Exergy Analysis and Heat Integration of a Coal-Based Oxy-combustion Power Plant

Abstract

Oxy-combustion is a competitive technology to enable the capture of CO2 from coal-based power plants. The main challenge to implement this technology is the large energy penalty and investment cost related to CO2 capture. A comprehensive exergy analysis has been performed for an entire coal-based oxy-combustion power plant. The exergy flows and irreversibilities are presented. The thermal efficiency penalty related to CO2 capture is about 9.4 percentage points (on the basis of the higher heating value) and is mainly caused by the air separation unit and the CO2 compression and purification unit. The theoretical minimum is 3.4 percentage points when the two units are assumed to be reversible, where the air separation unit contributes 1.4 percentage points and the CO2 compression and purification unit is responsible for 2.0 percentage points. The compression processes are causing the largest exergy losses related to CO2 capture. The case studies show that the integration of the compression heat with the steam cycle can increase the thermal efficiency by up to 0.72 percentage points.