RU2206520C1 - Method of cleaning water to remove dissolved and undissolved impurities - Google Patents

Abstract

FIELD: water treatment. SUBSTANCE: initial water, designed for use in power engineering, chemical, food, and other industries, is passed into countercurrent filter in top-down direction through floating inert material bed and charge consisting of ionite bed and overlaying filter bed, in particular inert polymer with density above 1 g/cu.cm but less than density of utilized ionite and having granulometric composition from 0.5 to 2.5 mm. Charge is periodically regenerated involving preliminarily lifting it to be pressed against floating inert material bed followed by introduction of regenerating solution in bottom-up direction through charge and floating bed. Entrapped impurities are further removed from regenerating solution by passing it through supplementary filter and ionite beds. EFFECT: increased productivity of cleaning operation performed in one apparatus. 2 cl, 2 dwg

Description

 The invention relates to methods for purifying natural and waste waters and aqueous solutions by physicochemical methods using ion exchangers and can be used in energy, chemical, food and other industries.

 A known method of purifying water from undissolved impurities by passing it through a two-layer filter. Crushed anthracite or expanded clay granules are used as the material for the upper filter layers, quartz sand, magnetic iron ore, magnesite are used as the lower layers. The washing of two-layer filters is carried out by an upward flow of water with the expansion of the filter layers (1).

 The specified method provides water purification only from undissolved impurities for its clarification and discoloration. If the technology requires further purification, for example, softening or desalting of water, additional ion-exchange filters must be installed. In addition, the washing process of the filter layers is carried out with the expansion of the filter materials, which contributes to their removal from the filter along with the wash water and clogging of the filter switchgear.

 A known method of purifying water from dissolved and undissolved impurities, carried out in a filter with a central vertical distribution device, in which only part of the processed fluid is passed through a layer of filter material and then an ion load layer. Moreover, the liquid passes through the ion load in the radial direction (2).

 The disadvantage of this method is the complexity of its implementation, due to the rather complex design of the filter.

 Closest to the proposed method is a method of water purification, comprising sequentially passing purified water in a downward direction through a floating layer of inert material, a filter layer that traps undissolved impurities and consisting of an ion-exchange material, and an ion-exchange layer. Then, periodic regeneration is carried out by preliminary lifting and pressing the filter and ion-exchange layers to the layer of floating inert material and the subsequent supply of the regeneration solution through all layers in an upward flow. In this case, the ionite filter layer during cleaning and regeneration is preliminarily displaced from the central chamber of the filter into the free space above the main ion exchanger layer (3).

 The disadvantages of this method are the complexity and low economic efficiency when treating water with a high amount of undissolved impurities. This is explained by the fact that the entire filter load consists of the same material, the top layer of which in the working state acts as a filter layer, retaining undissolved impurities not caught on the mechanical filter. At higher concentrations of undissolved impurities, the use of an expensive ion-exchange material as a filter layer is economically disadvantageous. In addition, in the process, mixing of an ion-exchange resin of a uniform composition and size is possible, which leads to contamination of the ion-exchange material throughout the volume, reducing its service life.

 The objective of the invention is to provide a fairly simple and cost-effective water purification from dissolved and undissolved impurities in one apparatus in countercurrent technology. In this case, it is possible to exclude preliminary water purification from undissolved impurities in a mechanical filter, which allows to reduce the number of equipment and communications and, accordingly, reduce production areas.

 Since the inert material used in the filter layer has a particle size distribution in the range of 0.5-2.5 mm, which is larger than the particle size distribution of an ion exchanger, for example KU-2-8 cation exchanger, whose grain sizes are 0.3-1, 2 mm, there is a decrease in the pressure drop in the filter during the duty cycle and its performance is increased by 20-30%. The filtering granular material located on the layer of the ion exchanger allows you to protect it from contamination with suspended solids, iron oxides and other undissolved impurities and thereby increase the life of the ion exchanger.

The problem is achieved in that in the method for purifying water from dissolved and undissolved impurities, the purified water is successively passed from top to bottom through a floating layer of inert material, a filter layer that retains undissolved impurities, and an ion-exchange layer and periodic regeneration by preliminary lifting and pressing the filter and ion-exchange layers to a layer of floating inert material and an upward flow of regeneration solution through all layers in countercurrent. At the same time, a granular inert polymer placed directly on the ion-exchange layer having a density greater than 1 g / cm ³ but lower than the density of the ion exchanger used and a particle size distribution of 0.5-2.5 mm are used as a filter layer. In addition, the height of the filter layer is made up of 5-50% of the height of the ion exchange layer.

 In figure 1. shows a diagram of the process in the operating mode of water treatment. In figure 2. a diagram of the implementation of the process in the mode of regeneration of the load.

 The counter-current filter 1 contains a nozzle 2 for supplying the treated water and withdrawing the spent regeneration solution, an upper distribution device 3 connected to the nozzle 2, a nozzle 4 for discharging the purified water and supplying the regenerating solution, a lower distributing device 5 connected to the nozzle 4, a floating inert layer material 6 and the load containing the ion exchange layer 7 and the filter layer 8 located directly on it. Between the layer of floating inert material 6 and the filter layer 8 is vobodnoe space 9 (Figure 1). In the regeneration mode of the load (figure 2), a free space 9 is placed between the ion-exchange layer 7 and the lower distribution device 5.

