Polymeric aluminum ferric chloride flocculant and its preparation process

Abstract

The present application belongs to the technical field of polymeric aluminum ferric chloride, and particularly relates to a polymeric aluminum ferric chloride flocculant, which comprises fly ash, acid liquor, an activator, a pore-forming agent and an alkalizing agent, and also relates to a preparation process thereof, which comprises preparing activated fly ash, acid leaching fly ash, estimating the amount of alkalizing agent, polymerization, curing and drying. In the present application, the salt base degree is used to replace the traditional pH value as the end point control criterion, so as to ensure the reliable and consistent performance of the product. In the curing stage, a vertical internal circulation curing tank is used, and the internal circulation of the material is formed by means of the built-in sleeve and the multi-stage layered stirring mechanism, and the curing time is shortened from 18-24 hours to 2-4 hours by cooperating with the heat preservation jacket. The cutting stirring rod and the screw pushing paddle are used to shear and disperse cooperatively, so as to prevent local over-aggregation and ensure the uniform distribution of the molecular weight. In the drying stage, the pore-forming agent is added to make the solid product have a porous and loose structure, so that the flocculation effect time is significantly shortened and the flocculation effect is not affected.

Description

Technical Field

[0001] This invention belongs to the field of polyaluminum ferric chloride technology, specifically relating to a polyaluminum ferric chloride flocculant and its preparation process. Background Technology

[0002] Polyaluminum ferric chloride (PAFC), as an inorganic polymeric composite flocculant, combines the excellent charge neutralization ability of aluminum-based flocculants with the strong adsorption bridging ability and fast settling speed of iron-based flocculants, making it widely used in the treatment of wastewater from coal washing, dyeing and printing, and municipal sewage. Current methods for preparing PAFC mainly use pure chemical reagents aluminum chloride and ferric chloride as raw materials, directly synthesizing them through a hydrolysis-polymerization reaction. While this method produces stable products, the high cost of raw materials limits its application in large-scale water treatment.

[0003] In existing technologies, the aging process of polyaluminum ferric chloride generally employs intermittent aging or slow stirring during static conditions. This process typically takes 18 to 24 hours, resulting in low production efficiency. More importantly, significant differences in temperature and concentration occur in different regions of the reactor, leading to a wide distribution of polymer molecular weight. Some regions experience localized overpolymerization, forming gels or precipitates, while other regions exhibit insufficient polymerization. This inhomogeneity directly causes large fluctuations in basicity and flocculation performance between product batches and even between different portions of the same batch, severely impacting the consistency and reliability of product quality.

[0004] Furthermore, existing maturation processes lack precise control over the final basicity. Traditional methods often rely on the initial feed ratio or the pH value at the end of the reaction as the basis for control. However, there is no fixed linear relationship between pH value and actual basicity, especially in solid waste acid leaching systems with large compositional fluctuations. This error is more pronounced, making it difficult to guarantee stable product performance even when following the same operating procedures. In the drying stage, solid PAFC products produced by existing technologies generally suffer from slow dissolution rates. Directly dried block products have a dense structure and require prolonged stirring in water to dissolve, resulting in a long flocculation time. Summary of the Invention

[0005] To address the problems existing in the prior art, the present invention provides a polyaluminum ferric chloride flocculant and its preparation process, which can improve the stability of polyaluminum ferric chloride product quality and increase the product's dissolution rate in water.

[0006] The specific technical solution adopted in this invention is as follows: A polyaluminum ferric chloride flocculant comprises 100 parts fly ash, 400-600 parts acid solution, 80-100 parts activator, 1-5 parts pore-forming agent, and alkalizing agent.

[0007] The acid solution is 15% hydrochloric acid by mass, the activator is sodium carbonate, the pore-forming agent is polyethylene glycol, and the alkalizing agent is a 15% sodium hydroxide aqueous solution.

[0008] A preparation process for a polyaluminum ferric chloride flocculant, comprising the following preparation steps: S1: Add an activator to fly ash, heat to 800-900℃ for calcination and activation for 2 hours, and cool to room temperature to obtain activated fly ash; S2: Add acid to activated fly ash, heat to 75-80℃ and stir for 110-130 min, separate solid and liquid, temporarily store filter cake, and obtain 300-400 parts of filtrate; S3: Filtrate Detection Al 3+ Concentration and Fe 3+ Concentration: The amount of substance of ions is calculated based on the ion concentration and the volume of filtrate, and finally the amount of alkalizing agent to be added is estimated based on the amount of substance of ions. S4: Control the temperature at 0-50℃, add the alkalizing agent to the filtrate in batches, and take a sample to test the basicity after each batch of alkalizing agent is added. Control the basicity to reach 60%-70%, raise the temperature to 80-90℃, and keep it at this temperature while stirring for 2.5-3.5 hours. S5: Add pore-forming agent to the reaction solution, stir and control the temperature to 70-80℃, and slowly stir and mature for 2-4 hours; S6: After ripening, spray drying is performed to obtain the finished product.

