CN110817926B - Method for directly preparing alpha-semi-hydrated gypsum by using titanium dioxide waste acid - Google Patents
Method for directly preparing alpha-semi-hydrated gypsum by using titanium dioxide waste acid Download PDFInfo
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- CN110817926B CN110817926B CN201911062602.9A CN201911062602A CN110817926B CN 110817926 B CN110817926 B CN 110817926B CN 201911062602 A CN201911062602 A CN 201911062602A CN 110817926 B CN110817926 B CN 110817926B
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- C01F11/00—Compounds of calcium, strontium, or barium
- C01F11/46—Sulfates
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B11/00—Calcium sulfate cements
- C04B11/26—Calcium sulfate cements strating from chemical gypsum; starting from phosphogypsum or from waste, e.g. purification products of smoke
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Abstract
A method for directly preparing alpha-semi-hydrated gypsum by using titanium dioxide waste acid comprises the following steps of a, filtering acid waste water generated in the production process of titanium dioxide to remove insoluble impurities, adjusting the concentration of acid to 6-10%, heating to 80-95 ℃, adding a crystallization auxiliary agent and an auxiliary agent, and mixing; b. continuously pumping the uniformly mixed solution into a tubular reactor, simultaneously continuously adding the ground 100-mesh and 300-mesh soda lime or calcium oxide into the tubular reactor by using a high-pressure feeding device according to a certain amount to obtain a reaction stock solution, wherein the pH value of the reaction stock solution is 7-9, and the reaction is continuously carried out for 10-120 min in the tubular reactor at the temperature of 90-160 ℃ and under the pressure of 0.1-1.0 MPa to generate alpha-hemihydrate gypsum slurry; c. drying the prepared alpha-hemihydrate gypsum slurry to obtain an alpha-gypsum crystal powder product. By adopting the direct neutralization technology under the high-temperature and high-pressure environment, the reaction stock solution is directly formed into the alpha-semi-hydrated gypsum, the production period is shorter, and the prepared alpha-semi-hydrated gypsum product has better stability.
Description
Technical Field
The invention relates to the field of production of alpha-semi-hydrated gypsum, in particular to a method for directly preparing alpha-semi-hydrated gypsum by using titanium white waste acid.
Background
The development of the titanium dioxide industry in China is rapid and is the biggest titanium dioxide producing country in the world, but due to the restriction of production equipment and technology, the problems of large three-waste by-products, most of the waste products cannot be recycled and the like exist, the huge pressure of recycling economy and clean production is faced, and particularly, the produced titanium white gypsum waste residue is subjected to high-benefit resource treatment and application technology to be developed.
At present, the resource utilization of the titanium white gypsum is realized by taking the existing titanium white gypsum as a research source point for technical development and research, the main components of the titanium white gypsum are dihydrate gypsum and beta-semi-hydrate gypsum, the utilization is difficult, for example, the acid wastewater generated in the production of the titanium white is directly taken as a source point to be converted into the alpha-semi-hydrate gypsum with excellent performance and higher value, and the resource utilization problem of the titanium white gypsum is solved.
The preparation processes of the alpha-hemihydrate gypsum which are popularized and applied are roughly divided into a gas phase steam pressure method and a liquid phase steam pressure method. The process comprises the steps of placing a dihydrate gypsum raw material into a closed container, adding a crystallization auxiliary agent, and controlling the dihydrate gypsum to be in a certain pressure and temperature range, so that the dihydrate gypsum is subjected to conversion reaction for a period of time to obtain the alpha-hemihydrate gypsum. The processes mostly adopt intermittent operation, and have long production period, large energy consumption and high cost. In China, a reliable technology for directly and continuously preparing alpha-hemihydrate gypsum by directly utilizing waste acid generated in the production process of titanium dioxide is lacked.
