Full-Scale Reuse Treatment of Wastewater Produced by Oxidation-Absorption Technology of Tail Gas from Natural Gas Purification Plant

Abstract

Summary Tail gas oxidation-absorption technology which has been applied in natural gas purification plants of the southwest oil & gas field company can get super low SO2 emissions that is better than the discharge standard (GB39728-2020) in china, but it produces huge wastewater. In this paper, the oxidation-absorption technology of natural gas purification plants was described, and wastewater-producing regularity and pollution characteristics were studied in detail. A full-scale reuse treatment strategy of the produced wastewater which was based on the sequential combination of disc-tube reverse osmosis and evaporative desalination at low temperature & low-pressures was proposed, afterward water quality of the wastewater before and after the reuse treatment was investigated. In addition, produced salts were explored by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). With our proposed reuse treatment system, the chroma disappeared, and COD, BOD5, TOC, TN and SS decreased. Meanwhile, salts were produced after the evaporative desalination. They were characterized by FT-IR, SEM and EDS, and the results indicated that the salts were consisted of Na2SO4 but mixed with organic amines (i.e., amine-based SO2 absorbents). As a result, the produced water was reused by the current treatment system in a full-scale, and water quality can meet the national reuse standard (GB/T 18920-2020) in China, which is helpful for extending tail gas oxidation-absorption technology and reducing SO2 emissions in the world.