US3456357A - Process for continuous automated vibrational drying of explosives and apparatus - Google Patents

Description

July 22, 1969 G. L. GRIFFITH PROCESS FOR CONTINUOUS AU'IOMA'FED VIBKA'I'IONAL URYINCI OF' EXPLOSIVES ANI) APPARATUS 7 sheets-sheet 1 Filed Feb. 5. 1968 July 22, 1969 G. L. @mmm 3,456,357

PROCESS FOR CONTINUOUS AUTOMATED VIBRATIONAL DRYING OF EXPLOSIVES AND APPARATUS- 7 Sheets-'Sheetlf'l Filed Feb. 5, 1968 ANI) APPARATUS 7 Sheets-Sheet July 22, 1969 G. L. GRIFFITH PROCESS IO( CONTINUOUS AUTOMA''E) VIBHA'I'ONAI: URYING OII EXILOSVHS med Feb. 5. 196el July 22, 1969 cs. L. GRIFFITH 3,456,357

PROCESS FOR CONTINUOUS UTOMATED VIBRATIONAL DRYING OF EXPLOSIVES AND APPARATUS Filed'Feb. 5, 1968 '7 Sheets-Sheet 4 .if 45a.

July 22, 1969 G. L. GRIFFITH 3,456,357

FEOCESS FOR CONTINUOUS AUTOMATED VIBRATINAL DRYING OF EXPLOSIVES AND APPARATUS July 22, 1969 PROCESS F'OH CONTINUOUS AUTO EXPLOSIVES AND APPARATU 7 Sheets-Sheet 6 Filed Feb.

July 22, 1969 G. 1 GRIFFITH 3,456,357

PROCESS FOR CONTINUOUS AUTOMATED VIBRATIONAL DRYING OF EXPLOSIVES AND APPARATUS CURVE I cuRvE In NI HIV m S'dINVSE zoo- Loo f United States Patent O 3,456,357 PROCESS FOR CONTINUOUS AUTOMATED VIBRATIONAL DRYING F EXPLOSIVES AND APPARATUS George L. Griiiith, Coopersburg, Pa., assignor to Commercial Solvents Corporation, New York, N.Y., a corporation of Maryland Filed Feb. 5, 1968, Ser. No. 702,852 Int. Cl. F2611 21/14, 3/06, 17/10 U.S. Cl. 34-28 33 Claims ABSTRACT 0F THE DISCLOSURE A process and drying apparatus designed for continuous and automated operation are provided, for drying nitrostarch, nitrocellulose, and other inflammable or detonable explosives. The apparatus comprises an elongated vibrated enclosure through which, optionally, hot drying gases can circulate over but not through a moving bed of explosive particles, and/or which optionally is heated, the explosive particles tumblingly progressing from one end to the other of the elongated enclosure in a continuous manner while they dry, so that wet explosive particles enter at one end, and dry explosive particles emerge at the other end, for immediate packaging.

This invention relates to a process and apparatus for drying explosive particles of an inflammable or detonable nature, and more particularly to an apparatus having an elongated enclosure through which the explosive particles are tumbled while the entire enclosure is vibrated, and While the particles are dried either by heating, or under and in a current of drying gas that is iiowed thereover, or both, adapted for continuous automated operation in a manner such that the explosive particles are moved continuously from one end to the other of the elongated enclosure, and to a continuous process for drying explosive particles by heating them and/ or by passing a current of hot gas over a tumbling bed of particles passing through a drying zone, the tumbling movement serving to move the particles from one end of the drying zone one to the other.

The manufacture of easily ignited explosive sensitizers in particle or powdered form, such as nitrostarch and nitrocellulose, has long presented an extreme hazard. These explosives when dry can ignite, and turn over from burning to detonation when heated too much, when exposed to flame, or when subjected to pressure or friction, so that the drying step is usually the most hazardous operation in the process. Up to that point in the manufacture, these explosives are not as sensitive to detonation or to turning over from burning to detonation, because they are wet. They are therefore processed wet for as long as possible, but eventually of course, they must be dried, with the attendant drying hazard.

ln the usual drying process, nitrostarch and nitrocellulose are loaded on trays which are stacked in an oven through which air is circulated during the drying. The trays all dry at relatively the same rate, and when the particles are all dry, the oven is shut off, and the trays of dried particles are then removed. At this stage, the hazard is the greatest, and is considerably increased by the large volume of dry explosive particles in this dangerous condition, virtually the entire capacity of the drying oven. Since for reasons of economy drying ovens are usually quite large, the hazard is that much greater. Any explosions that may occur nearly always involve loss of life or serious injury to the personnel, because removal of the trays from the oven is necessarily a manual operation. Since human failure and accidents are more or less inevi- 3,456,357 Patented July 22, 1969 ice table, despite all safety precautions, most explosive manufacturers have to expect fatalities from time to time, arising from explosions at the dryers.

Considerable effort has been made to develop drying apparatus that does not entail this hazard, but with no success. As a result, a batch-type drying operation using tray dryers is virtually the standard throughout the industry, in this country and elsewhere in the world.

In accordance with the instant invention, drying apparatus is provided that makes it possible to dry nitrostarch, nitrocellulose and similar particulate explosive sensitizers, as Well as other hazardous chemicals, in a continuous manner that can be entirely automated. Since the operation of the dryer is continuous, only small quantities of the hazardous dry explosive are present in the dryer at any given time. The amount of dry explosive can thus be reduced to the point where even if explosion occurs, no serious damage will result, because of the small quantity of explosive. Moreover, the dry explosive can be loaded into containers and transported away from the dryer automatically, which means that no operator need be stationed at or near the dryer, or even in the dryer building.

Safety is also ensured by moving the particles of the explosive through the dryer by a vibratory, tumbling movement, and by fully enclosing that portion of the dryer through which the explosive passes, so that no particles of explosive, wet or dry, can escape, vibrating the entire enclosure to obtain such tumbling movement, so that there are no moving parts in which explosive particles can be caught, With resultant friction, heating, and possible danger of an explosion,

The dryer has the further feature that air or other drying gas can be passed over, along and across the surface of the explosive particles, and not directly through a bed of the particles, from one side to the other, minimizing the danger of entrainment of the explosive particles in the drying gas, and avoiding the high gas pressures that might otherwise be necessary to force the gas through the bed.

Also the dryer can -be heated externally, to heat the particles therewithin, `and either replace or supplement the drying effect of the drying gas.

The drying apparatus in accordance with the invention comprises, in combination, an elongated drying enclosure through which the particles of explosive or other hazardous chemical are passed; means for introducing Wet particulate explosive at one end of the enclosure to form a bed of such particles Within the enclosure; means for withdrawing dry particulate explosive at the other end of the enclosure; means externally of the enclosure for Vibrating the entire enclosure in a generally forward and generally upward direction, so as to impart a tumbling forward movement to a bed of the explosive particles within the enclosure; means (optional) for iiowing drying gas through the enclosure, introducing and withdrawing the drying gas from the enclosure at a point above the explosive particles, so as to pass the gas over but not through a `bed of the particles Within the enclosure; and/ or means (optional) for heating the gas and/ or the enclosure (preferably from beneath) to a temperature at which drying occurs, if necessary.