Disclosure of Invention
The invention provides a method for directly preparing alpha-semi-hydrated gypsum by using titanium dioxide waste acid, which overcomes the defects of the prior art, and changes the traditional method for preparing alpha-gypsum crystals by firstly converting the acidic waste water generated in the titanium dioxide production process into titanium dioxide gypsum through directly using the acidic waste water generated in the titanium dioxide production process. The production process is closed, automatic and continuous, the process flow is simple and easy to control, the production period is greatly shortened, the energy consumption is low, and the cost is low. The method achieves the purposes of completely recycling waste acid generated in the production process of titanium dioxide and not generating titanium white gypsum to pollute the environment.
The invention relates to a method for directly preparing alpha-semi-hydrated gypsum by using titanium dioxide waste acid, which comprises the following steps:
a. filtering acidic wastewater generated in the production process of titanium dioxide to remove insoluble impurities, adjusting the concentration of acid to 6-10%, heating to 80-95 ℃, adding a crystallization aid and an aid, and mixing;
b. continuously pumping the uniformly mixed solution into a tubular reactor, simultaneously continuously adding the ground 100-mesh and 300-mesh soda lime or calcium oxide into the tubular reactor by using a high-pressure feeding device according to a certain amount to obtain a reaction stock solution, wherein the pH value of the reaction stock solution is 7-9, and the reaction is continuously carried out for 10-120 min in the tubular reactor at the temperature of 90-160 ℃ and under the pressure of 0.1-1.0 MPa to generate alpha-hemihydrate gypsum slurry;
c. drying the prepared alpha-hemihydrate gypsum slurry to obtain an alpha-gypsum crystal powder product.
Further, the reaction is carried out under the conditions of pH value of 7-9, temperature of 90-160 ℃ and pressure of 0.1-1.0 MPa, and the generated calcium sulfate directly forms alpha-hemihydrate gypsum.
Further, the crystallization auxiliary agent is one or more of ferric sulfate, aluminum sulfate, magnesium sulfate, potassium chloride, magnesium chloride, alum, sodium citrate and gelatin, and the preparation concentration of the crystallization auxiliary agent is 0.1-5.0 wt% of the total mass of titanium white waste acid and calcium oxide in the reaction stock solution.
Further, the auxiliary agent is one or more of EDTA, citric acid, aminoacetic acid and sodium thiosulfate, and the preparation concentration of the auxiliary agent is 0.1 wt% -1.0 wt% of the total mass of the titanium white waste acid and the calcium oxide in the reaction stock solution.
Further, the drying mode is any one of spray drying, plate-and-frame filter-press drying, centrifugal airflow drying and flash evaporation drying.
Further, the drying temperature is 100-150 ℃.
Furthermore, the tubular reactor is formed by connecting communicated tubular pipelines for feeding slurry to flow.
Further, the continuous reaction lasts for 10min-80 min.
Further, the continuous reaction temperature in the tubular reactor is 110-150 ℃.
Further, the continuous reaction pressure in the tubular reactor is 0.3MPa-0.8 MPa.
Furthermore, the crystal morphology of the alpha-hemihydrate gypsum is 0.5-1.5 μm in diameter and 7:1-2:1 in length-diameter ratio.
The method for directly preparing the alpha-semi-hydrated gypsum by using the titanium white waste acid has the following advantages:
1. the waste acid generated in the production process of the titanium pigment is completely recycled, so that the pollution of the waste acid to the environment is avoided;
2. by adopting a direct neutralization technology in a high-temperature and high-pressure environment, the reaction stock solution directly forms the alpha-hemihydrate gypsum, the production period is shorter, and the prepared alpha-hemihydrate gypsum product has better stability;
3. the tubular reactor is used for continuous production, the production efficiency is high, the process is simple and convenient, and the control is easy;
4. in the production process, the alpha-semi-hydrated gypsum with different crystal forms, the diameter of which is 0.5 to 1.5 mu m and the length-diameter ratio of which is 7:1 to 2:1, is prepared by adjusting the types and the dosages of the crystallization auxiliary agent and other auxiliary agents under the condition of the same technological parameters.