 The method is as follows.

 During the working cycle of water purification, the treated water is fed to the counter-current filter 1 through the nozzle 2 and the upper distribution device 3. The water passes in a downward flow sequentially floating layer of inert material 6, the filter layer 8 and the ion-exchange layer 7. The purified water is discharged through the lower distribution device 5 and fitting 4. In this case, insoluble impurities (suspended solids, iron oxides, etc.) are retained from the treated water in the filtering layer 8, and dissolved ones are retained in the ion-exchange layer 7 RIMES (corresponding ions). Non-mixing of the loading layers is ensured by a significant difference in the grain densities of the filter material and the ion exchanger.

 After completion of the working cycle, the regeneration process is carried out (Fig. 2) in order to restore the exchange capacity of the ion exchanger and to clean the undissolved impurities of the filter material. To do this, through the nozzle 4 and the lower switchgear 5, an upward flow of water is preliminarily supplied for the piston-like lifting and pressing of the ion exchange layer 7 and the filter layer 8 to the layer of floating inert material 6.

 During the operation of pressing the loading layers to a floating inert material, due to the active hydrodynamics of the water supply stream, suspended solids and other undissolved impurities trapped by the filter material during the working cycle are carried away from the filter layer. Floating inert material freely passes a sealing or regeneration stream, undissolved impurities and delays whole grain loading. Next, through the nozzle 4 serves regeneration solution in the direction from the bottom up with the flow rate, ensuring that the layers 7 and 8 are kept in a clamped state, to the floating layer 6. Water is withdrawn for lifting and pressing the layers, as well as the spent regeneration solution from the counterflow filter 1 through the upper distribution device 3 and fitting 2.

EXAMPLE
A strongly acidic KU-2-8 grade cation exchange resin in a sodium form with a particle size distribution of 0.3-1.2 mm, with a density of 1.25-1.28 g / cm ³ and in an amount of 1700 is loaded into a countercurrent sodium cation exchange filter with a diameter of 1000 mm l As the filter material, a granular copolymer of styrene and divinylbenzene with a particle size distribution of 0.8-2.0 and with a density of 1.05 g / cm ³ located on a layer of cation exchange resin is used. The height of the filter layer is 400 mm. As an inert material of the floating layer, low-pressure polyethylene with a particle size distribution of 2-5 mm and a density of 0.95 g / cm ³ , the lower layer of which is 100 mm below the upper switchgear, is used. Between a layer of floating inert material and a filter layer there is a free space 100 mm high. The treated water with a suspended matter content of 7-8 mg / l and a total hardness of 4.5 mEq / l is passed at a speed of 20 m / h in a top-down direction sequentially through a layer of floating inert material, a filter layer and a layer of cation exchanger. At the outlet of the countercurrent sodium-cation exchange filter, the purified water had a suspended matter content of less than 0.5 mg / L and a total hardness of not more than 0.005 mEq / L. When the increase in the breakthrough of hardness salts in purified water exceeds 0.03 mEq / l, the countercurrent filter is switched off for regeneration. To this end, water is preliminarily fed into the filter from the bottom up with a flow velocity of not more than 50 m / h with the aim of a piston-like rise of the cation exchanger layer and the filter layer to the floating layer of inert material, and then in the same ascending direction, 8-10% sodium chloride solution with a flow rate that ensures the preservation of layers of cation exchange resin and filter material in the clamped state.

 In this case, during the regeneration, the exchange capacity of the cation exchanger is restored to the sodium form and at the same time, the removal of undissolved impurities from the filter material (styrene-divinylbenzene copolymer) is ensured.

The countercurrent filter can also be loaded instead of cation exchange resin with anion exchange resin, for example, anion exchange resin AB-17-8 in hydroxide form, having a grain size of 0.3-1.2 mm and a density of 1.1 g / cm ³ . In this case, the removal of insoluble impurities from the treated water (layer of styrene-divinylbenzene copolymer) and dissolved impurities - anions (layer of anion exchange resin) is ensured. Moreover, during countercurrent regeneration, a 4% sodium hydroxide solution is used.

 Thus, the use of this method of water purification allows combining in one device the removal of undissolved impurities from the treated water using all the advantages of countercurrent regeneration of ion exchange resin and filter material.

Sources of information
1. V.A. Klyachko, M.E. Apeltsin, Purification of natural waters, Moscow, Stroyizdat, 1971, p.231-236.

 2. Pat. RF 1319367, publ. 07/23/90, class At 01 D 24/00.

 3. Pat. RF 2121873, publ. 11/20/98, B 01 J 47/02, B 01 D 15/04, C 02 F 1/42.

Claims (2)

1. A method of purifying water from dissolved and insoluble impurities, comprising sequentially passing purified water in a downward direction through a floating layer of inert material, a filter layer that retains undissolved impurities, and an ion-exchange layer and periodic regeneration by preliminary lifting and pressing the filter and ion-exchange layers to the layer floating inert material and the supply of the regeneration solution through all layers countercurrent, characterized in that as the filter layer using gr a canceled inert material placed directly on the ion-exchange layer, having a density greater than 1 g / cm ³ but less than the density of the ion exchanger used and the particle size distribution of 0.5-2.5 mm.  2. The method according to claim 1, characterized in that the height of the filter layer is made up of 5-50% of the height of the ion exchange layer.

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