Thermodynamic assessment of SNG and power polygeneration with the goal of zero CO2 emission.

The current coal-to-SNG (synthetic natural gas) projects are facing two main issues, addressing on insufficient energy utilization and large amount of carbon emissions. For this reason, we proposed a coal-based SNG and power cogeneration process, at the ability to achieve high-efficiency and achieve zero-energy-penalty separation of CO 2 , by incorporation with chemical looping combustion (CLC). The main objective of this paper is to estimate thermodynamic performances under the effects of key parameters in order to pre-examine whether the proposed process is thermodynamically viable. At optimal condition (oxygen to carbon ratio ( O/C)  = 0.4, steam to carbon ratio ( S/C)  = 0.8 and recycling ratio of unreacted gas (Ru)  = 3), the overall plant energy efficiency, exergy efficiency and energy saving ratio are 58.84%, 56.59% and 10.82%, respectively. The proposed process is compared with several traditional systems that aims to further demonstrate the superiority of such process design in terms of thermodynamic and preliminarily economic assessment. A sensitivity analysis is also included to examine the effects of different coal feedstocks and oxygen carriers of CLC on system performances. [ABSTRACT FROM AUTHOR]