WO2014058407A1

WO2014058407A1 - Method for treating aqueous solutions with electro-erosion coagulation

Info

Publication number: WO2014058407A1
Application number: PCT/UA2012/000107
Authority: WO
Inventors: Николай Константинович МОНАСТЫРЕВ; Леонид Николаевич ЗИМА
Original assignee: Monastyrov Mykola Konstantinovich; Zima Leonid Nikolaevich
Priority date: 2012-10-10
Filing date: 2012-12-03
Publication date: 2014-04-17
Also published as: UA76821U

Abstract

The invention relates to facilities for the complex treatment of industrial waste water and rainwater run-off, and also processing water from atomic power plants, with the aim of decontaminating said water from radionuclides. The method comprises filling a discharge chamber with an aqueous solution to be treated, placing a layer of metallic granules into the discharge chamber cavity, subjecting the layer of granules to electric pulses via electrodes, which are connected to corresponding outputs of a pulse generator, and gradually destroying the granules under the action of spark discharges therebetween until coagulants and water of the required purity are produced. The layer of metallic granules is produced from granules manufactured from steel and aluminium or alloys thereof, the steel granules and steel electrodes make up approximately 20-25% of the total volume of metals in the aqueous solution to be treated, and said solution is fed into the discharge chamber cavity in a continuous-flow mode with pressure from below, producing a "pseudo-boiling" layer of granules, the granules being subjected to square-wave electric pulses with a relative pulse duration of 75-85 microseconds and an amplitude of 300-800 volts.

Description

The method of purification of aqueous solutions by electroerosive coagulation.

The present invention relates to means for the integrated treatment of industrial and rainwater, as well as the process water of nuclear power plants for the purpose of their decontamination, mainly from radionuclides - cesium-137 (137Cs), strontium-90 (90Sr), americium-241 (241At).

The decontamination of radionuclides that accumulate in the upper layer of the earth and during rainfall turn into rainwater and also concentrate in the technological waters of nuclear power plants is an important task, the solution of which will improve the quality of agricultural products, improve the environment and improve the health of the population.

One of the methods of decontamination is sorption processes using inorganic sorbents and organic ion-exchange materials, but their use in large volumes is hindered by the high cost, and in some cases, the complexity of the processes of their manufacture.

Taking into account the contamination of large areas with radionuclides of cesium-137 (137Cs), strontium-90 (90Sr) and americium-241 (241At), the proposed solution is relevant and reasonable.

A known method of water purification in order to obtain drinking water, including the operation of preliminary purification of the source water from harmful and toxic substances, cooling the water and then removing heavy hydrogen isotopes from the water — deuterium and radioactive tritium — in the water stream by selective solid condensation of these heavy isotopes into two stages: at the first stage - on the surface of a solid body - evaporator, cooled below 0 ° С, washed by leaving water, and then at the second stage - on the surface of single layers of condensate - ice, which They constantly form, while the surface temperature each layer is maintained at the level originally established by the evaporator temperature, after obtaining the necessary ice crystallization process thickness stopped and removed the heavy isotopes of oxygen O _d and O-is, then carry the light water sampling with a reduced content of heavy isotopes of hydrogen and oxygen is carried out defrosting and condensate drain activation of the obtained water by optimizing its mineral composition and structure [Declaration Patent of Ukraine Ns 51330 A for Invention, IPC 7 C02F9 / 00, Publ. 11/15/2002. Bull. Ns 1 1/2002].

The disadvantage of the described method lies in its complexity and high cost of the obtained product - purified water, which significantly limits its use for purification, in particular, industrial and rainwater from radionuclides - cesium-137 (137Cs), strontium-90 (90Sr), americium- 241 (241 At).

Closest to the proposed one by the number of essential features is a method of purifying aqueous solutions by electroerosive coagulation, which includes the operation of passing an aqueous solution through a layer of metal granules that are located in the discharge chamber, and exposing them to electric pulses until the granules gradually disintegrate under the influence of spark discharges and the formation of coagulants [Scherba A.A., Zakharchenko S.N. Application of the method of electroerosive coagulation. / In the journal "Water and Water Purification Technologies" - Ns 4, December 2002; p. 27-29]. In accordance with the described method, the granules are placed in the discharge chamber and periodically act on them with short - up to 200 μs and powerful - up to 500 kW pulses.

The disadvantage of the described method is the need to use powerful pulses, and therefore a powerful installation, which is not always economically feasible and affordable.

