High-temperature-resistant composite scale inhibitor for evaporator and preparation method thereof

Abstract

The present application relates to a kind of high-temperature-resistant composite scale inhibitor for evaporator and its preparation method, belong to industrial water treatment scale inhibitor technical field.The present application obtains heat-resistant phosphonocarboxylic acid by compounding PBTC with PAPEMP according to specific proportion, relies on the rigid skeleton of ether bond inside PAPEMP molecule to form molecular protection to PBTC, inhibits the high-temperature hydrolysis of phosphonic acid CP bond;With diethanolamine, construct high-temperature pH buffer environment, further weaken the hydrolysis damage of phosphonic acid functional group in high-temperature water environment.Simultaneously, ternary copolymer introduces methyl allyl sulfonate rigid heat-resistant branch chain, so that polymer main chain is not prone to thermal degradation under the condition of evaporator high temperature, continuously retains chelation, dispersion active site, overcome the inherent defects of ordinary AA-AMPS binary copolymer, such as molecular chain breakage, function failure under high temperature, and has wide application prospect.

Description

Technical Field

[0001] This invention relates to a high-temperature resistant composite scale inhibitor for evaporators and its preparation method, belonging to the technical field of scale inhibitors for industrial water treatment. Background Technology

[0002] Currently, zero-discharge industrial wastewater treatment often uses MVR or multi-effect evaporators to concentrate and solidify RO concentrate, which operates at high temperatures. Calcium, magnesium, silicon, and sulfate ions continuously accumulate in the concentrate. Under high-temperature conditions, calcium carbonate, calcium sulfate, and calcium magnesium silicate rapidly crystallize, forming dense, hard scale on the heat exchanger tube walls. This leads to decreased heat transfer efficiency, increased energy consumption, and tube blockage causing shutdowns. Silicon complex scale is difficult to completely remove with conventional acid washing.

[0003] Currently, the industry often directly adds conventional reverse osmosis antiscalants to the evaporation feed water. However, ordinary antiscalants have poor heat resistance and are prone to decomposition and failure at high temperatures, making it difficult to meet the harsh operating conditions of evaporators.

[0004] Existing scale inhibitors generally suffer from high-temperature hydrolysis and failure, and silicon... The problems of insufficient calcium complex scale inhibition, easy formation of secondary calcium phosphate scale at high temperatures, poor storage stability of reagents, and complex formulations urgently require the development of a product specifically adapted to industrial wastewater zero-discharge evaporator 85. A special scale inhibitor for high-temperature, high-salt concentrated water conditions at 120℃.

[0005] In view of the above-mentioned shortcomings, the present invention aims to create a high-temperature resistant composite scale inhibitor for evaporators and its preparation method, so as to make it more valuable for industrial use. Summary of the Invention

[0006] To address the aforementioned technical problems, the present invention aims to provide a high-temperature resistant composite scale inhibitor for evaporators and its preparation method. This agent simultaneously inhibits the formation of calcium carbonate, calcium sulfate, magnesium silicate, and silica scale, thereby extending the evaporator's operating cycle and reducing energy consumption and maintenance costs.

[0007] The present invention provides a high-temperature resistant composite scale inhibitor for evaporators, which is composed of the following raw materials in parts by weight:

[0008] The heat-resistant phosphonic acid contains 16-34 parts; the heat-resistant phosphonic acid of this invention stably chelates calcium and magnesium metal ions in water under high temperature conditions, interfering with the crystallization nucleation process of calcium and magnesium salts; the AA-AMPS-methylallyl sulfonate terpolymer carries high-density sulfonic acid groups, which can adsorb silica colloidal particles and block Si from crystallizing by means of electrostatic repulsion and steric hindrance. O The Si condensation reaction inhibits the formation of dense and irreversible silica scale at the source; the phosphorus-free PESA component exerts a lattice distortion effect to specifically inhibit the crystallization and precipitation of calcium sulfate, forming a multi-synergistic scale-inhibiting effect with phosphonic acid and sulfonated polymers, solving the industry problem of the difficulty in controlling silica-calcium composite hard scale in evaporators.

[0009] 22-44 parts of acrylic acid-AMPS-methylallyl sulfonate terpolymer; 7-18 parts of polyepoxysuccinic acid; Diethanolamine 4-10 parts; Diethanolamine constructs a high-temperature pH buffer microenvironment, inhibiting hydrolysis and abnormal association precipitation of the agent components during heated storage. Under heated storage conditions in a preheated tank, the agent maintains system homogeneity, preventing stratification, turbidity, and flocculent precipitation, thus solving the problems of existing scale inhibitors easily precipitating impurities upon heating and exhibiting large fluctuations in scale inhibition effect during on-site addition.

