Preheating pyrolysis-char combustion characteristics and kinetic analysis of ultra-low calorific value coal gangue: Thermogravimetric study

A massive amount of coal gangue is produced during the mining and washing processes of coal, and it has become China's largest solid waste. Therefore, the disposal of coal gangue is extremely urgent. In this paper, a norvel coal gangue disposal technology is proposed, which is mainly divided into two stages: high temperature preheating pyrolysis and char combustion. A 300,000 tons/year demostration project of self-sustainable direct combustion decarbonization without auxiliary fuel is eatablished. The weight loss characteristics and kinetic analysis of ultra-low calorific value coal gangue in this process were studied by thermogravimetric analysis, compared with the normal calorific value coal gangue. The results show that the equipment has advantages and stability for the disposal of ultra-low calorific value coal gangue, and the removal rate of combustible components can reach 88.47 % on average. Based on analysis of TG data, it is determined that the best model describing stage 1, stage 2 and stage 3 of coal gangue pyrolysis process is D3, F2 and F2 model respectively, and the best model describing char combustion process is D2 model. Comparison experiments were carried out for ultra-low caloric value coal gangue under different heating rates and combustion temperatures. It is concluded that the residence time and combustion temperature in actual engineering have influence on the process, and it is suggested that the combustion temperature of char should be 800 ∼ 900 ℃. The research presented in this paper can provide innovative solutions for the disposal of coal gangue, and provide corresponding theoretical guidance.