CN1037762C - Process for producing compound poly-ferric aluminium sulfate - Google Patents

Abstract

A production method of composite polymeric iron-aluminum sulfate, which uses ferrous sulfate as raw material and aluminum nitrate as catalyst to carry out oxidation, hydrolysis and polymerization under acidic conditions for about one hour to obtain a compound with a basicity of more than 20%. Polymerized ferric aluminum sulfate, the production method has a short reaction time, basically eliminates environmental pollution, and has a good flocculation effect on sewage and waste water.

Description

Production method of composite polyferric aluminum sulfate

The present invention relates to the production method of the flocculant that is used for treating drinking water, waste water or sewage etc., relates to the production of the inorganic macromolecule flocculant (composite polyferric aluminum sulfate) that is used for treating drinking water, waste water or sewage etc. method.

Polymerized ferric sulfate is an inorganic polymer flocculant developed in recent years. Compared with traditional flocculants such as ferric oxide, aluminum sulfate, and ferric sulfate chloride, polyferric sulfate has the advantages of small dosage and high turbidity removal. High efficiency, good decolorization effect and so on. There are various production methods of polyferric sulfate, but they all include the oxidation, hydrolysis and polymerization of ferrous sulfate in acidic solution. According to different oxidation methods, the production methods of polyferric sulfate are divided into two categories: (1) Direct oxidation method, that is, using strong oxidants H ₂ O ₂ , NaClO, KClO ₃ , MnO _{2 ,} etc. to directly convert ferrous ions Oxidation to iron ions, followed by hydrolysis and polymerization to obtain polymerized ferric sulfate; (2) Catalytic oxidation method, that is, under the action of a catalyst, ferrous ions are oxidized to iron ions by air or oxygen, which is also obtained by hydrolysis and polymerization. iron sulfate. The direct oxidation method is difficult for industrialized production because of the large consumption of oxidant and the high cost, and the separation cost of the residue introduced by oxidant is relatively high, and the quality of the product will be affected if not separated.

At present, the production of polyferric sulfate at home and abroad generally adopts catalytic oxidation method, and NaNO ₂ and HNO ₃ are mainly used as catalysts. For example, Japanese Patent Publication 51-17516 discloses a production method of polyferric sulfate, which uses _FeSO4 as raw material, under certain temperature and pressure, _NaNO2 as catalyst, air oxidation, hydrolysis and polymerization to obtain polysulfuric acid iron. Publication No. CN1053222A (1991) Chinese patent application disclosed method is to use _HNO3 as catalyst and oxidant, _FeSO4 in the presence of _H3SO4 after oxidation, _hydrolysis , polymerization to obtain polyferric sulfate. There is following shortcoming in the method that prior art adopts above-mentioned catalyzer to produce polyferric sulfate:

(1) The reaction time is too long, requiring more than 17 hours, so that the equipment efficiency is low, the production efficiency is low, and the cost is high;

( ₂ ) take NaNO as catalyst The oxidation reaction when preparing polyferric sulfate is as follows:

            

It can be seen that nitrogen oxides are released during the reaction process, polluting the environment;

(3) prepare polyferric sulfate with _HNO3 as catalyst, need a large amount of _HNO3 , owing to use _HNO3 can produce the oxide compound of nitrogen, thereby increased the weight of the pollution to environment;

(4) These production methods all have great dependence to acidity, promptly the input amount of acid must be very big just can guarantee that ferric hydroxide precipitation does not occur in the final product mixture, and the input amount of acid increases and must reduce the salt of product Basis, thus affecting its flocculation effect.

The molecular formula of polyferric sulfate can be expressed as [Fe ₂ (OH) _n (SO ₄ ) _3-n/2 ] _m , and its corresponding basicity is n/6×100%. The higher the basicity of polyferric sulfate, that is, the larger n, the higher the degree of polymerization m of the product, the larger the alum flowers formed, the better the flocculation effect, and the faster the floc sedimentation speed. Our country stipulates that the basicity of the first-grade polyferric sulfate must reach more than 12%, and the basicity of the Japanese standard sample is 8.33-16.67%, and the polyferric sulfate products with a basicity of more than 16.67% have not been reported so far. Therefore, trying to improve the basicity of polyferric sulfate has become an important way to improve product quality.

Corresponding to polyferric sulfate, the molecular formula of composite polyferric aluminum sulfate can be expressed as Al _m Fe ₂ -k(OH) _n (SO ₄ ) _3-n/2 〕 _m . k≤2, the degree of basicity can be expressed as n/6×100%, and m is the degree of polymerization of the product.

