Thermodynamic analysis of air-blown gasification for IGCC applications

This paper analyzes the thermodynamic performance of IGCC power plants based on an air-blown gasifier. A preliminary computational model for a lab-scale gasifier was calibrated on experimental data available in open literature, as a first step for the modeling of a large-scale MHI-type air-blown demonstration gasifier. The latter was analyzed by a parametric analysis, carried out by varying the gasification temperature and the heat transferred to the membrane walls. In agreement with data from MHI, the power balance of the air-blown gasifier suggests that the cold gas efficiency is similar to the one of oxygen-blown gasifiers, even though energy flows are quite different in the two gasification technologies. A complete IGCC power plant based on an air-blown gasifier is then proposed. Its predicted performance is compared to the one of a plant using an oxygen-blown Shell-type gasifier, calculated with coherent assumptions. The same state-of-the-art combustion turbine is selected as topping cycle in both the IGCCs. The overall power plant performance improves with the air-blown technology and the calculated net efficiency is a bit more than 1.5% points higher. Such a result, along with potential savings in terms of investment cost, could possibly determine lower costs of the electricity produced. Sankey diagrams of the energy flows, along with a second-law analysis, are discussed in the paper, to better understand the results provided by similar power cycle configurations, but with very different coal gasification technologies. (C) 2011 Elsevier Ltd. All rights reserved.