RU2314881C1 - Method of stripping of the electrical equipment from the mixture of polychlorobiphenyls and trichlorobenzenes - Google Patents

Abstract

FIELD: electrical industry; chemical industry; other industries; methods of stripping of the electrical equipment from the mixture of polychlorobiphenyls and trichlorobenzenes.

SUBSTANCE: the invention is pertaining to the electrical industry, in particular, to the method of stripping of the electrical devices containing the mixture of polychlorobiphenyls and trichlorobenzenes (PCB) and may be used at decontamination and salvage of the electrical equipment, for example, the power transformers and condensers. The methods of stripping of the electrical equipment from the mixture of polychlorobiphenyls and trichlorobenzenes (PCB) includes: drain of the PCB from the electrical equipment; filling-up of the internal volume of the electrical equipment with chloroform for the period of no less than 12 hours; drain of chloroform; treatment of the electrical equipment containing the mixture of chloroform with the steam; removal of the residues of the mixture by vacuum. At that the stripping cycle, beginning from the operation of filling-up of the electrical equipment with chloroform repeat not less than three times. The technical result of the method is the increased degree of the stripping, decrease of its explosion-fire hazard and the anthropogenic damage to the environment.

EFFECT: the invention ensures the increased degree of the stripping, the decrease degree of its explosion-fire hazard and the anthropogenic damage to the environment.

2 cl, 3 tbl, 3 ex

Description

The invention relates to the electrical industry, in particular to a technology for cleaning apparatus containing polychlorobiphenyls and trichlorobenzenes (hereinafter - PCBs), and can be used in the disposal and disposal of electrical equipment, such as power transformers and capacitors.

Currently, the threat of pollution of both the water and air basins of the environment with highly toxic products known in the industry under the names "Sovtol-10", "Askerel", "Arochlor-1242", "Sovol", which is a mixture of polychlorobiphenyls and trichlorobenzenes with various concentrations and additives and contained in electrical equipment that has worked out the standard operating life.

PCBs are one of the most widespread environmental pollutants found in almost all environments (air, water, soil, food, etc.). PCBs are highly toxic compounds that cause damage to the liver, kidneys, skin, and suppress the immune system of humans and animals. Therefore, the norms of the maximum permissible concentration (MPC) in the air of the working zone of 1 mg / m ^{3 were established} (see, for example, the article by A. Makarov, Ecological safety of storage of spent Sovtol and electrotechnical equipment contaminated with it // Materials of the Russian Conference on Methods for Disposal of Persistent organic pollutants (POPs), St. Petersburg, Russian Federation July 9–13, 2001, p. 159), The combination of the toxic properties of PCBs with their resistance to the environment served as the basis for including them among the 12 most dangerous organic FIR pollutants of the environment.

In this regard, the operation of electrical equipment where PCBs are used as dielectric is currently prohibited. As a result of such a ban, a problem arose in the disposal of this equipment from PCBs.

However, the cleaning of electrical equipment from PCBs is difficult, due to the complexity of the design of high-voltage electrical devices. So, the transformer is a closed case, which contains copper windings with a common magnetic core. In addition, the transformer contains wooden racks that hold the main parts in place. All the free space is filled with transformer oil, which contains PCBs as its main component.

Like a transformer, a high-voltage capacitor is a sealed metal container containing an active core made of solid plates of thin metal foil (aluminum), twisted together and separated by an insulating polypropylene film and / or PCB-impregnated paper. This core is located inside the capacitor housing, and all the free space is filled with capacitor PCB oil.

Therefore, the complex arrangement of transformers and capacitors, the presence of highly toxic oil cause serious problems in cleaning this equipment from residual PCBs.

Known technologies for cleaning the metal surfaces of transformers and capacitors from PCBs using organic solvents such as mineral alcohols and gasoline have achieved significant success. However, special problems arise with the cleaning of PCBs of porous materials inside electrical equipment, since during operation they accumulate a significant amount of PCBs.