The apparatus can lbe so operated that Wet explosive particles can be introduced into the enclosure continuously, and dry explosive particles withdrawn continuously, and therefore optionally features means for continuously and automatically collecting, batchwise, dry explosive emerging from the elongated enclosure, and removing such batches of dry explosive from the immediate vicinity of the dryer for safety purposes. As a further optional feature, the apparatus also includes a tire, light and/erw heat sensitive deluge system for quenching any fire or excessive generation of heat (such as a faulty heating 3 system) that may occur in any portion of the drying enclosure.

The invention also provides a process for drying particulate explosives, such as nitrostarch and nitrocellulose, as well as other hazardous chemicals, Iwhich :comprises continuously introducing such material in wet particulate form at one end of an elongated heating zone, imparting a vibratory forward `ad upward tumbling movement to such material lwhile in the zone, so as to move the material progressively from one end of the Zone to another end, while heating the material at -an elevated temperature, if necessary, and optionally, but preferably, while flowing a drying gas through the zone over the vibrating tumbling particulate material, to entrain moisture from the particulate material in the gas, and remove 'such moisture from the zone, withdrawing moisturecontaining gas from the zone, continuously withdrawing dry particulate material from the end of the zone, and continuously removing the dry particulate material, desirafbly, as rapidly as possible, to a point safely distant from the drying zone.

As a further feature, the invention provides va continuous process in which the drying gases are washed or scrubbed with water to remove any particulate explosive material that may be entrained therein, returning any entrained wet particulate material thus recovered :for recycling, drying the scrubbed drying gas, and recycling the drying gas, if desired, and also recovering and recycling the wash Water after separation of the particulate explosive material therefrom.

The process and apparatus are especially advantageous for the drying of hazardous materials because of the tumbling action. The particles are elevated and air or gas contact increased, while at the same time they are lifted up, out of contact with the enclosure. Thus, if the enclosure is heated, the particles can cool somewhat, while bathed in a stream of drying gas. They then drop back into contact with the enclosure, and the cycle is repeated. In this way, the particles are alternately heated and cooled, while the gas carries away the moisture that is liberated. Also, any static charge the particles acquire lwhile aloft -and in motion is dissipated whenever the particles are in contact with the enclosure, increasing the safety, due to minimizing the possibility of spark discharge of static accumulation.

The process and apparatus can be used to remove any volatile liquid as vapor from particulate explosives and other hazardous chemicals. The removal of Water as vapor is the principal objective, in most cases, but volatile solvents and other organic liquids, when present, With or without Water, is also achieved, using the same techniques. Consequently, the term drying is u-sed herein to refer to removal of volatile liquids as a class, and is not limited to the removal of water. 1

As the drying gas, air is preferred. If the material being dried is 4air-or oxygen-sensitive, an inert gas can be used, such as nitrogen, carbon dioxide, argon, helium, or krypton. The drying gas can be stripped of water or other liquid being removed, and recirculated, if economics require it. To reduce any static charge on the explosive being dried, the drying gas may be ionized. The solvent or other organic liquid can also be recovered or recirculated, as for instance, in the drying of smokeless powder, or gelatin dynamites, or nitrocellulose.

The apparatus and process of the invention are applicable to any hazardous flammable solid particulate material. They find their best application to the drying of explosive sensitizers that can be detonated when dry, or that can turn over 'from -burning to detonation when dry, such as nitrostarch, nitrocellulose, I-IMX, pentaerythritol tetranitrate, smokeless powder, carbine ball powder, lead azide, mercury fulminate, and 80-20 mixture of mercury fulminate and potassium chlorate, lead styphnate, tetracene, a mixture of potassium chlorate and lead sulfocyanate, picric acid, lead picrate, ammonium picrate, lead trinitro resorcinate, n-nitrophenyl diazonium perchlorate, nitrogen sulfide, copper acetylide, fulminating gold, nitroso guanidine, mercury tartrate, mercury oxalate, silver tartrate, silver oxalate, and mixtures of potassium chlorate and red phosphorus, mannitol hexanitr-ate, sorbitol hexanitrate, trinitrotoluene, pentolite, cyclonite I(RDX, cyclotrimethylene trinitramine), Composition B (a mixture `of up to 60% RDX, up to 40% TNT, and 1 to 4% wax), cyclotol (Composition B without the wax) Amatol, Sodatol, tetryl and tetryl pentolite. The process and apparatus are yalso applicable to hazardous chemicals such as ammonium nitrate, yammonium chlorate, potassium chlorate, sodium chlorate, and potassium perchlorate, sodium perchlorate, and ammonium perchlorate.

A preferred embodiment of dryer in `accodance with the invention is shown in the drawings, -in which:

FIGURE l represents a plan or top view, partly in section, of a drying apparatus in accordance with the invention.

FIGURE 2 represents a side view, in elevation and with parts broken away and in section, of the drying apparatus of FIGURE l.

FIGURE 3 represents a cross-sectional and enlarged detail view of the elongated enclosure of the dryer of FIGURES 1 and 2, taken along the line 3-3 of FIG- URE 1, and looking in the direction of the arrows.

FIGURE 4 represents a detailed side view, in elevation, and partly in section, of feed hoppers and a conveyor for feeding wet particulate explosive material to the wet end of the 4dryer of FIGURE 1.

FIGURE 5 is a cross-sectional view of the feed system of FIGURE 4, taken along the line 5-5 and looking in the direction of the arrows.

FIGURE 6 is a detailed view, in side elevation, of the equipment for vibrating the elongated enclosure of the dryer of FIGURES 1 and 2.

FIGURE 7 is a plan view of the automated dry particulate explosive delivery and batch collection system at the dry end of the dryer of FIGURES l and 2.

FIGURE 8 is an isometric view of another type of enclosure for which the vibratory motion is imparted by a pulsating flow of the heating iiuid through the enclosure.

FIGURE 9 is a graph of percent moisture against the length of the dryer enclosure of FIGURES 1 to 7, showing the moisture content of a typical material being dried at nine stations along the enclosure.

The dryer shown in FIGURES l to 7, inclusive, comprises an elongated dryer enclosure 1, that is housed in and extends from one end to another of the dryer tunnel 2, and projects slightly beyond it at each end. At the wet end 3, the enclosure 1 projects into the chamber 4 0f building 5. The dry end 6 0f the enclosure 1 terminates in a spout 9 that projects into the chamber 10 of building 11. Port 7 provides access to the enclosure 1 at the top, for feed of wet particulate explosive, and hopper 8 is provided at the dry end for delivery of dry explosive to the collection system in chamber 10.

Along the top of the dryer enclosure 1 (as is best seen in FIGURE 1) are a plurality of drying gas inlets 15 interspersed between gas outlets 16, each type being uniformly spaced (or nonuniformly spaced, if desired) from the dry end to the wet end of the dryer, and interspersed between these ports are a plurality of inspection ports 17.

Starting from about half way down the enclosure t0 the dry end and in chamber 10 are placed four lire deluge tanks 18 which form a part of the fire quenching system. These are individually and operatively connected to a corresponding number of ame detectors 19, designed to sense any unusual increase in light level within the tunnel 2 in which the enclosure 1 is disposed. The sensors can also be designed to detect any unusually high temperature above a predetermined temperature high threshold. Thermocouples, infrared and ultraviolet detectors, ionization differential detectors, thermistors, and pressure-sensitive paints, can also be used as sensors. Since the entire closure, housing and building interior are dark, greater sensitivity is possible in a light detection system.