Drawings
FIG. 1 is a schematic flow chart of a method for directly preparing alpha-hemihydrate gypsum by using titanium white waste acid.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments obtained by a person of ordinary skill in the art based on the embodiments of the present invention without any creative effort belong to the protection scope of the present invention.
Example 1:
as shown in fig. 1, acidic wastewater generated in the production process of titanium dioxide is filtered to remove insoluble impurities, and is conveyed to a mixing tank, the concentration of acid is adjusted to 8%, an auxiliary agent and a crystallization auxiliary agent are added, the preparation concentration of the auxiliary agent is 0.6 wt% of the total mass of titanium white waste acid and calcium oxide in the reaction stock solution, and the auxiliary agent comprises: the ethylene diamine tetraacetic acid and the sodium thiosulfate specifically comprise the following components: 0.3 wt% of ethylenediamine Tetraacetic Acid (EDTA for short) and 0.3 wt% of sodium thiosulfate. The preparation concentration of the crystallization auxiliary agent is 0.6 wt% of the total mass of titanium white waste acid and calcium oxide in the reaction stock solution, and the crystallization auxiliary agent comprises: alum, potassium chloride and sodium citrate, which specifically comprise the following components: 0.2 wt% of alum, 0.1 wt% of magnesium sulfate and 0.3 wt% of sodium citrate. Solution after the misce bene heats to 90 ℃, is carried to tubular reactor neutralization preheating section by the high-pressure pump, and the 200 mesh calcium oxide of measurement simultaneously adds tubular reactor neutralization preheating section through high-pressure feeding device, takes place neutralization reaction with the spent acid of pump-in according to the measurement and obtains the reaction stoste, and the pH value of reaction stoste is 8, tubular reactor constitutes for the tubular pipe connection of the feed thick liquid flow of intercommunication, continuous reaction does through the automatic flow in tubular reactor in time with the spatial continuous reaction, make reaction efficiency higher. Heating to 140 ℃ for 20min, entering a crystallization section, crystallizing at 140 ℃ and under 0.5MPa, and reacting for 30min to convert the product into alpha-semi-hydrated gypsum. And directly feeding the slurry crystallized in the tubular reactor into a flash evaporation kettle for flash evaporation, wherein the flash evaporation temperature of the alpha-hemihydrate gypsum slurry is 110 ℃ during flash evaporation. And (3) the slurry after flash evaporation enters centrifugal separation equipment for centrifugal dehydration, and the temperature of the separation equipment is 100 ℃ when the alpha-hemihydrate gypsum slurry is separated. And (3) drying the dehydrated material in vacuum paddle drying equipment with a crusher to obtain a powdery product, wherein the drying temperature of the alpha-semi-hydrated gypsum slurry is 130 ℃ during drying, and then grinding and packaging.
