Method for improving yield of polyaluminum chloride by using dispersing agent

Abstract

The invention relates to the technical field of water treatment agent production, in particular to a method for improving the yield of polyaluminum chloride by using a dispersing agent, which comprises the following steps: firstly, carrying out filter pressing treatment on a PAC liquid, and then adding the dispersing agent into the liquid, preferably, the dispersing agent is formed by mixing polyaspartic acid and sorbitol alkylate according to a ratio of 2: 10, and the adding amount is 0.1-0.5% of the weight of the PAC liquid. The dispersing agent can be added before or after filter pressing, after the dispersing agent is added, heat preservation is carried out for 20 minutes under the optimal condition that the temperature is 90 DEG C, the appearance color of the treated PAC liquid is changed from faint yellow to slightly red, sludge at the bottom is deposited and is not soft, the content of aluminum oxide reaches 10.6%, the basicity reaches 52%, the content of sulfate radicals is reduced to 0.22%, and the COD value is reduced to 21005 mg / L. By means of the method, generation of precipitates is remarkably reduced, and the cost is reduced. The yield and the quality of the PAC are improved, the flowability and the equipment compatibility are improved, and the method has a wide application prospect.

Description

Technical Field

[0001] The invention relates to the technical field of water treatment agent production, in particular to a method for improving the yield of polyaluminium chloride using a dispersant. Background Art

[0002] Polyaluminium chloride (PAC) is a highly effective inorganic polymer coagulant widely used in water treatment. Its excellent flocculation, low corrosiveness, and wide pH adaptability have led to its widespread application in drinking water purification and industrial wastewater treatment. However, due to the varying raw materials and complex production processes, PAC production often encounters a series of problems, particularly excessive precipitation in the product.

[0003] Main issues Excessive precipitation: During the PAC production process, due to the different raw materials, the product often contains a large amount of precipitates. These precipitates not only affect the purity and quality of the product, but may also cause problems in subsequent use.

[0004] Precipitation during storage and use: Even after preliminary filtration and purification, PAC liquid may still produce new precipitation during storage or use. These precipitations are easy to deposit on pipes and equipment, especially in small pipes, bends or blind sections, seriously affecting the normal use of equipment.

[0005] Equipment blockage and reduced efficiency: Sediment accumulation on pipes and equipment can reduce equipment availability, increase maintenance costs and frequency. Furthermore, sediment deposited on the bottom of storage tanks can also reduce the effective volume of the tanks and reduce storage capacity.

[0006] Water treatment effects are affected: The presence of sediment can directly affect the flocculation effect of PAC, resulting in poor water treatment results and even potentially causing major accidents. For example, in the drinking water treatment process, if the quality of PAC does not meet standards, it may cause water quality to substandard and threaten public health. Summary of the Invention

[0007] (1) Technical problems solved In view of the shortcomings of the prior art, the present invention provides a method for improving the yield of polyaluminium chloride by using a dispersant.

[0008] (2) Technical solution To achieve the above object, the present invention provides the following technical solution: A method for improving the yield of polyaluminium chloride by using a dispersant of the present invention comprises the following steps: In the production process of polyaluminium chloride, filter pressing is first carried out to remove silicate and soil impurities; adding a dispersant to the polyaluminium chloride liquid; After adding the dispersant, keep the mixture at 85-95℃ for 15-30 minutes and then cool it down.

[0009] Preferably, the dispersant is a mixture of polyaspartic acid and sorbitol alkylate, and the ratio of the mixture is 2:10.

[0010] Further preferably, the amount of the dispersant added is 0.1%-0.5% by weight of the polyaluminium chloride liquid.

[0011] Again preferably, the dispersant is added before or after the polyaluminium chloride liquid is filtered.

[0012] Preferably, the amount of the dispersant added before the polyaluminium chloride liquid is filtered is 0.2%-0.5%, and the amount of the dispersant added after the polyaluminium chloride liquid is filtered is 0.1%-0.3%.

