The production and evolution of fractures during coal creep will directly affect the occurrence, extraction and flow law of gas in a coal seam. The coal fracture evolution under creep conditions was studied by qualitative analysis and quantitative characterization. At a room temperature of 24 °C, triaxial compression creep tests of coal samples from the Zhaogu No. 2 coal mine in Jiaozuo were carried out under different loading conditions (0 MPa, 6 MPa, 9 MPa and 12 MPa), and low field nuclear magnetic resonance technique tests and industrial CT scanning experiments were performed. The obtained CT images were analyzed with the MATLAB software for equalization and binary image processing. The development and distribution of fractures in coal samples under different loading conditions were studied. The results show that the internal fractures are unevenly distributed and controlled by the main fracture, and the expansion direction of fractures is parallel to the direction of the maximum effective compressive stress. The number of fractures shows an increasing trend with the increase of axial stress, and the pace of growth of new fractures accelerates. The primary fractures in the coal body expand and generate new fractures, which improves the connectivity of the fractures in the coal body. The research results can provide a basis for studying the gas flow rule around the borehole and determining the influence range of the borehole.

The exhaust flue gas cooler in a 300MW oxy-coal fired boiler is taken as an object of study. The simulation model of the cooler was established by the method of lumped parameter. The change rule of the exhaust flue gas cooler parameters and the flue gas thermal physical property parameters were analyzed by the disturbance of the coal feeder speed. It is found that, the simulation model of exhaust flue gas cooler was established basing on the conservation laws of mass and energy. The simulation experiment results show that the change rules of main operational parameters and the flue gas thermal physical property parameters in the exhaust flue gas cooler can be reasonably presented by the model with the speed disturbance of coal feeder, which can be the reference for the design and the operation control of the flue gas coolers.

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The flue gas compression system in a 300MW oxy-coal fired boiler unit is taken as an object of study. By the leakage test of quad-section rotary gas-gas preheater on B-MCR condition, the influence from the leakage on the operation parameters of the flue gas compression system were analyzed. The results present that the leakage of the quad-section rotary gas-gas preheater leads to the temperature drop of the exhaust flue gas, which is beneficial to the elimination of flue gas moisture. But the increase of compressed flue gas flow leads to the increase power of flue gas compressor. In addition, with the increase of air leakage rate of quad-section rotary gas-gas preheater, the rise of flue gas compressor outlet pressure has an influence on the operation performance of deep dehydration equipment, which is unbeneficial to further purification and recovery of the compressed gas.