US3834954A - Process for the production of a waterbearing explosive composition - Google Patents

Abstract

A PROCESS FOR THE PRODUCTION OF A WATER-BEARING EXPLOSIVE COMPOSITION, WHEREIN A PREVIOUSLY PREPARED, THICKENED SOLUTION OR DISPERSION SUBSTANTIALLY COMPRISING THE OXIDIZING COMPONENTS OF THE EXPLOSIVE COMPOSITION, IS MIXED WITH THE COMBUSTIBLE OR OXYGEN CONSUMING COMPONENTS OF THE EXPLOSIVE COMPOSITION, CHARACTERIZED THEREIN THAT ALSO THE OXYGEN CONSUMING COMPONENTS ARE USED IN THE FORM OF A VISCOUS OR THICKENED SOLUTION OR DISPERSION HAVING NEARLY THE SAME CONSISTENCY AS THE OXIDIZING COMPONENT MIXTURE.

Description

" United States Patent 3,834,954 PROCESS FOR THE PRODUCTION OF A WATER- BEARING EXPLOSIVE COMPOSITION Eirik Samuelsen, Lierbyen, Norway, assignor to Dyno Induslrier A.S., Oslo, Norway No Drawing. Filed Mar. 2, 1972, Ser. No. 231,376 Claims priority, application Norway, Mar. 10, 1971, 907

Int. Cl. C06b 1/04 US. Cl. 149-2 11 Claims ABSTRACT OF THE DISCLOSURE The present invention relates to the production of explosives which comprise a water-bearing mixture of oxidizing salts and fuel components of various kinds, constituting a viscous dispersion of solid particles in a thickened aqueous medium.

At present, explosives of the stated nature are produced in two clearly different ways, viz., either in a manufacturing plant production of the complete explosive composition, which not till after a contingent storage and subsequent transport to the blasting site is placed in the borehole, or in the way that the components of the explosive, optionally in the form of certain premixtures or prepared solutions, are mixed on the site immediately in connection with the pumping of the explosive into the bore-holes.

The first mentioned method comprises the practice of preparing loading units, cartridges, preferably in plastic tubing, of dimensions adapted to the bore-holes in which they are to be used, as well as the practice of storing and transporting the material in essentially larger units or transport containers, from which the explosive is unloaded or pumped into the bore-holes.

This method is advantageous in that the composition of the explosive and the specifications thereof may be supervised more readily and be checked before use. A certain disadvantage consists therein that during storage the explosive may be subject to changes in an unfavourable direction that concerns its blasting qualities as well as its consistency. The latter may be of essential importance to a rational and proper operation of the pumping and loading on the place of use. Another disadvantage of the manufacturing plant production method is that the entire amount of explosive is present as a detonating explosive during storage and transport, with the corresponding safety rules.

The second method generally has the distinct advantage that during transport and storage no complete detonating explosive exists, since this is established only in the immediate vicinity of the bore-holes in which to be used, and immediately before it is loaded therein. This is entirely the fact when none of the components has any explosive character per se, and even if that is the case, the amount thereof, being subject to specific transporting and storing restrictions, will be substantially less than if the first mentioned method comprising plant production had been used.

However, the last mentioned method, comprising production on the site, has the disadvantage that the composition of the explosive and consequently its properties, is dependent on a carefully and accurately performed metering and mixing operation on the site. Up to now the 3,834,954 Patented Sept. 10, 1974 method has been characterized therein that at least one of the flow of materials to the mixing operation has been a particulate solid material, mostly the fuel components of the explosive, and often also a part of the oxidizing salts, preferably ammonium nitrate has been fed to the mixing operation as a solid substance. The other quantities of salts and other water soluble components of the explosive then have constituted a solution which is included in the mixing operation as a readily pumpable flow of material.

It is not easy to perform an accurate metering of dry components in strictly specified ratios into a flow of liquid. It is particularly difficult when the dry components are very finely pulverized, as in that case both their bulk densities and flow properties are strongly dependent on the air content of the particulate material as well as of the other properties of the powder particles. Especially for explosives of the herein disclosed nature it is of great importance that the dry components are very finely pulverised, and it has often been necessary to take different measures, such as vibrating of hopperwalls, mechanical agitating devices inside the hoppers, or blowing air into the hoppers to counteract failure in the feeding of the dry components through screw conveyors or other metering devices. Under unfavourable conditions, such as high humidity in the air or high temperature, the particulate material has demonstrated such a tendency to sintering and formation of lumps that even the measures mentioned above have not been able to ensure the required result in metering the material.

The object of the present invention is to obtain the advantage of the last mentioned method as far as concerns the final explosive to be established immediately before use on the site, at the same time as the disadvantages of handling and accurate metering of the dry particulate components are eliminated.