[0010] Potassium citrate 1-7 parts; the potassium citrate in the formulation of this invention can complex and capture Fe³⁺. + Al³ + This eliminates the catalytic side effects of metal ions and further ensures the effect of inhibiting silica scale buildup.

[0011] Add deionized water to bring the total to 100 parts; The heat-resistant phosphonic acid is a compound of 2-phosphono-1,2,4-tricarboxybutane and polyamine polyether methylenephosphonic acid, with a mass ratio of 2-phosphono-1,2,4-tricarboxybutane to polyamine polyether methylenephosphonic acid of 3:1; the acrylic acid-AMPS-methylallyl sulfonate terpolymer has a weight-average molecular weight (Mw) of 3000 to 5000.

[0012] This invention combines PBTC and PAPEMP in a specific ratio to obtain heat-resistant phosphonic acid. The rigid ether linkages within the PAPEMP molecule provide molecular protection for PBTC, inhibiting the formation of phosphonic acid C. The P-bonds undergo high-temperature hydrolysis; the presence of diethanolamine creates a high-temperature pH buffer environment, further mitigating the hydrolytic damage to phosphonic acid functional groups caused by the high-temperature water environment. Simultaneously, the terpolymer introduces rigid, heat-resistant branches of methyl allyl sulfonate, making the polymer backbone less susceptible to thermal degradation under the high-temperature conditions of the evaporator, thus preserving chelating and dispersing active sites and overcoming the inherent defects of ordinary AA-AMPS binary copolymers, such as chain breakage and functional failure at high temperatures.

[0013] Furthermore, the weight parts of each raw material are as follows: 26 parts of heat-resistant phosphonic acid, 32 parts of acrylic acid-AMPS-methylallyl sulfonate terpolymer, 12 parts of polyepoxysuccinic acid, 6 parts of diethanolamine, 4 parts of potassium citrate, and 20 parts of deionized water.

[0014] Furthermore, in the acrylic acid-AMPS-methylallyl sulfonate terpolymer, the molar ratio of the three monomers, acrylic acid, AMPS, and methylallyl sulfonate, is (2-4):(5-7):(1-2).

[0015] Furthermore, the acrylic acid-AMPS-methylallyl sulfonate terpolymer was prepared by aqueous solution free radical polymerization, using ammonium persulfate as an initiator, with a polymerization temperature of 75-90℃ and a polymerization time of 4-6h.

[0016] A method for preparing a high-temperature resistant composite scale inhibitor for evaporators includes the following steps: (1) Add all deionized water to the reactor at room temperature, and add diethanolamine and potassium citrate under stirring at 200-400 rpm, stirring until completely dissolved; (2) Increase the stirring speed to 400-600 rpm, add heat-resistant phosphonic acid, and stir until the system is mixed evenly and without stratification; (3) Maintain stirring at 400-600 rpm and slowly add acrylic acid-AMPS-methylallyl sulfonate terpolymer; after the addition is complete, increase the stirring speed to 800-1200 rpm and continue stirring; (4) Reduce the speed to 400-600 rpm, add polyepoxysuccinic acid, and stir to combine; (5) Keep warm at 40-50℃ for 1-3 hours, filter to remove trace amounts of insoluble impurities, and obtain the finished product.

[0017] Further, in step (1), the rotation speed is 300 rpm and the stirring time is 5 min; in step (2), the rotation speed is 500 rpm and the stirring time is 10 min; in step (3), the dripping time is 15 min, and after the dripping is completed, the high-speed stirring is 1000 rpm for 15 min; in step (4), the rotation speed is 500 rpm and the stirring time is 8 min; in step (5), the maturation temperature is 45℃ and the maturation time is 2 h.

[0018] A method for applying a high-temperature resistant composite scale inhibitor to an industrial wastewater zero-discharge evaporator involves continuously adding the high-temperature resistant composite scale inhibitor to the evaporator inlet water system at a dosage of 4-6 ppm, measured by the evaporator inlet water flow meter. Applicable operating conditions include: evaporation temperature of 85-120℃, inlet water TDS of 50000-100000 mg / L, and inlet water SiO2 concentration of 100-250 mg / L. No pH adjustment of the inlet water is required when adding the agent.

