Optimizing CO2 capture efficiency: integrating high temperature heat pumps to achieve 60% final energy reduction
This paper concerns a study on reducing the energy demand of an amine based CO2-capture process by applying a heat pump to this process. This work is part of the HEU project HiRECORD which aims to reduce the costs of CO2-capture. Applying a heat pump to the capture process allows for recovery and upgrading of waste heat within the system, therewith reducing the net energy demand and energy costs of operating this process. The target for final energy reduction was set at 60%. This translates to a required Coefficient of Performance (COP) for the heat pump of 2.5. Thermodynamic calculations have been carried out combining several waste heat sources within the process with the required heat demand of 130°C for the reboiler of the regeneration column. Data from a CO2 capture plant at a quick lime production plant, with a capture rate of 5.6 ton/h, has been used as input. The modelling work resulted in a heat pump concept with two parallel compressors, each using a different combination of waste heat sources from within the capture process. Isopentane (R601a) was selected as the working medium and an assessment was made on the availability of commercially available compressors for this heat pump. The required compressor properties with respect to pressure ratio and volume flow fit very well within existing compressors. The calculated COP is 2.76, meeting the target of the project. The specific regeneration energy of the CO2 capture plant is reduced from 3.29 GJth/ton to 1.29 GJel/ton, allowing for significant operational cost savings.