New insight into Allam cycle combined with coal gasification in supercritical water

In this work, we proposed and investigated the power generation system where coal gasification in supercritical water is combined with Allam cycle (CAllam cycle). This CAllam cycle features zero pollutant emission, easy CO2 collection and no extra heating. Our simulations demonstrated the differences between the natural gas Allam cycle and our proposed CAllam cycle, and also elucidated the mechanisms underlying these differences. Results show that recycling CO2 not only reduces the temperature of gas turbine blades but also further improves the system efficiency. Results also show that the gas turbine outlet pressure corresponding to the maximum efficiency is smaller and away from the gas-liquid line. Furthermore, we graphically identified the combination of CO2 recycling ratio and gas turbine outlet pressure, that the CAllam cycle allowed. Built on these findings, our proposed CAllam cycle was optimized graphically. Taking 40 wt% Hongliulin coal as an example, the maximum system efficiency is 53.19% and the corresponding CO2 recycling ratio and gas turbine outlet pressure are 1.158 and 2.43 MPa, respectively.

Automated summary

In this study, we proposed and investigated a power generation system called CAllam cycle, which combines coal gasification in supercritical water with the Allam cycle. Our simulations compared the CAllam cycle with the natural gas Allam cycle and explained the underlying mechanisms of the differences. Results showed that recycling CO2 improved system efficiency and reduced gas turbine blade temperature. The optimized CAllam cycle achieved a maximum system efficiency of 53.19% with a CO2 recycling ratio of 1.158 and a gas turbine outlet pressure of 2.43 MPa, using 40 wt% Hongliulin coal as an example.