Thermodynamic analysis and economic evaluation of a novel coal-based zero emission polygeneration system using solar gasification

Abstract

• Solar penetration reduces coal consumption and upgrades the syngas quality. • Methanol yield and net power output increase by 94.2% and 22.9%, respectively. • Equivalent solar-to-methanol efficiency soars to 44.0% at the designate point. • The levelized energy cost of the methanol is 341.95 $/ton. Hybridization of solar energy with coal can effectively reduce the fossil fuel consumption and improve the solar conversion efficiency. A novel solar hybrid polygeneration system is proposed to convert the concentrated solar energy into stable chemical (methanol) and realize the zero emission of coal-based energy system. In the proposed system, the solar-driven coal gasification is innovatively integrated with a methanol and electric power polygeneration system using a direct-fired supercritical carbon dioxide power cycle (Allam cycle) for power generation and carbon capture. Detailed models based on material and energy balance are developed and the overall system thermodynamic performance is obtained by the process simulation. Results show that in the solar hybrid system, the solar integration can improve the methanol production and net power output by 94.2% and 22.9%, respectively; the fuel saving ratio is calculated as 35.8% with the solar contribution ratio of 25.3%; and the equivalent solar-to-methanol efficiency soars to 44.0% at the designate point. For the economic performance, the levelized energy cost of the methanol is obtained as 341.95 $/ton, 10.49% higher than that of the reference system. The solar integration can obviously boost the methanol yield and net power output in the zero-emission polygeneration system, and the solar-to-chemical efficiency in the hybrid system is much higher than that of the conventional stand-alone solar system. In addition, with the investment cost of the solar field decreasing and the coal price increasing, the solar hybrid system might obtain a better economic performance.