Coal to dimethyl ether based on a new gasification technology by decomposing C and H components

This paper proposes a novel coal to Dimethyl Ether (DME) system based on a new gasification technology by decomposing C, H components. In the novel system, coal is gasified through three steps: Coking, char-CO2 gasification and water gas shift & CO2 separation, and three gases including coke oven gas, pure H2 and CO are produced, instead of one gas containing CO and H2. Furthermore, the additional work for air separation is avoided by substituting CO2 for O2. Based on the TGA, reasonable conditions for coking (1 bar, 1100°C) and CO2-char gasification (30 bar, 1100°C) are obtained. Under those conditions, the novel coal to DME system is simulated by Aspen Plus and the energetic and exergetic analysis are presented. It shows that the simulated energy utilization efficiency reaches up to 61.8%, which is 12.8 percentage points higher than that of traditional system. By the aid of energy utilization diagram (EUD) analysis, the internal irreversible mechanisms of key processes are revealed. It turns out that the performance improvement of the novel system mainly comes from two aspects – a significant reduction in exergy destruction of coal gasification and syngas heat recovery unit, and elimination of air separation unit.