Comprehensive Exergy Analysis of Three IGCC Power Plant Configurations with CO2 Capture

Nicholas Siefert,Yang Chen,Sarah Narburgh

doi:10.3390/en9090669

Abstract

We have conducted comprehensive exergy analyses of three integrated gasification combined cycle with carbon capture and storage (IGCC-CCS) power plant configurations: (1) a baseline model using Selexol™ for H2S/CO2 removal; (2) a modified version that adds a H2-selective membrane before the Selexol™ acid gas removal system; and (3) a modified baseline version that uses a CO2-selective membrane before the Selexol™ acid gas removal system. While holding the coal input flow rate and the CO2 captured flow rates constant, it was determined that the H2-selective membrane case had a higher net power output (584 MW) compared to the baseline (564 MW) and compared to the CO2-selective membrane case (550 MW). Interestingly, the CO2-selective membrane case destroyed the least amount of exergy within the power plant (967 MW), compared with the Baseline case (999 MW) and the H2-membrane case (972 MW). The main problem with the CO2-selective membrane case was the large amount of H2 (48 MW worth of H2 chemical exergy) remaining within the supercritical CO2 that exits the power plant. Regardless of the CO2 capture process used, the majority of the exergy destruction occurred in the gasifier (305 MW) and gas turbine (~380 MW) subsystems, suggesting that these two areas should be key areas of focus of future improvements.

Highlights

Global demand for electricity has been increasing and likely will continue to increase, especially as new and existing technologies are adopted globally
There is a net power decrease of approximately 6 basis points when adding CO2 capture and compression. Most of this net power reduction is due to the fairly high exergy in the CO2 stream leaving the power plant in the CO2 storage pipeline (15 MPa), whose pressure is significantly higher than both the partial pressure of the CO2 in the environment (40 Pa) and the partial pressure of CO2 in the flue gas stream from a coal power plant (15 kPa.) For example, our results later in this paper find that the exergy in the supercritical CO2 leaving in the CO2 pipeline is approximately 5% of the exergy in the inlet coal
This paper presents comprehensive exergy analyses on three integrated gasification combined cycle (IGCC)-carbon capture and storage (CCS) power plants: (a) a baseline model using SelexolTM for H2 S & CO2 capture; (b) a modified version that incorporates a H2 -selective PBI-membrane operating at 250 ◦ C; and (c) a modified version that incorporates a CO2 selective membrane

Summary

Introduction

Global demand for electricity has been increasing and likely will continue to increase, especially as new and existing technologies are adopted globally. With rising global temperatures and sea levels due to rising greenhouse gas concentrations in the atmosphere, there is a crucial need for eliminating greenhouse gas emissions from fossil-fueled combustion in order prevent future environmental and economic damage [1]. Agency (EPA) finalized the “Clean Power Plan”, which aims to cut carbon emissions thirty percent from what they were in 2005 by 2030 [2]. This plan determines emission standards for pre-existing power plants [3] and sets a limit of 636 kg (gross) of CO2 emissions per MWh from new coal-based power plants, averaged over the lifetime of the power plant [4]

Methods

Results

Conclusion