Improving plant-level heat pump performance through process modifications

Heat pumps are a promising option to decarbonize the industrial sector. However, their performance at plant-level can be affected by other changes in the plant. In this work, process changes that can improve the heat pump’s performance have been explored with Process Change Analysis (PCA) and the newly introduced split exergy grand composite curve. This approach shows the impact of the process changes on the heat pump work requirements by studying the position of the heat pump in relation to the pinch point of the background process. Its application is demonstrated in two case studies. In the first it allowed to identify technologies that enhance heat pump performance and while reducing overall heating requirements. In a biodiesel production plant, a heat pump transfers 1.9 MW with a COP of 4.2 but incurs a 40 kW penalty for transferring heat above the background process's pinch temperature. Replacing the wet water washer with a membrane separation unit avoids this penalty, while drastically reducing energy requirements from 0.9 MW to 0.3 MW. Secondly, the PCA showed how the extraction of heat in vinyl chloride monomer-purification process impacted the formation of the background pinch, from which an implementation strategy was derived that increased the heat pump’s plant-level performance by 6.5% in respect to standard implementation.