The proposed utility model is based on the task of creating such a method for the purification of aqueous electroerosive solutions coagulation in order to deactivate them, mainly from radioactive compounds of cesium, strontium and americium, which would be more economical, and therefore more accessible.

The problem is solved in the proposed method by creating conditions for the selective sorption of cesium, strontium and americium compounds by their coagulation with aluminum and iron hydroxides, which are formed by electroerosive dispersion of aluminum and steel granules in an aqueous medium.

The proposed, as well as the known method of purification of aqueous solutions by electroerosive coagulation, includes filling the discharge chamber with a purified aqueous solution, placing a layer of metal granules in the cavity of the discharge chamber, applying electric pulses to the layer of granules through electrodes that connect to the corresponding outputs of the pulse generator, and gradually destroying the granules under the action of spark discharges between them until the formation of coagulants and water of the required purity, and, according to the invention, a layer of metal gr the anul is created from granules made of steel and aluminum or its alloys, steel granules and steel electrodes make up approximately 20-25% of the total volume of metals in the purified aqueous solution, and this solution is fed into the cavity of the discharge chamber in a flow mode with a pressure from below, creating "Pseudo-boiling" layer of granules, which are affected by rectangular electric pulses with a duty cycle of 75-85 microseconds and an amplitude of 300-800 volts.

The authors experimentally found that the optimal material for the layer of metal granules, which is most able to coagulate the radionuclides of cesium-137 (137Cs), strontium-90 (90Sr) and americium-241 (241At), is a mixture of steel granules, for example, from Art. З and aluminum or its alloys, for example, АМЦС. The initial diameter (size) of each granule is 8-10 mm. AT As granules can be used and crushed metal chips of these metals of the same size.

The aqueous solution is fed into the dispersion zone under pressure from below, through a perforated grating of dielectric material, so that the layer of aluminum and steel granules is in a "pseudo-boiling" state. In this case, the intensity of the contacting of the granules with each other and with the electrodes significantly increases, and, as a result, the number of electrical contacts between them per unit time per unit volume of the aqueous solution that is subjected to purification increases, which leads to an increase in the release of the amorphous phase of metal hydroxides (coagulants), ozone, OH- radicals, which intensifies the passage of chemical reactions to create water-insoluble complex compounds, which include radionuclides of cesium-137 (137Cs), strontium-90 (90Sr), ame ricium-241 (241At) - selective sorption of compounds of cesium, strontium and americium.

The ratio of the volume of granules in each case is chosen experimentally - depending on the contamination of the solution that needs to be cleaned. In this case, steel granules (or shavings) comprise approximately 20 - 25% of the total volume of metals in the discharge chamber. To ensure a constant flow of the dispersion process, the electrodes in the reactor (cathode and anode) are made of carbon steel, for example, grade St. 3. Thus, the dispersible layer of metal granules consists of several metals - iron, aluminum or its compounds, or alloys based on aluminum. The presence of carbon steel in the discharge chamber not only contributes to the creation of coagulants, but also softens the hydrodynamic load on the body of the discharge chamber. Moreover, iron hydroxide compounds in which iron has a valency of +2, +3, +4 (based on FeO, Fe ₂ O ₃ , Fe ₃ O ₄ oxides) formed during the electroerosion of steel electrodes and steel granules or shavings have a high coagulation level in relation to heavy ions metals such as strontium-90 (90Sr). Aluminum hydroxide / A1 (OH) ₃ /, which is formed as a result of electroerosion of aluminum granules or shavings, has a high level of coagulation with respect to cesium-137 (137Cs) and americium-241 (241 Am) ions.

Table 1 shows the data confirming the optimal volume of carbon steel granules and electrodes in the total volume of metals in the cavity of the discharge chamber when using rectangular pulses with a duty cycle of 75 μs and an amplitude of 500 V for the purification of aqueous solutions of radionuclides - cesium - 137 (137Cs), strontium -90 (90Sr) and americium-241 (241At), which is 20-25%:

Table 1

In addition, the precipitate, which does not dissolve and consists of coagulants, also containing AI (OH) ₃ , FeO, Fe ₂ O ₃ , Fe ₃ O ₄ , has a reduced magnetic susceptibility. This allows you to remotely and quickly manipulate the coagulant during technological operations (its compaction, removal from the sedimentator, etc.).

