A composite flocculant, its preparation method and its application in sludge dewatering

Abstract

The present invention discloses a composite flocculant, a preparation method thereof and its application in sludge dewatering, belonging to the technical field of flocculants. The preparation raw materials include the following parts by mass: 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 stabilizer includes ammonium sulfate; the viscosity of the polydimethyldiallylammonium chloride solution is 0.5 - 1 dL / g. In this application, a polyaluminum chloride solution with an alumina content of 10 - 15 wt% and a polymerization degree of 10 - 45% is used as the matrix. 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.

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

[0003] By adding active silica to polyaluminum chloride, polysilicon aluminum 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, adding cationic electrolytes with high cation charge density to 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 object 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 dehydration efficiency.

[0006] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] A composite flocculant, comprising the following parts by mass of preparation raw materials: 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;

[0008] The stabilizer includes ammonium sulfate;

[0009] The viscosity of the polydimethyldiallylammonium chloride solution is 0.5 - 1 dL / g;

[0010] The alumina content of the polyaluminum chloride solution is 10 - 15 wt%, and the polymerization degree is 10 - 45%.

[0011] In a large number of studies, the inventors of the present invention found that when poly(dimethyldiallylammonium chloride) purchased from the market was incorporated into polyaluminum chloride products and used as a liquid product, the effect was indeed better than that of polyaluminum chloride. However, when it was spray-dried, the coagulation effect of the resulting product was very poor. The inventors speculated that it might be because poly(dimethyldiallylammonium chloride) has a high cationic charge density, which leads to the destruction of the synergistic effect of the resulting product and even antagonistic effects, resulting in a decrease in the coagulation effect.

[0012] 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, under the combined action of ferric sulfate, a stabilizer, and a poly(dimethyldiallylammonium chloride) solution, a composite flocculant with excellent flocculation effect and stability is obtained. The composite flocculant has excellent dehydration efficiency.

[0013] In the present invention, sulfate ions and iron ions are introduced into the polyaluminum chloride solution to make it 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, so that the polyaluminum ferric chloride solution will not stratify even after being stored for one month, effectively solving the problem of instability of the liquid product with added sulfate ions. Then, a poly(dimethyldiallylammonium chloride) solution with a viscosity of 0.5-1 dL / g is incorporated to increase the cationic charge density of the product and improve 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 a good coagulation effect, is particularly suitable for sludge dewatering conditioning, and has excellent dehydration efficiency.

[0014] When the composite coagulant of the present invention is used for sludge dewatering conditioning, only one agent is needed for conditioning. The dehydration efficiency is better than that of the traditional conditioning effects of two agents, polyaluminum chloride (or polyferric sulfate) and polyacrylamide, which can meet the requirements of users for deep dehydration conditioning. It is convenient to use and can be sold locally. Since 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 a good comprehensive cost performance and excellent market competition conditions.

[0015] 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 poly(dimethyldiallylammonium chloride) solution. Especially when the dosages of the raw materials are controlled within this range, the synergistic effect is more obvious, it can be more suitable for sludge dewatering, and the dehydration efficiency can be improved.

[0016] 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 poly(dimethyldiallylammonium chloride) solution. Especially when the dosages of each raw material are controlled within this range, the synergistic effect is more obvious, and it is more suitable for sludge dewatering, improving the dewatering efficiency.

[0017] As a preferred embodiment of the present invention, the alumina content of the polyaluminum chloride solution is 12 - 14 wt%, and the polymerization degree is 20 - 30%. The polyaluminum chloride solution does not contain calcium element. Especially when using a polyaluminum chloride solution with an alumina content of 12 - 14 wt% and a polymerization degree of 20 - 30%, it has a better flocculation effect, better compatibility in the system, more obvious synergistic effect, and can more effectively improve the dewatering efficiency.

[0018] 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 dewatering effect. By controlling the mass ratio within this range, the dewatering efficiency is effectively improved.

[0019] As a preferred embodiment of the present invention, the preparation method of the poly(dimethyldiallylammonium chloride) solution includes the following steps:

[0020] Add a dimethyldiallylammonium chloride solution with a concentration of 38 - 42 wt% into 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 the poly(dimethyldiallylammonium chloride) solution;

[0021] The mass ratio of the dimethyldiallylammonium chloride solution to ammonium persulfate is 1:(0.001 - 0.0015).

