RU2132757C1 - Method of removing hydrocarbons from soil - Google Patents

Abstract

FIELD: oil pollution removal. SUBSTANCE: central and peripheral electrodes are plunged into soil at area to be cleaned and voltage gradient between electrodes is created. Then, nonpolluting liquid carrier is fed into the surface region around central electrode, which carrier moves under electroosmosis effect from central electrode toward peripheral electrodes and displaces hydrocarbons in soil that are removed from peripheral electrodes. As liquid carrier, water with pH 9 prepared by cavitation effect or water with pH 5,5 prepared by heating is utilized. Utilization of water taken from bed in oil and gas deposit development is possible. EFFECT: enhanced cleaning efficiency due to accelerated movement of liquid carrier and reduced voltage gradient on electrodes. 2 cl, 3 dwg

Description

 The invention relates to methods for cleaning the soil of hydrocarbons (oil, gas condensate, engine oil, gasoline, etc.).

 A known method of cleaning sand from petroleum products (as USSR AS N 1629102, MKI 5: 03 V 5/00, 01 01 33/12, publ. 02.23.91, Bull N 7-analogue), including sand processing an aqueous solution of hydrofluoric acid with a concentration of 0.5 - 2.0 wt.% with the ratio of the mass of solid soil to liquid reagent as 1: (2-6) for 30 minutes

 The main disadvantage of this method is the treatment of sand with a chemical reagent, to neutralize which it is necessary to add additional reagents and remove the reaction products of these reagents, which entails additional economic costs and does not increase the ecology of the cleaned sandy soil.

 Closest to the technical nature of the present invention is a method of removing contaminated soil (US patent N 54157744 A, MKI 6: 01 D 61/56, publ, ISM, issue 001, N 10, 1996, S. 34 - prototype ), including immersion in the soil on the cleaned area of the central and peripheral electrodes, creating a voltage gradient between them, feeding into the zone adjacent to the central, non-polluting carrier fluid, moving the carrier fluid under the action of the electroosmotic effect between the electrodes, displacing the contaminated carrier fluidmaterial from the soil to the peripheral electrodes and removal of contaminated material from the latter.

 This method is more environmentally friendly than the analogue. However, the movement of pure carrier fluids such as water under the action of the electroosmotic effect is not intense, and it slows down even more when contaminants such as viscous hydrocarbons such as oil, engine oil and the like are displaced from the soil by the carrier fluid. Particularly great resistance to the movement of the carrier fluid with hydrocarbons occurs in the cold season, when the viscosity of the latter increases. Therefore, to ensure the movement of the carrier fluid and viscous hydrocarbons, it is necessary to maintain a high voltage gradient of about 380-500 V, depending on the soil structure, which leads to high energy consumption and makes this method ineffective.

 The purpose of the invention is to increase the efficiency of soil cleaning from hydrocarbons by accelerating the movement of the carrier fluid and reducing the voltage gradient at the electrodes.

 This goal is achieved by the fact that in the method of cleaning the soil of hydrocarbons, including immersion in the soil on the cleaned area of the central and peripheral electrodes, creating a voltage gradient between the first and second, supplying to the area adjacent to the central electrode, not polluting the carrier fluid, moving the liquid -carrier under the action of the electroosmotic effect from the central electrode to the peripheral, displacement of hydrocarbons from the soil by the carrier fluid and their removal from the peripheral electrodes, as Carrier liquids use water in which the pH is changed to 9, acting on it by cavitation, or up to 5.5 by heating.

 The use of water as a carrier fluid, in which the pH is changed to 9, acting on it by cavitation, or to 5.5 by heating, it has improved the efficiency of soil cleaning at any temperature without the use of chemicals and their neutralization.

 The applicant is not aware of soil cleaning methods in which water is used as a carrier fluid, in which the pH is changed to 9 by exposure to it by cavitation, or by 5.5 by heating.

 In FIG. Figure 1 shows a graph of the pH of distilled and fresh water versus the duration of cavitation.

 In FIG. 2 shows a graph of the pH of water versus its temperature.

 In FIG. 3 shows the technological scheme of the installation for implementing the method of cleaning the soil from hydrocarbons.

 The proposed method of cleaning the soil from hydrocarbons is as follows.

Due to the action of cavitation, water molecules dissociate into H ⁺ and OH ^- ions. H ⁺ ions partially leave the liquid phase and the ions OH ^- are accumulated in the latter, increasing water pH. In FIG. 1 shows a graph of the pH of distilled water and fresh water taken from various sources 2 and 3, depending on the duration of cavitation. Water with high pH has a high surface activity and has high detergent properties.

Such water in contact with hydrocarbons
- destroys the viscous surface film of hydrocarbons and intensively leaches them from the soil;
- increases the dynamics of mixing leachable hydrocarbons with itself and forms an emulsion, which has a small hydraulic and low electrical resistance.

