A novel coal-based polygeneration system cogenerating power, natural gas and liquid fuel with CO2 capture

In this paper, a novel coal-based polygeneration system has been proposed, in which power, natural gas and liquid fuel are cogenerated and 62% of carbon is captured. Through proper adjustment instead of full adjustment of the syngas component, the CO/H₂ of the unreacted gas in methanol synthesis unit can exactly meet the CO/H₂ requirement for SNG synthesis, and thus cogeneration of methanol and SNG can be realized easily. By adopting partial recycle instead of full recycle of the unreacted gas in chemical island, the sharp increase of energy consumption for chemical synthesis can be avoided. On the other hand, part of the unreacted gas from methanol synthesis unit, which is hard to be converted, together with the recovery gas in chemical islands will be sent to combustion for power generation efficiently. At the same time, 62% of the carbon has been captured by low-temperature methanol wash method (LTMW) after concentration. As a result, the thermal efficiency of the novel system is around 54.9%, and the exergy efficiency is about 57.3%, which is much higher than the IGCC system, or single methanol synthesis system. Compared with the conventional single product systems, primary energy saving ratio of this novel polygeneration system can reach as high as 10.8 percent. Based on the graphical exergy analysis, the key processes of the new system are disclosed and the internal phenomena for high performance are revealed. The promising results obtained in this coal-based system may realize both the low-energy-penalty decarburization of coal and highefficient coal utilization, and will possibly provide a new option to enforce the safety of energy supply for countries with abundant coal resources but lack of natural gas and oils.