[0019] By means of the above-described solution, the present invention has at least the following advantages: (1) In this invention, PBTC and PAPEMP are compounded in a specific ratio to obtain heat-resistant phosphonic acid. The rigid ether bond backbone inside the PAPEMP molecule forms molecular protection for PBTC, inhibiting the C of phosphonic acid. The P-bonds undergo high-temperature hydrolysis; the presence of diethanolamine creates a high-temperature pH buffer environment, further mitigating the hydrolytic damage to phosphonic acid functional groups caused by the high-temperature water environment. Simultaneously, the terpolymer introduces rigid, heat-resistant branches of methyl allyl sulfonate, making the polymer backbone less susceptible to thermal degradation under the high-temperature conditions of the evaporator, thus preserving chelating and dispersing active sites and overcoming the inherent defects of ordinary AA-AMPS binary copolymers, such as chain breakage and functional failure at high temperatures.

[0020] (2) The heat-resistant phosphonic acid of the present invention stably chelates calcium and magnesium metal ions in water under high temperature conditions, interfering with the crystallization nucleation process of calcium and magnesium salts; the AA-AMPS-methylallyl sulfonate terpolymer carries high-density sulfonic acid groups, which can adsorb silica colloidal particles and block Si from crystallizing by means of electrostatic repulsion and steric hindrance. O The Si condensation reaction inhibits the formation of dense and irreversible silica scale at the source; the phosphorus-free PESA component exerts a lattice distortion effect to specifically inhibit the crystallization and precipitation of calcium sulfate, forming a multi-synergistic scale-inhibiting effect with phosphonic acid and sulfonated polymers, solving the industry problem of the difficulty in controlling silica-calcium composite hard scale in evaporators.

[0021] (3) Conventional organophosphorus scale inhibitors under high temperature conditions C The breakage of P bonds releases orthophosphate ions, which combine with high concentrations of calcium ions in concentrated water to form calcium phosphate precipitate. This can lead to a situation where adding chemicals actually exacerbates scaling. This invention employs a hydrolysis-resistant PBTC and PAPEMP compound system, combined with the buffering effect of diethanolamine, to significantly reduce the degree of phosphine group hydrolysis, making it less prone to secondary calcium phosphate precipitation under high-temperature conditions.

[0022] (4) Diethanolamine constructs a high-temperature pH buffer microenvironment to inhibit hydrolysis and abnormal association precipitation of the agent components during heated storage. The agent can maintain the system homogeneity under heated storage conditions in a preheating tank, and will not exhibit stratification, turbidity, or flocculent precipitation, thus solving the problem that existing scale inhibitors are prone to precipitating impurities when heated and have large fluctuations in scale inhibition effect when added on-site.

[0023] (5) Evaporation of concentrated water will introduce Fe³⁺. + Al³ + Trace amounts of metal ions are present, which act as catalysts, accelerating the dehydration condensation of silicic acid hydroxyl groups and promoting the formation of silica scale. The potassium citrate in the formulation of this invention can complex and capture Fe³⁺. + Al³ + This eliminates the catalytic side effects of metal ions and further ensures the effect of inhibiting silica scale buildup.

[0024] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, the preferred embodiments of the present invention are described in detail below. Detailed Implementation

[0025] The specific embodiments of the present invention will be described in further detail below with reference to the examples. These examples are for illustrative purposes only and are not intended to limit the scope of the invention.

[0026] A high-temperature resistant composite scale inhibitor for industrial wastewater zero-discharge evaporators is composed of the following raw materials in parts by weight: 16-34 parts of heat-resistant phosphonic acid; 2 parts of acrylic acid. Acrylamide 2 22-44 parts of methylpropanesulfonic acid (AMPS)-methylallyl sulfonate terpolymer; 7-18 parts of polyepoxysuccinic acid (PESA); 4-10 parts of diethanolamine; 1-7 parts of potassium citrate; deionized water to make up to 100 parts; The heat-resistant phosphonic acid is a compound of 2-phosphono-1,2,4-tricarboxybutane (PBTC) and polyamine polyether methylenephosphonic acid (PAPEMP) in a mass ratio of 3:1; the acrylic acid-AMPS-methylallyl sulfonate terpolymer has a weight-average molecular weight (Mw) of 3000–5000. In the acrylic acid-AMPS-methylallyl sulfonate terpolymer, the molar ratio of acrylic acid, AMPS, and methylallyl sulfonate monomers is (2–4):(5–7):(1–2). The acrylic acid-AMPS-methylallyl sulfonate terpolymer is prepared by aqueous solution free radical polymerization, using ammonium persulfate as an initiator, at a polymerization temperature of 75–90℃ and a polymerization reaction time of 4–6 h.