[0022] The present invention uses 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 especially 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 decreases significantly. When the viscosity is too high, the stability of the obtained product decreases, and the solubility in water also decreases, resulting in a significant decrease in the dewatering effect.

[0023] It should be noted that by controlling the polymerization time of the dimethyldiallylammonium chloride solution and the subsequent reaction temperature, the viscosity of the polydimethyldiallylammonium chloride solution is changed.

[0024] As a preferred embodiment of the present invention, the preparation method of the polyaluminum chloride solution includes the following steps:

[0025] 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;

[0026] The mass ratio of the hydrochloric acid solution, deammoniated aluminum ash, and sodium sulfide solution is (2.8-3):1:(0.2-0.4).

[0027] 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 changed.

[0028] 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.

[0029] As a preferred embodiment of the present invention, the mass fraction of the sodium sulfide solution is 8-12%.

[0030] The present invention also provides a preparation method of a composite flocculant, including the following steps:

[0031] Mix the polyaluminum chloride solution, ferric sulfate, and stabilizer evenly, then add the polydimethyldiallylammonium chloride solution, stir evenly, and spray dry to obtain a composite flocculant.

[0032] As a preferred embodiment of the present invention, the temperature of the spray drying is 200-260 °C.

[0033] The present invention also provides an application of the composite flocculant in sludge dewatering.

[0034] 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.

[0035] (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 stored 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 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.

[0036] (3) When the composite coagulant of the present invention is used for sludge dewatering conditioning, only one type of agent is needed for conditioning. Its dewatering efficiency is superior to that of the traditional conditioning effects of two agents, namely polyaluminum chloride (or polyferric sulfate) and polyacrylamide, and can meet the requirements of users for deep dewatering conditioning. It is convenient to use and can be sold locally. Since 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.

[0037] (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, etc. Brief Description of the Drawings

[0038] Figure 1 It is a diagram of the mixed solution and the polydimethyldiallylammonium chloride solution prepared in Example 1 of the present invention. Detailed Embodiments

[0039] 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.

[0040] 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.

[0041] 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.

[0042] In this application, there is no particular limitation on the specific dispersion and stirring treatment methods.

[0043] Unless otherwise specified, the component raw materials or instruments used in each embodiment and comparative example 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.

[0044] 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.

[0045] Example 1

[0046] A preparation method of a composite flocculant, comprising the following steps:

[0047] (1) Add 3 kg of hydrochloric acid with a concentration of 20 wt% to 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, the reaction time is 240 min. After the reaction, introduce 0.3 kg of a 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 aluminum oxide content of 14% (wt%) and a polymerization degree of 30%.

[0048] (2) First, add 3 kg of a dimethyldiallylammonium chloride solution with a concentration of 40 wt% to a 5 L reactor, then continuously introduce an 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 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%).

[0049] (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 poly(dimethyldiallylammonium chloride) solution;

[0050] 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 140:1;

[0051] (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.

[0052] 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.

[0053] 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.

[0054] Example 2

[0055] A preparation method of a composite flocculant, comprising the following steps:

[0056] (1) Add 3 kg of hydrochloric acid with a concentration of 20 wt% to 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, and after the reaction, introduce 0.3 kg of a sodium sulfide liquid with a concentration of 10% (wt%) into the reaction kettle, and 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%.

[0057] (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 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 (concentration of 40 wt%) with a viscosity of 0.5 dL / g.

[0058] (3) Weigh the following raw materials according to the mass portion ratio: 500 parts of polyaluminum chloride solution, 184 parts of ferric sulfate, 1.4 parts of ammonium sulfate, 6 parts of polydimethyldiallylammonium chloride solution;

[0059] 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 114:1;

[0060] (4) Add the polyaluminum chloride solution into a 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 perform spray drying at 230 °C to obtain a composite flocculant.

[0061] Example 3

[0062] A method for preparing a composite flocculant, comprising the following steps:

[0063] (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 min, and after the reaction, introduce 0.3 kg of a sodium sulfide liquid with a concentration of 10% (wt%) into the reaction kettle, and 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%.