The authors also experimentally established that while passing rectangular current pulses with an amplitude of 300-800 V through a layer of granules in an aqueous solution of radionuclides - cesium-137 _Example _mmetin> -

(137Cs), strontium-90 (90Sr), americium-241 (241 Am), which are in the purified solution in the dissolved state, the granules are destroyed, and the ions of the mentioned radioactive isotopes are sorbed on aluminum and iron hydroxides and turn into an insoluble state in the form of complex compounds . When using sawtooth or arcuate pulses, the processes of sorption and coagulant creation are slower, which leads to a delay of the process. Therefore, the series of short rectangular pulses with a duty cycle of 75-85 μs and an amplitude of 300-800 V were determined optimal.

Table 2 shows the data that confirm the fact that the optimal effect on the granule layer is rectangular pulses with a duty cycle of 75-85 μs and an amplitude of 300-800 V, provided that the volume of granules and electrodes made of carbon steel is stable in the total volume of metals in the discharge camera - 23%:

table 2

Boreness Amplitude Cleaning time Cleaning time rectangular-rectangular-1 m ³ technolo- 1 m ³ technolo-

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of impulse impulsive effluents from the water of ice, in ice, in the foundry nuclear

<υ micro- Volt power plant production-

ϊ

about kundas (Azovstal, otsii (Zaporizhzhya-Mariupol); Skye AES);

about

X in hours in hours

1 60 500 3.8 3.6

2 75 500 2,5 2,5

3 80 500 2.5 2.2

85 500 2.5 2.2

5 100 500 3.0 3.5

75,260 3.0 3.2 7 75 300 2.6 2.5

8 75 800 2.4 2.2

9 75 1000 3.0 3.2

Figure 1 schematically shows the installation for the purification of aqueous solutions by electroerosive coagulation, which carried out the proposed method.

Installation for cleaning aqueous solutions by electroerosive coagulation contains a discharge chamber 1 of a dielectric material. A horizontal mesh partition 2 of dielectric material is installed in the cavity of the discharge chamber 1, on which granules of carbon steel (for example, grade 3) and aluminum or an aluminum alloy (for example, grade AMC) with a diameter of 8-10 mm are placed in a uniform layer 3. Two vertical steel electrodes 4 of different polarity pass through the partition 2. The volume of steel granules and electrodes 4 located in the solution to be cleaned is 20 - 25% of the total volume of metals in the cavity of the discharge chamber 1. Each electrode 4 has the shape of a rectangular parallelepiped, the larger edge of which is located vertically, and is connected to the corresponding output of the pulse generator - anode or cathode / not shown /. In the lower part of the discharge chamber 1. a nozzle 5 is installed for supplying a cleaned solution under pressure in the flow chamber 1 to the cavity of the chamber 1 with a pressure from below to create a "pseudo-boiling" layer of granules, which is created using the corresponding pump (not shown). In the lower part of the cavity of the chamber 1, under the mesh partition 2, a sedimentation tray 6 is horizontally located - for the extraction of coagulated sediment from the chamber 1, which is formed during electroerosive coagulation. In the upper part of the chamber 1, a fitting with a valve 7 is installed, designed to control the drain rate of the solution to be purified and its subsequent re-supply in flow mode through the nozzle 5 into the cavity of the chamber 1. At the top chamber 1, a valve 8 is installed, designed to supply new granules into the cavity of the discharge chamber 1. The installation is equipped with a control unit, the corresponding inputs of which are connected to temperature sensors, the level of the aqueous solution and the degree of its purification, and the corresponding outputs are connected to the pump and to the pulse generator \ are not shown \. The control unit is designed to maintain the stability of the set parameters of a series of rectangular electric pulses and to record data regarding the purity of the solution passing through the valve 7 at the outlet of the chamber 1. The control unit is designed as a control computer with appropriate software.

