RU2496720C2 - Water treatment method and system - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: group of inventions relates to a water treatment method and system and can be used for industrial production of water which free of heavy impurities and has melt water properties. The water treatment method involves cooling water until a portion of the water containing heavy isotopes turns into ice; discharging the unfrozen water for further complete freezing thereof and thawing to obtain melt water, melting the ice remaining after discharging in the same container. Cooling is carried out in at least two steps, at each of which the water is cooled while stirring constantly until 10-20% of the water, with respect to its initial volume, turns into ice. Unfrozen water from the previous step is fed into each next step and melted ice is returned to the previous step, while adding it to the cooled water. The melted ice from the first step, having the highest content of heavy isotopes, is discharged into a storage container for further use. The water treatment system includes at least two linked containers with cooling and heating means. The first container is fitted with a heavy water drain line and the last is fitted with a purified water drain line. The containers are in form of overlapping basins which provides access to atmospheric air, fitted with means of moving water and connected in series by unfrozen water drain lines and melted ice return lines. The purified water drain line of the last container is connected to an apparatus for producing melt water, having a freezing means and an ice storage.

EFFECT: high quality of purifying water from heavy isotopes regardless of the volume of the purified water.

9 cl, 3 dwg

Description

FIELD OF THE INVENTION

The invention relates to the field of water treatment by freezing and is intended for the industrial production of water purified from heavy impurities and with the properties of melt water.

State of the art

A known method of water purification (see patent RU 2282596, IPC: C02F 9/08, C02F 1/22, publ. 08/27/2006), including primary freezing until 4-5 wt.% Water in the solid phase, which is removed , and the remaining part of the water is frozen, subjecting to hydrodynamic cavitation and removing the central part in an amount of 4-5 wt.%.

A known method of water purification (see patent RU 2400433, IPC: C02F 1/22, publ. 09/27/2010), comprising cooling the water in the freezing chamber until it is completely frozen, transferring the formed ice to the thawing chamber and gradually thawing it through filtering melt water through thermostatic filter.

A known method of water purification, including the complete freezing of water in a vessel and the gradual thawing of water in an inverted vessel, involves the freezing of heavy water on the walls of the vessel and its separation as initially thawed from the vessel walls into a separate container (see patent RU 2404131, IPC: C02F 1 / 22, published on November 20, 2010).

A known method of purifying water by freezing it (patent RU 2142914, IPC: C02F 1/22, publ. 20,12.1999), including cooling the tank with water to a freezing temperature to obtain a layer of pure ice along the contour of the tank in a volume of 25-50% of the initial volume of water and a layer of deuterium ice with a thickness of 0.5-4 mm on both end surfaces, pouring out the residual brine and thawing clean ice.

Each of the above methods allows the purification of water from the so-called "heavy" water containing heavy isotopes of hydrogen and oxygen, of which the most famous are deuterium and tritium, and which, as established by numerous studies, have an adverse effect on living organisms, including human organism. However, all of the above methods have limited application for small volumes of water, because suggest the removal of the initially formed deuterium ice, its transfer to another container and other operations that cannot be carried out in conditions of large volumes.

Known methods of water purification used in industrial water supply, based on freezing water by sprinkling (spraying) in an atmosphere with negative air temperature to form an ice mass, and obtaining purified water as a result of subsequent melting of this mass (see patent RU 2178389, IPC: C02F 1/22, published on January 20, 2002, and also patent SU 1838244, IPC: C02F 1/22, published on 08.30.1993). However, these methods provide water purification only from brines and mechanical impurities, and do not allow water purification from the so-called. heavy water.

A known method of water purification (see patent RU 2274607, IPC: C02F 1/22, publ. 04/20/2006), including freezing water in a closed container with ice formation ≈70% of the total volume of water, draining unfrozen brine with impurities, and thawing ice, which is carried out in two stages: first, 93-95% of the total volume of ice is thawed, removing melt clean water through a fine filter, and then the remaining ice containing heavy isotopes is thawed and removed in a separate container. To melt water more completely from heavy isotopes, melt water is subjected to short-term freezing to obtain 3-7% of ice from the volume of water, which is also removed. However, the complete freezing of water at the first stage makes it economically impractical to use this method for the purification of large volumes of water.

As the closest analogue to the proposed method, the method of purification of drinking water, which takes place during operation of the installation according to the invention patent RU 2128144, IPC: C02F 1/22, C02F 9/00, publ. 03/27/1999, the Method includes cooling the water until the ice part of the water containing heavy isotopes, draining unfrozen, purified from "heavy" water for its subsequent complete freezing and thawing to obtain melt water, and melting the remaining ice in the same tank with its subsequent removal on a separate line.

