US2168020A

US2168020A - Black powder manufacture

Info

Publication number: US2168020A
Application number: US127401A
Authority: US
Inventors: Jr Clarence W Brooks
Original assignee: EI Du Pont de Nemours and Co
Current assignee: EIDP Inc
Priority date: 1937-02-24
Filing date: 1937-02-24
Publication date: 1939-08-01
Anticipated expiration: 1956-08-01

Description

' '1 1939- c. w. BROOKS, JR 2, 6 ,0

BLACK POWDER mmumcwunn Filed Feb. 24, 1957 WHEEL/N6 SCREENING 7'0 GPANULATE PREDRY/NG STEP PRESS/N6 INTO Pt'LLET FORM AT HIGH DENJ/T) CLARENCE W BROOKS, J'rr. INVENTOR.

A TTORNEY.

Patented Aug. 1, 1939 BLACK POWDER MANUFACTURE Clarence W. Brooks, .lr., Wenonah, N. J., assignor to E. I. du Pont de Nernours & Company, Wilmington, Dcl., a corporation of Delaware Application February 24, 1937, Serial No. 127,401

10 Claims.

This invention relates to an improved process for producing pellets or blocks of black blasting powder having a relatively high density.

Black blasting powder, compressed into the form of cylindrical pellets or blocks, has been introduced into practice with considerable success within the last few years, this form of powder largely replacing the glazed granular black blasting powder previously used. Such pressed powder commonly comprises pellets about 2 inches in length and with diameters varying from 1 to 2 inches. Four of the above pellets of 2-inch length are ordinarily enclosed end to end in a paper wrapper. This package resembles a stick or cartridge of dynamite and may readily be loaded into a borehole.

These pellets commonly have the ordinary black powder composition, for example 72% sodium nitrate, 12% sulfur, and 16% charcoal, blended by thorough incorporation of the ingredients in the customary edge runner wheel mills. The product of such incorporation is known as wheel cake. Wheel cake is the incorporated powder base which is subsequently processed through several intermediate stages for the purpose of obtaining the finished forms in which all black blasting powders are customarily used.

The prior art methods of producing black powder pellets of relatively high density have commonly utilized the product known as green grain as the material for pressing. By high density is meant an apparent density of 1.45 to 1.60, such that there will be 115 to 105-l 8" cartridges per 50 pounds. Green grain is produced by first pressing wheel cake into slabs of high density, approximately 2 feet square and 1 inch thick,

this material being designated by the industry as.

press cake, having a density of 1.70 to 1.80. The press cake is then corned to a granulation suitable for pressing into pellets. A suitable granulation is that passing through an opening of 0.115 inch and held on a screen having openings of 0.046 inch. Green grain produced in this manner is characterized by a high density, 1.7 to 1.8, and possesses a hard, clean, grainy structure. Pellets are produced from this material by feeding it into a mechanical press where it is given the desired cylindrical shape and a center hole is provided running longitudinally throughout the pellet, for example in diameter.

It will be seen, therefore, that prior art methods of producing high density pellets have had to start with a form of powder that has already been given considerable treatment. While screened wheel cake has been employed for direct compression into pellets, as disclosed by Brooks and Johnson, in United States Patent No. 2,062,636, such pellets have been characterized by low density, for example between 1.3 and 1.4, such that 130 to 120 cartridges are contained in a 50-pound box. It has been found to be impossible to produce by this or any other method known to the prior art, high density pellets directly from wheel cake which possess satisfactory burning speeds.

Pellets of varying density are required in different types of blasting and on different occasions, and considerable advantage would result in simplicity of operations if high density pellets could be produced directly from wheel cake.

An object of the present invention is an improved process for producing high density black powder pellets. A further object is such a method wherein increased simplicity and safety in operations is obtained. A still further object is a method for the production of black powder pellets of relatively high density and satisfactory high burning speeds directly from wheel cake. Additional objects will be disclosed as the invention is further described hereinafter.

I have found that the foregoing objects are accomplished by the process of the present invention, which comprises subjecting wheel cake to a preliminary drying process and afterwards compressing into a pellet form of high density.

As a result of this process, high density pellets may be prepared directly from wheel cake, yet possessing the desired high burning speeds. The beneficial effect of the predrying step upon the burning speed of the resulting pellet is directly proportional to the amount of drying.

My preferred process may be more readily understood by referring to the accompanying drawing which constitutes a flow sheet showing in preferred sequence the steps of forming the wheel cake, screening said wheel cake to granulate the same and to remove the fines therefrom, passing the wheel cake, granulated by said screening, through a predrying step, and pressing said predried granules into pellet form at high density; namely, at densities of at least 1.40. It will be noted that the very important and novel step about which the invention centers; namely, the predrying step, has been emphasized in the flow sheet by means of a double line.

I prefer to use the following procedure. The black powder composition is incorporated under the wheels at a moisture content between 6 and 10%, preferably about 6.5%. The moist wheel cake is first screened somewhat to produce a more or less granular product. It is then desirable to reduce the bulkiness of this granular product. This can be accomplished by the removal. of the dust and a portion of the finer particles, for example by passing all the material through a 4- mesh screen and utilizing the portion that is held on a 16-mesh screen. This wheel cake is then dried to a moisture content between 1.5 and preferably between 2 and 3%. This wheel cake which has been subjected to a preliminary.

drying is then pressed in the pellet press. The pellets are subsequently dried to a moisture content lower than 1% and preferably to less than 0.5%. These pellets have a density comparable to that of the high density pellets of the prior art, for example 1.40 to 1.65. Furthermore, the pellets thus produced possess much more satisfactory high burning speeds than do pellets produced directly from wheel cake with the omission of the drying step. This result maybe illustrated bythe following table, which shows a comparison with respect to burning time of high density pellets produced from corned press-cake, grained wheel cake, and predried wheel cake grain respectively. The density is stated in terms of cartridges per 50 pounds of powder. The pellets employed in these measurements were 2 inches in length and 1 inches in diameter.

