US3113060A

US3113060A - Ammonium nitrate-fuel oil blasting agent containing triethylene glycol dinitrate

Info

Publication number: US3113060A
Application number: US153702A
Authority: US
Inventors: Robert A Cooley
Original assignee: Chromalloy Corp
Current assignee: Chromalloy Corp
Priority date: 1961-11-20
Filing date: 1961-11-20
Publication date: 1963-12-03
Anticipated expiration: 1980-12-03

Description

United States Patent 3,113,060 AMMONIUM NlTRATE-FUEL GIL BLASTING AGENT CONTAINING TRIETHYLENE GLY- CQL DINITRATE Robert A. Cooley, Rosewood Heights, Ill., assignor to Chromalloy Corporation, Edwardsville, lil., a corporation of New York No Drawing. Filed Nov. 20, 1961, Ser. No. 153,702 3 Claims. (Cl. 149-47) The invention relates generally to a blasting agent and more specifically to blasting compositions of the type generally used in quarries, mines, construction and industrial blasting whether it is of the surface or underground type. Ammonium nitrate blasting agents are generally employed for the above-mentioned types of blasting. One of the more popular ammonium nitrate blasting agents is one wherein diesel fuel oil is absorbed by ammonium nitrate prills. The ammonium nitrate-diesel fuel oil (hereinafter called AN/FO) blasting agent has numerous advantageous characteristics, that is, it is one of the least expensive blasting agents commercially used and it is relatively insensitive to impact and therefore suitable for safe and low cost transportation. However, in some cases where the ammonium nitrate has been mixed with the diesel fuel oil, the resultant composition is not sufiiciently sensitive to detonation so that when used in a blast hole the detonation velocity achieved is lower than ideal or the material does not fully detonate. Similarly, it is generally known that all explosive materials can be characterized by a critical diameter below which a charge of this composition will not support detonation. The best quality AN/FO composition may very reliably suppont detonation, in a column two inches in diameter, but will be incapable of supporting detonation if the diameter of the charge is less than one inch.

/ Therefore, it is an object of the present invention to provide a blasting agent of the ammonium nitrate type which has a critical diameter below that of ordinary AN/tFO blasting agents.

Another object of the present invention is to provide a blasting agent that reliably achieves ideal detonation velocities without sacrificing any of the advantageous properties exhibited by AN/FO type agents.

Other objects will appear obvious to those skilled in the art from the following detailed description that is in such full, clear and concise terms that any person can make and use the same.

The blasting agent of the present invention is of the AN/FO type and consists essentially of ammonium nitrate, diesel fuel oil and triethylene glycol dinitrate (hereinafter referred to as TEGDN). Ammonium nitrate comprises the majority of the composition, while the diesel fuel oil and TEGDN are present in relatively small amounts.

The herein described blasting agents have all of the advantageous characteristics of the AN/FO compositions heretofore commercially used so extensively, While simultaneously having numerous advantageous characteristics not prevalent with AN/FO mixtures.

One of the most important advantages that is exhibited by the present composition is that it has a detonation velocity comparable to that of nitroglycerine and TNT, while simultaneously having a cost and safety fac.or comparable to AN/FO mixtures. Although AN/FO mixtures are extremely cheap when compared with the more expensive blasting agents, rtheir detonation velocity is not nearly as high. However, in order to use the less expensive safer blasting agents, consumers sacrifice the high detonation velocity and the smaller critical diameter of the charge. By the addition of a slight amount of TEGDN to the AN/FO blasting agents, a substantial increase in ice the detonation velocity is obtained. The detonation velocity ranges between 9800 to 11,0000 feet per second for an AN/FO mixture containing 94 percent whole prills and 6 percent fuel oil. An AN/FO mixture containing 47 percent whole prills and 47 percent ground prills plus 6 percent fuel oil, has a detonation velocity of 12,000 to 13,500 feet per second. When 2 percent by Weight of TEGDN is added to the 94/6 percent AN/FO mixture (forming a 93/ 5/2 mixture), the detonation velocity is increased to between about 12,800 to about 14,000 feet per second. With the addition of about 2 percent TEGDN to the 47/ 47/ 6 percent ammonium nitrate fuel oil mixture (forming a 46.5/46.5/5/2 mixture), an increase in the detonation velocity to between about 15,500 to about 17,000 feet per second is obtained. Since the power of an explosive is proportional to the square of the detonation velocity, incremental increases in velocity will result in appreciably better performance.

Detonation velocities of ammonium nitrate blasting agents are varied by the relative detonation velocity of the initiator, the cross-section density of the shot column, and the confinement of the material shot. By having a range of increased detonation velocities by the addition of TEGDN, over those offered by standard AN/FO mixtures, the mixtures of the present invention are better able to solve common blasting problems, such as: (a) T oe-out or breakage of the shot wall to base linenecessary on fixed excavations and desired for smooth operating floor in quarries and mines. (b) Complete breakage of shot face to depth of drill hole in underground mining and quarrying-most conventional explosives will leave a few feet of the horizontal drill hole. (0) Better fragmentation of harder or more dense rock formationsmore rock is of a crushable size eliminating secondary breakage. (d) drill hole spacing can be spreadcutting costs of drilling time, and the amount of blasting agent used per ton of rock broken.

