CN1830828A - Method of producing poly aluminium iron silicate composite flocculating agent using fly ash and ferrous sulphate - Google Patents

Abstract

The invention belongs to a polymer flocculant for water treatment, and relates to a method for producing a polyaluminum-iron silicate composite flocculant by using fly ash and ferrous sulfate. It consists of a three-step process of preparation of primary products, impregnation of primary products, and separation of products. The method of the present invention provides a new production process for preparing a high-efficiency composite flocculant with the solid waste fly ash of coal-fired power plants and the by-product ferrous sulfate produced from titanium dioxide as the main raw materials, which solves the problem of low raw material utilization and poor product stability , active silicate is easy to form gel and cause product failure; the process is simplified, the production time is greatly shortened, the investment is small, the operation cost is low, the product is stable, and the performance is good; at the same time, it is used for the production of fly ash and titanium dioxide The utilization of the by-product ferrous sulfate provides a new way, improves the comprehensive utilization rate of resources, and also reduces the production cost and sewage treatment cost of polyaluminum iron silicate, which has strong economic, environmental and social benefits.

Description

Method for producing polyaluminum-ferric silicate composite flocculant with fly ash and ferrous sulfate

1. Technical field

The invention belongs to a polymer flocculant for water treatment, in particular to a preparation method of polyaluminum iron silicate.

2. Background technology

At present, the polyaluminium-silicon flocculants developed at home and abroad can be roughly divided into two categories: one is the product made by introducing silicon into polyaluminum sulfate, such as polyaluminum-silicon sulfate flocculant (PASS); the other is Based on activated silicic acid, the product is made by adding aluminum salt, such as polyaluminum silicate (PSAS). The preparation process of the former is relatively complicated and has high requirements for raw materials and equipment; the preparation process of the latter is simple and cheap, but its effective concentration is low, its stability is poor, and it is difficult to commercialize. It is only suitable for on-site preparation and investment in water plants. add. Polyaluminum-iron silicate flocculant is a composite flocculant developed on the basis of polysilicate and traditional aluminum salts, iron salts and other flocculants. great concern.

At present, the annual discharge of fly ash from coal-fired power plants in my country has reached more than 100 million tons, while its utilization rate is only about 30%. A large amount of fly ash is accumulated in the ash yard, which not only occupies a large amount of land resources, but also seriously pollutes the environment. Therefore, the comprehensive utilization of fly ash has always been one of the hot topics in the field of environmental protection research. How to fully develop and utilize fly ash, increase the added value of its utilization, and turn waste into wealth is a difficult problem to be solved in the current technical field.

Since fly ash and polyaluminum iron silicate have similar elemental compositions, relevant researchers have explored the method of preparing polyaluminum iron silicate from fly ash.

On March 16, 2005, a Chinese invention patent application titled "Special Synthesis Process of Polyaluminum Iron Silicate" was published, and the publication number is CN1594082A. Its main technical content is: using fly ash and iron-making slag as the main raw materials, the preparation process includes eight steps including the preparation of polymerized aluminum-iron, polymerized silicic acid and polymerized aluminum-iron silicate. The process has the following disadvantages: it uses many raw and auxiliary materials, including fly ash, ironmaking slag, sodium hydroxide, sodium carbonate, sulfuric acid and hydrochloric acid; and has special requirements for raw materials, Fe ₂ O ₃ 20-40% ironmaking waste slag with 40-50% content, 4%-10% _Fe2O3 content, 20-30% _{Al2O3 content} , 40-60% _{SiO2 pulverized} coal Ash; the process is complicated, the preparation conditions are harsh, and it needs to be carried out under certain pressure conditions (0.5-0.6MPa). Therefore, if it is used for industrialization, its process equipment investment cost, production operation cost, etc. are all high, and the cost for wastewater treatment is too high.

3. Contents of the invention

The purpose of the present invention is to aim at the above-mentioned defects that exist in the prior art, propose to provide a kind of method that is different from the prior art scheme to produce polyaluminum iron silicate composite flocculant with fly ash and ferrous sulfate, make the auxiliary agent kind Less, simple process and conditions, less investment in production equipment, low operating costs, stable product performance, and good quality.

For realizing the purpose of the present invention, the technical scheme adopted is as follows.

A method for producing polyaluminum-ferric silicate composite flocculant with fly ash and ferrous sulfate, comprising using fly ash as raw material, characterized in that it consists of three steps:

(1) Preparation of primary products

Fully mix fly ash, ferrous sulfate, and industrial soda ash in a weight ratio of 1:0.8~1.2:0.5~0.8, then roast the mixture at a temperature of 800-900°C for 0.5-2 hours, and cool naturally to become primary product.

(2) Impregnation of primary products

The primary product prepared in step (1) and industrial hydrochloric acid with a volume ratio of 1:1 are stirred and impregnated at a temperature of 40-90°C for 2-4 hours at a weight ratio of 1:5-20, and then left to stand at room temperature for 1 -2 hours.

(3) Separation of products

The impregnated product aged in step (2) is subjected to centrifugal filtration and separation, and the filtrate is polyaluminum iron silicate product; the filter residue is unreacted fly ash, which is returned to step (1) for recycling as a raw material.

