RU2381579C1 - Method of processing radioactive ion-exchange resins and industrial toxic liquid wastes - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to environmental protection, and more specifically to methods of processing (decontaminating) spent radioactive ion-exchange resins (IER) and industrial liquid toxic wastes (LTW) which contain environmentally hazardous substances, particularly toxic ethyleneglycol. Spent radioactive ion-exchange resins at the decontamination stage are subjected to thermal treatment at 101-150°C while moving in a solution of hydrophilic high-temperature organic coolant in form of ethyleneglycol or used cooling and hydraulic liquids based on ethyleneglycol with addition of phthalic anhydride with weight ratio of anhydrous components in the solution ranging from 1.0 to 2.3 g of phthalic anhydride per 1.0 g of ethyleneglycol.

EFFECT: decontamination of radioactive ion-exchange resins, recycling industrial spent solutions of cooling and hydraulic liquids based on toxic ethyleneglycol; reduced energy and financial expenses on carrying out the process; simplification of the technology of decontaminating radioactive ion-exchange resins and liquid toxic wastes; reduced technogenic effect of hazardous substances on the environment.

3 cl, 2 tbl

Description

The invention relates to the field of environmental protection, and more specifically, to the processing technology (disposal) of spent radioactive ion exchange resins (IOS) and industrial liquid waste containing toxic organic substances that have spent their regulatory lives.

Ion-exchange water purification technologies used at nuclear power facilities are one of the sources of the generation of environmentally hazardous radioactive waste, which are pulps of IOS that have fulfilled their regulatory time. It is also known that during the operation of vehicles and industrial installations, in the working systems of which water-containing liquids based on glycols (most often, ethylene glycol) are used [A. M. Sukhotin et al. Non-combustible heat transfer fluids and hydraulic fluids. Chemistry, Leningrad, 1979, p. 266], significant volumes of liquid toxic waste (ZhTO) are formed, which are cooling and hydraulic fluids that have developed a lifetime.

To ensure environmental safety during long-term storage of radioactive IOS and disposal of radioactive wastes, a set of measures is required to render them harmless. It is obvious that the main conditions for organizing an effective technology for the disposal of environmentally hazardous waste, regardless of their condition (solid waste or liquid), are not only the requirements for the maximum reduction in the volume of the final product to be disposed of and its reliable isolation from the environment, but also the minimum consumption, cost and availability of reagents and materials used in the waste disposal cycle.

In the practice of neutralizing spent radioactive IOS, the methods of their inclusion (monologization, immobilization) in traditional binders are widely used: thermoplastic (bitumen, etc.), inorganic (cement, gypsum, etc.), thermosetting (polyester, urea resins, etc.) . Sorbents are included in the binders of the first group at elevated temperatures (180-240 ° C), and the second and third ones at room temperature [A.S. Nikiforov, V.V. Kulichenko, M.I. Zhikharev. Neutralization of liquid radioactive waste. M., Energoatomizdat, 1985, p. 115, 116, 126, 132, 136]. It is known that to obtain strong monoliths, the used ion-exchange resins must be dehydrated as much as possible before being included in the binders of the second and third groups to eliminate excessive volume and because of the ability of IOS to swell when they come in contact with water [RF patent No. 2062517, publ. 06/20/96; RF patent №2114471, publ. 06/18/97; A.S. Nikiforov, V.V. Kulichenko, M.I. Zhikharev. Neutralization of liquid radioactive waste. M, Energoatomizdat, 1985, p.114-115]. Deep dehydration of IOS, which can significantly reduce their volume and eliminate the ability of sorbents to swell when in contact with water, is achieved at thermal (temperature 350-395 ° C) [RF patent No. 2068208, publ. 10.20.96] or thermochemical (temperature over 250 ° C, pressure 40 atm) [RF patent No. 2062517, publ. 06/20/96] their processing.

