MXPA98005653A - Method for preventing sulphide powder explosions subsequent to detonacio - Google Patents

Abstract

Method to prevent sulfide dust explosions following detonation operations involving sulfur-containing minerals, this method involves (a) loading an explosion hole that has been drilled in a mining body containing sulphides with an emulsifying detonating agent containing an emulsifier, a continuous organic fuel phase, a density control agent and a discontinuous phase of oxidizing saline solution containing an inorganic oxidant (s) salt, water and urea as an inhibitor in amounts ranging from 1% to 10% by weight of the explosive agent, the detonating agent is charged in a coupling relationship with the hole, and (b) detonates the explosive agent.

Description

METHOD FOR PREVENTING SULFIDE POWDER EXPLOSIONS AFTER DETONATIONS.

The present invention relates to methods for preventing explosions of sulfur dust subsequent to a detonation in blasting operations of minerals containing a relatively high percentage of sulfides or pyrites. In a more particular meaning, this invention relates to a method that involves (a) charging an explosion hole that has been drilled into a mineral body containing sulfides and pyrite with an emulsified detonating agent containing urea as a chemical inhibitor in the phase discontinuous saline solution and (b) detonate the explosive agent. The chemical inhibitor used in the method of the present invention is urea in amounts ranging from 1% to almost 10% by weight of the explosive agent. The chemical inhibitor acts to suppress the rapid and energetic reaction of the residual nitrates or NOx (which may be present following the detonation of the explosive agent) with the reactive sulfur powder that may be present from the detonation itself.

