A Study On Reduction And Reuse Technology Of High Salt Water In Soft Water Regeneration System For Heavy Oil Recovery

In the process of heavy oil production in Xinjiang Oilfield,coal-fired steam injection boiler and two-stage sodium ion softener will produce a large amount of high salt wastewater.In order to improve the ecological environment around Xinjiang,a research of high salt wastewater treatment technology has been carried out for the discharge of coal-fired steam boiler with large displacement and low hardness.However,the high salt water discharged from the regeneration process of the softener,which is very difficult to deal with,is still treated in the way of reinjection formation and discharge of artificial wetland and accident pool.With the increase of high salt water emissions and the increasingly strict requirements of the country on the environment,the original way can not meet the actual needs.Therefore,the technology of reducing and reusing high salt water in the regeneration process of softener is studied in this thesis.Through the analysis of the water quality in each stage of the regeneration process of the softener,the reasons for the large discharge of high salt water and the characteristics of the water quality containing a large number of hardness ions and salt solution were found.In order to solve the problem of high salt water emission,the regeneration process optimization of two-stage sodium ion softener was carried out.The optimized regeneration process was added into the emptying process,and the dynamic regeneration was transformed into static regeneration by using the salt solution immersion and small washing process instead of the replacement process.Therefore,the soaking salt concentration of SST-60 resin with different adsorptive capacity to achieve the best regeneration efficiency was studied under the condition of static regeneration in laboratory,and the results were applied in the field test.In order to achieve the purpose of recovering and utilizing the high salt water,combined with the characteristics of high salt water quality,the research on the improvement and reuse of high salt water was carried out.The hardness ions in wastewater were removed and missing sodium ions were replaced by adding Na₂CO₃ and NaOH mixture.In order to determine the optimum conditions for adding precipitant,indoor experiments were conducted to study the effect of reaction time,dosage and dosing method on the removal of hardness ions.Based on laboratory experiments,the feasibility of the scheme is verified by field test.The research on regeneration process optimization of two-stage sodium ion softener shows that the concentration of soaking salt solution is 14%,the regeneration cycle is increased from 3 times to 4 times per day after the optimized regeneration process,but the total amount of high salt water discharged is decreased,and the reduction ratio is 12.7%.The experimental study on the modification of high salt water shows that when the dosage of NaOH is 1.08 times that of the theoretical calculation and the dosage of Na₂CO₃ is 1.11 times the theoretical calculation,the removal rate of hardness is over 99%,and the ratio of the drug is the highest.It is verified by field test that high salt water is fully recycled,and the annual cost savings is about 50%.According to the comparison of the emission reduction of high salt water,it is decided to popularize the technology of improving and reusing high salt water on a large scale.First of all,the pilot test design is carried out for the No.5 heating station of heavy oil company.If the test is successful,it can be used for reference in the treatment of high salt water in Xinjiang area.