[0027] A method for preparing a high-temperature resistant composite scale inhibitor includes the following steps: S1: Add all deionized water to the reactor at room temperature, and add diethanolamine and potassium citrate under stirring at 200-400 rpm, stirring until completely dissolved; S2: Increase the stirring speed to 400-600 rpm, add heat-resistant phosphonic acid, and continue stirring until the mixture is uniform and there is no layering; S3: Maintain stirring at 400-600 rpm and slowly add acrylic acid-AMPS-methylallyl sulfonate terpolymer; after the addition is complete, increase the stirring speed to 800-1200 rpm and continue stirring; S4: Reduce the speed to 400-600 rpm, add polyepoxysuccinic acid, and stir to compound; S5: Keep warm at 40-50℃ for 1-3 hours, filter to remove trace amounts of insoluble impurities, and obtain the finished scale inhibitor.

[0028] A method for applying a high-temperature resistant composite scale inhibitor in an industrial wastewater zero-discharge evaporator: The composite scale inhibitor is continuously added to the evaporator inlet water system at a dosage of 4-6 ppm (based on the evaporator inlet water flow meter); applicable operating conditions: evaporation temperature 85-120℃, inlet water TDS 50000-100000 mg / L, inlet water SiO2 100-250 mg / L; the agent is added directly without prior adjustment of the inlet water pH.

[0029] Example 1 A high-temperature resistant composite scale inhibitor for zero-discharge evaporators of industrial wastewater is composed of the following raw materials in parts by weight: 26 parts of heat-resistant phosphonic acid (PBTC:PAPEMP=3:1); 32 parts of acrylic acid-AMPS-methylallyl sulfonate terpolymer (Mw≈4000); 12 parts of polyepoxysuccinic acid (PESA); 6 parts of diethanolamine; 4 parts of potassium citrate; and 20 parts of deionized water. A method for preparing a high-temperature resistant composite scale inhibitor includes the following steps: S1: Add all deionized water to the reactor at room temperature, and add diethanolamine and potassium citrate under stirring at 300 rpm, stirring until completely dissolved; S2: Increase the stirring speed to 500 rpm, add heat-resistant phosphonic acid, and continue stirring until the mixture is uniform and there is no layering; S3: Maintain stirring at 500 rpm and slowly add acrylic acid-AMPS-methylallyl sulfonate terpolymer; after the addition is complete, increase the stirring speed to 1000 rpm and continue stirring; S4: Reduce the speed to 500 rpm, add polyepoxysuccinic acid, and stir to compound; S5: Keep warm at 45℃ for 2 hours, filter to remove trace amounts of insoluble impurities, and obtain the finished scale inhibitor.

[0030] A method for applying a high-temperature resistant composite scale inhibitor in an industrial wastewater zero-discharge evaporator: The composite scale inhibitor is continuously added to the evaporator inlet water system at a dosage of 5 ppm (based on the evaporator inlet water flow rate); the simulated evaporator temperature is 105℃, the concentrated water SiO2 is 220 mg / L, TDS is 80000 mg / L, pH is 8.5, and the scale inhibitor dosage is 5 ppm. The agent is added directly without prior adjustment of the inlet water pH.

[0031] Example 2 In this embodiment, the composite scale inhibitor, by weight, consists of 18 parts heat-resistant phosphonic acid, 40 parts AA-AMPS-methylallyl sulfonate terpolymer, 8 parts PESA, 5 parts diethanolamine, 5 parts potassium citrate, and 24 parts deionized water; the preparation process is the same as in Example 1, and the dosage is 5 ppm.

[0032] Example 3 In this embodiment, the composite scale inhibitor, by weight, consists of 32 parts heat-resistant phosphonic acid, 24 parts AA-AMPS-methylallyl sulfonate terpolymer, 16 parts PESA, 8 parts diethanolamine, 3 parts potassium citrate, and 17 parts deionized water; the preparation process is the same as in Example 1, and the dosage is 5 ppm.

[0033] Example 4 The composite scale inhibitor in this embodiment, by weight, consists of 17 parts heat-resistant phosphonic acid, 42 parts AA-AMPS-methylallyl sulfonate terpolymer, 17 parts PESA, 7 parts diethanolamine, 6 parts potassium citrate, and 11 parts deionized water; the preparation process is the same as in Example 1, and the dosage is 5 ppm.

[0034] Example 5 In this embodiment, the composite scale inhibitor, by weight, consists of 16 parts heat-resistant phosphonic acid; 22 parts AA-AMPS-methylallyl sulfonate terpolymer; 7 parts PESA; 4 parts diethanolamine; 1 part potassium citrate; and 50 parts deionized water, with a dosage of 5 ppm.