In the product obtained through the aforementioned process steps, the solid dissolution rate reaches 90%-95%, no gel occurs within 3 months, and the product performance is relatively stable.

The polyaluminum ferric silicate product prepared by the method of the present invention, through simulation and actual papermaking wastewater treatment flocculation test, the results show that the product has good flocculation effect, short settling time, and has better decolorization and COD removal effect than similar products. The rate is 92.9%, and the COD removal rate is 84.1%. It is a new type of composite flocculant for water treatment.

Compared with the prior art, the method of the present invention provides a new production line for preparing high-efficiency composite flocculants of polyaluminum-ferric silicate by using fly ash as solid waste from coal-fired power plants and by-product ferrous sulfate produced from titanium dioxide as main raw materials. The technology solves the problems of low raw material utilization rate, poor product stability, and active silicate is easy to form gel, which leads to product failure; the process is simplified, the production time is greatly shortened, the investment is small, the operating cost is low, and the product stability is good. Excellent performance; at the same time, it provides a new way for the utilization of fly ash and ferrous sulfate, a by-product of the production of titanium dioxide, improves the comprehensive utilization of resources, and reduces the production cost and sewage treatment cost of polyaluminum iron silicate. Strong economic, environmental and social benefits.

4. Specific implementation

A number of examples are listed below to further illustrate the specific implementation of the method of the present invention, and the good effect of the example products on treating papermaking wastewater. It is pointed out that the method of the invention is not limited to the examples given.

Example 1

Weigh 2.5Kg of fly ash, 2.5Kg of ferrous sulfate and 1.5Kg of soda ash and mix them thoroughly, then roast them at 850°C for 50 minutes, and cool to room temperature to obtain the primary product.

The primary product was impregnated with 70Kg of industrial hydrochloric acid with a volume ratio of 1:1 at 80°C for 3 hours, left to stand at room temperature for 2 hours, and centrifuged to obtain a liquid product, polyaluminosilicate iron, which did not appear after 3 months of storage. gel.

Example 2

Weigh 2.5Kg of fly ash, 2.5Kg of ferrous sulfate and 2Kg of soda ash and mix them thoroughly, then roast them at 850°C for 40 minutes, and cool to room temperature to obtain the primary product.

The primary product was impregnated with 80Kg of industrial hydrochloric acid with a volume ratio of 1:1 at 70°C for 3 hours, left to stand at room temperature for 2 hours, and centrifuged to obtain a liquid product, polyaluminum iron silicate, which did not appear after 3 months of storage. gel.

Example 3

Weigh 2.5Kg of fly ash, 2.5Kg of ferrous sulfate and 2Kg of soda ash and mix them thoroughly, then roast them at 850°C for 30 minutes, and cool to room temperature to obtain the primary product.

The primary product was impregnated with 80Kg of industrial hydrochloric acid with a volume ratio of 1:1 at 60°C for 3 hours, left to stand at room temperature for 1 hour, and centrifuged to obtain a liquid product, polyaluminosilicate iron, which did not appear after 3 months of storage. gel.

Example 4

The product ferric aluminum silicate prepared in Example 3 and preserved for at least 2 months was used for the comparison experiment of treating actual papermaking wastewater with commercially available similar products, and the results are as follows: COD mg L ¹ Remaining CODmg·L ¹ Removal rate% Chroma/fold Remaining chroma/fold Decolorization rate polyaluminum iron silicate 378 60 84.1 280 20 92.9% PACs 378 74 80.4 280 35 87.5% PFS 378 78 79.4 280 40 85.7%

Note: PAC and PFS are commercially available polyaluminum chloride and polyferric sulfate, respectively.

It can be found from comparative experiments that polyaluminum ferric silicate has better decolorization and COD removal effects than similar commercially available products such as polyaluminum chloride and polyferric sulfate. In the experiment of treating simulated sewage, papermaking sewage and domestic sewage, it is also found that polyaluminum iron silicate has the characteristics of small dosage, large and dense alum flowers, layered floc settlement, fast settlement speed and good treatment effect.

Claims (1)

1, a kind of method with fly ash and ferrous sulfate production polyaluminum-iron-silicate composite flocculant, comprise using fly ash as raw material, it is characterized in that it is made up of three-step process: (one) the preparation of primary product, Fully mix fly ash, ferrous sulfate, and industrial soda ash in a weight ratio of 1:0.8~1.2:0.5~0.8, then roast the mixture at a temperature of 800-900°C for 0.5-2 hours, and cool naturally to become primary Product; (2) the impregnation of primary product, the primary product that step (1) is made and the industrial hydrochloric acid that volume ratio is 1: 1 are by weight 1: 5～20 under the temperature condition of 40-90 ℃ of stirring impregnation 2- 4 hours, then stand at room temperature and age for 1-2 hours; (3) separation of the product, the impregnated product after step (2) aging is subjected to centrifugal filtration and separation, the filtrate is the polyaluminum iron silicate product, and the filter residue is returned to the step (1) Recycling as raw materials.