A Novel Coal Gasification System Through Thermochemical Regenerative Process of Syngas Sensible Heat to Enhance Cold Gas Efficiency

Abstract

In this paper, a novel coal gasification technology used for Integrated Gasification Combined Cycle (IGCC) power plants is proposed, in which a regenerative unit is applied to recover syngas sensible heat to generate steam and then the high temperature steam is used to gasify coke from pyrolyzer. Through such a thermochemical regenerative unit, the sensible heat with lower energy level is upgraded into syngas chemical energy with higher energy level, and therefore a higher cold gas efficiency (CGE) is expected. The Aspen Plus Software is selected to simulate the novel coal gasification system. Then the exergy and Energy-Utilization Diagram (EUD) analyses are applied to disclose the plant performance enhancement mechanism. It reveals that 83.2% of syngas sensible heat can be recovered into steam agent and so the CGE is upgraded to 90%. And with the enhancement of CGE, the efficiency of an IGCC plant based on the novel gasification system can be as high as 51.82%, showing a significant improvement compared to 45.2% in a Texaco coal gasification based plant. At the same time, the exergy destruction of gasification process is reduced from 132.5MW to 98.4MW through thermochemical reactions. Lift of accepted energy level (Aea), and decrease of released energy level (Aed) and heat absorption (ΔH) contribute to the exergy destruction reduction in the gasification process. Additionally, since oxygen agent is no longer used in the IGCC, 34.5MW exergy loss in the air separation unit is avoided. Thereby the novel coal gasification technology proposed in this paper has a good thermodynamic performance and may provide a quite promising way for high efficient and clean coal utilization.