The drying enclosure 1 (as is best seen in FIGURE 3), is made of two sections, an upper section 20, in this case formed of aluminum, that is generally U-shaped in crosssection, and terminates with a flange 22, and a lower section 21 that is roughly trough-shaped in cross-section, with liaring sides, and that in this case is made of stainless steel, the sides also terminating in flanges 23. The flanges 22, 23 are bolted together, with a gasket 24 therebetween, so that the enclosure 1 is effectively sealed from end to end.

Directly beneath the lower section 21 of the enclosure 1 is a plate heating coil 25, whose channels run horizontally to and crosswise of the bottom of the lower section 21. These coils are connected at an end to a water inlet line 26 and at the other end to an outlet line 27, through which heating water is circulated, for heating the enclosure. The coils can be divided into sections, for better heat control of successive sections of the enclosure 1. The water supply system is carried on supports 46, and iS circulated through a heating system (not shown) in another building.

The vibrating or rocking mechanism 30 for the enclosure 1 is external of the enclosure, and vibrates the entire enclosure as a single unit, and as is seen from FIGURE 6 is otherwise conventional. The entire mechanism is enclosed in a protective shroud 32, attached to lower section 21 and to base 42 by flange arrangements comprising flanges 43 and plates 43a. The shroud is air-purged, by supplying air therewithin, maintaining a constant outward ow at any leaks therein. The lower portion 21 of the enclosure 1 is operatively supported on and connected to the vibrating mechanism system by way of a plurality of lugs or struts 28, 29. Alternate lugs 28 are attached to fiber glass leaf springs 31. The top end of each spring 31 is attached to the lugs 28, and the lower end is attached to the base 42, via lug 45.

The vibrational forward and upward movement is imparted to the enclosure 1 at the lugs 29. Shock absorbers 40 at their top end are attached to the lug 29 and at their lower end the shock absorbers are attached to one end of a lever arm 39. The other end of the lever arm 39 is attached to the connecting arm bushing 37 at one end 0f the drive arm 35. The other end of the drive arm is mounted to and moves with the eccentric shaft 34, which moves with sheave 36. Rotating the sheave 36 is a drive belt 44, which is operatively connected to a drive sheave 33 operated by a motor, not shown. A pan bushing 38 connects the end of the lever arm 39 to the other end of the lug 29. The motor, located outside the building to prevent overheating and thus avoid danger of re, is connected to drive sheave 33 by a drive shaft extending through the wall of the building.

It will be evident that operation of the drive belt by the motor 33 moves the eccentric 34, and this in turn reciprocates the drive arm 35, imparting the desired vibrational to and fro movement, first upward and forward, then downward and backward, to the enclosure 1.

The function of the shock absorber 40 is to slowly change its length, thereby compensating for change in vertical elevation of the enclosure between no load and full load, in order to automatically keep the entire vibrating weight of the enclosure 1 and the conveyed explosive material on the springs 31, and never on the drive shaft and bearings. It is so designed that at normal operating speeds, the valves do not lift, and the vibration of the enclosure l itself causes no movement in the shock absorber. Therefore, the operating amplitude remains fixed, so safe limits are not exceeded, and dampening under load does not take place. During the stopping cycle, when the drive and spring forces are opposed, the shock absorber simply stretches and collapses several times, so that the motion is actually compromised rather than overpowered. The pan connector bushing and the drive arm connection bushing are all set in a leverage ratio through a lever to the shock absorber. The pan attachment bushing and the drive arm bushing can therefore move with respect to each other, whenever the shock absorber changes its length. In addition, the supporting springs are uniformly dispersed throughout the length of the enclosure 1, and are actually linear fly wheels. Thus, the energy that vibrates the pan is stored on short centers, and returned to the system in such a manner as to uniformly distribute the stresses over the entire length of the enclosure. Once motion has been initiated, these springs actually can be considered not only the supports but also the driving means for the enclosure 1, and the eccentric drive merely becomes an exciter, to make up the internal friction loss, which is extremely small.

As material flows long the enclosure 1, the enclosure 1 can actually settle under the weight of the material that is being conveyed and dried, and automatically floats to its neutral position on the spring system. Thus, not only the vibrating weight of the equipment itself, but the weight of the material and the impact from the material are supported or absorbed by the spring system, and are prevented from reaching the drive shaft and bearings. Thus, the system is well designed to impel the explosive material forward without shock, and therefore with utmost safety.

'Drying gas, in this case, air, is circulated lengthwise of the elongated enclosure 1 via the system of inlet ports 15 and outlet ports 16 along the top of the container.

The main gas inlet duct 56 leading from the heating equipment whence heated gas is fed by blowers (not shown) enters a plenum chamber 60 beneath the roof 59 of the dryer building, which extends the entire length of the tunnel 2, over the elongated dryer enclosure 1. Ports 57 are provided at spaced intervals in the roof of the tunnel 2 along the plenum chamber 60. These ports are arranged with covers 61, which can partially or entirely close off each port 57, for regulation of the volume of gas or air entering the tunnel 2 through the port. The gas thus enters the tunnel into the space 1A surrounding the elongated dryer enclosure 1, from which it can enter the elongated enclosure 1 itself by way of the inlet ports 15. It then circulates over the material within the elongated enclosure 1, in a countercurrent and in a concurrent flow direction from each port 15, as indicated by the arrows in FIGURE 2, to the nearest outlet port 16, so that both concurrent and countercurrent flow is obtained during the drying process. If desired, all of the ow can be countercurrent, or all of the ow can be concurrent, simply by adjusting the number and location of the outlet ports 16, and by appropriate battling, but a combination of the two is of assistance in promoting drying.

Any conventional dehumidifying system can be provided for preparing the gas for drying, so as to reduce the humidity or moisture level to the minimum desired, and provide heating, if desired.

The drying gas within the enclosure 1 emerges via the outlet ports 16. The construction of the gas outlet ports 16 and connecting lines is best seen in FIGURE 3. To the port 16. is tted a exible union 52, allowing for movement of the union according to vibrational movement of the port with the elongated enclosure 1. A suitable material is an electrically conductive flexible plastic or rubber. To the iiexible union is connected the flared outlet gas conduit 53, which connects at a T- joint to the horizontal header line 54. For convenience, the line 54 extends all the way from one side to the other, across the tunnel enclosure 2, but it is connected to a gas line running to the central gas recovery systern only at the side 55.

At one end of the line 54 is provided a spray jet 47 for wash-down of the header, cleaning out any particles that may accumulate there. The wash water passes out via line 53 and aspirator venturi 73. These are operated only when the apparatus is shut down, and being cleaned out.

