Method for inhibiting calcium sulfate from scaling in evaporator

Abstract

The invention discloses a method for inhibiting calcium sulfate from scaling in an evaporator, and belongs to the technical field of anti-scaling treatment. The invention discloses a method for inhibiting calcium sulfate from scaling in an evaporator. The method comprises the following steps: preparing an ammonium ionic liquid additive; the method comprises the following steps: adding an NH4Cl solution into an ammonium ionic liquid additive, and uniformly mixing to obtain an ammonium ionic liquid + NH4Cl stock solution; the method comprises the following steps: adding CaSO4. 2H2O into a stock solution of ammonium ionic liquid and NH4Cl to prepare a mixed solution, uniformly mixing the mixed solution, carrying out centrifugal treatment on the mixed solution, and taking supernate to obtain a solution. By adopting the method for inhibiting the calcium sulfate from scaling in the evaporator, the problem that the evaporator is blocked due to the fact that the calcium sulfate is easy to scale in the ammonium chloride solution can be solved.

Description

Technical Field

[0001] The invention relates to the technical field of anti-scaling treatment, and in particular to a method for inhibiting scaling of calcium sulfate in an evaporator. Background Art

[0002] Calcium sulfate dihydrate (gypsum) is an inorganic salt with a wide range of applications. The effectiveness and ability of gypsum as a functional building material, mineral processing and contaminated soil restoration make gypsum an essential salt for commercial use. However, gypsum has a low solubility in aqueous environments and can easily precipitate and scale in pipes during industrial operations. Therefore, gypsum is one of the main causes of scale formation in reverse osmosis systems, seawater desalination, industrial water recycling and hydrometallurgical operations. In some production processes, scaling can cause serious problems such as hindering process flow, scaling of reverse osmosis membranes, thereby reducing performance and increasing costs.

[0003] In the separation and purification of ammonium chloride solution, the ammonium chloride solution contains calcium sulfate dihydrate, and the solubility of calcium sulfate dihydrate in the ammonium chloride solution is greatly affected by temperature. Especially in the evaporator, as the solution temperature increases, the solubility of calcium sulfate solution further decreases, causing calcium sulfate crystallization in the evaporator and scaling in the evaporator, affecting the normal use of the evaporator. Summary of the invention

[0004] The purpose of the invention is to provide a method for inhibiting scaling of calcium sulfate in an evaporator, so as to solve the problem that calcium sulfate is easy to scale in an ammonium chloride solution and cause evaporator blockage.

[0005] To achieve the above object, the present invention provides a method for inhibiting scaling of calcium sulfate in an evaporator, comprising the following steps: S1, preparing ammonium ionic liquid additives; S2, adding NH4Cl solution to the ammonium ionic liquid additive, mixing evenly, to obtain a stock solution of ammonium ionic liquid + NH4Cl; S3. Add CaSO4·2H2O to the stock solution of ammonium ionic liquid + NH4Cl to prepare a mixed solution, mix the mixed solution evenly, centrifuge the mixed solution, take the supernatant, and obtain a solution.

[0006] Preferably, in S1, the preparation method of the ammonium ionic liquid additive comprises: S11, placing an amine solution in a flask, adding an acid solution into the flask under an ice bath condition, and stirring and mixing the amine solution and the acid solution at room temperature to obtain a reaction solution; S12, drying the reaction solution in a rotary evaporator to obtain an ammonium ionic liquid additive; the ammonium ionic liquid additive after drying is stored in a vacuum dryer using phosphorus pentoxide as a desiccant.

[0007] Preferably, in S11, the molar ratio of the amine solution to the acid solution is 1:1, and the stirring time is 20h-30h.

[0008] Preferably, in S11, the amine solution is one of 2-hydroxyamine, di(2-hydroxy)amine, tri-(2-hydroxy)amine, hydroxymethylamine, hydroxyethylamine, hydroxypropylamine, hydroxypropylmethylamine, hydroxypropyldimethylamine, ethylamine, diethylamine, triethylamine, tripropylamine, tributylamine, tripentylamine, trihexylamine, trioctylamine, and didecyldimethylamine.

[0009] Preferably, the amine solution is 5.3 mol / L ethylamine or 11.33 mol / L hydroxyethylamine.

