Exergy Analysis of a Syngas-Fueled Combined Cycle with Chemical-Looping Combustion and CO2 Sequestration

Álvaro Urdiales Montesino,Ángel Jiménez Álvaro,Rafael Nieto Carlier,Javier Rodríguez Martín

doi:10.3390/e18090314

Álvaro Urdiales Montesino, Ángel Jiménez Álvaro + Show 2 more

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https://doi.org/10.3390/e18090314

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Journal: Entropy	Publication Date: Aug 25, 2016
Citations: 20	License type: CC BY 4.0

Affiliation: Universidad Politécnica de Madrid

Abstract

Fossil fuels are still widely used for power generation. Nevertheless, it is possible to attain a short- and medium-term substantial reduction of greenhouse gas emissions to the atmosphere through a sequestration of the CO2 produced in fuels’ oxidation. The chemical-looping combustion (CLC) technique is based on a chemical intermediate agent, which gets oxidized in an air reactor and is then conducted to a separated fuel reactor, where it oxidizes the fuel in turn. Thus, the oxidation products CO2 and H2O are obtained in an output flow in which the only non-condensable gas is CO2, allowing the subsequent sequestration of CO2 without an energy penalty. Furthermore, with shrewd configurations, a lower exergy destruction in the combustion chemical transformation can be achieved. This paper focus on a second law analysis of a CLC combined cycle power plant with CO2 sequestration using syngas from coal and biomass gasification as fuel. The key thermodynamic parameters are optimized via the exergy method. The proposed power plant configuration is compared with a similar gas turbine system with a conventional combustion, finding a notable increase of the power plant efficiency. Furthermore, the influence of syngas composition on the results is investigated by considering different H2-content fuels.

Highlights

The carbon capture and storage (CCS) is seen as a potential option for the mitigation of the greenhouse gas (GHG) emissions produced by power generation
The high energy penalty involved in the separation of carbon dioxide from a gaseous stream seriously questions the viability of CCS in thermal power plants in practice
The simulation of the chemical-looping combustion (CLC)-based combined cycle power plant shown in Figure 2 has been carried out relying on the PATITUG library, an own software for thermodynamic analysis developed by the Applied Thermodynamics Group of the Technical University of Madrid

Summary

Introduction

The carbon capture and storage (CCS) is seen as a potential option for the mitigation of the greenhouse gas (GHG) emissions produced by power generation. The high energy penalty involved in the separation of carbon dioxide from a gaseous stream seriously questions the viability of CCS in thermal power plants in practice. Conventional separation methods, such as separation by membrane, chemical absorption or adsorption and cryogenic separation are used, e.g., Chiesa and Consonni [1] describes a capture method via amine chemical absorption in the case of a “post-combustion” strategy. In the thermochemical gasification of solid fuels, a previous decarbonization to a mixture of gases (synthesis gas or merely syngas), mainly composed of H2 , CO and CO2 and impurities, takes place In this case, a “pre-combustion” strategy is preferred, since CO2 is quite more concentrated in the syngas than it is in the air after combustion.

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