Search

Mine fire is a serious threat to workers’ health and safety production of coal mines. Foam is used as an efficient extinguishment method in underground coal mines. A new design of foam generator was proposed to solve the drawbacks caused by the complicated operation of conventional foam technology. Experimental results show that the intake air pressure of the new foam generator increases with the foam liquid pressure linearly. The foam production quantity and foam expansion ratio reach maximums at the foam liquid flow of 3.5-4.5 m3/h. The intake air pressure increases sharply with the outlet pressure especially at a larger foam liquid flow. It is essential to keep the foam generator outlet pressure less than a critical value to get an optimal foam production quantity. The new foam generator has the advantages of simple structure, convenient operation and compact size that is very suitable for fire extinguishment in underground coal mines. The foam technology using the new device makes a good foaming effect in the field and ensures the safety operation of dismantling hydraulic supports from the working face, creating significant economic benefits for underground coal mines. [ABSTRACT FROM AUTHOR]

To investigate the characteristics of adiabatic oxidation phase and build the prediction model of coal spontaneous combustion critical point, the adiabatic oxidation experiment data of eight coal samples are given in this paper, based on the adiabatic oxidation experiment, element analysis experiment and industrial analysis experiment. The phase heating rates of adiabatic oxidation of these samples are also calculated. Then using the thermodynamic parameter calculation method, Tr0.05 and TΔmax are defined and obtained. Furthermore, based on the Levenberg-Marquardt method, the relationship between the coal element content, volatility, the phase heating rate of adiabatic oxidation and Tr0.05 are established. The results show that the content of N or S correlates positively with Tr0.05 Osand that O, C, or H content correlates negatively with Tr0.05. However, the link between these elements and stage-heating rate is the opposite. The law also suggests that stage-heating rate will be much faster and coal spontaneous combustion will be easier when Tr0.05 becomes much lower. The more volatile coal is, the lower Tr0.05, and the more likely it is to spontaneously combust. [ABSTRACT FROM AUTHOR]

In order to theoretically understand the law of temperature rise due to spontaneous combustion in caving zone of roof coal in coal mine roadway, and identify the location of hazardous region and studied the fire prevention effects by nitrogen injection, the software FLUENT was used to solve the stable state of air leakage speed and oxygen concentration ,dynamic temperature distribution and cooling effects brought by nitrogen injection in the high caving zone based on the assumption that coal oxidation rate accords with Arrhenius law. The computation results indicate that the temperature rise reflects a slow-accelerating process and the portion close to roadway has lowest temperature while the deep portion comes next, the top temperature region lies in the middle part of caving zone and deviates to inlet. The rate of temperature rise in high temperature region accelerates both by the increasing air velocity in roadway and increasing porosity when practical size is kept unchanged. The nitrogen injection in high temperature region can lead to obvious cooling effects for the reason that the temperature close to injection hole decreases dramaticlly after short time and cooling effects extend towards part of the middle and outlet gradually. [ABSTRACT FROM AUTHOR]