US2316195A

US2316195A - Apparatus for the manufacture of smokeless powder

Info

Publication number: US2316195A
Application number: US325515A
Authority: US
Inventors: Troxler Bernhart
Original assignee: Hercules Powder Co
Current assignee: Hercules Powder Co
Priority date: 1939-02-14
Filing date: 1940-03-23
Publication date: 1943-04-13
Anticipated expiration: 1960-04-13

Description

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B. TROXLER APPARATUS FOR THE MANUFACTURE OF SMOYKELESS POWDER Original Filed Feb. 14, 1939 mwmzwozoo N o- 1! i l April 13, 1943.

BERNHART TROXLER INVENTOR.

BY wk; (".1

Patented Apr. 13, 1943 APPARATUS FOR THE MANUFACTURE OF SMOKELESS POWDER Troxler, Kenvil, N. J'., assignor to Hercules Powder Company, .Wilmington, Del., a corporation of Delaware Original application February 14, 1939, Serial No. 256,314. Divided and this application March 23, 1940, Serial No. 325,515

7 Claims.

This invention relates to an improved apparatus for manufacturing propellant smokeless powder and more particularly to an improved apparatus for recovering the excess solvent from and the drying of single "base smokeless powder.

It is well known by the art that smokeless powder manufacture includes the fololwing steps: the dehydration of the raw material, nitrocellulose or reclaimed smokeless powder; the colloidin of the dehydrated material with a solvent or solvents, for example, an ethyl ether-ethyl alcohol or an acetone-ethyl alcohol mixture; the forming of the colloided mass into strands by pressing through one or more dies; the cutting of these strands-into short lengths called grains; the treating of thegrains to remove the excess solvent; the drying of the treated grains; the

screening of the grains to remove clusters and foreign material and the blending of the dry grains to produce a uniform product.

In the above process the steps of dehydration, colloiding, pressing, cutting, and blending have been developed to a high state of efiiciency and comparative safety but the step of processing the grains to remove the excess solvent, the step of drying the grains, and the step of screening of the grains, at present, from a standpoint of efliciency, economy, and safety show many disadvantages.

Nowin order to produce a smokeless powder that will give satisfactory ballistics, it is necessary to control the amount of total volatile matter, retained in th grains, within very definite limits. Such limits are determined by the type of powder and the ballistics required. Therefore, the removal of the excess solvent and moisture from the grains is of the utmost importance in the manufacture of an acceptable powder. These two steps also have an economic effect on the process as the time required and the equipment needed for recovering the excess solvent and for the drying of the powder have a verydeflnite bearing on the per pound cost of the completed powder.

The art originally placed the powder grains in a dry house after the cutting operation and by forcing hot .air through the mass drove the solvents from the grains but it is obvious that this was a very expensive operation as the solvents were .lcst. At present/the method of removing and recovering the solvents from the grains includes placing the powder grains in a solvent recovery system that consists of a number of recall condensed vapors to astorage tank where they await recovery by rectification. The reduction of the solvent content of the powder grainsbythis method cannot be carried out to the desired low percentage and, therefore, it is necessary to further treat th grains in what is commonly termed by the art a water-dry system. The water-drying of the grains consists of treating the grains with hot water for a suflicient period to effect the reduction of solvent content to the desired per cent.

From the water-dry operation the powder is taken to dry houses where it is spread on trays and heated by forced air drafts until dried to the total volatile content desired. The dry-houses are expensive and the drying procedure is hazardous. The powder is loaded in wooden trays that are positioned in the dry house to allow air circulation which must be controlled in regard to temperature and speed as high temperatures cause excessive deterioration and the possibility of fire, while excessively fast drying caused by rapid circulation causes uneven drying.

From the dry houses the powder must be placed in storage or taken direct to a screen house to remove all clusters and foreign material. From the screening operation the powder is stored or taken directly to the blender where a substantially uniform product is produced.

tangular boxes or bins that have air-tight covers It will be apparent to those'skilled in the art that each of the described processes requires at least two handlings of the powder and furtherthat each time powder is handled there are losses and the operators are exposed to the inherent hazard of handling explosives. It is also well acare very expensive and operations, and that will prevent the loss of powder. Other objects will appear hereinafter.

grains; and the screening of the dried product. The above processes are all carried out within one piece of apparatus and, therefore, the powder being processed is handled only during the loading and unloading of the tank.

