US2395367A - Granular ammonium nitrate explosive - Google Patents

Description

?aieuted Feb. 19, 194$ stares GRANULAR AMMONIUM NITRATE EXPLOSIVE No Drawing.

'3' Claims.

This invention relates to a new blasting explosive composition and to a method for the manufacture thereof and in particular to a blasting explosive oi the permissible type which is especially adapted for use in producing lump cool.

It is well ltnown in the art that the sustained heaving action of blast. powder is the most desirable type of force available if it is desired to produce lump coal. This sustained heaving actlon is due to the low rate of detonation of black powder, which rate classes black powder as a defiagrating explosive and not use detonating explosive. However, blaclr powder cannot be used in gaseous mines due to the name characteristics,

, since the dances produced quite often cause excharacteristic oi biaclt powder as used in the production oi cool,

It is the object oi invention to produce an improved explosive composition especially adapted for the production oi coal.

it is a further object of this invention to provide a method for the manufacture of an improved explosive composition. suitable for use in mining coal.

It is a further object of this invention to pro-- duce a permissible explosive which will have a sustained heaving action upon detonation.

it is a'iurther object oi this invention to provide a method of manufacturing a permissible explosive which has a sustained heaving action similar to that associated with black powde It is a further object of this invention to provide a method of producingpellets comprising ammonium nitrate.

It is a still further object of this invention to provide a means of impregnating and pelleting a mixture which when used with nitroglycerin will provide a permissible explosive having a. sustained heaving action upon detonation.

Cther and further objects of this invention will be apparent hereinafter.

The objects oi this invention have been accomplished by grainiug or pelieting admixtures comprising 1o: nitrate and a binding or eelhesive agent into grenuleshaving a predeter- & a delve then admixing with these granules Application April 1172, 194M, Serial No. 888,262 a desired sensitivity and explosive properties. In particular an explosive composition in accordance with this invention has been prepared by admixing ammonium nitrate, a carbonaceous material, and starch in the presence of a wettmg agent, preferably water, which may be supplied by adding to the mixture liquid water or by using salts containing water of crystallization. The admixing of the materials is easily accomplished by raising the temperature of the salt to effect melting or fusing adding carbonaceous and adhesive agents thereto, and while the admixture is in a molten condition or close to a molten condition, passing this molten or semiplastic admixture through a screen, cooling the screened material and admixing with the screened material the desired amount of liquid explosive nitric ester.

In particular, it has been found that highly desirable, granules may be obtained by passing the molten or semi-plastic materials made by admixing ammonium' nitrate, carbonaceous material, a hydrated salt, and a binder, such as for example, starch through an 8-mesh screen and allowing the screened material to fall through a column of cool air, recovering the granules which have thus been cooled and hardened, and then admixing therewith between about 5% and about 15% nitroglycerin or an equivalent liquid explosive nitric ester, such as nitroglycol, nitro sugars, nitrated diethylene glycol, and the like.

A low rate of detonation of the explosive has been found possible by controlling the particlesize of the granules used by passing the material l through the desirable smaller or larger mesh screens. Also by varying the amount of nitroglycerin added to the granules, the detonation rate may be altered.

pounds of explosive. The explosives so produced will have a relatively high sensitivity by the half cartridge sensitivity test and will exhibit velocities which may vary from about 1,200 to 2,000 meters per second depending upon the coordination of granule particle size and percentage of nitroglycerin.

In preparing the granules to which is added the liquid explosive nitric ester, it is preferable to lent explosive nitric ester to give the admix with a preponderance of ammonium n1- the desired sensitivity.

'er,'such as a revolving drum or a heated'evaporating pan having a plow therein or by passing the semi-plastic mass through a screen of the desired size.

It is oftentimes desirable to add various other ingredients to the mix oi ammonium nitrate, wetting agent, and binder and such additive ingredients may be for example, sodium nitrate to increase the oxygen content of the explosive or a carbonaceous material, such as balsa, bagasse, ivory meal, wood flour. manioc, and the like to control the oxygen balance of the admixture and also to control the density of the material when it is grained into its final granule form.

Although I have found it preferable to use vari: ous salts containing water of crystallization in order to wet the adhesive and aid in the forming of a molten or plastic'mass, I may also use water per se in order to obtain the desired end. Thus, water may be added to the admixture at any time during the mixing of the various ingredients, or if desired, the water may be added with the starch or adhesive by forming an aqueous solution of adhesive material and adding said solution to the admixture.

