FI63011C - FREQUENCY REQUIREMENTS FOR THE PURPOSE OF SUSPENSION OF GELSUSPENSIONSSPRAENGAEMNE - Google Patents

Description

1 63011

Method for preparing an explosive of a non-detonating aqueous gel suspension type

Separated from Patent Application No. 760,613

Patent No. 61,469 5 Aqueous gel explosives, the chemical energy of which is mainly due to the thermal decomposition of ammonium nitrate, are widely used in rock mining, excavation and ore mining mainly because they are cheap and safe to handle. These explosives usually contain expensive suspended solid fuels and cannot be detonated with detonators, but considerably bristant additional charges are required to achieve effective detonation. There is a need for both cheaper non-detonator-sensitive explosives that do not contain any fuels or sensitizers, as well as explosives that can be placed and detonated in the same way as dynamite, but that are less expensive and less susceptible to accidental explosion. It has now been found that a number of aqueous gel explosives based on suspensions of ammonium nitrate can easily be prepared without the use of suspended solid fuels.

Jelly aqueous ammonium nitrate suspension explosives are known. Klima'n et al. U.S. Patent No. 3,676,236 discloses explosive compositions prepared from varying amounts of ammonium nitrate, sodium nitrate, ammonium perchlorate, hexamethylenetetramine, nitric acid, a finely divided solid fuel, a hydroxy-substituted thickener, and a crosslinking thickener. Previously known explosive compositions are particularly useful for placement in relatively large, long-spaced boreholes such as are commonly used in opencast mining of hard rock types. Explosives of this type are usually detonated by means of detonators and high-explosive charges.

It has now been found that non-detonators can be manufactured using the same materials as previously used, but without the need to include a finely divided solid fuel, ensuring that the proportions of the materials are kept within a narrow range by the following method: (a) preparation of the mother liquor; containing 26 to 36% by weight of water, 14 to 24% by weight of hexamethylenetetramine, ammonium nitrate in an amount of 5 to 15% by weight to 5% by weight of ammonium perchlorate and as much nitric acid as to saturate the solution so that the pH is obtained in the range of 4.0 to 6.5, and (b) 80 to 175 parts by weight of ammonium nitrate powder are added for every 100 parts of the mother liquor prepared in step (a) so that the total water content of the composition obtained is between 13 and 18% by weight together with a sufficient amount of polysaccharide rubber to thicken the mixture to gel consistency.

The preferred method for preparing the mother liquor in step (a) above is as follows:

Mix 15 to 40% by weight of an aqueous solution of hexamethylenetetramine with sufficient nitric acid to bring the pH to between 5.0 and 5.3 while adjusting the temperature of the resulting mixture so that it does not rise above 66 ° C to prepare an aqueous solution having a hexamethylenetetramine content of 25-35% by weight, then dissolved in a certain amount of this solution with sufficient ammonium perchlorate to a final concentration of 5.0-6.0%, sufficient sodium nitrate to give a final concentration of 8.0-9, 0% and sufficient ammonium nitrate so that the final concentration becomes 30-45%.

This mother liquor can then be preferably mixed with finely ground ammonium nitrate powder and a sufficient thickener to form a non-detonator-sensitive explosive gel in which ammonium nitrate is suspended.

30 The various stages of the method have critical features and, if deviated from significantly, can lead to failure. The critical features of each step are described below:

Step (a) 35 At the beginning of this step, an exothermic reaction occurs if the procedure is followed according to the examples. Initially, only water, hexamethylenetetramine and nitric acid, 3 63011, are preferably present so that the temperature and pH can be well adjusted. The upper temperature limit should be closely monitored to prevent decomposition due to side reaction. The temperature is preferably maintained between 50 and 60 ° C.

Since the dissolution of ammonium nitrate is an endothermic event, this can be accomplished more quickly and conveniently by introducing additional heat through a steam coil or other heat exchange device. During this step, enough heat is preferably introduced so that the final temperature in preparation for step (b) is 35-50 ° C.

10 Step (b)

The solution prepared in step (a) can be stored if desired and part of it can be used as a mother liquor for the preparation of various explosive products. However, it is more economical and more convenient to use this solution as it comes from step (a) before it cools down. The ammonium nitrate used at this stage should be finely ground and free of lumps. The combination of the polysaccharide gum and the crosslinking agent should be selected from those commercially available which cause the prepared suspension to gel. Some gums 20 do not form a sufficiently strong gel at the pH of this suspension (about 5.8-5.9).

