Preparation method for producing flocculating agent by utilizing industrial waste and side products and sewage treatment method thereof

Abstract

The invention discloses a preparation method for producing a flocculant by using industrial waste and side products, and relates to the technical field of preparation of flocculants and alkaline industrial sewage treatment. The method comprises the following steps: step 1, in a sulfuric acid method titanium dioxide production process, high-concentration waste acid and medium-concentration waste acid are generated in a water washing process; after the high-concentration waste acid is concentrated to 55-60%, solid-liquid separation is carried out, a filter cake and filtrate are separated out, and the filter cake is ferrous sulfate monohydrate; the filtrate is concentrated waste acid and is sent to a production system for recycling; and 2, adding the medium-concentration waste acid into a reaction tank, opening the reaction tank, stirring, adding ferrous sulfate monohydrate into the reaction tank, and heating to 45-50 DEG C by indirect steam to completely dissolve the solid, thereby obtaining the special flocculant product. The method is simple in process and low in production cost, and meanwhile, waste and auxiliary resources are utilized, clean production is realized, and waste is turned into wealth. The invention also relates to a sewage treatment method of the flocculant.

Description

Technical Field

[0001] The present invention relates to the technical field of flocculant preparation and alkaline industrial sewage treatment, and more specifically, it is a method for preparing a special flocculant by utilizing waste byproducts (waste sulfuric acid and ferrous sulfate monohydrate) generated in the production process of titanium dioxide by sulfuric acid method. The present invention also relates to a sewage treatment method using the flocculant. Background Art

[0002] In the production process of titanium dioxide by sulfuric acid method, a large amount of waste sulfuric acid with high, medium and low concentrations is produced in the washing process. The high-concentration waste acid comes from the upper acid (filtrate produced by solid-liquid separation of metatitanic acid) of the slurry (meta-titanic acid) after hydrolysis. The high-concentration waste acid contains H2SO4 300-310g / L, Fe 2+ 44-48g / L, 4-6 tons are produced per ton of titanium dioxide. Due to the high concentration of high-concentration waste acid, it has been effectively utilized to the maximum extent by being used as the initiator liquid for the main reaction of acidolysis, waste acid concentration, mixed acid, etc.; medium-concentration waste acid comes from the waste acid produced in the early stage of water washing of the upper filter cake (the filtrate in the early stage of water washing). The medium-concentration waste acid contains H2SO4200-250g / L, Fe 2+ 33-40g / L, 6-10 tons of medium-concentration waste acid is produced per ton of titanium dioxide. The concentration of medium-concentration waste acid is relatively high, and it has a certain comprehensive utilization value; low-concentration waste acid comes from the waste acid produced in the later stage of water washing of the upper filter cake (the filtrate from the early stage of water washing to the end of water washing). The low-concentration waste acid contains H2SO410-50g / L, Fe 2+ 1.5-4.5g / L, 15-20 tons of low-concentration waste acid is produced per ton of titanium dioxide. The concentration of low-concentration waste acid is low and the production volume is large. At present, there is no path for comprehensive utilization to directly neutralize and meet emission standards.

[0003] After the high-concentration waste acid is concentrated to 55-60%, solid-liquid separation is required. The main component of the separated filter cake is ferrous sulfate monohydrate (FeSO4·H2O), with a content of about 56% and free acid of about 11%, producing 0.7-0.9 tons per ton of titanium dioxide; this part can only be sent to pyrite for acid production and co-combustion to recover S and Fe elements; the separated filtrate (concentrated waste acid) is reused as the initiator liquid for the main reaction of acidolysis.

[0004] Waste sulfuric acid produced by water washing and ferrous sulfate monohydrate produced by waste acid concentration are two waste by-products produced in the production process of titanium dioxide by the sulfuric acid method. They are produced in large quantities and are difficult to utilize comprehensively.

[0005] Therefore, it is necessary to develop a method for preparing a special flocculant using waste by-products (waste sulfuric acid and ferrous sulfate monohydrate) generated during the production of titanium dioxide by the sulfuric acid process. Summary of the invention

[0006] The first object of the present invention is to overcome the shortcomings of the above-mentioned background technology and provide a method for preparing flocculants by utilizing industrial waste by-products.

[0007] The second purpose of the present invention is to overcome the shortcomings of the above-mentioned background technology and provide a method for treating sewage using such a flocculant.

[0008] In order to achieve the above first purpose, the technical solution of the present invention is: a method for preparing flocculants by using industrial waste by-products, characterized in that it comprises the following steps:

[0009] Step 1: During the production of titanium dioxide by sulfuric acid process, the washing process produces high-concentration waste acid and medium-concentration waste acid;

[0010] High concentration waste acid contains H2SO4300-310g / L, Fe 2+ 44-48g / L;

[0011] Medium concentration waste acid contains H2SO4200-250g / L, Fe 2+ 33-40g / L;

[0012] After the high-concentration waste acid is concentrated to 55-60%, solid-liquid separation is performed to separate the filter cake and filtrate. The filter cake is ferrous sulfate monohydrate; the filtrate is concentrated waste acid, which is sent to the production system for reuse;

[0013] Step 2: Add medium-concentration waste acid into the reaction tank, stir the reaction tank, then add ferrous sulfate monohydrate into the reaction tank, heat with indirect steam at 45-50°C to completely dissolve the solid, and obtain a special flocculant product;

[0014] In the above technical solution, in step 1, ferrous sulfate monohydrate contains 56% FeSO4·H2O and 11% free H2SO4.

