Thermodynamic Assessment of a Novel Concept for Integrated Gasification Chemical Looping Combustion of Solid Fuels
2012
Zhang, Yongxing | Doroodchi, Elham | Moghtaderi, Behdad
A novel integrated gasification chemical looping combustion (IGCLC) process is proposed here for combustion of solid fuels, particularly coal. The proposed process incorporates an ex situ step for gasification of the solid fuel, but unlike conventional ex situ methods, the gasification process is fully integrated with the combustion process. This is achieved using a three-step chemical loop for the production of hydrogen, combustion of gaseous fuels, and regeneration of metal oxides. A detailed thermodynamic chemical equilibrium assessment of the IGCLC process was carried out to evaluate its technical viability. The relevant analyses were performed using Aspen Plus process simulation software. The IGCLC process was found to be thermodynamically feasible. More specifically, it was uncovered that the gasification process can operate at an adequate temperature (above 1023 K) at thermoneutral conditions with high coal conversion (95%). It was also found that, to achieve the highest hydrogen production, the steam/hydrogen to carbon ratio (SHTCR) had to be set to 2, at which the gasification temperature was around 1070 K, coal conversion was 95%, gaseous fuel reactor (i.e., combustor) temperature was 1140 K, and H₂ productivity was 0.85 mol/mol carbon. Mass and energy balance calculations were also performed. It demonstrated that the proposed IGCLC system can achieve an electricity efficiency of 49.5% at SHTCR ∼ 2 and feed temperature of 1100 K with some appropriate assumptions, which is 80% higher than a conventional coal-fired power station with carbon capture and storage (CCS) measures.
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