Enhanced near-zero-CO 2 -emission chemicals-oriented oil production from coal with inherent CO 2 recycling: Part I—PRB coal fast pyrolysis coupled with CO 2 /CH 4 reforming

In this study, the Powder River Basin (PRB) coal fast pyrolysis was conducted at 700 °C in the atmosphere of syngas produced by CH4–CO2 reforming in two different patterns, including the double reactors pattern (the first reactor is for syngas production and the second is for coal pyrolysis) and double layers pattern (catalyst was at upper layer and coal was at lower layer). Besides, pure gases atmosphere including N2, H2, CO, H2–CO were also tested to investigate the mechanism of the coal pyrolysis under different atmospheres. The pyrolysis products including gas, liquid and char were characterized, the result showed that, compared with the inert atmosphere, the tar yield is improved with the reducing atmospheres, as well as the tar quality. The hydrogen partial pressure is the key point for that improvement. In the atmosphere of H2, the tar yield was increased by 31.3% and the contained BTX (benzene, toluene and xylene) and naphthalene were increased by 27.1% and 133.4%. The double reactors pattern also performed outstandingly, with 25.4% increment of tar yield and 25.0% and 79.4% for the BTX and naphthalene. The double layers pattern is not effective enough due to the low temperature (700 °C) in which the Ni-based catalyst was not fully activated.