RU2200637C2 - Method of cleaning surfaces from hydrocarbon contamination - Google Patents

Abstract

FIELD: methods of cleaning surfaces from hydrocarbon contamination, such as oil, petroleum products, grease, fats, oils; mechanized washing of technological and transport facilities. SUBSTANCE: method includes preparation of washing compound containing 2-4 mas.% of nonionogenous surfactant on base of alkoxylate of fatty alcohol and active component containing only soda ash or partial replacement of it by sodium salts of phosphorous acid; used as nonionogenous surfactant is hydroxyethylated polyoxypropylene glycol derivatives of ethylenediamide or ethylenediamine; proposed method includes also washing the surface with aqueous solution of detergent, discharging emulsion thus obtained, separating the emulsion into aqueous and organic phases by passing it through self-cleaning thin- layer settler made in form of plane-parallel vertical coalescence plates forming slotted clearances followed by return of aqueous phase to cleaning cycle and periodic removal of organic phase to receiver. EFFECT: simplified procedure; increased extraction of hydrocarbon contaminants; improved service parameters. 3 cl, 1 dwg, 3 tbl

Description

 The invention relates to methods for cleaning the surface of hydrocarbon compounds, such as oil, oil products, lubricants, technical and household fats, oils, and can be used in various industries for chemical-mechanized washing and cleaning of technological and transporting agents.

 The process of processing (cleaning, washing, degreasing) of parts, assemblies, mechanisms and equipment, as well as tanks and containers contaminated with oil, oil products, fats and other liquid hydrocarbons, is one of the urgent problems from the standpoint of operational, environmental and fire safety, as well and in terms of huge financial costs.

 Known cleaning methods used previously could not meet modern requirements. The reason for this is the complexity and incomplete knowledge of the physicochemical processes that occur during cleaning of surfaces from liquid hydrocarbons, the results of which are influenced by a set of factors: surface material, composition and property of contaminants, parameters and modes of the cleaning process, composition of technical detergents, on which they depend its properties, especially the interaction of washing solutions with contaminants, etc.

 Known methods and compositions (Labomid, MS-61, ML-51, ML-80 and others), as well as various solvents for cleaning metal surfaces from oil-mud, oil and asphalt-resinous pollution, which are widely used in industry. As a rule, universal solvents are used that can dissolve various substances included in the contaminants, such as acetone, kerosene, white spirit, etc. (B.G. Petrik, P.V. Chulkov and S.I. Kalashnikov "Reference: Solvents and compositions for cleaning machines and mechanisms", M., "Chemistry", 1989). The main operations of these methods are washing the surface to be cleaned, pumping out the resulting emulsion of the solvent and liquid hydrocarbons, and removing it with a discharge to the treatment plant.

 The main disadvantages of using various types of washing liquid solvents are high fire hazard, environmental hazard both for the environment and for staff. Known solvents with a high flash point (trichloroethane, trichlorethylene, etc.), despite the fact that they reduce fire hazard, are extremely toxic and dangerous to the health of staff, therefore they require strict observance of safety measures.

 A known method of cleaning the surface of products from hydrocarbon contaminants, in particular from oil-fat contaminants (RF patent 2019318, 08 V 3/08, publ. 1994) using two liquids. Washing the surface of products according to this method is carried out with a washing solution and the washed impurities are removed from the washing solution with the aid of an auxiliary liquid that does not form a stable emulsion with the washing solution and is capable of selectively extracting oil-fat contaminants from it. After cleaning, the auxiliary liquid is regenerated, in particular by distillation, and returned to the cleaning cycle.

 The disadvantages of this method include the use of two liquids, which complicates the technological scheme, requires additional equipment and, accordingly, increases the cost of cleaning surfaces.

 A known method of cleaning the surface of oil products (ed. Certificate. 944685, 08 V 3/08, publ. 1982). In this method, the surface is cleaned with an aqueous solution of detergents based on surfactants and electrolytes, which forms a stable emulsion with hydrocarbon contaminants. To conduct surface cleaning in a closed cycle, the washing solution is regenerated by phase separation of the emulsion by electroflotation, after which the organic phase is removed, and the aqueous suspension is returned to the cleaning cycle.