[0035] Example 6 In this embodiment, the composite scale inhibitor, by weight, consists of 34 parts heat-resistant phosphonic acid; 44 parts AA-AMPS-methylallyl sulfonate terpolymer; 18 parts PESA; 10 parts diethanolamine; 7 parts potassium citrate; and 7 parts deionized water, with a dosage of 5 ppm.

[0036] Example 7 In this embodiment, the composite scale inhibitor, by weight, comprises 26 parts of heat-resistant phosphonocarboxylic acid (PBTC:PAPEMP = 5:1); AA AMPS 32 parts of methyl allyl sulfonate terpolymer; 12 parts of PESA; 6 parts of diethanolamine; 4 parts of potassium citrate; 20 parts of deionized water; dosage 5 ppm.

[0037] Comparative Example Comparative Example 1 This comparative formulation uses 26 parts HEDP, 32 parts PAA, and 42 parts deionized water to simulate a conventional binary compound system of RO scale inhibitors.

[0038] Comparative Example 2 This comparative formulation uses 15 parts PBTC, 5 parts PAPEMP, 32 parts AA / AMPS binary copolymer, and 48 parts deionized water to simulate a scale inhibitor without PESA, stabilizer, or third monomer.

[0039] Comparative Example 3 The formulation of this comparative example is the same as that of Example 1, except that diethanolamine and potassium citrate are removed and replaced with an equal amount of deionized water.

[0040] Comparative Example 4 This comparative example has the same formula as Example 1, where the AA-AMPS-methallyl sulfonate terpolymer is replaced with an equal mass of AA-AMPS dipolymer.

[0041] Performance tests were carried out on Examples 1-4 of the present invention and Comparative Examples 1-4 respectively, and the test results are shown in Table 1: The instruments and detection methods for performance evaluation of the examples and comparative examples of the present invention are as follows: wherein the detection of silicon scale refers to national standards, the scale inhibition against calcium carbonate refers to the general industrial static scale inhibition test method; high-temperature aging of the chemical agent, storage stability and simulated evaporation operation are simulation test methods established by the present invention for the working conditions of evaporators.

[0042] 1. Retention rate of effective components after high-temperature aging at 90°C for 72h Test method: seal the scale inhibitor for high-temperature aging, and evaluate the retention capacity of active components of the chemical agent at high temperature by measuring the mass fraction of total solids before and after aging. Operation steps: take two equal parts of the scale inhibitor to be tested, one as the initial sample; place the other in a sealed pressure-resistant aging tank for constant-temperature aging at 90°C for 72h. Accurately weigh the same mass of the initial sample and the aged sample respectively, place them in an evaporation dish that has been constant in weight, dry them to constant weight in a 105°C forced-air drying oven, cool and weigh, and calculate the total solid content.

[0043] Retention rate of effective components (%) = (total solid content of aged sample / total solid content of initial sample) × 100%.

[0044] 2. Determination of calcium carbonate scale inhibition rate Refer to HG / T 2430-2020 "Water Treatment Agents - Determination of Scale Inhibition Performance - Calcium Carbonate Deposition Method", the test temperature is adjusted to 105°C to adapt to the high-temperature working conditions of evaporators.

[0045] 3. Determination of silicon scale inhibition rate Implement the silicon molybdenum blue spectrophotometry in GB / T 12149-2017 "Determination of Silicon in Industrial Circulating Cooling Water and Boiler Water" to determine the content of soluble silicon dioxide.

[0046] 4. High-temperature storage stability test of chemical agent Simulate the storage working condition of the chemical agent in the preheating tank at 60-80°C at the front end of the evaporator, and investigate whether hydrolysis, delamination or precipitation occurs in the chemical agent. Operation steps: seal the scale inhibitor sample to be tested in a polyethylene sample bottle, place it in a high-temperature aging box at 80°C for constant-temperature placement for 72h; take it out and cool to room temperature, visually observe whether delamination, turbidity or flocculent precipitate appears in the sample; when turbid precipitate occurs, filter with a 0.45μm filter membrane and weigh the mass of insoluble matter. Evaluation criterion: the sample is clear and uniform, without delamination or precipitate, which is qualified. Test instruments: high-temperature aging test chamber, sealed polyethylene sample bottle, 0.45μm filter membrane.

