ABSORPSI SELEKTIF H2S DENGAN PELARUT NAOH

• Main Author: Nugra Baskoro, Ardian
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/48567
• Institution: Institut Teknologi Bandung

Natural gas is still the primary energy sources in Indonesia. One of its important processing steps is the removal of impurities in the form of CO2 and H2S (acid gas). Permen LH No. 13 of 2009 limits the amount of SO2 (H2S thermal oxidation product) emitted to the environment, which is 2,600 mg/Nm3. Therefore, selective separation of H2S from acid gas is very important. One of the separation methods applied is absorption with NaOH solvent. The addition of sodium carbonate (Na2CO3) and sodium bicarbonate (NaHCO3) buffer to NaOH solution can suppress CO2 absorption, thereby increasing the selectivity of H2S absorption. This study aimed to evaluate the effect of buffer addition to increase H2S absorption selectivity using NaOH. The experiment was conducted in ambient pressure and temperature. The simulated L/G range was 0.006 – 0.030. The evaluated feed gas composition representing the acid gas from one of the gas processing facility in Indonesia, which is 667,000 ppmv CO2 and 3,000 ppmv H2S in CH4. The concentration range of NaOH in the solvent is 1%-mass to 5%-mass. Sodium bicarbonate buffer was added with a mass ratio range of 0:1 to 3:1 to NaOH. Sodium carbonate buffer was added with a mass ratio of 1.26:1 to sodium bicarbonate. This study showed that buffer addition could increase H2S selectivity by suppressing CO2 absorption. An increase in the L/G ratio directly proportional with an increase in CO2 absorption, thus reduced the H2S selectivity. Based on the simulation results, in 0.006 – 0.030 L/G ratio range and greater than 2%-mass NaOH solvent concentration, the addition of NaHCO3 with a mass ratio greater than 1.5:1 to NaOH and the addition of Na2CO3 at 1.26 times NaHCO3’s mass proved to increase H2S absorption selectivity up to 17.3%. A combination of L/G ratio of 0.006 and a solvent with a composition of 5%-mass NaOH, 15%-mass NaHCO3, and 18.9%-mass Na2CO3 produced the highest H2S selectivity of 23.1 (H2S selecitivity increase of 379.7%). With respect to solvent solubility limitation and economic aspect, a combination of L/G ratio of 0.006 and a solvent with a composition of 5%-mass NaOH, 10%-mass NaHCO3, and 12.6%-mass Na2CO3 resulted on optimum H2S selectivity of 9,6 (H2S selecitivity increase of 123.1%).