LT6826B - Water desalination method and thus obtained product - Google Patents

Abstract

The technology is intended for desalination (demineralization) of water that is used for technological purposes. Technology in the desalination process does not produce waste that pollutes the environment. Desalinated water is used in industrial processes to protect the equipment from salt deposits or as a diluent in solutions, liquid products, to prevent additional impurities such as salts containing in the water. Technology is based on the principle of ionic exchange. Filtration of water through cationic and anionic charges (cations and anions) removes salts from the water, replacing them with H + and OH- ions. The cation exchanger is regenerated with concentrated nitric acid and the anion exchanger with aqueous ammonia solution. The composition of the regeneration product is close to that of complex mineral fertilizers, therefore, depending on the composition of the desalting water, it is applicable in the production of liquid or bulk complex mineral fertilizers.

Description

FIELD OF THE INVENTION

The invention relates to the desalination (demineralization) of water which is used for filling steam boilers or for other technological purposes, and more particularly to a method for desalination without the formation of waste and thus to a product.

State of the art

Desalinated water is used in industrial processes to protect equipment (steam, water heating boilers, turbines, etc.) from salt deposits or as a diluent for solutions, liquid products to avoid additional impurities - salts in the water. Water desalination technologies, by removing salts from water, create wastewater with a concentrated amount of salts. Today, in order to reduce environmental pollution, the norms of wastewater discharged into the environment regulate the concentrations of salts and individual chemical elements. As a result, industries face the problem of wastewater discharges, especially when there are no other wastewaters that could dilute the wastewater from the desalination process.

Conventional ion exchange technology is the filtration of water through an ion exchange resin. The water is filtered through a cation exchange charge and the cations are removed from the water (converted to H ion) in the water, then the water is filtered through an anion exchange charge and the anions (converted to OH ion) in the water are removed from the water. In this way, salts are removed from the water. When the ion exchange resins are depleted, they are regenerated. _{0.5-2.5% sulfuric acid (H 2} SO ₄ ) or 4-5% hydrochloric acid (HCl) is used for the regeneration of the cation exchange resin, 4-5% sodium hydroxide (NaOH) or potassium hydroxide is used for the regeneration of the anion exchange resin KOH (4-6%) (Purolite Engineering Manual-Puropack packed-Bed Technology, 1999).

_{Nitric acid (HNO 3} ) 46% can also be used for cation exchange regeneration.

In conventional ion exchange technologies, the amount of wastewater during regeneration is 5-15%, calculated from the amount of produced (desalinated) water. The mineralization of wastewater is usually obtained at 5-20 g / L, in addition, the wastewater is enriched with the reagents used in regeneration and the salts formed from them NaCl, NaSO ₄ , NaNO ₃ .

In reverse osmosis technology, two water streams are separated under high pressure - one is desalinated water, the other is concentrated water. The technology produces 25-15% of concentrated water (wastewater) and 75-85% of desalinated water. During reverse osmosis, the inlet water is concentrated 4-5 times, i. if the salinity of the raw water is 500 mg / L, then the salinity of the concentrate will be 2-2.5 g / L.

Both technologies produce a certain amount of wastewater with a correspondingly high salinity and create unwanted environmental pollution.

U.S. Pat. No. 3,956,115 discloses the peculiarities of the regeneration of ion exchange charges with concentrated HNO ₃ and NH ₄ solutions. This patent describes the regeneration of ionic charges enriched in only one type of ion - NH ₄ and NO ₃ , by cleaning condensates contaminated with ammonium nitrate ions, but does not describe the possibility of regenerating ionic charges enriched with Ca, Mg, Na, Cl, SO ₄ ions that are for desalination in the waters used.

The closest analog is disclosed in US5951874. The patent describes the possibilities of water reduction in ion exchange systems using surface water for treatment, but does not disclose whether the wastewater water reduction measures used are possible for regenerations with HNO ₃ and NH ₃ solutions. This patent discloses regenerations only with solutions of HCl, H ₂ SO ₄ , NaCl, NaOH.

The invention does not have the above-mentioned disadvantages associated with water desalination methods and includes additional advantages.

Brief description of the invention

This method is based on ion exchange i.e. filtering the water through an ion exchange charge to remove salt ions from the water and, after utilizing the charge susceptibility, regenerating it with higher concentration salt solutions, thereby restoring the original ionic susceptibility of the charge. Due to the recovery materials used, the resulting effluent composition and the small amount of effluent generated during charge regeneration, the resulting effluent / solution is used as a raw material in the production of mineral fertilizers. In this way, the method of desalination is waterless and waste-free.