[0010] Preferably, the acidic solution is one of hydrochloric acid, lactic acid, 2-hydroxypropionic acid, acetic acid, propionic acid, butyric acid, salicylic acid, m-hydroxybenzoic acid, p-hydroxybenzoic acid, malonic acid, and succinic acid.

[0011] Preferably, the acidic solution is 11.3 mol / L lactic acid or 17.3 mol / L acetic acid.

[0012] Preferably, in S2, the mass concentration of the ammonium ionic liquid is 5%-15%; the molar concentration of the NH4Cl solution is 1 mol / kg-5.5 mol / kg.

[0013] Preferably, in S2, the mass ratio of the ammonium ionic liquid to the NH4Cl solution is 0.019-0.103; in order to obtain a better anti-scaling effect, the mass ratio of the ionic liquid to the NH4Cl solution is set to 100:4.7 Preferably, in S3, the mixed solution is shaken at 10 rpm-100 rpm and 20° C.-50° C. for 10 h-15 h for mixing; and centrifuged at 3500 rpm for 10 min.

[0014] The advantages and positive effects of the method for inhibiting the scaling of calcium sulfate in the evaporator described in the present invention are: after adding the ammonium ionic liquid additive to the NH4Cl solution, the present invention forms a CaSO4·2H2O + NH4Cl + H2O + ILs system, which can effectively improve the solubility of CaSO4·2H2O in the NH4Cl solution, inhibit the scaling of CaSO4·2H2O in the evaporator, protect the evaporator, and extend the service life of the evaporator. In addition, the ammonium ionic liquid additive does not corrode metals, is harmless to the human body, and does not produce hydrogen embrittlement, can be directly discharged, and is green and pollution-free.

[0015] The reaction mechanism of using ammonium ionic liquid additives to improve the solubility of CaSO4·2H2O is as follows: The solubility of calcium sulfate dihydrate is affected by the cation / anion of the ionic liquid. 2+ and SO4 2- The salt effect produced by the interaction is that when an ionic liquid that does not have the same ions as calcium sulfate dihydrate is added to a solution of weak electrolyte calcium sulfate dihydrate, the total ion concentration in the solution increases, and anions and cations with different electrical properties attract each other to form weak particles called ion atmospheres, which reduces the chances of anions and cations dissociated from calcium sulfate dihydrate to recombine to form molecules, thereby reducing the activity of calcium sulfate dihydrate, and further promoting the continued ionization of calcium sulfate dihydrate, thereby increasing the solubility of calcium sulfate dihydrate.

[0016] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is the solubility of calcium sulfate in a saturated ammonium chloride system in the presence of ethylammonium lactate ionic liquid of different concentrations according to the present invention. DETAILED DESCRIPTION

[0018] In this application, unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by technicians in the technical field of this application. In the event of any inconsistency, the meaning described in this specification or the meaning derived from the contents recorded in this specification shall prevail. In addition, the terms used herein are only for the purpose of describing the embodiments of the present application and are not intended to limit the present application. In order to accurately describe the technical content in this application and to accurately understand the present invention, the following explanations or definitions are given to the terms used in this specification before describing the specific embodiments: Embodiment 1 S1. preparing an ammonium ionic liquid additive.

[0019] Ethylamine was placed in a round-bottom flask, and lactic acid was added dropwise at a molar ratio of 1:1 under ice bath and constant stirring. After complete addition, the reaction mixture was stirred at room temperature for 24 hours to obtain ethylammonium lactate ionic liquid. The ethylammonium lactate ionic liquid was dried in a rotary evaporator and stored in a vacuum desiccator with phosphorus pentoxide as a desiccant.

[0020] S2. Add 3.0 mol / kg NH4Cl solution to 5% ethylammonium lactate ionic liquid aqueous solution, mix well, and obtain a stock solution of ethylammonium lactate ionic liquid + saturated NH4Cl.

[0021] S3. Add the stock solution of ethylammonium lactate ionic liquid + saturated NH4Cl to excess CaSO4·2H2O to prepare a mixed solution, shake the mixed solution at 35 rpm and 35°C for 12 hours, and then centrifuge the solution at 3500 rpm (REMI R-8M) for 10 minutes.