Known methods for cleaning electrical equipment are associated with the use of fire hazardous solvents, with the burning of liquid waste with PCBs and porous materials with PCBs, therefore they are fire and explosive, and also require large financial costs for environmental measures, since the combustion process itself is environmentally friendly dangerous. In addition, during the combustion of PCBs, the formation of even more dangerous and toxic products compared to PCBs is possible - polychlorinated dioxins, which during combustion can enter the atmospheric air and accumulate in various environmental objects (see, for example, the article by A. Kuntsevich Systematization and risk assessment of superecotoxicants // Advances in Chemistry. - 1991. - T.60.- No. 2, p. 530-535).

Known technology utilization sovtol-containing transformers, implemented by JSC "Transformer" Togliatti. This technology includes sovtol draining from a transformer into tanks equipped with a submersible pump. Sovtol is transferred from tanks to a blast furnace through a pipeline. The transformers are cleaned of residual amounts of sovtol using a washing solution, which at a temperature of (85-90) ° C circulates along the inner circuit of the transformers. Sovtol is washed off the walls of the case, windings and packages of transformer iron, thereby cleaning the transformer (see Internet, access mode: http://www.transfomiatorjsc.ru/eng/contact.htm,http://transform.ru/salvaging/ / ss / php / phb. ttm, 04/15/2004).

The degree of washing the transformer casing from sovtol residues reaches 99.5%. This technology for cleaning transformers from residual quantities of sovtol is quite simple and economical. However, it has a significant drawback. The known method for cleaning transformers involves the burning of significant quantities of PCBs and does not allow to clean to a safe level porous materials (for example, wood, cardboard) inside the transformer.

There is also a method of cleaning transformers from PCBs and other polluting residues, according to which the process of cleaning the transformer is carried out due to the action of ultrasound on PCB-containing transformer oil, with the regeneration of the solvent and the burning of PCB-containing products (see German patent for invention No. DE 3615036, IPC Н01F 27/14, publ. 11/05/1987).

However, the known method of cleaning the transformer is expensive and does not allow you to clean the porous materials of the transformer to the required level, and when disposing and disassembling the transformer provides for their burning.

A known method of cleaning a transformer from PCBs is used in a device for removing polychlorobiphenyls from electrical apparatus, according to which it is proposed to connect two liquid circulation systems to it to clean a transformer from PCBs. One system is a circulation circuit: a transformer filled with a solvent and a liquid dielectric (trifluorotrichloroethane and / or perchlorethylene) and a pump circulating these liquids through the transformer to dissolve the remaining PCBs in the transformer. The transformer is connected to the network to maintain normal temperature and pressure. In the second, external, circulation system, the liquid exiting the transformer is heated to the boiling point of the liquid dielectric used, which evaporates, condenses and returns to the transformer, and the PCB remains in the liquid phase in the vessel (see US Patent No. 4790337, IPC V08V 03/10, publ. 12/13/1988).

A disadvantage of the known method is the need to use a complex expensive mixture (solvent + liquid dielectric) for washing the transformer from PCB residues. In addition, the known method is effective only for cleaning metal surfaces, while porous materials are not cleaned.

A known method of cleaning a transformer from an insulating liquid based on polychlorobiphenyl, including draining the insulating liquid from the transformer, cleaning the solvent vapor from the remnants of the insulating liquid, the drain of the insulating liquid is made from a preheated transformer, after which the transformer is cooled below the boiling point of the solvent, solvent vapor is supplied, the condensate formed on the inner surfaces and the active part of the transformer it removes impurities and leaches non-leaking residues of the insulating liquid from the bottom of the transformer, the resulting liquid phase is sent to evaporation for repeated treatment of the transformer with the regenerated solvent in a closed circuit, and methylene chloride is used as the solvent (see RF patent for the invention No. 2187858, IPC Н01F 27 / 14, B08B 03/08, publ. 08/20/2002).

