CO2 Capture and Use in a Novel Coal-Based Polygeneration System

A novel coal-based polygeneration system with CO2 recycling for CO2 capture is proposed. Two CO2 recycling schemes exist in this system. In the first, CO2 is recycled into the gasifier as the gasifying agent. In the second, CO2 is recycled into the gas turbine as a diluent. Compared with conventional CCS systems, this new system avoids the use of water gas shift and CO2 separation processes to capture CO2, and, more importantly, a part of CO2 can be converted into CO in coal gasification and be used to synthesize chemicals, improving carbon element utilization and chemical output. By means of exergy analysis, comparison with four conventional single production systems shows that the proposed system provides more than 11% in energy savings and more than 25% in capital investment saving. The exergy efficiency, CO2 emission, and internal rate of return may be expected to reach 46.3%, 0.47 t.(t-coal)(-1) and 14.76%, respectively.