Abstract: Caustic sludge generated from refinery and ethylene plant is considered as waste which contains excessive amount of alkaline, COD, sulfide, salt and nonbiodegradable organic compounds. It is suitable to be pretreated first and then into the sewage treatment field. Sulfuric acid neutralization-acidification is a a simple and traditional pretreatment method with low investment and operating cost, which can remove sulfide and several organic matters. However COD is still high and a large amount of malodorous gases is produced in the neutralization process. Increasing the extraction or biological aeration pretreatment on the basis of neutralization acidification can improve the COD removal rate, but still does not solve the problem of odor pollution. Wet air oxidation-SBR (sequencing batch reactor activated sludge process) pretreatment method has solved the odor pollution problem in caustic sludge neutralization process. All the pretreated caustic sludge can be treated in the sewage treatment field, but the oxidized tail gas has a small amount of odor and VOCs emissions, and its investment and operating cost is higher. Caustic sludge neutralization-acidification sulfur recovery and gas water purification technology is depended on the existing sewage treatment field in the factory, MDEA hydrogen sulfide recovery system, and VOCs exhaust gas treatment device. Through the newly established caustic sludge neutralization-acidification and nitrogen blowing reaction precipitator and blowing off hydrogen sulfide absorption tower, several goals can be achieved with relatively lower investment and operating cost, such as treated neutralized wastewater to meet discharge standards, hydrogen sulfide and VOCs recovery, high level purification of exhaust gas to meet the standard emissions.

Key words: refinery, caustic sludge, neutralization, acidification, odor, sulfur recovery, biochemical, desalination