Advantages of the method:

1. Regeneration of the cationic charge is performed with 30-50% HNO ₃ . Regeneration of the anionic charge is done with 15-25% NH3 solution.

2. The amount of wastewater during regeneration is 0.4-1%, calculated from the amount of water produced during the filter cycle. The salinity of the wastewater is 100180 g / L.

3. The effluents from the process are concentrated and have a composition that can be used as an ingredient in the production of complex mineral fertilizers.

4. This technology is wastewater-free and waste-free, as all wastewater is used as a raw material in the production of mineral fertilizers.

5. A 5-fold higher concentration (compared to a conventional regeneration system with non-concentrated reagents) is more cost-effective, as the use of wastewater as a raw material for dry fertilizer production significantly reduces water evaporation and significantly saves storage space as a liquid fertilizer. and transportation costs.

Using conventional technology, after obtaining 20 g / L of mineralization effluent and achieving a salinity of 150 g / L, the remaining water should be evaporated. Evaporation technology is expensive in terms of operation and investment, and environmentally harmful due to the high energy consumption.

Brief description of the drawings fig. a schematic of the water desalination system is shown.

Detailed description of the invention

It should be understood that many specific details are set forth in order to provide a complete and understandable description of an exemplary embodiment of the invention. However, it will be clear to a person skilled in the art that the detail of the examples of implementation of the invention does not limit the implementation of the invention, which can be implemented without such specific instructions. Well-known methods, procedures, and ingredients have not been described in detail to avoid misleading examples of the practice of the invention. Furthermore, this description should not be construed as limiting the examples of implementation provided, but only as their implementation.

Although examples of embodiments of the invention, or aspects thereof, as shown and described, include many components that are depicted to be in a particular common space or location, some components may be remote. It should also be understood that the examples provided are not limited to the components described and include other elements necessary for their operation and interaction with other components, the presence of which is self-evident and therefore not detailed.

Desalination of water used for filling steam boilers or other technological purposes involves the supply of treated water by pump P5. Valves V1, V13, V2 are open. The water passes through the cationic column C and the anionic column A, enters the tank T6 and pours. Other valves closed, pumps off. When the required amount of water has elapsed, regeneration is performed.

Regeneration of column C is performed:

_{fraction - HNO 3} solution is fed by pump P1, opening valves V3, V9. After passing the 4L solution (water is expelled from the ion exchange column and pipelines), V9 is closed, V12, V14 are opened.

fraction - when the required amount of regeneration solution is missed, P1 is switched off, the valves are closed. V5, V12, V14 are opened, demineralized water is pumped by pump P3 to expel the solution. The fraction is injected into tank T5.

fraction - closes V14, opens V19. The fraction is injected into tank T8. The valves close, the pump switches off.

From tank T8, pump P7 passes water through columns A through valves V18, V11, V10.

A concentrated solution of HNO ₃ is added to j j1 for subsequent regeneration.

Regeneration of column A is performed:

_{fraction - NH 4} solution is supplied by pump P4, opening valves V4, V11, V10. When 4L solution is missed (water is expelled from the ion exchange column and piping), V10 is closed, V14 is opened.

fraction - when the required amount of regeneration solution is missed, P4 is switched off, the valves are closed. V6, V11, V14 are opened, demineralized water is pumped by pump P3 to expel the solution. The fraction is injected into tank T5.

fraction - closes V14, opens V15, fraction is injected into T7.

From the T7 vessel, inject the appropriate amount of solution into the T4 vessel by diluting the additional concentrated NH ₄ until the regeneration solution is used for the next regeneration.

fraction - closes V15, opens V10. The fraction is added to T2.

Before starting the next cycle, recirculation is performed through tank T6, pumps P6, valves V7, V13, V2 open. The circulation is carried out until desalinated water of suitable quality is obtained.

After starting a new filtration cycle, pump P2 is switched on and the water of the first and fourth fractions from tank T2 is introduced into the incoming water flow of 3-4 L / h. speed.

The process (desalination of water) takes place by passing water through ion exchange charges, the water flowing from the bottom to the top. Water first flows through a charge of a strong acid cation exchange resin, then through a charge of a weakly basic anion exchange resin. Compressed bed technology is used (the filter is completely filled with ion exchange resin, leaving only free space to compensate for the expansion of ion exchange resins).

