Optimal design of a coal-based synthetic natural gas (SNG) process with different coal ranks and gasification technologies via techno-economic analysis

Abstract

Natural gas is regarded as a cleaner fuel and could be a feedstock for chemicals production. In some regions where petroleum resources are limited, the coal-based synthetic natural gas (SNG) process could be an alternative option. Generally, the coal-based SNG process begins with the gasification of coal to produce crude syngas, implying that coal rank and gasification technology would have a significant impact on the process performance and product quality. Within this work, a series of coal-based SNG processes with different coal ranks and gasification technologies are investigated and analyzed based on rigorous process modeling and simulation. Sensitivity analysis is carried out to optimize key parameters and explore their effects on process performance. The results indicate that the low-rank coal with the Lurgi gasifier could effectively improve the energy conversion efficiency when compared with various combinations of coal ranks and gasification technologies. The lignite coal with the Lurgi gasifier could improve the energy efficiency up to 61% with a Wobbe index of 52 MJ/m3, a carbon yield of 44%, and the minimum CO2 emission of 3.5 kgCO2/kgSNG. The economic evaluation suggests that the total equipment investment for the process based on lignite is 20% and 27% lower than that based on bituminous and anthracite, respectively. Furthermore, the Lurgi gasifier could save 12% equipment investment compared with the Texaco gasifier when the process is based on the same coal rank. The research could provide quantitative guidance for the design and optimization of coal-based SNG processes.