Two-stage gasification process simulation and optimization of pulverized coal for hydrogen-rich production using Aspen plus

Abstract

This study proposed a two-stage gasification (TSG) process of pulverized coal to allow for hydrogen-rich (HR) production. The balance flow of this process is constructed using Aspen Plus software. Gasification pressure (GP), steam-coal ratio (SCR), and oxygen-coal ratio (OCR) influences on the process are studied, and the operating conditions are optimized to achieve the maximum hydrogen production. The results show that the GP mainly affects the pyrolysis of pulverized coal in the low-temperature section. Reducing the GP is conducive to hydrogen production. However, it requires heat supplement to raise temperature and maintain the balance of the system. An increase in the SCR is better for hydrogen production, leading to a decrease in the gasification temperature. When the SCR is higher than 0.3, the steam utilization rate decreases obviously. With an increase in the OCR, the gasification temperature continues to increase, and hydrogen production first increases and then decreases, reaching its peak at approximately 0.5. The optimal parameter combination is as follows: the SCR is 0.3; the OCR is 0.53; water is used as the medium for temperature regulation uses, and the water supply is 0.12 kg/kg coal; oxygen is used to raise the temperature of the low-temperature section, and the oxygen supply is 0.18 kg/kg coal. The hydrogen production rate of the optimal working condition is 77.78 g/kg coal, which is 48.38% higher than that of single-stage gasification.