The arrangement for recovering fines of explosives material that may be entrained in the drying gas also 1s best seen in FIGURE 3. Wet gas emerging from the tunnel 2 via line 54 enters the aspirator venturi 73 to which water is supplied at any desired temperature via line 72 and nozzle 71. The aspirator 73 draws Wet gas from the line 54 so that gas is both blown into the dryer enclosure 1 and sucked out, with the result that the air pressure within the enclosure 1 normally is slightly below atmospheric pressure. Both water and gas pass downwardly through the aspirator venturi 73, entering the separating chamber 74. The water and gas are well mixed in the aspirator venturi, and any particulate explosive material that may be entrained in the gas is washed or scrubbed out in the course of this mixing, and entrained in the water. The now particle-free gas is withdrawn via the exhaust line 75, while the water containing the solid material washed out from the gas is drawn off via the exit line 76. From this water, since the explosive is now relatively insensitive, because it is wet, suspended material can be separated by settling, filtration or centrifuging, and then returned to the drying system, if necessary, after agglomeration. The water can then be recovered, and recirculated through the nozzle 71.

The supply system for feeding wet particulate explosive material to the wet end of the elongated dry enclosure 1 is best seen in FIGURE 4. This system comprises a feed hopper 80, into which the wet particulate material, such as wet nitrostarch, can be dumped manually, batchwise, or continuously, and automatically, as desired. The wet material contains a sufficient amount of water to render it insensitive, so that this operation is nonhazardous. From the hopper 80, the material is fed by gravity onto the endless conveyor belt 81. The conveyor has a longitudinally and cross-ribbed surface, with spaced longitudinal and cross ribs 82, and is operated in a clockwise direction with the upper surface passing to the right over roller 83, and then to the left beneath to the drive roller 84, thus in a continuous fashion carrying off the particulate material 85 fed to it from the hopper S0. The ribs assist in control of feed. The space between the ribs determines the feed volume. A rubber plate or doctor blade 86 at the exit end of the hopper, adjustable in height above the belt 81, controls the depth and volume of particulate material on the belt, and therefore, with the speed of travel of the belt, and the ribs spacing, the rate of feed of the particulate material to the dryer.

Directly beneath the roller 83 is a second feed hopper 88, within which is disposed a bristle brush 89, with bristles 92 of natural fiber or synthetic fiber, that is a nonfriction and static charge-dissipating material, mounted at the lower end of the rotatable drive shaft 91. The bristles 92 brush the sides 94 of the hopper 88, to feed particulate explosive material through the hopper. At the lower end of the hopper 88 is a wide mesh screen 95 from which the particulate material is fed directly into the entry port 7 at the wet end 3 of the elongated enclosure 1. The mesh size of the screen controls the particle size of the material fed to the dryer to a predetermined maximum. The rotational speed of the brush is adjustable by control of the rotational speed of the shaft, so as to control rate of feed through the screen 95. The particulate material enters the enclosure 1 via the entry port 7, best vseen in FIGURE 1, disposed directly beneath the screen 95, whence the particulate material is moved forward through the enclosure by vibrational movement.

The dry explosive material collection system at the dry end 6 of the enclosure 1 is best seen in FIGURE 7. This is designed for automatic operation, so that no operator need be in the immediate vicinity of the dry end of the enclosure.

Enclosing the spout 9 at the dry end of the enclosure 1 is a feed hopper 8 arranged to feed dry material from the enclosure directly into a canister 13. The canister 13 is supported on a turntable 14, on which is mounted a canister frame 48, that is fixed to and therefore rotatable with the turntable 14. This frame has four pairs of arms 49, dividing the turntable into four quadrants, and located to embrace canisters on each quadrant, so that four canisters are loaded on and moved with the frame on the turntable.

A canister-carrying car 77 operates from one end to another of a track 78, terminating at one end at the turntable, and leading to a vdistant point A. The car is operated from one end of the track to the other by a cable 96 attached to a piston 97, which in turn moves in air cylinder 98. Reciprocation of the piston pulls the cable 96, and with the cable the car 77, from one end of the track to the other. At the far end A of the track, the canister can be handled manually by an operator, and moved to storage or shipment, as desired.

The track is mounted over a water-filled trough 99, so that any dry explosive that happens to spill from the canister accidentally or otherwise is immediately desensitized. Similarly, the turntable 14 can be operated in a water-filled trough 100 for the same reason, if desired.

The turntable 14 and the canister frame 48 are each mounted on a vertical shaft 101 which rides in safety bearings at the ceiling and fioor of the chamber. The fioor bearing 102 which is of porous bronze (best seen in FIGURE 2) is held in the trough 103, which is filled with water, completely immersing the bearing 102, and the bearing end of the shaft 101. This provides lubrication for the shaft, and it also prevents any contact of sensitive dry explosive with the rotating shaft parts.

The upper bearing 105 is also separated from the chamber by a water seal. The shaft at a portion near the ceiling supports a trough 110, which is filled with water. Dependent from the ceiling is a tube 111, the lower end of which is emerged in the trough. Thus, this end is immersed in water, and no particulate explosive that may happen to become entrained in the air in the chamber can pass beyond this point, so as to reach the bearings in which the shaft rotates, or the motor and drive mechanism for the shaft.

If desired, a closed circuit television system can -be provided in the chamber, so that an operator at position A can view the operation of the enclosure and the filling of the canister. Mechanism can be provided for automatically closing the bottom of the hopper when a canister is full, after which the turntable -can be rotated through 90 by the operator, so the canister is brought to and placed upon a car, and removed from the chamber, and a fresh canister immediately substituted, already in position as shown on the turntable in the next bay of the canister frame. In this way, a semicontinuous batchwise filling ofthe canisters can ybe provided for, so as to correspond in delivery volume to the drying volume capacity of the dryer.

Alternatively, mechanism can be provided, so that the operator will manually move the canister when it is full. An operator controlled mechanism can also be included, to override any automatic filling mechanism.

The operation of the dryer is as follows:

Porous particulate explosive material 85, such as nitrostarch, nitrocellulose or smokeless powder, is loaded into the hopper 30 of the supply feeding system, whence it is fed to the belt 81, which carries it to the dryer enclosure feed hopper 88. The brush 89 wipes the material through the screen 95 into the drying enclosure 1 via the delivery port 7. In the case of nitrostarch, the moisture content of the nitrostarch at this stage is suitably within the range from 10 to 50% by weight, but usually from 15 to 30% by weight. The brush feeder ensures that there will be no hang-up of explosive in the hopper, and the screen is of a mesh size that ensures that the explosive delivered to the drying enclosure is of an appropriate particle size for optimum drying rate. This is from 2 to 5 mesh in the case of nitrostarch.

The particulate wet material, for example, nitrostarch, is fed into the elongated enclosure 1, where it forms a bed 1A; to 2/8 inch deep. The particles in the bed at once acquire a tumbling forward motion by the vibratory motion so that they are impelled towards the dry end 6 of the enclosure while air is passed over the bed at a temperature of from 140 to 160 F. and a flow rate of 150 to 200 cu. ft./ min. The water circulated through the heating coils 25 beneath the enclosure 1 is kept at from 140 to 160 F. The rate of travel of the tumbling bed of nitrostarch particles is within the range from 5 to l0 feet per minute, so that the total travel time from the wet end 3 to the dry end 6 of the enclosure 1 is about ten to twenty minutes. Because the particles are continually tumbling and so changing the face they offer to the air passed over the bed, the nitrostarch is dried rapidly in the course of its travel through the enclosure, and when it emerges at the dry end 6 of the dryer has a moisture content below 1%. There it is loaded into canisters 13. The canisters when full are rotated through 90 with the turntable 14 to the car 77, and then brought by the car to position A, where the operator then loads the canister into storage.

