Analysis of IGCC-Based Plants with Carbon Capture for an Efficient and Flexible Electric Power Generation

Abstract

In this work, systems based on the Integrated gasification combined cycle (IGCC) technology with carbon capture are analyzed regarding an efficient and flexible electric power generation. All analysis are related to a high-efficiency or low-cost IGCC base case with carbon capture which are both commercially available. In the high-efficiency base case, thermodynamic inefficiencies are determined based on a conventional exergy analysis. The gasifier followed by the combustion chamber of the gas turbine running on syngas are rated to the largest inefficiencies. Based on an advanced exergy analysis, the inefficiencies are split into an avoidable and unavoidable part as well as an endogenous and exogenous part. For example, it was found that about half of the inefficiencies within the gasifier are caused by other components of the overall system (exogenous part). Further investigations on the combination of both splitting types are presented. The gas turbine system is identified to be a major component and therefore a detailed model was developed using state-of-the-art technologies. Based on this model, 12 types of characteristic inefficiencies were determined and rated by their exergy destruction. Chemical-Looping Combustion (CLC) is one of the most promising technologies to enhance the available IGCC design. CLC uses composite metal particles acting as an oxygen carrier to transport oxygen from the air to the fuel gas through a redox-cycle. Thus, the inefficiencies associated with the combustion process decrease and the application of physical absorption for capturing CO2 is replaced by an inherent CO2capture. In this work, the most suitable oxygen carriers for CLC using syngas (nickel oxide and iron oxide) are analyzed at different temperatures. Moreover, different types of gasifier as well as CLC reactor designs are analyzed. Regenerating the oxygen carrier by steam and air, produces additional hydrogen from the reduction of steam which is further combusted within the gas turbine. Particularly, the development of the novel process design focuses on optimizing the heat exchanger network under specific constraints. The final results show a minor potential for improvement. Economic benefits are potentially generated by a transition from a base load to a flexible operation of IGCC plants. In this process, the operation of the syngas production path remains constant while the generation of electricity depends on the market price. Subsequent to an additional purification of the common syngas, the product gas consists of almost pure hydrogen which can be sold in times of low electricity prices. The profit is estimated considering major relevant impact factors.