Composite flocculant as well as preparation method and application thereof in sludge dewatering

Abstract

The invention discloses a composite flocculant as well as a preparation method and application thereof in sludge dewatering, and belongs to the technical field of flocculants.The composite flocculant is prepared from the following raw materials in parts by mass: 500 parts of a polyaluminum chloride solution, 100-200 parts of ferric sulfate, 1-1.5 parts of a stabilizer and 5-15 parts of a poly dimethyl diallyl ammonium chloride solution; the stabilizer comprises ammonium sulfate; the viscosity of the poly dimethyl diallyl ammonium chloride solution is 0.5 to 1 dL / g. The polyaluminum chloride solution with the aluminum oxide content of 10-15 wt% and the polymerization degree of 10-45% is used as a matrix, under the combined action of the ferric sulfate, the stabilizer and the poly dimethyl diallyl ammonium chloride solution, the composite flocculant with the excellent flocculation effect and stability is obtained, and the composite flocculant has the excellent dehydration efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of flocculants, and particularly relates to a composite flocculant, a preparation method thereof, and an application thereof in sludge dewatering. Background Art

[0002] By incorporating different groups into polyaluminum chloride liquid, polyaluminum chloride composite products with better coagulation performance can be obtained. For example, by incorporating sulfate anions, polyaluminum sulfochloride with sulfate coordination groups is prepared, and its coagulation performance is better than that of polyaluminum chloride. By incorporating ferric ions, polyaluminum chloride ferric is prepared, and its coagulation performance is also better than that of polyaluminum chloride. However, polyaluminum sulfochloride or polyaluminum chloride ferric liquid prepared by incorporating aluminum sulfate or ferric chloride into polyaluminum chloride liquid is unstable.

[0003] By incorporating active silica into polyaluminum chloride, polyaluminum silicate chloride is prepared, and its use effect is also significantly better than that of polyaluminum chloride. Similarly, the stability of the liquid product after adding silicon to the polyaluminum chloride liquid product is also poor. In addition, incorporating cationic electrolytes with high cationic charge density into polyaluminum chloride liquid products is also an important way to improve the coagulation performance of polyaluminum chloride.

[0004] In view of this, the present application is proposed. Summary of the Invention

[0005] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a composite flocculant, a preparation method thereof, and an application thereof in sludge dewatering. The composite flocculant has excellent flocculation effect and stability, and the composite flocculant has excellent dewatering efficiency.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is as follows: A composite flocculant, comprising the following raw materials in parts by mass: 500 parts of polyaluminum chloride solution, 100 - 200 parts of ferric sulfate, 1 - 1.5 parts of stabilizer, 5 - 15 parts of polydimethyldiallylammonium chloride solution; The stabilizer includes ammonium sulfate; The viscosity of the polydimethyldiallylammonium chloride solution is 0.5 - 1 dL / g; The alumina content of the polyaluminum chloride solution is 10 - 15 wt%, and the degree of polymerization is 10 - 45%.

[0007] The inventor of the present invention found in a large number of studies that incorporating commercially available polydimethyldiallylammonium chloride into polyaluminum chloride products and using them as liquid products indeed have better effects than polyaluminum chloride. However, when spray-dried, the coagulation effect of the obtained products is very poor. The inventor speculated that polydimethyldiallylammonium chloride has a high cationic charge density, resulting in the destruction of the synergistic effect of the obtained products, and even an antagonistic effect, leading to a decrease in the coagulation effect.

[0008] Therefore, based on the above problems, the present application creatively combines the above raw materials, using a polyaluminum chloride solution with an alumina content of 10 - 15 wt% and a polymerization degree of 10 - 45% as the matrix, and under the combined action of ferric sulfate, a stabilizer, and a polydimethyldiallylammonium chloride solution, a composite flocculant with excellent flocculation effect and stability is obtained. The composite flocculant has excellent dehydration efficiency.

[0009] The present invention introduces sulfate ions and iron ions into the polyaluminum chloride solution to make it an aluminum - iron product containing sulfate ions, improving the product structure. On this basis, a stabilizer is added to solve the problem of poor stability of the poly - sulfur - aluminum - iron chloride solution, so that the poly - sulfur - aluminum - iron chloride solution will not stratify after being placed for one month, effectively solving the problem of instability of the liquid product with added sulfate ions. Then, a polydimethyldiallylammonium chloride solution with a viscosity of 0.5 - 1 dL / g is added, increasing the positive charge density of the product and improving the electro - neutralization ability of the product. Most importantly, the solid composite coagulant product obtained after spray drying is still easily soluble in water, has good coagulation effect, is especially suitable for sludge dewatering conditioning, and has excellent dehydration efficiency.

[0010] When the composite coagulant of the present invention is used for sludge dewatering conditioning, only one kind of agent is needed for conditioning. The dehydration efficiency is better than that of the traditional conditioning effects of two agents, namely polyaluminum chloride (or polyferric sulfate) and polyacrylamide, which can meet the requirements of users for deep - dehydration conditioning. It is convenient to use, can be sold locally, and because the solid product can be transported over long distances, it is also very suitable for off - site sales and even export sales. The comprehensive cost - performance ratio of the product is good, and it has excellent market competition conditions.

[0011] As a preferred embodiment of the present invention, the preparation raw materials include the following parts by mass: 500 parts of polyaluminum chloride solution, 130 - 184 parts of ferric sulfate, 1.1 - 1.4 parts of stabilizer, and 6 - 14 parts of polydimethyldiallylammonium chloride solution. Especially when the dosages of the raw materials are controlled within this range, the synergistic effect is more obvious, which can be more suitable for sludge dewatering and improve the dehydration efficiency.

