Murphy, Charles H. (Northumberland, EN)
Udy, Lex L. (Salt Lake City, UT)

05/231162

01/08/1974

03/02/1972

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Ireco Chemical (Salt Lake City, UT)

86/20.120

264/3.300

C06B21/00; C06D1/08

86/2R,2C,47 264/3B 149/14-16,2 53/140

3380333	System for mixing and pumping slurry explosives	April 1968	Clay et al.
3552259	PROCESS AND APPARATUS FOR PREPARING DETONATING AND DEFLAGRATING FUSE AND PRODUCT	January 1971	Griffith
3597516		August 1971	Harwood

Lechert Jr., Stephen J.

Bingham, Robert A.

What is claimed is

1. Apparatus for preparing and packaging stick slurry explosives in a continuous fashion comprising, in combination, means for supplying a liquid solution of inorganic oxidizer to a mixing zone at a controlled rate, means for supply particulate solids suspendible in said liquid solution to said mixing vessel also at controlled rates, means for mixing the liquid solution and salt particles together at said zone to form a pumpable slurry, means for continuously pumping the resulting slurry from said zone into and through an extrusion tube while continuously feeding a wrapper material along and around said tube, thereby extruding the slurry from said tube into the wrapping material which is formed to completely encircle the extruded slurry in a tube-like stick, means for allowing the packaged slurry to continually proceed forwardly in the direction of extrusion, means for tying off the outer end of a length of wrapper material placed around the extrusion tube, means for collapsing the tubular wrapper between adjacent filled portions, means for applying a pair of sealing clips to the collapsed portion and means for cutting the tubular wrapper between adjacent clips.

2. Apparatus according to claim 1 which includes means for injecting gas into the packaged slurry.

3. Apparatus according to claim 1 which includes a surge chamber in the form of an elastic expandable tube and a rigid wall member surrounding said tube to limit its expansion.

4. Apparatus according to claim 1 which includes means for opening up a flattened tubular wrapper, means for slitting said tubular wrapper longitudinally to enable it to by-pass a slurry supply connection, and means for applying a sealing tape longitudinally of the wrapper to reseal the slitted parts.

BACKGROUND AND PRIOR ART

It has been proposed in the past to form slurry explosive compositions into "sticks" of slender packages of sizes suitable for use like conventional sticks of dynamite. In general, however, slurry explosive compositions, which have been very successful in large scale blasting operations, have not been formed in sticks but have been used almost entirely in bags or in bulk in large diameter columns. Unpackaged slurry is often poured or pumped directly into boreholes. In some cases, it has been packaged in relatively large bags but it has not been used commercially, to any substantial extent, in small "sticks." One reason for this is the fact that most slurry explosives, i.e., those made by suspending fuel particles, such as aluminum, coal, gilsonite, sulfur, and/or granules or grains of self-explosive materials, such as TNT, smokeless powder and the like, in solutions of ammonium nitrate in water, etc., are extremely insensitive. They are therefore difficult and often impossible to detonate in small diameters.

However, more sensitive compositions are known and some of these are coming into use. In an application by Cook and Bailey, Ser. No. 497,442, filed Oct. 18, 1965, for example, a relatively sensitive slurry is described which is or can be made cap sensitive in relatively small diameters. Other and still more sensitive blasting slurries have been discovered recently so that there are now available a variety of explosive compositions of slurry type which can be detonated in slender or "stick" form. These can be used, therefore, in much the same way that dynamite has been used in the past, if they are suitably packaged, but packaging involves difficulties because of the semi-fluid character of the slurries.

Some of the new compositions have several advantages over dynamite. They are less expensive; in many cases, they can be compounded of fertilizer grade nitrates and various sensitizing materials which are locally available in various parts of the world. Some of them can be "tailor-made" to meet specific requirements. Most of them can be manufactured in bulk readily by use of simple equipment. Moveover, they often can be prepared in the field at or near the point of use.

These slurry explosives often have additional advantages in that they can be made of ingredients which individually are quite safe to handle. This simplifies problems of supply and handling. Until the particulate fuels, such as finely divided aluminum, carbonaceous materials, etc., for example, are actually incorporated into oxidizer solutions, e.g., of ammonium nitrate, sodium nitrate, etc., both the particulate and the liquid components can be shipped in bulk and handled without particular care.

