RU2296719C2 - Mineralized and sea water desalting and final softening system - Google Patents

Abstract

FIELD: power engineering; production of desalted water from mineralized and sea water.

SUBSTANCE: proposed system includes clarifying plant with clarified water line desalting membrane-type reverse osmosis plant with permeant line and condensate discharge line, as well as plant for proportioning the inhibitor solution before desalting reverse osmosis plant whose inlet is connected with counter-flow Na-cationite filters of clarified water and outlet is connected with Na-cationite filters of permeant; line discharging the concentrate from desalting reverse osmosis plant is connected to inlet of Na-cationite permeant filters and line discharging the used concentrate from these filters is connected to outlet of Na-cationite clarified water filters mounted before desalting reverse osmosis plant.

EFFECT: reduced hardness of desalted water; increased yield of permeant; reduced discharge of condensate; enhanced regenerating ability of desalting plant.

2 dwg

Description

The invention relates to the field of power engineering and can be used to produce demineralized water from mineralized and sea waters.

A known system of desalination of sea or ocean water, containing a series-included installation of preliminary preparation and a single-stage desalination installation of reverse osmosis (UOO) [1] - analogue. The disadvantage of this system is the low yield of permeate (35 ÷ 50% of the flow rate of the incoming water).

Known closest to the proposed invention for the intended purpose and the effect achieved is the desalination system of mineralized and sea or ocean waters, containing sequentially included clarification unit and desalination membrane UOE, as well as a unit for dosing a solution of scale inhibitor before UOE [2] - prototype.

The disadvantages of such a system are:

- a relatively low permeate yield (53% in the first stage and 94.5% in the second stage), a total of 50% of the initial flow rate for the installation;

- increased consumption of concentrate (purge water) - about 50% of the flow rate of the source water;

- high content of total hardness in the incoming water after preliminary treatment (L = 134.4 mEq / l), equivalent to its content in the source water (Ca - 451 mg / l or 22.5 mEq / l and Mg - 1342 mg / l or 111.8 mEq / l);

- low quality of permeate for scale-forming ions (Ca = 3.4 mg / l or 0.17 mg-equiv / l), that is, even two-stage UOE permeate does not meet the quality standards of the additional water in terms of hardness established for boilers of various parameters.

The achieved results of the invention in comparison with the prototype are a decrease in the hardness content in demineralized water, an increase in the permeate yield with a decrease in the concentrate discharge, as well as an increase in the regenerative ability of the UO concentrate due to an increase in the sodium content in it and a decrease in the content of hardness cations.

These results are ensured by the fact that in the desalination system of mineralized and sea or ocean waters, containing a sequentially connected clarification unit with a clarified water line and a desalination membrane UOE with permeate and concentrate removal lines, as well as a unit for dosing a scale inhibitor solution before UOE, according to the invention, to the inlet OOU countercurrent Na-cationite filters of clarified water are connected, and Na-cationite filters of permeate are connected to the outlet of OOE, with the concentrate discharge line from UOE connected to the inlet of Na-cation exchange filters of permeate, and the drainage line of spent concentrate from these filters is connected to the output of Na-cation exchange filters of clarified water installed in front of the DOE.

That is, the Na-cation exchange filters of permeate operate according to a parallel-flow pattern, and the Na-cation exchange filters of clarified water installed before the OOE operate according to a counter-flow pattern.

In the system according to the invention, the quality of the UO concentrate is characterized by a Na content of 1000 ÷ 1200 mEq / L and L = 13 ÷ 20 mEq / L. Due to this, the UO concentrate has sufficient regenerating ability with respect to Na-cation exchange filters of permeate and clarified water.

Figure 1 as one example of the implementation of the invention schematically shows a desalination system according to the invention with a single-stage DOE; figure 2 - the same system with a two-stage DOE.

The desalination system of mineralized and sea or ocean waters according to the invention comprises a clarification unit 1 connected in series with clarified water line 1.1, as well as a single-stage desalination membrane UOO 2 (FIG. 1) or two-stage (FIG. 2) with a first stage UO 2.1 and a second stage UO 2.2. Each stage of the DOE is equipped with a permeate (demineralized water) line 2.3 and a concentrate drain line 2.4, as well as a device (not shown) for dispensing a scaling inhibitor solution supplied through line 2.5 to the DOE. Countercurrent Na-cation exchange filters 3 of clarified water are connected to the entrance of UOO 2, and permeate Na-cation exchange filters 4 are connected to the output of UOO 2, the line 2.4 of concentrate discharge from UOO 2 is connected to the input of Na-cation exchange filters 4 of permeate, and the exhaust discharge line 4.1 concentrate from these filters is connected to the outlet of Na-cation exchange filters 3, clarified water installed in front of DOE 2. Line 5 serves to supply the source water for clarification, line 6 - to supply the finished deeply desalted water to the consumer.