It will be apparent that by using the apparatus in accordance with this invention many advantages over the established methods of the art may be enjoyed. After the loading of the tank with a predetermined amount of powder there is no need of further labor until the powder is dry and ready to be removed from the tank. During the dumping of the tank the powder is automatically screened and when the dumping operation is complete the powder is ready to be blended. The method which may be carried out with the apparatus in accordance with this invention has been found to be more efficient than the methods ordinarily used by the art especially in regards to the time consumed for properly processing the powder; in the amount of solvent recovered from the grains; in economy of labor; and in the yield of powder obtained.

A very marked increase in safety is effected by using the apparatus in accordance with this invention for the manufacturing of smokeless powder, as the handling of the powder is reduced to a minimum and such an advantage provides a definite improvementin the explosive art.

Having now indicated in a general way the nature and purpose of this invention, there follows a more detailed description of preferred embodiments thereof, with reference to the accompanying drawing in which:

The figure indicates diagrammatically, with parts in section, the preferred embodiment of the apparatus of this invention for the manufacture of smokeless powder.

To facilitate an understanding of the method 'of treating smokeless powder' with the apparatus of this invention, a detailed description of the apparatus used will be made with reference to a part of the figure.

The tank l, which is shown in section, is of a novel design that permits the carrying out of the solvent recovery, water dry, and air dry process steps without disturbing the powder charge once it has been placedrin the tank. The tank I has an opening 2 at the top which is closed by a cover 3 that is shapedto fit into the water seal trough 4 around the opening 2. The cover 3 is further designed in the shape of a funnel that has an opening 5 located directly above the centhe powder within the tank.

The tank I also has a false bottom l0 covered with a screen II and which is shaped like a funpowder charge.

nel to aid in the removal of the powder charge through valve l2 centrally located in the bottom of the tank. The funnel shaped false bottom is covered with screen ll of sufficiently fine mesh to prevent the powder grains from passing through but which will allow the free circulation of air throughout the tank. It will be understood that the screen mesh may be altered to suit the type of powder being processed. The screen H as will be noted has been deleted in parts to allow the clear showing of other parts of the'tank.

In the center of the tank are located three concentric rings l3 which are so placed that the powder is prevented from filling the center of the tank I and also are so placed to form a layer of powder throughout the tank which is approximately of uniform thickness. These rings may be placed to form any thickness of powder desired and if desired a larger number of rings may be used to produce a'more uniform powder layer. The rings used are solid but may be made from screening materialif desired. The rings while not essential are highly desirable as a much more uniform solvent recovery and air dry are obtained through their use in a much shorter length of time. While rings have been specified as desirable, the use of various shaped means are contemplated for maintaining the powder grains in their proper position as regard thickness of the layer of powder within the tank and such variations will be obvious to those skilled in the art.

The valve I2 in the bottom of the tank may be of any type suitable for removing the powder grains from the tank. The type shown consists of a plunger l4 attached to a rod I5, acting through a guide It, that extends to within a few inches of top point 6 of the spreader 1. The valve I2 is therefore easily operated, from the top of the tank. A slot type valve has also been found suitable but the valve used should obviously be one which will not tend to jam the powder grains when operated and, further, the valve must be water and vapor tight.

The tank must be of vaporproof and waterproof design and may be fabricated from aluminum, copper, or the like or may be a lined wooden tank. While ferrous alloys may be used it is not desirable to include any metal from which sparks may be struck due to the explosive nature of the with the necessary air and water valves to carry out the processes and the method of making such connections will be obvious to those skilled in the art.

There now follows a description of the process for treating the powder in the apparatus of this invention. The grains of powder from the cutting machine are processed, in the single tank I- described hereinbefore, to the'point where they are ready for blending. The process with reference to the figure is carried out by loading tank I, via opening 2, with powder grains from the cutting machines. The spreader I distributes the powder evenly within the tank i and also aids in breaking up any clusters of powder that may have formed while the powder grains were in the container at the cutting machine. The tank i is preferably filled with powder to within a few inches of the bottom of the spreader I and then a water sealed cover 3 is'placed over the opening 2 to prevent the loss of vapor. It is to be understood that the process of this invention may be carried out with any amount of powder in the tank but from an Further, thetank is equipped v emciency standpoint it is preferable to fill the tank.

During the charging of'the tank the three-way air valve I! is set to allow the circulation of air from fan l8 through heater down through the powder in tank I, out through the three-way air valve I1 to the condenser 20. The hot air from the heater I9 absorbs solvent vapor from the powder and substantially all these absorbed is filled to the desired height the circulation of air is continuous until the solvent content is reduced to a low percentage.