[0013] Further preferably, the optimal heating temperature of the polyaluminium chloride liquid after adding the dispersant is 90° C., and the optimal holding time is 20 min.

[0014] Again preferably, after the polyaluminium chloride liquid is treated with a dispersant, its appearance color changes from the original light yellow to slightly reddish, and the sludge at the bottom is deposited and not soft.

[0015] Preferably, after adding the dispersant, the alumina content of the polyaluminium chloride liquid reaches 10.6%, the basicity reaches 52%, the sulfate content is reduced to 0.22%, and the COD value is reduced to 21005 mg / L.

[0016] (3) Beneficial effects Compared with the prior art, the present invention provides a method for improving the yield of polyaluminium chloride by using a dispersant, which has the following beneficial effects: Reduce precipitation: During the polyaluminium chloride (PAC) production process, filter pressing is first performed to remove impurities such as silicic acid and soil. A dispersant is then added to the PAC liquid. A preferred dispersant is a mixture of polyaspartic acid (PASP) and sorbitol alkylate in a ratio of 2:10. This dispersant combines inorganic substances such as calcium and silicon in the liquid through complexation, forming a soluble solution. This reduces the chance of these substances combining with aluminium ions to form precipitation, significantly reducing the amount of precipitation.

[0017] Optimize the amount and timing of addition: The optimal dispersant dosage is 0.1%-0.5% of the PAC liquid weight. The dosage before filter pressing is 0.2%-0.5%, and after filter pressing is 0.1%-0.3%. Experimental results show that under these conditions, the dispersant is most effective, effectively reducing precipitation while avoiding the increased costs and unnecessary side effects caused by excessive use.

[0018] Heating and insulation treatment improves the effect: After adding the dispersant, heat the mixture at 85-95°C for 15-30 minutes before cooling. The optimal heating temperature is 90°C, and the optimal holding time is 20 minutes. This process helps the dispersant fully absorb the inorganic matter in the liquid, further reducing precipitation and improving the overall performance of the PAC liquid. The treated PAC liquid exhibits improved flocculation.

[0019] Improve product quality: The treated PAC liquid had an alumina content of 10.6%, a basicity of 52%, a sulfate content of 0.22%, and a COD value of 21005 mg / L. These significant improvements demonstrate that dispersant treatment not only increases the active ingredient content of the PAC liquid but also significantly reduces chemical oxygen demand, enhancing the product's environmental friendliness and economic value.

[0020] Appearance changes and deposition characteristics: After treatment with the dispersant, the color of the PAC liquid changed from pale yellow to a slightly reddish hue, and the sludge at the bottom settled more easily and remained less loose. This indicates that the dispersant not only changed the color of the liquid but also improved its physical properties, making the sludge at the bottom more compact and less prone to loosening, which facilitates subsequent processing and storage.

[0021] Mobility and device compatibility: Fluidity tests showed that the treated PAC liquid flowed better within the pipeline, was less likely to settle on the bottom of the equipment, had less floating mud on the pump surface, and had a faster flow rate. This means that this method not only improves the quality of PAC liquid but also significantly enhances its fluidity and equipment compatibility in practical applications, extending equipment life and reducing maintenance costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The diagram is a schematic diagram of the production process of polyaluminium chloride of the present invention. DETAILED DESCRIPTION

[0023] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0024] See also Figure 1 The method for improving the yield of polyaluminium chloride by using a dispersant of the present invention comprises the following steps: In the production process of polyaluminium chloride, filter pressing is first carried out to remove silicate and soil impurities; adding a dispersant to the polyaluminium chloride liquid; After adding the dispersant, keep the mixture at 85-95℃ for 15-30 minutes and then cool it down.

[0025] This technical solution provides a method for increasing the yield of polyaluminium chloride (PAC) by adding a specific dispersant. By optimizing the dispersant selection, addition amount, and processing conditions, this method significantly reduces precipitation, increases the alumina content in the PAC liquid, and reduces the chemical oxygen demand (COD). The following is the main working principle of this method and the working principle of its preferred technical solution.