The invention consists therein that the nature and amount of the components of the explosive are selected such that it may be prepared at the place of use by simple mixing of two in principle liquid, viscous or pasty, volumetrically readily metered component mixtures, the one of which in a per se known way essentially comprises an aqueous solution or dispersion of oxidizing salts, the second component mixture essentially comprising the fuel components.

The essential feature of the invention, thus, consists in letting the fuel components of the explosive be introduced into the final mixing operation in a pumpable form. In such a viscous or pasty component mixture a liquid phase should be included which is mixable with the salt solution constituting the liquid phase of the other pumpable component mixture. As a suitable dispergent medium for different solid fuel components several liquid media have been found, having in common that they consist entirely or substantially of combustible materials, and that they have a relatively high viscosity which prevents insoluble fuel particles from sedimentation. As examples of such suitable dispersing liquids for solid fuel components may be mentioned ethyleneglycol thickened with small amounts of specific thickening agents, such as Polyhall, Grade 295, supplied by the firm Mayhall, Switzerland or Kelsan, supplied by Kelco C0,, U.S.A. and, further, molasses and evaporated sulfite liquor from a sulfite pulping process.

Among the combustible components to be dispersed in such a liquid there must generally be at least one to provide the final explosive mixture with a necessary degree of sensitivity toward initiation. Of such sensitizing agents primarily either a solid substance having explosive character, preferably trinitro toluene, or finely divided, preferably flaked aluminium comes into question. It is a feature of the invention that the initiability of these sensitizing agents will be considerably reduced by being dispersed in a liquid phase, while they are, however, provid ing the final explosive mixture in which also the oxidizing salts are present, with a sufficient sensitivity towards initiation.

In addition to these sensitizing agents the viscous or pasty component mixture may comprise various other combustible substances, which by taking part in the reaction contribute to the generation of heat and combustion gases. One group of such combustible substances comprises powders of coal, asphalt, pitch, peat, wood, cork, bark, and the like, another group comprising powders of metals such as aluminium, magnesium, silicon, boron or alloys thereof.

Beside these components which constitute essential constituents of the final explosive, the fuel component mixture as well as the mixture of the oxidizing salts may comprise constituents which influence or stabilize the consistency of both component mixtures or of the final explosive composition, such as, e.g., thickening agents and crosslinking agents for these thickening agents, or, which influence or stabilize the content of dispersed air in the mixtures, such as dispersing agents or other surfactant agents. Such substances may also be introduced separately during the final mixing operation, in case this is found advantageous.

In the practice of the present invention it is of importance, primarily, to perform an accurate metering of both component mixtures, and, secondarily, a thorough blending thereof.

It is a feature of the invention that the volumetric metering of the component mixtures is far more easy to perform accurately and reproducibly than metering of dry components as practiced previously. As a suitable pumping means, preferably, gear pumps of different design will come into question. Moreover, a preferred means is an arrangement in which two gear pumps, one for each of the component mixtures, are driven by the same motor, and wherein the ratio between the speeds of the pumps may be varied for controlling the required mixing ratio, while the production rate of the final explosive may be varied by means of a speed variator for the motor in common. An alternative arrangement consists in pumping one component mixture with varying speed, allowing a flow meter in this flow of material to control the pump speed in the second fiow of material in an adjustable, though stable condition under varying pump speeds. Such arrangements are suitable both for the maintenance of the correct composition of the explosive and for adapting the production rate of the loading operation and other conditions on the site.

Irrespective of the pumping means being selected for an accurate and stable metering of both component mixtures in a determined ratio, the final mixing of these two materials must be completed before the explosive is introduced into the bore hole. This final mixing may be facilitated by suitable construction of the part where the flows of material are combined, e.g., by causing one flow of material to flow through a nozzle having a large number of openings, into the second flow of material. After this combination of the component mixtures they should be thoroughly blended. This may be achieved by means of mechanically operated mixing means, such as paddles or stirring blades operating in a mixing chamber, but a preferred embodiment of this mixing operation comprises the use of a so called static mixer, in which the total flow of material is split up and caused to change direction several times, only as a consequence of the flow movement in the two component mixtures originally effected by the pumps.

Irrespective of the mixing technique used, it has been found suitable that the two component mixtures are of substantially the same viscosity or consistency, thereby reducing essentially the risk that one of the component mixtures be present as non-dispersed lumps or local inhomogenities in the remaining mixture.

In the following there will be given an example of an emobidment of the invention, however, it will ppear from the foregoing that the invention is not limited to this example, but that it includes every production of aqueous explosives in which two viscous or pasty component mixtures are combined to form the final explosives.

EXAMPLE 1 Component mixture A A viscous up to pasty dispersion of oxiding salts is prepared having the following composition, in parts by weight:

Parts Ammonium nitrate 40 Nitrate of lime, fertilizer grade 45 Sodium nitrates 4 Urea 5 Water 4 Ethylene glycol 1.5 Tapioca starch 0.4 Guar Gum 0.1

Total 100.0

Remark: The nitrate of lime used contains about 79% calcium nitrate, 6% ammonium nitrate and 15% water.