BACKGROUND OF THE INVENTION Explosions of sulfur dust have occurred in underground mines in various parts of the world, particularly in mines where the mineral body has massive deposits of sulfides in which the sulfur content reaches 50% or more. Although it is estimated that the concentration of sulfides is the main cause of explosive incidents, other chemical, geological or physical factors can also contribute to the propensity of a sulphured mineral body to experience a post-detonation dust explosion. One possible explanation for the dust explosion is that the flames generated by the explosion of the detonating agent ignite the sulfur dust generated by the detonation or the explosion itself (or the dust may be present from previous explosions or other mining activities). The explosion of the resulting dust can cause considerable damage to the mine and present an accident potential for mine personnel. These explosives can also produce large amounts of sulfur dioxide and other toxic gases that can permeate the atmosphere of a mine for hours. In this way, dust explosions result in significant productivity losses in mining operations. Attempts to control dust explosions following detonation have focused on: the type of explosive used, such as ANFO, packaged products, bulk products, etc .; reducing the incendiary characteristics of explosives through variations in the formulation; the design and preparation of detonation, including the use of distribution materials of various kinds; other precautions taken on the surface of the explosion to reduce or cool the explosive flash, such as dew, hang lime bags, etc .; and a general cleaning or moistening all dust in current and on the surface. These practices, although certainly useful, have been insufficient in the most difficult types of minerals where sulfur explosions after detonation occur with almost every detonation. Emulsified detonating agents are well known in the art and generally have properties superior to other detonating agents, such as ANFO or packed detonating agents, to minimize the potential for a sulfur powder explosion after a detonation. The use of a detonating agent emulsified by itself, however, is not sufficient to prevent a sulfur explosion after a detonation in all cases, and it has been importantly discovered in the present invention that the presence of a chemical inhibitor, preferably urea, functions as explained above in order to prevent the rapid and energetic reaction of the explosion after the detonation of the residual nitrates or NO of reactions with sulfurized powder. Then a critical element in the present invention is to add a chemical inhibitor to the emulsified detonating agent. The invention comprises a method to prevent explosions of pol Subsequent Sulfide Volatiles in Detonation Operations Involving Sulfide-Containing Minerals This method comprises (a) charging an explosion hole that has been drilled into a sulfide containing mineral body with an emulsified detonating agent containing an emulsifier., a continuous organic fuel phase, a density control agent and a discontinuous phase of oxidizing saline solution containing salt (s) inorganic oxidants, water and urea as an inhibiting agent in amounts ranging from 1% to almost 10% by weight of the explosive agent and (b) detonating the explosive agent DETAILED DESCRIPTION OF THE INVENTION The chemical inhibitor, urea, is added to the detonating agent in the form of an emulsion either as part of the oxidative saline solution phase or as a dry ingredient or as both Urea is added in amounts ranging from 1 % to almost 10% by weight of the detonating agent and preferably from 2% to almost 6% 25 The failure of prior art attempts to try to control or minimize the occurrence of sulfur powder explosions after detonation of the types of more difficult minerals indicate that the ignition mechanism may have been & > relatively undisturbed by such attempts. There may be an ignition mechanism occurring within the detonation zone that is developing immediately after detonation involving the reaction of hot intermediate gases or detonation products (the most notable is the NOJ and also possibly traces of unreacted nitrate salts with newly formed mineral dust. This powder will be in a highly reactive state at temperatures around the area of the detonation and since it has been formed recently, it will not be passivated by oxidation of the surface (unlike the dust present on the face before detonation) Since there is essentially no oxygen in the area where detonation takes place, heat, intermediate gases and products of the detonation reaction (and possibly residual salts of unreacted nitrate ) are the only possible oxidizing species available for the dust, the most notable the NO gases The resulting oxidation of the particular NOx by ore or the resulting nitrates The particles will be heated even further by the particles and when swept with the current, the dust particles from the street can react even with intermixed oxygen from the mine air, thus substantially increasing the total heat and the incendiary nature of the detonation and contributing to the the ignition of additional sulfur powders mixed with the oxygen in the mine air. If this mechanism is correct, then a NOx scavenger such as urea could substantially suppress the NOx reaction with mineral powder, thereby reducing or eliminating the contribution of this ignition mechanism at the onset of a sulfur powder explosion. The immiscible organic fuel that forms the continuous phase of the composition is present in an amount from about 3% to about 12%, and preferably in an amount from about 3% to less than 7% by weight of composition. The actual amount used may vary depending on the immiscible fuel (s) in question that is used, the presence of other fuels, if any, and the amount of urea used. To ensure that an amount of urea remains unreacted after detonation so as to prevent an explosion of sulfur dust, sufficient urea and organic fuel phase can be added to achieve a negative total oxygen balance with the component of oxidant inorganic salt. Optionally the amount of organic fuel phase can be sufficient by itself to balance the oxygen with the inorganic oxidant salt, and in this way the urea does not need to react to a large extent with the oxidizing salt during the detonation. However, since the method of the present invention will be used mainly in underground operations, the oxygen balance should not be so negative since otherwise it may result in the formation of other toxic gases after detonation, especially monoxide of carbon. Preferably the oxygen balance should be from almost 0 to -8.0% and more preferably -2.0 to 4.0%. In this way the relative amounts of non-miscible fuel and urea can be adjusted as desired. The non-miscible organic fuels can be aliphatic, alicyclic and / or aromatic and can be saturated and / or unsaturated, as long as they are liquid at the formulation temperature. Preferred fuels include tall oil, mineral oils, waxes, paraffin oils, benzene, toluene, xylenes, mixtures of liquid hydrocarbons generally called petroleum distillates such as gasoline, kerosene and diesel fuels, and vegetable oils such as corn oil, oil, cottonseed, peanut oil and soybean oil. The preferred liquid fuels are mineral oil, fuel oil No. 2, paraffin waxes, microcrystalline waxes and other mixtures. Aliphatic and aromatic nitro compounds and chlorinated hydrocarbons can also be used. Mixtures of all of the above can be used. For underground applications, where the present invention will normally be practiced, the preferred organic fuel will be liquid at room temperature to allow the detonating agent to be pumpable for easier handling and storage.

The emulsifiers used in the present invention can be selected from those conventionally employed, and are generally used in amounts of from 0.2% to 5%. Typical emulsifiers are sorbitan fatty esters, glycol esters, substitute oxazolines, alkylamines or their salts, derivatives thereof and their like, and polymeric emulsifiers, such as bisalkanolamine or polyols derived from a bis-carboxylate or olefinic anhydride derivatives or polymers of vinyl addition. Optionally, and in addition to the immiscible organic liquid fuel and urea, other fuels can be used in selected quantities. To prevent the generation of incendiary molten particles during detonation, the additional fuels must be liquid instead of solid.

The solution of inorganic oxidizing salts that form the discontinuous phase of the explosive generally comprises inorganic oxidizing salts, in amounts from 45% to 95% by weight of the total composition, and water and / or water-miscible organic liquids, in amounts from 0% to 30%. Since ammonium nitrate (NA) is potentially more reactive with sulfur powders, other salts may preferably be used to replace some or all of the NA salts in amounts generally up to 50%. The other oxidizing salts are selected from the group consisting of nitrates chlorates and perchlorates of alkali and alkaline earth metals,. Of these, sodium nitrate (NS) and calcium nitrate (NC) are preferred.