[0009] In step S2, the stirring speed is 40-60 r / min.

[0010] In step S3, sampling and testing are performed under stirring conditions, with a stirring speed of 40-60 r / min.

[0011] The formula for calculating the amount of substance of the ions is: i is Al 3+ or Fe 3+ , This represents the amount of substance of the ions. Let be the molar concentration of the ions, and v be the volume. This represents the relative molecular mass of the ion; The mass of the alkalizing agent The calculation formula is: B represents basicity. This represents the relative molecular weight of the alkalizing agent. This represents the mass concentration of the alkalizing agent.

[0012] In step S4, the alkalizing agent is added in equal parts of 5 portions. After each portion is added, the mixture is stirred for 15 minutes before adding the next portion, until the basicity reaches 60%-70%. The basicity B is used as the endpoint criterion, and the pH value is used as an auxiliary criterion, with the pH value being 2.5-3.5.

[0013] In step S5, the maturation step is achieved through a vertical internal circulation maturation tank. The vertical internal circulation maturation tank includes an outer tank and an inner sleeve. The top of the outer tank is provided with a feed inlet that connects to the inside of the inner sleeve, and the bottom is provided with a discharge outlet. The side wall is provided with a heat-insulating jacket. The inner sleeve is coaxially fixedly installed inside the outer tank, and the inner sleeve is a through-type vertical cylindrical structure. The inner sleeve is provided with a multi-stage layered stirring mechanism, which includes a partition plate, a cutting stirring rod, and a spiral pusher. Multiple partition plates are arranged vertically and vertically inside the inner sleeve, and several through-type material flow holes are opened on the plates. A cutting stirring rod is arranged adjacent to the lower surface of each partition plate, and a spiral pusher is arranged between the cutting stirring rod and the next partition plate. The inner wall of the outer tank and the outer wall of the inner sleeve form a reflux cavity.

[0014] It also includes a central spindle that runs through the entire vertical internal circulation maturation tank, with a rotary drive device connected to the top of the central spindle; the cutting and stirring rod and the spiral pusher are both fixedly installed on the central spindle and rotate synchronously with the central spindle.

[0015] The bottom of the outer tank is provided with an integrally formed conical head. When the material flows to the bottom of the inner sleeve and merges into the return cavity, the inclined surface of the conical head guides the flow and reduces the resistance to material backflow.

[0016] The beneficial effects of this invention are: This invention uses industrial solid waste fly ash as raw material and extracts aluminum and iron from it through an activation roasting-acid leaching process, significantly reducing the production cost of polyaluminum ferric chloride while realizing the resource utilization of solid waste. During the reaction stage, this invention uses basicity as the core criterion for endpoint control, rather than relying solely on pH value as in traditional processes, ensuring that the product basicity is precisely controlled within the target range, resulting in reliable and consistent product performance.

[0017] During the curing stage, this invention employs a vertical internal circulation curing tank. Through an internal sleeve and a multi-stage layered stirring mechanism, the material circulates within the tank, ensuring uniform curing distribution. Combined with an insulation jacket, this reduces the curing time from the traditional 18-24 hours to 2-4 hours, significantly improving production efficiency. Furthermore, the vertical internal circulation curing tank, through the cooperation of a cutting stirring rod and a spiral pusher, continuously shears and disperses polymer clumps during material circulation, effectively preventing localized over-polymerization and gel formation, thus ensuring uniform molecular weight distribution and stable batch quality.

