Abstract: By analyzing the problems of high caustic consumption and large spent caustics discharge in the treating system of LPG sweetening process, the caustic scrubbing process of each LPG sweetening unit was improved and a spent caustics regeneration unit was added, and the total sulfur concentration of refined LPG in each unit is not more than 20 mg/m³, the product quality is significantly improved, and the consumption of fresh caustic solution and the discharge of caustic residue are significantly reduced. Through utilizing the old fiber membrane caustics CO₂ neutralization device, the caustics wet oxidation unit can be stopped, realizing zero discharge of caustics.

Key words: liquid gas, sweetening, caustic solution, spent caustics, zero discharge