 The specified method provides the required degree of surface cleaning and the possibility of reuse of the washing solution, however, due to the formation of a stable emulsion, which is caused by the shortcomings of the selected technical detergent, the process is complicated and requires a long time and cost of cleaning the resulting wash water.

 A known method of washing the tank and extracting residual liquid, which includes the suction and pumping of the residual liquid, the supply of the washing solution to the tank, separation of the oil-water mixture with the supply of inert gas to separate the oil component (RF patent 2099156, 08 V 9/08 Publ. 17.06 .93).

 The disadvantages of this method are the conduct of each of the operations on a separate vehicle and the use of hot water as a detergent, which cannot provide the proper degree of surface cleaning.

 Known methods for cleaning the surface from oil pollution using a coagulant and various depressants, which use additives containing polymers and a hydrocarbon solvent (RF patent 2109583, 08 V 9/08, publ. 27. 04. 98) or an aqueous suspension of hydrocarbons and salts of nitrogen, phosphorus and potassium (RF patent 2104103 B 09 C 1/10 Publ. BI 4-98), followed by rinsing the inner surface with hot water or treating with hot steam.

 The disadvantages of these methods include high temperature up to 95-100 C of the process and the complexity of the technological support for carrying it out. The lack of data on the composition of the detergent does not allow us to judge the quality of cleaning.

 Closest to the proposed method is a technical solution protected by RF patent 2135304 08 V 3/08, publ. 08.28.99 "Method for cleaning the surface of hydrocarbon contaminants." The essence of this method is that a surface contaminated with various hydrocarbon contaminants, such as oil, oil products, greases, fats and oils, is washed with an aqueous detergent solution capable of emulsifying hydrocarbon contaminants, the washing solution is regenerated by phase separation of the emulsion, followed by separation of the organic phase and returning the aqueous phase to the purification cycle. As a washing solution, forming an unstable emulsion with hydrocarbon contaminants, use the UBON detergent, protected by RF patent 210133 7, C 11 D 1/46, or the BOK detergent.

 The specified tool "UBON" has the following composition, wt.%: Sodium salt of polyacrylic acid, modified with ether groups - 0.1-10; electrolyte - 0.5-40; water up to 100.

 The composition of the detergent "SIDE" includes: non-inorganic surfactant in an amount of 0.2-14 wt. %; polyelectrolyte in an amount of 2.5-5.5 wt.%; active supplement rest. Acrylic acid polymers, for example, sodium carboxymethyl cellulose (Na-CMC), are used as a polyelectrolyte in the indicated agent, and sodium carbonate or sodium carbonate in combination with carbomide and / or sodium metasilicate are used as an active additive (RF patent 2132367, publ. BI 18 , 1999). As a nonionic surfactant in the specified detergent composition use neonol or syntanol.

 To prevent organic contaminants from entering the washing solution, the phase separation of the emulsion is carried out in a separation tank, and the aqueous phase returned to the cleaning cycle is passed through an intermediate tank. The selection of the aqueous phase is carried out from the lower part of the separation tank, and its supply to the cleaning cycle is carried out from the lower part of the intermediate tank. During phase separation, the emulsions provide a volume ratio of organic contaminants and washing solution of at least 1: 2.

 The specified method provides the required degree of surface cleaning and the possibility of reuse of the washing solution, however, the result is achieved due to the complexity of the process, because Separate stages are carried out in intermediate containers, and ensuring the volumetric ratio of contaminants to the washing solution requires an assessment of the amount of contaminants to be removed before starting the surface cleaning process. How to reliably perform such an assessment is a problem.

 In addition, the achievement of the required degree of purification when using detergent "UBON" having the composition described in the description of the invention raises some doubts. So it does not contain an active component, i.e. main detergent. This doubt is confirmed by the fact that in the description of the implementation of this method there are no examples of its application.

When using the BOK technical agent as a washing solution, it must be taken into account that neonol and syntanol are nonionic surfactants that cause large foaming, and when the washing solution is prepared at relatively low temperatures, they can decompose, losing their properties. The use of metasilicates in a washing solution is also undesirable, as when its content is more than 20%, SiO ₂ is released on the surface to be cleaned, which prevents cleaning.

 Polyelectrolytes are prone to the formation of polymer-colloidal complexes, which can cause a decrease in the extraction of organic compounds and the degree of purification of the washing solution, i.e. more frequent adjustments.