Example 2:
filtering acid wastewater generated in the production process of titanium dioxide, removing insoluble impurities, conveying to a mixing tank, adjusting the concentration of acid to 10%, adding an auxiliary agent and a crystallization auxiliary agent, wherein the preparation concentration of the auxiliary agent is 1.0 wt% of the total mass of titanium dioxide waste acid and soda lime in a reaction stock solution, and the auxiliary agent comprises: the ethylene diamine tetraacetic acid and the sodium thiosulfate specifically comprise the following components: ethylenediaminetetraacetic Acid (EDTA) 0.5 wt%, sodium thiosulfate 0.5 wt%. The preparation concentration of the crystallization auxiliary agent is 5.0 wt% of the total mass of titanium dioxide waste acid and soda lime in the reaction stock solution, and the crystallization auxiliary agent comprises: alum, potassium chloride and sodium citrate, which specifically comprises the following components: 1.5 wt% of alum, 1.0 wt% of magnesium sulfate and 2.5 wt% of sodium citrate. The solution after being uniformly mixed is heated to 90 ℃, the solution is conveyed to a neutralization preheating section of a tubular reactor by a high-pressure pump, simultaneously metered 100-mesh soda lime is added into the neutralization preheating section of the tubular reactor through a high-pressure feeding device, and is subjected to neutralization reaction with pumped waste acid according to the metering to obtain reaction stock solution, the pH value of the reaction stock solution is 9, the tubular reactor is formed by connecting communicated tubular pipelines for feeding slurry to flow, and the reaction efficiency is higher. Heating to 160 ℃ for 25min, entering a crystallization section, crystallizing at the temperature of 160 ℃ and under the pressure of 1.0MPa, and reacting for 20min to convert the product into alpha-semi-hydrated gypsum. And directly feeding the slurry crystallized in the tubular reactor into a flash evaporation kettle for flash evaporation, wherein the flash evaporation temperature of the alpha-hemihydrate gypsum slurry is 120 ℃ during flash evaporation. And (3) centrifugally dewatering the flash-evaporated slurry in centrifugal separation equipment, wherein the temperature of the separation equipment is 110 ℃ when the alpha-hemihydrate gypsum slurry is separated. And (3) drying the dehydrated material in vacuum paddle drying equipment with a crusher to obtain a powdery product, wherein the drying temperature of the alpha-hemihydrate gypsum slurry is 100 ℃ during drying, and the drying temperature is 130 ℃ in another embodiment, so that the alpha-hemihydrate gypsum crystal powder product can be obtained.
Example 3:
filtering acid wastewater generated in the production process of titanium dioxide, removing insoluble impurities, conveying to a mixing tank, adjusting the concentration of acid to 6%, adding an auxiliary agent and a crystallization auxiliary agent, wherein the preparation concentration of the auxiliary agent is 0.1 wt% of the total mass of titanium dioxide waste acid and calcium oxide in a reaction stock solution, and the auxiliary agent comprises: the ethylene diamine tetraacetic acid and the sodium thiosulfate specifically comprise the following components: 0.3 wt% of ethylenediamine Tetraacetic Acid (EDTA for short) and 0.3 wt% of sodium thiosulfate. The preparation concentration of the crystallization auxiliary agent is 0.1 wt% of the total mass of titanium white waste acid and calcium oxide in the reaction stock solution, and the crystallization auxiliary agent comprises: alum, potassium chloride and sodium citrate, which specifically comprises the following components: 0.03 wt% of alum, 0.02 wt% of magnesium sulfate and 0.05 wt% of sodium citrate. The solution after being uniformly mixed is heated to 90 ℃, the solution is conveyed to a neutralization preheating section of a tubular reactor by a high-pressure pump, simultaneously metered 300-mesh calcium oxide is added into the neutralization preheating section of the tubular reactor through a high-pressure feeding device and is subjected to neutralization reaction with pumped waste acid according to the metering to obtain reaction stock solution, the pH value of the reaction stock solution is 7, the tubular reactor is formed by connecting communicated tubular pipelines for feeding slurry to flow, and the reaction efficiency is higher. Heating to 95 ℃ for 10min, entering a crystallization section, crystallizing at the temperature of 95 ℃ and under the pressure of 0.1MPa, and reacting for 120min to convert the product into alpha-hemihydrate gypsum. Drying the slurry crystallized in the tubular reactor in a centrifugal airflow drying mode, wherein the drying temperature of the alpha-semi-hydrated gypsum slurry is 150 ℃ when the alpha-semi-hydrated gypsum slurry is dried, and finally obtaining the alpha-semi-hydrated gypsum crystal powder.