The first five components are heated under stirring to about 65 C., whereafter the two last mentioned components, the thickening agents, are dispersed in the ethylene glycol and added to the salt solution. Cooling under stirring causes initial salt precipitation at about 30 C., whereas the component mixture maintains its pumpability and character of a viscous dispersion down to between 10 C. and 20 C. By decomposition, this component mixture will during detonation place about 210 grams of oxygen per kilogram, at the disposal for the combustion of other substances.

Component mixture B A viscous mixture of combustible components are produced having the following composition, in parts by weight:

Parts Ethylene glycol 72.2 Thickening agent Polyhall 295 0.4 Aluminium, flake form 18.0 Asphalt powder 9.4

Total 100.0

The thickening agent is dispersed in the glycol, which is heated to about 80 C., thereby producing a clear solution which after cooling has a viscosity of about 2000 cps. -In this solution the two last mentioned components are then dispersed. This component mixture needs about 1400 grams of oxygen per kilogram for complete combustion.

Preparation of the explosive When admixing 87 parts component mixture A, and 13 parts component mixture B a substantially oxygen balanced explosive is obtained. During this mixing operation also 0.3 parts of a 50% sodium bichromate solution is added, which provokes a gel-like consistency and improved water resistancy of the explosive mixture.

EXAMPLE 2 Component mixture A In a similar way as set out in example 1 a mixture of the following composition was prepared:

Parts Ammonium nitrate 40.0 Nitrate of lime, fertilizer grade 43.3 Sodium nitrate 6.5 Water 6.5 Ethylene glycol 2.5 Tapioca starch 0.9 Guar gum 0.3

Total 100.0

This mixture will demonstrate initial salt precipitation at about 35 C., but may, however, be pumped at temperatures down to about 20 C. It provides about 235 grams of available oxygen per kilogram.

Component mixture B A viscous mixture of combustible components is prepared of the following composition:

Parts Evaporated SLllPfiiB liquor from an ammonium sulfite were added per kilogram of the above paste. The so produced paste will consume about 820 grams oxygen per kilogram for complete combustion.

Preparation of the explosive When admixing 77.5 parts of component mixture A, and 22.5 parts of component mixture B Total 100.0 parts,

a substantially oxygen balanced exposive is obtained.

Both of the here mentioned exposives will detonate completely in an about 75 mm. diameter charge column at about C. when initiating with a pentolite primer.

What is claimed is: 1. A process for producing a water-bearing exposive composition which comprises (a) preparing a viscous aqueous dispersion comprising water and the oxidizing components of the explosive composition,

(b) preparing a viscous dispersion of the oxygen consuming components of the explosive composition, containing as a major component a water-soluble combustible liquid and having a viscosity substantially the same as that of the dispersion prepared in step a, and

(c) pumping and mixing the dispersions with each other.

2. The process of claim 1 wherein the combustible liquid is ethylene glycol thickened with a high molecular weight compound so as to achieve a viscosity substantially preventing sedimentation of the solid substances dispersed therein.

3. The process of claim 1 wherein the combustible liquid is molasses.

4. The process of claim 1 wherein characterized in that in the component mixture comprising the combustible liquid is substances, an evaporated sulfite liquor from a sulfite pulping process.

5. The process of any of claim 1 wherein very finely divided aluminum is dispersed in the combustible liquid.

6. The process of claim 1 wherein an explosive substance is dispersed in the combustible liquid.

7. The process of claim 1 wherein at least one member selected from the group consisting of powdered coal, asphalt, pitch, peat, cork, bark, aluminium, magnesium, silicon and alloys of such metals is dispersed in the combustible liquid.

8. The process of claim 1 wherein the dispersions are mixed in a mixing ratio which results in a substantially oxygen balanced explosive composition.

9. The process of claim 6 wherein the explosive substance is trinitro toluene.

10. The process of claim 5 wherein the aluminum is used in the form of flakes.

11. The process of claim 8 wherein the oxidizing components are the nitrates of ammonia, sodium and calcium.

References Cited UNITED STATES PATENTS 3,153,606 10/1964 Breza et al 14944 X 3,160,538 12/1964 Zaslowsky et al 149--44 X 3,307,986 3/1967 Grant l49'44 X 3,312,578 4/1967 Craig et al 149-44 X 3,347,722 10/1967 Gordon 14944 X 3,356,544 12/1967 Fee et al 14944 X 3,377,909 4/1968 Grant et al 14944 X 3,467,559 9/ 1969 Paasch et al. 149--44 3,523,048 8/ 1970 Hopler 149-44 X 3,617,406 11/1971 Young 149-' 60 3,619,308 11/1971 Caldwell et al 149-60 STEPHEN J. LECHERT, J R., Primary Examiner US. Cl. X.R.