[0047] 5. Simulated evaporator continuous operation test A simulated evaporation and concentration device was used to reproduce the high-temperature, high-salt concentration conditions of an industrial MVR / multi-effect evaporator at 85-120℃. The decrease in the total heat transfer coefficient (TDS) was used as the criterion for system scaling. Operating conditions: Simulated influent water quality: TDS = 80000 mg / L, SiO2 = 220 mg / L, pH = 8.5; evaporation temperature 105℃; scale inhibitor dosage 5 ppm (based on influent water); continuous system operation, with real-time monitoring of the TDS. When the TDS decreased to 80% of the initial TDS, the system was considered to have reached the operational endpoint for scaling, and the number of consecutive operating days was recorded. Experimental instruments: Simulated evaporation and concentration experimental device, online temperature / flow rate monitoring module.

[0048] 6. Calcium sulfate scale inhibition rate at 105℃: The ability of calcium sulfate to inhibit scale was evaluated through a static high-temperature calcium sulfate deposition test. 7. Tendency of secondary scale formation of calcium phosphate: The amount of calcium phosphate precipitate in the system was measured after being kept at 105℃ for 24 hours to characterize the risk of secondary scale formation caused by high-temperature hydrolysis of phosphonic acid.

[0049] Test conditions: simulated influent TDS=80000mg / L, SiO2=220mg / L, pH=8.5, scale inhibitor dosage 5ppm.

[0050] Table 1 Performance Test Results

[0051] Analysis of test results: As shown in Table 1, the performance test results of Examples 1-7 of the present invention are significantly better than the blank control group and each comparative example in terms of various indicators, including the retention rate of effective components after high-temperature aging at 90℃ for 72h, the scale inhibition rate of calcium carbonate at 105℃, the scale inhibition rate of silica at 105℃, the tendency of secondary scale formation of calcium phosphate, the high-temperature storage stability of the reagent, and the number of days of continuous operation of the simulated evaporator. The specific analysis is as follows: This invention uses PBTC and PAPEMP in a 3:1 mass ratio as a heat-resistant phosphonic acid, and combines it with diethanolamine to construct a high-temperature pH buffer microenvironment. Table 1 shows that the effective component retention rates at 90℃ and 72h in Examples 1–6 were 78.3%–87.5%, with extremely low to very low tendency for secondary scaling of calcium phosphate; among them, Example 6 had the highest effective component retention rate, reaching 87.5%.

[0052] In Example 7, the mass ratio of PBTC to PAPEMP was adjusted to 5:1 (reducing the proportion of PAPEMP). The retention rate of its effective components decreased to 74.6%, the tendency for secondary scaling of calcium phosphate increased to moderate, and the number of days the simulated evaporator operated continuously decreased from 116 days in Example 1 to 70 days. These results indicate that the rigid ether bond framework within the PAPEMP molecule protects the CP bonds of PBTC. When the proportion of PAPEMP is insufficient, the high-temperature hydrolysis of phosphonic acid intensifies, and the hydrolysis resistance significantly decreases.

[0053] Comparative Example 1 used a conventional RO scale inhibitor system (HEDP+PAA), with an effective component retention rate of only 37.6% and a high tendency for secondary calcium phosphate scaling. This indicates that conventional organophosphorus scale inhibitors undergo extensive CP bond breakage and hydrolysis under high-temperature conditions in the evaporator, releasing orthophosphate ions that combine with high-concentration calcium ions in the concentrate to form calcium phosphate precipitates. This results in the phenomenon that adding the agent actually exacerbates scaling.

[0054] Comparative Example 2 retained the combination of PBTC and PAPEMP but lacked diethanolamine. The effective component retention rate was 68.5%, and the tendency for secondary scaling with calcium phosphate was moderate, significantly lower than that of Examples 1-6. This demonstrates that the pH buffer microenvironment constructed by diethanolamine can further weaken the hydrolytic damage of phosphonic acid functional groups caused by high-temperature water environment. Comparative Example 3 removed diethanolamine and potassium citrate, further reducing the effective component retention rate to 61.5%, and the tendency for secondary scaling with calcium phosphate was relatively high.

[0055] The above results confirm that the 3:1 mixture of PBTC and PAPEMP, combined with a diethanolamine buffer system, can significantly inhibit the high-temperature hydrolysis of phosphonic acid and reduce the risk of secondary scale formation in calcium phosphate.

[0056] This invention employs a terpolymer with rigid, heat-resistant branches of methyl allyl sulfonate to overcome the high-temperature molecular chain scission failure defect of ordinary AA-AMPS binary copolymers. As shown in Table 1, the silica scale inhibition rates at 105℃ for Examples 1–6 range from 79.5% to 91.3%, with Example 6 achieving a silica scale inhibition rate of 91.3%.

