Process design and optimization on self-sustaining pyrolysis and carbonization of ultra-low calorific value coal gangue

In the process of coal mining, washing and utilization, a huge amount of coal gangue (CG) is produced, which has become the largest solid waste in China. Large accumulation of CG is not only occupying the land area, but also leading to severe environment pollution. Therefore, the disposal of CG is extremely urgent in China. In this paper, a novelty process of CG pyrolysis is proposed, which can achieve self-sustaining treatment of CG. Based on the analysis results of pyrolysis experiments, the process simulation is established by Aspen plus software. By comparing the effects of CG type and pyrolysis temperature on the system, the stability and flexibility of the system is analyzed. The experiments results show that, with the increase of pyrolysis temperature, the oil and gases yields of CG pyrolysis increases. The simulation results show that under the same process conditions, the economy of the system strongly depends on the quality of CG, and the method proposed in this paper is more economical to treat ultra-low calorific value CG. The pyrolysis temperature also significantly affects the energy self-balance of the system, and the recommended pyrolysis temperature is about 600 ℃ for industry process.