Efficiency improvement, consumption reduction and optimization of high-sulfur natural gas sweetening units

Abstract

To increase purified gas production and reduce the comprehensive energy consumption of high-sulfur natural gas sweetening unit, a process simulation model was established by using ProMax based on the field operation data in the Sinopec Puguang Natural Gas Purification Plant. Then, sensitivity analysis and optimization study were carried out on the main operating parameters, including circulation rates, the concentrations and the inlet temperatures of primary and secondary absorption towers of MDEA (methyldiethanolamine) solutions. Furthermore, the effects of reduction of the feed gas load and pressure and increasement of H2S content on the quality and yield rates of purified gas were analyzed under the optimized operating conditions with the actual field situations. And the following research results were obtained. First, the absorption selectivity of MDEA solutions can be improved by decreasing the circulation rates, concentrations and inlet temperatures of MDEA solutions, which is favorable for the increase of the yield rates of purified gas. Specifically, the circulation rate of MDEA solution is the main factor influencing the comprehensive energy consumption of a high-sulfur natural gas sweetening unit. Second, when the flow rate, pressure and H2S content of feed gas fluctuate, the purification requirements can be satisfied under the optimized operating conditions. Third, energy conservation under low flow rates of feed gas can be achieved by reducing the flow rates of regenerated steam and adjusting the position of MDEA solutions entering the secondary absorption tower. Fourth, as H2S content is increased by 1%, it is necessary to increase the circulation rate of MDEA solution by about 20 × 103 kg/h. Fifth, after parameter optimization, the yield rate of purified gas is increased by 0.5% and the comprehensive energy consumption is reduced by 19.1% under the operating condition of full load.