Study of the Efficiency of Combined Titanium Coagulants in the Treatment of Formation Waters
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y of the Efficiency of Combined Titanium Coagulants in the Treatment of Formation Waters S. V. Azopkova,*, E. N. Kuzina, and N. E. Kruchininaa a Mendeleev
Russian University of Chemical Technology, Moscow, 125047 Russia *e-mail: [email protected]
Received February 5, 2020; revised September 17, 2020; accepted September 17, 2020
Abstract―The pretreatment of model and real formation waters before the subsequent desalination was investigated. Produced water associated with the oil production process was used as a real formation water. The real and model formation waters were characterized by high salt (up to 30 g/L) and oil contents (up to 50 mg/L) and a pH range of 7.6–7.8. Treatment was carried out using aqueous solutions of aluminum sulfate (Al2(SO4)3) and titanium tetrachloride (TiCl4), thiosulfate (TiOSO4), and trichloride (TiCl3), as well as their combinations. The efficiency of treatment with different coagulant samples was evaluated, and the effective doses of reagents were selected. The feasibility of electrocoagulation on aluminum and titanium electrodes for the pretreatment of formation water was explored. The efficiency of removal of oil products and suspended solids with titanium tetrachloride solutions was 95% and with the aluminum–titanium coagulant, 90%. The efficiency of removal of oil products by the electrocoagulation on both titanium and aluminum electrodes was not higher than 76%. The effect of doping of titanium-containing precursors to a classical coagulant (aluminum sulfate) on such parameters as the efficiency of removal of oil products, suspended solids, and color, as well as the rate of filtration of coagulation sludge. The effective ratios of aluminum sulfate and titanium additives were determined, which allow the filtration rate and the efficiency of pretreatment of formation to be increased with only slight increase of the cost of the combined reagent. Keywords: titanium coagulant, water treatment, titanium tetrachloride, electrocoagulation
DOI: 10.1134/S1070363220090364 INTRODUCTION The demand for various types of energy is increasing from year to year, and this in turn leads to an increase in the production capacity of oil refineries and in the number of oil wells. The oil production process is accompanied by water flooding of oil-bearing formations and, as a consequence, generation of large volumes of highly mineralized formation water. The extraction of 1 ton of oil generates up to 5 tons of polluted waters [1]. Formation water has a complicated chemical compositions and is characterized by high salinity (up to 30 g/L), high temperature (70–80°C), and contains such components as: – petroleum products and naphthenic acids and their salts; – condensation and residual capillary (pore-capillary) moisture; – drilling mud filtrate;
– various solutions used in the process of repair, well operation (corrosion inhibitors, acids, and other reagents); – dissolved gases. The presence of toxic components in formation water makes it impossible to purify to meet the standards for water disch
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