The granules which are produced by admixing the materials described hereinbefore when cooled to room temperatures have a hard outer surface which is comparatively non-absorbent and when the liquid explosive nitric ester is added to these granules. the liquid explosive is substantially maintained on the surface of the non-absorbent grains and provides the finished explosive with It has been found that the preferable amount of liquid explosive nitric ester, usuallyv nitroglycerin, lies between about 5 and 8% as this liquid explosive content provides the explosive with the low detonation rate desirable for producing theheaving action. The ex-' plosive possesses detonation characteristics similar to those possessed by black powder.

In order to further illustrate the new explosive of this invention and to point out in particular the methodof producing the explosive, the following examples are given. .All parts and percentages used are by weight.

Exams! 1 assess? The pelleted ivory meal havingthe above composition was prepared in a grainer by adding starch and the ivory meal to the salts which were melted together at a temperature of 250 F. The admixture was stirred for about 30 minutes and then cooled to below F., removed from the grainer and screened. About half of the charge was pelleted so that it would not pass an 8-mesh screen and the other half was pelleted so that all passed an G-mesh screen and about 20% passed a 40-mesh screen. The pellets produced were extremely hard and tough and adaptable for use in explosive formulations.

In order to determine the usefulness of the pelleted material in an explosive formulation, the following composition was prepared:

To an admixture of 74.3% ammonium nitrate,

3% sodium nitrate, 0.5% chalk, and 16.2% of the pelleted material described hereinbeiore hut screened between a and 40-mesh screens was added 6% nitroglycerin. The formulation after thorough mixing was packed in 1% x 8" cartridges and gave a count of 302 cartridges per 100 pounds of explosive. The Cordeau rate was 1,500 m./sec, and the sensitivity was 16 inches. After five days storage at E, the Cordeau rate was 1,200 m./sec. and the sensitivity was 12 inches by the standard half cartridge sensitiveness test.

EXAMPLES 2-7 Various other carbonaceous materials have been treated with salt melt, and starch and then pelleted through a screen to provide examples of xplosives. The pelleted materials were admixed with. a liquid explosive nitric ester usually and preferably nitroglycerin to form an explosive composition. Thetable below shows the composition of six samples of material pelleted with the aid of starch.

Table I Pellet No.

2 a 4 a a 7 Salt-melt 1 78.0 75. .0 33.4 35.4 66.7 Bagssse-Celotex... 19.0 12.0 Starch 3.0 2.0 20 1.3 1.2 :11 Fine ivory meal.. 11.0 58.0 32.0 22.5 Fine oat hulls 19.3 Wood pulp... 7. 3 NH4N03 33.3 40. Screentemp.F.-. 200 an 225 225 -190 210-220 Composition fore $alt melt ingredients: melting NHN0| 11.3 Mg sNomamo a 1.3 N8, 0- 10.4 N501 5.0

A pelleted product was prepared by impregnating ivory meal with a salt mixture comprising ammonium nitrate 77 magnesium nitrate 7.3%, sodium nitrate 10.4%, sodium chloride 5.0% and starch. This material after admixing had the following composition.

Composition Percentage 30. 8 2. 0 4. l 1. 9 Starch 5. 9 Fine ivory meal. 54. 0

In preparing the pelleted material, the carbonaceous ingredients were added to the salt which was in a melted condition and held at 250 F., the admixturethoroughly stirred for about 15 minutes, allowed to cool and screened through an s-mesh screen which was held four to five feet above the floor. The pelleted material passing v through the screen dropped through the four or five feet of air and was cooled to an extent that produced pellets which maintained their granular form, were hard. and non-absorbent.

' Theabove six samples of pelleted material were used in dynamite formulations in accordance with the following table:

2,895,887 I Table II Granular product per cent 73 Nitroglycerin 12 NH4NO3 do 8 Powder composition, percent NaNoa fin 7 2 3 4 5 6 7 5 1%" x a" ctgs./l00. lbs. 574 Cordeau rate m./s 1,620 Sensitiveness-normal inches 10 N itroglycerin NH NO ONO Chalk Tests:

Count (1% x 8)/ V 100 lbs 398 352 290 310 336 314 Rateby Cordeaunorma] (m./s.) 1,460 1,410 1,390 1,290 1,280 1,280 Sens. normal,

inches 8 12 12 20 20 Exsmrm 8 To produce a desired ingredient 27.2 parts of potato starch dissolved in 500 parts of water were admixed with 152 parts of 50/50 balsa/bagasse-and after partially drying this admixture, a molten mass comprising Parts NH4NO3 436.8 Mg (N03) 2.61120 45.6 NHiCl 28.8 NaNOa 109.8

was added thereto with stirring. The stirring was continued until the carbonaceous material had absorbed the salt or become impregnated therewith and a granular product formed. This granular 'product was used in a dynamite formulatior. which had the following properties.