[0012] As a preferred embodiment of the present invention, the preparation raw materials include the following parts by mass: 500 parts of polyaluminum chloride solution, 150 - 170 parts of ferric sulfate, 1.2 - 1.3 parts of stabilizer, and 7.5 - 12.5 parts of polydimethyldiallylammonium chloride solution. Especially when the dosages of the raw materials are controlled within this range, the synergistic effect is more obvious, which can be more suitable for sludge dewatering and improve the dehydration efficiency.

[0013] As a preferred embodiment of the present invention, the alumina content of the polyaluminum chloride solution is 12-14 wt%, the degree of polymerization is 20-30%, and the polyaluminum chloride solution does not contain calcium element. In particular, when using a polyaluminum chloride solution with an alumina content of 12-14 wt% and a degree of polymerization of 20-30%, it has a better flocculation effect, better compatibility in the system, more obvious synergistic effect, and can more effectively improve the dehydration efficiency.

[0014] As a preferred embodiment of the present invention, the mass ratio of the sum of the masses of the polyaluminum chloride solution and ferric sulfate to the mass of the poly(dimethyldiallylammonium chloride) solution is (40-140):1. The inventors of the present invention have found that the mass ratio of the sum of the masses of the polyaluminum chloride solution and ferric sulfate to the mass of the poly(dimethyldiallylammonium chloride) solution has a great influence on the dehydration effect. By controlling the mass ratio of the sum of the masses of the polyaluminum chloride solution and ferric sulfate to the mass of the poly(dimethyldiallylammonium chloride) solution within this range, the dehydration efficiency is effectively improved.

[0015] As a preferred embodiment of the present invention, the preparation method of the poly(dimethyldiallylammonium chloride) solution includes the following steps: Add a dimethyldiallylammonium chloride solution with a concentration of 38-42 wt% to the reaction kettle, continuously introduce an inert gas into the reaction kettle for 5-15 min, add ammonium persulfate, react at 40-44 °C for 0.5-1.5 h, raise the temperature to 45-55 °C, react for 1-3 h, then raise the temperature to 60-70 °C, react for 2-3 h, and then cool to obtain a poly(dimethyldiallylammonium chloride) solution; The mass ratio of the dimethyldiallylammonium chloride solution to ammonium persulfate is 1:(0.001-0.0015).

[0016] The present invention adopts the above specific method to prepare a poly(dimethyldiallylammonium chloride) solution with a viscosity of 0.5-1 dL / g. The poly(dimethyldiallylammonium chloride) solution is particularly suitable for the system of the present invention and can balance water solubility and coagulation performance. When the viscosity is too low, the coagulation effect will decrease significantly. When the viscosity is too high, the stability of the obtained product will decrease, and the solubility in water will also decrease, resulting in a significant decrease in the dehydration effect.

[0017] It should be noted that by controlling the polymerization time of the dimethyldiallylammonium chloride solution and the later reaction temperature, the viscosity of the poly(dimethyldiallylammonium chloride) solution can be changed.

[0018] As a preferred embodiment of the present invention, the preparation method of the polyaluminum chloride solution includes the following steps: Add a hydrochloric acid solution with a concentration of 20 - 30 wt% to the reaction kettle, continuously introduce an inert gas into the reaction kettle for 5 - 15 min, add deammoniated aluminum ash, react at 100 - 105 °C for 180 - 240 min, add a sodium sulfide solution, stir evenly, filter, and obtain a polyaluminum chloride solution; The mass ratio of the hydrochloric acid solution, deammoniated aluminum ash, and sodium sulfide solution is (2.8 - 3):1:(0.2 - 0.4).

[0019] It should be noted that in this application, by changing the amount of deammoniated aluminum ash used and the reaction time, the alumina content and the degree of polymerization are further changed.

[0020] The present invention uses inexpensive aluminum ash to prepare a calcium-free polyaluminum chloride solution, with less waste residue and low raw material cost. Using sodium sulfide as a heavy metal removal agent not only solves the problem of heavy metal impurity interference but also solves the problem of heavy metal exceeding the standard in the production using aluminum ash as a raw material. At the same time, the dehydration effect of the prepared polyaluminum chloride solution is further improved.

[0021] As a preferred embodiment of the present invention, the mass fraction of the sodium sulfide solution is 8 - 12%.

[0022] The present invention also provides a preparation method of a composite flocculant, including the following steps: Mix the polyaluminum chloride solution, ferric sulfate, and stabilizer evenly, then add a polydimethyldiallylammonium chloride solution, stir evenly, and spray dry to obtain a composite flocculant.

[0023] As a preferred embodiment of the present invention, the temperature of the spray drying is 200 - 260 °C.

[0024] The present invention also provides an application of the composite flocculant in sludge dewatering.

[0025] The beneficial effects of the present invention are as follows: (1) Based on a polyaluminum chloride solution with an alumina content of 10 - 15 wt% and a degree of polymerization of 10 - 45%, under the combined action of ferric sulfate, stabilizer, and polydimethyldiallylammonium chloride solution, a composite flocculant with excellent flocculation effect and stability is obtained, and the composite flocculant has excellent dehydration efficiency.

[0026] (2) In the present invention, sulfate ions and iron ions are introduced into the polyaluminum chloride solution to form an aluminum-iron product containing sulfate ions, which improves the product structure. On this basis, a stabilizer is added to solve the problem of poor stability of the polyaluminum ferric chloride solution. As a result, the polyaluminum ferric chloride solution will not stratify even after being placed for one month, effectively solving the problem of instability of the liquid product containing sulfate ions. Then, a poly(dimethyldiallylammonium chloride) solution with a viscosity of 0.5 - 1 dL / g is incorporated, increasing the positive charge density of the product and enhancing its electro-neutralization ability. Most importantly, the solid composite coagulant product obtained after spray drying is still easily soluble in water and has good coagulation effect, especially suitable for sludge dewatering conditioning and having excellent dewatering efficiency.