Burning timeseconds Density, ctgs./50 lbs. Corned Grained 5 5352 5 2 press-cake wheelcake grain l.4tol.8 2.213026 l0tol.4 2.0t0 2.4 1.8to 2.2

It becomes apparent from these results that by the process of the present invention pellets are produced which display burning speeds asrapid as those produced from corned press-cake at comparable densities. Further, it may be noted that the preferred process produces pellets which have higher burning speeds than those produced directly from wheel cake without employing the drying step and indeed, the'burning speeds are even higher than those of pellets pressed to a lower density by this latter'process. This result is unexpected in view of the general principle for pelleted black powder compositions that speed of burning decreases as density increases. As shown, pellets produced directly from wheel cake without preliminary drying at a density of 110 cartridges per 50 pounds require much longer burning time than pellets from predried wheel cake grain at the higher density of 106 cartridges per 50 pounds. r

The above preferred method may be varied in several ways. For instance, instead of screen ing and removing the fines prior to the drying step, the moist wheel cake may be dried directly. It is then desirable to screen the wheel cake and reduce the bulkiness thereof by removing the fines immediately after drying. Again, the wheel cake may be simply screened either before or after the drying steps without the removal of the fines. In other words, although the chief benefits of the invention are derived from the step of predrying prior to pressing, these benefits are increased by supplementing this drying step with the auxiliary operations of screening and reduction of bulk.

The method outlined in the foregoing makes possible to the art for the first time the production of high density black powder pellets of satisfactory high burning speed, directly from wheel cake and has a number of other advantages over those heretofore in use for the production of high density pellets. By the direct use of wheel cake, the procedures of pressing the wheel cake and passing the cut press cake through a coming mill are eliminated. This is a distinct safety contribution to the process, since definite hazards are associated with the operation of press and corning mills. It means also a simplifying of black powder pellet manufacturing procedure by cutting out the two steps named.

The pellets, asformed in the press, will desirably be of the usual cylindrical form, with the central perforation longitudinally through the pellet. These pellets, as stated, are customarily of 2-inch length and of varying diameters from 1 to 2 /2 inches, four of these pellets being wrapped end to end in a paper wrapper to form an, 8-inch cartridge. My invention is not limited necessarily, however, to such products. The powder may, for example, be compressed into any predetermined form.

My improved process of manufacturing high density pellets has been described in detail in the foregoing. It should be understood, however, that many variations in procedure and in minor points may be adopted without departure from the scope of the invention. I Wish, therefore,,1to be limited only by the following patent claims:

I claim:

1. The process of producing high density pellets of black blasting powder from wheel cake, which process comprises subjecting the wheel cake to a preliminary drying step and compressing said dried wheel cake to a density of at least 1.40.

2. The process of producing high density pellets of black blasting powder from wheel cake, which process comprises screening vsaid wheel cake, subjecting said screened wheel cake to a preliminary drying step and compressing said screened, dried wheel cake into a container of predetermined form at a density of at least 1.40.

3. The process of producing high density pellets of black blasting powder from wheel cake, which process comprises screening said wheel cake, removing the fines therefrom, subjecting said screened wheel cake to a preliminary drying step/and compressing said screened, dried wheel cake into a container of predetermined form at a density of at least 1.40.

'4. "The process of producing high density pellets of black blasting powder from wheel cake, which process comprises subjecting said wheel cake to a preliminary drying step, screening said dried wheel cake, and compressing said dried, screened wheel cake into a container of predetermined format a density of at least 1.40.

5.'The' process of producing high density pellets of black blasting powder from Wheel cake, which process comprises subjecting said wheel cake to a preliminary drying step, screening said dried wheel cake and removing the fines therefrom, and compressing said dried, screened wheel cake into a container of predetermined form at a density of at least 1.40.

6. The process of producing high density pellets of black blasting powder'from wheel cake, whichpprocess comprises subjecting the wheel caketo a preliminary drying step and compressing saiddriedwheel cake to a density greater than 1.40 in a container'of predetermined form. 75

'7. The process of producing high density pellets of black blasting powder from wheel cake, which process comprises predrying said wheel cake to a moisture content between 1.5 and 5%, and compressing said dried wheel cake into a container of predetermined form at a density of at least 1.40.

8. The process of producing high density pellets of black blasting powder from wheel cake, which process comprises predrying said wheel cake to a moisture content between 1.5 and 5%, compressing said dried wheel cake into a container of predetermined form at a density of at least 1.40, and imparting a still harder surface to said pellet powder by drying to a moisture content below 1.0%.

9. The process of producing high density pellets of black blasting powder from wheel cake, which process comprises screening said wheel cake, predrying the same to a moisture content between 1.5 and 5%, and compressing said dried wheel cake into a container of predetermined form at a density of at least 1.40.

10. The process of producing high density pellets of black blasting powder from wheel cake, which process comprises subjecting wheel cake having a moisture content between 6.0 and 10% to a preliminary drying step wherein. said powder is dried to a moisture content between 1.5 and 5%, and compressing said dried wheel cake into a container of predetermined form at a density of at least 1.40.

CLARENCE W. BROOKS, JR.