Comparison of Vapor Recompression and Bottom Flashing Methods in Energy Optimization of Natural Gas Sweetening Process

The sweetening of sour gas by amine solvent has attracted a lot of attention due to the high ability of amines to remove acidic compounds from natural gas. In this process, an adsorption column and a distillation column are used to recover the amine. The operating costs of the conventional sour gas sweetening process are very high due to the high energy consumption in the solvent recovery column. Therefore, process energy optimization is very essential. In this research, first, the conventional gas sweetening process was subjected to heat integration (HI) so instead of using utility in supplying process energy, the energy of process flows has been used. Then, the amine recovery column is thermally integrated into this process by Vapor Recompression (VRC) and Bottom Flashing (BF) methods. The results showed that the HI, VRC, and BF processes reduced energy consumption compared to the conventional process about 25%, 88%, and 90%, respectively. Although the compressor consumption of the VRC and BF processes is almost the same, the reduction in hot and cold utility consumption in BF is 33% higher than in VRC. So, the BF process performs better than the VRC process. Moreover, BF process could reduce total annual cost (TAC) of the base process in the maximum value of 96%. That is why BF process is selected as the best choice of heat integration in this case study.