Packaging machinery, e.g., for conventional plastic dynamites of the prior art, has been somewhat complex. It generally is not suited for slurry handling and does not lend itself to use in the field. The precautions necessary with the more sensitive conventional explosives, such as dynamites and blasting gelatins, also have inhibited manufacture or packaging of such materials in the field.

A particular object of the present invention is to make possible the manufacture and packaging of explosive slurries in bulk, followed by immediate packaging in small, slender packages or sticks, using relatively simple equipment which can be operated away from complex facilities, if desired. A further object is to design combination mixing and packaging equipment that is readily portable so that it can be shifted from place to place in the field, if desired. Another object is to convert separate supplies of liquid and particulate solids into sticks of finished explosives, without requiring use of extensive machinery or other equipment. Still another object is to so design the equipment that it can be operated by relatively unskilled personnel. Other objects and advantages will appear from the fuller description given below.

SUMMARY OF THE INVENTION

A relatively simple apparatus which is self-inoperable in the field if desired, is supplied with solution from a tank and with particulate fuels and other solids from bulk packages such as barrels. Simple metering and stirring devices are used to blend these ingredients and form a homogeneous slurry. Preferably, ingredients include a thickener which will cause a liquid phase to gel or become quite viscous after a short but predictable time interval. The slurry, with a thickening agent included but not yet fully effective, for example, is pumped by an air driven or hydraulically driven diaphram pump through an extrusion tube whereby it may be subsequently packaged, and in meantime, thickened further to the stiff consistency desired in the finished product.

The diaphragm pump, followed by a surge chamber, provides a somewhat constant pressure which allows the slurry explosive to be extruded in a continuous manner, and thus by using a packaging means also operating in a continuous manner, the slurries may be mixed, pumped and extruded in a continuous and automatic fashion. The wrapper material, such as polyethylene or equivalent sheet or film of plastic material, is impregnated or coated. It may be supplied in the form of plastic ribbon in large rolls which may be unrolled and shaped around the extruding slurry by means of a round hollow mandrel. Plastic preformed tubing may be used which can be cut or split lengthwise to form a ribbon-like strip and then reformed around the extruded slurry. After being formed around the slurry, the material may then be sealed in a conventional manner such as by using tape. Alternatively, a self-locking "Zippertube" method may be used to close the longitudinal seam. Both of these procedures are common in the packaging art. The "Zippertubing" method consists of using a "zipper" or specially designed self-locking tube in appropriate apparatus to seal the longitudinal edges of the sheet material and thus form a circular packaging tube. Plastic tubing may also be prebunched or gathered over the end of the extrusion tubes in a sleeve-like or telescopic manner. The bunched tubing can then be filled by the continuously extruded rod-like slurry and pulled off the extrusion tube as filling is completed. As soon as a stick length of explosive is extruded into and packaged by the plastic tubing, an automatic tying and cutting device squeezes or collapses the tube shut and applies two ties or clips around the tubing to separate any two adjoining sticks. A cutter also severs the tubular wrap material between these two ties; thus, separate sticks of predetermined length are formed, tied and cut off, until the roll or gathered bunch of packaging material is exhausted, or nearly so. By using a roll of packaging material, a large quantity of tubing may be provided and thus the process may be kept continous for a long period of time. When it is necessary to replace the roll of tubing material, little if any delay in replacing the roll is entailed. Thus, for all practical purposes, the process may be considered to be continuous, which is often quite essential especially where time is a factor in the thickening and setting up of the stick slurries after mixing and precedent to the extrusion and packaging.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective and somewhat exploded view of apparatus of the present invention showing mixing and packaging equipment combined.

FIG. 2 shows a group of detachable hollow mandrels suitable for filling tubular wrapping material with slurry.

FIG. 3 is a diagramatic view showing the separating of individual sticks following the filling operation.

FIG. 4 is a plan view of a modified system for mixing and packaging slurries.

FIG. 5 is a side view of an alternative modification of packaging means.

