US3455750A - Nonaqueous inorganic oxidizer salt blasting compositions containing silicon component of particular size - Google Patents

Description

3,455,750 NONAQUEOUS INORGANIC OXIDIZER SALT BLASTING COMPOSITIONS CONTAINING SILICON COMPONENT OF PARTICULAR SIZE Robert W. Lawrence, Bancroft Manor, Wilmington, Del., assignor to Hercules Incorporated, Wilmington, Del., a corporation of Delaware No Drawing. Filed Dec. 29, 1967, Ser. No. 694,367 Int. Cl. C06b 1/04 U.S. Cl. 149-21 17 Claims ABSTRACT OF THE DISCLOSURE A nonaqueous inorganic oxidizer salt blasting agent of the nitrocarbonitrate type containing, as an energizer component, from 2 to 18 weight percent particulate silicon and/or silicon-metal alloy(s) substantially all of which will pass through a 30 mesh U.S. standard sieve, and said alloy(s) having a silicon content of at least 70 wt. percent.

This invention relates to nonaqueous inorganic oxidizer salt blasting agents of the ammonium nitrate-fuel oil and nitrocarbonitrate types, containing particulate silicon and/ or one or more silicon alloys of at least 70 percent silicon content as an energizer component, and which are characterized by improved safety in manufacture and handling, and stability to segregation of the silicon particles.

Inorganic oxidizer salt blasting agents, or compositions, of the nonaqueous type, contain an inorganic oxidizer salt, generally ammonium nitrate, as a chief ingredient along with a suitable fuel or energizer such as one or more of aluminum, coal, a hydrocarbon oil, a monoor dinitrotoluene, and the like. Inasmuch as fuel or energizer components of these blasting agents generally impart an increase in sensitivity they are often also referred to as sensitizers.

The above described blasting agents are of two well known types, viz nitrocarbonitrate and ammonium nitrate-fuel oil, and are often referred to in the art as NCNs and ANFOs, respectively. The ammonium nitrate-fuel oil type, in addition to the inorganic oxidizer salt, contains a small proportion of a hydrocarbon oil and, often, a small proportion of particulate aluminum or an aluminummagnesium alloy as an additional fuel, or energizer; and the nitrocarbonitrate type contains, in addition to the inorganic oxidizer salt, an energizer such as a monoor dinitro-toluene, particulate coal, finely divided aluminum, and the like.

These blasting agents are free from ingredients which, per se, are high explosives. The NCNs, and generally the ANFOs, are insensitive to detonating action of a commercial No. 8 blasting cap, but are, in all events, readily detonated in response to detonating action of a conventional booster type charge such as PETN, pentolite, tetryl and the like.

Although aluminum has been utilized in the above described inorganic oxidizer salt blasting agents for some time, the handling of aluminum during manufacture is hazardous, and often the sensitivity of the resulting blasting agent product is increased to the extent that it requires especially careful handling during storage and shipping even though it is insensitive to detonating action of a No. 8 electric blasting cap. Further, particulate aluminum as generally utilized, readily segregates from the remaining blasting agent ingredients during storage, particularly when the oxidizer salt is in prilled form, which of course contributes to composition nonuniformity and unreliable performance of the blasting agent.

This invention is concerned with inorganic oxidizer salt 3,455,750 Patented July 15, 1969 blasting agents of the nonaqueous type which contain a novel metal energizer, or fuel, ingredient, and which are of substantially the same explosive strength as those blasting agents containing aluminum, but are characterized by lower sensitivity and hence greater safety in manufacture and handling, greater static resistance, and greater resistance to settling of the metal ingredient.

In accordance with the invention nonaqueous inorganic oxidizer salt blasting agents of the nitrocarbonitrate type are provided which contain, as an energizer, from 2 to 18 weight percent of a particulate silicon component substantially all of which will pass through a 30 mesh U.S. standard sieve and selected from the group consisting of silicon, at least one silicon-metal alloy having a silicon content of at least 70 weight percent, and a mixture of silicon and at least one said alloy.

