Performance Improvement of Gas Sweetening Units by Using a Blend of MDEA/PZ

Abstract

This work investigates three gas sweetening units in Libya; particularly, Mellitah complex, Alestiklal, and Sahel gas plant. These units are designed mainly to use Methyl diethanolamine (MDEA) as a solvent for the removal of H2S and CO2 from the raw gas. Thus, the handling of higher gas production rates for the forthcoming years is a bottleneck without being upgraded. This work aims to increase throughput and reduce operating costs while maintaining the product quality of these units. HYSYS simulation was used to simulate the processes, assess the potential advantages of using a blend of MDEA and Piperazine (PZ), and investigate important parameters in the process. Results show that the MDEA/PZ blend provides high-performance as a gas treating solvent. The raw gas flow rate can be increased from 16,208 kmol/h to 18,820 kmol/h in the Mellitah complex with specs of 1.98 vol % CO2 and 0.9915 ppm H2S. In the Alestiklal gas plant, the flow rate can be increased from 8,012.79 kmol/h to 8,750 with specs of 0.975 Mole % CO2. But Sahel gas plant had a different behaviour, where the addition of Piperazine led to deviation of H2S from the required specification. The value of H2S reached 25.944 ppm, and the percent of CO2 was 1.347 Mole %. However, the decrease of the amine temperature reduces H2S to 13.76 ppm and CO2 to 1.276 Mole %. These results demonstrate the potential for significant improvements in increasing throughput via the use of PZ as an activator to the MDEA.