Techno-economic and environmental analysis of coal-based synthetic natural gas process in China

Abstract

Coal-based synthetic natural gas (SNG) has the potential to make a significant contribution to China's natural gas market. The present study addresses a techno-economic and environmental assessment of large-scale coal to SNG process. To decipher the difference performances of the coal-based SNG projects, three major coal-based SNG production regions in China are considered. To obtain the mass and energy balances, detailed process models are developed and overall flowsheet is simulated. On this basis, economic performance and environmental impacts are systematically analyzed based on the criteria including capital investment, production cost, breakeven price, carbon footprint, and water footprint. The economic analysis indicates that the average breakeven SNG price is 2.2 CNY/Nm3, and corresponding breakeven crude oil price is 62 USD/bbl. Under the current oil price, developing SNG projects potentially lead to severe economic risk. The cradle-to-gate boundary of environmental impacts analysis shows that coal to SNG processes suffer from high carbon footprint and water footprint: the GHG emissions is 4.80–5.02 kg CO2-eq per Nm3 SNG, and the water consumption is 12.2–16.0 kg per Nm3 SNG. The GHG emissions can be mitigated by CO2 capture and storage(CCS), but it would lead to production cost increasing by 0.53 CNY/Nm3. In conclusion, although coal-based SNG projects can relieve the tense situation of supply and demand of natural gas, the capacity should be tightly controlled from the aspect of both economic competitiveness and environmental impacts.