The disadvantage of this method is the inability to provide high quality water purification with large volumes of used containers. A single freezing of water allows removing only about 4% of heavy isotopes from water.

A device for water purification is known, including a water tank with a conical bottom, a drain for water and freezing and heating means associated with the control unit, a tank for collecting purified water and a tank for collecting water with impurities and a high deuterium content (see patent for Utility model RU 83068, IPC: C02F 1/22, publ. 05.20.2009).

A device is known for purifying water by freezing it, including a water tank having a removable lid and a bottom, equipped with freezing and heating means and made with recesses on the internal surfaces for freezing ice in them (see patent for invention RU 2058262, IPC: C02F 1 / 22, published on 04/20/1996).

However, both of the above devices are for domestic use.

Known industrial desalination plant designed for water purification by freezing using natural climatic factors (see patent for invention RU 2255902, IPC: C02F 1/22, publ. 10.07.2005). The installation includes a storage tank for purified water, a storage tank for purified desalinated water, pumping stations with inlet pressure pipelines, an ice platform with an anti-filter screen, protective shafts, shut-off drains and water outlets, winter sprinklers for freezing the ice massif, a channel system for collecting brines and desalinated water, control measuring complex, power plant and device for heating air and its supply to the collector. The mentioned installation provides the purification of water from brines, however, it cannot be used to purify water from heavy hydrogen isotopes.

As the closest, according to the purpose and the presence of similar structural features, analogue for the claimed device, an installation for drinking water treatment has been adopted (see patent for invention RU 2128144, IPC: C02F 1/22, C02F 9/00, published on 03/27/1999 .). The installation contains at least two containers connected to each other with cooling and heating means, the first of which is equipped with a heavy water drain line, and the last with a purified water drain line. Water is cooled in the first tank until part of the water containing heavy isotopes enters the ice. Non-frozen water is poured into the second tank, where it is completely frozen and then melted to obtain melt water. Ice with a high content of heavy isotopes remaining in the first tank is melted and removed separately. The installation allows you to get free of heavy water drinking water with the properties of melt water, however, it is also designed for small volumes and use at home.

Disclosure of invention

The problem to which the claimed invention is directed is to develop a method and system of purification that allows water to be purified from the heavy isotopes contained in it on an industrial scale and with appropriate quality, including through the use of natural climatic factors.

One positive technical result achieved by the implementation of the claimed invention is to improve the quality of water purification from heavy isotopes, regardless of the volume of purified water.

Another positive result is the possibility of obtaining heavy water with a high concentration of heavy isotopes, which allows it to be used for industrial purposes.

The above problem is solved and the technical results are achieved due to the fact that in the method of water purification, which includes cooling the water before moving part of the water containing heavy isotopes into ice, draining the unfrozen water for its subsequent freezing and thawing to obtain melt water, and melting the ice, remaining after draining, in the same tank, according to the claimed invention, the cooling is carried out in at least two stages, at each of which the water is cooled with constant stirring until 10-20% of water passes into ice t of its initial volume, while for each subsequent stage unfrozen water is supplied from the previous stage, and the melted ice is returned to the previous stage, adding it to the cooled water, the melted ice from the first stage, which has the highest content of heavy isotopes, is removed to the accumulator for the subsequent use.

The aforementioned problem is also solved by the proposed water purification system, comprising at least two interconnected containers with cooling and heating means, of which the first container is equipped with a heavy water drain line, and the last one with a purified water drain line.

New in the proposed cleaning system is the implementation of water tanks in the form of swimming pools with an overlap that provides access to atmospheric air, equipped with water mixing means and successively communicated between each other by drain lines of unfrozen water and return lines of melted ice, while the drain line of purified water of the last tank is connected with a plant for producing melt water, including means of freezing ice and ice storage.

Improving the quality of water purification, with large volumes of the latter, is achieved due to the multi-stage purification carried out sequentially at several stages similar to each other. At each subsequent stage, water is already partially purified from heavy isotopes and the actions similar to those carried out in the previous stage are repeated. As a result, the degree of water purification increases with each subsequent stage.

The ice remaining in the tank after draining the purified water, having a high content of heavy isotopes, is melted and returned to the previous purification stage, which allows obtaining raw materials for the extraction of "concentrated" heavy water. So, during the usual single-stage cleaning, the concentration of heavy isotopes in the removed ice is low, 4-5%. In the claimed solution, the water subjected to purification in the first stage, as a result of the return of melted ice from the previous stage, has a much higher concentration of heavy isotopes. As a result, heavy water released in the form of ice is also characterized by an increased concentration of heavy isotopes. It is such heavy water that can be used for industrial purposes, in particular, in nuclear energy.