The methods for processing radioactive IOS discussed above have their advantages and disadvantages. So, for example, the simplicity and manufacturability of the method of direct homologization of wet IOS with cement widely used in practice [A.S. Nikiforov, V.V. Kulichenko, M.I. Zhikharev. Neutralization of liquid radioactive waste. M., Energoatomizdat, 1985, p.132], even with a low degree of filling of the cement monolith in IOS (not more than 10% in dry resin), they do not provide the required strength of the final product and significantly increase its volume (2 or more times). Methods of immobilizing IOS in traditional hardeners with preliminary deep thermal treatment (processing temperature over 350-395 ° C) [RF patent No. 2068208, publ. 20.10.96] or thermochemical (temperature over 250 ° C and pressure in the apparatus over 40 atm.) [RF patent No. 2062517, publ. 06/20/96] their processing is energy-intensive and complicated in the hardware design of a process that requires the use of metal-intensive equipment operating at high pressure. In addition, the deep thermal or thermochemical degradation of IOS, up to the destruction of the high molecular weight IOS base, leads to the formation of volatile environmentally hazardous organic substances (mercaptans, amines, etc.), which complicates the gas purification system.

The closest in technical essence to the claimed method is a method of processing spent radioactive ion-exchange resin, including grinding IOS, heat treatment of the obtained IOS powder at a temperature of 170-350 ° C, providing decomposition of only ion-exchange groups of IOS without decomposition of the organic base of the resin and curing (immobilization, monolithization) undecomposed resin base by mixing it with a hardener [JP patent No. 61086693, publ. 05/02/1986].

The disadvantages of this method, selected as a prototype, are the complexity of the instrumentation of the technological process due to the need for a preliminary stage of mechanical grinding of IOS, the possibility of reducing the strength of the final products (monoliths) when they come into contact with water, since the method does not involve the degradation of the high molecular weight resin base, excluding the ability of IOS to swell when they come in contact with water. It is known that IOS lose their ability to swell in water as a result of their heat treatment at temperatures above 350 ° C [RF patent No. 2068208, publ. 10.20.96].

The objective of the present invention is to provide a method of processing spent resource radioactive ion exchange resins and liquid industrial waste containing toxic ethylene glycol, allowing:

- neutralize industrial liquid waste containing toxic ethylene glycol;

- reduce the financial costs for the purchase of reagents due to the use of glycols or used cooling and hydraulic fluids based on glycols as a high-temperature hydrophilic coolant in the IOS neutralization cycle, and ethylene glycol or used cooling and hydraulic fluids that have been used as the main component of the inert matrix (binder) based on it;

- reduce the volume of the final product subject to long-term storage, and increase its water resistance;

- to reduce the anthropogenic impact of harmful substances on the environment of the region during the neutralization of IOS and ZhTO and to improve the environmental situation during long-term storage of final products.

To solve the problem and achieve the technical result in a method of processing spent radioactive ion-exchange resin, including its heat treatment in a heated apparatus at a temperature that ensures the decomposition of only functionally active ion-exchange groups of IOS without decomposition of the organic base of the resin, and curing (immobilization, monolithic) of undecomposed the basis of IOS by mixing it with a hardener, it is proposed that the process of neutralizing the radioactive resin be carried out at a temperature urine of the product in a bath of 101-230 ° C under stirring conditions using glycols as a high-temperature hydrophilic heat transfer medium or glycols-based hydraulic and hydraulic fluids that have developed a resource, and ethylene glycol or cooling and hydraulic-life-generated as the main component of an inert matrix (binder) liquids based on it with the addition of phthalic anhydride when the ratio of components in the bath solution is 1.0 grams of ethylene glycol 1.0-2.3 grams of phthalic anhydride in terms of anhydrous s components.

It is also proposed that when a solution of ethylene glycol with phthalic anhydride is used in the IOS neutralization cycle, the process is carried out at the initial volume ratio of wet IOS to the solution in the bath from 1: 0.05 to 1: 1 until the product is obtained in the bath, which, after cooling to ambient temperature media, bulk hydrophobic granules, "an organic resin base impregnated with a polymer," or a monolith, "hydrophobic resin granules, incorporated into a polymer based on ethylene glycol and phthalic anhydride."

It is also proposed, when using a life-time cooling and hydraulic liquids based on ethylene glycol that have been used in the IOS processing cycle, the process of their simultaneous neutralization is carried out until the product "polymer solution - hydrophobic resin granules" containing at least 50 vol.% Organic resin base is formed in the bath and then the resulting product is cooled to ambient temperature until a molten, solid, water-resistant monolith is formed in the bath.

In addition, it is proposed that the initial volume ratio of wet IOS to the glycol-phthalic solution in the bath be determined on the basis of the requirements for the final state of the product and the conditions for its long-term storage (the presence or absence of additional insulating shells, etc.), ensuring environmentally safe long-term storage.

