(724f) Heat Integration of Absorption-Based Carbon Capture Processes in the Industrial Sector

The industrial sector is struggling with the difficult switch to renewable feedstocks, since the generated carbon is sometimes inherent in their processes or a part of their product. Therefore, carbon capture and storage (CCS) performed in the industrial sector has gained increasing attention recently, and most research is aimed at absorption-based capture processes. The largest cost for post-combustion CCS when applied at a power plant is the cost of regeneration of the absorbent, but industrial plants often have vast amounts of excess heat that can be utilized in the capture process. The focus of this paper is, therefore, heat integration of absorption-based carbon capture in the industrial sector. Models of two capture processes, using monoethanolamine (MEA) or ammonia as absorbents, were evaluated on the basis of how suitable they are for generic, industrial applications, depending on the availability and quality of the excess heat at the industrial site, and the temperature in the stripper reboiler. Models of the two processes have been constructed in Aspen Plus using a temperature interval of 90 â?? 120 °C for MEA and 105 â?? 155 °C for ammonia, and have been presented in previous work.

The study then continues with a heat integration case study of an oil refinery situated on the west coast of Sweden, emitting 1.8 Mt CO₂/yr from the four main chimneys. Over 100 coolers, using air or water as a cooling medium, are present at the refinery, providing cooling in the proximity of 500 MW. Because a system where over 100 new units are installed would be very complex and expensive, the possibility of installing fewer heat exchangers while having an acceptable loss of the available excess heat was investigated. Both the MEA and the ammonia process were evaluated based upon the levels of heat that resulted from this investigation.

The results point at a maximum heat recovery temperature of 108 °C for ammonia, and for MEA there is a boundary solution at the lower boundary of the investigated temperature interval, 90 °C. MEA could capture more CO₂ than ammonia using only excess heat, and techno-economic calculations were then made for the implementation of the MEA process in the oil refinery, including the cost for excess heat collection. The calculations comprise of the cost of the MEA process at both boundary temperatures in the stripper-reboiler, 90 °C and (standard) 120 °C, at two different sizes, and CO₂ concentrations. Compared to estimates where excess heat is not considered, the cost for carbon capture was decreased by up to 40 %.