However, cleaning the transformer from the remains of the insulating liquid using methylene chloride vapors is effective only for the active part and leaching of indelible residues of the specified liquid, since in this case there is no cleaning from the PCB of porous materials. In addition, with the repeated use of electrical equipment, PCB is converted to a new dielectric and the transformer again becomes PCB-containing.

There is also a method for the neutralization of polychlorinated biphenyl-containing products, which consists in the fact that the products are heated with a gas-oxygen torch with a temperature of at least 2000 ° C until a temperature on their surface is reached of 600-750 ° C with heating of the walls of the afterburning chamber to temperatures above 1000 ° C, released from the products the gases are heated at the inlet in the afterburner to a temperature of at least 1300 ° C in the absence of free oxygen with the simultaneous supply of ammonia in an amount that ensures the binding of hydrogen chloride, and burned up with oxygen at the outlet of the afterburning chamber 3-5%. The residence time of the evolved gases in the afterburner provides at least 1.5 s. At the exit from the afterburner, the gases are sucked through a layer of kaolin wool with the simultaneous injection of ammonia (see RF patent for invention No. 211,19615, IPC F23G 07/06, published on 09/27/1998).

The known method is very energy intensive, and therefore expensive and can only be used for the disposal of small items contaminated with PCBs. It is not possible to neutralize large-sized equipment (for example, transformers with a mass of 2 tons or 3 tons), as this will require the availability of special furnaces for burning off exhaust gases. In addition, the known method cannot be used for continuous industrial neutralization of electrical equipment, and use is possible only for the neutralization of a limited number of small items.

Closest to the proposed technical solution is a known method for removing polychlorobiphenyl residues from transformers using water vapor, which form a low boiling azeotrope with PCBs, and removing it using vacuum, followed by cooling. The cleaning process consists of cycles, including steam treatment for 10 minutes - evacuation of 5 minutes. Alternation continues until the temperature in the transformer is no higher than the boiling point of the azeotrope. In this case, solvents are used that form low-boiling azeotropes with PCBs, including, for example, water, methanol, toluene and acetonitrile (see US patent for invention No. 4699667, IPC B08B 05/00, B01D 15/04, publ. 13.10.1987 g .).

However, the known method has the following significant disadvantages:

- water vapor only cleans metal surfaces, while porous materials (wood, cardboard) are not cleaned from PCBs, since water vapor does not penetrate into the pores of wood and cardboard structures inside the transformer that are deeply impregnated with PCBs. A transformer with wooden and cardboard structures impregnated with PCBs remains environmentally hazardous even after filling it with another dielectric fluid, since residual PCBs from porous materials diffuse into a dielectric, turning the transformer into PCB-containing;

- PCBs from the condensate are captured by activated carbon, which is subsequently burned, which increases the amount of dioxin-like substances that destroy the atmosphere;

- the cleaning process is energy-intensive, as it consists of cycles: steam treatment for 10 minutes - evacuation for 5 minutes, and the entire cleaning cycle of the transformer can last from several hours to several days.

The objective of the present invention is to provide a method that has a reduced explosion and fire hazard and provides an increased degree of purification of electrical equipment from PCBs, and does not require special measures to ensure environmental safety in the process of its implementation, which reduces the anthropogenic load on the environment during the cleaning of electrical equipment from PCBs.

The technical result achieved in solving this problem is to achieve a degree of purification of porous materials inside electrical equipment to a value of 99.99% in the absence of waste incineration processes from PCBs and PCB-containing compounds, as well as obtaining a residue containing PCBs suitable for subsequent disposal.

The specified technical result is achieved by the fact that the method of cleaning electrical equipment from a mixture of polychlorobiphenyls and trichlorobenzenes (PCBs) includes draining PCBs from electrical equipment, filling the internal volume of electrical equipment with chloroform for at least 12 hours, draining chloroform, processing electrical equipment containing a mixture of chloroform and PCBs, with steam, removal of the residual mixture with vacuum, while the cleaning cycle, starting with the operation of filling the electrical equipment with chloroform, is repeated at least three times.

