly 13. The exhaust conduit 16 extends generally parallel to the fire tube 14 and then upwardly as a exhaust stack 17 which extends from the fire tube 14 to and through the top 18 of the tank 11.
The exhaust stack 17 extends through an insulating jacket 19 which is closed at its bottom 20 and which is open to the air at its top 21 which extends above the top 18 of the tank 11.
The exhaust stack 17 is connected to an exhaust conduit 22 which is in turn connected to a condensing end cooling coil 23. The condensing and cooling coil may be either air or water cooled and is of a conventional design.
The outlet end 24 of the condensing and cooling coil is connected to an automatic condensate drain 25 which is in turn connected to the low pressure inlet of a compressor 26. The high pressure outlet of compressor 26 is connected through conduit 27 to a high pressure accumulator tank 28. The high pressure accumulator tank 28 is connected through a conduit 29 to the interior of the asphalt tank 11 at its top. A pressure regulating valve 30 is operationally connected to the conduit 29 and is adapted to maintain a constant positive pressure of exhaust gas in the space 31 beneath the top 18 of the tank 11 and above the top surface 32 of the asphalt 15.
As a supplement to the system hereinbefore described, in the event that the supply of exhaust gas in the accumulator tank 28 becomes sufficiently depleted that it can no longer maintain an adequate blanket of exhaust gas in space 31 above the surface 32 of the asphalt 15, a supplemental protective gas generating system 33 may be connected through conduit 34 to conduit 29. The supplemental gas generating system 33 may be another fossil fuel combustion burner system as described with respect to the asphalt tank 11 or some other system capable of generating a compatable protective gas. The protective gas generating heating system for the asphalt tank is preferably operationally connected to controls for the auxiliary generating system 33 so that in the event that there is inadequate pressure in accumulator tank 28, the supplemental system 33 is automatically energized.
In operation, the protective gas generating heating system is energized by energizing the fuel supply and ignitor assembly 13 which generates flame within the fire tube 14. Since the system is heated by combustion of a fossil fuel, the exhaust gas is predominatly carbon dioxide and water vapor with small quantities of carbon monoxide. The exhaust gas passes through exhaust conduit 16 to the exhaust stack 17. The jacket 19 prevents the formation of a skin on the stack 17 which would tend to be generated by reason of its high temperature driving off the lower boiling point constituents of the asphalt. Air circulating through the open top of the jacket 19 cools the jacket to a sufficiently low temperature so as to prevent the formation of an asphalt skin thereon.
The exhaust gas passes from the stack 17 through conduit 22 to a condensing and cooling coil where water vapor condenses out and the temperature of the exhaust gas is significantly lowered. Water condensate is automatically drained through the automatic condensate drain 25 and the water free cooled exhaust gas passes to the low pressure inlet of compressor 26. Compressor 26 raises the pressure of the exhause gas and and passes it through conduit 27 to an accumulator tank 28.
Exhaust gas under positive pressure is automatically fed through pressure regulator 30 to the interior of the tank 11 through conduit 29 passing into the space 31 beneath the top 18 of the tank 11 and the upper surface 32 of the asphalt 15 thereby purging air therefrom through purge valve 35. The predominately carbon dioxide exhaust gas prevents the formation of the nearly solid skin on top of the asphalt 15.
Asphalt is normally added to an inlet valve 36 at the top of the tank 11 and withdrawn through an outlet 37 in the bottom. Under proper operating conditions, the level of asphalt 15 is never lowered to a level below the top of the fire tube 14 otherwise a skin would tend to form on the fire tube due to its high temperature. If the tank 11 is to be drained the fire tube 14 is preferably shut down so that its surface temperature is not so high as to generate a skin as the level of the asphalt descends beneath the level of the fire tube 14. Appropriate controls may be provided to prevent the lowering of the asphalt.
The purge valve 35 is also preferably adapted to maintain at least a slight positive pressure in the tank 11 above the top 22 of the asphalt 15 to prevent unintended air intrusion.
Under normal operating conditions, there is sufficient exhaust gas generated by the heating tube 12 to provide a protective air blanket in space 31 at all times. Nevertheless, an auxiliary protective gas generating heating system as a safeguard.
The foregoing description is merely intended to illustrate an embodiment of the invention. The component parts have been shown and described. They each may have substitutes which may perform a substantially similar function; such substitutes may be known as proper substitutes for the said components and may have actually been known or invented before the present invention.