[0022] Take all the supernatant and use standard EDTA and silver nitrate solution to determine Ca 2+ and Cl − Ion concentration, using barium chloride as a precipitant, the sulfate ion concentration was determined by gravimetric method. In this example, the maximum solubility of CaSO4·2H2O was 0.078 mol / kg.

[0023] Embodiment 2 S1. preparing an ammonium ionic liquid additive.

[0024] Ethylamine was placed in a round-bottom flask, and lactic acid was added dropwise at a molar ratio of 1:1 under ice bath and constant stirring. After complete addition, the reaction mixture was stirred at room temperature for 24 hours to obtain ethylammonium lactate ionic liquid. The ethylammonium lactate ionic liquid was dried in a rotary evaporator and stored in a vacuum desiccator with phosphorus pentoxide as a desiccant.

[0025] S2. Add 3.0 mol / kg NH4Cl solution to 7.5% ethylammonium lactate ionic liquid aqueous solution, mix well, and obtain a stock solution of ethylammonium lactate ionic liquid + saturated NH4Cl.

[0026] S3. Add the stock solution of ethylammonium lactate ionic liquid + saturated NH4Cl to excess CaSO4·2H2O to prepare a mixed solution, shake the mixed solution at 35 rpm and 35°C for 12 hours, and then centrifuge the solution at 3500 rpm (REMI R-8M) for 10 minutes.

[0027] Take all the supernatant and use standard EDTA and silver nitrate solution to determine Ca 2+ and Cl − Ion concentration, using barium chloride as a precipitant, the sulfate ion concentration was determined by gravimetric method. In this example, the solubility of CaSO4·2H2O was up to 0.095 mol / kg.

[0028] Embodiment 3 S1. preparing an ammonium ionic liquid additive.

[0029] Ethylamine was placed in a round-bottom flask, and lactic acid was added dropwise at a molar ratio of 1:1 under ice bath and constant stirring. After complete addition, the reaction mixture was stirred at room temperature for 24 hours to obtain ethylammonium lactate ionic liquid. The ethylammonium lactate ionic liquid was dried in a rotary evaporator and stored in a vacuum desiccator with phosphorus pentoxide as a desiccant.

[0030] S2. Add 2.5 mol / kg NH4Cl solution to 15% ethylammonium lactate ionic liquid aqueous solution, mix well, and obtain a stock solution of ethylammonium lactate ionic liquid + saturated NH4Cl.

[0031] S3. Add the stock solution of ethyl lactate ionic liquid + saturated NH4Cl to excess CaSO4·2H2O to prepare a mixed solution, shake the mixed solution at 35 rpm and 35°C for 12 h, and then centrifuge the solution at 3500 rpm (REMI R-8M) for 10 min.

[0032] Take all the supernatant and use standard EDTA and silver nitrate solution to determine Ca 2+ and Cl − Ion concentration, using barium chloride as a precipitant, the sulfate ion concentration was determined by gravimetric method. In this example, the solubility of CaSO4·2H2O was 0.092 mol / kg at most.

[0033] Embodiment 4 S1. preparing an ammonium ionic liquid additive.

[0034] Hydroxyethylamine was placed in a round-bottom flask, and acetic acid was added dropwise at a molar ratio of 1:1 under ice bath and constant stirring. After complete addition, the reaction mixture was stirred at room temperature for 24 hours to obtain dihydroxyethylammonium acetate ionic liquid. The dihydroxyethylammonium acetate ionic liquid was dried in a rotary evaporator and stored in a vacuum desiccator with phosphorus pentoxide as a desiccant.

[0035] S2. Add 2.0 mol / kg NH4Cl solution to 15% mass concentration of dihydroxyethylammonium acetate ion liquid aqueous solution, mix well, and obtain a stock solution of dihydroxyethylammonium acetate ion liquid + saturated NH4Cl.

[0036] S3. Add the stock solution of dihydroxyethylammonium acetate ionic liquid + saturated NH4Cl to excess CaSO4·2H2O to prepare a mixed solution, shake the mixed solution at 35 rpm and 35°C for 12 h, and then centrifuge the solution at 3500 rpm (REMI R-8M) for 10 min.

[0037] Take all the supernatant and use standard EDTA and silver nitrate solution to determine Ca 2+ and Cl− Ion concentration, using barium chloride as a precipitant, the sulfate ion concentration was determined by gravimetric method. In this example, the solubility of CaSO4·2H2O was 0.065 mol / kg at most.