 The technical task of the invention is to simplify the process, increase the extraction of hydrocarbon contaminants during the regeneration of the washing solution and increase the technical and economic indicators of the process.

 The technical result is achieved due to the fact that in the known method of cleaning the surface of hydrocarbon contaminants in a closed cycle, including the preparation of an aqueous solution of detergent containing a nonionic surfactant and an active component, washing the surface with an aqueous solution of detergent, pumping the emulsion obtained, separation of the emulsion into water and organic phase, with the subsequent return of the aqueous phase to the purification cycle and periodic removal of the organic phase, some changes were made to the collection, which Rivedoux below.

 As a detergent, a detergent of the following composition is used, wt. %: nonionic surfactant based on fatty alcohol alkoxysilate 2-4 and the active substance the rest is up to 100%, moreover, soda ash or a composition with its partial replacement with sodium salts of phosphoric acid in a certain ratio of components is used as the active substance.

 The pumped-out emulsion (washing solution with hydrocarbon contaminants) is passed through a self-cleaning thin-layer sump, which can be installed in the same tank where the washing solution is located and it is regenerated or separately from this tank. Some differences in the design of the technological process do not affect the implementation of the proposed cleaning method.

Depending on the type of contaminants (oil, oil, fats, etc.) and the material of the surface being cleaned (steel, aluminum or other non-ferrous metal), a washing solution with a different content of detergent in it is used - from 1.5 to 4.0 wt. .%. Accordingly, the temperature of the washing solution is selected in the range of 40-55 ^o C.

 During the cleaning process, the concentration of the washing solution is controlled by the residual alkalinity of the washing solution, and, if necessary, periodically adjust it by adding fresh washing solution.

 A nonionic hydrophilic surfactant (nonionic surfactant) based on a fatty alcohol alkoxylate is highly soluble in water and gives low foaming in neutral and alkaline environments. It has high surface and interfacial activity in an alkaline medium and good wetting properties on a polar and solid surface.

 As such nonionic surfactants, for example, ethoxylated polyoxypropylene glycol derivatives of ethylene diamide or ethoxylated polypropylene ethylene diamine, known under the trademark Alcatronic EDP, EGE, PGP and others, which have a number of useful properties, including emulsifying and thickening (can be used as a thickener).

 When the content of nonionic surfactants is less than 1.5 wt. % the performance of the cleaning process is reduced, since it is difficult to "detach" hydrocarbon contaminants from the surface being cleaned, the speed of cleaning is slowed down, and when the content is more than 4.0 wt.%, there is an increase in the cost of cleaning, which is not practical.

 The use of soda ash as the active component is explained by the fact that it is the cheapest and most common detergent, although it is somewhat inferior in effectiveness to more expensive products, such as tripolyphosphate or trisodium phosphate. However, in cases where hydrocarbon pollution has a very complex composition or a high degree of pollution, especially old ones, it is advisable to use a more effective detergent. Such a need may arise in the case of a deficiency of soda ash or a lack of time in the presence of sodium salts of phosphoric acid.

 In practice, it was found that to achieve optimal cleaning performance it is enough to replace about 30% of soda ash, i.e. the ratio of soda ash: sodium salt of phosphoric acid should be in the range of 1.9-2.3: 1. From the foregoing, it is clear that with a larger ratio, there is a danger of reducing the cleaning efficiency, and with a lower ratio, the cost of the cleaning process increases.

As shown by studies conducted using detergents prepared from these compounds to clean the surface of liquid hydrocarbons, if the tank is made of non-ferrous metal, such as aluminum, then an aqueous solution of detergent with a concentration of 1.5-2.5% is used, if the surface is made of steel or cast iron, then a 2.0-4.0% washing solution is used. At lower concentrations of the washing solution, the time of the cleaning process increases, and at a higher concentration, the cleaning costs increase. The temperature range of the washing solution 40-55 ^o C is optimal for cleaning time. At a temperature of less than 40 ^o With the cleaning time increases, and with a larger value of the specified limit, the cleaning efficiency decreases, because foaming increases, and the activity of nonionic surfactants decreases.

