RU2149685C1 - Method of countercurrent regeneration of ionites - Google Patents

Abstract

FIELD: water treatment. SUBSTANCE: invention relates to ion-exchange filter- assisted treatment of natural and waste waters as well as liquid solutions for application in power engineering, metallurgy, chemical and other industries utilizing in their operations desalted or softened water. UPCORE-type ionites are regenerated in a process including stage in which ionite bed is held down by upward directed liquid medium current. Holding-down process is accomplished in pulse mode, where water is supplied at least between two pulses. Amplitude of the first one is not lower than the height of free space zone over ionite bed at the end of working cycle and amplitude of the next pulse is not inferior to the amplitude of reflected wave arising after decay of preceding pulse. Inter- pulse period does not exceed time required for passage of reflected wave from preceding pulse through ionite bed. EFFECT: achieved more complete removal of pollutions from ionite bed allowing more efficient regeneration of ionite, in which regeneration time is reduced by 5-7% depending on nature and service time of ionite and water consumption is reduced by 10-12%. 3 cl, 4 dwg, 2 tbl

Description

 The invention relates to methods for purifying natural and wastewater, as well as other liquid solutions using ion-exchange filters, and in particular to methods for regenerating ion-exchange resins (IP), and can be used in energy, metallurgy, chemical and other industries using desalted or softened water in technological processes.

 There is a method of countercurrent regeneration of spent IS, including treatment with a regeneration solution and loosening from bottom to top, and washing with water from top to bottom (US Pat. RF N 2058817, 1995, class C 02 P 1/42).

 The disadvantage of this method is the low efficiency of the regeneration process due to the high consumption of regeneration solutions and water consumption for own needs, as well as the increased time of the resin regeneration process.

 The prototype of the proposed method is a method of regeneration of ion exchangers in filtration processes of the UPCORE type, carried out in a filtration plant containing an ion-exchange resin (ion exchange resin) and chemically inert material (inert) under the conditions of the process (Engineering The UPCORE System, Engineering Handbook, Trademark of The Dow Chemical Company, may 1995, Al page 5.6, B2 page 21).

 The method consists in the fact that at the end of the filtration work cycle, operations are carried out with a piston-like lifting and clamping of the ion exchanger layer with an upward flow of water, after which a regenerating solution (regenerant) is supplied in a bottom-up direction with a flow rate ensuring that the ion exchanger layer is kept in a clamped state, then displacing the regenerant residues with an upward flow of water without decompression of the clamped layer of ion exchanger, after which they allow the resin layer to settle under the influence of gravity and wash with water in the direction coincident flow direction of the treated water in the duty cycle. This ensures the degree of clamping of the ion exchanger layer in the range from 90% to 92%, which requires a flow of water with a linear speed of up to 50 m / h for at least 3-5 minutes, and for the regeneration of the resin regenerant is fed for up to one hour with a linear a flow rate of up to 20 m / h to maintain the resin layer in a clamped state.

The main disadvantages of the prototype are:
the impossibility of optimal resin regeneration due to incomplete clamping of the layer (up to 10% of the volume of the resin layer in the lower part of the apparatus remains uncompressed);
significant water consumption for clamping the layer and washing it, especially in the case of a high concentration of suspensions in the treated water.

 The problem solved by the authors was the development of a method for the regeneration of ion-exchange resins in processes of the UPCORE type, which makes it possible to more efficiently remove impurities from the system, including IS adsorbed on granules, as well as to reduce the regeneration time and reduce the amount of demineralized water used.

 It has been suggested that particle regeneration processes can be dramatically enhanced by exposing the particles successively to elevated pressure and “rarefaction” to create micropulsations on the surface of the ion exchanger grains. To solve this problem, the authors proposed to expose the ion exchanger layer during the regeneration to at least two successive pulses, the mode of which was selected so that the ion exchanger layer was first clamped by two opposing waves, and its grain surface was subjected to increased pressure, and then after the passage of the wave high pressure particles sorbed on the grains were subjected to "post-wave rarefaction". At the same time, the degree of “post-wave rarefaction” should be selected so that with the most complete decantation of contaminants, loosening of the clamped layer is excluded.

 As a result of the interaction of opposing waves in the zone of the clamped ion exchanger, a so-called “standing wave” is formed, which draws particles located on the periphery of the layer to its center and thereby increases the degree of clamping of the ion exchanger granules. As shown by experiments, as a result of this treatment, the ion exchanger layer is able to remain in a clamped state for up to 5 minutes without backwater flow.