The drying system shown in the drawing with a dryer enclosure 100 feet x 11/2 feet x 21/2 feet has a capacity of 150 lbs. nitrostarch and is capable of drying nitrostarch having a moisture content of from 15 to 20% at a rate of from 150 to 200 pounds per hour, so that one dryer is quite adequate for drying the daily nitrostarch production of a 16 ton per day nitrostarch plant.

It will be evident that by suitable design modification, the drying system can be made to cope with any desired production volume, for any type of particulate explosive. However, it is not -usually desirable to design the dryer enclosure for a capacity that requires more than 250 pounds of nitrostarch (both wet and dry) to be present in the dryer enclousure 1 at any given time, for safety reasons. Where production requires it, it is better to install two dryer enclosures of low capacity, rather than a single dryer of a larger capacity. Even at a 250 lbs. capacity, no more than 125 pounds of dry (and sensitive) nitrostarch is present at any given time.

In the -unlikely event of a fire, the deluge system provided by the invention serves to quench it in almost all cases before damage is done or an explosion can occur. The ilame or heat detectors 19 are designed to sense any amount of light that is suticiently above normal room light so as to prevent a deluge on a bright day, but far enough below the light emitted when the explosive has ignited or is burning to ensure operation of the deluge system before detonation can occur. The flame detectors 19 are electrically connected by wires 19a to an amplier (not shown), and this in turn is electrically connected to a blasting cap. The flame detectors are cadmium sulfide cells which upon sensing a certain minimum level of light will generate an electric current of predetermined magnitude that is fed to the amplifier. Selenium or lead sulfide cells also can -be used. The amplier in turn at a predetermined minimum current level amplifies the current suiciently to open a switch, whereupon current passes to an electric blasting cap and detonates the cap. This in turn ruptures a diaphragm or opens the valve of the nearest deluge tanks, and at once discharges a sufficient volume of water throughout the chamber and elongated enclosure to quench any iire that may exist.

It will be appreciated that numerous modications can be made in the dryer shown above. In place of the vibratory system shown, any conventional vibration mechanism can be used for vibrating the enclosure 1. The system that is shown is preferred, because it ensures a safe propulsion of the explosive material from one end of the dryer enclosure 1 to the other, and because it is also suitable for vibrating the entire enclosure, instead of just a portion thereof. The latter alternative would involve moving parts within a stationary enclosure, which would at once present a safety hazard.

Another form of vibration mechanism is shown in FIG- URE 8, in which the lower section 121 of enclosure 1 is vibrated by a pulsed tlow of water to the heating platecoil 125. The enclosure is similar to that shown in FIG- URES 1 to 7, and is similarly supported. The drying enclosure 1 is made of two sections, an upper section 120, that is generally U-shaped in cross-section, and terminates with a flange 122, and a lower section 121 that is roughly trough-shaped in cross-section, with Haring sides, the sides also terminating in anges 123. The anges 122, 123 are bolted together, with a gasket 124 therebetween, so that the enclosure 1 is effectively sealed from end to end. However, the vibrating and rocking mechanism 30, as shown in FIGURE 3, and the drive motor (not shown) is replaced by a pulsed fluid vibration mechanism operated in this case by a peristaltic pump 133. A piston pump, or a sigma pump, can be used, or any other type of pump capable of delivering a pulsating flow or a stop-and-go tiow of iiuid, or a combination of a pump and intermittent opening and closing valves can also be used. The pump 133 is in the water inlet line 126, and supplies a pulsating ow of heating water (or other heating fluid, such as an oil) to the plate coil 125. A throttling valve 127 in the line 126 aids in controlling the amplitude of the pulsations of the pump 133. The reservoir 130 is for heating and temperature control, and is in the recycle line 132. The pulsation rate in this case is controlled by the speed of the pump and by the number of digitated members on the pump. The pulsations in the flow are communicated to and vibrate the enclosure 1, the lower section 121 of which is supported only on the leaf springs 131.

The design of the elongated enclosure will, of course, be adapted to meet the required drying conditions, and the type of particulate material that is to be dried. The enclosure must be long enough and vibrated at a throw and a rate such that the wet material is fully dried by the time it reaches the dry end of the enclosure, while the volume of the enclosure is such that the desired drying capacity is provided for. While the enclosure shown is rectangular in cross-section, it can, of course, be round, square, elliptical, polygonal, or any other shape, as desired.

The drying enclosure shown is disposed horizontally, but it also could be inclined slightly towards the dry end, so as to expedite the flow of material towards the dry end. The general vibratory movement or throw is upward and forward. The apparatus shown is designed to operate at a throw of from 1/s to 1/2 inch with a forward and upward movement at an angle of 45 to the horizontal, but it is apparent that this can be modied as desired. The throw can be increased to two inches or more, and can be as little as 1%,2 inch, while the angle can be Within the range from 30 to 60 to the horizontal, and in some cases even as much as from l5 to 75.

The drying enclosure can be made of any suitable material. The material in contact with the particulate material to be dried must, of course, be inert to that material. It should also be electrically conducting, so as to avoid the build-up of static charges. Consequently, metallic materials are preferred, and stainless steel is particularly desirable for explosives, because it is inert to most explosives. The upper portion of the enclosure need not be inert since it does not contact the material, and aluminum or other materials can serve. Plastic materials also are useful, particularly plastic materials which are electrically conducting. Polyethylene, polypropylene, polystyrene, synthetic rubber, nylon, polyvinyl chloride, urea-formaldehyde, phenol formaldehyde, melamine formaldehyde, polyester, polycarbonate, polyacrylonitrile, acrylonitrilebutadiene-styrene, and polyformaldehyde resins are quite satisfactory.

It is desirable to operate the dryer with a ow of air into the elongated enclosure 1 from the wet and dry ends (shown by the arrows at 3 and 6 and FIGURE 2) so as to ensure that the material that may be entrained in the air in the rooms into which the enclosure projects will be eventually drawn into the dryer, thus preventing a possible safety hazard. This is provided for in the apparatus shown by the aspirators 71.

The dryer enclosure should be operated with a rather thin bed of particulate material at its bottom. In the usual case, the bed is within the range from about 1/s to about 34; inch deep, although in the case of some materials having a low moisture content, a depth of as high as 5%; of an inch or even one inch can be tolerated, particularly when the particles are rather large. In general, the larger the particle, the greater the depth of bed, and the lower the moisture content of the particle, the greater the depth of bed. A thin bed is preferred, because of the greater of the enclosure 1 was halted, another canister substituted, and vibration resumed, so as to maintain a semicontinuous delivery of dry nitrostarch from the enclosure. The filled canisters were brought to point A by the operator of the car, and sent to storage.

Under these conditions, the dryer was operated for a three month period, at a daily production rate of 4800 pounds of dry nitrostarch, without any mishaps whatsoever. At no time did the amount of dry nitrostarch in the drying enclosure exceed 75 pounds by weight, and the total amount of nitrostarch held in the enclosure at any given time did not exceed 150 pounds.