In addition, the processing of the internal volume, internal parts and materials of electrical equipment containing a mixture of chloroform and PCB, steam and the removal of the residual mixture with vacuum is carried out both without disassembling it and in a chamber with its disassembling into individual parts, including porous materials.

Common features of the proposed technical solution and prototype are the following: draining PCBs from electrical equipment, injecting electrical equipment with steam, using a vacuum to remove residues resulting from the cleaning process.

Distinctive features of the proposed technical solution from the prototype are the following: filling the internal volume of electrical equipment with chloroform for a period of at least 12 hours, draining chloroform, processing electrical equipment containing a mixture of chloroform: PCB, steam, removing residues of a mixture of chloroform: PCB: water with vacuum, while cleaning, starting with the operation of filling the electrical equipment with chloroform, is repeated at least three times.

When checking the possibility of using a number of solvents (organic and organochlorine) to clean PCB electrical equipment, chloroform showed the ability to penetrate the pores of porous materials, giving the effect of "swelling". When using other solvents, the effect of "swelling" was not observed and they did not allow the cleaning of porous materials from PCBs, although they made it possible to clean metal surfaces of electrical equipment from PCBs up to 99.99%. Thus, chloroform in the proposed cleaning method is a cleaning agent from PCBs of both metal surfaces and porous materials of electrical equipment.

Filling the electrical equipment with chloroform leads to the “swelling effect” of wooden elements (for example, wooden posts that hold the main parts in place) of this electrical equipment for a time determined experimentally and amounting to at least 12 hours. When the chloroform is held for less than 12 hours, the saturation of the porous materials of the electrical equipment with chloroform decreases and the PCB fraction dissolves in chloroform, which requires additional cleaning of the electrical equipment to a degree of purification of 99.99%.

When vacuum is connected to electrical equipment after chloroform is drained from it without steam pretreatment, chloroform evaporates from the surfaces of electrical equipment, while PCB settles inside the electrical equipment.

Processing of electrical equipment with a residual amount of chloroform and PCBs by steam promotes the formation of a “chloroform-PCB-water” mixture in inaccessible places of electrical equipment and in the pores of porous materials, as a result of which, using vacuum, chloroform and PCBs are not evaporated in a mixture with chloroform and water vapor electrical equipment. Repeating the cleaning operation "chloroform: steam: vacuum" three times allows you to bring the degree of purification of electrical equipment to 100%.

The analysis of the residue obtained after the regeneration of chloroform solutions with PCB, carried out using a gas chromatographic technique, shows that it consists of PCB fractions similar to the composition of sovtol, which is used to obtain PCS-T paste. The treatment of bottoms containing PCBs with oleum and triethanolamine using a known technology showed that it is possible to convert the highly toxic PCB compound to a hazard class IV compound - PCDS-T paste, which is used as an antiseptic for wood. Moreover, during the cleaning process, the burning of harmful PCB-containing wastes is not required, thereby achieving the explosion and fire safety of the proposed method.

To assess the possibility of using the proposed method for cleaning the transformer from residual PCBs, for example sovtol, a laboratory model of the transformer was assembled, which was a glass case with upper and lower holes, where clean metal and wooden elements of the transformer were placed. The transformer model was poured with sovtol heated to a temperature of 90 ° C, the contents were held for 24 hours, then the sovtol was merged, and the transformer model was filled with chloroform for at least 12 hours. A holding time of at least 12 hours was experimentally determined by studying the diffusion of sovtol from a tree to chloroform and chloroform into a tree, and the pores of the tree are filled with chloroform (“swelling” effect). At the end of the exposure, chloroform merged and the transformer model was processed, containing the remains of chloroform and sovtol, with water vapor at a temperature of 100 ° C for 30 minutes, then a “vacuum extraction” of the mixture “chloroform: PCB: water” was made, and the vacuum was 15-20 mm Hg. Art. created by a vacuum pump. After removing the mixture “chloroform: PCB: water” from the transformer model, the latter was air dried to constant weight. The chloroform: PCB: water mixtures obtained by treating the model with steam and vacuum were cooled and separated. The layer containing chloroform and sovtol, and chloroform, after holding the model for at least 12 hours, were sent for regeneration. The water layer was sent to process the model with steam. Purified chloroform was used for subsequent filling of the model, and the residue containing sovtol was disposed of, i.e. was treated with oleum and triethanolamine to obtain a paste PCB-T.