Thus, the claimed method not only improves the quality of water purification as an output product, but also to obtain an additional output product - "concentrated" heavy water, which is a "waste" purification product, which is not achieved by other known methods of water purification.

At each stage, the mixing of water is carried out, which helps to equalize the temperature throughout the volume of the tank and ensure conditions for the release of heavy water into the solid phase evenly throughout the volume.

The optimal number of stages is 3 ÷ 5 and is determined by the required degree of purification.

For the implementation of multi-stage cleaning, the proposed system contains consistently placed homogeneous elements - pools for cooling water, equipped with means of mixing, heating and cooling and interconnected by a system of inlet and outlet pipelines.

In order to be able to use natural climatic conditions when freezing water, the design of the pools requires a light overlap that can be removed, opening up access to cold atmospheric air (in winter). However, the possibility of forced cooling is not excluded.

Melting of ice is possible both in natural conditions, for example, when closing a movable ceiling of a pool and stopping access to cold atmospheric air, or using forced heating.

Purified from heavy isotopes, light water is sent to complete freezing for the subsequent receipt of melt water from it. To completely freeze purified water, sprinklers are used, for example, well-known winter sprinklers. An ice mass is formed in the ice storage, which has, preferably a pyramidal shape.

The inclination of the walls of such an ice storage contributes to a good perception of heat and its heat transfer to ice. The pyramidal shape of the storage, with the walls expanding downward, provides the possibility of a natural and gradual lowering of the mass of ice.

The angle of inclination of the side faces (walls) of the ice storage to its base is preferably 70.5 ° ± 0.5 °. The choice of the mentioned angle of inclination is due to the fact that the ice crystallites are spatial polyhedral figures with an angle between the faces of 70.5 °. The latter is explained by the shape of the unit cell of water, which is a tetrahedron containing five water molecules H ₂ O linked by hydrogen bonds. Moreover, each of the water molecules in simple tetrahedra retains the ability to form hydrogen bonds, due to which simple tetrahedra can be joined together by vertices , edges or faces, forming a variety of spatial shapes, the base of which is a hexagonal (hexagonal) structure, when six water molecules (tetrahedrons) are combined into tso (materials enz. Wikipedia). This type of structure is characteristic of ice, snow and melt water, and a characteristic angle between the faces is an angle of 70.5 °.

Due to the fact that the inclination of the walls of the pyramid at 70.5 ° to the horizon corresponds to the corner of the ice mountain during melting, the ice melts in such an ice storage with the formation of a uniform air gap between the ice and the wall, which contributes to the passage of the melting process without collapse of the ice mass. Melt water, moving from top to bottom, always falls on un-melted ice and is forced to move between its particles, with multiple separation and separation of water: heavy water molecules freeze to ice particles, and light water molecules are washed out of ice. As a result, additional light water comes to the base of the pyramid, and heavy water is concentrated in the ice.

At a larger angle, the ice collapses and the air gap becomes clogged. As a result, melt water descends along the wall and, due to the porosity of the latter, penetrates outward and evaporates, cooling the wall. All this lengthens the thawing time and contributes to the formation of efflorescence on the wall.

When the angle of inclination is less than 70 °, the volume and height of the ice mass decreases, as a result of which the path of melt water through the ice decreases and the efficiency of its separation (separation) into heavy and light water decreases.

Overlapping the pool can be made of two hemispheres, one of which is installed stationary, and the other with the possibility of rotation by half a turn with entry under the first hemisphere.

To enable forced heating (and cooling), the pools are equipped with a system of pipes mounted in the walls and bottom of the pool. Pipes, depending on the need, are either supplied with warm water, preferably waste water from power plants or geothermal sources, or refrigerant. The heavy water discharge line from the first basin is connected to the heavy water storage device.

Brief Description of the Drawings

The invention is illustrated by drawings, where

figure 1 - technological scheme of the proposed water purification system;

figure 2 - pool for cooling water, General view;

figure 3 is a view a from figure 2;

figure 4 - presents a table of the results of laboratory tests of water samples.

The implementation of the invention

The water purification system (see figure 1) contains a cascade 1 from the pools (B ₁ -B _n ) and installation 2 for receiving melt water.

Pools (B ₁ -B _n ) are sequentially interconnected by lines 3 of discharge of unfrozen water and lines 4 of return of heavy water (melted ice), in which storage tanks 5 for heavy water can be installed.

