Towards net-zero energy penalty: District heating recovery and optimization in a CO2 capture unit in demonstration-scale

Retrofitting waste-to-energy facilities with CO 2 capture enables the production of carbon-negative electricity and district heating while treating residual solid waste streams. However, CO 2 capture imposes a large energy penalty, presenting economic challenges for energy generation facilities. This study presents the results from experimental optimisation campaigns at the demonstration-scale CO 2 capture unit at the Amager Bakke waste-to-energy facility, using 35 wt.% monoethanolamine (MEA). The liquid-to-gas ratio was optimised, and a systematic absorber intercooling (AIC) campaign was conducted, varying both intercooler placement and temperature. AIC configuration and setpoint selection were guided by objectives of reducing specific reboiler duty (SRD), improving the potential for heat recovery to district heating, and reducing NH 3 slip in the depleted flue gas. The SRD was largely independent of both intercooler configuration and temperature. The lowest energy consumption was found with dual intercooling at 3.5 m and 7.0 m packing height with an intercooler outlet temperature of 45 °C, where an SRD of 3.77 MJ kg −1 CO 2 was achieved. A synthetic district heating integration based on these results showed that optimal AIC temperature and configuration depend on district heating return temperature, suggesting that dynamic operations with adaptive AIC settings could cost-optimise operations through seasonal variations. • Optimized liquid-to-gas ratio reduced SRD by 18.6% to 3.73 MJ/kg CO 2 . • Absorber intercooling had minimal impact on SRD but affected NH 3 slip. • Higher intercooling temperatures increased NH 3 slip in depleted flue gas. • Synthetic district heating integration optimized waste heat recovery. • Dynamic intercooling settings could enhance seasonal energy efficiency.