[0018] In addition, solid products prepared by traditional drying processes have the disadvantages of slow dissolution and long flocculation onset time. This invention adds a pore-forming agent to make the solid product have a porous and loose structure, which can be quickly dissolved and dispersed when it comes into contact with water, significantly shortening the flocculation onset time without affecting the flocculation effect. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the preparation process of the present invention; Figure 2 This is a schematic diagram of a vertical internal circulation curing tank. In the attached diagram, 1 is the outer tank, 101 is the inlet, 102 is the outlet, 2 is the inner sleeve, 201 is the partition plate, 202 is the cutting and stirring rod, 203 is the spiral pusher, 3 is the reflux cavity, and 4 is the conical head. Detailed Implementation

[0020] The present invention will be further described below with reference to the accompanying drawings and specific embodiments: Example 1 The preparation of a polyaluminum ferric chloride flocculant includes the following steps: S1: Add 80 parts of activator to 100 parts of fly ash, heat to 850℃±5℃ for calcination and activation for 2 hours, and cool to room temperature to obtain activated fly ash; S2: Add 500 parts of 15% hydrochloric acid to activated fly ash, set the stirring speed to 50 r / min, heat to 75-80℃ and react for 120 min, separate solid and liquid to obtain 328 parts of filtrate; temporarily store the filter cake, the main component of the filter cake is silicon dioxide, which is used to prepare by-product white carbon black or synthesize zeolite molecular sieves.

[0021] S3: Filtrate Detection Al 3+ Concentration and Fe 3+ Concentration was measured by sampling under stirring conditions at a speed of 50 r / min. Al was detected. 3+ The concentration was 15.4 parts / L, Fe 3+ With a concentration of 13.8 parts / L and a basicity of 67% as the standard, the formula calculates that 48 parts of a 15% sodium hydroxide aqueous solution should be added.

[0022] The formula for calculating the amount of substance of the ions is: i is Al 3+ or Fe 3+ , This represents the amount of substance of the ions. Let be the molar concentration of the ions, and v be the volume. This represents the relative molecular mass of the ion; The mass of the alkalizing agent The calculation formula is: S4: Control the temperature at 0-50℃, add the alkalizing agent to the filtrate in 5 batches. After each batch of alkalizing agent is added, stir for 15 minutes and take a sample to test the basicity before adding the next batch of alkalizing agent, until the basicity is controlled to reach 60%-70%. The final basicity is 65%, the pH is 2.8, raise the temperature to 85℃±2℃, and keep it at this temperature with stirring for 3 hours. S5: Add 2 parts of pore-forming agent to the reaction solution, stir and control the temperature to 70-80℃, and slowly stir and mature for 3 hours; S6: After ripening, spray drying is performed to obtain the finished product.

[0023] Example 2 The difference between Example 2 and Example 1 lies only in the addition of 90 parts of activator and 400 parts of 15% hydrochloric acid, resulting in 296 parts of filtrate. The Al³⁺ concentration was measured to be 14.6 parts / L and the Fe³⁺ concentration to be 12.3 parts / L. Calculations indicate that approximately 40 parts of 15% sodium hydroxide aqueous solution should be added to achieve a final basicity of 60%. Example 3 The difference between Example 3 and Example 1 lies only in the addition of 100 parts of activator and 600 parts of 15% hydrochloric acid, resulting in 503 parts of filtrate. The Al³⁺ concentration was measured to be 16 parts / L and the Fe³⁺ concentration to be 15.5 parts / L. Calculations indicate that approximately 78 parts of 15% sodium hydroxide aqueous solution should be added to achieve a final basicity of 70%. In summary, the basicity of the final product in Example 1 reached 65%, which is the middle value of the optimal range, while the basicities of Examples 2 and 3 were at the upper and lower limits of the optimal range, respectively.

[0024] As basicity increases, the degree of hydrolysis and polymerization of aluminum and iron ions deepens. Increased basicity leads to a higher molecular weight of polyaluminum ferric chloride (PAFC), forming more long-chain, network-like high-polymerization structures. This chain-network structure tends to be stable and carries a higher positive charge, thus enhancing the product's charge neutralization and adsorption bridging / encapsulation sweeping capabilities, ultimately improving the flocculation effect. However, if basicity continues to increase beyond the upper limit of the optimal range, excessively high basicity means too many hydroxyl groups in the system. This promotes high polymerization of aluminum and iron ions, forming precipitates such as aluminum hydroxide and ferric hydroxide, instead of high-molecular-weight complexes with flocculation activity. The formation of these precipitates directly reduces the charge neutralization and encapsulation capabilities of PAFC, thereby decreasing the flocculation effect. Therefore, the preparation scheme in Example 1 is the optimal scheme.