FIG. 6 is a detail sectional view taken on line 6--6 of FIG. 5.

FIG. 7 shows a detail view of pump and valve mechanism for supplying liquid oxidizer solution to the slurry mixer.

DESCRIPTION OF PREFERRED EMBODIMENTS

Referring now to FIG. 1, the apparatus shown comprises a liquid supply tank 11 which may be filled with an aqueous solution of any suitable inorganic oxygen-supplying salt. Normally the preferred solution comprises an aqueous solution, i.e., where water alone or a mixture of water and a compatible organic liquid such as formamide or ethylene glycol is more or less saturated with ammonium nitrate, which may be combined with sodium nitrate and/or calcium nitrate. However, any of these ingredients may be eliminated and other choices or combinations of well known oxidizer salts may be used, such as ammonium and/or alkali or alkaline earth metal perchlorates, chlorates and nitrates, as is well known in the art. The solution supplied to tank 11 will normally be saturated or substantially so, and may be at a somewhat elevated temperature above the ambient so as to contain relatively high concentrations of the oxidizer salt.

Salts in dry form, such as ammonium nitrate prills, may be supplied to the tank 11 through a line 13 from a conventional bin or other source, not shown. A valve 15 is provided for controlling flow of solids from pipe 13 into tank 11. Another conduit or pipe 16, provided with a valve 17, can supply the same or other oxidizer salts in dry form to a dispenser vessel 19. The feeding action shown here is by gravity, but suitable augers or other known conveying means can be used if desired.

Another vessel or barrel 21 is provided for supplying fuels, e.g., finely divided carbonaceous solids such as coal or gilsonite, or powdered aluminum, etc., in the form of particulate solids. Additional containers 31 may be added besides the vessels 19, 21, all of them being supported on a hopper or trough 23. Means are provided for controlling the rate of flow of particulate solids from each vessel, 19, 21, etc. A valve 25 for controlling liquid flow rate is installed in line 27, which leads from the lower part of vessel 11 to a mixing compartment or station 30. An auger 34 in the lower part of vessel or trough 23 may be driven by appropriate mechanism to move the solids from outlets of vessels 19 and 21 at appropriate rate into the mixing operation. At station 30 the liquid and particulate solids ingredients are mixed together to form a homogenous slurry. The mere act of flowing the liquid and solids together through the trough is often sufficient for mixing them, especially when they go through a delivery pump immediately thereafter, but if required, an impeller type mixer or other stirring device, not shown, may be incorporated in the lower part of mixer 30. Such mixing equipment is of well known type and need not be described in detail.

The mixing apparatus connects to an outlet tube 38 connected to a delivery line 42. A pump 44, shown diagramatically only, preferably as an air operated diaphragm pump, is provided to impel to impel the freshly mixed slurry from vessel 23, 30, through extrusion tubes and into the plastic receptacle or tubing to be packaged as shown in FIG. 1 and described more fully below.

After the slurry leaves the air operated diagraphm pump it immediately passes through a delivery line 101. Two such lines are shown, and appropriate valve means, not shown, may control the flow of slurry alternately into one or the other. The preferred type of delivery line is shown at 102 in FIG. 4. It consists of a soft elastic expandable rubber hose 103 encased in a metal tube 104 prior to entering the extrusion tubes 105 and 106. This rubber hose has an outside diameter of less than the inside diameter of the metal casing so as to allow the hose to expand if necessary and thus it acts as a surge chamber. The diaphragm pump 44 produces relatively little pressure pulsation or surging of the slurry and this may be adequately handled by the resultant surging or expanding of the rubber hose 103.

From the hose 102, which constitues a surge chamber, the slurry is pumped through a conduit 71, FIG. 1, where it branches at tee, through alternate valves 107, into the two extrusion tubes 105 and 106. Valves 108 and 109 are provided further to control the flow rate of the slurry into each tube. These valves may be manually operated, but preferably are operated by solenoids or by hhydraulic fluid or by compressed air.