[0057] Comparative Example 4 replaced the terpolymer of the present invention with an equal mass of AA-AMPS binary copolymer, resulting in a silica scale inhibition rate of 72.8%, an effective component retention rate of 72.3%, and a simulated evaporator continuous operation period of only 74 days, far lower than the 116 days in Example 1. Comparative Example 2 also used AA-AMPS binary copolymer, but the silica scale inhibition rate was only 65.2%.

[0058] The above comparison results show that the introduction of the heat-resistant rigid side chain of methyl allyl sulfonate makes the polymer backbone less prone to thermal degradation under the high temperature conditions of the evaporator, and continuously retains the chelating and dispersing active sites; at the same time, the high-density sulfonic acid groups carried by the terpolymer can adsorb silica colloidal particles, and block the Si-O-Si condensation reaction by means of electrostatic repulsion and steric hindrance, thereby inhibiting the formation of dense irreversible silica scale from the source.

[0059] This invention achieves synergistic scale inhibition through a multi-component approach: heat-resistant phosphonic acid chelates calcium and magnesium ions, a ternary sulfonated polymer inhibits silica scale, and PESA exerts a lattice distortion effect to inhibit calcium sulfate crystallization. Table 1 shows that the blank control group's simulated evaporator reached the scaling endpoint after only 3 days of continuous operation; the simulated evaporators in Examples 1-6 operated continuously for 81-121 days, with Example 6 reaching 121 days. Its calcium carbonate scale inhibition rate at 105℃ was 93.2%, and its silica scale inhibition rate was 91.3%, demonstrating the best overall performance.

[0060] The number of consecutive operating days of the simulated evaporators in each comparative example was significantly lower than that in the embodiments of the present invention: Comparative Example 1 was only 27 days, Comparative Example 2 was 62 days, Comparative Example 3 was 44 days, and Comparative Example 4 was 74 days. Among them, Comparative Example 2 lacked the PESA component, and could not exert the lattice distortion effect to inhibit calcium sulfate crystallization, resulting in a decrease in overall scale inhibition capacity and a significantly shortened operating cycle. This proves that there is a synergistic scale inhibition effect between PESA, phosphonic acid, and sulfonated polymers, which can achieve simultaneous control of calcium carbonate, calcium sulfate, and silicon-calcium composite scale.

[0061] As shown in Table 1, after 72 hours of storage at 80°C, all of the reagents in Examples 1 to 7 remained clear and uniform, without stratification or precipitation; Comparative Example 1 showed a large amount of turbid precipitate; Comparative Example 2 showed trace amounts of flocculent matter; and Comparative Example 3 showed slight stratification.

[0062] Comparative Examples 2 and 3 both lacked diethanolamine components, and the reagents exhibited varying degrees of precipitation or stratification under high-temperature storage conditions. This demonstrates that the pH buffer microenvironment constructed by diethanolamine can inhibit hydrolysis and abnormal association precipitation of reagent components during heated storage, ensuring the uniformity and stability of the system under heated storage conditions in the preheating tank at the front end of the evaporator. This solves the problems of existing scale inhibitors easily precipitating impurities when heated and having large fluctuations in scale inhibition effect when added on-site.

[0063] Fe³ introduced into the concentrated water during evaporation + Al³ + Trace amounts of metal ions can catalyze the dehydration condensation of silicic acid hydroxyl groups, accelerating the formation of silica scale. The potassium citrate in the formulation of this invention can complex and capture Fe³⁺. + Al³ + This eliminates the catalytic side effects of metal ions.

[0064] Comparing Example 1 and Comparative Example 3, it can be seen that after removing potassium citrate (and diethanolamine) from Comparative Example 3, the silica scale inhibition rate dropped sharply from 90.6% in Example 1 to 36.4%. Furthermore, in Example 5, using 1 part of the lower limit of the potassium citrate formulation, the silica scale inhibition rate was 79.5%; in Example 6, using 7 parts of the upper limit of the potassium citrate formulation, the silica scale inhibition rate reached 91.3%. The silica scale inhibition effect showed a positive increasing trend with the increase of potassium citrate dosage, confirming the auxiliary enhancing effect of potassium citrate complexing metal ions on silica scale inhibition.