The results of experiments on cleaning the transformer model from sovtol are presented in table 1. Analysis of the experimental data on washing the laboratory model of the transformer from sovtol shows that if the model has metal elements of the transformer (see experiment 1, table 1) after two times the surface is cleaned by 100, 0% After cleaning, the metal elements had a shiny surface, without any deposits.

The results of experiment 2 (table 1), when porous materials are present in the laboratory model (wood, for example beech, as well as cardboard), show that after draining sovtol a significant amount of sovtol remains, the saturation level of sovtol is 45.0%. After the discharge of chloroform, chloroform penetrated into the pores of the elements of wood and cardboard (the effect of "swelling") and the displacement of PCBs. This can be seen in these experiments from data on the weight of Sovtol and data on the increase in the weight of the laboratory model of the transformer after the discharge of chloroform. After three times processing and after drying the model with air to a constant weight, the degree of purification of porous elements was 99.99%.

The research results are also confirmed by the following examples.

Example. The sovtolny transformer of the TTAZ K206 brand was put on the scales. According to the passport data: the weight of the sovtol poured into the transformer was 71.0 kg, and the weight of the transformer with sovtol was 211.0 kg. Sovtol from the transformer merged and the transformer was weighed. The entire transformer volume was filled with chloroform and held for 12 hours (see experiment 1, table 2) and for 11 hours (see experiment 2, table 3). After exposure, chloroform with sovtol from the transformer merged. Steam with a temperature of 100-130 ° C was supplied to the transformer with a residual amount of chloroform and sovtol until the temperature in the transformer reached 95-100 ° C (the temperature change was controlled using a thermocouple inside the transformer). The mixture "chloroform: PCB: water" leaving the transformer was cooled and collected in a collector. A vacuum pump was also connected to a heated transformer at a vacuum of 10-15 mm Hg. “vacuum extraction” was carried out for 15-20 minutes to remove the residues of the mixture “chloroform: PCB: water”. The operation of filling with chloroform, holding it, draining, steaming and vacuum removing the resulting mixture of “chloroform: PCB: water” was repeated several times, then air drying was carried out to constant weight. From the collection of the mixture “chloroform: PCB: water”, obtained both by treating the transformer with steam and by “vacuum drawing”, the chloroform layer containing PCB was separated, which was combined with chloroform drained from the transformer and sent to evaporation. Purified chloroform was used to refill the transformer, and the bottom residue containing PCB, which was sovtol in composition (determination of which was carried out, for example, using a known chromatographic technique), was utilized by treatment of oleum and triethanolamine.

The results of experiments on cleaning the transformer brand TTAZ K206 are presented in table 2 (experiment 1) and in table 3 (experiment 2).

The results of experiments on the cleaning of PCB transformer brand TTAZ K206 during exposure with chloroform for 12 hours

table 2 Transformer weight Number of treatments Drying transformer to constant weight (kg) PCB Transformer Cleaning Efficiency (%) The amount of PCBs on the surface (mg / cm ² ) without sovtol (kg) before draining Sovtol (kg) after draining Sovtol (kg) one 2 3 four 5 6 7 140.0 211.0 144.9 1st 140.8 90.1 2nd 140.1 98.01 3rd ~ 140.0 ~ 100.0 less than 0.1 · 10 ^-2

The weighing results of the transformer brand TTAZ K206 (table 2) show that the degree of purification after 3-fold processing and drying tends to 100%.

