Utilization of Cold Energy of LNG for Carbon Dioxide Capture and Liquefaction in Amine-Based SMR

Abstract

Hydrogen is widely produced by a steam methane reforming (SMR) process, but CO 2 that is produced as a byproduct needs to be captured. For this purpose, amine absorption, one of the main carbon capture and utilization (CCU) techniques, is commonly integrated with the SMR process. A drawback of the amine absorption process is that captured CO 2 is recovered in the gas phase and must be liquefied or solidified to be suitable for transportation and storage. Traditionally, the liquefaction of CO 2 is achieved by a series of compression-cooling and expansions (e.g., the Linde−Hampson process), which is a costly and energy-intensive process. This study proposes using liquefied natural gas (LNG) not only as the source for hydrogen production and heat supply for the SMR reaction, but also to provide the necessary thermal energy requirement for the liquefaction of CO 2 using plate-fin heat exchangers. Aspen HYSYS is used to simulate a 300 Nm 3 /h scale SMR process, the amine absorber, and CO 2 Liquefaction processes. Energy, exergy, and cost efficiencies for a conventional Linde−Hampson process and two novel setups utilizing LNG cold energy are studied and compared. In summary, our results show the significant advantages of the proposed nonrecycling process over the conventional Linde−Hampson system. Specifically, it offers up to a 39.38% enhancement in overall exergy efficiency, achieves a net rational exergy efficiency as high as 95.72%, and reduces total capital costs by 30.83%.