The system according to the invention operates as follows. The source water through line 5 is supplied to clarification unit 1, then the clarified water supplied through line 1.1 is partially softened on Na-cation exchange filters 3 and enters UO 2. Permeate is collected in a tank (not shown) and fed to Na-cation exchange filters 4 The UOO 2 concentrate is also collected in a tank (not shown) and fed via line 2.4 to the regeneration of Na-cation exchange filters 4 installed on permeate line 2.3. The spent concentrate after these filters is collected in a container (not shown) and fed to the regeneration of Na-cation exchange filters 3 installed on the clarified water line 1.2 in front of the OOU 2. Ready demineralized water is supplied to the consumer through line 6.

Example 1. The water of the Caspian Sea after purification in clarification plant 1 is supplied to the softener on countercurrent Na-cation exchange filters 3 loaded with strongly acidic cation exchanger KU-2-8. Further, partially softened water with calcium hardness W = 0.7 mEq / L and with an inhibitor content of 3 mg / L is supplied for desalination in a single-stage UO2 (Fig. 1) equipped with Filmtec SW 30 HR-380 membrane elements. UOO 2 permeate with hardness L = 50 µg-eq / L is supplied for softening with Na-cation exchange filters 4. Residual permeate stiffness after Na-cation filters 4 Ж≤1 µg-equiv / L. The permeate yield is 80% of the feed water consumption. The concentrate UOO 2 with the content of Na = 1040 mEq / L and L = 13 mEq / L is fed to the regeneration of Na-cation exchange filters 4 installed on line 2.3 of the permeate. After these filters, the spent concentrate is fed to the regeneration of countercurrent Na-cation exchange filters 3 installed on the clarified water line 1.1 in front of DOE 2.

For a two-stage UOE 2 (Fig. 2), when operating on partially softened Caspian water, the rigidity of the permeate of the second stage 2.2 UOU 2 is L = 8 ÷ 10 μg-eq / L. Permeate with the indicated hardness is supplied for softening on Na-cation exchange filters 4. Residual permeate rigidity after Na-cation exchange filters 4 Ж≤1 μg-eq / L. The permeate yield in the first stage is 80%, in the second stage - 90%. The concentrate of the second stage 2.2 UOO 2 is fed into the line 1.1 of the source clarified water before UO 2. The concentrate of the first stage 2.1 UO 2 is fed to the regeneration of Na-cation exchange filters 4 installed on the permeate line 2.3. After these filters, the spent concentrate is fed to the regeneration of countercurrent Na-cation exchange filters 3 installed on the clarified water line 1.1 in front of DOE 2.

Example 2. Ocean water after purification in clarification unit 1 is supplied to the softener on countercurrent Na-cation exchange filters 3 loaded with strongly acidic cation exchange resin KU-2-8. Further, partially softened water with calcium hardness W = 1 mEq / L and with an inhibitor content of 4 mg / L is supplied for desalination to a single-stage UO 2 (Fig. 1) equipped with Filmtec SW 30 HR-380 membrane elements. UOO 2 permeate with hardness L = 100-130 µg-eq / L is supplied for softening with Na-cation exchange filters 4. Residual permeate stiffness after these filters is L≤1 µg-eq / l. The permeate yield is 60% of the feed water consumption. The concentrate UOO 2 with the content of Na = 1200 mEq / L and L = 20 mEq / l is fed to the regeneration of Na-cation exchange filters 4 installed on line 2.3 of the permeate. After these filters, the spent concentrate is fed to the regeneration of countercurrent Na-cation exchange filters 3 installed on the clarified water line 1.1 in front of DOE 2.

For a two-stage DOE 2 (figure 2) when working on partially softened ocean water, the rigidity of the permeate of the second stage 2.2 is W = 15-20 μg-eq / L. The permeate with the indicated hardness is fed to the softening on Na-cation exchange filters 4. The residual permeate hardness after these filters is W≤1 μg-eq / L. The permeate yield in the first stage is 60%, in the second stage - 90%. The concentrate of the second stage 2.2 UOO 2 is fed into the line 1.1 of the source clarified water before UO 2. The concentrate of the first stage 2.1 UO 2 is fed to the regeneration of Na-cation exchange filters 4 installed on the permeate line 2.3. After these filters, the spent concentrate is fed to the regeneration of countercurrent Na-cation exchange filters 3 installed on the clarified water line 1.1 in front of DOE 2.

Information sources

1. Higher Recovery with Improved Hollow Fiber Membrane Modules. - Atsuo Kumano and others.- Desalination & Water Reuse. - November / December 2003, vol. 13/3, p. 39.40.

2. Higher Recovery with Improved Hollow Fiber Membrane Modules. - Atsuo Kumano and others. - Desalination & Water Reuse. - November / December 2003, vol. 13/3, p.13-16.

Claims (1)

A desalination system for mineralized and sea or ocean waters, comprising a clarification unit in series with a clarified water line and a reverse osmosis desalination membrane unit (UOE) with permeate and concentrate removal lines, as well as a unit for dosing the scale inhibitor solution in front of the UOE, characterized in that to the input OOU countercurrent Na-cation exchange filters of clarified water are connected, and Na-cationite filters of permeate are connected to the OOU outlet, and the concentrate discharge line from OOU is connected to the input permeate Na-cation exchange filters, and the waste concentrate discharge line from these filters is connected to the outlet of clarified water Na-cation exchange filters installed in front of the COO.

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