Supercritical water gasification of coal is a clean and efficient method for coal utilization which can convert coal into H₂ and CO₂. In order to further reduce costs, a novel two-step cascade utilization method was proposed in this study: conducting traditional pyrolysis first and then gasifying the pyrolysis char in supercritical water. The influences of different pyrolysis operating parameters on gaseous products and char gasification in supercritical water were investigated. Quartz tube reactors were used to ensure the complete collection of gaseous products in pyrolysis process. The experimental results showed that both carbon and hydrogen conversion efficiency increased with temperature, and the increasing trend became not obvious after reaction for 5 min. The thermo-gravimetric curves showed that volatilization removal process was completed at the pyrolysis time of 5 min and higher pyrolysis temperatures were beneficial to the subsequent gasification process. The result also showed that residual weight was 15%–20% of the initial weight. Hydroxyl radicals kept stable during pyrolysis process with the absorption peak intensity increasing first and then decreasing, and mineral substance disintegrated gradually as time increased. As pyrolysis temperature increased, the peak of CC double bonds decreased, turning into stable functional groups and carbonyl group increased. Dispersive pores occurred at the surface of coal as residence time increased with particle size decreasing, specific surface area and reactivity increasing. The results might be used for the design of a cascade utilization system based on coal gasification in supercritical water.

煤的超临界水气化是一种清洁有效的煤炭利用方法，可以将煤转化为H ₂和CO _2。。为了进一步降低成本，本研究提出了一种新颖的两步级联利用方法：首先进行传统的热解，然后在超临界水中气化热解炭。研究了不同的热解操作参数对超临界水中气态产物和焦炭气化的影响。石英管反应器用于确保在热解过程中完全收集气态产物。实验结果表明，碳和氢的转化效率均随温度的升高而增加，反应5 min后其增长趋势不明显。热重曲线表明，在5min的热解时间完成了挥发去除过程，较高的热解温度有利于后续的气化过程。结果还表明，剩余重量为初始重量的15％至20％。羟基自由基在热解过程中保持稳定，吸收峰强度先增大后减小，随着时间的增加矿物质逐渐分解。随着热解温度的升高，C的峰值C双键减少，变成稳定的官能团，羰基增加。随着停留时间的增加，随着粒径的减小，比表面积和反应性的增加，在煤的表面出现了分散的孔。研究结果可用于基于超临界水中煤气化的级联利用系统的设计。