Generally the blasting agents of the invention contain on a weight basis from about 78 to about 98 percent, preferably not more than about 92 percent, of inorganic oxidizer salt, from about 1 to about 8, preferably 2 to 5 percent, of a carbonaceous fuel component and the particulate silicon component, as above described. Often the particulate silicon component is an alloy of at least percent silicon content with at least percent passing through a U.S. mesh screen. Preferred silicon component contents of the now preferred compositions are often advantageously in the order of from 6 to 15 weight percent. In some instances, limited proportions of particulate aluminum are advantageously utilized as a supplement to the silicon component, say in a weight ratio thereto up to about 1:1, the particulate aluminum being present in the finished blasting agent composition in an amount not exceeding about 5 weight percent.

By the term inorganic oxidizer salt as is well known in the art, is meant one which under the conditions of the detonation supplies oxygen for the oxygen balance required. Ammonium nitrate is in many instances the only oxygen-supplying salt component. However, other inorganic oxygen supplying salts can be utilized alone or with ammonium nitrate as a supplementary oxidizer salt. Of these, the alkali metal nitrates, generally sodium nitrate, are now preferred and, as a supplementary inorganic oxidizer salt, are present in the finished composition in an ammonium nitrate to sodium nitrate weight ratio of from 4:1 to 03:1. Exemplary oxygen supplying salts that can be used alone or together with ammonium nitrate as supplementary oxidizer salts are alkali metal and alkaline earth metal nitrates, and perchlorates (including ammonium) as for example sodium nitrate, magnesium nitrate, calcium nitrate, potassium nitrate, barium nitrate, sodium perchlorate, ammonium perchlorate, calcium perchlorate and magnesium perchlorate.

Particle size of the inorganic oxidizer salt ingredients is not critical. For example, ammonium nitrate can consist of prills, or it can be granular and in that form vary from coarse to fine. Other inorganic oxidizer salt ingredients are generally of comparable particle size.

The NCN and ANFO blasting agents of the invention contain at least one carbonaceous fuel component in addition to the inorganic oxidizer salt and the silicon component as an energizer (or fuel), and they often also contain an additional suitable supplementary fuel component, preferably a carbonaceous fuel and/or a particulate metal. Further exemplary of suitable fuel components are sulfur, gilsonite, finely divided coal, monoand di-nitrated hydrocarbons, e.g. DNT and MNT, ethylene glycol, ordinary granuated sugar, paraffin wax, nitroparaffins, hydrocarbon fuel oils, particulate aluminum, and the like. Of the various carbonaceous fuel components, hydrocarbon fuel oils and monoand di-nitrotoluenes are among those particularly preferred.

The particulate silicon energizer component of the blasting agents of the invention can be selected from a broad range of commercially available grades to permit the use of not only substantially pure silicon but a choice of silicon from a number of silicon alloys and alloy blends.

Silicon content of the silicon component, in accordance with the invention, is at least 70 percent and preferably in the order of 85 percent and higher. Exemplary, and typical, particle size distribution and compositions of now preferred silicon components in practice of the invention, are shown in Table I.

TABLE I.PAR'IICLE SIZES AND COMPOSITION Silicon Component Type I II III 1 Through 200 65. 0 82 percent smaller than 74 microns.

Through 325 2.0 39 percent smaller than 44 microns.

TYPICAL ASSAY OF SILICON COMPONENT Types I and III Type II Percent Silicon 1 Sharples Micromerograph" particle size distribution analysis.

Silicon component types I and III are silicon alloys containing 95 to 97 percent silicon and having a range analysis of major residual elements bound in the alloy as follows:

The blasting compositions of the invention are further illustrated with reference to the following examples.

Examples 1-4 Two blasting agent compositions (Examples 2 and 4) of the invention were formulated and each tested for sensitivity in terms of minimum size booster required for initiation, and two additional and corresponding blasting compositions (Examples 1 and 3) containing aluminum in place of silicon, were tested for comparative purposes. The data summarizing these tests are summarized in Table II.

TABLE II Minimum Booster For Initiation Formulation, Weight Percent Army Cap 6 Detonation Ammonium Fuel Density, or Pentolite Rate, Example Nitrate 1 Metal oil 2 gins/cc. (grams) m./sec.