The following examples illustrate the manufacture of various non-detonator-sensitive products.

Example 1 8 349 parts of water were placed in a clean reaction vessel equipped with a stirrer. To this was added 4,914 parts of solid hexamethylenetetramine powder while stirring, and stirring was continued until the solution formed.

To this solution was added 1,988 parts of nitric acid (69%: 30 ° C) while stirring and maintaining the temperature between about 45-60 ° C for the evolution of heat, continuing to stir after the reaction was completely stopped, as indicated by the pH: n invariance and temperature drop. At this point, the pH was measured at 5.1-5.3 at 38 ° C.

To this solution was then added 10,602 parts of spherical ammonium nitrate while stirring and heating the reactor with a steam jacket. While maintaining a temperature of nearly 50 ° C, 1,551 parts of ammonium perchlorate and 2,586 parts of sodium nitrate were also dissolved in the mixture. The properties of the finished solution, determined from several batches prepared as described above, were as follows: pH 5.8-5.9 5 3 specific gravity 1.34-1.35 g / cm

crystallization temperature -4 ° C

The solution described above was then used as the liquid phase to form the coagulated suspension described below at 38-49 ° C.

1960 parts of finely ground ammonium nitrate were placed in a mixing vessel and then a sufficient amount of the liquid described above was added while stirring to form a uniform and lump-free slurry. The remainder of the total amount of 2,000 parts of the liquid described above was added, followed by mixing with 40 parts of guar gum and crosslinking agent, which were added through the vacuum cleaners at such a rate that mixing was thorough and no lumps formed. The thickened suspension was allowed to reach gel consistency, which took about 20 to 10 minutes after the addition of guar gum was complete. The product comprised 4,000 parts by weight of a non-detonating aqueous gel suspension type explosive having a density of 1.20-1.25 g / an and a pH of 5.9-6.2. The% amounts of the various components in the finished mixture were as follows (to one decimal place): 25

Ingredients% by weight water 14.9 nitric acid 100%) 2.3 hexamethylenetetramine 8.2 ammonium nitrate in solution 17.7 30 ammonium perchlorate 2.6 sodium nitrate 4.3 ammonium nitrate (ground) 49.0

Guar gum (NGL 4 779, New, FP) (Stein-Hall) together with crosslinking agent x RO (x = potassium pyrantimonite) (Stein-Hall) 1.0% by weight 5 6301 1 1 '

Example 2

In step (a), a solution was prepared as in Example 1 from the following raw materials:% by weight of hexamethylenetetramine 15.3 5% water 30.6 nitric acid 6.5 ammonium perchlorate 5.1 sodium nitrate 8.5 ammonium nitrate 34.0 100.0% by weight 58 To 8 parts of the resulting solution were added 36.3 parts of finely ground ammonium nitrate and 0.9 parts of guar gum together with a crosslinking agent (Stein-Hall NGL4 779 New, FF together with a crosslinking agent RO) while stirring thoroughly.

^ 5 A non-detonating aqueous gel explosive with very good storage stability was obtained.

20 25 30 35

Claims (2)

6301 1 A process for preparing a non-sensitive water-based gel suspension explosive which does not contain any suspended solid fuel, characterized in that (a) a mother liquor containing 26 to 36% by weight of water, 14 to 24% by weight of hexamethylenetetramine, ammonium nitrate is prepared between an amount of 30% by weight and the amount required to saturate the solution, 8-9% by weight of sodium nitrate, 5-15% by weight of ammonium perchlorate and sufficient nitric acid to bring the pH to between 4.0 and -6.5, and (b) adding 80-175 parts of ammonium nitrate powder to each 100 parts batch of the mother liquor prepared in step (a) to bring the total water content of the mixture from 13 to 18% by weight and an amount of polysaccharide gum and crosslinking agent that thickens the mixture gel consistency. Non-tensile sensitive aqueous gel suspension explosive prepared by the process according to claim 1, characterized in that it contains 8.2% hexamethylenetetramine, 2.3% nitric acid, 66.7% ammonium nitrate, 4.3% sodium nitrate, 2.6% ammonium perchlorate, 1% guar gum and crosslinker, and water. 25 30 35