EXACT TITLE OF PAPER: The Study on kinetics of LRC mild pyrolysis

摘要

Low rank coals (LRCs) are characterized by their high moisture content and high reactivity, which greatly restricted their utilizationsunless they were upgraded. The “Coal Refining” technology developing by National Institute of Clean-and-low-carbon Energy ofChina (NICE) is one of the technologies that upgrade LRCs to value-added products with improved transport safety and economics. Inthe technology, LRC was pyrolyzed at mild conditions to decrease its volatile and then passivated to stable high-BTU upgraded coal.Pyro-oil was another high value product produced during the mild pyrolysis of LRC. Though the kinetics of coal pyrolysis have beeninvestigated by many people, most of them are conducted in high temperature regarding pyrolysis as the first step of combustion andgasification. The research on coal pyrolysis at mild conditions is still limited in literatures. In order to understand the mild pyrolysis of LRC, the kinetics of mild pyrolysis is studied in this paper.Experimental studies on mild pyrolysis of typical Chinese lignite were done in a TGA-FTIR system at atmospheric pressure andtemperatures ranging from 480～593°C. The primary gas species (CO, CO_2, CH_4, and H_2O) from coal mild pyrolysis are analyzedquantitatively. Not like high temperature pyrolysis, a portion of the volatiles in coal will never cracked and released at mild conditions because the bonds of these volatiles are strong enough at this temperature level. The mild pyrolysis reaction rate depends not only on the temperature, but also the “effective volatile” in coal, which means the theoretical cracked volatile in coal after a long time at certain temperature. The relationship between the effective volatile and temperature was studied. The pyro-oil yield increased with temperature, but the increasing rate became slowly at high temperature, probably because more pyro-oil was secondly-cracked to gas species at higher temperature. The gas compositions were different at different temperatures so that different species should have distinct kinetics. Therefore separate kinetics of CH_4, CO, CO_2, H_2O and pyro-oil were built from the experimental data.