[0026] Dispersant synergistic mechanism Polyaspartic acid (PASP) chelation: The carboxyl (-COOH) and amide (-NHCO-) groups on the PASP molecular chain form stable, water-soluble complexes with calcium, magnesium, and silicon ions (such as Ca²⁺ and SiO colloids) through coordination bonds. For example, each PASP molecule can chelate 3-5 Ca²⁺ ions, blocking their pathway to combine with aluminum ions (Al³⁺) to form precipitates such as CaAl²O⁺.

[0027] Key parameters: PASP molecular weight is controlled between 1000 and 5000 to ensure sufficient steric hindrance and chelating activity.

[0028] Dispersion effect of sorbitol alkylate: Its non-ionic structure adsorbs on the particle surface through multiple hydroxyl groups (-OH), forming a protective film with a thickness of about 5-10nm, generating a spatial repulsive force (theoretical repulsive energy ≥10⁻¹ 9 J), so that the dispersed particles remain in a stable suspended state and prevent re-agglomeration.

[0029] Co-optimization of temperature and time Temperature Effect: At 90°C, the PASP molecular chain movement intensified, and the chelation reaction rate constant k increased to 2.5×10⁻³ s⁻¹ (compared to k=0.8×10⁻³ s⁻¹ at 25°C). At the same time, the surface tension of sorbitol alkylate dropped to 32mN / m (critical micelle concentration CMC=0.05%), and the dispersion efficiency increased by 30%.

[0030] Time effect: When the temperature is kept warm for 20 minutes, more than 95% of the calcium and silicon ions complete the chelation reaction (the kinetic fitting is consistent with the second-order reaction model). Extending the time to 30 minutes only increases the conversion rate by less than 5%, but the energy consumption increases by 15%. Therefore, 20 minutes is the optimal balance point.

[0031] The essence of productivity improvement Reduce the loss of active ingredients: In traditional processes, approximately 18%-25% of the aluminum is encapsulated in calcium-silicon precipitates (e.g., CaSiO₃・Al₂O₃). Dispersants inhibit precipitation, keeping the aluminum in solution. This increases the measured effective aluminum content from 8.5% to 10.6%, corresponding to a 24.7% increase in yield.

[0032] Improved flow and separation efficiency: The dispersant reduces the liquid viscosity (from 5.2mPa·s to 3.8mPa·s), increases the filtration speed by 40%, and reduces the water content of the filter cake from 65% to 55%, indirectly reducing the loss of effective ingredients with the filter cake.

[0033] Working principle of the optimal technical solution Dispersant ratio optimization (2:10) Charge matching: When PASP (negative charge density 0.8e / nm²) is mixed with sorbitol alkylate (neutral hydrophilic head group) in a ratio of 2:10, it forms the best coating (Zeta potential drops from ±30mV to ±10mV) on positively charged Al(OH)3 colloid and negatively charged SiO2 colloid, with the highest stability.

[0034] Synergy: Experiments show that the precipitation inhibition rate reaches 92% under this ratio, which is significantly higher than that of a single component (PASP 78%, sorbitol alkylate 65%).

[0035] Add strategy in segments Add before filtration (0.2%-0.5%): At high solids contents (8%-12% alumina), the dispersant preferentially targets silica gel and soil particles, preventing them from co-precipitating with aluminum ions. At this level, a higher concentration (0.5%) rapidly reduces system viscosity and improves filter press efficiency (flux rate increases from 0.8m³ / h・m² to 1.2m³ / h・m²).

[0036] Add after filtration (0.1%-0.3%): For the nano-scale colloidal particles (diameter <100nm) remaining in the filtrate, low-concentration dispersants prevent secondary agglomeration during storage by replenishing the dispersion layer thickness (from 5nm to 12nm), thereby extending the product shelf life to 6 months (traditional process only 3 months).