Claims (9)
1. A method for directly preparing alpha-hemihydrate gypsum by using titanium dioxide waste acid is characterized in that the method is used for preparing the alpha-hemihydrate gypsum with the diameter of 0.5-1.5 mu m and the length-diameter ratio of 7:1-2:1, and the method comprises the following steps:
a. filtering acidic wastewater generated in the production process of titanium dioxide to remove insoluble impurities, adjusting the concentration of acid to 6-10%, heating to 80-95 ℃, adding a crystallization aid and an aid, and mixing;
b. continuously pumping the uniformly mixed solution into a tubular reactor, simultaneously continuously adding the ground 100-mesh and 300-mesh soda lime or calcium oxide into a neutralization preheating section of the tubular reactor by using a high-pressure feeding device according to a certain amount to obtain a reaction stock solution, wherein the pH value of the reaction stock solution is 7-9, and the reaction is continuously carried out for 10min-120min in the tubular reactor under the conditions of the temperature of 90-160 ℃ and the pressure of 0.1MPa-1.0MPa to generate alpha-hemihydrate gypsum slurry;
c. and drying the prepared alpha-semi-hydrated gypsum slurry to obtain an alpha-gypsum crystal powder product.
2. The method for directly preparing alpha-hemihydrate gypsum by using titanium white waste acid according to claim 1, wherein the method comprises the following steps: the crystallization auxiliary agent is one or more of ferric sulfate, aluminum sulfate, magnesium sulfate, potassium chloride, magnesium chloride, alum, sodium citrate and gelatin, and the preparation concentration of the crystallization auxiliary agent is 0.1-5.0 wt% of the total mass of titanium white waste acid and calcium oxide in the reaction stock solution.
3. The method for directly preparing alpha-hemihydrate gypsum by using titanium white waste acid as claimed in claim 1, wherein the method comprises the following steps: the auxiliary agent is one or more of EDTA, citric acid, aminoacetic acid and sodium thiosulfate, and the preparation concentration of the auxiliary agent is 0.1-1.0 wt% of the total mass of the titanium white waste acid and the calcium oxide in the reaction stock solution.
4. The method for directly preparing alpha-hemihydrate gypsum by using titanium white waste acid according to claim 1, wherein the method comprises the following steps: the drying mode is any one of spray drying, plate-and-frame filter pressing drying, centrifugal airflow drying and flash evaporation drying.
5. The method for directly preparing alpha-hemihydrate gypsum by using titanium white waste acid according to claim 4, wherein the method comprises the following steps: the drying temperature is 100-150 ℃.
6. The method for directly preparing alpha-hemihydrate gypsum by using titanium white waste acid as claimed in claim 1, wherein the method comprises the following steps: the tubular reactor is formed by connecting communicated tubular pipelines for feeding slurry to flow.
7. The method for directly preparing alpha-hemihydrate gypsum by using titanium white waste acid as claimed in claim 1, wherein the continuous reaction is carried out for 10-80 min.
8. The method for directly preparing alpha-hemihydrate gypsum by using titanium white waste acid as claimed in claim 1, wherein the continuous reaction temperature in the tubular reactor is 110-150 ℃.
9. The method for directly preparing alpha-hemihydrate gypsum by using titanium white waste acid as claimed in claim 1, wherein the continuous reaction pressure in the tubular reactor is 0.3MPa to 0.8 MPa.
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| CN111320403B (en) * | 2020-03-31 | 2022-01-25 | 湖北大学 | Method for preparing multi-morphology alpha semi-hydrated gypsum through titanium dioxide waste acid and obtained gypsum |
| CN111484756B (en) * | 2020-05-22 | 2022-02-08 | 中信钛业股份有限公司 | Method for improving dispersion stability of alumina-coated titanium dioxide |
| CN113003599A (en) * | 2021-03-16 | 2021-06-22 | 深圳市长隆科技有限公司 | Process for producing high-strength gypsum by using sulfate ions in industrial wastewater |
| CN115159878B (en) * | 2022-05-26 | 2023-10-27 | 中南大学 | Method for preparing alpha-hemihydrate gypsum by circulating salt solution |
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