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.

► Air-blown IGCCs are investigated starting from a model of an air-blown gasifier.
► Air-blown and oxygen-blown gasifiers have similar cold gas efficiency.
► Different coal gasification technologies are better understand by means of Sankey diagrams.
► The overall IGCC performance improves with the air-blown technology.
► Potential savings in terms of investment costs determine lower electricity costs.