 These properties increase under the action of the electroosmotic effect the mobility in the soil of the formed liquid system (emulsion), which, ultimately, leads to a decrease in voltage between the electrodes to 60 V and energy consumption and, as a result, to an increase in the efficiency of the method for cleaning the soil from hydrocarbons.

 When water is heated, its pH decreases and, therefore, its conductivity increases. In FIG. 2 shows a graph of the pH of water versus its temperature. With decreasing pH of the water, the solubility of hydrocarbons in it increases.

Such water in contact with hydrocarbons
- reduces their surface tension and viscosity;
- forms a mobile electrically conductive emulsion.

 These properties intensify the joint movement of water with hydrocarbons in the soil under the action of the electroosmotic effect from the central electrode to the peripheral one, which, as a result, leads to a decrease in voltage between the electrodes to 60 V and a decrease in energy costs and increases the efficiency of the method of cleaning the soil from hydrocarbons.

 The proposed method for cleaning the soil from hydrocarbons in its intensity is similar to methods for cleaning the soil using chemicals such as surfactants with a pH of 9 and acids of pH 5.5.

 However, this method is environmentally friendly, does not require additional costs for chemicals and their neutralization.

 Compared with the prototype, this method is 6-7 times more efficient than the prototype in terms of energy consumption.

 The method can be implemented using the setup shown in FIG. 3. The installation consists of central 2 and peripheral 3 electrodes immersed in soil on the cleaned area 1, nozzles 4 for supplying water, pump 5, which serves to remove water with hydrocarbons from peripheral electrodes, separator 6, which serves to separate water and hydrocarbons, capacity 7 with a Venturi nozzle 8 and a heater 9, a pump 10 for pumping water into the nozzles 4 and a Venturi nozzle 8. The separator 6 and the tank 7 are connected by a water pipe to the check valve 11. The tank 7 is additionally connected to the nozzle 4 by a high-pressure supply pipe 12 water with a pH of 5.5.

An example of the method. Water with a temperature of 17 ^o C, having a pH of 7.4, is fed by a pump 10 from a tank 7 to a Venturi nozzle 8 at a speed of 30 m / s. The pressure of the water flowing through the diffuser of the Venturi nozzle 8 is reduced to a value of 2 • 10 ³ Pa. In this case, cavitation of water occurs. The cavitated liquid enters again into the container 7. Water is treated in such a way by cavitation for 520 seconds, after which the water in the tank has a pH of 9. The surface-active water obtained by pump 10 is fed through the nozzle 4 to the area adjacent to the central electrode 2. Between the central and peripheral electrodes create a voltage gradient of 60 V. Surface-active water with a pH of 9 under the influence of the electroosmotic effect moves from the central electrode 2 to the peripheral 3. At the same time, it contacts the hydrocarbons, knowing the soil, destroys their surface film and intensively leaches them from the soil. Surface-active water with a pH of 9 with hydrocarbons forms an emulsion, which enters the peripheral electrodes 3, from where it is removed by a pump 5 and fed to the separator 6. In the separator 6, the emulsion is separated into water located at the bottom and hydrocarbons located at the top of the separator 6. Separated water enters the tank 7 through the check valve 11. The separated hydrocarbons are sent to the storage tanks.

The described cycle is repeated until complete removal of hydrocarbons from the soil. The process of cleaning the soil with surface-active water obtained using cavitation is energetically beneficial at soil temperatures above 0 ^o C.

In the case of cleaning the soil with a temperature below 0 ^o C from hydrocarbons in this way, water with a pH of 5.5 is used, which is obtained by heating to 240 ^o C in the tank 7 using the heater 9. When the water in the tank 7 is heated, the pressure rises to 3.5 MPa Under this pressure, water with a pH of 5.5 is supplied, bypassing the pump 10, through a pipe 12 through the nozzle 4 to the treated area 1. The further process of cleaning the soil from hydrocarbons is carried out similarly to the process described above.

Claims (2)

 1. A method of cleaning the soil of hydrocarbons, including immersing in the soil on the cleaned area of the central and peripheral electrodes, creating a voltage gradient between the central and peripheral electrodes, applying to the region adjacent to the central electrode not polluting the carrier fluid, moving the carrier fluid under the action the electroosmotic effect from the central electrode to the peripheral, displacement from the soil by a carrier liquid of hydrocarbons and their removal from the peripheral electrodes, characterized in that in honors the carrier liquid is water with a pH of 9, the resultant cavitation influence on it, or water with a pH of 5.5 obtained by heating it.  2. The method according to claim 1, characterized in that use the water extracted from the reservoir during the development of oil and gas fields.

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