The essence of the proposed method lies in the fact that the principle "toxic is utilized in toxic" is laid down, namely, it is proposed that the spent radioactive ion-exchange resins be neutralized using glycols as a hydrophilic heat carrier or cooling and hydraulic liquids based on glycols that have developed a resource, and as one of the components of the insulating matrix (hardener) - ethylene glycol or industrial waste based on it, with the receipt of environmentally friendly neutralization at the final stage hazardous waste (radioactive IOS and toxic solutions of ethylene glycol) - waterproof products suitable for long-term storage.

The inventive method allows, in addition to radioactive IOS, to utilize other spent environmentally hazardous heterogeneous filter materials, namely, radioactive perlite, activated carbon, sludge, etc. [A. S. Nikiforov, V. V. Kulichenko, M. I. Zhikharev. Neutralization of liquid radioactive waste. M., Energoatomizdat, 1985, pp. 9, 10], and other high-boiling organic substances belonging to the class of dihydric alcohols (glycols) [A.A. Petrov et al. Organic chemistry. Higher School, Moscow, 1973, pp. 130-131], such as diethylene glycol, triethylene glycol, tetraethylene glycol and propylene glycol [A. M. Sukhotin et al. Non-combustible heat transfer fluids and hydraulic fluids. Chemistry, Leningrad, 1979, p. 269].

It is known [A. M. Sukhotin and others. Non-combustible heat transfer fluids and hydraulic fluids. Chemistry, Leningrad, 1979, p. 269], that the majority of ethylene glycol produced in the world is spent on the manufacture of antifreezes, which are aqueous solutions of ethylene glycol of various concentrations, containing corrosion inhibitors, buffered salt additives, etc. From the same source it is known that cooling and ethylene glycol-based hydraulic fluids are highly toxic. It is also known that trouble-free operation of automobile transport, where ethylene glycol-based antifreezes are used as a coolant, requires at least 1 time in 2 years to completely replace it with a new one. In this case, large volumes of toxic waste are generated (for only one passenger car - about 10 liters of liquid waste containing from 40 or more wt.% Of highly toxic, environmentally hazardous ethylene glycol), which, of course, requires the implementation of mandatory measures for their neutralization or regeneration.

The feasibility of the regeneration of antifreezes, as well as high-temperature organic coolants (BOT), is determined by their initial market value, the perfection of the regeneration technology and the operating costs of its implementation. The most acceptable way to regenerate BOT is their double distillation [A.V. Chechetkin. High temperature fluids. Energy, Moscow, 1971, p. 417]. Despite its simplicity, the thermal method of BOT regeneration has a significant drawback - it requires the consumption of a large amount of heat, which increases the cost of processing and the price of the secondary product. The method of burning spent antifreeze is economically and environmentally unjustified, since it requires the use of sophisticated equipment (for example, plasmatrons) with an effective gas cleaning system. Utilization of antifreeze agents at special landfills (“filtration fields”) is unacceptable for environmental reasons.

In this regard, the proposed method of neutralizing radioactive IOS using industrial waste containing toxic ethylene glycol in the cycle of their processing is very relevant.

It is known that the main disadvantage of water-glycol fluids when used in cooling systems and hydraulics of industrial plants and vehicles is the evaporation of water, especially at high temperatures [A. M. Sukhotin and others. Non-combustible heat transfer fluids and hydraulic fluids. Chemistry, Leningrad, 1979, p.266]. It is also known [A.A. Petrov, H.V. Balyan, A.T. Troshchenko. Organic chemistry. Higher School, Moscow, 1973, p.135] that ethylene glycol is very hygroscopic, miscible with water in all ratios. The presence of water in ethylene glycol sharply reduces its boiling point [A.V. Chechetkin. High temperature fluids. Energy, Moscow, 1971, p. 91]. It was experimentally established that when implementing the proposed method, the above-mentioned properties of ethylene glycol and solutions based on it (intensive evaporation of water from water-glycol liquids at elevated temperatures for their use, high hygroscopicity of ethylene glycol, etc.) and the process under conditions that provide direct contact of the hydrophilic coolant with wet granules of IOS, allow at the first stage of processing of IOS at a temperature of 101-150 ° C (see tables 1 and 2) to carry out not only deep dehydration of IOS and their drying But also to prepare a resin (resin impregnated granules phthalic-glycolic solution) to the final stage of its neutralization (immobilization step the resin in an inert matrix).