1. The desalination process shall take place according to the following formulas:

Cationic charge:

CaCl, MgCl, NaCl, CaSO ₄ , MgSO ₄ , NaSO ₄ , Ca (HCO ₃ ), Mg (HCO ₃ ), Na (HCO ₃ ), + RH R- (Ca, Mg, Na) + H (Cl, SO ₄ ) + CO ₂

Anion exchange charge:

H (CI, SO ₄ ) + CO ₂ + R-OH o R- (CI, SO ₄ , CO ₂ ) + H ₂ O

A cationic charge is used for the desalination process - strong acid cation exchange resin and weak base anion exchange resin.

2. The regeneration process shall follow the following formulas:

Cationic charge:

R- (Ca, Mg, Na) + HNO ₃ «RH + Ca (NO ₃ ) ₂ , Mg (NO ₃ ) ₂ , NaNO ₃

Anion exchange charge:

R- (CI, SO ₄ , CO ₂ ) + NH ₄ OH «R-OH + (NH ₄ ) ₂ SO ₄ , NH ₄ CI + NH ₄ CO ₂

Cationic charge regeneration process

Regeneration is performed in the opposite direction to the process - from top to bottom.

The cationic resin is regenerated with 30-50% concentration of nitric acid. After the solution is fed, the desalinated water is fed to expel the regenerating solution.

During regeneration, 3 wastewater fractions are separated:

Fraction 1 contains 2-10% of the total salts. This amount of water is returned to the beginning of the process.

Fraction 2 contains 85-95% of the total salts. This amount of effluent is mixed with the effluent of the second fraction of the anion exchange charge.

Fraction 3 contains 20-40% excess HNO3. This amount of wastewater is passed through the anionic charge. The water is returned to the beginning of the process after the anion exchange charge.

Anion exchange charge regeneration process

The anionic charge is regenerated with a 15-25% NH ₃ solution, followed by the addition of demineralized water to leach the solution. During regeneration, 4 wastewater fractions are separated:

Fraction 1 contains 2-10% of the total salts. This amount of water is returned to the beginning of the process.

Fraction 2 contains 82-96% of the total salts. This amount of effluent is mixed with the effluent of the second fraction of the cationic charge.

Fraction 3 contains a 25% excess of _{NH 3.} This solution is used to _{prepare the NH 3} solution for the next regeneration.

the fraction is returned to the beginning of the process.

Upon completion of the feed and expulsion of the regeneration solutions, water is recirculated by circulating the water through the cationic and anionic columns until a purified water quality of 15-25 pS / cm is achieved. After recirculation, the inlet water is supplied and a new desalination cycle is started.

The regeneration product is a 10-18% (100-180 g / L) solution. In terms of its composition, this solution is close to the nitrogen-based mineral fertilizer composition and can therefore be used as an ingredient in a raw material for the production of complex fertilizers or as a component of liquid complex fertilizers. The composition of the resulting product depends directly on the composition of the inlet water and is different for each water source. For this reason, the use of a regeneration product for each water source, the specifics of the company's (potential user of the technology) production, its use as a raw material for fertilizer production, or the use of liquid fertilizers in nearby markets are considered on a case-by-case basis. If deeper water desalination is required, mixed resin filtration technology or electrodeionization technology is used after the described technology. The preliminary composition of the regeneration product is given in the table.

table:

Product % NaNO ₃ 10-15 Mg (NO ₃ ) ₂ 5-10 Ca (NO ₃ ) ₂ 15-25 NH ₄ NO ₃ 20-30 nh ₄ hco ₃ 20-30 (NH ₄ ) ₂ SO ₄ 2-20 nh ₄ ci 2-20

Methods and materials

To verify the operation of the process, tests were performed. A water treatment station consisting of: cation exchange column, anion exchange column, chemically resistant pumps, containers for water, reagents and solutions was used for the tests.

All apparatus are connected by plastic pipes, resistant to the solutions used, fitted with appropriate fittings. The station is partially automated (level of automation - monitoring of critical parameters, automatic stopping when critical parameters are exceeded).