It is well known that the 'old' method of solvent recovery resulted in clustering and distortion of the powder grains. I his was due to the fact that it was not practical to operate the solvent recovery process while filling the old typeapparatus. Thus, the old method allowed solvent to condense within the apparatus which softened the grains and due to the weight of the powder those softened grains clustered and were distorted. With the solvent recovery apparatus of this invention, clustering and distortion need not beexperienced because the hot air may be circulated until the apparatus is brought up to the operating temperature before any powder is put in the tan'k. Further, the air circulation is continuous valve I2 in the bottom of tank I and allowing the powder to run'freely from the tank. The funnel shaped false bottom I0 greatly aids in the dumping of the tank as will be apparent from the' drawing. The screen 25 located just below the valve-I2 allows the powder to be screened as the tank is emptied and the valve I2 is so regulated that the amount of powder leaving the tank I may be conveniently screened and packed into bags.-

The powder afterbeing bagged is ready to be sent to the blender or to storage and the tank Ifroni which it was removed is ready for another charge of powder.

It will be apparent to thoseskilled in the art that the mode of operation of the apparatus described above will lend itself readily for use with.

any type of powder from which the solvents are to be recovered and it will also be understood that variations in design and operation are contemplated and are within the spirit of this invention.

The heaters I9 and 24 are fed with steam and are automatically regulated to maintain the *desired air temperatures during the solvent recovery and air drying operations. The fans I 8 and 23 must be of sufllcient capacity to efllciently remove the solvents and water from the powder in the desired lengths of time. the fan 23 for drying the powder will be of much I greater capacity than the fan I8 used to circulate during the tank loading period except for the 3 various short intervals of time that powder is actually being dumped into the tank, therefore, removal of solvent from the powder starts as soon as it enters the tank, thus causing the grains to harden which eliminates the clustering and distortion of the grains that was experienced in the method known to the art.

After removal of the solvent by air circulation the residual solvent must be removed andthis is accomplished by closing the three-way air valve I1 and adjusting the three-way water valve 2| to allow the tank I to be filled with hot water. The tank I is filled to an overflow pipe 22 above the level of the powder, and the valve 2| then so adjusted to keep suilicient water circulating to maintain the proper temperature. During the water dry operation, the cover 3 is removed to allow all vapors to escape to the air. This water dry operation is continued until the residual solvent is removed from the grains to a point that complies with the particular specification being used, after which the powder is ready to be air dried.

The air drying of the powder is accomplished by draining the water from the'tank I through valve 2| and then so adjusting valve I! that air from the fan 23 may be blown through heater 24 into tank I and through the powder. The cover 3 is left open andthe drying air is exhausted to the atmosphere. The powder at the end of the drying operation has the proper moisture content and is, of course, quite hot. To prevent the handling of hot powder th heater 24 is turned oif and cold air blown through the powder until the powder temperature is approximately equal to room temperature.

The powder is now ready to be removed from the tank and thisis accomplished by opening the air for removing the solvent vapors.

The three-way valves IT and 2| may be standard air and water valves or 'a series of connections may be made to perform the function of these two valves.

The screen 25 is positioned under the dumping" valve I2 and is designed and placed to obtain effective, screening of whatever type of powder is being manufactured. It is desirable to have a screen holder that allows changing of screens easily if a variety of granulations are to be manufactured. The screen, as will be obvious, may be equipped to remove large and small particles of powder and may also be equipped with any suitable means for aiding in bagging the powder. A screen used in screening powder is preferably not of the vibrating type and, therefore, the screen used in this invention has been placed at an angle and th'e'powder allowed to flow over it by ravity.

In the operation of the apparatus of this invention,it has been found that various inert gaseous mediums may be circulated through the powder charge to remove the excess solvent butit has been found preferable to use air at a temperature within the range of about 50 C. to about 60 C.

' The so-called water dry step is preferably carried Themanufacture of smokeless powder in ac-' cordance with the apparatus of this invention shows very definite advantages over the meth d now used by the art. The improvement and advantages may be shown by the comparison of data of the two examples given below.

Example I A lot of single base smokeless powder, for use in the m./m. howitzer, with a granulation of It will be obvious that accepted methods of solvent recovery, water drying, air drying, and screening with the following results.

A lot of single base smokeless powder, for use in the 155 m./m. howitzer, with a granulation of .0675-.030 x .250 was manufactured by using the apparatus set forth by this invention with the following result:

Powder mixed -pounds 1,275,200 Powder shipped -do.. 1,275,367 Loss in manufacture per cent none Solvent used--ether and alcohol ounds 1,014,592 Solvent recovered-ether and alcohol I pounds 292,383 Solvent recovered per cent 28.82

Operating time for- Solvent recovery at 55 C ..hours 72 Water dry at 55 C ..-do 96 Air dry at 55 C do Screening -..do

' Operating time--Total do- 186 or 7% days From a comparison of the results of: the two examples above it is obvious that the apparatus in accordance with this invention is much superior to the ordinary apparatus of the art. It is noted that the yield has been raised from 99 to 100% which is a substantial improvement, especially when the lots manufactured run about a million pounds. A more marked improvement is noted in the amount of solvent that it is possible to recover from the powder as the apparatus of this invention provides for about a 29% recovery against about a recovery by the apparatus now used by the art. It will be noticed that the time of the manufacturing cycle has been cut approximately in half with a consequent saving in labor cost and with a possible increase in production.