For purposes of comparison, samplings were made of the nitrostarch being dried on successive days, at each of nine stations simultaneously, via the inspection ports 17, and the samples analyzed for percent H2O. The stations were spaced along the enclosure from the dry end to wet end. The following data were taken:

TAB LE Nitrostarch Distance in Time from Percent sample station feet from dry end 1u No. dry end minutes Day No. I Day No. II Day No. III Average 0 0 20. 86 19. 65 21. 75 20. 753 3 18.06 17. 18 18. 76 18. 00 22 7 18. 42 14. 97 16. 16 16. 516 33 0. 5 15. 22 12. 24 9. 02 12. 46 44 13. 5 11.56 7. 07 8.57 9.066 55 17. 5 11. 13 5. 66 7.09 7. 96 6G 20 7. 58 3. 80 7. 04 6. 14 78 24 3. 99 2. 57 5. 96 4. 173 92 27. 5 2. 86 2. 64 3. 17 2. 89 No. IX 100 3() 2. 36 1. 07 2. 42 1. 95

urve in Fig. 9 I II III Average rapidity of drying, and because the tendency of an explosive to turn over from burning to detonation is reduced in the case of a thin bed. Therefore, usually, if a choice can be had between a deep bed and a thin bed, as compared to a dryer enclosure of greater or shorter length, a thin bed in a longer dryer would definitely be preferred to a thick bed in a shorter dryer.

The apparatus shown in FIGURES 1 to 7 and 8 is suitable for the drying of any particulate explosive sensitizer, and is particularly suitable for nitrostarch, nitrocellulose and smokeless powder.

The following examples in the opinion of the inventor represent preferred embodiments of the invention.

EXAMPLE 1 Nitrostarch having a nitrogen content of 12.75% was prepared by the nitration of corn starch, using .aqueous nitric ac'id containing 38% nitric acid and 63% sulfuric acid, in the ratio of 800 lbs. of acid and 200 lbs. oi starch. The nitrostarch was purified by cold water washings, and had a moisture content of 25% as prepared. The wet nitrostarch was dried on the screen from the nitrator to a moisture content of about 20%, and then brought to the hopper of the apparatus shown in FIGURE 1, where it was loaded at room temperature onto the conveyor belt and fed through the brush feed hopper and a 2 mesh screen into the wet end port 7 of drying enclosure 1. The temperature of the drying enclosure was kept at from 140 to 160 F., and the temperature of the drying air was kept in the same range. The air flow through the drying enclosure was approximately 200 cubic feet per minute.

The Wet nitrostarch was loaded into the enclosure in a suticient amount to form a bed approximately Ms inch deep, and the vibration system of the enclosure was operated at a throw of BAG inch, at a frequency of 595 throws per minute. The travel time for the nitrostarch from the wet to the dry end of the bed was approximately minutes, and the nitrostarch emerging at the dry end of the bed had a moisture content of about 1% or 2%, and a nitrogen content of 12.75%.

The nitrostarch was loaded into canisters at the dry end of the bed. When a canister was filled, the vibration The above data is graphed in FIGURE 9. The curves show a remarkable uniformity in the drying operation and the drying rate.

The dry nitrostarch product that was obtained was comparable vin every way with a conventional tray-dried product. There was no evidence of scorching or decomposition of the nitrostarch particles, and they were as stable in storage as the tray-dried material, and showed the same properties when formulated into explosive compositions of the usual type.

For comparison, the dryer enclosure was operated under the same conditions, but while stationary, i.e., without vibrating it. The drying time to reach a 1% moisture content was two hours and thirty-five minutes. This shows how much the Vibrational, tumbling movement of the particles improves the drying operation.

EXAMPLE 2 Nitrocellulose having a nitrogen `content of 13.25% was prepared by the nitration of cotton linters, using an aqueous (9% H2O) mixture of 67% sulfuric acid (sp. gr. 1.84) and 24% nitric acid (sp. gr. 1.42), and washed thoroughly with water, including a boiling wash -with slightly acidilied water. The nitrocellulose was pulped, poached, screened, and wrung to a moisture content of 26-28%. The wet nitrocellulose was then brought to the hopper of the apparatus shown in FIGURE 1, and at room temperature was loaded onto the conveyor belt and fed through the brush feed hopper and the screen, a 2 mesh screen, into the wet end of drying enclosure 1. The temperature of the drying enclosure was kept at from to 160 F., and the temperature of the drying air was kept in the same range. The rate of ow of air into the drying enclosure was approximately 75 cubic feet per minute.

The wet nitrocellulose was loaded into the enclosure in a sufficient amount to form a bed approximately 1A; inch deep, and the enclosure was operated at a throw of 1A: inch at a frequency of 800 throws per minute. The travel time for the nitrocellulose from the wet to the dry end of the bed was approximately 30 minutes, and the nitrocellulose emerging at the dry end of the bed had a 13 moisture content of 2%, and a nitrogen content of The nitrocellulose was loaded into canisters at the dry end of the bed. When a canister was lled, the vibration'of the enclosure was halted, another canister substituted, and the vibration resumed, so as to maintain a semicontinuous delivery of dry nitrocellulose from the enclosure. The filled cans were brought to point A by the operator of the car, and the lled canisters were sent to storage.

The dry nitrocellulose product that was obtained was comparable in every Way with a conventional tray-dried product. There was no evidence of scorching or decomposition of the nitrocellulose particles, and they Were aS stable in storage as the tray-dried material, and showed the same properties when formulated into explosive compositions of the usual type.

EXAMPLE 3 Smokeless powder was prepared having the following formulation:

Nitrocellulose (percent N in nitrocellulose 13.15) 84.00

The batch was made up to 200 pounds of the ingredients noted above, 100 pounds of water was added, and dye, and the mix milled in a wheel mill, put through a mechanical rubber to break up thev lumps, screened through a 2 mesh sieve, and hardened with acetone and alcohol. The solvent-and-water-wet particulate material (liquid content 18.5%) was then brought to the hopper of the apparatus shown in FIGURE 1. Then, at room temperature, it was loaded onto the conveyor belt and fed through the brush feed hopper and the screen, a 2 mesh screen, into the wet end of drying enclosure 1. The temperature of the drying enclosure Was kept at 160 F., and the temperature of the drying air was 115 F. The rate of ow of air into the drying enclosure was approximately 250 cubic feet per minute.

The wet smokeless powder was loaded into the enclosure in a sufficient amount to form a bed approximately 3/8 inch deep, and the enclosure was operated at a throw of 1A inch and a frequency of 600 throws per minute. The travel time for the smokeles powder from the wet to the dry end of the bed was approximately 20 minutes, and the smokeless powder emerging at the dry end of the bed had a moisture content of 0.53%, and was solvent-free.

The smokeless powder was loaded into canisters at the dry end of the bed. When a canister was filled, the enclosure was stopped, another canister substituted, and the enclosure restarted, so as to maintain a semicontinuous delivery of dry smokeless powder from the enclosure. The lled canisters were brought to point A by the operator of the car, and sent to storage.