[0065] In summary, the components of this invention are not simply physically mixed, but rather, through the synergistic combination of PBTC / PAPEMP=3:1 heat-resistant phosphonic acid, AA-AMPS-methylallyl sulfonate terpolymer, PESA, diethanolamine, and potassium citrate, under the high-temperature and high-salt conditions of the evaporator (85–120°C), the following are achieved: (1) significantly inhibiting the high-temperature hydrolysis of phosphonic acid and reducing the risk of secondary scaling of calcium phosphate; (2) effectively inhibiting the scaling of silica, calcium carbonate, and calcium sulfate; (3) significantly extending the continuous operation cycle of the evaporator; and (4) ensuring the high-temperature storage stability of the reagents. Comparative studies, by omitting key components or replacing key structures, all exhibited problems such as decreased retention rate of effective components, reduced scale inhibition rate, increased risk of secondary scaling, worsened storage stability, and shortened simulated evaporation operation cycle, thus verifying the synergistic effect of the technical solution of this invention.

[0066] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A high-temperature resistant composite scale inhibitor for evaporators, characterized in that, It consists of the following raw materials in parts by weight: 16–34 parts of heat-resistant phosphonic acid; 22-44 parts of acrylic acid-AMPS-methylallyl sulfonate terpolymer; 7-18 parts of polyepoxysuccinic acid; 4-10 parts of diethanolamine; 1-7 parts potassium citrate; Add deionized water to bring the total to 100 parts; The heat-resistant phosphonic acid is a compound of 2-phosphono-1,2,4-tricarboxybutane and polyamine polyether methylenephosphonic acid, with a mass ratio of 2-phosphono-1,2,4-tricarboxybutane to polyamine polyether methylenephosphonic acid of 3:1; the acrylic acid-AMPS-methylallyl sulfonate terpolymer has a weight-average molecular weight (Mw) of 3000 to 5000.

2. The high-temperature resistant composite scale inhibitor for evaporators according to claim 1, characterized in that: The weight parts of each raw material are as follows: 26 parts of heat-resistant phosphonic acid, 32 parts of acrylic acid-AMPS-methylallyl sulfonate terpolymer, 12 parts of polyepoxysuccinic acid, 6 parts of diethanolamine, 4 parts of potassium citrate, and 20 parts of deionized water.

3. The high-temperature resistant composite scale inhibitor for evaporators according to claim 1, characterized in that: In the acrylic acid-AMPS-methylallyl sulfonate terpolymer, the molar ratio of the three monomers, acrylic acid, AMPS and methylallyl sulfonate, is (2-4):(5-7):(1-2).

4. According to claim 1 3. A high-temperature resistant composite scale inhibitor for evaporators according to any one of the claims, characterized in that: The acrylic acid-AMPS-methylallyl sulfonate terpolymer was prepared by aqueous solution free radical polymerization, using ammonium persulfate as the initiator, with a polymerization temperature of 75-90℃ and a polymerization time of 4-6h.

5. A method for preparing a high-temperature resistant composite scale inhibitor for evaporators according to any one of claims 1-4, characterized in that, Includes the following steps: (1) Add all deionized water to the reactor at room temperature, and add diethanolamine and potassium citrate under stirring at 200-400 rpm, stirring until completely dissolved; (2) Increase the stirring speed to 400-600 rpm, add heat-resistant phosphonic acid, and stir until the system is mixed evenly and without stratification; (3) Maintain stirring at 400-600 rpm and slowly add acrylic acid-AMPS-methylallyl sulfonate terpolymer; after the addition is complete, increase the stirring speed to 800-1200 rpm and continue stirring; (4) Reduce the speed to 400-600 rpm, add polyepoxysuccinic acid, and stir to combine; (5) Keep warm at 40-50℃ for 1-3 hours, filter to remove trace amounts of insoluble impurities, and obtain the finished product.

6. The method for preparing the high-temperature resistant composite scale inhibitor for evaporators according to claim 5, characterized in that: Step (1) The rotation speed is 300 rpm and the stirring time is 5 min; Step (2) The rotation speed is 500 rpm and the stirring time is 10 min; Step (3) The dripping time is 15 min, and after the dripping is completed, the high-speed stirring is 1000 rpm for 15 min; Step (4) The rotation speed is 500 rpm and the stirring time is 8 min; Step (5) The maturation temperature is 45℃ and the maturation time is 2 h.

7. A method for applying the high-temperature resistant composite scale inhibitor for evaporators according to any one of claims 1-4 in an industrial wastewater zero-discharge evaporator, characterized in that: The high-temperature resistant composite scale inhibitor is continuously added to the evaporator inlet water system at a dosage of 4-6 ppm, based on the evaporator inlet water flow meter. Applicable operating conditions: evaporation temperature 85-120℃, inlet water TDS 50000-100000 mg / L, inlet water SiO2 concentration 100-250 mg / L. No adjustment of inlet water pH is required when adding the agent.

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