AN/FO mixtures have a rather uniform density of between about 0.85 and 0.95 grams/cm. A composition containing 93 whole prills, 5% fuel oil and 2% TEGDN has a density of about .84 grams/cm. and represents the lower end of the gamut of densities obtained from the compositions of the present invention. At the other extremity is a composition containing 46.5% whole prills, 46.5 ground prills, 5% fuel oil and 2% TEGDN which has a density of about 1.2 grants/emf. The preferred charge density is dependent upon a variety of factors: The cross-section diameter of the drill hole-smaller the hole the greater the load density preferred; relative density of material being shotgreater load density for harder rock; and, when blasting dry or wet drill holes, filled with water, a density of greater than 1.0 is preferred so that the packaged material will sink to the bottom of the water-filled hole. Bulk loading densities, using the above extremities, of from 52 to 68 pounds per cubic foot can be obtained. This range satisfies the variation of conditions most often found in the field. Having various densities to choose from, enables the critical diameter of the charge to be changed, thus a lower critical diameter, as Well as a more ideal detonation velocity, for the charge can be obtained.

The following examples are representative of the compositions Within the purview of the present invention.

Example I 46.5 grams of whole ammonium nitrate prills are thoroughly mixed in a mixing chamber with 46.5 grams of ground ammonium nitrate prills. These dry ingredients are allowed to blend within the mixing chamber for about 10-15 minutes. 5 grams of #2 fuel oil are thoroughly mixed with 2 grams of TEGDN and the liquid is then 1'3 added to the mixing chamber and thoroughly mixed with the ammonium nitrate for a period of about 20 minutes.

Example 11 Two grams of #2 diesel fuel oil is mixed with 10 grams of TEGDN. The resulting liquid mixture is added to 188 grams of ammonium nitrate prills (Spencer N4 or Monsanto CD) in a rotary blender and allowed to remain therein until thorough mixing has been accomplished. This explosive composition is especially suitable for cartridges in the order of one inch in diameter, and has a comparable detonation velocity with a dynamite stick of the same size. However, although it has a similar det onation velocity, it is much more insensitive to impact than is the dynamite stick, and thus affords a safety factor when being used.

Example [II To 93 grams of ammonium nitrate whole prills are added a mixture of 5 grams #2 fuel oil and 2 grams TEGDN, and the ingredients are thoroughly mixed in a mixing chamber for about to minutes.

The ammonium nitrate prills used in the present invention have particle sizes as follows:

Percent Whole prill AN:

Minus 6 mesh USSS 100 Plus 18 mesh USSS 99.5 Ground prill AN:

Plus 20 mesh USSS 10 Minus 20 plus 100 70 Minus 100 20 The above recited figures represent the preferred particle size of the ammonium nitrate, but in no way is that recitation intended to limit the invention.

The fuel oil that is commonly used to sensitize the ammonium nitrate is No. 2 diesel fuel oil, but any other desirable and satisfactory oil may also be used.

Due to the high performance of TEGDN, it is believed that some type of absorption occurs which makes it ideal to be mixed with ammonium nitrate. Any organic nitrate might improve ammonium nitrate as a blasting agent, but not all organic nitrates have the right molecular configuration to supply a fuel moiety and a nitrate oxidizer moiety which, in combination with ammonium nitrate crystal structure or physical properties, have ideal characteristics. TEGDN has three sets of ethylene groups and two oxygen bridges as well as two nitrate groups as can be seen from the following structural for- This proportionethylene groups to oxygen bridges to nitrate groups-is believed to be ideal to achieve the most favorable absorption of the fuel moiety into the ammonium nitrate crystals, and leave the nitrate moiety from the TEGDN unabsorbed, but in an ideal state to decrease the critical diameter of the explosive.

The amount of TEGDN present in the formulation is dependent upon the desired characteristics of the blasting agent. However, I have found that the preferable range of TEGDN present is between about 1.5 to about 5 percent by weight of the total composition.

Other glycol dinitrates are entirely unsatisfactory for this purpose because the carbon chain or fuel moiety of the molecules separating the nitrate groups is either shorter or longer than that of TEGDN, thus, not producing the desired characteristics exhibited by the triethylene glycol dinitrate.

Although higher detonation velocities, lower critical charge diameters, variable densities, etc., can be obtained from the compositions of the present invention, their relative sensitivity does not differ from that of standard AN/FO mixtures. A 24" length of grain detonating cord stretch on the ground did not detonate either standard AN/FO or AN/FO/TEGDN compositions within the purview of the present invention, while 40% extra dynamite was detonated Thus, the relative insensitivity of the AN/FO/TEGDN mixtures can readily be seen and their advantages realized by those skilled in the art.

Many changes in and modifications of the present invention may be made without departing from the spirit of my invention or sacrificing any of its advantages.

Having thus described the invention, what is claimed and desired to be secured by Letters Patent is:

1. A blasting composition consisting essentially of ammonium nitrate, diesel fuel oil and triethylene glycol dinitrate, wherein the said ammonium nitrate accounts for the majority of the composition.

2. The blasting composition of claim 1 wherein the ammonium nitrate is present as ammonium nitrate prills.

3. A blasting composition consisting essentially of ammonium nitrate prills, ground ammonium nitrate, fuel oil and triethylene glycol dinitrate, wherein the said ammonium nitrates comprises a major portion of composition.

References Cited in the file of this patent UNITED STATES PATENTS 2,997,378 Cox et al Aug. 22, 1961 OTHER REFERENCES Military Explosives, Depts. of the Army and the Air Force, TM 9-1910; TO 11A-l-34, April 1955, pp. 215- 216.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,113,060 December 3, 1963 Robert A. Cooley It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 2, line 2, for "11,0000" read ll O00 Signed and sealed this 26th day of May 1964.

(SEAL) Attest:

ERNEST W. SWIDER EDWARD J. BRENNER Attesting Officer Commissioner of Patents