[0038] Embodiment 5 S1. preparing an ammonium ionic liquid additive.

[0039] Trioctylamine was placed in a round-bottom flask, and hydrochloric acid was added dropwise at a molar ratio of 1:1 under ice bath and constant stirring. After complete addition, the reaction mixture was stirred at room temperature for 24 hours to obtain trioctyl ammonium chloride ionic liquid. The trioctyl ammonium chloride ionic liquid was dried in a rotary evaporator and stored in a vacuum desiccator with phosphorus pentoxide as a desiccant.

[0040] S2. Add 2.5 mol / kg NH4Cl solution to 7.5% mass concentration of trioctyl ammonium chloride ionic liquid aqueous solution, mix well, and obtain a stock solution of trioctyl ammonium chloride ionic liquid + saturated NH4Cl.

[0041] S3. Add the stock solution of trioctyl ammonium chloride ionic liquid + saturated NH4Cl to excess CaSO4·2H2O to prepare a mixed solution, shake the mixed solution at 35 rpm and 35°C for 12 hours, and then centrifuge the solution at 3500 rpm (REMI R-8M) for 10 minutes.

[0042] Take all the supernatant and use standard EDTA and silver nitrate solution to determine Ca 2+ and Cl − Ion concentration, using barium chloride as a precipitant, the sulfate ion concentration was determined by gravimetric method. In this example, the solubility of CaSO4·2H2O was 0.047 mol / kg at most.

[0043] Embodiment 6 S1. preparing an ammonium ionic liquid additive.

[0044] Ethylamine was placed in a round-bottom flask, and lactic acid was added dropwise at a molar ratio of 1:1 under ice bath and constant stirring. After complete addition, the reaction mixture was stirred at room temperature for 24 hours to obtain ethylammonium lactate ionic liquid. The ethylammonium lactate ionic liquid was dried in a rotary evaporator and stored in a vacuum desiccator with phosphorus pentoxide as a desiccant.

[0045] S2. Add 2.5 mol / kg NH4Cl solution to 15% ethylammonium lactate ionic liquid aqueous solution, mix well, and obtain a stock solution of ethylammonium lactate ionic liquid + saturated NH4Cl.

[0046] S3. Add the stock solution of ethyl lactate ionic liquid + saturated NH4Cl to excess CaSO4·2H2O to prepare a mixed solution, shake the mixed solution at 100 rpm and 35°C for 12 hours, and then centrifuge the solution at 3500 rpm (REMI R-8M) for 10 minutes.

[0047] Take all the supernatant and use standard EDTA and silver nitrate solution to determine Ca 2+ and Cl − Ion concentration, using barium chloride as a precipitant, the sulfate ion concentration was determined by gravimetric method. In this example, the solubility of CaSO4·2H2O was 0.090 mol / kg at most.

[0048] Embodiment 7 S1. preparing an ammonium ionic liquid additive.

[0049] Ethylamine was placed in a round-bottom flask, and lactic acid was added dropwise at a molar ratio of 1:1 under ice bath and constant stirring. After complete addition, the reaction mixture was stirred at room temperature for 24 hours to obtain ethylammonium lactate ionic liquid. The ethylammonium lactate ionic liquid was dried in a rotary evaporator and stored in a vacuum desiccator with phosphorus pentoxide as a desiccant.

[0050] S2. Add 2.5 mol / kg NH4Cl solution to 10% ethylammonium lactate ionic liquid aqueous solution, mix well, and obtain a stock solution of ethylammonium lactate ionic liquid + saturated NH4Cl.

[0051] S3. Add the stock solution of ethylamine lactate ionic liquid + saturated NH4Cl to excess CaSO4·2H2O to prepare a mixed solution, shake the mixed solution at 75 rpm and 20°C for 12 h, and then centrifuge the solution at 3500 rpm (REMI R-8M) for 10 min.

[0052] Take all the supernatant and use standard EDTA and silver nitrate solution to determine Ca 2+ and Cl − Ion concentration, using barium chloride as a precipitant, the sulfate ion concentration was determined by gravimetric method. In this example, the solubility of CaSO4·2H2O was up to 0.12 mol / kg.

