Techno-economic assessment of high temperature heat pumps integrated in MEA-based post-combustion CO2 capture for cement plant

Abstract

This study presents a techno-economic assessment of solvent-based (MEA) post-combustion CO₂ capture integration within cement production process, exploring both conventional natural gas (NG) boiler configurations and innovative high-temperature heat pump (HTHP) solutions for thermal energy supply. Heat Pumps exploit the low-temperature waste heat from the cement plant and the capture unit as thermal source in the evaporator. The following options are assessed, either individually or in combination, as alternatives to the boiler for providing the steam required for solvent regeneration: (i) a lean vapor compression (LVC) system integrated within the capture process itself; (ii) a closed Reverse Rankine heat pump; (ii) a cascade system combining a bottoming closed-loop reverse Rankine cycle heat pump with a topping mechanical vapor recompression (MVR) system. Process simulations and equipment sizing are performed with a validated rate-based model of the absorption process in Aspen Plus and the economic analysis is carried out with a referenced bottom-up methodology. The cost-effectiveness of each technology is evaluated in terms of cost of CO₂ avoidance (CCA), clinker cost increment (∆CC) and cost of CO₂ capture (COC). For the conventional steam supply with NG boiler, two positions for the capture plant are assessed: tail end (Case #1 - Tail end) and integrated upstream the raw mill (Case #2 - Integrated). The best configuration with steam generation via NG boiler is case #2 with LVC at a flash pressure of 0.8 bar, resulting in an incremental cost of clinker of 62.1 €/t_clk and a CCA of 149.6 €/t_CO2. The integration of HTHPs offers significant benefits in terms of energy efficiency and cost competitiveness. The comparative evaluation of multiple HTHP configurations, including reverse Rankine cycle heat pumps and mechanical vapor recompression (MVR) systems, shows that the most viable solution is an MVR-based HTHP combined with LVC. Fuel consumption for solvent regeneration of around 100 MW_th is replaced by an additional electricity demand of 26.9 MW_el in the best case. The CO₂ avoidance rate of the overall cement plant is reduced from almost 91 % to 89 % due to the increased Scope 2 emissions, with the assumed electricity carbon intensity of 100 kg_CO2/MWh. With baseline NG and electricity prices of 40 €/MWh and 100 €/MWh respectively, the cost of CO₂ avoidance and incremental clinker cost are 125.9 €/t_CO2 and 42.1 €/t_clk, respectively. These findings provide insights into the techno-economic trade-offs of integrating carbon capture in cement plants and underscores the potential role of HTHPs in helping the decarbonization of this sector. Sensitivity analyses on key parameters affecting energy balance and costs are included to highlight how the competitiveness and costs of the different solutions vary under different assumptions or market conditions.