Technical Progress and the Prospect of Low-Rank Coal Pyrolysis in China

China possesses an amazing variety of low-rank coal (LRC) resources. The developed strategies for the large-scale use of coal resources in China suggest that achieving the grading effective conversion and utilization of LRC by mid-low-temperature coal-pyrolysis technologies can maximize LRC resources. On the basis of investigations on and the analysis of coal-pyrolysis technologies, a comprehensive overview of the LRC pyrolysis technologies in recent years is described in this review. The technologies include square-retort pyrolysis technology, upgraded square-retort pyrolysis technology, solid-heat-carrier pyrolysis technology, belt-type-furnace pyrolysis technology, and rotary-kiln pyrolysis technology. Focusing on the technical characteristics with analysis and comparison of different LRC pyrolysis technologies, we summarize the main problems in the development of pyrolysis processes, namely, dust separation of coal tar, wastewater treatment, and incomplete pyrolysis reaction mechanisms. Moreover, suitable methods for the rational and efficient utilization of LRC resources are discussed to achieve the sustainable development of pyrolysis technologies based on optimizing pyrolysis reactors and developing deep-processing multigeneration technologies.