89 7A1 4 0.88 Army ca 3,300 89 7 Si 4 0. 81 Pentolite (l0) 3, 550 92. 7 7.3 A1 0 0. 84 Pentolite 2, 800 92. 7 7.3 Si 0 0. 86 Pentolite(160) 3, 350

IrillsNone on 6 mesh, 5 percent (max.) on 8 mesh, 2 percent (main) through 20 mesh.

2 No. 2 fuel oil.

Aluminum90 percent minimum Al content, 90 percent through 30 mesh.

'* Type II of Table I, containing 85 weight percent silicon.

5 Measured as average detonation velocity of a. 20 cm. length at the end of column of explosive. The explosive is confined in a 5 x 28 black n 28" ion iron pipe Schedule 40). The time for detonation to proceed across the 20 cm.

length of explosive is measured electronically by means of a counterchrono- Silicon component type II is a preferred material due to its ability to enter the explosive reaction and its economy. Type II is a silicon alloy blend averaging about 85 percent silicon, with a nominal silicon range of 82 to 88 percent. The range analysis of major residual elements bound in the alloy is as follows:

Percent Aluminum .701.25 Calcium .35.60 Carbon .10.15 Chromium .20-.30 Copper .03-.08 Magnesium .02.05 Molybdenum .01-.04 Nickel .04-.08 Phosphorous .01.03 Titanium .08.l2

Manganese .05-.15 Iron Balance raph.

B 1.87 times the detonating strength of a No. 8 blasting cap.

Examples 1 and 2 illustrate ammonium nitrate-fuel oilsilicon blasting compositions of the invention and their sensitivity which is markedly lower than that when the composition contains aluminum in lieu of silicon. Similarly, Examples 3 and 4 illustrate ammonium nitratesilicon blasting compositions of the invention containing no supplemental fuel and of lower sensitivity than corresponding ammonium nitrate-aluminum blasting compositions. The blasting compositions of the invention containing silicon are of lower sensitivity and are thus safer to handle during storage and shipping than are corresponding blasting compositions containing aluminum in accordance with convention practice.

Examples 5-10 Examples 5-10, summarized in Table III, further demonstrate the sensitivity of blasting compositions of the invention to be lower than that of compositions conventionally containing particulate aluminum as the metal component. The procedure of each example was carried out by loading a metal container 3%" ID. X 4%" ht. with 250 grams of the composition, and at the temperature shown was subjected to the impact of a 220 caliber swift, 48 grain, soft point bullet fired at a distance of 100 feet.

6 Example 13 It is often advantageous to supplement the silicon energizer component of the compositions of the invention with particulate aluminum, preferably not in an amount TABLE III Formulation, Weight Percent Ammonium (Per- Temp., Ex. Nitrate 1 cent) Oil 2 F. Result Comment 5 94 O 63 No reaction Except for bullet hole the container was unchanged. 6 94 6 Same as for Ex. 1.

7 89 7 Al 4 Container blown into two sections. 8 89 7 Al 3 4 Container blown into four sections.

9 89 7 Si 4 60 Very slight, if any, Except for bullet hole, container reaction. substantially unchanged.

l0 89 7 Si 4 150 do Do.

For footnotes (1), (2), (3) and (4) see Table II.

Examples -10 demonstrate the low sensitivity imparted to ammonium nitrate fuel oil blasting agents by the presence of the particulate silicon as compared with the markedly higher sensitivity imparted by the conventional presence of particulate aluminum in an ammonium nitrate-metal blasting composition.