The first pool B ₁ in the sequential cascade has a heavy water discharge line 6 connected to the heavy water storage device 7. The last pool B _{n is} connected by a non-frozen water discharge line 3 with a unit 2 for receiving melt water, including sprinklers 8 and a pyramidal ice storage 9, with angle a of the inclination of the side faces to the base, comprising about 70.5 °.

Pools (B ₁ -B _n ) for cooling water are made (see Fig.2-3) in the form of structures of the same type 10 with a movable ceiling formed of two hemispheres 11 and 12, one of which is installed stationary, and the other with the possibility of displacement (turn) half a turn under the first, which provides access to atmospheric air into the interior of the pool. Each pool is equipped with a mixing device 13 and means of forced heating and cooling (not shown). The means of forced heating and cooling can be made in the form of pipes mounted in the bottom and walls of the pool to supply coolant or refrigerant. It is also possible to use electric heaters.

To determine the most optimal and economically feasible period of water cooling, laboratory studies of water samples taken at different stages of freezing were carried out, the research results are shown in the table (figure 4).

For laboratory studies, the following samples were presented: sample No. 1 - ordinary tap water (without purification), sample No. 2 - water after a single freeze with the formation of 6% ice, sample No. 3 - water after a single freeze with the formation of 10% ice, sample No. 4 - water after a single freeze with the formation of 15% ice, sample No. 5 - water after a single freeze and the formation of 20% ice, sample No. 6 - water after a single freeze and the formation of 25% ice, sample No. 7 - melted ice obtained upon transition 15% of water in ice.

Laboratory studies of water samples were carried out by the method of isotopic analysis of oxygen and hydrogen in water (δ ¹⁸ O and δD) in the laboratory of stable isotopes. The preparation of water samples was carried out by the standard method of high-temperature pyrolysis of water on carbon. To determine the ¹⁸ O / ¹⁶ O and D / H isotopic ratios in water samples, a TC / EA high-temperature converter (ThermoQuest, Bremen, Germany) connected to a MAT 253 isotope mass spectrometer (ThermoQuest, Bremen, Germany) operating in continuous flow mode was used helium.

The measurement results of δD and δ ¹⁸ O are given in relation to the international standard VSMOW. The error in determining δD and δ ¹⁸ O (2σ) was 0.8 ^o / _oo and 0.2 ^o / _oo (n = 5), respectively.

As can be seen from the table, the results of laboratory tests of the water remaining after 6% of the water left in the ice (sample No. 2) do not significantly differ from the results of the analysis of simple tap water (sample No. 1).

When passing to ice 25% of the initial volume of water (sample No. 6), a significant improvement in the quality of water treatment does not occur compared to the sample where ice was 20%, which makes the cost of electricity for cooling water unreasonable, economically impractical, t. to. they do not bring significant results.

The best results of water purification from heavy isotopes show samples No. 3, No. 4 and No. 5.

Thus, when 10-20% of the water is transferred to ice from its original volume, the largest transition to heavy isotopes of ice occurs, which is valid for any stage of water purification. Only the numerical expression of the percentage of the selected heavy fraction differs, which decreases with each subsequent stage.

The method of water purification is as follows.

Fill the pool B ₁ with water from the storage pond 14, open the overlap of the pool, turning the hemisphere 12, to provide access to cold atmospheric air. Cool the water to t = 0 + 3 ° C and maintain at the mentioned temperature, carrying out constant stirring. In the process of such exposure, a part of the water passes into the ice, characterized by a high content of heavy isotopes having a freezing temperature of about + 3.8 ° C.

When the volume of ice is about 10-20% of the initial volume of water in the pool, the unfrozen, “lightened” water is drained into pool B ₂ .

Monitoring and measuring the amount of water passing into the ice is carried out by monitoring the total volume of water in the tank. It is known that when frozen, 100 volumes of water give 109 volumes of ice, i.e. the volume of water increases by 9% upon transition to ice. Thus, when 10% of water goes into ice, the total volume will increase by 0.9%, and when 15% and 20% of water goes into ice, the volume will increase by 1.35% and 1.8%, respectively.

The walls of the tank are rigid and the change in volume will only affect the water level - the height of the tank. Knowing the initial filling height of the tank, one can determine by the method of simple mathematical calculations that, for example, with an initial filling height of 3 m, when 15% of the water goes into ice, its level in the tank will rise by 40.5 mm. The increase in water level in the tank is determined by a level sensor (not shown in the drawings).