Preferably the water is used in amounts ranging from 10% to 30% by weight based on the total composition and more preferably in amounts ranging from 12% to % The use of water within this range helps to cool or lower the detonation temperature compared to ANFO and most packaged products and thus helps prevent explosions of sulfur dust. Organic water-miscible liquids can partially replace water as a solvent in the salts, and these liquids also function as fuels for the composition. Furthermore, some organic compounds also reduce the crystallization temperature of the oxidizing salts in the solution. Solid or liquid miscible fuels in addition to urea may include alcohols such as sugars and methylated alcohols, glycols such as ethylene glycols, other amides such as formamide, amines, amine nitrates, and analogous nitrogen-containing fuels. As is well known in the art, the amount or types of liquid (s) or solid (s) miscible in water used may vary according to the desired physical properties. The emulsion preferably does not contain solids, with the exception of solid urea if it is desired. However, the use of added solid oxidants such as ammonium nitrate tablets and other nitrate or chlorate perchlorate salts as known in the art may be used as long as the product remains effective in preventing dust explosion. sulfide. The density controlling agent may contain chemical gasifying agents that chemically react in the composition to produce gas balloons. In addition to, or in place of, chemical bulking agents, hollow spheres or particles made of glass, plastic or knob can be added to reduce the density. Since inert glass spheres can form molten incendiary particles during detonation, while spheres or microspheres are consumed as fuel, plastic microspheres are the solid density controlling agent of choice. In addition, and as is known in the art, mechanically controlled gas bubbles can be used to reduce the density or add foams. The emulsion of the present invention can be formulated in a conventional manner. Typically, the salt (s) oxidants, urea and other soluble aqueous constituents are first dissolved in the water (or the aqueous solution of water and miscible liquid fuel) at an elevated temperature or from 25 ° C to 90 ° C or plus, depending on the crystallization temperature of the saline solution. The aqueous solution is then added to an emulsion solution and to the liquid immiscible organic fuel, these solutions are preferably at the same elevated temperature, and the resulting mixture is stirred vigorously enough to convert the emulsion of aqueous solution into a phase fuel. continuous liquid hydrocarbon Usually this is achieved instantaneously by stirring rapidly (The compositions can also be prepared by adding the organic liquid to the aqueous solution) Continue stirring until the formulation is uniform The addition of solids such as control agents density (preferably of the plastic type) and optionally solid urea or oxidants can then be mixed into the formulation. When gasification is desired, the gasifying agents are added and mixed homogeneously in the emulsion to produce uniform gasification at the desired rates. Also the solid ingredients, if there are, they can be added optionally together with the gasifying agents and mixed completely with the formulation in the conventional manner. However, to prevent the loss or coalescence of the gas bubbles, the subsequent handling must be done quickly after the addition of the agent gasifier, depending on the gasifying ratio It has been found to be advantageous to pre-dissolve the emulsifier in the organic liquid fuel before adding the organic fuel in the aqueous solution This method allows the emulsion to form quickly and with minimal agitation However, If desired, the emulsifier can be watering as a third component The reference to the following table illustrates the invention Table I provides formulations and detonation results for stabilized emulsions for use in reactive metals subject to a post-detonation dust explosion. Examples 2 and 4 are preferred as that they contain salts of secondary oxidants and the preferred density reduction means, for example, respectively, plastic microspheres and chemical gasifiers. As described below, the effectiveness of the formulation set forth in Example 2 of Table I was demonstrated with success in mines that were expending explosions of dust after a detonation Field test 1 The field tests were conducted in a copper mine in an area of ore containing a high concentration of sulfides. The sulfur content was in excess of 40%. Prior to testing the method of the present invention, the detonation was I had carried out this mine using ANFO with some packaged products. Mine personnel took precautions to try to prevent explosions of sulfur dust. This included plugging the hole with an inert cartridge, washing the detonation area and using a rain of water to suppress the dust created by the detonation Despite these precautions, the explosions of sulfur powder after detonations occurred regularly in this area of the mine. A detonation pattern was loaded with the detonating agent of the stabilizing emulsion of Example 2 in Table I All the other precautions that were normally taken with ANFO, were also taken at this time d The detonation did not produce a dust explosion, and the results of the fractures were equivalent to, or better than, those obtained with ANFO A second pattern was loaded in the same section, but precautions were not taken Again the detonation did not produce a explosion of sulfur dust * after detonation and the detonation results were good. As a comparison a third pattern was loaded in the same section with ANFO, together with the use of all precautions. There was a violent explosion of sulfur powder later to the detonation, and more than 61 meters (200 feet) of ventilation pipes were damaged. A 5th strike consisting of another load of the same section with the stabilized explosive agent of Example 2 No additional precautions were taken. The detonation did not produce an explosion. of sulfur powder after detonation and the detonation results were excellent Terrain test 2 Additional soil tests were conducted in a copper and zmc mine where the content of sulfide metals was 40% or more In this mine, the previous use of standard aqueous gel and ANFO products caused dust explosions of sulfur postnores to detonation with each detonation This explosions occurred despite the many precautions which included detonating one charge at a time (previous experience in the mine indicated that multiple detonations increased the possibility of explosions after detonation), washing the walls, and applying a shower of water to the face In fact, the mine had discontinued the detonations in this section due to the constant occurrence of explosions of sulfur dust 20 A complete round was loaded with pumpable stabilized explosive emulsifying agent of Example 2 in Table I For this charge, all precautions that were normally used were taken, as described above. The detonation did not produce an explosion of sulfur powder post-detonation to the detonation evidenced by a lack of gases normally detected after these incidents and by a visual inspection of the detonation area The detonation results were very good Another test was performed in the same area, but this time none of the usual precautions were taken Two rounds were also loaded in the same section and simultaneously detonated Despite the absence of the precautions, with the formulation of Example 2 there was no explosion of sulfur powder after detonation and the results were very good. A third test was conducted in the same area, but 5 separate loading points were included for the stabilized emulsion of Example 2 or other precautions were taken. Due to the multiple loading, the mine personnel were sure that an explosion of sulfur dust would occur The detonation produced good results and there was no explosion of sulfur dust 35 More tests were conducted in the second mine in both sections and in other areas with high sulfur content with explosion histories of sulfur powder The emulsion of Example 2 did not produce even a single explosion of sulfur powder after detonation Following this test, the same lines were treated in this detonation mine with packaged prior art emulsions that were not stabilized and by the 40 so much did not contain urea, in these cases there was the explosion of sulfur powder While this invention has been described with reference to certain illustrative examples, for those skilled in the art will be obvious vain modifications and any modification will be contemplated within the scope of this invention as set forth in the claims 15 20 25 30 35 40 Table I Typical stabilized emulsions for use in reactive minerals susceptible to sulfur powder explosions after detonation. % fifteen twenty w ^ f 30 40

