A proposed coal-to-methanol process with CO2 capture combined Organic Rankine Cycle (ORC) for waste heat recovery

Coal-to-methanol (CTM) is the main methanol production process in China. Application of carbon capture and storage (CCS) technology in CTM is a possible way for CO2 reduction. However, the increase of energy consumption caused by CCS and related increase of Green House Gas footprint has to be minimised. This paper presents a CTM combined with CO2 capture and Organic Rankine Cycle (ORC) power generation, which improves energy efficiency simultaneously. The electricity generated from ORC is through the thermodynamic cycle converted the waste heat recovered from the CO2 compression and water gas shift unit in CTM process. The proposed process is simulated and analysed from energy efficiency and economic viewpoints. The analysis indicates several points: (1) Heat Integration of CO2 compression and water gas shift unit produce the heated water as the heat source of ORC; (2) With the CO2 ratio of 60%, the energy efficiency of the proposed CTM combined ORC system is 45.5%; (3) From economic point of view, electricity generated from waste heat conversion is around 4.8 MW, and the payback period of the ORC invested in CTM with CO2 capture process is 2.7 y.