CN1176024C - Comprehensive Utilization of Titanium Dioxide Waste Acid - Google Patents

Abstract

A comprehensive utilization method of titanium dioxide waste acid, which completely combines the comprehensive utilization of titanium dioxide waste acid with zinc hydrometallurgy technology, effectively solves the technical problem that titanium dioxide waste acid is difficult to handle and difficult to fully recover. The specific technical plan is: heat and hydrolyze the waste titanium dioxide acid, and return the metatitanic acid obtained from the hydrolysis to the main process of titanium dioxide production or use it to prepare titanium yellow powder; use the filtrate obtained from hydrolysis and zinc-containing oxides as raw materials, and adopt hydrometallurgical process Prepare active zinc oxide, basic zinc carbonate, ferric oxide and zinc-containing ammonium sulfate. Since the entire process is basically a wet closed-circuit cycle, it can comprehensively utilize titanium self-spent acid to prepare high-quality, high-value-added products without polluting the environment.

Description

Comprehensive Utilization of Titanium Dioxide Waste Acid

1. Technical field

The invention relates to a treatment method for waste acid produced by sulfuric acid production of titanium dioxide.

2. Background technology

There are two main production methods of titanium dioxide (titanium dioxide): the chloride method and the sulfuric acid method. Due to the limitation of raw materials in my country, the sulfuric acid method is mainly used. The biggest problem of the sulfuric acid method is that every ton of titanium dioxide produced will produce 5-7 tons of waste sulfuric acid with a concentration of about 20% and a large amount of dilute acid. Therefore, the treatment of waste acid is the key problem that must be solved in the preparation of titanium dioxide by the sulfuric acid method .

Regarding the treatment of titanium dioxide waste acid, my country's titanium dioxide manufacturers have various methods: including neutralization discharge, production of potassium sulfate, ammonium sulfate, magnesium sulfate and other salts, concentration and reuse, etc., but none of them are satisfactory methods , Either the input is large and the output is small, or the pollution is changed from one kind of pollution to another. Japan's Ishihara Corporation has proposed a "Ishihara method", that is, the production of artificial rutile with the waste acid produced by the sulfuric acid method of titanium dioxide; "Sichuan Nonferrous Metals", No. 3, 2001, P65), but judging from the content disclosed so far, there is still a problem of the treatment of waste acid containing high concentration iron.

3. Contents of the invention

Aiming at the problems existing in the prior art, the present invention proposes a comprehensive utilization method for treating waste acid produced by sulfuric acid method to produce titanium dioxide. Pollution; it can fully recover the acid, titanium and iron in the waste titanium dioxide acid, and prepare a variety of products with high quality and added value and large market demand.

The technical scheme of the invention is: treating the titanium white waste acid by utilizing the zinc hydrometallurgical process. First, the waste titanium dioxide acid is heated and hydrolyzed, and the metatitanic acid obtained from the hydrolysis is returned to the main process of titanium dioxide production or used to prepare titanium yellow powder. ammonium sulfate.

1. Titanium dioxide waste acid heating and hydrolysis

The chemical reaction formula of thermal hydrolysis of titanium dioxide waste acid: The process conditions are as follows: add crystal seeds, complete the reaction under stirring, control the temperature to make the waste titanium dioxide acid boil, and control the time to complete the hydrolysis reaction, generally 1.5 to 2.5 hours. The precipitated metatitanic acid obtained by hydrolysis is filtered, washed with acidified water until no iron can be detected, and then washed with pure water. If its physical and chemical properties are the same as the main process of titanium dioxide production, it can return to the main process; if its physical and chemical properties are different from the main process of titanium dioxide production or titanium yellow powder needs to be prepared, it will be used as a raw material for preparing titanium yellow powder.

2. Preparation of titanium yellow powder by metatitanic acid

The process steps of preparing titanium yellow powder from metatitanic acid are drying, calcination and crushing in sequence; drying and calcination is to dry the metatitanic acid filter cake obtained by filtering and washing and calcining to obtain titanium yellow, and the thermal decomposition chemical reaction of metatitanic acid calcining Mode: , the calcination temperature is 650-850°C, and the calcination time is 2-3 hours; grinding is to prepare titanium yellow into a powdered finished product.