[0064] (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 and continue to react for 2 h, then raise the temperature to 60 °C, and after reacting for 2 h, cool to obtain a polydimethyldiallylammonium chloride solution (with a concentration of 40 wt%) with a viscosity of 0.5 dL / g.

[0065] (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, 7.5 parts of polydimethyldiallylammonium chloride solution;

[0066] 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 89.3:1;

[0067] (4) Add the polyaluminum chloride solution into a 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 perform spray drying at 230 °C to obtain a composite flocculant.

[0068] Example 4

[0069] A method for preparing a composite flocculant, comprising the following steps:

[0070] (1) Add 3 kg of hydrochloric acid with a concentration of 20 wt% into a 5 L reactor, 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 reactor 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%.

[0071] (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 minutes. While stirring, add 4 g of ammonium persulfate, react at 44 °C for 1.0 h, then 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%).

[0072] (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;

[0073] 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;

[0074] (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, and spray dry at 230 °C to obtain a composite flocculant.

[0075] Example 5

[0076] A preparation method of a composite flocculant, comprising the following steps:

[0077] (1) Add 3 kg of hydrochloric acid with a concentration of 20 wt% into a 5 L reactor, 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 reactor 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%.

[0078] (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.

[0079] (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;

[0080] 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 45:1;

[0081] (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.

[0082] Example 6

[0083] A preparation method of a composite flocculant, comprising the following steps:

[0084] (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, control the reaction temperature at 100 °C for an atmospheric pressure reaction, and the reaction time is 240 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 obtain a polyaluminum chloride solution with an alumina content of 14% (wt%) and a polymerization degree of 30%.

[0085] (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.

[0086] (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, and 15 parts of poly(dimethyldiallylammonium chloride) solution;

[0087] 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;

[0088] (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.

[0089] Example 7

[0090] A preparation method of a composite flocculant includes the following steps:

[0091] (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, 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, 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%.

[0092] (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, continue to react for 2.5 h, then raise the temperature to 65 °C, react for 2 h, and then cool to obtain a polydimethyldiallylammonium chloride solution (concentration 40 wt%) with a viscosity of 1 dL / g.

[0093] (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;

[0094] 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 140:1;

[0095] (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.

[0096] Example 8

[0097] A preparation method of a composite flocculant, comprising the following steps:

[0098] (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. Stepwise add 0.85 kg of deammoniated aluminum ash under stirring, control the reaction temperature at 100 °C for atmospheric pressure reaction, with a reaction time of 200 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 remove the filter residue to obtain a polyaluminum chloride solution with an aluminum oxide content of 12% (wt%) and a polymerization degree of 20%.

[0099] (2) First, add 3 kg of a dimethyldiallylammonium chloride solution with a concentration of 40 wt% into a 5 L reactor, then continuously introduce an inert gas into the reactor for 15 min. Then add 4 g of ammonium persulfate under stirring, react at 44 °C for 1.0 h, then 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, obtain a poly dimethyldiallylammonium chloride solution with a viscosity of 0.5 dL / g (concentration of 40 wt%).

[0100] (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;

[0101] 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;

[0102] (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.

[0103] Example 9

[0104] A preparation method of a composite flocculant, comprising the following steps:

[0105] (1) Add 3 kg of hydrochloric acid with a concentration of 20 wt% to a 5 L reactor, then introduce nitrogen for 15 minutes to remove oxygen. Gradually add 0.70 kg of deammoniated aluminum ash under stirring, control the reaction temperature at 100 °C for atmospheric pressure reaction, and the reaction time is 150 minutes. 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 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 10% (wt%) and a polymerization degree of 10%.

[0106] (2) First, add 3 kg of dimethyldiallylammonium chloride solution with a concentration of 40 wt% to a 5 L reactor, then continuously introduce inert gas into the reactor for 15 minutes. Then add 4 g of ammonium persulfate under stirring, react at 44 °C for 1.0 h, then 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, and then cool to obtain a poly(dimethyldiallylammonium chloride) solution with a viscosity of 0.5 dL / g (concentration is 40 wt%).

