Study On Treatment Of Oil-Based Cuttings By Demulsification Separation-Modified Fenton Oxidation Process

A large amount of oil-based drill cuttings are generated during the drilling of shale gas resources,which is clearly defined as a dangerous solid waste by the state.If it is not treated,direct discharge will cause great harm to the natural environment.Most of the technical methods for processing oil-based drill cuttings in current engineering applications have the disadvantages of high cost,low efficiency,and complicated equipment operation.The modified Fenton method is widely used in the application of sewage treatment and soil remediation,and has the advantages of good treatment effect,low operation requirement and low cost.The modified Fenton process for oil-based cuttings has not been reported yet.In this paper,the chemical demulsificationcentrifugal separation method and the modified Fenton oxidation method are combined to treat petroleum-based materials in oil-based cuttings.The removal rate of petroleumbased materials in oil-based cuttings is used to study the chemical breakthrough.Milkcentrifugal separation treatment of oil-based cuttings with two different pollution levels(ie,oil content of 48423.89mg/kg and 93800.23mg/kg,respectively),and the optimal process parameters were obtained through optimization.The modified Fenton reagent was prepared to investigate the effects of modified Fenton oxidation system on the oxidation removal of petroleum-based materials in oil-based drill cuttings.The optimal process parameters were optimized and the optimization experiments under the system were carried out.The reaction mechanism and reaction kinetics of oil-based drill cuttings were studied.The morphological morphology of oil-based cuttings samples before and after treatment was analyzed by SEM,XRD,TG-MS,FTIR and GC-MS.Characterization changes and the variation of the composition content of petroleum substances were explored.The following conclusions were obtained:(1)Demulsification separation-the best conditions for the treatment of oil-based cuttings by modified Fenton oxidation method: the best demulsifier is selected as BASF-L62.For 10 g oil-based cuttings samples,the optimal conditions for demulsification separation are The demulsifier dosage is 200 mg/L,the demulsification temperature is 65 °C,the demulsification time is 2 h,the centrifugal speed is 7000 r/min,the centrifugation time is 10 min;the optimum condition for modified Fenton oxidation is 30%.The dosage of hydrogen peroxide was 6 mL,the dosage of citric acid-ferrous sulfate catalyst was 5.8 mmol/L,the initial pH of the reaction was 6,and the reaction temperature was 65 °C.Under the optimal comprehensive conditions,the degree of light pollution of oil-based drill cuttings and medium-to-severe pollution degree oilbased cuttings in oil-based cuttings were 90.03% and 85.09%,respectively.(2)The optimization experiment of modified Fenton oxidation treatment of oilbased drill cuttings was studied: the oil-based cuttings with mild pollution degree were obtained by adding the catalyst and hydrogen peroxide once.Obtaining the best oil removal rate of 64.32%;for oil-based drill cuttings with moderate to severe pollution levels,when the dosing method is twice when the catalyst and hydrogen peroxide are added,and the dosing interval is 6 h,The best petroleum removal rate was 55.96%.(3)A preliminary study on the mechanism of oil removal: SEM and XRD showed that the crystal phase of oil-based drill cuttings before and after treatment was found to be a large change,still mainly quartz,barite,calcium carbonate and so on.The reaction kinetics fitting results show that the modified Fenton oxidation process for petroleumbased drill cuttings is more in line with quasi-secondary reaction kinetics.Through thermogravimetric analysis,it was found that the weight loss rate of the oil-based drill cuttings after treatment was greatly reduced compared with that before treatment.The residual weight of the samples after treatment at the final temperature was much larger than that before treatment.The residual weight indicates that the removal effect of petroleum-based substances in the oil-based drill cuttings is significantly improved.After treatment,the proportion of linear hydrocarbons in petroleum materials increases,the proportion of branched hydrocarbons,naphthenes and aromatic hydrocarbons decreases,and the carbonyl group and other substances decrease,which is more conducive to the advanced treatment of subsequent microorganisms.