3. Preparation of active zinc oxide from the filtrate

The process steps of preparing active zinc oxide from the filtrate are leaching, neutralization, filtering and washing, sinking alum, filtering and washing, secondary oxidation, filtering and washing, replacement, filtering and washing, ammonium precipitation, filtering and washing, drying, calcining and pulverizing. Leaching is to add zinc-containing oxides to the filtrate so that the large amount of sulfuric acid contained in the filtrate can be fully utilized. The main chemical reactions in the leaching process are:

            

The accompanying side effects are:

            

            

            

            

            

The process conditions of leaching: the reaction is completed under stirring, the temperature is controlled at 80°C-90°C, the pH at the end point is controlled at 1.5-1.8, and the time is 1-2 hours. Neutralization is to add a neutralizing agent to the mixed solution formed in the leaching process, and the final pH is controlled at 5 to 5.4 to facilitate the removal of impurities from the mixed solution formed in the leaching process. Alum sinking is to add ammonium persulfate to the filtrate after filtering and washing for preliminary removal of impurities (Pb, In, Ge, etc.), so that Fe ²⁺ is oxidized to Fe ³⁺ , and yellow ammonium jarosite is generated, which can purify and prepare active zinc oxide. Raw materials can also be used to obtain raw materials for the preparation of ferric oxide. The reaction formula of ammonium persulfate to oxidize Fe ²⁺ to Fe ³⁺ is as follows:

            

            

        

The amount of ammonium persulfate added is 90-100% of the theoretical amount required for ^Fe in the oxidation solution.

The generation reaction of jarosite is:

The technological conditions of sinking alum are: add seed crystals, complete the reaction under stirring, the temperature is 90°C~boiling, the time is 1~4 hours, add neutralizing agent to keep the pH of the reaction solution at 1.5~2, and sink the alum for the last half an hour to react The solution was adjusted to pH 4-4.5. Secondary oxidation is to add potassium permanganate solution to the filtrate of jarosite to oxidize and remove Mn ²⁺ and Fe ²⁺ . The main chemical reaction is:

       

       

The technical conditions of the secondary oxidation are as follows: the reaction is completed under stirring, the temperature is 60-70° C., the time is 40 minutes-1 hour, and the pH at the end is controlled at 4-4.5. Replacement is to add zinc powder to the filtrate that removes manganese slag and iron slag to further purify the solution. The main chemical reactions are as follows:

               

               

             

    

The technological conditions for replacement are: the reaction is completed under stirring, the amount of zinc powder added is 1.5-2 times of the theoretical amount, the temperature is controlled at 60-80°C, the final pH of the solution is 5-5.4, and the time is 1.5-2 hours. Ammonium precipitation is to add ammonium bicarbonate saturated liquid to the filtrate to filter out the replacement slag to obtain basic zinc carbonate, and its reaction formula is:

    

The process conditions for ammonium precipitation are: reaction temperature 40-50°C, pH control at the end point at 6.8-7.0, then temperature rise to 70-75°C and stirring for 1 hour, and finally heat preservation and precipitation at 60°C for 3-4 hours. Drying is to dry the basic zinc carbonate filter cake obtained by filtering and washing to make its water content less than 2.5%. Calcining is to thermally decompose basic zinc carbonate to obtain active zinc oxide. The reaction formula is as follows:

     

The calcination temperature is 450-500° C., and the calcination time is 2-3 hours. Crushing is to prepare the block active zinc oxide as a finished product.

4. Preparation of ferric oxide

The preparation of ferric oxide uses the jarosite obtained in the alum sinking process as a raw material, and the process steps are drying, calcining and crushing in sequence, the calcining temperature is 700-950 DEG C, and the calcining time is 2-2.5 hours. The thermal decomposition reaction formula during calcination is as follows:

        

The SO ₃ and SO ₂ produced by calcination can be absorbed by the ammonium bicarbonate liquid to generate ammonium sulfate liquid, which is used to prepare zinc-containing ammonium sulfate.

