| Coal and gas protrusion is a kind of coal mine power disaster that is very easy to encounter in the process of coal mining,which is manifested in a very short period of time accompanied by gas gas throwing out a large amount of coal rock,which seriously threatens the safety production of the mine and the life safety of underground workers,which is an urgent problem to be solved.In essence,the process of coal and gas protrusion is the process of energy accumulation and dissipation,and the energy within the gas acts on the crushing and throwing of coal rock mass.In order to study how much energy is required for coal rock mass to be crushed into small particle sizes after impact,this paper takes six kinds of raw coal of different hardness as the research object,combines experimental and theoretical analysis,based on the theory of pulverization power consumption,and studies the range and characteristics of the k-value of the crushing parameter by relying on the crushing power experiments of raw coal of different hardnesses,and discusses the application value of k-value.The following conclusions are obtained:1.In the state of the impact process of the falling hammer device,it is found that when the raw coal falling hammer impact crushing experiment is carried out,the large and small coal particles in the falling hammer barrel are gradually stratified under the multiple impacts of the heavy hammer,and the corresponding consolidation state is presented relative to different impact energies,and the higher the hardness of the coal,the greater the crushing power acting on the unit mass coal,the more conducive to the crushing of small-grain coal.The layer crushing theory and the limit surface theory can explain this phenomenon very well.It shows that when the impact energy reaches a certain level,there is a crushing limit,the particle size of the tiny coal particles reaches a certain fineness,the particles appear micro-plastic deformation,and the forging and welding phenomenon occurs.This part of the coal particles are repolymerized by forging and welding,and the particles are enlarged.2.When the tiny coal particles(particle size <0.1mm)were observed,the surface area distance average diameter and volume distance average diameter of this part of the coal particles were tested by laser particle size analyzer,and the range of surface area distance average diameter was 19.1～36.3 μm,and the range of volume distance average diameter was 49.4～88.8 μm.It can be seen that there is still a certain gap between the coal particles after impact crushing and the perfect spherical model.3.Through the analysis of the firmness coefficient f-value,the crushing power of the coal body and the degree of crushing of the coal body,the relationship between the fvalue of the solidity coefficient and the converted diameter,the crushing work and the new surface area is discussed.The results show that the f-value and the converted diameter show a good linear function relationship,the fitting relationship is d＿m=1.4615f-0.1691,and the correlation coefficient is 0.9899;the crushing work has a good exponential function relationship with the new surface area,but the rate of change of the exponential function is different;the specific surface area is not affected by the solidity coefficient,only related to its own internal structure and the size of the external impact energy.4.The k-value of the pulverization parameter of the coal body is highly linear correlated with the crushing ratio w and has nothing to do with the size of the crushing work,and the k-value and the crushing ratio w fitting relationship formula: k＿n=13.666w-682.38,and the linear correlation is 99.69%;The k value has a good linear correlation with the new surface area after the impact crushing of the coal rock mass,and also has a good linear correlation with the new surface area of the tiny coal particles.It is explained that the k value can reflect the degree of crushing of the coal body,and the k value is an indicator of the strength of the coal body to resist external crushing force.Factors affecting the k value are the hardness(solidity coefficient)of the coal rock mass and the crushing power applied to the coal body.The degree of crushing of the coal can be inferred when the k-value is known.The research results of this paper can provide certain theoretical and practical support for the research of coal body crushing power in coal rock power disaster coal and gas protrusion,and have certain theoretical and practical value.Figure 35 Table 24 Reference 73... |
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