Experimental study on acoustic emission characteristics of high-temperature thermal damage in an oxygen-rich environment of long flame coal

In the process of underground coal gasification, the development and evolution of cracks are vital for efficient coal gasification. In this paper, long flame coal is taken as a test object and heated to different temperatures (100-500 degrees C) in an oxygen-rich environment. The failure process of coal samples was analysed and monitored based on acoustic emission (AE) technique. The results show that the heating process of coal samples can be divided into two stages-room temperature to 300 degrees C and 300-500 degrees C-where the AE counts, energy and mass loss are closely related. Inflection points of the b-value occur at the temperatures of 250 and 400 degrees C corresponding to the change of AE counts. The cracks on the surface of coal samples gradually vary in width with the increase in heating temperature in the range of 100-400 degrees C, and the crack width becomes narrow at 500 degrees C due to the sealing of pores by tar condensation.

Automated summary

This paper investigates the development and evolution of cracks in the process of underground coal gasification using acoustic emission (AE) technique. The experiments were conducted on long flame coal samples heated to different temperatures in an oxygen-rich environment. The results show that the heating process can be divided into two stages based on AE counts, energy, and mass loss. The width of cracks on the surface of the coal samples gradually varies with the increase in heating temperature, becoming narrower at 500 degrees C due to tar condensation sealing the pores.