 The self-cleaning thin-layer sump is a structure with a plane-parallel nozzle placed in its body. Self-cleaning nozzles is achieved by the selection of processing modes, as well as the corresponding inclination of the plates, which depends on the composition and properties of the mixture being separated. Various designs of such self-cleaning thin-layer sediment tanks are protected by RF patents 2032443 and autosvid. 1001961 (coalescing separator) having some structural differences.

 A coalescing separator is a block of parallel plates oriented vertically. The gap between the plates is provided by gaskets. The separated mixture (emulsion) enters it through the upper nozzle and is distributed through the slotted channels, which have three sections: vertical, where oil particles are separated on the plate walls; rotation, where the flow changes orientation in the gravitational field, and expansion, where the separated organic phase emerges in the upper part of the apparatus and is displayed in the collection of decanted oil products. The purified water enters the tank with the cleaning solution.

Compared with the best foreign analogues, for example Utility Vault Co, self-cleaning thin-layer sedimentation tanks do not require frequent stops and dismantling for cleaning and regeneration of a plane-parallel nozzle. Compared to settling tanks equipped with a Quantek corrugated nozzle, which has an inclination angle of only 45 ^° , the above settling tanks provide any angle of inclination of the plates and exclude repeated mixing of the separated phases.

 With a small delay, it is possible to separate hydrocarbon particles with sizes up to 10 μm and the accumulation of solid phase particles in the gaps formed by vertical plates is excluded.

 The efficiency of using self-cleaning thin-layer sedimentation tanks increases due to the fact that as a result of the use of a washing solution of the indicated composition of TMS, a static charge of a contaminated solution is not created. It is almost neutral, so the organic phase is pressed against the plates and washed out on their surface, increasing the degree of separation from the contaminated solution.

 Passing the emulsion, which is a mixture of hydrocarbon contaminants and a washing solution through a self-cleaning thin-layer sump, allows you to catch the bulk of the contaminants at this stage and thereby virtually eliminate the stage of gravity sludge contaminated washing solution. As a result of this separation of the emulsion, the recovery of liquid hydrogen was 98.5% compared to 95% of the prototype.

 Depending on the type of contaminants and the surface material, as already noted above, it is necessary to maintain a certain concentration of the washing solution. The concentration of the washing solution is controlled by residual alkalinity by the method of titration with hydrochloric acid with an indicator of methyl orange. The correspondence of the total alkalinity of the washing solution to its concentration is given in table 1.

 In practice, the adjustment of the solution is carried out after 6-8 cleaning cycles by adding freshly prepared washing solution in an amount sufficient to bring the total concentration to a predetermined value.

 An example of the implementation of the proposed method is the operation of a universal mobile washing station (UMPS), with which rail and tank trucks, vertical, horizontal and underground stationary tanks, as well as other containers for storing and transporting liquid hydrocarbons, can be washed.

 UMPS is protected by the RF certificate 13333 for a utility model and presents a design that includes the following main components: a washing solution tank 1, a pressure pump 2 for supplying a washing solution to the washing zone 3 (tank), a washing solution heater 4, a jet washing device representing a washing complex heads 5, installed with the possibility of their orientation, a device for pumping a mixture of washing solution and washing products 6 (membrane type pump) into the tank with the washing solution. A self-cleaning thin-layer sedimentation tank 7 is installed on the pumping line of the contaminated washing solution, representing a block of inclined plates that can be placed directly in the tank with the washing solution or separately from it. To ensure better operation of the sump on the drainage line of the purified solution, loop 8 was made, which plays the role of a water seal. By means of a device (not shown) for pumping liquid hydrocarbons to a storage tank, a separated phase for decanted product 9 is output. All tanks, pumps, etc. connected by appropriate pipelines with shutoff and control valves installed on them.

 UMPS is equipped with a docking device with a tank or storage tank, which are cleaned (not shown).

The process of washing the tanks begins with the preparation of a washing solution, which is prepared at the rate of 15-20 kg of dry detergent of the specified composition, if the material of the tank is non-ferrous metal and 25-40 kg, if the tank is made of steel, per 1000 liters of water. A washing solution is prepared by batchwise dissolving the detergent in water heated at least 40 ^° C (40-60 ^° C), with thorough mixing (stirrer, bubbler with compressed air, etc.).