[0027] (3) When the composite coagulant of the present invention is used for sludge dewatering conditioning, only one kind of agent is needed for conditioning, and its dewatering efficiency is better than that of the traditional conditioning effects of two agents, namely polyaluminum chloride (or polyferric sulfate) and polyacrylamide. It can meet the requirements of users for deep dewatering conditioning, is convenient to use, can be sold locally, and because the solid product can be transported over long distances, it is also very suitable for off-site sales and even export sales. The product has good comprehensive cost performance and excellent market competition conditions.

[0028] (4) The composite coagulant of the present invention is suitable for large-scale industrial production, and has very important practical significance for promoting the development of the polyaluminum chloride industry and enhancing the international market competitiveness of polyaluminum chloride industry enterprises. Description of the Drawings

[0029] Figure 1 It is a diagram of the mixed solution and the poly(dimethyldiallylammonium chloride) solution prepared in Example 1 of the present invention. Detailed Embodiments

[0030] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below. Apparently, the described embodiments are some, but not all, of the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of the present application.

[0031] In the present application, among the technical features described in an open-ended manner, there are included closed technical solutions composed of the listed features, as well as open technical solutions containing the listed features.

[0032] In this application, when it comes to numerical ranges, unless otherwise specified, the above numerical ranges are considered continuous and include the minimum and maximum values of the range, as well as each value between such minimum and maximum values. Further, when the range refers to integers, it includes each integer between the minimum and maximum values of the range. In addition, when multiple ranges are provided to describe features or characteristics, the ranges can be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all sub-ranges subsumed therein.

[0033] In this application, there are no particular restrictions on the specific dispersion and stirring treatment methods.

[0034] Unless otherwise specified, the component raw materials or instruments used in the embodiments and comparative examples of the present invention are all commercially available raw materials or instruments, and the component raw materials used in each parallel experiment are of the same kind.

[0035] The following examples are provided to facilitate the understanding of the present invention. These examples are not provided to limit the scope of the claims.

[0036] Example 1 A method for preparing a composite flocculant, comprising the following steps: (1) Add 3 kg of hydrochloric acid with a concentration of 20 wt% to a 5 L reaction kettle, then introduce nitrogen for 15 minutes to remove oxygen. Under stirring, add 1 kg of deammoniated aluminum ash, control the reaction temperature at 100 °C for atmospheric pressure reaction, and the reaction time is 240 minutes. After the reaction, introduce 0.3 kg of a sodium sulfide liquid with a concentration of 10% (wt%) into the reaction kettle, and continue stirring for 30 minutes to convert heavy metal ions such as calcium ions, chromium ions, lead ions, and nickel ions into sulfide precipitates. Then filter to obtain a polyaluminum chloride solution with an alumina content of 14% (wt%) and a polymerization degree of 30%.

[0037] (2) First, add 3 kg of a dimethyldiallylammonium chloride solution with a concentration of 40 wt% to a 5 L reaction kettle, then continuously introduce an inert gas into the reaction kettle for 15 minutes. Then, under stirring, add 4 g of ammonium persulfate. After reacting at 44 °C for 1.0 h, adjust the temperature to 50 °C and continue the reaction for 2 h. Then raise the temperature to 60 °C and react for 2 h. After cooling, obtain a poly(dimethyldiallylammonium chloride) solution with a viscosity of 0.5 dL / g (concentration of 40 wt%).

[0038] (3) Weigh the following raw materials according to the mass ratio: 500 parts of polyaluminum chloride solution, 200 parts of ferric sulfate, 1.5 parts of ammonium sulfate, and 5 parts of poly(dimethyldiallylammonium chloride) solution; Among them, the mass ratio of the sum of the masses of the polyaluminum chloride solution and ferric sulfate to the mass of the poly(dimethyldiallylammonium chloride) solution is 140:1; (4) Add the polyaluminum chloride solution into the reaction kettle, then add ferric sulfate, stir evenly, then add ammonium sulfate, stir evenly to obtain a mixed solution, and finally add the polydimethyldiallylammonium chloride solution, stir evenly, and spray dry at 230 °C to obtain the composite flocculant.

[0039] Among them, as Figure 1 shown in Figure 1 on the left, the mixed solution prepared in step (4) is placed at room temperature for 30 days, and no precipitate appears.

[0040] Among them, the polydimethyldiallylammonium chloride solution prepared in this example is as Figure 1 shown in the figures on the right 1 and right 2.

[0041] Example 2 A preparation method of a composite flocculant, comprising the following steps: (1) Add 3 kg of hydrochloric acid with a concentration of 20 wt% into a 5 L reaction kettle, then introduce nitrogen for 15 min to remove oxygen, add 1 kg of deammoniated aluminum ash under stirring, control the reaction temperature at 100 °C for atmospheric pressure reaction, the reaction time is 240 minutes, after the reaction, introduce 0.3 kg of sodium sulfide liquid with a concentration of 10% (wt%) into the reaction kettle, continue to stir for 30 min to convert heavy metal ions such as calcium ions, chromium ions, lead ions and nickel ions into sulfide precipitates, and then filter to obtain a polyaluminum chloride solution with an alumina content of 14% (wt%) and a polymerization degree of 30%.

[0042] (2) First add 3 kg of a dimethyldiallylammonium chloride solution with a concentration of 40 wt% into a 5 L reaction kettle, then continuously introduce an inert gas into the reaction kettle for 15 min, and then add 4 g of ammonium persulfate under stirring. After reacting at 44 °C for 1.0 h, adjust the temperature to 50 °C, continue to react for 2 h, then raise the temperature to 60 °C, react for 2 h, and then cool to obtain a polydimethyldiallylammonium chloride solution with a viscosity of 0.5 dL / g (concentration of 40 wt%).

