Introduction
At Ukrainian mines between 6 and 36 endogenous fires are registered annually. They take the second place after exogenous fires in terms of the damage they cause. For example, in 1999 it made 8 mln hrn, which made 21.4% of the damage from all mine accidents. The most efficient mine fields at Zasyadko, Kapustina and other mines have been driven out of operation by these fires.
In the structure of the world reserves coal dominates - 60%, oil and gas take 27%, other mineral - 13%. However in production the main part is taken by oil and gas - 67%, coal makes only 30%. One of the most important reasons is danger of coal extraction process.
Topicality
Millions of scientists have tried to make miners' labour safer. However this problem has not yet been solved. Thus, the problem of labour safety and protection at mines is one of the most urgent problems.
Endogenous fires occur because of coal self-heating in the places which are difficult to reach, such as worked and supported space, pillars, coal pumps, behind the insulating bridges, seam-satellite. Extinguishing of fire sites in such conditions is made more difficult. 36% of fires are put out by the active method, 59% are isolated, in 5% of cases combined methods are used. prognostication and prevention of coal self-heating is the most perspective and economically expedient way of fighting endogenous fires.
Development of ways to predict self-heating and self-combustion conditions is especially topical in such conditions
The research aim
Development of methods to prognosticate endogenous fire danger of mine workings. Analysis of dependence of the recorded fires number at Donbass mines on coal and anthracite metamorphism and composition of native water released from the caved coal.
Main part
Main part consists in development of modern methods to prognosticate and predict endogenous fires.
Many scientists have been working on the problem of discovering the nature of coal self-combustion. However, initial stage of self-combustion process is still unexplored.
There are several theories of coal self-combustion (sulfur, coal-oxygen, etc.), but there is no common theory.
The proven fact is that the coal seam is not evenly self-combustible. We can speak about zonal character of self-combustion.
It is also interesting that some coal beds are equally inclined to coal and gas outburst and self-combustion. According to coal-oxygen theory such seam after outburst self-combustion incubation period is shortened. However in such seams also there can be no endogenous fires, i.e. there is lack of some physical and chemical activity.
The author of a new theory of coal self-combustion tendency is prof. Nikolin V.I. The theory is in experimentally determined capacity of the caved rock to give away native water (solutions) from the pores more that 10-7m during unloading. It is shown in animation.
The genetic recovery deformations take place (GRD), which are accompanied by obligatory release of different solutions and compounds from the extracted coal, they moisten the products of extraction. Some of them can be chemically active relative to coal compounds, and can be accompanied by heat generation, which conditions locality of endogenous fires. But the chemical composition of the native water changes absolutely illogically.
There exists an opinion that extraction of low-metamorphized coal is especially fire-dangerous. But endogenous fires do not occur during development of highly-metamorphized anthracites, characterized by lg<3.0. This is explained by the fact that high level of anthracite metamorphism has led to absolutely complete absence of outburst danger, tendency to GRD.
This animation shows the pattern of change of Pi tendency to unexpected gas and coal outbursts (1), sandstone and gas outburst (2), endogenous fire danger (3) depending on coal metamorphism level: points À - lgp = 3,3; Á - Ì=27,7; Â - Vdaf= 18 %; Ã - Ì=28,9; lgp = 3,0.
It appears from this that the further increase of coal metamorphism is accompanied now by decrease of the outburst probability. The natural gas-content decreases, and highly-metamorphized anthracites become gasless and highly porous.
This proves that the most intensive physical and chemical transformations of organic substances accompanied by methane and its homologues take place in seams characterized by Vdaf=19-20%
While predicting coal self-combustion it is necessary to use not the coal ranks but the more exact definition of the coal metamorphism on the basis of three criteria: Vdaf,%; lg p and M (complex metamorphism value).
On the basis of the analysis of endogenous fires at Donbass mines foe the last 25 years it is possible to work out the dependence of endogenous fires number on coal metamorphism level, valued as lg p for anthracites and Vdaf for coals.
Dependence is built on the basis of average data. It is approximate that is why determined by the dotted line.
As is seen from the graph in point Á - Vdaf ~ 40.7% - corresponds to the maximum release of volatile substances at which coal combustion took place. With the increase of metamorphism level the number of endogenous fires increases sharply being maximum in point B - Vdaf ~ 34-35%. With the further rise of metamorphism level gradual drop in endogenous fires is observed.
Point À - lg p = 6.6 ~ Vdaf ~ 6.6% corresponds to the minimum release of volatile substances, at which endogenous fires were registered.
Conclusions
The work presents theoretic generalization of urgent scientific and technical problem - crease of endogenous fires safety on the basis prediction of coal self-combustion at definite composition of native waters.
Carried out research allowed to extend the idea of peculiarities of coal self-heating occurrence and development and determine a number of factors increasing the efficiency of endogenous fires prediction and prevention.
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