Examples 11 and 12 Examples 11 and 12 in Table IV demonstrate that as to energy content, blasting compositions of the invention are substantially equivalent to corresponding compositions containing particulate aluminum in lieu of silicon. In carrying out the tests, summarized in Table IV, a blasting composition of the invention was formulated and tested for energy content and the corresponding aluminum-containing composition was subjected to the same tests for comparison. Three samples of each formulation were tested for detonation rate and for explosive energy while confined under water in a standard schedule 40 steel 3" ID. x 28" in length pipe, in accordance with procedure of Cole (Cole, H. C., Underwater Explosions, Princeton University Press, Princeton, NJ. (1948), pages 228 to 285) and Sadwin (Sadwin, L. D., Cooley, C. M., Porter, S. 1., Stresau, R. H.; Underwater Evaluation of the Performance of Explosions, International Symposium on Mining Research, Missouri, February 1961, vol 1). The pipes were suspended vertically feet below the surface of the water, approximately 11 feet from the bottom of the water body. The charges were initiated from the bottom with commercial pentolite boosters conr taining 340 grams pentolite. The pressure generated by each detonation was transformed by a piezoelectric hydrophone transducer into voltage impulses which were displayed on an oscilloscope. The bubble times were recorded on a counter chronograph. The voltage amplitude was calibrated in p.s.i. units by testing an appropriate pentolite charge. The bubble time was calibrated in energy units by testing a 60 percent high, pressure gelatin dynamite charge. Detonation rates were measured over Footnotes 14, see Table II.

of aluminum exceeding about 5 weight percent of the total blasting composition, as illustrated with reference to the data summarized in the following tabulation.

TABLE V Formulation, weight percent: Example 13 Ammonium nitrate 81 DNT 5 Aluminum 5 Silicon 9 Detonation rate, m./s. 3150 Booster charge, grams pentolite 21 Footnotes 1, 3, 4, 5, see Table II.

The blasting compositions of the invention can be prepared in accordance with any suitable mixing procedure. In one such preparation, the inorganic oxidizer salt, often solely ammonium nitrate is introduced into a mixing zone, followed by addition of the silicon ingredient with initiation of mixing action of the two ingredients. The carbonaceous fuel, is advantageously added to the inorganic oxidizer salt under mixing conditions prior to the addition of the silicon component.

The explosives art has in recent years stressed the use of prilled ammonium nitrate hydrocarbon fuel oil mixtures in numerous applications, and the use of particulate aluminum as an energizer component has oftentimes been unsatisfactory due to the settling, or separation, of the aluminum particles from the voids in the mass of prills. However, it has been discovered that surprisingly, silicon component particles in the NCN and ANFO compositions of the invention containing ammonium nitrate in prilled form, do not separate therefrom. They appear to cling to the prills to prevent segregation and hence provide compositions of unexpected uniformity in composition and performance.

Example 14 Safety in manufacture of the blasing compositions of the invention in respect of handling of the silicon ingredient is illustrated with reference to the results of flammability tests of particulate aluminum of various paricle sizes utilized heretofore in nonaqueous ANFO and NCN type blasting compositions, and particulate silicon of the compositions of the invention. Each test, summarized in the following tabulation, was conducted by dropping approximately grams of sample, a distance of 16 inches down an 8 inch diameter tube, ventilated at the bottom and open at the top while simultaneously initiating a commercial electric squib at a point about midway' along the 16 inch column.

7 TABLE VI Paint grade aluminum (97 percent, 74 microns; 6 percent, 44

microns) Flash-6 to 8 feet high. Aluminum (400 mesh) Flash1 foot. Aluminum (200 mesh) Flash4 feet. Silicon No flash.

For foo note 4, see Table II.

As shown, the particulate silicon did not fiash, whereas the three particulate aluminums flashed thus demonstrating the much greater degree in safety in manufacture and handling of the compositions of the invention imparted by the silicon component, i.e. than is accomplished in the manufacture of the conventional nonaqueous aluminumammonium nitrate blasting compositions.

In preferred practice, the ANFO and NCN type blasting agents of the invention each contain, on a weight basis, from 78 to 92 percent inorganic oxidizer salt and 1 to 8 percent of the carbonaceous fuel, together with the defined silicon energizer component; and in more specific embodiments they contain as the silicon energizer component a silicon-metal alloy having a silicon content in the order of at least about 85 percent and a particle size such that at least about 90 percent will pass through a No. 2 100 mesh U.S. standard sieve. Preferred ANFOs contain a hydrocarbon fuel oil as the carbonaceous ingredient, present in the order of from about 2 to 5 percent; and preferred NCNs contain DNT and/ or MNT as the carbonaceous fuel ingredient, also in a preferred amount of from 2 to 5 percent.