The object of the present invention is to provide a kind of production method of composite polyferric aluminum sulfate, shorten reaction time, improve production efficiency, reduce cost.

The purpose of the present invention is also to provide a kind of production method of composite polyferric aluminum sulfate, adopt new catalyzer, just can complete whole reaction with very little consumption, so that substantially eliminate the oxide compound that emits nitrogen in the reaction process, reduce environmental pollution.

The more important purpose of the present invention is to provide a production method of composite polyferric aluminum sulfate, adopting a new catalyst, so that the dependence of the production method on acidity is greatly reduced, thereby significantly increasing the basicity and greatly improving the flocculation of the product Effect.

The production method of the invention uses ferrous sulfate as raw material and aluminum nitrate as a catalyst to obtain composite polymerized ferric aluminum sulfate product through oxidation, hydrolysis and polymerization under acidic conditions.

The catalyst used in the present invention is aluminum nitrate for industrial use, or the mixture of aluminum oxide or aluminum salt and nitric acid capable of forming aluminum nitrate.

Since the present invention uses aluminum nitrate as a catalyst, the product formed after the reaction contains aluminum to form composite polyferric aluminum sulfate. Practice has proved that the aluminum contained in polyferric sulfate products can promote the treatment of wastewater.

In fact, the inventor once used nitrates such as sodium nitrate, zinc nitrate, and manganese nitrate as catalysts, and the polyferric sulfate produced had no effect on treating wastewater, and the product also contained impurities such as sodium, zinc, and manganese. The contriver also selects pernitric acid, ferric nitrate as catalyst, and the polyferric sulfate that makes is pure product, but also has no unique performance. In the present invention, aluminum nitrate is not only a catalyst, but also a buffer, thereby significantly reducing the dependence of the reaction system on the acidity, so that the impact of the acidity on the reaction becomes less important; it is simultaneously An accelerator for hydrolysis and polymerization, which makes oxidation, hydrolysis and polymerization proceed simultaneously in a more balanced manner; aluminum nitrate is also a stable metal salt oxidant, which is characterized by a small amount, so it avoids the use of traditional production methods When polymerizing ferric sulfate, a large amount of nitrogen oxides must be discharged, which basically eliminates environmental pollution.

The specific implementation of the present invention is that 28.0%-32.0% by weight of ferrous sulfate, 4.5%-7.0% by weight of sulfuric acid, 1.0%-10.0% by weight of aluminum nitrate, and 51.0%-66.5% by weight of water are added to the reactor and stirred until Mix the components evenly, unscrew the oxygen valve, adjust the oxygen flow rate within the range of 5.4-18.0m ³ /h, and start heating, control the reaction temperature within the range of 110-150°C, and reduce the system pressure by adjusting the release valve Control it between 0.1-0.4MPa, and react for about one hour to produce a homogeneous, brown-red viscous composite polymeric iron and aluminum sulfate.

The ferrous sulfate used in the present invention can be industrial ferrous sulfate or ferrous sulfate-containing slag, waste residue, and the sulfuric acid used in the present invention can be industrial sulfuric acid or waste acid containing sulfuric acid.

Compared with the prior art, the present invention has the following advantages:

(1) Because the present invention adopts aluminum nitrate as a catalyst, the product produced contains aluminum components and becomes composite polymerized iron-aluminum sulfate, which promotes the treatment of waste water.

(2) The present invention can reduce or even avoid environmental pollution due to the use of a very small amount of aluminum nitrate catalyst to complete the entire reaction process.

(3) The production method of the present invention can alleviate the dependence of the reaction system on the acidity, thereby being able to produce products with a basicity of more than 20%.

(4) The reaction time of the method for producing composite polyferric aluminum sulfate of the present invention is short, about 1 hour, greatly improved production efficiency, and reduced cost.

The present invention will be further described below in conjunction with the examples.

Example 1

Put 629 kg of industrial ferrous sulfate, 90.2 kg of sulfuric acid, 37.4 kg of industrial aluminum nitrate and 1243.4 kg of water into the ^3m3 reaction kettle in sequence, start the mixer to mix the components quickly and evenly, and then slowly unscrew the oxygen valve to release the oxygen Adjust the flow rate at 5.4m ³ /h, start heating, control the reaction temperature within the range of 115-125°C, and control the system pressure between 0.1-0.35MPa by adjusting the purge valve. Then raise, then lower, so three cycles. The reaction ended within 42 minutes, and a homogeneous, brown-red viscous composite polymeric ferric aluminum sulfate product was obtained. The basicity was 20.59%, the total iron content was 170.4g/L, and no ferrous ions could be detected.