The dryer gave a daily production rate of 10,000 pounds of dry smokeless powder, without any mishaps whatsoever. At no time did the amount of dry smokeless powder in the drying enclosure exceed 75 pounds by weight, and the total amount of dry smokeless powder present in the enclosure at any given time did not exceed 150 pounds.

The dry smokeless powder product that was obtained was comparable in every way with a conventional rotating cylinder-dried product. There was no evidence of scorching or decomposition of the nitrocellulose in the smokeless powder particles, and they were as stable in storage as the cylinder dried material, and showed the same deagrating properties.

EXAMPLE 4 Wet granular 20 mesh pentolite, 50:50 TNT:PETN, having a moisture content of 9%, was brought to the hopper of the apparatus shown in FIGURE 1, where it was loaded at room temperature onto the conveyor belt and fed through the brush feed hopper and a 2 mesh screen into the wet end port 7 of drying enclosure 1. The temperature of the drying enclosure was kept at 160 F., and the temperature of the drying air was kept at F. The air flow through the drying enclosure was approximately 200 cubic feet per minute.

The wet pentolite was loaded into the enclosure in a suicient amount to form a bed approximately 1A inch deep, and the vibration system of the enclosure was operated at a throw of 46 inch, at a frequency of 700- 800 throws per minute. The travel time from the wet to the dry end of the bed was approximately 30 minutes, and the pentolite emerging at the dry end of the bed had a moisture content of about 1%.

EXAMPLE 5 Pentaerythritol tetranitrate having a moisture content of 8% was brought to the hopper of the apparatus shown in FIGURE 1, and at room temperature was loaded onto the conveyor belt and fed through a 2 mesh screen (the brush feed hopper was removed) into the wet end of drying enclosure 1. The temperature of the drying enclosure was kept at from to 160 F., and the temperature of the drying air was kept at 125 F. The rate of ow of air into the drying enclosure was approximately 15 0 cubic feet per minute.

The wet PETN was loaded into the enclosure in a suicient amount to form a bed approximately W16 inch deep, and the enclosure was operated at a throw of ls inch at a frequency of 750 throws/minute. The travel time for the PETN from the wet to the dry end of the bed was approximately 20 minutes, and the PETN emerging at the dry end of .the bed had a moisture content of 1%.

EXAMPLE 6 A wet carbine-ball powder having the following size distribution:

was screened through a 4 mesh sieve, and brought to the hopper of the apparatus shown in FIGURE 1. Then, at room temperature, it was loaded onto the conveyor belt and fed through the brush feed hopper and the screen, a 4 mesh screen, into the wet end of drying enclosure 1. The temperature of the drying enclosure was kept at 159 F., and the temperature of the drying air was 12S-127 F. The rate of flow of air into the drying enclosure was approximately 250 cubic feet per minute.

The wet smokeless powder was loaded into the enclosure in a sufficient amount to form a bed approximately l)A6 inch deep, and the enclosure was operated at a throw of 1A; inch, and at a frequency of 750 throws per minute. The travel time for the smokeless powder from the wet to the dry end of the bed was` approximately 20 minutes, and the smokeless powder emerging at the dry end of the bed had a moisture content of 1%, and was solvent-free.

EXAMPLE 7 Trinitrotoluene having a moisture content of 10% was brought to the hopper of the apparatus shown in FIG- URE 1, where it was loaded at room temperature onto the conveyor belt and fed through the brush feed hopper and a 2 mesh screen into the wetend port 7 of drying enclosure 1. The temperature of the drying enclosure was kept at 160 F., and the temperature of the drying air was kept at 12S-135 F The air tiow through the drying enclosure was approximately 200 cubic feet per minute.

The wet trinitrotoluene was loaded into the enclosure in a sufficient amount to form a bed approximately 1A inch deep, and the vibration system of the enclosure was operated at a throw of 'l/16 inch, at a frequency of 750 throws per minute. The travel time from the wet to the dry end of the bed was approximately 20 minutes, and the TNT emerging at'the dry end of the bed had a moisture content of about 1%.

EXAMPLE 8 Ammonium nitrate prills, having a moisture content f and a density of 0.82, was brought to the hopper of the apparatus shown in FIGURE 1, and at room temperature was loaded onto the conveyor belt and fed through the brush feed hopper and the screen, a 1 mesh screen, into the wetend of drying enclosure 1. The temperature of the ydrying enclosure was kept at 160 F., and the temperature of the drying air was kept at 130 F. The rate of iiowof air into the drying enclosure was approximately 300 cubic feet per minute.

The wet ammonium nitrate was loaded into the enclosure in a suiiicient amount to form a bed approximately Mt inch deep, and the enclosure was operated at a throw of 1A; inch, and at a frequency of 750 throws per minute. The travel time for the ammonium nitrate from the wet to the dry end of the bed was approximately minutes, and the ammonium nitrate emerging at the dry end of the bed had a moisture content of 0.07%. The material did not cake, and the dry prills were free-flowing.

EXAMPLE 9 Wet RDX (cyclotrimethylene trinitramine) was brought to the hopper of the apparatus shown in FIG- URE 1. Then, at room temperature, it was loaded onto the conveyor belt and fed through the brush feed hopper and the screen, a 2 mesh screen, into the wet end of drying enclosure 1. The temperature of the drying enclosure was kept at 160 F., and the temperature of the drying air was kept at 130 F. The rate of flow of air into the drying enclosure was approximately 200 cubic feet per minute.

The wet RDX was loaded into the enclosure in a sufficient amount to form a bed approximately 11H6 inch deep, and the enclosure was operated at a throw of 3/16 inch, and at a frequency of 650 throws per minute. The travel time from the wet to the dry end of the bed was approximately 20 minutes, and the RDX emerging at the dry end of the bed had a moisture content of 0.1%

It will be evident that the particular temperature, rate of travel of particulate material, air flow rate, and relative humidity and other drying conditions, including the moisture content of the entering material, will be adjusted according to the requirements of the material being dried. If, in a trial run, the material being dried does not emerge from the dryer in a fully dried condition, it will be necessary either to increase the drying temperature or reduce the moisture content of the wet material entering the dryer, or slow the travel rate of the material through the dryer by reducing the throw or the number of vibrations per minute of the vibratory equipment. In the drying of any material, the usual drying conditions in a tray or other dryer can be employed as a start, and these can be adjusted by trial and error until the optimum conditions are obtained in which the desired dry product is delivered from the dry end of the drying enclosure. Modifications necessary to achieve this objective will `be evident to those skilled in the art, and further details need not be given.

In`v the drying nitrostarch, it will generally be found that the drying temperature should be within the range from about 120 to about 160 F. Similar drying temperatures will also be applicable to nitrocellulose and smokeless powder. Explosives that have a lower melting point and/ or are sensitive at temperatures as high as this will, of course, be dried at a lower temperature. Usually, drying temperatures within the range from about to about 250 F. will be found satisfactory for most chemicals, including explosives, and even 250 F.'is" l not the maximum in some cases. The temperature should be kept about 25 F. below the ignition temperature ofany material present and about 25 F. below the softening temperature of the solid, for safety and convenience of operation.