In this example, a steel tank with a capacity of 63 m ^{3 is} washed with a 3.5% solution of detergent having a composition of 3.0 wt.% Nonionic surfactants, which is an ethoxylated polyoxypropylene glycol derivative of ethyldiamine (Alcatronic EDP) and 97 wt.% Soda ash. The specified washing solution from the tank UMPS using the ejector was fed into the washing heads installed inside the tank, each of which has two nozzles. The pressure of the washing liquid was 1.5 MPa. The temperature of the washing solution was controlled by a thermometer and maintained in the range of 45-55 ^o C by heating it with a coil. After a 10-minute jet washing, the resulting emulsion, which is a mixture of a washing solution and liquid hydrocarbons, was pumped out using a membrane pump.

 Contaminated washing solution enters the upper part (pipe) of a self-cleaning thin-layer sedimentation tank, on the plates of which the bulk of fatty, silty contaminants settle. A practically cleaned washing solution enters through the upper nozzle into the reservoir in which the washing solution is located. The washing solution for washing is taken from the bottom flange of the tank. The phase separation time was only a few minutes.

 The organic phase floats into the upper part of the sump and is removed using a pump or special grease traps in the storage tank of the decanted product. Periodically, a sample is taken through a sampler installed on the supply line of the washing solution and the total alkalinity of the solution is checked. In our case, after eight washing cycles, about 30 liters of water and 800 g of detergent were added to adjust the set concentration.

 When using a detergent composition, wt.%: Nonionic surfactants 3.0; tripolyphosphate 30; soda ash the rest is up to 100, the washing time is slightly reduced (up to 7 minutes).

 The degree of extraction of hydrocarbon compounds from the emulsion was 98%.

 The brigadier draws up an act in the form of VU-19 for the washed tank, and the next tank is put for washing.

 The method was tested not only on railway tanks, but also other various objects. So in table 2 shows data on cleaning tanks for storing petroleum products, and in table 3 - vertical cylindrical tanks of various capacities under the shield roof. Detergent solutions with a concentration of 3-4% detergent were used.

 On average, when using a detergent containing the same amount of nonionic surfactant and a different active component, only soda ash or partially replaced with sodium salts of phosphoric acid, the washing time differs by 8-12%, or to achieve the same result, the concentration of the washing solution is reduced by 0.10-0.18 wt.%.

Testing of the proposed method showed that, in comparison with the known technologies for cleaning surfaces from hydrocarbon compounds and detergent compositions used for these purposes, it has several advantages, namely:
- an increase in the degree of extraction of hydrocarbon compounds from the contaminated washing solution to 97-98.5%;
- reduction of energy consumption by lowering the temperature of the washing solution in the cleaning process;
- simplification of the design process, because the regeneration of the spent washing solution takes place in the same container as the main washing solution;
- the use of the proposed composition eliminates the use of more expensive detergents, which additionally contained sodium salts of polyacrylic acid and a corrosion inhibitor;
- improving the ecology of the environment and working conditions of staff by eliminating the above components;
- reducing the cost and time of cleaning from hydrocarbon pollution per unit of usable area.

 The proposed method and composition of the detergent will find application in various industries, as evidenced by the positive reviews received from organizations that carry out their testing.

Claims (3)

 1. A method of cleaning the surface of hydrocarbon contaminants in a closed cycle, comprising preparing a detergent containing 2-4 wt. % non-ionic surfactant based on fatty alcohol alkoxylate and an active component containing only soda ash or partially replaced with sodium salts of phosphoric acid, ethoxylated polyoxypropylene glycol derivatives of ethylene diamide or ethylene diamine are used as a non-ionic surfactant, and the surface is washed with water pumping the emulsion obtained, separation of the emulsion into aqueous and organic phases by passing it through ca a washable thin-layer sump made in the form of plane-parallel vertical coalescing plates forming slit gaps, with the subsequent return of the aqueous phase to the cleaning cycle and periodic removal of the organic phase into the collector.  2. The method according to p. 1, in which with a partial replacement of soda ash as sodium salts of phosphoric acid, tripolyphosphate and / or trisodium phosphate is used with a weight ratio of soda ash: sodium salts of phosphoric acid (1.9-2.3): 1.  3. The method according to p. 1 or 2, in which for washing, depending on the surface material and type of contamination, an aqueous washing solution with a concentration of detergent in it in the range of 1.5-4.0 wt. %

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