A granular product was produced in accordance with Example 8 except that the starch solution was added after the balsa/bagasse had been treated with the molten salt admixture. llhe material after addition of the starch was heated and stirred until dry. The granular product was used in a dynamite formulation which had the following properties Granular product per cent 73 Nitroglycerin do 12 NH4NO3 ..dO 3 NaNOs do '7 1%," x 8" ctgs./100 lbs. 444 Cordeau rate m./s 1,785 Sensitivenessnormal inches 24 EXAMPLE 10 A granular product was produced in accordance with the procedure of Example 9 except the starch added to the balsa/bagasse was in the dry state. The material was stirred until the starch had been thoroughly dissolved and distributed through the mass. The granular product after cooling was used in a dynamite formulation which had the followin pro erties.

From the above examples, it will be seen that the pelleted salt-carbonaceous-adhesive admixture when admixed with a liquid explosive provides an explosive composition having a low rate of detonation and a. high sensitivity. This type explosive gives unusual advantages when lump material is to be produced. The explosive gives a heaving action similar to black powder which is highly desirable since this type action prevents the production of large amounts of fines.

It will be understood that the details and examples hereinbefore set forth are illustrative only and that the invention as broadly described and claimed is in no way limited thereby.

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

1. The method of preparing a. granulated explosive, which method comprises intimately intermingling a preponderantamount of ammomum nitrate, starch, a carbonaceous combustible ingredient, and water in an amount less than 5% of the entire composition, subjecting the mixture to the action of heat, forming the blend of materials, while still plastic, into distinct agglomerates of controlled size, cooling to convert said agglomerates into firm. free-flowing grains, and surface-coating said grains with nitroglycerin in an amount less than 10% of the entire composition.

2. The method of preparing a granular explosive, which method comprises intimately intermingling a preponderant amount of ammonium nitrate, starch, a carbonaceous ingredient, and a salt containing water of crystallization, sub- J'ecting the blended mixture to a temperature suflicient to fuse said salt containing water of crystallization, forming the blend of materials into distinct agglomerates of controlled size, cooling to convert said agglomerates into firm, free-flowing grains, and coating the surface of said grains with nitroglycerin in an amount less than 10% of the entire composition.

3. A detonatlng explosive especially adapted to the mining of coal, comprising a blend of ammomum nitrate. a carbonaceous combustible material, and a binder substantially insoluble in nitroglycerin, said blend being in the form of firm sized aggregates of such size that substantially all are held on a BO-mesh screen, said aggregates having a. surface coating of nitroglycerin in an amount not more than 10% of the entire explosive composition.

4. A detonating explosive especially adapted to the mining of coal, comprising a blend of ammonium nitrate, a carbonaceous combustible material, a binder substantially insoluble in nitroglycerin, and a salt containing water of crystallization, said blend being in the form of firm sized ag regates of such size that substantially all are held on a. 30-mesh screen, said aggregates having a surface coating of nitroglycerin in an amount not more than 10% of the entire explosive composition.

5. A detonating explosive especially adapted to the mining of coal, comprising a blend of ammonium nitrate, a carbonaceous combustible material. a binder substantiallv insoluble in nitm.

glycerin, anda salt containing water of crystallization, said blend being ionned oi firm sized aggregates, d said aggresateshaving a surface coating of nitroglycerin in an amount not more than 10% ot the entire explosive composition and sumcient to give a sensitivity 01. at least 1e? asmeasured by the'baif cartridge sensitive= neas test.

1 6. A detonating'explosive especially adapted to the mining of coal, comprising a blend of emmonium nitrate, a carbonaceous combustible material, a binder substantially insoluble in nitro glycerin, and magnesium nitrate hezahydrate, said blend being in the form of firm sized ag regates 0! such size that substantially all are held on a iii-mesh screen, said aggregates having a surface coating of nitroglycerin in an amount not more than 10% 01 the entire explosive composition. i

7. A detonating explosive especially adapted to the mining of coal, comprising a blend 0! ammcnium nitrate, a carbonaceous combustible !Y terial and starch in hard tenacicus farm, said blend being in the form of firm sized aggregates of such size that substantially all are held on. a 30-mesh screen, said aggregates having a surface coating of nitroghrcerin in an amount not more than 10% or the entire explosive composition. I