Example 1. In the cavity made of dielectric material of the discharge chamber 1, in which a horizontal mesh partition 2 of dielectric material is installed, granules of carbon steel grade St were loaded. 3 and aluminum alloy AMtsS brand with a diameter of 8 - 10 mm. The granules were placed in a uniform layer 3 on a horizontal mesh partition 2 so that the solution to be cleaned — process effluents — completely covered the layer 3 of granules during operation of the unit for cleaning aqueous solutions. Two vertical steel electrodes 4 of different polarity, located at a distance of 200 - 250 millimeters in the cavity of chamber 1, passed through the partition 2. The volume of steel granules and electrodes 4 was approximately 25% of the total volume of metals in the cleaned solution in the cavity of the discharge chamber 1. Each electrode 4 had the shape of a rectangular parallelepiped and was connected to the output of a pulse generator of the corresponding polarity. Technological drains were supplied from the bottom to the top through the nozzle 5 into the discharge chamber 1 with the aim of their decontamination, mainly from radionuclides - cesium-137 (137Cs), strontium-90 (90Sr), americium-241 (241At). Rectangular pulses with a duty cycle of 75 μs and an amplitude of 600 V were applied to the electrodes 4. During the transmission of pulses between the individual granules and electrodes 4 sparks occurred. During discharges in a layer of 3 granules in a liquid, hydroxides A1 (OH) s and iron, oxides FeO, RegОз, Fe ₃ 0 ₄ were synthesized, which sorbed cesium, strontium, americium and heavy metal ions dissolved in technological effluents . Namely, there was selective sorption of cesium, strontium and americium compounds by their coagulation with aluminum hydroxides, iron oxides and hydroxides, which were formed during electroerosive dispersion of layer 3 from aluminum and steel granules in an aqueous medium. Due to the creation of a “pseudo-boiling” layer 3 of aluminum and steel granules, the contact intensity of both the granules with each other and the granules with electrodes 4 increased significantly, and, as a result, the number of electrical contacts between them per unit time increased. This significantly increased the performance of the synthesis process of complex compounds based on AI (OH) ₃ , FeO, Fe ₂ O ₃ , Fe ₃ O ₄ coagulant hydroxides, which were insoluble or slightly soluble in water, and the release of ozone and OH-radicals intensified the process chemical reactions. The solution, which was subjected to purification, was fed into the discharge chamber 1 in a flow mode with a pressure from below through the nozzle 5 to create a "pseudo-boiling" layer 3 of granules. In this case, the solution through the nozzle with a valve 7 in the upper part of the chamber 1 flowed out of the chamber 1 and entered the pump chamber / not shown /, from which the pump again fed the solution into the cavity of the chamber 1 for re-cleaning through the nozzle 5. During operation, the degree of cleaning was monitored solution. As the granules of layer 3 are destroyed in the discharge chamber 1, new batches of metal granules are loaded through the valve 8 to maintain a ratio of 25% of the volume of steel granules and electrodes 4 in the solution to be cleaned to the total volume of metals in the discharge chamber 1. After obtaining an aqueous solution of the required degree cleaning it was poured through the fitting with a valve 7 from the cavity of the discharge chamber 1 into the receiving tank / not shown /, unloaded the coagulated sediment from tray 6 and fed under pressure through the nozzle 5 a new portion of the technological effluents for cleaning.

Example 2. Purification of rainwater was carried out in order to deactivate them mainly from radionuclides — cesium-137 (137Cs), strontium-90 (90Sr), americium-241 (241At). The same operations were performed as in example 1, but the volume of steel granules and electrodes 4 was approximately 20% of the total volume of metals in the discharge chamber 1. A series of rectangular pulses with a duty cycle of 80 μs and an amplitude of 300 V were applied to the electrodes 4.

As a result, aqueous solutions of the required degree of purification were obtained.

Compared with the prototype method, the proposed method turned out to be more economical, since equipment with an installed capacity of only 4 kW was used for its implementation, in contrast to 20-25 kW in the prototype, and in addition, the proposed method had greater productivity due to the use of layer 3 of granules of carbon steel and aluminum alloys that were in the cleaned solution in the cavity of the discharge chamber 1 in a "pseudo-boiling" state, by creating conditions for selective sorption of cesium, strontium and amer compounds it is coagulated by aluminum and iron hydroxides, which are formed by electroerosive dispersion of aluminum and steel granules in an aqueous medium by a series of rectangular pulses with optimal values of duty cycle and amplitude.

Claims

Claim.

The method of purification of aqueous solutions by electroerosive coagulation, including filling the discharge chamber with a purified aqueous solution, placing a layer of metal granules in the cavity of the discharge chamber, applying electric pulses to the layer of granules through electrodes, which are connected to the respective outputs of the pulse generator, and the granules are gradually destroyed by spark discharges between them to the formation of coagulants and water of necessary purity, characterized in that the layer of metal granules is created from granules, made made of steel and aluminum or its alloys, steel granules and steel electrodes make up approximately 20-25% of the total volume of metals in the purified aqueous solution, and this solution is fed into the cavity of the discharge chamber in a flow mode with a pressure from below, creating a "pseudo-boiling" layer of granules which are affected by rectangular electric pulses with a duty cycle of 75-85 microseconds and an amplitude of 300-800 volts.