[0043] (3) Weigh the following raw materials according to the mass ratio: 500 parts of polyaluminum chloride solution, 184 parts of ferric sulfate, 1.4 parts of ammonium sulfate, 6 parts of polydimethyldiallylammonium chloride solution; Among them, the mass ratio of the sum of the masses of the polyaluminum chloride solution and ferric sulfate to the mass of the polydimethyldiallylammonium chloride solution is 114:1; (4) Add the polyaluminum chloride solution into the reaction kettle, then add ferric sulfate, stir evenly, then add ammonium sulfate, stir evenly to obtain a mixed solution, and finally add the polydimethyldiallylammonium chloride solution, stir evenly, and spray dry at 230 °C to obtain the composite flocculant.

[0044] Example 3 A preparation method of a composite flocculant, comprising the following steps: (1) Add 3 kg of hydrochloric acid with a concentration of 20 wt% into a 5 L reactor, then introduce nitrogen for 15 min to remove oxygen. Under stirring, add 1 kg of deammoniated aluminum ash, control the reaction temperature at 100 °C for atmospheric pressure reaction, and the reaction time is 240 min. After the reaction, introduce 0.3 kg of sodium sulfide liquid with a concentration of 10% (wt%) into the reactor, and continue stirring for 30 min to convert heavy metal ions such as calcium ions, chromium ions, lead ions, and nickel ions into sulfide precipitates. Then filter to obtain a polyaluminum chloride solution with an alumina content of 14% (wt%) and a polymerization degree of 30%.

[0045] (2) First, add 3 kg of dimethyldiallylammonium chloride solution with a concentration of 40 wt% into a 5 L reactor, then continuously introduce inert gas into the reactor for 15 min. Then, under stirring, add 4 g of ammonium persulfate. After reacting at 44 °C for 1.0 h, adjust the temperature to 50 °C and continue reacting for 2 h. Then raise the temperature to 60 °C and react for 2 h. After cooling, obtain a poly(dimethyldiallylammonium chloride) solution with a viscosity of 0.5 dL / g (concentration: 40 wt%).

[0046] (3) Weigh the following raw materials according to the mass ratio: 500 parts of polyaluminum chloride solution, 170 parts of ferric sulfate, 1.3 parts of ammonium sulfate, and 7.5 parts of poly(dimethyldiallylammonium chloride) solution; Among them, the mass ratio of the sum of the masses of the polyaluminum chloride solution and ferric sulfate to the mass of the poly(dimethyldiallylammonium chloride) solution is 89.3:1; (4) Add the polyaluminum chloride solution into the reactor, then add ferric sulfate and stir evenly. Then add ammonium sulfate and stir evenly to obtain a mixed solution. Finally, add the poly(dimethyldiallylammonium chloride) solution and stir evenly. Spray dry at 230 °C to obtain the composite flocculant.

[0047] Example 4 A preparation method of a composite flocculant, comprising the following steps: (1) Add 3 kg of hydrochloric acid with a concentration of 20 wt% into a 5 L reactor, then introduce nitrogen for 15 min to remove oxygen. Under stirring, add 1 kg of deammoniated aluminum ash, control the reaction temperature at 100 °C for atmospheric pressure reaction, and the reaction time is 240 min. After the reaction, introduce 0.3 kg of sodium sulfide liquid with a concentration of 10% (wt%) into the reactor, and continue stirring for 30 min to convert heavy metal ions such as calcium ions, chromium ions, lead ions, and nickel ions into sulfide precipitates. Then filter to obtain a polyaluminum chloride solution with an alumina content of 14% (wt%) and a polymerization degree of 30%.

[0048] (2) First, add 3 kg of a 40 wt% dimethyldiallylammonium chloride solution to a 5 L reaction kettle, then continuously introduce an inert gas into the reaction kettle for 15 min, and then add 4 g of ammonium persulfate under stirring. After reacting at 44 °C for 1.0 h, adjust the temperature to 50 °C and continue the reaction for 2 h. Then raise the temperature to 60 °C and react for 2 h. After cooling, a poly(dimethyldiallylammonium chloride) solution with a viscosity of 0.5 dL / g (concentration 40 wt%) is obtained.

[0049] (3) Weigh the following raw materials according to the mass ratio: 500 parts of polyaluminum chloride solution, 150 parts of ferric sulfate, 1.2 parts of ammonium sulfate, and 12.5 parts of poly(dimethyldiallylammonium chloride) solution; Among them, the mass ratio of the sum of the masses of the polyaluminum chloride solution and ferric sulfate to the mass of the poly(dimethyldiallylammonium chloride) solution is 52:1; (4) Add the polyaluminum chloride solution to the reaction kettle, then add ferric sulfate and stir evenly. Then add ammonium sulfate and stir evenly to obtain a mixed solution. Finally, add the poly(dimethyldiallylammonium chloride) solution and stir evenly. Spray dry at 230 °C to obtain a composite flocculant.

[0050] Example 5 A preparation method of a composite flocculant, comprising the following steps: (1) Add 3 kg of 20 wt% hydrochloric acid to a 5 L reaction kettle, then introduce nitrogen for 15 min to remove oxygen. Add 1 kg of deammoniated aluminum ash under stirring and control the reaction temperature at 100 °C for an atmospheric reaction. The reaction time is 240 min. After the reaction, introduce 0.3 kg of a 10% (wt%) sodium sulfide solution into the reaction kettle and continue stirring for 30 min to convert heavy metal ions such as calcium ions, chromium ions, lead ions, and nickel ions into sulfide precipitates. Then filter to obtain a polyaluminum chloride solution with an alumina content of 14% (wt%) and a polymerization degree of 30%.

[0051] (2) First, add 3 kg of a 40 wt% dimethyldiallylammonium chloride solution to a 5 L reaction kettle, then continuously introduce an inert gas into the reaction kettle for 15 min, and then add 4 g of ammonium persulfate under stirring. After reacting at 44 °C for 1.0 h, adjust the temperature to 50 °C and continue the reaction for 2 h. Then raise the temperature to 60 °C and react for 2 h. After cooling, a poly(dimethyldiallylammonium chloride) solution with a viscosity of 0.5 dL / g (concentration 40 wt%) is obtained.

