A research group led by Choe Yong Chol, a researcher at the Faculty of Mining Engineering, has been employing his new method of reducing the amount of harmful explosion gas by using vermiculite and acidic deposits of mine water.
Introducing this technology, you can increase the power of explosion much higher than before thanks to the increase in the work ability resulted from the evaporation of combined water in vermiculite as well as the increase in brisance resulted from the increase in explosive density. At the same time, you can reduce the emission of harmful explosion gas such as CO and NOx by adsorption of expanded vermiculite, absorption of water separated from vermiculite and oxidation of metallic oxides in vermiculite at high temperature of explosion.
This method has two stages; manufacturing stage where vermiculite that passed through crushing, separating and distributing processes and acidic deposits of mine water are mixed, and application stage where they are admixed with explosives.
Explosive additives are made with vermiculite of 0.1mm~1.5mm in granulation size and acidic deposits of mine water less than 0.05mm in granulation size in the proportion 3:1. This mixture and Expanded Ammonium Nitrate Explosives are mixed evenly in a ratio of one to five and put into blasting cartridges before use.
Most of the acidic deposits of mine water consist of ferric hydroxide(Fe(OH)3) and basic ferric sulphate(Fe(OH)SO4). In vermiculite, some metallic oxides such as ferric oxide make up about 5.5%, which is less than those contained in acidic deposits of mine water. Trihydric ferric salt and ferric oxides serve as oxidizers that oxidize CO and NO in explosion gas to CO2 and NO2 respectively.
Vermiculite contains about 15% of interformational water which is not changed between micaceous layers at low temperatures but converted into water vapor at over hundreds of degrees. This interformational water removes harmful gases by absorbing soluble gases like NO2, N2O3, N2O4, etc. produced from explosive reactions and from oxidation by trihydric ferric constituents in the additives.
Vermiculite has a strong cation exchange ability. Its cation exchange capacity and base absorption capacity increases by 1.5 times at high temperatures. Thus, at high explosion temperatures vermiculites are expanded and the absorption ability for harmful explosion gas is further increased.
When explosives are mixed with vermiculites and acidic deposits of mine water that are heavier than constituents of explosives, the charge density of explosives increases. Consequently, the detonation velocity and pressure increase and the dynamic explosion power of explosives gets higher.
Vermiculite has a maximum of 18% of interformational and combined waters, which are changed into water vapour at the moment of explosion and expanded thousands of times in volume. It results in a considerable increase in the volume of explosion gas and in the explosion pressure of explosives, which leads to the increase in the static power and blast effects.
If this additive(vermiculit and acidic deposit of mine water) makes up 20% in explosives, removal rate for CO and NOx gases can be more than 93% and 85% respectively. The explosion power of explosives remains similar to or gets higher than before.
With the introduction of this method to all kinds of blasting operations such as driving, you can save a considerable amount of explosives and make a contribution to protecting the environment and improving working conditions by reducing the emission of harmful explosion gas.
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