Process Optimization in Gas Sweetening Unit - A Case Study

Abstract A number of process parameters can be considered to optimize amine sweetening units for smooth operation and better H2S absorption. The performance is often very sensitive to one or more of the operating parameters: inlet gas temperature, circulation rate, lean amine temperature, amine concentration, number of contact stages, pressure and temperature of regenerator etc. These parameters have direct or indirect impact on H2S absorption, CO2 absorption, foaming, amine degradation, corrosion rate and reboiler duty. Amine degradation products lead to a number of operational problems and increase process losses. Amine degradation and formation of heat stable salts can be minimized by fine adjustments of parameters. In this paper a parametric analysis of operating parameters with respect to Gas Sweetening Unit, Hazira Gas Processing Plant, ONGC, Hazira is carried out. It is the largest gas processing plant in India, processing 42 MMSCM sour gas per day. Inlet gas contains 160 to 200 ppm H2S which is sweetened below 4 ppm using Methyl Di-ethanol Amine (MDEA) for selective absorption of H2S from sour natural gas. Based on currently operating facilities some guidelines for optimizing gas sweetening units are presented. Introduction Amine solvents are used for removal of acidic components such as CO2 and H2S from natural gas to comply with the sales gas specifications. MDEA has an advantage of selective absorption capacity. In selective absorption H2S is selectively absorbed from the gas leaving a large amount of CO2 in the gas. The performance of MDEA system largely depends on the operating parameters. Experience has shown that with fine balance of different parameters operational problems can be minimized and a high level of performance can be achieved. Considerable savings can be realized with no capital cost through process optimization without sacrificing operational stability and flexibility. Downtime and process losses are reduced due to less operational problems.