[0052] (3) Weigh the following raw materials according to the mass ratio: 500 parts of polyaluminum chloride solution, 130 parts of ferric sulfate, 1.1 parts of ammonium sulfate, and 14 parts of poly(dimethyldiallylammonium chloride) solution; Among them, the mass ratio of the sum of the mass of the polyaluminum chloride solution and ferric sulfate to the mass of the polydimethyldiallylammonium chloride solution is 45:1; (4)Add the polyaluminum chloride solution to the reaction kettle, then add ferric sulfate, stir evenly, then add ammonium sulfate, stir evenly to obtain a mixed solution, and finally add the polydimethyldiallylammonium chloride solution, stir evenly, and spray dry at 230 °C to obtain a composite flocculant.

[0053] Example 6 A preparation method of a composite flocculant includes the following steps: (1)Add 3 kg of hydrochloric acid with a concentration of 20 wt% to a 5L reaction kettle, then introduce nitrogen for 15 minutes to remove oxygen, add 1 kg of deammoniated aluminum ash under stirring, control the reaction temperature at 100 °C for atmospheric pressure reaction, the reaction time is 240 minutes, and after the reaction, introduce 0.3 kg of sodium sulfide liquid with a concentration of 10% (wt%) into the reaction kettle, and continue to stir for 30 minutes to convert heavy metal ions such as calcium ions, chromium ions, lead ions and nickel ions into sulfide precipitates, and then filter to obtain a polyaluminum chloride solution with an alumina content of 14% (wt%) and a polymerization degree of 30%.

[0054] (2)First add 3 kg of a dimethyldiallylammonium chloride solution with a concentration of 40 wt% to a 5L reaction kettle, then continuously introduce an inert gas into the reaction kettle for 15 minutes, and then add 4 g of ammonium persulfate under stirring. After reacting at 44 °C for 1.0 h, adjust the temperature to 50 °C and continue to react for 2 h, then raise the temperature to 60 °C. After reacting for 2 h, cool to obtain a polydimethyldiallylammonium chloride solution (concentration of 40 wt%) with a viscosity of 0.5 dL / g.

[0055] (3)Weigh the following raw materials according to the mass ratio: 500 parts of polyaluminum chloride solution, 100 parts of ferric sulfate, 1 part of ammonium sulfate, 15 parts of polydimethyldiallylammonium chloride solution; Among them, the mass ratio of the sum of the mass of the polyaluminum chloride solution and ferric sulfate to the mass of the polydimethyldiallylammonium chloride solution is 40:1; (4)Add the polyaluminum chloride solution to the reaction kettle, then add ferric sulfate, stir evenly, then add ammonium sulfate, stir evenly to obtain a mixed solution, and finally add the polydimethyldiallylammonium chloride solution, stir evenly, and spray dry at 230 °C to obtain a composite flocculant.

[0056] Example 7 A preparation method of a composite flocculant includes the following steps: (1) Add 3 kg of hydrochloric acid with a concentration of 20 wt% to a 5 L reaction kettle, then introduce nitrogen for 15 minutes to remove oxygen. While stirring, add 1 kg of deammoniated aluminum ash, control the reaction temperature at 100 °C for atmospheric pressure reaction, and the reaction time is 240 minutes. After the reaction, introduce 0.3 kg of sodium sulfide liquid with a concentration of 10% (wt%) into the reaction kettle, and continue to stir for 30 minutes to convert heavy metal ions such as calcium ions, chromium ions, lead ions, and nickel ions into sulfide precipitates. Then filter to obtain a polyaluminum chloride solution with an alumina content of 14% (wt%) and a polymerization degree of 30%.

[0057] (2) First, add 3 kg of dimethyldiallylammonium chloride solution with a concentration of 40 wt% to a 5 L reaction kettle, then continuously introduce inert gas into the reaction kettle for 15 minutes. Then, while stirring, add 4 g of ammonium persulfate. After reacting at 44 °C for 1.0 h, adjust the temperature to 50 °C and continue to react for 2.5 h. Then raise the temperature to 65 °C and react for 2 h. After cooling, obtain a poly(dimethyldiallylammonium chloride) solution with a viscosity of 1 dL / g (concentration of 40 wt%).

[0058] (3) Weigh the following raw materials according to the mass ratio: 500 parts of polyaluminum chloride solution, 200 parts of ferric sulfate, 1.5 parts of ammonium sulfate, and 5 parts of poly(dimethyldiallylammonium chloride) solution; Among them, the mass ratio of the sum of the masses of the polyaluminum chloride solution and ferric sulfate to the mass of the poly(dimethyldiallylammonium chloride) solution is 140:1; (4) Add the polyaluminum chloride solution to the reaction kettle, then add ferric sulfate and stir evenly. Then add ammonium sulfate and stir evenly to obtain a mixed solution. Finally, add the poly(dimethyldiallylammonium chloride) solution and stir evenly. Spray dry at 230 °C to obtain a composite flocculant.

[0059] Example 8 A preparation method of a composite flocculant, comprising the following steps: (1) Add 3 kg of hydrochloric acid with a concentration of 20 wt% to a 5 L reaction kettle, then introduce nitrogen for 15 minutes to remove oxygen. While stirring, add 0.85 kg of deammoniated aluminum ash step by step, control the reaction temperature at 100 °C for atmospheric pressure reaction, and the reaction time is 200 minutes. After the reaction, introduce 0.3 kg of sodium sulfide liquid with a concentration of 10% (wt%) into the reaction kettle, and continue to stir for 30 minutes to convert heavy metal ions such as calcium ions, chromium ions, lead ions, and nickel ions into sulfide precipitates. Then filter to remove the filter residue to obtain a polyaluminum chloride solution with an alumina content of 12% (wt%) and a polymerization degree of 20%.