5. Preparation of zinc-containing ammonium sulfate

The preparation of zinc-containing ammonium sulfate takes the filtrate produced by filtering and washing basic zinc carbonate and the solution formed by absorbing sulfur trioxide and sulfur dioxide produced by calcined jarosite as raw materials, and the process steps are concentration, cooling crystallization and drying in sequence.

In addition to the above-mentioned comprehensive utilization scheme, part of the basic zinc carbonate obtained in the ammonium precipitation process can be used to prepare active zinc oxide after being filtered, washed and dried, and part of it can be used to prepare the finished product of basic zinc carbonate. If the basic zinc carbonate finished product is prepared, only the dried basic zinc carbonate needs to be pulverized as required.

In order to minimize environmental pollution, the ammonium bicarbonate liquid formed after the carbon dioxide produced by calcining basic zinc carbonate is absorbed by ammonia water can also be used as a supplementary raw material for the ammonium precipitation process.

In the above-mentioned comprehensive utilization scheme, the seed crystal used in the heating hydrolysis process is prepared by ammonia water and titanium white waste acid, and the addition amount of the seed crystal is 1 to 1.5% of the titanium dioxide (conversion) amount contained in the titanium white waste acid; the leaching process adds The zinc-containing oxide is zinc calcine or zinc fume or hot-dip galvanized ash after calcined alkali leaching; the neutralizing agent added in the neutralization process is ammonia water or ammonia water and zinc calcine, zinc fume, hot-dip galvanized ash, calcium carbonate The combination of any one of the powders; the seed crystal added in the alum sinking process is jarosite, and the neutralizing agent is ammonia water and/or basic zinc carbonate.

The present invention has the following beneficial effects:

1. The method provided can comprehensively recycle useful substances in titanium white waste acid, and prepare them into titanium yellow powder, active zinc oxide, ferric oxide, basic zinc carbonate and zinc-containing ammonium sulfate compound fertilizer, and the cost of the above products is low , high quality, has a strong market competitive advantage.

2. The entire technological process is basically a wet closed-circuit cycle, which effectively solves the problem of environmental pollution in the treatment of titanium dioxide waste acid.

3. The technology of zinc hydrometallurgy is mature, the equipment is conventional, and it is easy for industrial production.

4. Description of drawings

Fig. 1 is a kind of process flow diagram of the comprehensive utilization method of titanium dioxide waste acid proposed by the present invention;

Fig. 2 is another process flow diagram of the comprehensive utilization method of titanium dioxide waste acid proposed by the present invention.

5. Specific implementation

Example 1:

The process flow of the comprehensive utilization method of titanium dioxide waste acid in this example is shown in Figure 1, the titanium dioxide waste acid is heated and hydrolyzed, the metatitanic acid obtained from hydrolysis is used to prepare titanium yellow powder, and the filtrate obtained from hydrolysis is used to prepare active zinc oxide , iron red (Fe ₂ O ₃ ) and ammonium sulfate containing zinc.

(1) Heating hydrolysis of titanium dioxide waste acid

The components of the processed titanium dioxide waste acid and the content (percentage by weight) of each component are as follows:

H ₂ SO ₄ 20.3 Fe 2.4

Mg 0.5 Ca 0.0037

TiO ₂ 9.51 V 0.0009

Co 0.00095

The equipment used is a reaction kettle equipped with heating temperature control, condensation reflux device and stirrer. Technological conditions: add 1% seed crystals (percentage by weight), calculated according to _TiO2 content, the crystal seeds are prepared from ammonia water and titanium white waste acid, and the amount of ammonia water added is based on the terminal pH of the obtained titanium white waste acid reaching 2 to 4. limit; temperature boiling; stirring speed 120 rpm; time 2 hours.

