| Summary: | This work explores the potential for use of carbon dioxide separation processes, colloquially known as carbon capture, to accelerate decarbonization of the transport sector. Thermal swing absorption processes using an aqueous, CO2-selective solvent, provide an efficient means of separating CO2 from other exhaust gas constituents. Amine-based solvents–well known from acid gas treating and other post-combustion carbon capture processes–are highly selective, have a fast rate of reaction with CO2, and can use waste heat to drive the separation process. This work demonstrates how amine-based processes can be deployed for carbon removal from a generic exhaust gas source produced by an internal combustion engine (ICE) using waste heat in the exhaust. It includes an estimation of the exhaust enthalpy-limited capture rate for various sources considering the capture system performance, the CO2 concentration, and the exhaust temperature.CO2 capture rates of around 25–80% are shown to be thermodynamically feasible for various ICE applications using waste exhaust heat for solvent regeneration. Rates of around 15–50% are attainable without providing additional energy, if exhaust heat is also used to power the capture system pump and compressor. Although a higher exhaust CO2 concentration reduces the specific energy requirements of the separation process, the total energy required for a given capture rate increases due to the greater amount of CO2 removed. Thus, maximum capture rates are highest for applications with high exhaust temperature and low CO2 concentration (such as diesel generators), and lowest for applications with very low exhaust temperature such as ships. This analysis also shows that the potential for CO2 avoidance using carbon capture systems far exceeds that of organic rankine cycle waste heat recovery systems. Overall, expanding the use of carbon capture to ICE applications can provide an efficient means of utilizing waste exhaust heat while providing significant reductions in the energy industry's scope 3 greenhouse gas emissions.
|
|---|