[0107] (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;

[0108] 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;

[0109] (4) Add the polyaluminum chloride solution to 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, and spray dry at 230 °C to obtain a composite flocculant.

[0110] Example 10

[0111] A preparation method of a composite flocculant, comprising the following steps:

[0112] (1) Add 3 kg of hydrochloric acid with a concentration of 20 wt% to a 5 L reactor, then introduce nitrogen for 15 minutes to remove oxygen. Gradually add 1.3 kg of deammoniated aluminum ash under stirring, control the reaction temperature at 100 °C for atmospheric pressure reaction, and the reaction time is 260 minutes. 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 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 15% (wt%) and a polymerization degree of 45%.

[0113] (2) First, add 3 kg of a 40 wt% dimethyldiallylammonium chloride solution to a 5 L reactor. Then, continuously introduce an inert gas into the reactor for 15 min. Next, 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 reacting 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.

[0114] (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;

[0115] 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;

[0116] (4) Add the polyaluminum chloride solution to the reactor, then add ferric sulfate and stir evenly. Next, 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.

[0117] Comparative Example 1

[0118] The difference between Comparative Example 1 and Example 1 lies in the different ratios of the polyaluminum chloride solution, ferric sulfate, ammonium sulfate, and poly(dimethyldiallylammonium chloride) solution, while the others are the same.

[0119] In this comparative example, weigh 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 poly(dimethyldiallylammonium chloride) solution.

[0120] Comparative Example 2

[0121] The difference between Comparative Example 2 and Example 1 lies in the different ratios of the polyaluminum chloride solution, ferric sulfate, ammonium sulfate, and poly(dimethyldiallylammonium chloride) solution, while the others are the same.

[0122] In this comparative example, weigh 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 poly(dimethyldiallylammonium chloride) solution.

[0123] Comparative Example 3

[0124] The difference between Comparative Example 3 and Example 1 lies in the different viscosity of the poly(dimethyldiallylammonium chloride) solution.

[0125] The viscosity of the poly(dimethyldiallylammonium chloride) solution in this comparative example is 0.4 dL / g, and the preparation method is as follows:

[0126] 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 min. Next, 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 the reaction for 1.5 h. Then, raise the temperature to 60 °C and react for 1.5 h. After that, cool to obtain a poly(dimethyldiallylammonium chloride) solution with a viscosity of 0.4 dL / g (concentration: 40 wt%).

[0127] Comparative Example 4

[0128] The difference between Comparative Example 4 and Example 1 lies in the different viscosities of the poly(dimethyldiallylammonium chloride) solution.

[0129] The viscosity of the poly(dimethyldiallylammonium chloride) solution in this comparative example is 1.3 dL / g, and the preparation method is as follows:

[0130] 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 min. Next, 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 the reaction for 3 h. Then, raise the temperature to 70 °C and react for 3 h. After that, cool to obtain a poly(dimethyldiallylammonium chloride) solution with a viscosity of 1.3 dL / g (concentration: 40 wt%).

[0131] Comparative Example 5

[0132] 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:

[0133] Add 3 kg of hydrochloric acid with a concentration of 20 wt% 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 sodium sulfide liquid with a concentration of 10% (wt%) 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%.

[0134] Comparative Example 6

[0135] The difference between Comparative Example 6 and Example 1 is that no poly(dimethyldiallylammonium chloride) solution is added, and the others are the same.

[0136] In this comparative example, the following raw materials are weighed according to the mass ratio: 500 parts of polyaluminum chloride solution, 200 parts of ferric sulfate, and 1.5 parts of ammonium sulfate.

[0137] Comparative Example 7

[0138] The difference between Comparative Example 7 and Example 1 is that ammonium sulfate was not added, and the others were the same.

[0139] The following raw materials were weighed according to the mass parts ratio in this comparative example: 500 parts of polyaluminum chloride solution, 200 parts of ferric sulfate, and 5 parts of polydimethyldiallylammonium chloride solution.

[0140] Comparative Example 8

[0141] The difference between Comparative Example 8 and Example 1 is that ferric sulfate was not added, and the others were the same.