[0053] The solubility of CaSO4·2H2O in 0-5.5mol / kgNH4Cl solution increases first and then decreases with the increase of the molar concentration of NH4Cl solution. When the molar concentration of NH4Cl solution is 2.75mol / kg and the mass concentration of ethylammonium lactate ionic liquid is 10%, the solubility of CaSO4·2H2O is 0.12mol / kg at most. It can be seen that the addition of ammonium ionic liquid additives to NH4Cl solution significantly increases the solubility of CaSO4·2H2O in NH4Cl solution, which can effectively inhibit the scaling of CaSO4·2H2O in the evaporator.

[0054] Therefore, the method for inhibiting scaling of calcium sulfate in an evaporator according to the present invention can solve the problem that calcium sulfate is easily scaled in an ammonium chloride solution and causes evaporator blockage.

[0055] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A method for inhibiting scaling of calcium sulfate in an evaporator, characterized in that: The following steps are involved: S1, preparing ammonium ionic liquid additives; S2, adding NH4Cl solution to the ammonium ionic liquid additive, mixing evenly, to obtain a stock solution of ammonium ionic liquid + NH4Cl; S3. Add CaSO4·2H2O to the stock solution of ammonium ionic liquid + NH4Cl to prepare a mixed solution, mix the mixed solution evenly, centrifuge the mixed solution, take the supernatant, and obtain a solution.

2. A method for inhibiting scaling of calcium sulfate in an evaporator according to claim 1, characterized in that: In S1, the preparation method of the ammonium ionic liquid additive comprises: S11, placing an amine solution in a flask, adding an acid solution into the flask under an ice bath condition, and stirring and mixing the amine solution and the acid solution at room temperature to obtain a reaction solution; S12, drying the reaction solution in a rotary evaporator to obtain an ammonium ionic liquid additive; the ammonium ionic liquid additive after drying is stored in a vacuum dryer using phosphorus pentoxide as a desiccant.

3. A method for inhibiting scaling of calcium sulfate in an evaporator according to claim 2, characterized in that: In the S11, the molar ratio of the amine solution to the acid solution is 1:1, and the stirring time is 20h-30h.

4. A method for inhibiting scaling of calcium sulfate in an evaporator according to claim 3, characterized in that: In the S11, the amine solution is one of 2-hydroxyamine, di(2-hydroxy)amine, tri-(2-hydroxy)amine, hydroxymethylamine, hydroxyethylamine, hydroxypropylamine, hydroxypropylmethylamine, hydroxypropyldimethylamine, ethylamine, diethylamine, triethylamine, tripropylamine, tributylamine, tripentylamine, trihexylamine, trioctylamine, and didecyldimethylamine.

5. A method for inhibiting scaling of calcium sulfate in an evaporator according to claim 4, characterized in that: The amine solution is 5.3 mol / L ethylamine or 11.33 mol / L hydroxyethylamine.

6. A method for inhibiting scaling of calcium sulfate in an evaporator according to claim 1, characterized in that: The acidic solution is one of hydrochloric acid, lactic acid, 2-hydroxypropionic acid, acetic acid, propionic acid, butyric acid, salicylic acid, m-hydroxybenzoic acid, p-hydroxybenzoic acid, malonic acid, and succinic acid.

7. A method for inhibiting scaling of calcium sulfate in an evaporator according to claim 1, characterized in that: The acidic solution is 11.3 mol / L lactic acid or 17.3 mol / L acetic acid.

8. A method for inhibiting scaling of calcium sulfate in an evaporator according to claim 1, characterized in that: In the S2, the mass concentration of the ammonium ionic liquid is 5%-15%; the molar concentration of the NH4Cl solution is 1 mol / kg-5.5 mol / kg.

9. A method for inhibiting scaling of calcium sulfate in an evaporator according to claim 1, characterized in that: In S2, the mass ratio of the ammonium ionic liquid to the NH4Cl solution is 0.019-0.

103.

10. A method for inhibiting scaling of calcium sulfate in an evaporator according to claim 1, characterized in that: In the S3, the mixed solution is shaken at 10 rpm-100 rpm and 20° C.-50° C. for 10 h-15 h for mixing; and centrifuged at 3500 rpm for 10 min.

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