The control of the surface cleanliness of the inner circuit of the transformer was determined by the results of flushing using a well-known gas chromatographic technique.

The results of experiments on the cleaning of PCB transformer brand TTAZ K206 during exposure with chloroform for 11 hours

Table 3 Transformer weight Number of treatments Drying transformer to constant weight (kg) PCB Transformer Cleaning Efficiency (%) The amount of PCBs on the surface (mg / cm ² ) without sovtol (kg) before draining Sovtol (kg) after draining Sovtol (kg) one 2 3 four 5 6 7 140.0 211.0 144.9 1st 141.0 79.59 2nd 140.6 87.76 3rd 140.1 97.96 4th ~ 140.0 ~ 100.0 less than 0.1 · 10 ^-2

The results of experiment 2 (table 3) on washing the transformer in a manner different from the proposed exposure time of chloroform in the transformer for 11 hours show that in order to achieve a degree of purification of ~ 100%, an increase in the number of treatments to 4, i.e. additional energy and time costs will be required.

The control of the surface cleanliness of the inner circuit of the transformer was determined by the results of flushing using a well-known gas chromatographic technique.

The mixture "chloroform: PCB: water" after steam treatment of the transformer and vacuum drawing is cooled and separated. Chloroform containing PCB after discharge from the transformer and the chloroform layers obtained after steam and vacuum extraction were passed through the transformer are regenerated to produce chloroform purified from PCB and VAT residue, the chromatographic analysis of which showed compliance with the composition of sovtol. The purified chloroform is sent to refill the transformer, and the bottom residue is disposed of in a known manner, for example, by reacting oleum and triethanolamine to obtain a PCDS-T paste.

The results of experimental tests of the proposed method for removing residual amounts of PCB-containing compounds from electrical equipment allow the following conclusions:

- a method of cleaning electrical equipment, including pouring chloroform, holding it, draining, treating electrical equipment containing a mixture of chloroform and PCB, steam, removing the mixture with vacuum, well cleans PCB (sovtol) metal parts (surfaces) and porous materials (wood) , cardboard);

- no operations are required to incinerate PCB-containing substances, which increases the safety of the method, excluding the occurrence of fires and explosions involving the release of harmful substances;

- the transformer model can also be considered as a chamber for cleaning PCB (sovtol) elements of electrical equipment.

This allows us to recommend the proposed method for cleaning PCBs of electrical equipment, such as power transformers and capacitors, with their disassembly.

Thus, the removal of the residual amount of PCBs (for example, Sovtol) from electrical equipment by the proposed method allows you to:

- increase the cleaning efficiency, as well as clean the metal surfaces and porous elements of the transformer from PCBs (the degree of purification from PCBs is 99.99%);

- reduce the anthropogenic pressure on the environment by eliminating the processes of incineration of wastes with PCBs;

- expand the technical capabilities of the method specified in the prototype, using cameras for cleaning transformer elements, which reduces the time of their cleaning.

The proposed method can also be used for cleaning porous materials from PCBs in the case of cleaning power transformers by other methods, as well as when contaminating porous materials with other toxic organic compounds soluble in chloroform.

Thus, the cleaning of electrical equipment using the proposed method allows to make the process of removing residual PCBs from power transformers and capacitors environmentally and technically safe.

Claims (2)

1. A method of cleaning electrical equipment from a mixture of polychlorobiphenyls and trichlorobenzenes (PCBs), including draining PCBs from electrical equipment, filling the internal volume of electrical equipment with chloroform for at least 12 hours, draining chloroform, treating electrical equipment containing a mixture of chloroform and PCB, with steam, removing the mixture with vacuum while the cleaning cycle, starting with the operation of filling the electrical equipment with chloroform, is repeated at least three times. 2. The method according to claim 1, in which the processing of the internal volume and internal parts and materials of electrical equipment containing a mixture of chloroform and PCBs, steam and the removal of the remainder of the mixture by vacuum is carried out both without disassembling it, and in a chamber with its disassembling into individual parts, including porous materials.