[0025] A pore-forming agent is added before curing and pumped into a vertical internal circulation curing tank. This ensures the pore-forming agent is evenly dispersed in the material, and the curing temperature of 70-80℃ poses no risk of decomposition to the agent. After curing, the material enters the drying stage via spray drying. During spray drying, polyethylene glycol decomposes or melts and volatilizes upon heating, transforming its original positions into pores, thus acting as a pore-forming agent. The spray drying process is very fast (milliseconds), and polyethylene glycol decomposes or volatilizes upon heating, creating pores. These pores make the final solid particles loose and porous. The increased surface area of ​​the solid particles allows water to penetrate into the particles through capillary action, dissolving faster than in solid particles. These pores persist after dissolution, providing numerous additional physical trapping sites for subsequent flocculation. Therefore, the appropriate addition of polyethylene glycol not only does not affect flocculation but also enhances the sweeping and trapping ability of small particles by utilizing its physical structure.

[0026] Furthermore, such as Figure 2 As shown, in step S5, the maturation step is achieved through a vertical internal circulation maturation tank. The vertical internal circulation maturation tank includes an outer tank 1 and an inner sleeve 2. The top of the outer tank 1 is provided with a feed inlet, which connects to the inside of the inner sleeve 2. The bottom is provided with a discharge outlet, and the side wall is provided with a heat-insulating jacket. The inner sleeve 2 is coaxially fixedly installed inside the outer tank 1. The inner sleeve 2 is a through-type vertical cylindrical structure. The inner sleeve 2 is provided with a multi-stage layered stirring mechanism. The multi-stage layered stirring mechanism includes a partition plate, a cutting stirring rod, and a spiral pusher. Multiple partition plates are arranged vertically and horizontally within the inner sleeve 2. Several through-type material flow holes are opened on the plate body. A cutting stirring rod is arranged adjacent to the lower surface of each partition plate. A spiral pusher is arranged between the cutting stirring rod and the next partition plate. The inner wall of the outer tank 1 and the outer wall of the inner sleeve 2 form a reflux cavity.

[0027] Two parts polyethylene glycol are added to the material and mixed thoroughly before being pumped into a vertical internal circulation curing tank. The mixture enters the inner sleeve 2 through the inlet and flows downwards through the through-holes of the first partition plate under gravity. As it passes the cutting and stirring rods, the material flowing out of the holes is sheared, dispersed, and homogenized. It then flows downwards past the spiral pusher, whose rotation generates a downward axial pushing force, driving the material from this layer into the next layer, until it reaches the bottom layer. Due to the continuous pushing of the spiral pusher, the material overflows upwards from the bottom layer, exiting the inner sleeve 2 and flowing into the return cavity. It then overflows back into the inner sleeve 2 from the top, forming an internal material circulation system that ensures uniform heating and curing.

[0028] Furthermore, such as Figure 2As shown, the vertical internal circulation maturation tank also includes a central main shaft, which runs through the entire vertical internal circulation maturation tank, and a rotary drive device is connected to the top of the central main shaft; the cutting and stirring rod and the spiral pusher are both fixedly installed on the central main shaft and rotate synchronously with the central main shaft.

[0029] During operation, the rotary drive unit rotates the central spindle, which synchronously transmits power to the cutting and stirring rods and the spiral pusher paddles at each layer. As the cutting and stirring rods rotate, they shear and disperse the material flowing from the holes in the partition plate, eliminating clumping and homogenizing the material. The rotating spiral pusher paddles generate a downward axial thrust, continuously pushing the material from one layer to the next. Because all the cutting and stirring rods and spiral pusher paddles are mounted on the same central spindle, the stirring and pushing actions at each layer are synchronized, ensuring that the material receives uniform shearing and pushing force as it falls layer by layer, thus guaranteeing the uniformity of the overall maturation effect.

[0030] Furthermore, such as Figure 2 As shown, the bottom of the outer tank 1 is provided with an integrally formed conical head. When the material flows to the bottom of the inner sleeve 2 and merges into the return cavity, the inclined surface of the conical head guides the flow and reduces the resistance of the material return flow.

[0031] The conical head utilizes the gradual transition of the inclined surface to transform the original vertical downward flow of materials, which required a sharp turn, into an outward flow along the inclined surface. This avoids the large flow resistance and dead zone caused by the sudden reversal of materials at the right-angle corner at the bottom, thereby reducing the energy loss of the material reversal flow, making the internal circulation flow smoother, and also reducing the risk of material deposition and agglomeration at the bottom.