[0037] Temperature and color change correlation Restructuring: Heating at 90℃ promotes Al 13 O4(OH) 24 7 The proportion of ⁺ (Keggin structure) increased from 45% to 65%. This structure has a stronger adsorption capacity for negatively charged organic matter (such as humic acid), causing the color to change from light yellow to slightly red (the characteristic absorption peak red-shifted from 420nm to 480nm).

[0038] Improved sludge characteristics: The dispersant changes the crystal form of CaCO3 in the sludge from loose aragonite to dense calcite, increasing the density from 2.6g / cm³ to 2.71g / cm³, reducing the sludge volume by 30% and increasing the sedimentation rate by 50%.

[0039] Detailed workflow Step S1: Filter pressing Operation: In the production process of polyaluminium chloride liquid, the PAC liquid is first subjected to filter press treatment to remove impurities such as silicate and soil.

[0040] Filter pressing is a commonly used solid-liquid separation technology that squeezes liquid from solid particles by applying pressure to achieve the purpose of clarification and purification.

[0041] Purpose: To ensure the effectiveness of the dispersant in subsequent steps and reduce unnecessary interference from precipitation.

[0042] Step S2: Dispersant addition Operation: Depending on the specific situation, add dispersant to the PAC liquid before or after filtration. The amount added before filtration is 0.2%-0.5%, and the amount added after filtration is 0.1%-0.3%.

[0043] Purpose: To reduce the chance of inorganic substances such as calcium and silicon in the liquid combining with aluminum ions to form precipitation through the complexation effect of dispersants.

[0044] Step S3: Heating and heat preservation treatment Operation: Heat the PAC liquid after adding the dispersant to 90℃, keep it warm for 20 minutes and then cool it down.

[0045] Purpose: To ensure that the dispersant fully acts on the inorganic matter in the liquid, reduce precipitation formation, and improve the flocculation effect of the PAC liquid.

[0046] Step S4: Performance testing Operation: Perform performance tests on the treated PAC liquid, including appearance color, alumina content, basicity, sulfate content and COD value.

[0047] Objective: To verify the treatment effect and ensure that the alumina content of the PAC liquid reaches 10.6%, the basicity reaches 52%, the sulfate content is reduced to 0.22%, and the COD value is reduced to 21005 mg / L.

[0048] Step S5: Application testing Operation: Conduct a flow test on the treated PAC liquid to observe its fluidity and the amount of floating mud on the equipment surface.

[0049] Purpose: To evaluate the performance of treated PAC fluid in actual applications, ensuring that it does not easily settle at the bottom of the equipment, has less floating mud on the pump surface, and has a faster flow rate.

[0050] Reference test example: Example 1: PAC liquid before filtration (first batch) 200g of the pre-filtered PAC liquid was added with dispersant at varying ratios (0.05%-0.3%), heated to 90°C for 20 minutes, and then cooled. The results showed that as the amount of dispersant added increased, the amount of precipitation gradually decreased, reaching a significant reduction when the addition reached 0.2%.

[0051] PAC liquid before filtration

[0052] Dispersant (addition ratio as follows in wt%)

[0053] Example 2: PAC liquid after filtration (first batch) Dispersants were added to 300g of the filtered PAC liquid at varying ratios (0.05%-0.5%), heated to 90°C for 20 minutes, and then cooled. The results showed that the addition of the dispersant significantly reduced the amount of precipitation, with the effect being particularly pronounced when the addition reached 0.1% or above.

[0054] Dispersant (addition ratio as follows in wt%):

[0055] Example 3: PAC liquid before filtration (second batch)

[0056] Dispersant (the following dosage ratio is in % by weight)

[0057] Example 4: PAC liquid after filtration (second batch) Dispersant (addition ratio as follows in wt%)

[0058] Example 5: Fluidity and Appearance Changes Flow test of PAC liquid after dispersant treatment: Experimental materials: PAC liquid samples treated with dispersants, and untreated PAC liquid as a control. The appearance color of the PAC liquid treated with dispersants changed slightly from the original light yellow to slightly reddish.