Any packaging material that is suitable for wrapping sticks of the plastic slurry explosive composition and keeping the latter material and its flexible, plastic or semi-plastic condition may be used to receive slurry from the extrusion tubes 105 and 106. Preferably, the wrapper material is a polyethylene packaging material in tubular form or which can be shaped into a tubular form. Polyethylene is preferred since it has significant fuel value which can be calculated into the oxygen balance of the slurry and thus act as an ingredient in itself. This will allow for the packaging to be consumed during the explosion and also to contribute energy to the explosion itself.

Packaging material in flat, web or ribbon-like state must be formed or shaped around the extrusion nozzle to receive the slurry and then be sealed. Any simple method may be employed to form and seal the packaged material around the extruded rod-like slurry. One method is to use a flattened tubular material, which is opened up and guided around the extrusion tube, being slit open and later resealed. In another case, a flat web is shaped around a round mandrel which guides and shapes the plastic ribbon-like material around the extrusion nozzle slurry as wrapper material passes outside and the slurry passes simultaneously through the mandrel. After the material is shaped tube-like around the slurry, in either of these cases, it may be sealed with a longitudinal seal by taping the longitudinal wrapper edges with tape which is unrolled and applied continuously as the extruded slurry and surrounding packaging material pass respectively through and around the mandrel.

Where preformed plastic tubing is used to begin with, an apparatus as shown in FIG. 5, may be employed. As shown, the preformed tubing 110 supplied from a roll 112 and guided by a plow element 114 on the advance end of a mandrel or extrusion tube 116, is cut lengthwise by a suitably placed cutter 118, such as a razor blade or similar slitting device.

The slit tubing is then guided past the slurry entry which is shown as a tube 120 and is shaped around the round hollow mandrel 116 where it is thereby reformed around the exit end of the extrusion tube 122. The latter is a continuation of the forming mandrel 116, ahead of the extruded slurry, and the cut slit is taped together, forming a tubular enclosure which receives the slurry further down the line. As shown, the tape 125 is supplied continuously from a roll 126 and is applied by two contoured pressure rollers 128 and 129, FIG. 6, which guide the wrapper in preparation to receive the extruded slurry and which also seal down the tape just ahead of the emerging slurry.

Another means by which the extruded slurry may be enclosed in tubing is by the use of "Zippertubing." "Zippertubing" is a known commercial method of packaging which consists of using a specially formed "zipper" edge tube, and closing the longitudinal seam by mechanism designed to "zip" together the longitudinal edges of the previously flat web or ribbon-like material to thus form a hollow enclosed tube of packaging material. By using this method, the rod-like slurry is extruded from tubes 105 or 106, FIG. 4, or tube 122, FIG. 5, and is packaged and sealed in a continuous fashion. The actual method selected for packaging the extruded slurry is not extremely important. Any suitable means for continuously forming and sealing the packaged material around the rod-like extruded slurry can be used.

Lengths of plastic preformed tubing of thin wall type may also be pre-bunched in a sleeve-like or telescopic manner over the end of the extrusion tube. FIGS. 1 and 3 show such a system. After placing and gathering the tubing W on a replaceable hollow mandrel 72, the outer end of the tubing may be tied off to close it. A small metal clip C may be used as the tie. Then, with valves 107 and 108 open, FIG. 4, the slurry flows under pressure through the extrusion tube 72 or mandel into the end of the sealed tubing. This flow starts to pull the telescoped wrapper off the filler tube 72, filling the tubing much like a sausage is filled, as flow of explosive slurry continues. The tubes 72 are connected, as shown in FIG. 1, to the valve mechanism which receives slurry from the pump 44 through supply lines 101 and 71.

Using the packaging means as shown in FIG. 5, a conventional tying and cutting-off device is shown diagramatically at 80. It is arranged at the end of the extrusion tube 122 and associated packaging mechanism so that the tubular wrapper W, which initially extends slightly beyond the tip of the extruded slurry, may first be tied off to close it. The metal clip C, FIG. 3, is used as the tie. Thereafter, the slurry flows under pressure from the air operated diaphragm pump 44 through the mandrel or filler tube and into the end of the wrapping material. This flow starts to pull off the wrapper from its gathered supply, thus filling the wrapper as the flow of explosive material continues. When the wrapper has been pushed off the filler tube for the length of a stick, the tying apparatus 80 is actuated again to press the tube or wrapper filled with fluid explosive such that the wrapper is pinched together forcing the fluid explosive to either side of the pinch and to apply two clips or seals C spaced far enough apart so that the wrapper can be cut between them at S, FIG. 3, and thus separate the tubing into individual filled sticks. The seals C may be metal bands or adhesive clips or tapes, or seals may be tied of cord or other suitable material. These are indicated generally at the ends of sticks 81 and 82, FIG. 3. A cutting knife 83 operated in conventional fashion by any suitable means, not shown, severs the first stick 81 from the portion of tubing 84 which follows. The operation is repeated for each new stick length.