(2) Preparation of titanium yellow powder

Filter the metatitanic acid precipitate obtained by hydrolysis, wash with sulfuric acid acidified water with pH 1.5 until no iron is detected, and then wash with pure water to obtain a metatitanic acid filter cake. Calcined at 800°C and 850°C for 2 hours and crushed into titanium yellow powder. Its TiO ₂ content is respectively 93.6%, 98.07%, 99.26% (percentage by weight), reaching China's national standard and ministerial standard GB1706-93, ZGB13004-90 indicators.

(3) Preparation of active zinc oxide

The filtrate obtained by hydrolysis is leached, neutralized, filtered and washed, alum sinked, filtered and washed, secondary oxidation, filtered and washed, replaced, filtered and washed, ammonium precipitation, filtered and washed, dried, calcined and crushed to obtain the finished product of active zinc oxide . Each of the above filtration and washing steps is washed with sulfuric acid acidified water with a pH of 5. The zinc-containing oxide added in the leaching process is a mixture of zinc flue powder and dust collection white powder, and its composition (weight percentage) is as follows: name Zinc flue powder Dust white powder Mixture (measured value) Proportion 30% 70% composition ZnO Ge In Pb Cl co ZnO ZnO content(%) 55 0.02-0.04 0.3 8-10 0.4 trace 80 73.114

The process conditions and process parameters are: zinc-containing oxide: titanium dioxide waste acid hydrolysis filtrate = 1:7 (weight ratio); temperature 85° C.; time 1 hour; stirring speed 120 rpm; end point pH 1.8.

The neutralizing agent added in the neutralization process is ammonia water and hot-dip galvanizing ash fine powder, and the pH at the end point is controlled at 5.2.

The technological conditions of sinking alum process are: temperature 95 ℃; Zn ²⁺ 103.9 grams/liter; ∑ Fe23.8 grams/liter; The addition of ammonium persulfate is 95% of theoretical amount; Crystal seed is jarosite, addition 150 g/L; the pH of the alum sinking is controlled at 1.8; the stirring speed is 120 rpm; the time is 4 hours; the neutralizing agent is basic zinc carbonate, and the pH is adjusted to 4 after 3.5 hours of sinking the alum.

The technological conditions of the secondary oxidation process are: temperature 60°C; stirring speed 120 rpm; 0.5% potassium permanganate solution oxidized for 1 hour, and the amount of potassium permanganate added should be limited to the color of the solution being purplish red for 5 minutes without discoloration , the final pH of the solution was controlled at 4.5.

The technical conditions of the replacement process are as follows: temperature 60°C; zinc powder dosage 2 times the theoretical amount; stirring speed 120 rpm; solution end point pH 5.4; time 1.5 hours.

The process conditions of the ammonium precipitation process are: ammonium precipitation temperature 40°C; end point pH 7.0; the amount of ammonium bicarbonate saturated liquid added is limited to the reaction liquid end point pH reaching 7.0; when the reaction liquid pH reaches 7.0, the temperature is raised to 70°C and stirred for 1 Hours, and finally 60 ° C heat sink for 4 hours.

The drying temperature in the drying step was 105°C.

The calcination temperature in the calcination step is 500° C., and the calcination time is 2 hours.

The active zinc oxide prepared in this example reaches the standard HG/T2572-94 issued by the Ministry of my country.

(4) Preparation of iron red (Fe ₂ O ₃ )

The filter cake formed by filtering and washing the jarosite obtained in the alum sinking process was dried at 110°C, calcined at 700°C, 750°C, 800°C, and ₈₅₀ °C for 2 hours and pulverized, and its _Fe2O3 content was 85.45%, 85.45%, 95.96%, 96.15%, and 98.2%, all of which reach the national standard GB1863-89 and the ministerial standard HG/T2574-94.

(5) Preparation of zinc-containing ammonium sulfate

The filtrate produced by filtering and washing basic zinc carbonate and the sulfur trioxide produced by calcining jarosite are absorbed by the ammonium bicarbonate solution to form a solution that is concentrated, cooled, crystallized, and dried to obtain zinc-containing ammonium sulfate. In the ammonium sulfate prepared in this example, N17.26%, Zn1.52%, also contains a small amount of NH ₄ Cl, MgCl ₂ and MgSO ₄ .