 During the experiments, the possible and optimal process parameters were established and a significant improvement in the results of the regeneration of ion-exchange resins was confirmed in comparison with the UPCORE technology.

 In particular, it was found that the problem is solved by using the proposed method if, at the stage of clamping of the ion exchange resin, an ion exchanger layer is applied by supplying water with at least two pulses, and the amplitude of the first pulse is not less than the height of the free space above with an ion exchanger layer at the end of the working cycle, and the amplitude of each subsequent pulse is not less than the amplitude of the reflected wave that occurs after the passage of the previous pulse, and the time between pulses no more than the time required for passage of the reflected wave from the preceding pulse through the resin bed.

 The duration of the first pulse in industrial plants is from 0.1 to 60 seconds, and the time between pulses from 0.1 to 300 seconds. The amplitude of the pulse is set by the combination of the pulse duration and the magnitude of the overpressure. Typically, the pressure when creating a pulse is at least 0.01 MPa. The upper limit is determined by the design of the installation. A specific choice of parameters is carried out depending on the features of the installation used, the type of ion exchanger and the viscosity of the liquid being cleaned.

 Impulses are created, as a rule, due to the creation of hydraulic pressure, although their formation is possible due to pneumatic, mechanical or other, including complex effects.

 The inventive method can be used on almost any type of ion-exchange resins when placed in the upper layer of inert material, however, better results are achieved when using DOWEX resins such as weakly acid cation exchanger MAC-3, strongly acid cation exchanger: Marathon C, UPCORE Mono C- 600, Monosphere 650 C, weakly basic anion exchangers Marathon WBA, UPCORE Mono WB-500, strongly basic anion exchangers Marathon A, Marathon 11, Marathon A2, UPCORE Mono A-625, UPCORE Mono A-500, Monosphere 550 A and others. To achieve optimal results, it is recommended to use DOWEX UPCORE IF-62 as an inert material.

 The inventive method of exposure to ion exchangers can be implemented at other stages of the process. In particular, in the course of the experiments it was found that when applying a regenerating solution of sulfuric acid in the inventive mode, it is possible to reduce the likelihood or eliminate the occurrence of the process of gypsum plating of cation exchangers.

 Through the use of the proposed method, it is possible to achieve that the resin layer is compacted by almost 100%, and the water consumption for the operation of clamping the layer is reduced by at least 2 times. Additional advantages are that there is no need to install an additional pump of higher power, used for piston-like lifting and clamping of the resin layer, and in the case of reconstruction of a direct-flow circuit into a counter-flow one, the replacement of pipelines and re-equipment is eliminated.

 The regeneration process is as follows. An ion exchange resin and an inert material are loaded into a water purification filtration unit.

 The general process diagram is shown in FIG. 1-4, where figure 1 shows the duty cycle of filtering; in FIG. 2 - stage of clamping of the ion exchanger layer, supply of reagents and their displacement; in FIG. 3 - stage deposition; in FIG. 4 - stage washing system.

In this case, the following notation is introduced in the drawings:
1 - upper switchgear (ASU);
2 - a layer of floating inert;
3 - free space;
4 - layer of ion exchanger;
5 - lower switchgear (NRU).

 During the working cycle (Fig. 1), the purified water enters the filter from above, passing sequentially through the ASU 1, inert 2, free space 3, the layer of ion exchanger 4, the ASU 5, and then it is removed from the filter. Upon depletion of the exchange capacity of the resin layer (completion of the working cycle), the flow of the treated liquid into the ion-exchange filter is stopped in the direction from top to bottom and the regeneration process is started (Fig. 2). In this case, the ion exchanger layer is pressed against the switchgear 5, and the free space zone 3 is located in the apparatus above the ion exchanger layer 4.

 When carrying out the process of regeneration of the ion exchanger (Fig. 2) in the direction from bottom to top in a pulsed mode, a stream of water is supplied, which raises the entire layer of ion exchanger 4 without intralayer mixing, pressing it to inert 2 or ASU 1, while simultaneously allowing the suspension to be removed from the ion exchanger layer and from the filter accumulated during the working cycle.

 Then, in the direction from bottom to top, a flow of a regenerating solution is supplied, which, passing through the layer of ion exchanger 4, carries out its chemical regeneration, keeping the layer of ion exchanger 4 in a clamped state. The supply of the regenerating solution is carried out in continuous or pulsed mode.

