Research On Caustic Washing Desulfurization From Oil Production And Harmless Treatment Of Sulfur Wastewater

In this paper, the caustic washing was used to conduct desulfurization from high-sulfurdiesel in order to alleviate increasingly serious energy and environmental problems of today’ssociety, and the harmless treatment of sulfur wastewater produced from this process was alsostudied. As well, the form of sulfur in oil, the characteristics and hazards of sulfur wastewater,desulfurization technology of domestic and overseas and the development process of thesulfur wastewater treatment technology were introduced and described, and the mechanism ofoil acid and alkali refining process, coagulation precipitation method and advanced oxidationprocesses were elaborated. The results of the experiment were analyzed and discussed at last.In the caustic washing desulfurization experiment, as sulfur removal an indicator, thetreatment effect influenced by the types of alkali, dosing concentration, temperature, stirringspeed and time were investigated. The results showed that the above factors all have varyingdegrees impact on the treatment effect. The best combination of factors is that thedesulfurization alkaline agent was NaOH, the temperature was controlled between20℃and30℃and the dosing concentration(the ratio of sodium hydroxide quality and diesel quality)of sodium hydroxide was14%. After processing, the sulfur content of diesel was260.56mg/ml and the removal rate was79.76%.The process of caustic washing desulfurization from diesel would produce a largeamount of sulfur wastewater. In this research, the coagulation precipitation method was usedfirst to pretreat this sulfur wastewater to reduce the concentration of pollutants in wastewater,and then the advanced oxidation was used for the advanced treatment. In the coagulationexperiment, as removal rate of S2-, COD removal rate, flocculation cake quality, flocculationcondition and water color the indicators, the coagulation effect influenced by coagulant, typesand dosing amount of flocculants, pH, temperature and the way of stirring were investigated,and the floc morphology was analyzed by scanning electron microscope; In the followingadvanced oxidation experiment, as removal rate of S2-, COD removal rate the indicators, theoxidation treatment effect influenced by types and dosing amount of oxidant, dosing method,pH and reaction time were investigated, and the effect on the residual ratio of persulfate byvarious factors was also investigated.The best treatment and operating conditions of each treatment unit were confirmed byexperiments:(1) Coagulation treatment: the pH was adjusted to7-8at the temperature of25℃, the dosing amount of PFS was4000mg/L and polyacrylamide was25mg/L, the rapid stirring was conducted first with the speed of200r/min and time of2min,and then the slowstirring started with the speed of80r/min and time of10min, at last, the reactor was made tokeep standing;(2) Advanced oxidation: the pH was adjusted to7, and the dosing amount ofammonium persulfate was60mg/L, the solution was dosed to the reactor equably andrepetitiously, and the reaction time was25min. The regularity of persulfate residual rateinfluenced by various factors was consistent with the regularity of oxidation treatment effectinfluenced by this factor.Sulfur wastewater treated by coagulation-advanced oxidation technology can get goodresults, COD was97.93mg/L and the removal rate was94.59%; the sulfur content was0.38mg/ml and the removal rate was99.91%. Effluent water was colorless, clear and all theindicators reached the national emission standards for direct emissions.