Calculated by treating 1 ton of titanium white waste acid, the quantities of various products prepared in this example are: titanium yellow powder 89kg, active zinc oxide 128kg, iron red (Fe ₂ O ₃ ) 35kg, zinc-containing ammonium sulfate 200kg.

Example 2:

The process flow of the comprehensive utilization method of titanium dioxide waste acid in this example is shown in Figure 2. The titanium dioxide waste acid is heated and hydrolyzed, and the metatitanic acid obtained from the hydrolysis is returned to the main process of titanium dioxide production, and the filtrate obtained from the hydrolysis is used to prepare active oxidation Zinc, basic zinc carbonate, iron red (Fe ₂ O ₃ ) and zinc ammonium sulfate.

The difference between this embodiment and embodiment 1 is as follows:

(1) The metatitanic acid obtained by hydrolysis is returned to the main process of titanium dioxide production.

(2) The zinc-containing oxide added in the leaching process of preparing basic zinc carbonate and active zinc oxide is formed by calcining and alkali leaching hot-dip galvanizing ash containing 77% zinc. The technical conditions of calcination are as follows: a calcination temperature of 500° C. and a calcination time of 2 hours. The technological conditions of alkaline leaching are: calcined zinc ash: 2% (NaOH+Na ₂ CO ₃ ) solution = 1:1 (weight ratio); normal temperature; and 6 hours. Alkali leaching is over, filtered and washed for later use.

(3) Half of the basic zinc carbonate obtained in the ammonium precipitation process is used to prepare active zinc oxide finished products after being filtered, washed and dried, and half is directly pulverized into basic zinc carbonate finished products.

(4) The carbon dioxide produced by calcining the basic zinc carbonate filter cake is absorbed by ammonia water to form ammonium bicarbonate liquid as a supplementary raw material for the ammonium precipitation process.

(5) The neutralizing agent used in the neutralization process of this embodiment is ammonia water and calcium carbonate powder.

Based on the calculation of treating 1 ton of titanium white waste acid, the quantities of various products prepared in this example are: 62 kg of active zinc oxide, 91 kg of basic zinc carbonate, 34 kg of iron red (Fe ₂ O ₃ ), and 202 kg of zinc-containing ammonium sulfate.

Claims (8)