[0142] The following raw materials were weighed according to the mass parts ratio in this comparative example: 500 parts of polyaluminum chloride solution, 1.5 parts of ammonium sulfate, and 5 parts of polydimethyldiallylammonium chloride solution.

[0143] Comparative Example 9

[0144] The difference between Comparative Example 9 and Example 1 is that the polydimethyldiallylammonium chloride in this comparative example was commercially available, and the others were the same.

[0145] The following raw materials were weighed according to the mass parts ratio in this comparative example: 500 parts of polyaluminum chloride solution, 200 parts of ferric sulfate, 1.5 parts of ammonium sulfate, and 5 parts of polydimethyldiallylammonium chloride.

[0146] The polydimethyldiallylammonium chloride in this comparative example was sourced from Wuxi Lanbo Chemistry, with the brand BLUWAT liquid.

[0147] Comparative Example 10

[0148] The difference between Comparative Example 10 and Example 1 is that in Comparative Example 10, commercially available equivalent polyaluminum chloride was directly used to replace the polyaluminum chloride solution, and the others were the same.

[0149] The following raw materials were weighed according to the mass parts ratio in this comparative example: 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.

[0150] Test Example

[0151] The sludge to be treated was the raw municipal sludge untreated with chemicals, with a sludge concentration of 4%. The sludge conditioning method was as follows:

[0152] 1) Add 30 m 3 of the above sludge to a 50 m 3 sludge conditioning tank, and add the same dosage of 120 kg of medicine to the sludge for conditioning respectively. The conditioning conditions were the same, and the stirring and conditioning time was 15 minutes.

[0153] 2) Use a plate and frame filter press with a filtration area of 200 square meters to carry out pressure filtration and dehydration on the above-conditioned sludge respectively. The dehydration conditions are the same, which are the sludge feeding time of 90 minutes, the dehydration pressing time of 60 minutes, and the pressing pressure of 1.5 MPa;

[0154] 3) Take mud cakes with the same thickness to detect the moisture content of the sludge, and the test results are shown in Table 1.

[0155] Table 1

[0156]

[0157] 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.

[0158] 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 is effectively improved.

[0159] 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.

[0160] 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.

[0161] 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 polydimethyldiallylammonium chloride solution to be (40-140):1, further improving the dehydration efficiency.

[0162] Comparing Comparative Examples 1, 6 with Examples 3-4, it can be seen that the present invention controls the dosage of each raw material as: 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, effectively improving the dehydration efficiency.

[0163] Comparing Comparative Examples 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%, effectively improving the dehydration efficiency.

[0164] 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 raw materials include the following parts by mass: 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 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 polymerization degree is 10 - 45%.

2. The composite flocculant according to claim 1, wherein 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.

3. The composite flocculant according to claim 1, characterized in that, The alumina content of the polyaluminum chloride solution is 12 - 14 wt%, the polymerization degree is 20 - 30%, and the polyaluminum chloride solution does not contain calcium element.

4. The composite flocculant according to claim 1, wherein 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 (40 - 140):

1.

5. The composite flocculant according to claim 1, characterized in that, The preparation method of the polydimethyldiallylammonium chloride solution includes the following steps: Add a dimethyldiallylammonium chloride solution with a concentration of 38 - 42 wt% into the reaction kettle, continuously introduce 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 the polydimethyldiallylammonium 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 polyaluminum chloride solution includes the following steps: Add a hydrochloric acid solution with a concentration of 20 - 30 wt% into the reaction kettle, continuously introduce inert gas into the reaction kettle for 5 - 15 min, add deammoniated aluminum ash, react at 100 - 105 °C for 180 - 240 min, add sodium sulfide solution, stir evenly, filter to obtain the 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).

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

8. The preparation method of the composite flocculant according to any one of claims 1 to 7, characterized in that, It includes the following steps: Mix the polyaluminum chloride solution, ferric sulfate, and stabilizer evenly, then add the polydimethyldiallylammonium chloride solution, stir evenly, and spray dry to obtain the composite flocculant.

9. The preparation method of the composite flocculant according to claim 8, characterized in that, The temperature of the spray drying is 200 - 260 °C.

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

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