[0015] In the above technical solution, in step 2, the indicators of the special flocculant product are ferrous sulfate mass fraction of 11.5-18.2%, ferrous mass fraction of 4.2-6.7%, free acid mass fraction of 16.0-20.8%, and density of ≥1.2-1.25g / cm 3 , 20℃, water insoluble matter ≤0.5%.

[0016] In the above technical solution, 0.82m 3 Add the medium-concentration waste acid into the reaction tank, start the reaction tank and stir, then add 90 kg of ferrous sulfate monohydrate into the reaction tank, heat it with indirect steam at 45-50°C to completely dissolve the solid, and produce 1 ton of special flocculant product that meets the indicators.

[0017] In the above technical solution, the above 0.70m 3Add the medium-concentration waste acid into the reaction tank, start the reaction tank and stir, then add 220 kg of ferrous sulfate monohydrate into the reaction tank, heat it with indirect steam at 45-50°C to completely dissolve the solid, and produce 1 ton of special flocculant product that meets the indicators.

[0018] In order to achieve the above second purpose, the technical solution of the present invention is: a method for treating sewage using a flocculant, characterized in that it comprises the following steps:

[0019] The special flocculant product is reacted with alkaline industrial sewage to achieve the treatment of alkaline industrial sewage;

[0020] The neutralization reaction between the special flocculant product and alkaline industrial sewage is:

[0021] 2NaOH+H2SO4→Na2SO4+H2O (1)

[0022] 2NaOH+FeSO4→Na2SO4+Fe(OH)2↓ (2)

[0023] The aeration flocculation reaction is:

[0024] 2FeSO4+O2→Fe2(SO)4 (3)

[0025] Fe2(SO)4+2NaOH→Fe(OH)3↓+Na2SO4 (4)

[0026] Fe(OH)2+O2→Fe(OH)3↓+H2O (5)

[0027] Ferric hydroxide plays a flocculation and sedimentation role in the system.

[0028] Compared with the prior art, the present invention has the following advantages:

[0029] 1) The process of the present invention is simple and the production cost is low. At the same time, waste by-product resource utilization, clean production, and waste into treasure are realized; the flocculant produced by the present invention is widely used in the treatment of alkaline industrial wastewater in the papermaking, printing and dyeing, leather and other industries, and is also suitable for the treatment of other discharged alkaline industrial wastewater.

[0030] 2) For alkaline industrial wastewater from industries such as papermaking, printing and dyeing, and leather, the present invention can be used to ensure that the pH value of discharged wastewater meets the requirements for industrial wastewater discharge by calculating the neutralization dosage of the special flocculant product according to the alkali content.

[0031] 3) The present invention converts two waste by-products generated in the production process of titanium dioxide by sulfuric acid method into a special flocculant product, which is simple to prepare and process and low in cost. It not only solves the problem of comprehensive utilization of waste by-products in the production process of titanium dioxide by sulfuric acid method, but also provides a solution for low-cost treatment of industrial wastewater in industries such as papermaking, printing and dyeing, and leather, achieving a win-win situation. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a process flow chart of the special flocculant product of the present invention;

[0033] Figure 2 It is a technical indicator diagram of the special flocculant product in the present invention. DETAILED DESCRIPTION

[0034] The following detailed description of the implementation of the present invention is made in conjunction with the accompanying drawings, but they do not constitute a limitation of the present invention and are only given as examples. At the same time, the advantages of the present invention will become clearer and easier to understand through the description.

[0035] Referring to the attached drawings, it can be seen that the method for preparing flocculants by using industrial waste by-products is characterized by comprising the following steps:

[0036] Step 1: During the production of titanium dioxide by sulfuric acid process, the washing process produces high-concentration waste acid and medium-concentration waste acid;

[0037] High concentration waste acid contains H2SO4300-310g / L, Fe 2+ 44-48g / L;

[0038] Medium concentration waste acid contains H2SO4200-250g / L, Fe 2+ 33-40g / L;

[0039] After the high-concentration waste acid is concentrated to 55-60%, solid-liquid separation is performed to separate the filter cake and filtrate. The filter cake is ferrous sulfate monohydrate; the filtrate is concentrated waste acid, which is sent to the production system for reuse;

[0040] Step 2: Add medium-concentration waste acid into the reaction tank, stir the reaction tank, then add ferrous sulfate monohydrate into the reaction tank, heat with indirect steam at 45-50°C to completely dissolve the solid, and obtain a special flocculant product;

[0041] In step 1, ferrous sulfate monohydrate contains 56% of FeSO4·H2O and 11% of free H2SO4.

