RU2500490C1 - Method of cleaning solid surfaces of oil contaminants - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to removal of oil contaminants and can be used for cleaning of solid surfaces including soils and complex-geometry structures. Proposed method comprises spray washing of solid surfaces in detergent flow and phase separation of fouled detergent. Said detergent represents a 1-15%-water dispersion of monodisperse solid particles composed of polystyrene microspheres or mineral particles. Size of said solid particles varies from 0.2 to 6.0 mcm while the surface is modified by organosilicon surfactant. Solid particles film maximum 2D pressure makes 12-18 mN/m. Phase separation of fluid detergent is performed by addition of electrolyte aqueous solution.

EFFECT: simplified non-polluting process.

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Description

The invention relates to the cleaning of oil pollution and can be used to clean any hard surfaces, including soil and objects with complex surface geometry.

Known methods for cleaning solid surfaces, in particular soil, from oil pollution by the pyrolysis method (RU 2319074 C2), in the mechanical flotation mode in an inhomogeneous magnetic field (RU 2232654 C1), biological treatment methods (DE 4337192 A1, RU 2398640 C1) using sorbents ( WO 9850178 A1). However, none of these methods can achieve a high degree of purification.

There is also a method of cleaning the soil from oil pollution, including mixing the soil with water, mixing the mixture when heated and separating oil and gas pollution together with water vapor, followed by soil treatment with a peroxide compound (WO 9904914 A3). The specified method also does not allow to achieve a high degree of soil purification.

The closest in technical essence and the achieved result is a known method of cleaning solid surfaces from oil contamination, including jet washing of solid surfaces in a stream of washing liquid and the subsequent phase separation of the contaminated washing liquid (RU 2244685 C1 - prototype).

According to the prototype method, the washing process is carried out in several stages. At the first stage, the soil is washed in the hopper with a stream of hot washing liquid. A 0.3-3.0% aqueous solution of a detergent forming an unstable emulsion with hydrocarbon impurities is used as a washing liquid, for example, detergents containing nonionic surfactants with additives. At the second stage, jet washing is carried out on an inclined screw conveyor when moving soil from the hopper to the vibrating screen through an integrated washing unit. The third stage of jet washing the soil is carried out on a vibrating screen with simultaneous separation of the soil from the contaminated solution. Contaminated washing liquid is dynamically regenerated by gravity sludge with constant heating using steam registers installed in a settling tank. The aqueous solution from the settling tank is pumped into the auxiliary pit, the sediment is discharged using a screw conveyor, the accumulated oil is pumped out using a vacuum pump, sent for further processing or used as fuel. In the pit, the residual concentration of detergent is precipitated by the flocculant.

The use of an aqueous solution of a detergent forming an unstable emulsion as a washing liquid provides rapid phase separation with a low residual concentration of carbon compounds in the aqueous phase. However, this same property of the washing liquid requires high intensity mixing of the mixture at all stages of washing in order to prevent premature destruction of the emulsion. The disadvantage of the prototype method is its multi-stage and the presence of polluting waste in the form of waste detergent deposited by the flocculant.

The technical task of the invention is to create a method of cleaning solid surfaces from oil pollution, devoid of these disadvantages.

The technical result of the invention is to simplify the technology and improve the environmental friendliness of the process.

The specified technical result is achieved by the fact that in the method of cleaning solid surfaces from oil pollution, including jet washing of solid surfaces in a stream of washing liquid and subsequent phase separation of the contaminated washing liquid, 1-15% aqueous dispersion of monodisperse solid particles is used as the washing liquid, are polystyrene microspheres or mineral particles and having a size selected from the range of 0.2-6.0 microns, a surface modified with an organosilicon surfactant m substance, and the maximum pressure of the two-dimensional 2D films formed from them, from 12 to 18 mN / m, the phase separation of the contaminated washing liquid is carried out by adding an aqueous electrolyte solution.

The basis of the proposed method is to obtain a stable emulsion of oil during mechanical (jet) processing of soil, objects with complex surface geometry, an aqueous dispersion of solid particles. Based on the results of the experiments, diagrams of the stability of emulsions were constructed depending on the solids content, based on which it was found that the solids content in the aqueous dispersion should be from 1 to 15%. The solid particles used in the proposed method have an optimal combination of hydrophilic and hydrophobic properties, which were studied by the Langmuir method (see, for example, Blinov L.M. Langmuir films. J. Uspekhi Fizicheskikh Nauk, 1988, vol. 155, issue 3, p. 443-480). As it was found experimentally, the indicated optimal combination of the hydrophilic and hydrophobic properties of solid particles is achieved with a maximum two-dimensional pressure of the 2D films formed from them from 12 to 18 mN / m, which is the result of using particles of the aforementioned size with a narrow particle size distribution (monodisperse particles ), as well as by modifying the surface of the particles with organosilicon surfactants. Monodispersity of particles provides a minimum number of defects in the protective film formed from them on the surface of oil droplets.

