Parametric study and optimization of an acid gas enrichment plant with outlet streams and energy usage consideration

Acid gas enrichment (AGE) is a new method to increase the H2S conversion in conventional Clause process. In this paper effect of methyl diethanolamine (MDEA) flow rate, MDEA temperature, acid gas flow rate, and AGE tower pressure on the outlet H2S and CO2 concentration and energy consumption have been studied. A novel procedure based on enthalpy of combustion in the reaction furnace and incinerator is conducted for energy consumption calculations. By changing MDEA and inlet acid gas flow rates, a maximum H2S concentration in the enriched stream could be attainable. Increasing MDEA temperature will decrease maximum H2S concentration and enriched acid flow rate; also, CO2 concentration in off-gas will be decreased. By increasing AGE pressure, maximum H2S concentration in the enriched stream will be diminished. At higher MDEA flow rates, lower AGE pressures will bring higher H2S concentration in enriched acid gas stream. According to flame temperature simulation in the reaction furnace, energy consumption is directly related to H2S concentration in the sulfur recovery unit (SRU) feed stream. Results show that maximum H2S concentration in the enriched acid gas stream has the best conditions from energy point of view. At optimum conditions, H2S concentration in enriched acid gas is 62.45 mol%, which has been increased by 24.8%, compared with existing plant conditions, and energy consumption has been decreased by 25.05 GJ/h, and CO2 concentration in off-gas is 94.94 mol%.