[0060] (2) First, add 3 kg of a 40 wt% dimethyldiallylammonium chloride solution to a 5 L reaction kettle, then continuously introduce an inert gas into the reaction kettle for 15 min, and then add 4 g of ammonium persulfate under stirring. After reacting at 44 °C for 1.0 h, adjust the temperature to 50 °C and continue the reaction for 2 h. Then raise the temperature to 65 °C and react for 2 h. After cooling, a poly(dimethyldiallylammonium chloride) solution with a viscosity of 0.5 dL / g (concentration: 40 wt%) is obtained.

[0061] (3) Weigh the following raw materials according to the mass ratio: 500 parts of polyaluminum chloride solution, 200 parts of ferric sulfate, 1.5 parts of ammonium sulfate, and 5 parts of poly(dimethyldiallylammonium chloride) solution; Among them, the mass ratio of the sum of the masses of the polyaluminum chloride solution and ferric sulfate to the mass of the poly(dimethyldiallylammonium chloride) solution is 140:1; (4) Add the polyaluminum chloride solution to the reaction kettle, then add ferric sulfate and stir evenly. Then add ammonium sulfate and stir evenly to obtain a mixed solution. Finally, add the poly(dimethyldiallylammonium chloride) solution and stir evenly. Spray dry at 230 °C to obtain a composite flocculant.

[0062] Example 9 A preparation method of a composite flocculant, comprising the following steps: (1) Add 3 kg of 20 wt% hydrochloric acid to a 5 L reaction kettle, then introduce nitrogen for 15 min to remove oxygen. Add 0.70 kg of deammoniated aluminum ash step by step under stirring, control the reaction temperature at 100 °C for an atmospheric reaction, and the reaction time is 150 min. After the reaction, introduce 0.3 kg of a 10% (wt%) sodium sulfide liquid into the reaction kettle and continue stirring for 30 min to convert heavy metal ions such as calcium ions, chromium ions, lead ions, and nickel ions into sulfide precipitates. Then filter to remove the filter residue to obtain a polyaluminum chloride solution with an alumina content of 10% (wt%) and a polymerization degree of 10%.

[0063] (2) First, add 3 kg of a 40 wt% dimethyldiallylammonium chloride solution to a 5 L reaction kettle, then continuously introduce an inert gas into the reaction kettle for 15 min, and then add 4 g of ammonium persulfate under stirring. After reacting at 44 °C for 1.0 h, adjust the temperature to 50 °C and continue the reaction for 2 h. Then raise the temperature to 65 °C and react for 2 h. After cooling, a poly(dimethyldiallylammonium chloride) solution with a viscosity of 0.5 dL / g (concentration: 40 wt%) is obtained.

[0064] (3) Weigh the following raw materials according to the mass ratio: 500 parts of polyaluminum chloride solution, 200 parts of ferric sulfate, 1.5 parts of ammonium sulfate, and 5 parts of poly(dimethyldiallylammonium chloride) solution; Among them, the mass ratio of the sum of the masses of the polyaluminum chloride solution and ferric sulfate to the mass of the polydimethyldiallylammonium chloride solution is 140:1; (4) Add the polyaluminum chloride solution to the reaction kettle, then add ferric sulfate, stir evenly, then add ammonium sulfate, stir evenly to obtain a mixed solution, and finally add the polydimethyldiallylammonium chloride solution, stir evenly, and spray dry at 230 °C to obtain a composite flocculant.

[0065] Example 10 A preparation method of a composite flocculant includes the following steps: (1) Add 3 kg of hydrochloric acid with a concentration of 20 wt% to a 5 L reaction kettle, then introduce nitrogen for 15 minutes to remove oxygen, and add 1.3 kg of deammoniated aluminum ash step by step under stirring, control the reaction temperature at 100 °C for atmospheric pressure reaction, the reaction time is 260 minutes, and after the reaction, introduce 0.3 kg of sodium sulfide liquid with a concentration of 10% (wt%) into the reaction kettle, and continue to stir for 30 minutes to convert heavy metal ions such as calcium ions, chromium ions, lead ions and nickel ions into sulfide precipitates, and then filter to obtain a polyaluminum chloride solution with an alumina content of 15% (wt%) and a polymerization degree of 45%.

[0066] (2) First add 3 kg of a dimethyldiallylammonium chloride solution with a concentration of 40 wt% to a 5 L reaction kettle, then continuously introduce an inert gas into the reaction kettle for 15 minutes, and then add 4 g of ammonium persulfate under stirring. After reacting at 44 °C for 1.0 h, adjust the temperature to 50 °C and continue to react for 2 h, then raise the temperature to 65 °C and react for 2 h, and then cool to obtain a polydimethyldiallylammonium chloride solution (concentration of 40 wt%) with a viscosity of 0.5 dL / g.

[0067] (3) Weigh the following raw materials according to the mass ratio: 500 parts of polyaluminum chloride solution, 200 parts of ferric sulfate, 1.5 parts of ammonium sulfate, 5 parts of polydimethyldiallylammonium chloride solution; Among them, the mass ratio of the sum of the masses of the polyaluminum chloride solution and ferric sulfate to the mass of the polydimethyldiallylammonium chloride solution is 140:1; (4) Add the polyaluminum chloride solution to the reaction kettle, then add ferric sulfate, stir evenly, then add ammonium sulfate, stir evenly to obtain a mixed solution, and finally add the polydimethyldiallylammonium chloride solution, stir evenly, and spray dry at 230 °C to obtain a composite flocculant.

[0068] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that the ratios of the polyaluminum chloride solution, ferric sulfate, ammonium sulfate, and polydimethyldiallylammonium chloride solution are different, and the others are the same.

[0069] This comparative example weighed the following raw materials according to the mass ratio: 500 parts of polyaluminum chloride solution, 300 parts of ferric sulfate, 2 parts of ammonium sulfate, and 2 parts of polydimethyldiallylammonium chloride solution.

