Catalytic conversion of gaseous tar using coal char catalyst in the two-stage downer reactor

The effect of catalyst height (0-50 mm) and catalyst temperature (600-900 degrees C) on the catalytic cracking of gaseous tar is investigated using a two-stage down reactor. Results show that the utilization of catalyst promotes the removal of coal tar. The yield of coal tar at the pyrolysis temperature of 900 degrees C is 7.14% and tar is composed of aromatics and high-carbon-number aliphatics. The coal char prepared by fast coke-making method at 900 degrees C is directly used as a catalyst in the catalytic cracking of coal tar. When the catalyst temperature and the catalyst height are 900 degrees C and 50 mm, the tar produced by coal pyrolysis is connected with high-temperature coal char for a short time, reducing the tar yield from 7.14% to 4.26%. Among them, aliphatic hydrocarbons with carbon number of C10 and C11 and aromatics are the main components of coal tar. Similarly, compared with the pyrolysis, the content of CH4 and H-2 obtained with the addition of the catalyst increase from 0.56 to 0.97 to 1.64%g/g coal and 1.02%g/g coal, respectively. Moreover, GC/MS results show that the increment of catalyst height and catalyst temperature increases aromatics content and facilitates the conversion of high-carbon-number component to low-carbon-number ones. (C) 2021 Elsevier Ltd. All rights reserved.