Example 2

Production method is with embodiment 1, and wherein the prescription of material is as follows:

  Ferrous sulfate: 606.8 kg

Sulfuric acid: 108.2 kg

  Aluminum nitrate: 113.4 kg

  Water: 1171.6 kg

The reaction conditions are as follows:

Oxygen flow rate: 9m ³ /h

Reaction temperature: 110-120°C

  System pressure: 0.14-0.35MPa

The reaction ended within 28 minutes, and a homogeneous, brown-red viscous composite polymeric ferric-aluminum sulfate product was obtained, with a basicity of 19.12%, a total iron content of 175.2g/L, and no ferrous iron detected. ion.

Example 3

Production method is with embodiment 1, and wherein the prescription of material is as follows:

  Ferrous sulfate: 573.8 kg

Sulfuric acid: 138.8 kg

  Aluminum nitrate: 194.4 kg

  Water: 1093.2 kg

The reaction conditions are as follows:

Oxygen flow rate: 14.4m ³ /h

  Reaction temperature: 135-145°C

  System pressure: 0.1-0.4MPa

The reaction was carried out for 22 minutes, and a homogeneous, brown-red viscous composite polymeric ferric aluminum sulfate product was obtained, the basicity of which was 19.98%, the total iron content was 168.5g/L, and no ferrous ions could be detected.

Example 4

Production method is with embodiment 1, and wherein the prescription of material is as follows:

  Ferrous sulfate: 629.0 kg

Sulfuric acid: 99.2 kg

   Aluminum nitrate: 22.6 kg

  Water: 1249.2 kg

The reaction conditions are as follows:

Oxygen flow rate: 18.0m ³ /h

Reaction temperature: 140-150°C

  System pressure: 0.14-0.35MPa

The reaction was carried out for 75 minutes, and a homogeneous, brown-red viscous composite polymeric ferric-aluminum sulfate product was obtained. The basicity was 19.43%, the total iron content was 172.9g/L, and no ferrous ions could be detected.

Table 1 is a comparison of the flocculation effect of the composite polymeric ferric aluminum sulfate flocculant produced by the method of the present invention and the polymeric ferric sulfate flocculant produced with _NaNO2 or _HNO3 as a catalyst.

Water from the Pearl River in Yuancun section was taken for testing, and the turbidity was 50ppm.

Measurement method: Take 1 liter of river water and put it into a 2 liter glass container, stir rapidly at 180rpm for 3 minutes, add flocculant, then stir slowly at 60rpm for 10 minutes, then let it stand for 20 minutes, take the supernatant to measure its turbidity Spend.

Table 1 serial number flocculant Basicity (%) Consumption (ppm) Outlet Turbidity (ppm) 1 The composite polymeric ferric aluminum sulfate of embodiment 1 20.59 10 2.7 2 The composite polymeric ferric aluminum sulfate of embodiment 2 19.12 10 2.9 3 The composite polymeric ferric aluminum sulfate of embodiment 3 19.98 10 2.3 4 The composite polymeric ferric aluminum sulfate of embodiment 4 19.43 10 4.1 5 Polyferric sulfate produced with HNO ₃ as catalyst 14.53 30 4.6 6 Polymerized ferric aluminum sulfate produced with _NaNO2 as catalyst 12.94 35 4.8

The data in Table 1 shows that the flocculation effect of the composite polyferric aluminum sulfate produced by the method of the present invention is obviously better than that of the existing flocculant polyferric sulfate.

Claims (1)

1. A production method of composite polymerized ferric aluminum sulfate, characterized in that 28.0%-32.0% weight ferrous sulfate, 4.5%-7.0% weight sulfuric acid, 1.0%-10.0% weight aluminum nitrate, 51.0-66.5% weight water Add it into the reaction kettle, stir until the components are evenly mixed, unscrew the oxygen valve, adjust the oxygen flow rate within the range of 5.4-18.0m ³ /h, and start heating, control the reaction temperature within the range of 110-150°C, and pass Adjust the release valve to control the system pressure between 0.1-0.4MPa for oxidation, hydrolysis and polymerization.