[0070] Comparative Example 2 The difference between Comparative Example 2 and Example 1 lies in the different ratios of polyaluminum chloride solution, ferric sulfate, ammonium sulfate, and polydimethyldiallylammonium chloride solution, while others are the same.

[0071] This comparative example weighed the following raw materials according to the mass ratio: 500 parts of polyaluminum chloride solution, 50 parts of ferric sulfate, 0.5 part of ammonium sulfate, and 20 parts of polydimethyldiallylammonium chloride solution.

[0072] Comparative Example 3 The difference between Comparative Example 3 and Example 1 lies in the different viscosity of the polydimethyldiallylammonium chloride solution.

[0073] The viscosity of the polydimethyldiallylammonium chloride solution in this comparative example is 0.4 dL / g, and the preparation method is as follows: First, add 3 kg of dimethyldiallylammonium chloride solution with a concentration of 40 wt% to a 5 L reaction kettle, then continuously introduce inert gas into the reaction kettle for 15 minutes, and then add 4 g of ammonium persulfate under stirring. After reacting at 44 °C for 1.5 h, adjust the temperature to 50 °C and continue to react for 1.5 h. Then raise the temperature to 60 °C and react for 1.5 h. After cooling, a polydimethyldiallylammonium chloride solution with a viscosity of 0.4 dL / g (concentration of 40 wt%) is obtained.

[0074] Comparative Example 4 The difference between Comparative Example 4 and Example 1 lies in the different viscosity of the polydimethyldiallylammonium chloride solution.

[0075] The viscosity of the polydimethyldiallylammonium chloride solution in this comparative example is 1.3 dL / g, and the preparation method is as follows: First, add 3 kg of dimethyldiallylammonium chloride solution with a concentration of 40 wt% to a 5 L reaction kettle, then continuously introduce inert gas into the reaction kettle for 15 minutes, and then add 4 g of ammonium persulfate under stirring. After reacting at 44 °C for 1.5 h, adjust the temperature to 60 °C and continue to react for 3 h. Then raise the temperature to 70 °C and react for 3 h. After cooling, a polydimethyldiallylammonium chloride solution with a viscosity of 1.3 dL / g (concentration of 40 wt%) is obtained.

[0076] Comparative Example 5 The flocculant in Comparative Example 5 is a polyaluminum chloride solution with an alumina content of 14% (wt%) and a polymerization degree of 30%. The preparation method is as follows: Add 3 kg of hydrochloric acid with a concentration of 20 wt% into a 5 L reaction kettle, then introduce nitrogen for 15 minutes to remove oxygen. While stirring, add 1 kg of deammoniated aluminum ash, control the reaction temperature at 100 °C for atmospheric pressure reaction, and the reaction time is 240 minutes. After the reaction, introduce 0.3 kg of sodium sulfide liquid with a concentration of 10% (wt%) into the reaction kettle and continue to stir for 30 minutes to convert heavy metal ions such as calcium ions, chromium ions, lead ions, and nickel ions into sulfide precipitates. Then filter to obtain a polyaluminum chloride solution with an aluminum oxide content of 14% (wt%) and a polymerization degree of 30%.

[0077] Comparative Example 6 The difference between Comparative Example 6 and Example 1 is that the poly(dimethyldiallylammonium chloride) solution was not added, and the others are the same.

[0078] For this comparative example, weigh the following raw materials according to the mass ratio: 500 parts of polyaluminum chloride solution, 200 parts of ferric sulfate, and 1.5 parts of ammonium sulfate.

[0079] Comparative Example 7 The difference between Comparative Example 7 and Example 1 is that ammonium sulfate was not added, and the others are the same.

[0080] For this comparative example, weigh the following raw materials according to the mass ratio: 500 parts of polyaluminum chloride solution, 200 parts of ferric sulfate, and 5 parts of poly(dimethyldiallylammonium chloride) solution.

[0081] Comparative Example 8 The difference between Comparative Example 8 and Example 1 is that ferric sulfate was not added, and the others are the same.

[0082] For this comparative example, weigh the following raw materials according to the mass ratio: 500 parts of polyaluminum chloride solution, 1.5 parts of ammonium sulfate, and 5 parts of poly(dimethyldiallylammonium chloride) solution.

[0083] Comparative Example 9 The difference between Comparative Example 9 and Example 1 is that the poly(dimethyldiallylammonium chloride) in this comparative example is commercially available, and the others are the same.

[0084] For this comparative example, weigh the following raw materials according to the mass ratio: 500 parts of polyaluminum chloride solution, 200 parts of ferric sulfate, 1.5 parts of ammonium sulfate, and 5 parts of poly(dimethyldiallylammonium chloride).

[0085] The poly(dimethyldiallylammonium chloride) in this comparative example is sourced from Wuxi Lanbo Chemistry, with the product number BLUWAT liquid.

[0086] Comparative Example 10 The difference between Comparative Example 10 and Example 1 is that in Comparative Example 10, commercially available polyaluminum chloride of the same amount was directly used to replace the polyaluminum chloride solution, and the others are the same.

[0087] For this comparative example, the following raw materials were weighed according to the mass parts ratio: 500 parts of polyaluminum chloride (commercially available, with an alumina content of 30%), 200 parts of ferric sulfate, 1.5 parts of ammonium sulfate, and 5 parts of polydimethyldiallylammonium chloride.