As will be evident to those skilled in the art, various modifications can be made or followed, in light of the foregoing disclosure and discussion, without departing from the spirit or scope of the disclosure or from the scope of the claims.

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

1. In a nonaqueous blasting agent of the nitrocarbonitrate type insensitive to detonating action of a No. 8 blasting cap, wherein the oxidizer is an inorganic oxidizer salt and the fuel is a carbonaceous material, the improvement comprising, as a metal energizer ingredient thereof, from 2 to 18 weight percent of a particulate silicon component substantially all of which will pass through a 30 mesh U.S. standard sieve and selected from the group consisting of silicon, at least one silicon-metal alloy having a silicon content of at least 70 weight percent, and a mixture of silicon and at least one said alloy.

2. A blasting agent of claim 1 containing from 78 to 98 Weight percent of said inorganic oxidizer salt.

3. A blasting agent of claim 2 containing from 1 to 8 weight percent of said carbonaceous fuel component.

4. In a blasting agent of claim 3, a silicon-metal alloy containing at least about 85 weight percent silicon and having a particle size such that at least about 90 percent will pass through a 100 mesh U.S. standard sieve, as said silicon component.

5. A blasting agent of claim 4 containing from 6 to weight percent of said silicon component.

6. A blasting agent of claim 3 containing not more than about 5 weight percent particulate aluminum in a weight ratio to said silicon component not exceeding 1:1.

7. A blasting agent of claim 3 containing prilled ammonium nitrate as at least a portion of said inorganic oxidizer salt.

8. A blasting agent of claim 3 wherein said inorganic oxidizer salt is selected from the group consisting of ammonium nitrate and a mixture of ammonium nitrate and sodium nitrate in an ammonium nitrate to sodium nitrate weigh tratio of from 4:1 0 0.321.

9. A blasting agent of claim 3 of the ammonium nitrate-fuel oil type and containing, on a weight basis, from 78 to 92 percent of said inorganic oxidizer salt, and from 1 to 8 percent of a hydrocarbon fuel oil as said carbonaceous fuel.

10. A blasting agent of claim 9 containing ammonium nitrate as at least a major portion of said inorganic oxidizer salt, from 2 to 5 percent of a No. 2 hydrocarbon fuel oil, and a silicon-metal alloy of at least percent silicon content and of particle size such that at least about percent will pass through a 100 mesh U.S. standard sieve.

11. A blasting agent of claim 10 wherein said inorganic oxidizer salt is ammonium nitrate together with sodium nitrate in an ammonium nitrate to sodium nitrate weight ratio within the range of 4:1 to 0.3: 1.

12. A blasting agent of claim 3 of the nitrocarbonitrate type containing ammonium nitrate as at least a major portion of said inorganic oxidizer salt, and a nitrotoluene selected from the group consisting of monoand dinitro-toluenes, as said carbonaceous fuel.

13. In a blasting agent of claim 12 a silicon-metal alloy of at least about 85 percent silicon content and of particle size such that at least about 90 percent will pass through a 100 mesh U.S. standard sieve, as said silicon component.

14. A blasting agent of claim 1 wherein said inorganic oxidizer salt is sodium nitrate.

15. A blasting agent of claim 1 wherein said silicon component is a silicon-metal alloy containing from 82 to 88 weight percent silicon.

16. A blasting agent of claim 1 wherein said silicon component is a silicon-metal alloy containing from to 97 percent silicon.

17. A blasting agent of claim 1 wherein said silicon component is substantially pure silicon.

References Cited UNITED STATES PATENTS 2,586,959 2/1952 Kerr et a1. l4937 X 2,643,946 6/1953 McLain et a1 14937 X 3,347,721 10/1967 Jago 14937 X 3,374,127 3/1968 Jenner et al 14938 X 3,390,028 6/1968 Fee et a1 149-89 BENJAMIN R. PADGETT, Primary Examiner S. J. LECHERT, Assistant Examiner U.S. Cl. X.R.