Research On Pretreatment Technology Of The Delayed Coking Sulphureous Sewage From Heavy Oil Refining

The delayed coking sulphureous wastewater(DCSW) is a very difficult stripping process to treat with characteristics of high concentration of coke powder, oil, sulfide, ammonia nitrogen, phenol and other multi-composition of pollutants, and high emulsification.Therefore, in order to keeping stable operation, it is inevitably develop a new efficient,reliable, economic, and environmental technology to preprocess the DCSW.Based on a widely literature search of delayed coking sour water pretreatment methods,this study was to solve the following problems:1) Chemical demulsification methods was firstly applied for sour water treatment to removal oil and coke powder pollutants. 2) The pretreatment technology of hydrocyclone separation and ceramic membrane separation were used to further remove those pollutants. For hydrocyclone separation, the influences of split ratio on removal rate of petroleum and coke powder were determined. For ceramic membrane separation, the effects of different influent quality on membrane permeability, removal rate of petroleum as well as coke powder were studied. 3) Furthermore, the coupling technology of hydrocyclone and ceramic membrane was applied to DCSW, and the effects of overflow ratio of secondary hydrocyclone on pretreatment systems were also studied.The results showed that: the pretreatment technology of DCSW was “demulsification and settlement→one stage hydrocyclone→ceramic membrane→twe stage hydrocyclone”. 1)the best conditions of demulsification was to use SYDX-2 reagents with the addition amount of 80 mg/L and settlement time of 3 to 5 h, the oil removal rate was up to 85%. 2) Under overflow rate of 2% ~ 3% in first stage of hydrocyclone unit, the removal rete of oil and coke powder was 30% and 40%, respectively. 3) the optimal conditions of ceramic membrane unit was as follows: controlling of oil in influent quality from ceramic membrane unit blow 100mg/L, keeping coke powder less than 300 mg/L and the membrane flux stability 140 L/m2.h,the oil and coke powder removal rate were 95% and 99%, respectively.4) the oil content and coke powder of pilot plant effluent was less than 20 mg/L and 0.5 mg/L, which was not only meet the standard requirement, but also superior than the standard.