Claims

1. A polyaluminum ferric chloride flocculant, characterized in that: It includes 100 parts fly ash, 400-600 parts acid solution, 80-100 parts activator, 1-5 parts pore-forming agent, and alkalizing agent.

2. The polyaluminum ferric chloride flocculant according to claim 1, characterized in that: The acid solution is 15% hydrochloric acid by mass, the activator is sodium carbonate, the pore-forming agent is polyethylene glycol, and the alkalizing agent is a 15% aqueous solution of sodium hydroxide.

3. A preparation process for a polyaluminum ferric chloride flocculant, used to prepare the polyaluminum ferric chloride flocculant as described in claim 1, characterized in that: The preparation steps include the following: S1: Add an activator to fly ash, heat to 800-900℃ for calcination and activation for 2 hours, and cool to room temperature to obtain activated fly ash; S2: Add acid to activated fly ash, heat to 75-80℃ and stir for 110-130 min, separate solid and liquid, temporarily store filter cake, and obtain 300-400 parts of filtrate; S3: Filtrate Detection Al 3+ Concentration and Fe 3+ Concentration: The amount of substance of ions is calculated based on the ion concentration and the volume of filtrate, and finally the amount of alkalizing agent to be added is estimated based on the amount of substance of ions. S4: Control the temperature at 0-50℃, add the alkalizing agent to the filtrate in batches, and take a sample to test the basicity after each batch of alkalizing agent is added. Control the basicity to reach 60%-70%, raise the temperature to 80-90℃, and keep it at this temperature while stirring for 2.5-3.5 hours. S5: Add pore-forming agent to the reaction solution, stir and control the temperature to 70-80℃, and slowly stir and mature for 2-4 hours; S6: After ripening, spray drying is performed to obtain the finished product.

4. The preparation process according to claim 3, characterized in that: In step S2, the stirring speed is 40-60 r / min.

5. The preparation process according to claim 3, characterized in that: In step S3, sampling and testing are performed under stirring conditions, with a stirring speed of 40-60 r / min. The formula for calculating the amount of substance of the ions is: i is Al 3+ or Fe 3+ , This represents the amount of substance of the ions. Let be the molar concentration of the ions, and v be the volume. This represents the relative molecular mass of the ion; The mass of the alkalizing agent The calculation formula is: B represents basicity. This represents the relative molecular weight of the alkalizing agent. This represents the mass concentration of the alkalizing agent.

6. The preparation process according to claim 3, characterized in that: In step S4, the alkalizing agent is added in 5 equal parts. After each part is added, the mixture is stirred for 15 minutes before adding the next part, until the basicity reaches 60%-70%. The basicity B was used as the endpoint criterion, with pH value as a secondary criterion, and the pH range was 2.5-3.

5.

7. The preparation process according to claim 3, characterized in that: In step S5, the maturation step is achieved through a vertical internal circulation maturation tank. The vertical internal circulation maturation tank includes an outer tank (1) and an inner sleeve (2). The top of the outer tank (1) is provided with a feed inlet (101), which is connected to the inside of the inner sleeve (2). The bottom is provided with a discharge outlet (102), and the side wall is provided with a heat-insulating jacket. The inner sleeve (2) is coaxially fixedly installed inside the outer tank (1). The inner sleeve (2) is a through-type vertical cylindrical structure. The inner sleeve (2) is provided with a multi-stage layered stirring mechanism. The multi-stage layered stirring mechanism includes a partition plate (201), a cutting stirring rod (202), and a spiral pusher (203). The partition plate (201) has multiple partition plates arranged vertically and vertically within the inner sleeve (2). The plate body has several through-type material flow holes. The lower surface of each partition plate is provided with a cutting stirring rod (202) adjacent to it. The spiral pusher (203) is provided between the cutting stirring rod (202) and the next partition plate (201). The inner wall of the outer tank (1) and the outer wall of the inner sleeve (2) form a reflux cavity (3).

8. The preparation process according to claim 7, characterized in that: It also includes a central spindle that runs through the entire vertical internal circulation maturation tank, with a rotary drive device connected to the top of the central spindle; the cutting and stirring rod (202) and the spiral pusher (203) are both fixedly installed on the central spindle and rotate synchronously with the central spindle.

9. The preparation process according to claim 7, characterized in that: The bottom of the outer tank (1) is provided with an integrally formed conical head (4). When the material flows to the bottom of the inner sleeve (2) and merges into the return cavity (3), the flow resistance of the material return is reduced by the inclined surface of the conical head (4).

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