After draining the purified water, the remaining ice in the B ₁ basin with a high content of heavy isotopes is melted: either due to natural warming, when closing the movable ceiling of the pool and stopping the access of atmospheric air, or due to forced heating of the pool by supplying coolant through pipes. The heavy water resulting from melting ice is poured into the reservoir 7 along line 6 of the heavy water discharge.

The water is re-cooled in pool B ₂ , and the sequence of operations is similar to the actions carried out in the first pool. Non-frozen water from pool B _{2 is} sent to the next stage, and melted ice, which is water with a high content of heavy isotopes, is returned to the previous stage - to pool B ₁ , along with a new portion of the water poured into it. As a result, the concentration of heavy water in the formed ice increases at this stage.

After each freezing, the concentration of heavy isotopes in water decreases. Thus, there is a multi-stage purification of water from heavy water, which allows to achieve its high-quality purification.

Non-frozen purified water from the last stage of treatment (basin B _n ) is sent to installation 2, where light water is frozen in any known manner, for example, by arranging a high fountain using known Grad installations (in winter), or in molds. The resulting ice is stored in the ice storage 9.

To obtain melt water, ice is thawed in the ice storage 9 at t about 0 + 1 ° C, preferably using natural climatic factors. However, the possibility of using forced heating is not ruled out.

The pyramidal shape of the ice storage and the angle of inclination of its walls contributes to a good perception of natural heat and its heat transfer to the ice mass, which gradually falls under the influence of this heat. In this case, an air gap is formed between the wall and ice, which allows air convection. Warm air rises to the top of the pyramid, warming up first of all the top of the ice massif, due to which the ice melts from above. Melt water, moving from top to bottom, falls on un-melted ice, moving between its particles. During this movement, heavy water molecules freeze to ice particles, and light water molecules are washed out of ice.

As a result, an additional lightweight clean melt water comes to the base of the pyramid, which is removed from the process for subsequent use, and heavy water is concentrated in the ice. The last non-melted ice in the ice storage, about 2-5%, has a higher concentration of heavy isotopic form, i.e. contains an increased amount of heavy isotopes. Therefore, the last ice is melted, removing the resulting heavy water in a separate tank and then into the reservoir 7 of heavy water.

Placing the heating elements at the base of the ice storage pyramid allows you to accelerate the process of melting and removal of the mentioned ice.

The heavy water accumulated in the accumulator 7 with an increased concentration of heavy isotopes is sent for further processing and industrial use.

Claims (10)

1. A method of water purification, including cooling the water before the ice part of the water containing heavy isotopes, draining unfrozen water for its subsequent complete freezing and thawing to obtain melt water and melting the ice remaining after draining in the same tank, characterized in that cooling is carried out in at least two stages, at each of which the water is cooled with constant stirring until 10-20% of the initial volume of water passes into ice, while non-frozen water from the previous hundred is supplied to each subsequent stage diium, and the melted ice is returned to the previous stage, adding it to the cooled water, the melted ice from the first stage, having the highest content of heavy isotopes, is removed to the accumulator for subsequent use. 2. The method according to claim 1, characterized in that the water is cooled in reservoirs such as pools by means of cold atmospheric air. 3. The method according to claim 1, characterized in that the ice is melted using forced heating. 4. The method according to claim 1, characterized in that the complete freezing of the purified water is carried out by sprinkling with the formation of an ice mass in a pyramidal ice storage. 5. A water purification system containing at least two containers connected to each other with cooling and heating means, of which the first tank is equipped with a heavy water drain line, and the last is a purified water drain line, characterized in that the tanks are made in the form of pools with overlap providing access to atmospheric air, equipped with means of mixing water and sequentially communicated between each other by drain lines of unfrozen water and return lines of melted ice, while the discharge line purified in last rows capacitance connected with installation for melt water, comprising means freezing ice and ice storage. 6. The system according to claim 5, characterized in that the ice storage is made in a pyramidal shape with an angle of inclination of the side faces to the base of 70.5 ° ± 0.5 °. 7. The system according to claim 5, characterized in that the means of freezing ice are made in the form of winter sprinkling apparatus. 8. The system according to claim 5, characterized in that the heavy water discharge line from the first basin is connected to the heavy water storage device. 9. The system according to claim 5, characterized in that the overlap of the pool is made of two hemispheres, one of which is installed stationary, and the other with the possibility of rotation by half a turn with entry under the first hemisphere. 10. The system according to claim 5, characterized in that the means for cooling and heating the pools are made in the form of pipes mounted on the walls and bottom of the pool through which the refrigerant or coolant is supplied.

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