As extrusion of the composition continues, the newly tied off wrapper portion is pushed by the extruding explosive along and outside the tube-shaping mandrel and under the longitudinal sealing device. This causes the wrapper to unroll from its supply reel in a continuous fashion and to then be shaped around the extruded slurry to form the filled tubes of slurry. A new tying operation takes place as each new tube length has been filled, as indicated in FIG. 3. Here the second stick or package 81 is shown as being formed and severed by the knife 83. This operation is continued step by step until the wrapping material is exhausted. Then a new supply of tubing, on a spare mandrel 72, FIG. 2, can be quickly placed in operation by detaching the one whose wrapper has been consumed, attaching a new one, and beginning the process over again.

The outer end of the mandrel 72, as shown in FIG. 1, is adapted to rest on or just above the table 95. The freshly severed stick S ₁ may be pushed off by the next succeeding stick, or so disposed that it falls on to a traveling conveyor belt 97. The latter, which is carried and driven by a roller 98 conveys the sticks to a suitable receptacle, such as a box, for final packaging. FIG. 3 shows some of these parts on a larger scale. In FIG. 5, an analogous arrangement includes a final delivery belt 133 on rollers 134 and 135.

In a typical production operation, the solid particulate fuel material is contained in a vessel such as 21. This is commonly referred to as a "premix," often consisting of a blend of fuel and thickener particles in solid form. It may consist of finely divided aluminum mixed with coal, gilsonite, or sulfur, or any two or more of these. It may include additional ingredients for imparting energy to the explosive. Ordinarily, it will include a small amount of a hydratable gum, thickener, or gelling agent, such as guar gum or equivalent, for converting the liquid phase to a viscous gel. This is well known in the art. Additional oxidizer salt in dry form may be supplied from a vessel such as 19. This may be the same salt as or different from that contained in the solution in tank 11. The reason for supplying additional oxidizer in dry form may be to thicken up the mix, to add energy, or to achieve better oxygen balance, or for all these purposes. This dry oxidizer and the other particulate ingredients are safe to handle individually and can be shipped directly from suppliers to the site. The solution in tank 11 can be prepared either off site or on and blended at site with the particulate solids at or near the mine, for example, where the explosives are going to be used.

The operator calibrates the flow of each ingredient from its hopper tank so that the desired blend of materials is received into the mixer 30. The formulation can be changed in the field at any time. The mixed materials are then blended together and pumped by the air operated diaphram pump 44 through the extrusion tubes to be subsequently packaged into tied and cut sticks of slurry, as described above.

When the system is set up for operation, the ingredients are first prepared and placed in the apropriate vessels 11, 19, 21 and others not shown, if needed. The operator calibrates the flow of each ingredient and starts the mixing operation. As the air operated diaphram pump forces the slurry through the extrusion tube, the wrapping material is shaped around the extruded rod-like slurry and is unrolled from its roll step by step as it fills, being tied and cut to length as each stick is completed. This tying and cutting is done under control of the packaging operator. Separate rolls of packaging material may be kept at a convenient place for fast replacement when one roll is extinguished.

The extrusion tubes 72, of which three spares are shown in FIG. 2, comprise preferably thin-walled stainless steel tubing of appropriate diameter. The material selected should be resistant to corrosion or chemical attack by the ingredients of the explosive, which of course, includes salts, which will attack many metals, such as ammonium nitrate, sodium nitrate, calcium nitrate, and the like. The thin-walled polyethylene tubing which is used as wrapper, may be of any of the "lay-flat" type, seamless type or any other type having longitudinal seams. A ball check valve 140 may be incorporated in the connector 71, FIG. 1, to prevent kickback of slurry due to pressure in the mandrel or the tube that has not yet been tied off and cut.