[0059] Experimental equipment: an oxygen pump or similar pump equipment that can simulate liquid transportation, a transparent pipe for observing the flow of liquid, and a container for collecting the outflowing liquid.

[0060] Experimental setup Pipeline Installation: Select a transparent pipe to facilitate observation of the state changes during the flow of liquid. Ensure that the length and diameter of the pipe are suitable for simulating the conditions in the actual application scenario.

[0061] Pump selection and installation: Use an aeration pump or other suitable pumping equipment, setting the flow rate and pressure according to the actual application scenario. Connect the pump to the piping system and ensure a good seal to prevent leakage.

[0062] Experimental operation Initial state record: Before starting the experiment, test the untreated PAC liquid and record its flow conditions in the pipeline, including whether there is obvious sedimentation and whether there is floating mud on the surface of the pump body.

[0063] Test of samples after treatment: Add the PAC liquid treated with dispersant into the pump, start the pump and adjust it to the predetermined working parameters (such as flow rate and pressure).

[0064] Observe the flow of liquid in the pipeline, pay attention to whether there is sediment formation, whether the liquid is clear, whether there is floating mud on the surface of the pump body, etc.

[0065] Regularly check and record experimental data, such as checking the changes in the status of the inner wall of the pipe and the surface of the pump body at regular intervals (for example, every hour).

[0066] Data recording and analysis Flowability evaluation: Evaluate the flowability of the PAC liquid based on observations. Ideally, the treated PAC liquid should exhibit better flowability, be less likely to settle in pipes or at the bottom of equipment, and have less floating mud on the pump surface.

[0067] Comparative Analysis: Compare the performance of treated PAC fluids to untreated samples to analyze the specific improvements brought about by the dispersant treatment.

[0068] Long-term stability test: To further verify the durability of the treatment effect, the experimental period can be extended (for example, running continuously for several days) to observe whether the flow properties of the PAC liquid remain stable over a long period of time.

[0069] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for improving the yield of polyaluminium chloride by using a dispersant, characterized in that: The following steps are involved: In the production process of polyaluminium chloride, filter pressing is first carried out to remove silicate and soil impurities; adding a dispersant to the polyaluminium chloride liquid; After adding the dispersant, keep the mixture at 85-95℃ for 15-30 minutes and then cool it down.

2. The method for improving the yield of polyaluminium chloride by using a dispersant according to claim 1, wherein: The dispersant is a mixture of polyaspartic acid and sorbitol alkylate, and the ratio of the mixture is 2:

10.

3. The method for improving the yield of polyaluminium chloride by using a dispersant according to claim 2, wherein: The amount of the dispersant added is 0.1%-0.5% of the weight of the polyaluminium chloride liquid.

4. The method for improving the yield of polyaluminium chloride by using a dispersant according to claim 3, wherein: The dispersant is added before or after the polyaluminium chloride liquid is filtered.

5. The method for improving the yield of polyaluminium chloride by using a dispersant according to claim 4, wherein: The amount of the dispersant added before the polyaluminium chloride liquid is filtered is 0.2%-0.5%, and the amount of the dispersant added after the polyaluminium chloride liquid is filtered is 0.1%-0.3%.

6. The method for improving the yield of polyaluminium chloride by using a dispersant according to claim 5, wherein: The optimal heating temperature of the polyaluminium chloride liquid after adding the dispersant is 90°C, and the optimal insulation time is 20 minutes.

7. The method for improving the yield of polyaluminium chloride by using a dispersant according to claim 6, wherein: After the polyaluminium chloride liquid is treated with a dispersant, its appearance color changes from original light yellow to slightly red, and the sludge at the bottom is deposited and not loose.

8. The method for improving the yield of polyaluminium chloride by using a dispersant according to claim 6, wherein: After adding the dispersant, the aluminum oxide content of the polyaluminum chloride liquid reaches 10.6%, the basicity reaches 52%, the sulfate content is reduced to 0.22%, and the COD value is reduced to 21005 mg / L.

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