Integration of sorbent-based direct air capture into combined heat and power plants with post-combustion carbon capture

Combined heat and power (CHP) plants that provide district heating are underutilized due to seasonal variations in heat demand. This work provides an assessment of the techno-economic potential of integrating sorbent-based direct air capture (s-DAC) into CHP plants in district heating systems, so as to expand the business portfolio of the plant and increase its utilization. The proposed integrated system utilizes the existing CHP infrastructure to provide heat at 100°C, and high-temperature heat pumps to upgrade available waste heat from a post-combustion carbon capture (PCC) unit, so as to drive a s-DAC process. A bottom-up framework methodology is used to quantify the carbon dioxide removal (CDR) potential of the proposed system and identify the optimal design and operation, while considering cost optimization with respect to fuel type, district heating demand, the extent of heat recovery within the plant, heat and electricity prices, and carbon removal prices. The results show that for a 167-MW reference plant with PCC, integration of a s-DAC process that is dimensioned for maximum removal (i.e., not optimizing the economics but instead prioritizing the extent of carbon removal) provides additional carbon removal from the atmosphere of 162.7 ktCO 2 /y. A net-positive cash flow is attained at CDR credit prices in the range of 279-685 €/tCO 2 (reflecting zero heat recovery to full heat recovery). For profit-driven operations, the results indicate that for a CDR credit price of 615 €/tCO 2 , s-DAC and PCC contribute 11.8% and 67.1%, respectively, of the total yearly net cash flow of the plant. • Process integration and plant optimization for direct air capture integrated to combined heat and power plant. • Assessing trade-off between using heat for district heating and carbon dioxide removal. • Recovering heat from post combustion capture unit for district heating and operation of Direct air capture. • Cash flow analysis for assessing the break-even carbon removal credit price. • Carbon dioxide removal can contribute to 68% percent of net cash flow for combined heat and power plants.