It is known [A.A. Petrov et al. Organic chemistry. Higher School, Moscow, 1973, p.135] that polyesters based on ethylene glycol and phthalic anhydride have been widely used in various industries as film-forming substances for varnishes and paints, as well as as the basis for polyester resins and synthetic fibers. The main chemical and technological parameters of the reaction for the synthesis of a polyester resin from ethylene glycol and phthalic anhydride are also known [A.P. Grigoriev, O.Ya. Fedotova. Laboratory workshop on technology of plastic masses, part 2. Higher school, Moscow, 1977, pp. 92-93].

The authors experimentally established that during the heat treatment of wet IOS in a medium containing ethylene glycol or a phthalic-glycol solution at a temperature of 101-150 ° C, sorbents are almost completely dehydrated, their volume, in comparison with the initial wet IOS, is significantly reduced, but at the same time sorbents do not lose their ability to swell in water. When the temperature of the product in the bath increases to 200-230 ° C and its further heat treatment is carried out in this temperature range for 3-4 hours, water-resistant products are formed in the bath, which, after they are cooled to room temperature:

bulk product - dehydrated granules of the organic resin base included in the inert polymer shell of the phthalic-glycol polyester (see specific examples, experiments 3-6, table 2), or

monolith - a polyester resin (solid matrix) containing at least 50 vol.% dry organic basis of the ion-exchange resin (see experiment 7 in the same table).

According to the authors, the requirements for the final state of the product subject to long-term disposal should be based on the requirements for ensuring the environmental safety of its long-term storage and the economic feasibility of using certain reagents used in the waste treatment cycle according to the proposed method.

So, for example, when using solutions based on ethylene glycol and phthalic anhydride in the cycle of neutralizing radioactive IOS, it is advisable to obtain a loose waterproof product at the final stage of neutralizing IOS that can be stored independently in primitive protective shells (polyethylene, metal, cement, etc.), so and be additionally monolithic in non-radioactive traditional matrices based on less expensive binders (thermoplastic or inorganic materials belonging to the first and second groups am binders) [A.S. Nikiforov, V.V. Kulichenko, M.I. Zhikharev. Neutralization of liquid radioactive waste. M., Energoatomizdat, 1985, p. 115, 130].

When solving the problem of the simultaneous neutralization of radioactive IOS and toxic industrial wastes containing ethylene glycol, it is naturally environmentally and economically justified to carry out the waste disposal process until a monolithic product is obtained, since this allows the processing of significant volumes of ZhTO with a high degree of its filling with the organic radioactive basis of IOS.

The proposed method is as follows.

Example 1

Wet radioactive IOS and the required amount of anhydrous ethylene glycol solution prepared in advance, are placed in a heated apparatus (container) equipped with a stirrer and a reflux condenser, which ensures the mixing of the product in the apparatus and the return of high-temperature sublimates (volatile organic substances at temperatures above 150 ° C), and with phthalic anhydride. The resulting mixture in the apparatus is heated with constant stirring to a boiling point, which mainly depends on the initial content in the product of water, and in the temperature range of 101-150 ° C, the stage is dehydrated IOS and their impregnation with a phthalic-glycol solution. After completing this stage of the heat treatment of the IOS, as evidenced by the cessation of water condensate from the apparatus and a sharp increase in the temperature of the product in the zone of its processing, the IOS is subjected to 3-4 hours heat treatment in the temperature range of 200-230 ° C until a mobile (tank) is obtained transportable) product, which, after cooling to ambient temperature, is a loose waterproof granules of the organic base of IOS, included in the protective inert shell of ethylene-based polyester resin glycol and phthalic anhydride.

