Prevention and control of coal spontaneous combustion are key to coal mining and storage. Existing technologies for the detection of coal spontaneous combustion have limitations, but coal spontaneous combustion creates some serious disasters in areas of the world where coal mining and/or storage exists. New technologies to detect coal spontaneous combustion are urgently needed to reduce the loss of life and resources. The article reviews the main techniques employed to detect coal spontaneous combustion and their advantages and disadvantages; it also reviews the good application prospect of acoustic temperature measurement technology on coal spontaneous combustion and introduces the basic principle of acoustic coal temperature measurement. The evolution of combustion sound and the propagation and attenuation of acoustic waves in quasi-porous media are discussed to form the basis for the development of acoustic thermometry technologies that can be used to accurately identify acoustic signals and temperature fields in loose coal. The concept of "single-source" coal temperature measurement to "dual-source" coal temperature measurement achieved by using combustion sound and an additional sound source device in the automatic combustion of loose coal in the mined area is discussed. The deep learning methods and correlation analyses are available to map the relationships between combustion sound, coal temperature, and sound velocity, and acquire coal temperature from dual source composite acoustic signals. The study lays the foundation for the development of acoustic thermometry technologies that have applications in different stages of combustion and applied to the early warning, prevention, and control of spontaneous combustion in coal, and it contributes to improving the environmental safety and efficiency of coal mining and storage.
The accurate prediction of coal spontaneous combustion
(CSC) in
the goaf areas of coal mines is a vital aspect of the migration from
passive to active fire prevention and control. However, CSC is highly
complicated and existing technologies cannot accurately monitor coal
temperatures over wide expanses. Thus, it may be beneficial to assess
CSC based on various index gases produced by the reactions of coal.
In the present study, the CSC process was simulated by temperature-programmed
experiments, and the relationships between index gas concentrations
with the coal temperature were determined using logistic fitting functions.
CSC was divided into seven stages, and a coal seam spontaneous ignition
early warning system involving six criteria was established. Field
trials demonstrated that this system is a viable approach to predicting
coal seam fires and meets the requirements for the active prevention
and control of coal combustion. This work establishes an early warning
system based on specific theoretical guidelines that permits the identification
of CSC and the implementation of active fire prevention and extinguishing
measures.
Fire extinguishing with the superior performance of fly ash composite colloid material is a cost-effective colloid fire prevention technology. In this paper, a new powder additive (suspending agent (XK-XJ) and gelling agent) was developed for the existing fire extinguishing technology of fly ash compound colloid. Tests show that the best additions to the fly ash slurry were 0.3% and 0.1∼0.3%, respectively. The grouting technical scheme of adding a suspending agent on the ground and gelling agent downhole was proposed to solve the problems of solid material settlement and blockage in the long-distance pipeline transportation process. Finally, the optimized fly ash colloid fire prevention and extinguishing technology was successfully applied to the fire control engineering examples of close-range coal seam groups, and the rationality of the developed powder and its proportion was tested, and the feasibility in coal fire control was tested.
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