Having regard =to the foregoing disclosure, the follow- 1ng is claimed as the inventive and patentablel embodiments thereof:

1. An apparatus for drying particulate explosives comprising, in combination, an elongated drying enclosure through which the particles of explosive are passed, means for introducing wet particulate explosive at one end of the enclosure to form a bed of such particles within the enclosure, and means for withdrawing dry particulate explosive at the end of thefenclosure, means externally of the enclosure for vibrating the entire enclosure in -a generally forward and generally upward direction, so as to impart a tumbing forward movement to a bed of the explosive particles within the enclosure, means for flowing drying gas through the enclosure, introducing and withdrawing the drying gas from the enclosure at a point 'above the explosive particles, so' as to pass the gas over but not through a bed of the particles within the enclosure, and/ or means for heating the gas and/or the enclosure to a temperature at which drying occurs, if necessary.

2. A drying apparatus according to claim 1, including means for introducing wet explosive particles A,into the enclosure continuously, vand for withdrawing dry explosive particles therefrom semicontinuously. f

3. A drying apparatus according to claim 1, including means for continuously and automatically collecting, batchwise, dry explosive emerging from the elongated enclosure, and removing such batches of dry explosive from the immediate vicinity of the dryer for safety purposes.

4. A drying apparatus according to claim 1, including a iire and/ or heat sensitive deluge system for quenching any tire or excessive generation of heat that may occur in any portion of the` drying enclosure containing dry sensitive explosiveparticles.

5. A drying apparatus according to claiml, including feed means for introducing wet particulate explosive into the enclosure comprising a iirst hopper, a second hopper for delivery of wet particulate explosive to; tlie drying enclosure, a conveyor belt for delivery of particulate material from the first to the second hopper, a brush feeder in the second hopper, and a screen for control of particle size of particulate material fed from the second hopper tothe enclosure.

6. A drying `apparatus according to claim 1 comprising means for delivery of dry particulate explosive to containers, a turntable for delivery of containers therefrom, a car for transporting filled containers from the turntable to storage, and for transporting empty containers to the turntable, and means for rotating the turntable to remove iilled containers from and feed empty containers to the delivery means.

7. A drying apparatus according to claim 6, wherein the turntable and car are operated manually.

8. A drying apparatus 'according to claim 6,A wherein the turntable and car are operated automatically upon iilling of a container at the hopper.

9. A drying apparatus according to claim 1, wherein the drying enclosure is disposed within a tunnel throughout at least the major portion of its length.

10. A drying apparatus according to claim 9, including a plenum chamber above the tunnel for circulation of drying ga-s, ports in the tunnel for entry of drying gas into the tunnel, ports in the ldrying enclosure for entry of drying gas into the enclosure, and means for withdrawing wet drying gas from the enclosure.

11. A drying apparatus according to claim 10, wherein Y the means for withdrawing wet drying gas is designed to maintain the enclosure at a subatmospheric pressure.

12. A drying apparatus according to claim 11, wherein Such means is a water jet aspirator.

13. A drying apparatus according to claim 10, including means for liquid-Washing the withdrawn wet drying gas to recover entrained particulate explosive therefrom.

14. A drying apparatus according to claim 13, including means for recycling drying gas and wash liquid.

15. A drying apparatus according to claim 1, including means for purifying and recycling any solvent removed by the drying gas.

16. A drying apparatus according to claim 1, including means for heating the enclosure.

17. A drying 'apparatus according to claim 16, wherein the heating means comprises a serpentine uid conduit beneath the enclosure and means for circulation of hea-ting uid through the serpentine fluid conduit.

18. A drying apparatus according to claim 17, wherein the serpentine fluid conduit is mounted for vibrational movement Wtih the enclosure, and the means for vibrating the enclosure comprises means for delivering a pulsating ow of heating uid to the serpentine uid conduit.

19. A drying apparatus according to claim 17, wherein the means for delivering a pulsating flow comprises a peristaltic pump.

20. A process for drying particulate explosives and other hazardous chemicals, which comprises continuously introducing such material in wet particulate form at one end of an elongated heating zone, Vimparting a vibratory forward and upward tumbling movement to such material while in the zone, so as to move the material progressively from one end of the zone to another end, at an elevated temperature, if necessary, while owing a drying gas through the zone over the vibrating tumbling particulate material, to entrain moisture from the particulate material in the gas, and remove such moisture from the zone, withdrawing moisture-containing gas from the zone, continuously withdrawing dry particulate material from the end of the zone, and continuously removing the dried particulate material to a point safely distant from the drying zone.

21. A continuous process according to claim 20, in which the drying gas is washed or scrubbed with water td remove any particulate material that may be entrained therein, returning any entrained Wet particulate material thus recovered for recycling.

22. A continuous process according to claim 21, which includes drying the scrubbed drying gas, 'and recycling the drying gas, if desired, and also recovering and recycling the wash water after separation of the particulate material therefrom.

23. A continuous process according to claim 20, wherein the particulate material is an explosive sensitizer that can be detonated when dry, or that turns over from burning to detonation when dry.

24. A process according to claim 23, in which the explosive is nitrostarch.

25. A process according to Claim 23, in which the explosive is nitrocellulose.

26. A process according to claim 23, in which the explosive is smokeless powder.

27. A process according to claim 20, in which the drying is effected at a subatrnospheric pressure.

28. A process according to claim 20, in which the particulate material is at a particle size below 1 mesh.

29. A process according to claim 20, wherein the material is nitrostarch, the temperature of the gas is within the range from about to about 160 F., and the drying gas is air.

30. A process according to claim 29, wherein the wetnitrostarch is at a moisture content within the range from about 10 to about 50% by Weight.

31. A process according to claim 20, which comprises lifting the particles and propelling them forward at an angle from 15 to 75 to the horizontal, to impart such vibratory, tumbling movement thereto.

32. A process according to claim 20, wherein an organic solvent is also removed, and is recovered from the drying gas and recycled.

33. A process for drying particulate explosives and other hazardous chemicals, which comprises continuously introducing such material in wet particulate form at one end of an elongated heating zone, imparting a vibratory forward and upward tumbling movement to such material while in the zone, so as to move the material progressively from one end of the zone to another end, at an elevated temperature, withdrawing moisture from the zone, continuously withdrawing dry particulate material from the end of the zone, and continuously removing the dried particulate material to a point safely distant from the drying zone.

References Cited UNITED STATES PATENTS 2,349,300 5/ 1944 Olsen 34-39 2,529,704 11/1950 Olsen 34-39 XR KENNETH W. SPRAGUE, Primary Examiner.

U.S. Cl. X.R. 34--33, 164

UNlTlfID STATES PATENT OFFICE CERTIFICATE OF CRRECTIN Patent: No. 3: 456s 357 Dated July 22 1969 Inventor-(s) GeOIIG Griffith It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

r:- Column 3, line 8, "ad" should be and Column 6, line 17, "long" should be along". Column 9, line 39, "enclousure" should be enclosure Column 15, line 69, #-f of should be inserted before "nitrostarch". Column 16, line 18 (Claim 1), other should be inserted before "end". Column 16, line 21, "tumbing" shouldvbe tumbling SIGND mn sfuso APR 7 N1970 (SEAL) Attest:

Edward M. Fletcher, JL WILLIAM E. SGHUYLER, JR. nesting Offica. Y Commissioner or Patents

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