(155f) Practical Flue Gas Carbon Capture at Steam Crackers

“Post-combustion CO₂ capture” is a widely used technology for decarbonizing plants in various sectors, including industrial, chemical and power generating facilities. In the context of steam cracking plants, “Post-combustion CO₂ capture” can be understood as CO₂ capture from flue gas mainly originating from cracking furnaces and auxiliary steam boilers. The respective flue gases are routed through a column with circulating liquid solvent, which absorbs the CO₂ molecules. A heating medium like steam enables the adjacent regeneration column to release the highly concentrated CO₂ from the solvent, and the CO₂ is sent to a processing unit for further upgrade (e.g. drying, compression, liquefaction) to enable storage or utilization.

This paper evaluates steam cracker flue gas carbon capture using the example of mainly methane-fired cracking furnaces. The case of a world‑scale liquid cracker decarbonization is presented, where the CO₂ from the flue gases is captured utilizing the OASE^® blue process, which is mutually developed by BASF and Linde. It is demonstrated that the direct continuous CO₂ emissions from the furnace and boiler stacks can be efficiently removed by more than 95%.

The paper further outlines how existing cracker assets can be retrofitted with appropriate ducting to collect and route the individual flue gases to the capture facility. Despite being an elegant “add-on” solution for retrofitting existing facilities with relatively low impact to the existing fired capital equipment, flue gas capture units consume a noticeable amount of low-temperature heat. Energy-integration potentials between cracker and flue gas capture unit are highlighted, mitigating or even avoiding extra thermal energy demand and associated extra CO₂ generation.

Finally, cracker-specific system dynamics relevant to the flue gas carbon capture unit are analyzed and sound control strategies are revealed that ensure continued stable plant operation in dynamically changing scenarios.