Integrating heat pumps into CHP plants to support CO₂ capture

Abstract

Integrating CO₂ capture into combined heat and power (CHP) plants reduces heat and electricity generation. Heat pumps (HPs) can be utilized to recover waste heat for solvent regeneration or district heating (DH). However, no study compares different ways of utilizing recovered heat. Therefore, this study evaluated the performance of a HP-integrated CHP plant with CO₂ capture. Four cases were considered, Case 1 (reference case 1): without CO₂ capture; Case 2 (reference case 2): with CO₂ capture and no HPs; Case 3: with CO₂ capture and using HPs to recover heat for DH; and Case 4: with CO₂ capture and using HPs to recover heat for solvent regeneration. Using real operating data from a waste-fired CHP plant (50 MW_e, 110 MW_th), results demonstrated that, in Case 2 (cf. Case 1), maximum 81.6% of CO₂ was captured at a cost of 62.6% reduction in net electricity generation. In Case 3, 45.3% of the DH demand was covered by HP recovered heat, amounting 375.8 GWh/year. In Case 4, 78.3% of the heat required for CO₂ capture was supplied by HP recovered heat, reaching 445.1 GWh/year. While 90% of CO₂ was captured in Cases 3 and 4, the annual net electricity generation was reduced by 64.5% and 37.1%, respectively. Additionally, given current carbon trading prices, CO₂ capture was not economically feasible and that system’s internal heat recovery by HPs is not economically feasible, either.

Keywords

Waste-fired combined heat and power plant / MEA-based chemical absorption / Waste heat recovery / Heat pumps / Operation optimization

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Funding

Mälardalen University

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