Example 2

A mixture of wet radioactive IOS is placed in a heated apparatus (capacity) equipped with an inlet into the ZhTO apparatus, an agitator and a reflux condenser that mixes the product in the apparatus and returns to its reaction zone a high-temperature sublimation (volatile organic substances at temperatures above 150 ° C) and aqueous industrial transport wastes containing toxic ethylene glycol, with the addition of the necessary amount of phthalic anhydride. The product obtained in the apparatus is heated with stirring to a temperature of 100 ° C and water is distilled from it in the temperature range from 101 to 150 ° C. When the product temperature in the apparatus reaches 140-150 ° С, additional portions of ZhTO containing aqueous solutions of ethylene glycol with the addition of phthalic anhydride are periodically or continuously introduced into its reaction zone until the amount of ethylene glycol and phthalic anhydride necessary for subsequent polymer synthesis is generated in the apparatus. After the stage of drying the IOS and concentration of aqueous solutions of ethylene glycol, as evidenced by the cessation of water condensate from the apparatus and a sharp increase in temperature in the treatment zone, the mixture of IOS with ethylene glycol-phthalic solution is subjected to 3-4 hours heat treatment in the temperature range 200-230 ° C to obtaining in the apparatus of a mobile (transportable) product, which is a melt of a polyester resin based on ethylene glycol and phthalic anhydride, containing at least 50 vol.% dry organic basis of ion exchange resin, which after cooling to ambient temperature turns into a solid non-porous waterproof monolith.

There may be other hardware and technological solutions for the implementation of the proposed method for processing environmentally hazardous waste, which mainly depend on the design features of the apparatus used and the physico-chemical composition of the waste to be treated.

The main results of experiments to develop the proposed method and examples of its specific performance are shown in tables 1 and 2.

Table 1 The boiling point of aqueous ethylene glycol and phthalethylene glycol solutions at a weight ratio of ethylene glycol to phthalic anhydride of 1: 1 g / g Coolant The coolant content in water, vol.% 0 twenty 40 60 80 90 one hundred The boiling point of the solution, ° C ethylene glycol 100.0 102.5 104.6 110.5 121.5 140.0 197.3 ethylene glycol + phthalic anhydride 100.0 101.1 102,2 105,4 112.5 126.0 150-160.0

The boiling point of an anhydrous phthalic-ethylene glycol solution at a weight ratio of ethylene glycol to phthalic anhydride of 1: 2.3 g / g - 200-220 ° C.

table 2 The main results of examples of specific performance
The initial volume of wet IOS is 5 cm ³ . The average wet granule size is 0.9 mm. The ratio of ethylene glycol to phthalic anhydride in solution is 1: 1 g / g. The temperature of the heat treatment is 101-230 ° C. The heat treatment time of the product in the bath at a temperature of 200-230 ° C is 3.0 hours. Ex Source product V resin / V solution cm ³ / cm ³ End product characterization V, cm ³ Size *, mm Product status Product swellability in water one wet ios - 1,6 0.4 loose granules swells, stole 2 times 2 wet iOS + ethylene glycol 1,0 / 0,5 2.0 0.5 loose granules swells, stole. 1.1 times volume 3 wet iOS + glycolphthalic solution 1,0 / 0,05 2.1 0.5 loose granules does not swell four wet iOS + glycolphthalic solution 1,0 / 0,1 2.6 0.8 loose granules does not swell 5 wet iOS + glycolphthalic solution 1.0 / 0.2 3,7 0.8-4.1 loose granules + conglomerates does not swell 6 wet iOS + glycolphthalic solution 1,0 / 0,5 3.9 - porous monolith does not swell 7 wet iOS + glycolphthalic solution 1.0 / 1.0 4.7 - non-porous monolith does not swell Note * - The average diameter of grain granules from 10 measurements

Claims (3)

1. A method of processing a radioactive ion-exchange resin, comprising heat treatment of an ion-exchange resin in a heated apparatus at a temperature that provides the decomposition of only functionally active ion-exchange groups of the ion-exchange resin without decomposition of the resin base, and curing the undecomposed organic base of the ion-exchange resin, characterized in that the resin is heat treated in a high-temperature hydrophilic coolant, which is used as glycols or used cooling and hydraulic resources cal glycol-based fluid, and as the hardeners is ethylene glycol or elaborate resources cooling and hydraulic fluids at its base with the addition of phthalic anhydride. 2. The method according to claim 1, characterized in that the heat treatment of the radioactive resins is carried out at a temperature of 101-230 ° C. 3. The method according to claim 1, characterized in that the ratio of hardener components is from 1.0 to 2.3 g of phthalic anhydride per 1.0 g of ethylene glycol in terms of anhydrous components.