Process Analysis of Chemical Looping Systems for Dimethyl Ether Synthesis from Coal

Coal is an essential primary energy source in modern industry. An important pathway of coal utilization is to gasify coal into syngas, which is then used for downstream production of numerous chemicals such as methanol and liquid fuels. Despite its wide applications, conventional coal gasification still faces challenges such as the use of a costly air separation unit and limited syngas H2/CO ratio. Chemical looping gasification technology is a promising alternative to replace conventional coal gasification with increased thermal efficiency and higher level of process intensification. This study presents the process analysis of chemical looping coal gasification and its integration with downstream production of dimethyl ether (DME) to reveal the advantages of the chemical looping scheme compared to conventional gasification schemes. This study discusses the simulation strategies to maintain adiabatic operation in the chemical looping system. The operating parameters of the chemical looping system are adjusted to achieve the maximum cold gas efficiency in one case study, while the operating parameters of the chemical looping system are adjusted to achieve the maximum effective thermal efficiency in another case study. These two chemical looping cases involve the integration of the chemical looping system with the DME synthesis in a process that considers overall process material and heat flows and power consumption and generation. An exergy analysis is also conducted for these two integrated chemical looping cases, revealing that they both can achieve around 10% increase in exergy efficiency over the conventional gasification system.