| Acidizing technology is a technical measure that uses acidic liquid to react with minerals in near wells or reservoirs to increase permeability,increase oil or gas well production and injection volume.After the acidification construction is completed,the residual acid will be discharged to the ground forming acidified waste.The acidified waste liquid has a low pH and complex composition,and it is of great significance to protect the environment by re-injecting the reservoir or discharging it after treatment.At present,acidification waste liquid treatment technologies include neutralization and chemical oxidation.It is the key to utilize the high concentration of Fe(Ⅱ)in acidified waste liquid and convert it into flocculated components.Based on the analysis of the main pollutant components of the acidified waste liquid,the research work has formed treatment process of the neutralization-oxidation-flocculation through the pH adjustment,suspension and Fe(Ⅱ)conversion and removal process and investigation of kinetics.Treatment technology provides a theoretical basis for the reinjection treatment of acidified waste liquids.The main conclusions are as follows:(1)The water quality analysis of three kinds of acidified waste liquids in an oil field in Yan’an area show that the pH of the waste liquid is below 5.0;the total iron concentration is 140-400mg/L,the average corrosion rate is 0.016-0.311mm/a,and the low oil content is 2.2-10.4mg/L.(2)Using the "neutralization-oxidation-flocculation" composite process,adjust the pH of the sewage to 7.5,when the amount of H2O2 is 0.05%-0.4%(V),and the optimal concentration of PAM is 3-5 mg·L-1‘,The content of suspended matter and total iron in the waste liquid after treatment can be reduced to 30 and 0.2 mg/L,respectively.(3)The kinetic parameters of Fe(Ⅱ)oxidation reaction were obtained through the combination of Luminol chemiluminescence signal detector and flow injection.Under 293K,the reaction of H2O2 with Fe(II)is a first-order reaction,and the reaction rate constants for Fe(Ⅱ)concentrations of 50,100,and 150 mg/L are 0.12612 ×103,0.41686 ×103,and 1.18230 ×1103 s-1.(4)When the molar ratio of NaOH to total iron ∑ Fe is R≤5.56 in the reaction system,the main composition of the precipitate is α-FeOOH.After the γ-FeOOH phase appears,as the amount of NaOH increases,the removal effect of simulated kaolin suspension is more obvious;the ferromagnetic Fe3O4 is generated when the molar ratio of the reaction system is R≥6.11,which is more obvious for the removal of turbidity and color.The turbidity of the acidified simulated solution is 61.8 NTU,which was reduced to 17.8,3.28,and 2.32 NTU after treatment,at 20,50 and 80℃ respectively.At 20℃C,with the increase of NaOH dosage,the residual turbidity decreased from 61.8 NTU to 11.54 NTU;at 50 and 80℃,the effect of NaOH dosage on residual turbidity was smaller than that at 20℃. |
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