[0042] In step 2, the indicators of the special flocculant product are ferrous sulfate mass fraction of 11.5-18.2%, ferrous mass fraction of 4.2-6.7%, free acid mass fraction of 16.0-20.8%, and density of ≥1.2-1.25g / cm 3, 20℃, water insoluble matter ≤0.5%.

[0043] 0.82m 3 Add the medium-concentration waste acid into the reaction tank, start the reaction tank and stir, then add 90 kg of ferrous sulfate monohydrate into the reaction tank, heat it with indirect steam at 45-50°C to completely dissolve the solid, and produce 1 ton of special flocculant product that meets the indicators.

[0044] The above 0.70m 3 Add the medium-concentration waste acid into the reaction tank, start the reaction tank and stir, then add 220 kg of ferrous sulfate monohydrate into the reaction tank, heat it with indirect steam at 45-50°C to completely dissolve the solid, and produce 1 ton of special flocculant product that meets the indicators.

[0045] A method for treating sewage using a flocculant, characterized in that it comprises the following steps:

[0046] The special flocculant product is reacted with alkaline industrial sewage to achieve the treatment of alkaline industrial sewage;

[0047] The neutralization reaction between the special flocculant product and alkaline industrial sewage is:

[0048] 2NaOH+H2SO4→Na2SO4+H2O (1)

[0049] 2NaOH+FeSO4→Na2SO4+Fe(OH)2↓ (2) The aeration flocculation reaction is:

[0050] 2FeSO4+O2→Fe2(SO)4 (3)

[0051] Fe2(SO)4+2NaOH→Fe(OH)3↓+Na2SO4 (4)

[0052] Fe(OH)2+O2→Fe(OH)3↓+H2O (5)

[0053] Ferric hydroxide plays a flocculation and sedimentation role in the system.

[0054] Other parts not described belong to the prior art.

Claims

1. A method for preparing a flocculant using industrial waste by-products, characterized in that: The following steps are involved: Step 1: During the production of titanium dioxide by sulfuric acid process, the washing process produces high-concentration waste acid and medium-concentration waste acid; High concentration waste acid contains H2SO4300-310g / L, Fe 2+ 44-48g / L; Medium concentration waste acid contains H2SO4200-250g / L, Fe 2+ 33-40g / L; After the high-concentration waste acid is concentrated to 55-60%, solid-liquid separation is performed to separate the filter cake and filtrate. The filter cake is ferrous sulfate monohydrate; the filtrate is concentrated waste acid, which is sent to the production system for reuse; Step 2: Add medium-concentration waste acid into the reaction tank, stir the reaction tank, then add ferrous sulfate monohydrate into the reaction tank, heat with indirect steam at 45-50°C to completely dissolve the solid, and obtain a special flocculant product.

2. The method for preparing flocculants by utilizing industrial waste by-products according to claim 1, characterized in that: In step 1, ferrous sulfate monohydrate contains 56% of FeSO4·H2O and 11% of free H2SO4.

3. The method for preparing flocculants by utilizing industrial waste by-products according to claim 2, characterized in that: In step 2, the indicators of the special flocculant product are ferrous sulfate mass fraction of 11.5-18.2%, ferrous mass fraction of 4.2-6.7%, free acid mass fraction of 16.0-20.8%, and density of ≥1.2-1.25g / cm 3 , 20℃, water insoluble matter ≤0.5%.

4. The method for preparing flocculants by utilizing industrial waste by-products according to claim 3, characterized in that: 0.82m 3 Add the medium-concentration waste acid into the reaction tank, start the reaction tank and stir, then add 90 kg of ferrous sulfate monohydrate into the reaction tank, heat it with indirect steam at 45-50°C to completely dissolve the solid, and produce 1 ton of special flocculant product that meets the indicators.

5. The method for preparing flocculants by utilizing industrial waste by-products according to claim 3, characterized in that: 0.70m 3 Add the medium-concentration waste acid into the reaction tank, start the reaction tank and stir, then add 220 kg of ferrous sulfate monohydrate into the reaction tank, heat it with indirect steam at 45-50°C to completely dissolve the solid, and produce 1 ton of special flocculant product that meets the indicators.

6. The method for treating sewage by using industrial waste to produce flocculants according to any one of claims 1 to 5, characterized in that: The following steps are involved: The special flocculant product is reacted with alkaline industrial sewage to achieve the treatment of alkaline industrial sewage; The neutralization reaction between the special flocculant product and alkaline industrial sewage is: 2NaOH+H2SO4→Na2SO4+H2O (1)2NaOH+FeSO4→Na2SO4+Fe(OH)2↓ (2) The aeration flocculation reaction is: 2FeSO4+O2→Fe2(SO)4 (3) Fe2(SO)4+2NaOH→Fe(OH)3↓+Na2SO4 (4) Fe(OH)2+O2→Fe(OH)3↓+H2O (5) Ferric hydroxide plays a flocculation and sedimentation role in the system.

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