[0088] Test Example The sludge to be treated was the original municipal sludge without chemical treatment, with a sludge concentration of 4%. The sludge conditioning method was as follows: 1) In a 50 m 3 30 m of the above-mentioned sludge was added to the sludge conditioning tank. 3 Using the same dosage of 120 kg of medicine, it was added to the sludge for conditioning respectively. The conditioning conditions were the same, and the stirring and conditioning time was 15 minutes each; 2) A plate and frame filter press with a filtration area of 200 square meters was used to press and dehydrate the above-mentioned conditioned sludge respectively. The dehydration conditions were the same, which were a sludge feeding time of 90 minutes, a dehydration and pressing time of 60 minutes, and a pressing pressure of 1.5 MPa; 3) Mud cakes with the same thickness were taken to detect the sludge moisture content, and the test results are shown in Table 1.

[0089] Table 1 It can be seen from Table 1 that the composite flocculant described in the present invention has excellent dehydration efficiency and is very suitable for sludge dehydration.

[0090] Comparing Comparative Examples 1 - 6 with Comparative Examples 1 - 2, by controlling the dosage of each raw material as: 500 parts of polyaluminum chloride solution, 100 - 200 parts of ferric sulfate, 1 - 1.5 parts of stabilizer, and 5 - 15 parts of polydimethyldiallylammonium chloride solution, the dehydration efficiency was effectively improved.

[0091] Comparing Comparative Example 1 with Comparative Examples 3 - 4, it can be seen that the polydimethyldiallylammonium chloride solution with a viscosity of 0.5 - 1 dL / g prepared by the preparation method of the present invention significantly improves the dehydration efficiency.

[0092] Comparing Comparative Example 1 with Comparative Examples 5 - 10, it can be seen that the polyaluminum chloride solution, ferric sulfate, stabilizer, and polydimethyldiallylammonium chloride solution described in the present invention have a significant synergistic effect. Under the synergistic effect of the polyaluminum chloride solution, ferric sulfate, stabilizer, and polydimethyldiallylammonium chloride solution, the dehydration efficiency is significantly improved.

[0093] Comparing Comparative Examples 1, 6 with Examples 2 - 5, it can be seen that the present invention controls the mass ratio of the sum of the masses of the polyaluminum chloride solution and ferric sulfate to the mass of the polydimethyldiallylammonium chloride solution to be (40 - 140):1, further improving the dehydration efficiency.

[0094] Comparing Comparative Example 1, 6 with Examples 3 - 4, it can be seen that the present invention effectively improves the dehydration efficiency by controlling the amounts of each raw material as follows: 500 parts of polyaluminum chloride solution, 150 - 170 parts of ferric sulfate, 1.2 - 1.3 parts of stabilizer, and 7.5 - 12.5 parts of polydimethyldiallylammonium chloride solution.

[0095] Comparing Comparative Example 1, 8 - 10, it can be seen that the present invention uses a polyaluminum chloride solution with an alumina content of 12 - 14 wt% and a polymerization degree of 20 - 30%, which effectively improves the dehydration efficiency.

[0096] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the protection scope of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A composite flocculant, characterized in that: The preparation method comprises the following raw materials in parts by weight: 500 parts of polyaluminium chloride solution, 100-200 parts of ferric sulfate, 1-1.5 parts of a stabilizer, and 5-15 parts of polydimethyldiallylammonium chloride solution; The stabilizer includes ammonium sulfate; The viscosity of the polydimethyldiallylammonium chloride solution is 0.5-1 dL / g; The polyaluminium chloride solution has an aluminium oxide content of 10-15 wt % and a degree of polymerization of 10-45 %.

2. The composite flocculant according to claim 1, characterized in that: The preparation method comprises the following raw materials in parts by weight: 500 parts of polyaluminium chloride solution, 150-170 parts of ferric sulfate, 1.2-1.3 parts of a stabilizer, and 7.5-12.5 parts of polydimethyldiallylammonium chloride solution.

3. The composite flocculant according to claim 1, characterized in that: The polyaluminium chloride solution has an aluminium oxide content of 12-14 wt %, a degree of polymerization of 20-30 %, and does not contain calcium.

4. The composite flocculant according to claim 1, characterized in that: The mass ratio of the sum of the masses of the polyaluminium chloride solution and ferric sulfate to the mass ratio of the polydimethyldiallylammonium chloride solution is (40-140):

1.

5. The composite flocculant according to claim 1, characterized in that: The preparation method of the polydimethyldiallylammonium chloride solution comprises the following steps: Add a dimethyldiallyl ammonium chloride solution with a concentration of 38-42 wt% into a reaction kettle, continuously introduce an inert gas into the reaction kettle for 5-15 min, add ammonium persulfate, react at 40-44° C. for 0.5-1.5 h, heat to 45-55° C., react for 1-3 h, heat to 60-70° C., react for 2-3 h, and cool to obtain a polydimethyldiallyl ammonium chloride solution; The mass ratio of the dimethyldiallylammonium chloride solution to ammonium persulfate is 1:(0.001-0.0015).

6. The composite flocculant according to claim 1, characterized in that: The preparation method of the polyaluminium chloride solution comprises the following steps: Add a hydrochloric acid solution with a concentration of 20-30wt% into the reactor, continue to introduce inert gas into the reactor for 5-15 minutes, add deaminated aluminum ash, react at 100-105°C for 180-240 minutes, add sodium sulfide solution, stir evenly, filter, and obtain a polyaluminum chloride solution; The mass ratio of the hydrochloric acid solution, deaminated aluminum ash and sodium sulfide solution is (2.8-3):1:(0.2-0.4).

7. The composite flocculant according to claim 6, characterized in that: The mass fraction of the sodium sulfide solution is 8-12%.

8. The method for preparing the composite flocculant according to any one of claims 1 to 7, characterized in that: The following steps are involved: The polyaluminium chloride solution, ferric sulfate and a stabilizer are mixed evenly, and then the polydimethyldiallylammonium chloride solution is added, stirred evenly, and spray-dried to obtain a composite flocculant.

9. The method for preparing a composite flocculant according to claim 8, characterized in that: The spray drying temperature is 200-260°C.

10. Use of the composite flocculant according to any one of claims 1 to 7 in sludge dewatering.

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