The labor cost per 100 of powder manufactured in accordance with this invention is about onesixth that of the old art method.

The above advantages are all material but the advantage of increased safety of operation must be taken into account. The apparatus in accordance with this invention eliminates many handlings of the powder which at best is a dangerous occupation and further by this method there are only about 9000 pounds of dry powder in a building at one time whereas the old art method of dry house operation may have as high as 50,000 to 100,000 pounds of dry powder in one building.

The combining of the four ,operations of sol- .0675-.030 x .250 was manufactured by using the vent recovery, water dry, air dry, and screening has eliminated practically all handling of the powder which furthers the safety of the operation. And also since each of these operations is usually carried out in a special building, there have been eliminated three-quarters of the buildings and equipment needed to process the powder.

It will be understood that the details and examples given hereinbefore are illustrative only and in 'no way limiting on my invention as broadly described hereinbefore and in the appended claims.

This application is a division of my application, Serial Number 256,314, filed February 14,

What I claim and desire to protect by Letters Patent is:

1. A smokeless powder processing apparatus comprising a tank having a loading opening therein for entrance of smokeless powder grains into said tank, entrance and exit means in said tank for circulation of iluids therethrough, means for positioning the powder grains in a mass of substantially uniform thickness within said tank whereby the fluid resistance of the mass is maintained substantially constant, discharge means for removing the grains from said,

tank, and aclassification screen adapted to separate grains into the desired grain size.

2. A smokeless powder processing apparatuscomprising a tank, entrance means for loading a. mass of smokeless powder grains into said tank, distributing means for positioning the grains in said tank and maintaining the fluid resistance of said mass approximately constant, conduit means connecting the top and bottom ofsaid tank and circulating means for passing a fluid through said conduits and mass discharge means for removing the grains from said tank, and a classifying means below said discharge means adapted to classify the grains into desired grain sizes.

3. A smokeless powder processing apparatus comprising a tank having an opening in the top thereof for receiving a mass of smokeless powder grains, and having a discharge opening at the bottom adapted for the removal of the powder mass, a conical spreader below said top opening, adapted to distribute the grains about the inner walls of said tank, concentric rings substantially centrally positioned within said tank to maintain the smokeless powder grains in a substantially even thickness, conduit means connecting the top and bottom of said tank and circulating means for passing a fluid through said conduits and mass and a foraminous funnel shaped bottom in said tank, the apex of which is positioned above said discharge opening.

4. A smokeless powder processing apparatus comprising a tank, loading and discharging means at the top and bottom of the said tank, said means being of vaporproof construction, a conical spreader below said loading means, a foraminous funnel shaped bottom above said discharge mearis, means centrally located in said tank adapted to maintain an even thickness of .smokeless powder grains, and means for circulating fluid through said tank.

5. A smokeless powder processing apparatus comprising a tank, loading and discharging means at the top and bottom of the said tank. said means being of vaporproof construction, a

I conical spreader below said loading means, a fotank adapted to maintain an even thickness of smokeless powder grains, means for circulating fluid through said tank, and a screen positioned below said discharge means for classifying the smokeless powder upon discharge from said tankl l i 6. A smokeless powder processing apparatus comprising a cylindrical tank, an opening having a gas-tight cover in the top of said tank adapted for charging smokeless powder grains into said tank, a distributing cone below said opening forming a distributing means to' peripherally dispose said grains in said tank. a false bottom in said tank to support said grains. said bottom being foraminous and funnel shaped. a discharge valve at the vortex of said funnel for removing said grains from .said tank, conduit means connected to said tank'above and below said false bottom, and means to circulate a gaseous medium through said tank connected in said conduit means.

'7. A'smokeless powder processing apparatus discharging means in the bottom thereof, said charging means adapted to fill said tank with powder grains and comprising an. opening with a gas-tight cover and said discharging means adapted to remove said grains from saidtank and comprising a gas-tight valve, supporting means in said tank to support said powder grains comprising a permeable funnel-shaped false bottom with the vortex thereof positioned over said discharging means, conduit means connected to said tank above and below said permeable false bottom and circulating means in said conduit means adapted to force a gaseous medium through powder grains positioned on said false bottom.