1, a kind of comprehensive utilization method of titanium white waste acid, it is characterized in that: (1) Heat and hydrolyze the waste titanium dioxide acid, the metatitanic acid obtained from hydrolysis is returned to the main process of titanium dioxide production or used to prepare titanium yellow powder, and the filtrate obtained from hydrolysis is leached from zinc-containing oxide materials to prepare active zinc oxide, ferric oxide and zinc-containing sulfuric acid ammonium, (2) The heating and hydrolysis of titanium white waste acid should be completed with adding seed crystals and stirring. The temperature control is to make the titanium white waste acid boil, and the time control is limited to the completion of the hydrolysis reaction, which is 1.5 to 2.5 hours. (3) The process steps of preparing titanium yellow powder from metatitanic acid are drying, calcination and crushing in sequence. Drying and calcination is to dry the metatitanic acid filter cake obtained by filtering and washing and then calcining to obtain titanium yellow. The temperature of calcination is 650-850 ℃, the calcination time is 2 to 3 hours, and the pulverization is to prepare titanium yellow into a powdery finished product. (4) The process steps of preparing active zinc oxide from the filtrate are leaching, neutralization, filter washing, alum sinking, filter washing, secondary oxidation, filter washing, replacement, filter washing, ammonium precipitation, filter washing, drying, calcination, pulverization , leaching is to add zinc-containing oxides to the filtrate and complete the chemical reaction under stirring. The temperature is controlled at 80-90°C, the pH at the end is controlled at 1.5-1.8, and the time is 1-2 hours. Neutralization is formed in the leaching process. A neutralizing agent is added to the mixed solution, and the pH at the end point is controlled at 5 to 5.4. For sinking alum, ammonium persulfate is added to the filtrate after filtering and washing for preliminary impurity removal, so that Fe ²⁺ is oxidized to Fe ³⁺ , and jarosite is formed. The amount of ammonium persulfate added is 90-100% of the theoretical amount required for Fe ²⁺ in the oxidation solution. The reaction is completed by adding seeds and stirring. The temperature is controlled at 90°C to boiling, and the time is 1-4 hours. Keep the pH of the reaction solution at 1.5-2, and adjust the reaction solution to pH 4-4.5 in the last half an hour of sinking alum. The second oxidation is to add potassium permanganate solution to the filtrate of jarosite to oxidize and remove Mn ²⁺ and Fe ²⁺ , the reaction is completed under stirring, the temperature is controlled at 60-70°C, the time is 40 minutes to 1 hour, and the pH at the end is controlled at 4-4.5. The replacement is to add zinc powder to the filtrate that removes manganese slag and iron slag to purify solution, the reaction is completed under stirring, the amount of zinc powder added is 1.5 to 2 times the theoretical amount, the temperature is controlled at 60 to 80 °C, the pH of the solution end point is 5 to 5.4, and the time is 1.5 to 2 hours. The ammonium precipitation is to filter out the replacement residue Add saturated solution of ammonium bicarbonate to the filtrate, the reaction temperature is 40-50°C, the final pH is controlled at 6.8-7.0, then the temperature is raised to 70-75°C and stirred for 1 hour, and finally the base is obtained by heat preservation and precipitation at 60°C for 3-4 hours Formula zinc carbonate, drying is to dry the basic zinc carbonate filter cake obtained by filtering and washing, and calcination is to thermally decompose basic zinc carbonate to obtain active zinc oxide, the calcination temperature is 450-500 ℃, and the calcination time is 2-3 hours , crushing is to prepare the block active zinc oxide as a finished product, (5) Ferric oxide is calcined after drying the jarosite filter cake. The calcining temperature is 700-950° C., and the calcining time is 2-2.5 hours. The block-shaped ferric oxide obtained by calcining is pulverized into a finished product. (6) Zinc-containing ammonium sulfate is made by concentrating the solution formed by filtering and washing the filtrate produced by basic zinc carbonate and calcining jarosite and sulfur dioxide after being absorbed by ammonium bicarbonate solution, cooling and crystallizing, and drying. 2. The comprehensive utilization method of titanium dioxide waste acid according to claim 1, characterized in that the dried basic zinc carbonate filter cake becomes the finished product of basic zinc carbonate after crushing. 3. The comprehensive utilization method of titanium white waste acid according to claim 1 or 2, characterized in that the carbon dioxide produced by calcining basic zinc carbonate is absorbed by ammonia water to form ammonium bicarbonate liquid as a supplementary raw material for the ammonium precipitation process. 4. The method for comprehensive utilization of titanium white waste acid according to claim 1 or 2, characterized in that the seed crystals used in the heating hydrolysis process are prepared from ammonia water and titanium white waste acid, and the amount of seed crystals added is 1-1.5% of the amount of titanium dioxide contained. 5. The comprehensive utilization method of titanium white waste acid according to claim 3, characterized in that the used crystal seed in the heating hydrolysis process is prepared from ammonia water and titanium white waste acid, and the amount of the seed crystal added is the amount contained in the titanium white waste acid. 1-1.5% of the amount of titanium dioxide. 6. The comprehensive utilization method of titanium white waste acid according to claim 1 or 2, characterized in that the zinc-containing oxide added in the leaching process is zinc calcine or zinc fume or hot-dip galvanized ash after calcination and alkali leaching . 7. The comprehensive utilization method of titanium white waste acid according to claim 1 or 2, characterized in that the neutralizing agent added in the neutralization process is ammonia water or ammonia water and zinc calcine, zinc fume, hot-dip galvanizing ash, calcium carbonate A combination of any of the powders. 8. The comprehensive utilization method of titanium white waste acid according to claim 1 or 2, characterized in that the seed crystal added in the alum sinking process is jarosite, and the neutralizing agent is ammonia water and/or basic zinc carbonate.

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