Claims (8)

1. CLAIMS 1 - . 1 - A method to prevent explosions of sulfur dust after a detonation operation involving metals containing sulphides CHARACTERIZED because it comprises 5 (a) charging an explosion hole that has been drilled into a mineral body containing sulphides with an agent emulsifying detonator containing an emulsifier, a continuous organic phase of fuel, a density control agent and a discontinuous phase of oxidant saline solution containing an inorganic oxidant salt, water containing urea in amounts ranging from 1% to 10% by weight of the explosive agent, the detonating agent is charged in a coupling relationship with the hole, and (b) detonated the explosive agent 2 - . 2 - A method according to claim 1 CHARACTERIZED because the density controller agent 15 is selected from the group consisting of plastic microspheres and gas bubbles 3 - . 3 - A method according to claim 1 CHARACTERIZED because the inorganic oxidizing salt is selected from the group consisting of nitrates and ammonium perchlorates 20 and alkali metals and nitrates and perchlorates of alkali metal teneos 4 - . 4 - A method according to claim 3 CHARACTERIZED in that the inorganic oxidizing salt is a combination consisting of a higher proportion of ammonium nitrate and a minor proportion of another nitrate or perchlorate 25 - A method according to claim 4 CHARACTERIZED because the inorganic oxidizing salt is ammonium nitrate 6 -. 6 - A method according to claim 1 characterized in that the organic fuel phase is an organic combustible liquid in an amount sufficient to balance the oxygen of the inorganic oxidant salt 7 -. 7 - A method for preventing explosions of sulfur powder in detonation operations involving metals containing sulfides according to claim 1 CHARACTERIZED because it comprises (a) charging an explosion hole that has been drilled in a mineral body containing sulfides with an emulsifying detonating agent containing an emulsifier, a continuous organic phase of fuel in amounts of 3% to 12% by weight of the detonating agent, a density control agent and a discontinuous phase 40 d oxidizing saline solution containing an inorganic oxidizing salt in amounts of 45% to 95%, water in amounts of 10% to 30%, and because it contains urea in amounts ranging from 1% to 10% by weight of the explosive agent, the detonating agent is charged in a coupling relationship with the hole; and (b) detonate the explosive agent. 8. - A method according to claim 7 CHARACTERIZED because urea is present in amounts of 2% to 6%. 10 fifteen twenty 25 ? 30 35 40