 Upon completion of the regeneration, the operation of displacing the remnants of the regenerating solution from the clamped layer of ion exchanger is carried out, supplying a stream of water in the direction from the bottom up. The flow of water to the displacement can also be supplied in continuous or pulsed mode.

 At the next stage, the deposition operation is carried out (Fig. 3), for which the flow of process flows to the ion-exchange apparatus is turned off, and the ion exchanger layer 4 under the influence of gravity laminarly (uniformly, without intralayer mixing) settles on the NRU 5. In this case, the free space zone 3 migrates from switchgear 5 to switchgear 1 or inert 2.

 The last operation is the washing (figure 4), carried out in the same direction as the treatment of the source water in the work cycle.

 To implement the proposed method, it is preferable to use DOWEX UPCORE brand ICs, for example, strongly acidic Mono C 600 cation exchanger, strongly basic Mono A-625 anion exchanger, weakly basic Mono WB-500 anion exchanger and others. This is due to the fact that the resins of these grades have a uniform particle size distribution and high physical and mechanical characteristics, which improves the hydrodynamic parameters of the resin regeneration process. As an inert material, better results are achieved when using the inert DOWEX UPCORE IF-62.

 Industrial tests were carried out on the basis of a filtration plant with a capacity of 0.5 cubic meters, where 0.45 cubic meters were loaded. m resin type DOWEX UPCORE Mono C 600, based on a styrene-divinylbenzene matrix in sodium form with a total exchange capacity of the resin of at least 2.2 g - equiv./l and 0.02 cubic meters. m inert material DOWEX UPCORE IF-62.

 After depletion of the exchange capacity of the resin layer (completion of the working cycle), the flow of treated water into the ion-exchange filter was stopped from top to bottom and the regeneration process was started. For this, part of the purified water was supplied under the resin layer in the direction from the bottom up in a wide range of time and pressure. A fixed time after the cessation of the supply of the first pulse, a second pulse was applied (varying its parameters in different series of tests), and in a number of experiments, a third pulse. The degree of clamping of the layer was controlled visually.

 Then, the water supply was stopped and a regenerating solution based on sodium chloride or sulfuric acid was supplied in accordance with the instructions attached to the resin upon delivery.

 Upon completion of the chemical regeneration of the layer, the remnants of the regenerating solution were displaced by the flow of demineralized water supplied from the bottom up. Then, the water supply was stopped, as a result of which gravitational deposition of the resin layer occurred. The settled resin layer was washed with a stream of treated water from top to bottom, simultaneously clamping it, after which the next working cycle of water purification was carried out.

 The obtained test results, reflecting the influence of process parameters on the efficiency of water treatment, are given in table 1.

 The experiments carried out on a typical chemical water treatment plant that previously used UPCORE technology (with an average productivity of 150 cubic meters per hour and a filter cycle volume of 1000 cubic meters), when replacing the regeneration system with the claimed modified one, showed the possibility of achieving an improved filter cycle without compromising the quality of the treated water. (The experimental results are given in table.2).

 As follows from the above examples, the use of the claimed method provides the possibility of more complete removal of contaminants from the IP layer and, accordingly, a higher efficiency of the process of its regeneration. The time spent on regeneration is reduced by an average of 5-7%, depending on the nature of the IC, the life of the ion exchanger and the nature of the pollution. The cost of water for own needs is reduced by 10-12%.

Claims (3)

 1. The method of regeneration of ion exchangers in filtration processes of the type "UPCORE", which includes the stage of clamping the layer of ion exchange resin with a liquid flow directed from the bottom up, the stage of regeneration, gravitational deposition and washing of ion exchangers from the remnants of the regenerating solution, characterized in that the clamping process is carried out in a pulsed mode, supplying water with at least two pulses, and the amplitude of the first pulse is not less than the height of the free space zone above the ion exchanger layer at the end of the working cycle, and the amplitude follows The output pulse is not less than the amplitude of the reflected wave arising after the passage of the previous pulse, and the time between pulses is not more than the time required for the reflected wave from the previous pulse to pass through the ion exchanger layer.  2. The method according to claim 1, characterized in that the first pulse is fed with a duration of from 0.1 to 60 s.  3. The method according to claim 1, characterized in that the subsequent pulses are served with an interval of time between pulses from 0.1 to 300 s.

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