Test materials:

Strong acid cation exchange resin, amount 14 L

Specification:

Total capacity * Η-Form min. eq / L 1.7 Total capacity * Η-Form (dry) min. eq / kg 4.8 Uniformity factor * max. 1.5 Ball size *> 90% mm 0.4-1.25 Effective size * mm 0.5-0.6 Fineness <0.315 mm normal 0.5% < Mass density (+/- 5%) g / L 765 Average density in g / ml 1.15 Water conservation wt. % 50-55 Mean pore diameter in nm 33 Stability temperature range ° C -20-125 Product safety max. years 2 Storage temperature range ° C -20 - 40

Weak base anion exchange resin, amount - 12L

Specification:

Uniformity factor * max. 1.6 Ball size *> 90% mm 0.4-1.25 Effective size * mm 0.5 -0.6 Mass density (+/- 5%) g / L 640 Average density in g / ml 1.02 Water conservation wt. % 52-58 Total capacity * min. eq / L 1.6 Stability in the pH range 0-14 Product safety max. years 2 Stability temperature range ° C -20 - 40

Solutions used for filter regeneration:

HNO3 acid - 58%

Aqueous NH ₃ ammonia solution - 25%

Measuring instruments used for the tests:

a) Electrical conductivity meter (installed: Chemitec 30; portable: WTW 82362 Cond 330i)

b) pH meter (portable: Hach HQ40d)

c) thermometer installed at 0-60 ° C - 4 pcs.

d) rotameter (flow meter), installed 50-500 l / h - 4 pcs.

e) pulse meter for water quantity - 1 unit.

Example of implementation of the invention

In order to implement the invention, experiments have been performed, which are presented here as examples of the implementation of the technology.

The water is fed to a cation exchange column, then the water is fed to an anion exchange column. The flow of treated water is from the bottom up. The treated water is collected in a treated water tank and spilled during the process. Part of the desalinated water is used for the preparation of regenerative solutions and for the expulsion of regenerants during regeneration. Regenerative solutions are fed from top to bottom.

Inlet water:

Origin: municipal water

Temperature: 10-15 ° C

Conductivity: 530 -540 pS / cm

Inlet water analysis:

Eil. no. Components mg / L meq / L 1 Ca + Mg 84 5.0 2 Na + K 12 0.53 3 Total cations 5.53 4 hco ₃ 292.8 4.8 5 Cl 12 0.34 6 SO ₄ 40 0.39 7 Total anion content 5.53

Water flow: 250 L / h

Water pressure: 3 atm

Regeneration was performed under the following conditions:

Cation exchange regeneration Regeneration solution hno ₃ Concentration 50% Temperature 16 ° C Anion exchange regeneration Regeneration solution nh ₃ Concentration 15% Temperature 16 ° C

Results

The filter cycle (water content from regeneration to regeneration) is 2500 L (10 hours).

The quality of desalinated water is 10-15 pS / cm. Amount of regeneration product obtained: 13L.

The amount of regeneration product formed is 0.53% of the amount of water produced (2500 L)

The composition of the regeneration product obtained:

Product mg / L K 950 Na 1230 Mg 4560 Ca 11400 Ammoniacal nitrogen (N-NH ₄ ) 4071 Nitrate nitrogen (N-NO ₃ ) 33868 SO ₄ 7850 Cl 2552

A total of 14 purification cycles and 14 regenerations were performed. Data are from Experiment 6. The filter cycle remained stable throughout the cycles at 2500 L ± 15 L. This indicates that the ion exchange resin is efficient. The quality of desalinated water is stable. The composition of the regeneration product solution is suitable for the production of liquid or dry mineral complex fertilizers with microelements.

Although many features and advantages have been listed in the description of the invention, together with the structural details and features of the invention, the description is provided as an exemplary embodiment of the invention. Modifications may be made in the details, in particular in the shape, size and arrangement of the materials, without departing from the principles of the invention, in accordance with the most widely understood meanings of the terms used in the claims.

Claims (4)

DEFINITION OF THE INVENTION A process for desalination of water for the removal of salts from surface or deep water, comprising regenerating the cationic charge and recovering the anionic charge after passing the filtered water through a cationic charge filter and passing the filtered water through the anionic charge, characterized in that: a) the filter with cation exchange resin is regenerated with 30-50% nitric acid, b) The filter with anion exchange resin is regenerated with 15-25% ammonia water solution. The product obtained by the process according to claim 1 is a product of cationic and anionic regeneration comprising complexes from salts which were in water before the start of filtration and from a solution of nitrogen, nitric acid and ammoniacal water. The product of claim 2, wherein the product is a liquid complex mineral fertilizer. Use of a product according to claim 2 or 3 as a raw material for the production of liquid or bulk mineral complex fertilizers or for direct soil fertilization.