As organosilicon surfactants for modifying the surface of solid particles, for example, industrially produced surfactants such as α, ω-bis [hydroxy-9-ethoxypropyl] polydimethylsiloxane, a mixture of a polyoxyalkyleneorganosiloxane block copolymer with α, ω-bis can be used [10-carboxydecyl] polydimethylsiloxane, etc.

Modification of the surface of mineral particles can be carried out, for example, by the method of applying from a solution or by any other known method. Particles of aluminum or silicon oxides, montmorillonite, zeolite, etc. can be used as initial particles. A fraction with an appropriate size is isolated by the method of separation of dispersed particles on sieves (in the geometric parameters of anisometric particles, width, height, thickness, at least two of these parameters have values in the corresponding range).

Polystyrene microspheres of a given size are prepared by seed polymerization. For particles of this group, the necessary surface properties are achieved by the introduction of surfactants at the synthesis stage according to known methods (see, for example, Gritskova I.A., Kopylov V.M., Simakova G.A., Gusev S.A., Markuse I.Yu., Levshenko E.N. Polymerization of styrene in the presence of surface-active organosilicon substances of various nature J. High-molecular compounds, 2010, vol. 52, No. 9, p. 1689-1695). The amount of surfactant, both in the case of mineral particles and in the case of polystyrene microspheres, is determined by the predetermined above value of the maximum two-dimensional pressure of the 2D films formed from them. Polystyrene microspheres can be further modified at the synthesis stage by the addition of a comonomer, for example, methyl methacrylic acid, which allows to obtain an additional technical result, which consists in the possibility of preparing a washing liquid based on sea water without its preliminary preparation. When using all other particles, the washing liquid is prepared only on the basis of fresh water from local sources also without its preliminary preparation.

Phase separation of contaminated washing liquid is carried out by adding an electrolyte solution, for example, sodium chloride in the form of an aqueous solution of 3-5% concentration, calcium chloride in the form of an aqueous solution of 0.1-2.0% concentration and other available electrolytes. The amount of added electrolyte depends on the volume of the tank, however, in any case, for the successful phase separation of contaminated washing liquid, the addition of electrolyte in an amount exceeding 5 wt.% Is not required.

According to the proposed method, the degree of removal of oil pollution without heating the washing liquid is about 98%. With increasing temperature of the washing liquid and the pressure of its stream, the degree of purification can be increased by at least 1%.

The implementation of the proposed method for cleaning solid surfaces from oil pollution is as follows.

An aqueous dispersion of solid particles is prepared with a solids content of 1-15%, selected depending on the degree of contamination of the cleaned object. The resulting dispersion under a pressure of 1.5-6 atm in the form of a jet obtained, for example, using a minimo wash, is directed to a contaminated object. If the object is a solid body with complex surface geometry, then when a jet strikes its surface, the contaminant film disperses. Solid particles make it possible to emulsify a hydrocarbon film at a temperature of 10 to 70 ° C and, due to the optimal combination of hydrophilic and hydrophobic properties, provide high stability of the emulsion obtained. For objects having a dispersed form (soil), in a collision with a stream of an aqueous dispersion of solid particles, not only emulsification of the film polluting the soil particles occurs, but also its mixing. The depth of mixing of the soil depends on its density and pressure of the jet, and the contaminating film is emulsified in the entire mixed volume. The resulting emulsion substitutes an easily mobile phase, which can be transferred to a container where an aqueous solution of electrolyte is added. The addition of electrolyte causes the destruction of the emulsion, while oil products with solid particles float. The resulting hydrocarbon layer is separated and sent for processing.

Example 1. A sample of 100.00 g of soil was contaminated with 10.00 g of oil. As a washing liquid, a 5% aqueous dispersion of polystyrene microspheres was used, 90% of which are 0.20 ± 0.05 μm in size. The microspheres have a modified surface and a maximum two-dimensional pressure of 2D films of 16 ± 1 mN / m. Soil cleaning is carried out according to the above scheme with a flow rate of washing liquid 200 ml and a spray pressure of 1.5 atm. When using detergent without heating, 9.82 g (98.2%) of oil was removed.

Example 2

The soil was cleaned from oil pollution by an aqueous dispersion of montmorillonite particles (sodium), a fraction of 2 μm (highlighted on metal-cloth sieves - GOST 6613-86) with a modified surface having a maximum two-dimensional pressure of 2D films of 15 ± 1 mN / m. When using detergent without heating, 9.80 g (98.0%) of oil was removed.

Example 3

Purification of the soil from oil pollution was carried out according to example 1, but when using water as a washing liquid. When using a washing liquid (water) without heating, 0.60 g (6%) of oil was removed.

Claims (1)

A method of cleaning solid surfaces from oil contamination, including jet washing of solid surfaces in a washing liquid stream and subsequent phase separation of the contaminated washing liquid, characterized in that 1-15% aqueous dispersion of monodisperse solid particles representing polystyrene microspheres or mineral particles having a size selected from the range of 0.2-6.0 μm, a surface modified with an organosilicon surfactant, and a maximum of two The pressure of the 2D films formed from them is from 12 to 18 mN / m, and the phase separation of the contaminated washing liquid is carried out by adding an aqueous electrolyte solution.