Impact of Changing Mdea Parameters on Absorption of H2S and CO2 and its Implications—A Case Study of Hazira Plant

Abstract

ABSTRACT On account of the poisonous nature of Hydrogen Sulphide (H2S) gas, removal of H2S or sweetening of natural gas is one of the most critical activities in gas processing. For sweetening of natural gas, Methyl Di-Ethanol Amine (MDEA) is successfully used all over the world. In MDEA based gas sweetening units, removal of H2S is carried out in the Absorber Column using counter – current principle. Due to acidic nature of H2S and CO2 both, removal of H2S is accompanied by absorption of CO2 by MDEA. For regeneration, MDEA is heated in the Regeneration Columns where H2S and CO2 both are liberated as Acid Gas. The basic aim of the gas sweetening process is to remove H2S almost completely with minimum absorption of CO2 in MDEA in order to reduce the quantum of Acid Gas generation. To achieve these objectives temperature, concentration and flow rate of MDEA solution along with contact time and other operational parameters are adjusted and optimized. For improving the effectiveness and efficiency of the process, a study on Impact of changing MDEA parameters (temperature and concentration) on absorption of H2S and CO2 was carried out. The study revealed that with change in parameters of MDEA, the H2S content and the CO2 content of rich MDEA changed appreciably. Hence by proper optimization of different parameters the absorption of H2S and CO2 in MDEA can be controlled to suit to our need and operational limitations. CO2 alone accounts for nearly 90 % of the volume of the acid gas. Restricting the absorption of CO2 in MDEA column itself can control the generation of acid gas. Lower temperature of MDEA along with lesser contact time will mitigate the dissolution of CO2 in MDEA solution. As in CO2 - MDEA reaction, the rate determining process is the dissolution of CO2 in water, by merely restricting the dissolution of CO2 in water, volume of acid gas generated can be reduced. Hence by maintaining proper parameters of MDEA solution, effective removal of H2S along with controlled generation of acid gas is possible which in turn can mitigate several operational problems. Controlled generation of acid gas will not only lessen the load of acid gas treatment but will also have significant financial implications.