The Study On The Treatment Of Acidizing And Fracturing Wastewater By Process Integration With Microelectrolysis

Fracturing and acidification were adopted popularly by oilfields in order to enhance oil recovery. The fracturing and acidizing wastewater had dull color, high COD value, high acidity, high viscosity, refractory and etc which was produced in the process of fracturing and acidizing operation. If the wastewater was discharged without being treated, the environment would be seriously polluted.This thesis proposed the process integration of"ammoniumpersulfate oxidation– microelectrolysis–Fenton oxidation-defluorination"to treat the fracturing wastewater based on its component, characteristic and according to the mechanism of ammoniumpersulfate oxidation, microelectrolys and Fenton oxidation. The conditions for process were determined on the removal rate of CODCr.The job were done in sequence. Firstly, in order to treat the fracturing and acidizing wastewater, the simulate wastewater of HPG (CODCr:752mg/L,pH = 3.0,CF- = 114.3mg/L) was treated by"microelectrolysis-Fenton oxidation", and the results were: (1) The removal rate of CODCr was 26.3% in the process of microelectrolysis with the process conditions were: m(Fe)/m(C)=5:1, t=90min,pH=2.5. (2) Under the conditions of t=75min, c[10%H2O2(v/v)]= 7.5mL/L, pH=4.0, the total removal rate of CODCr was 38.3%. (3) Using Ca(OH)2 as precipitant, the concentration of fluorion was 8.5mg/L when the concentration of precipitant was 20g/L.secondly, the fracturing wastewater (initial CODCr:11007mg/L) was treated by the process integration, and the results as follows: (1) The removal rate of CODCr was 22% in the process of oxidation by ammoniumpersulfate under the condition of the reaction time was 30min, c[5%(NH4)2S2O8 (m/m)]=25.0mL/L, pH=3.0. (2) After oxidation operation, the fracturing wastewater was treated by microelectrolysis with the conditions of t=120min, m(Fe)/m(C)= 5:1, and the removal rate of CODCr was about 35.8%. In order to improve the ratio of CODCr removal, copper was electroplated on the surface of iron particles, under the optimum conditions of t=120min, m[Fe(Cu)]/m(C)=6:1, the times was 2, the removal rate of CODCr could reach to 58.7%. The results showed that the removal rate of CODCr was increased by about 20% compared with microeleclysis above. (3) The fracturing wastewater was given to the Fenton reagent oxidation after the reaction of catalytic copper microelectrolysis. The conditions of the advanced oxidation were that: c[10%H2O2(v/v)]=7.5mL/L, pH=4.0, t= 60min, and the removal rate of CODCr 22.6% was got. The total removal rate of CODCr could reach to 75.6% by the process integration (final CODCr:2750mg/L).The innovations of this thesis were that the fracturing wastewater treated by the"four-stages"process integration was implemented for the first time, then a convenient way of treating fracturing and acidizing wastewater was offered. And the mechanism of microelectro- lysis involved flocculation, adsorption, oxidation-reduction, and electro-enrichment which worked coordinately was testified initially.