The tying machine which has been referred to above, is desirably of a type well known in the art which feeds and crimps small aluminum clips or bands around the wrapper W. These are placed about one-half or three-quarters of an inch apart on the tube for packages of one to one and a half inches in diameter. As the clips are closed, the cutter simultaneously cuts the wrapper between them, thus separating each packaged charge in turn from the unfilled tubing. The cyclic rate of operation may vary widely, e.g., from 25 to 100 cycles or more per minute, usually in the range of about 40 to 70.

The belt conveyor 97 is not always absolutely necessary, but is a convenience. It can be used to package the sticks in boxes, not shown, with very little manual control or adjustment. Supplementary equipment of conventional type may include means for sealing the boxes. In addition, other mixing, blending and/or holding facilities may be desirable, for example, a means for combining water, glycol, AN, SN, CaN, and the like, for producing additional quantities of the solution for tank 11; blending means may be used also for preparing the "pre-mix" for tank 21, etc. In order to facilitate solution blending in the open, particularly in cooler weather, it may be necessary to have a heating facility such as a hot water heater or boiler so that the liquid ingredients, especially water or other solvents for oxidizer salts, may be heated. If necessary, the temperature in tank 11 can be maintained at a desired elevated level, to make certain that salts will not crystallize out of the solution prematurely. Generally speaking, the raw materials used in the finished composition, including particulate fuels, such as finely divided aluminum, gilsonite, other carbonaceous materials, gums, starches and/or other thickening agents, or gel-formers, cross-linking materials, and the like, will be stored separately to avoid hazards of explosion. The system thus can be made entirely safe since nothing explosive is produced in most cases until the materials which make up the final blasting agents are actually blended together.

FIG. 4 shows an embodiment having several desirable control features. Slurry from a suitable mixer, not shown in this figure, is fed through an outlet nozzle 141 into a funnel 143. From here it flows into a peristaltic slurry pump 145, driven hydraulically by a pressure line 147 powered by master pump 151. The latter is replenished with hydraulic fluid from a sump 153. Hydraulic return line 155 brings the hydraulic drive fluid back from slurry pump 145.

It is often desirable to aerate the slurry somewhat as it is packaged. For this purpose, air may be supplied from a suitable pressure source, not shown, through a line 160, FIG. 4. The air passes through a filter-lubricator unit 162 and through a pressure regulator 164 into line 165 which feeds it into the pump outlet line 168. A cut-off valve 166 is provided in line 165. A bleed line 169 with cut-off valve 170 is provided for bleeding air out of the slurry for starting up. The slurry flows through a line 172 into the surge chamber 102 comprised of the elastic hose 103. The latter may be banded at intervals, as shown at 175, to control the surge capacity, the outer limit of expansion of the elastic hose being determined by the walls of the confining cylinder 104, which is not expandable at the pressures involved.

FIG. 7 shows a convenient valve arrangement for pumping and controlling the oxidizer solution, as in tank 11, FIG. 1. The solution is drawn out near the bottom through valve 25 and part or all of it may be recycled to the top through line 180. This prevents crystallization of the salt on standing which might otherwise occur. Solution pump 182 forces the solution from tank 11 or equivalent to the mixer through line 184, but a variable valve 186, controlled by hydraulic means 188, can be set as desired to recycle from zero to 100 percent of the solution stream to tank 11 through line 180.

A means may be provided also, as shown at 191, FIG. 1, for spraying and washing the sticks as they leave the packaging apparatus, e.g., to remove slurry which may be contaminating the exterior of the package. Also, a printing device 193 is provided to date or otherwise label each stick that is packaged.

Control of slurry consistency for pumpability and extrusion in final desired consistency in the package can be obtained by proper control or choice of thickener, cross-linking agents, and delaying agents, amounts of liquid, addition of undissolved salts, etc., as is now well known in the art.

Obviously, many variations and combinations are possible in addition to those already mentioned and it is intended by the claims which follow to cover the invention as broadly as the prior art properly permits.