3. The reductive bleaching washed well biasing titanate slurry was filtered through a leaf filter, with deionized water (preferably 40-60 deg.] C and containing 0.1% -2.0% of the acidic water) was washed with metatitanic acid, further ferrous sulfate wash until metatitanic Fe 2 0 3 containing less than 30 * 10 -6 qualified. After the solution is clarified, it is cooled to obtain a mixed solution of brownish-clear transparent titanium sulfate and ferric sulfate. Â Â Â X. Calculation of sulfuric acid and aluminum powder used for the preparation of trivalent titanium solution by acid dissolution and reduction of aluminum powder According to the theoretical calculation, the aluminum powder is required to be 11.26kg. However, some of the aluminum powder is consumed in the formation of hydrogen with sulfuric acid, so a theoretical amount of 150% is required to achieve a reduction rate of more than 90%. That is, about 1. 9kg of aluminum powder is required for the reduction of 100kg of Ti0 2 . 45Kg Lpg Gas Cylinder,Refillable Propane Gas Cylinder,Wholesale Lpg Gas Cylinder,48Kg Lpg Gas Bottle Jiangsu Minsheng Heavy Industries Co., Ltd. , https://www.chlorinecylinder.com
7. Operation steps, requirements, shortcomings and improvement suggestions for the bleaching of trivalent titanium solution
1. Addition of acid was dissolved in the water jacket qualified heated with stirring enamel Fanyingguo metatitanic acid and water, stirring to adjust the slurry concentration and containing about Ti0 2 300g / L (if made of rutile titanium dioxide, this When adding calcined seeds, then add a certain amount of industrial sulfuric acid, so that the sulfuric acid concentration of the slurry is between 40-50g / L, steam heated to 50-55 ° C, so that the high-iron hydroxide is dissolved into high-speed iron sulfate Solution.
2. Reduction According to Ti0 2 , add 0.4%-1.0% of trivalent titanium solution as reducing agent, continue stirring, continue heating, keep the temperature at 50-55 ° C for 1 h, and let all the high-sulfur sulfate reduce to ferrous sulfate. Sampling and measuring the trivalent titanium concentration (in terms of Ti0 2 ) in the slurry is 0.3-0.5 g/L, and cooling to 40 ° C or lower can be washed with water. When using a trivalent titanium solution, the solid impurities must be filtered out to ensure the quality of the bleaching. At the same time, the trivalent titanium ions are easily oxidized in the air, so when bleaching, the temperature of the slurry should not be too high, and the stirring during the heat preservation should not be too fast.
3. Washing will reduce the bleached metatitanic acid slurry, and filter it with a vacuum filter with a vacuum vacuum or a vacuum filter, then use sand or deionized water (preferably 40-50 ° C) containing 0.1% -2.0% aqueous sulfuric acid) was washed with metatitanic acid, further washed ferrous sulfate, in order to reduce the iron content, until the content of metatitanic acid Fe 2 0 3 is less than 0.003% is acceptable.
The disadvantages of the trivalent titanium solution bleaching are as follows: the preparation of the trivalent titanium solution requires separate equipment and increases the preparation workload, and the preparation process is complicated, and the preparation consumes large energy, consumes more acid, and has high cost. In order to overcome these shortcomings, a factory has made the following improvements: first add a small amount of metatitanic acid suspension to the bleaching pot, then add all the sulfuric acid for bleaching, and let the two react fully. After 30 minutes, start stirring and add separately. by people meter Ti0 2 to 0.5% aluminum powder and allowed to mix uniformly, i.e. solutions of trivalent titanium. Add all the remaining metatitanic acid. When adding the remaining metatitanic acid, the direct steam valve is opened, heated to about 85 ° C, and kept for 1.5-2 h to complete the bleaching process. Obviously, this method is a bleaching effect which is more satisfactory when it is bleached with aluminum powder and contains trivalent titanium bleaching ingredients. At the same time, the preparation process is simplified, and it is not necessary to separately prepare a trivalent titanium solution, and the bleaching pot is also a preparation pot of trivalent titanium, and it is not necessary to separately increase the preparation pot of trivalent titanium. Therefore, its energy consumption, acid consumption and cost are greatly reduced.
8. Can you use "pickling" instead of bleaching?
During the washing process of metatitanic acid, the impurity ferrous sulfate is oxidized by water-soluble oxygen to iron sulfate. When the pH of the washed acid is ≥1.5, the iron sulfate is hydrolyzed to form iron hydroxide precipitate mixed in the titanium. In acid. The purpose of bleaching is to dissolve the ferric hydroxide into ferric sulphate by adding sulfuric acid, and then reducing it to ferrous sulfate by adding a reducing agent. Since the acidity of the hydrolysis of ferrous sulfate is pH ≥ 6.5, the acidity in the metatitanic acid cannot be weakened to this extent, so the ferrous sulfate is not hydrolyzed to form a precipitate of ferrous hydroxide, so that the iron can be removed by washing with water. After knowing this principle, you can add a small amount of sulfuric acid to the washing water at the source by gradually increasing the pH value after washing. The pH of the washing water is not more than 1.5, so that the ferric sulfate will not be hydrolyzed. The iron hydroxide precipitate is mixed in the metatitanic acid, and there is no iron hydroxide in the metatitanic acid, so that it is not necessary to bleach. It can be seen that the pickling can prevent the hydrolysis of the iron salt, and can play a role equivalent to bleaching, and the bleaching process can be omitted. [next]
9. Method for preparing trivalent titanium solution by acid dissolution and aluminum reduction
The method for preparing a trivalent titanium solution by acid-dissolving and aluminum reduction is as follows: 180 g/L is prepared in an acid-resistant enamel pot at a ratio of H 2 S0 4 : Ti0 2 = 5:1 by washing with water-qualified metatitanic acid and sulfuric acid. The concentration is adjusted to obtain a titanium sulfate solution by stirring, and the acid dissolution process is actually a process of preparing a colloidal solution by using a "dissolution method" to become a titanium sulfate solution. In this process, the first step is to heat to boiling. As the water evaporates, the boiling point gradually rises. When the temperature reaches 120-125 ° C, the metatitanic acid colloidal particles are gradually acid-dissolved and dispersed into colloidal particles; the second step is During the incubation period, the dispersed colloidal particles are all dissolved. Its reaction formula is as follows:
During the preparation process, both Ti 4+ ions and peptized metatitanic acid microparticles are present in the solution. The ratio between the two is determined by the temperature, the duration of dissolution, the concentration of titanium, and the concentration of acid. In order to prevent the resulting agglomeration instability of the colloidal solution in the obtained titanium sulfate solution, so that precipitation is generated and cannot be further reduced, it is necessary to ensure that the ratio of acid to titanium of the slurry at the time of preparation is ≥5.
The titanium sulfate solution is cooled and diluted with water to about 80 g/L under stirring. Otherwise, the concentration is too high, the amount of the reducing agent is correspondingly increased, and the aluminum sulfate formed by the reaction crystallizes. When the temperature drops to 75-80 ° C, the aluminum powder is firstly adjusted to a slurry with water, and added in portions within 20 to 30 minutes to prevent a pan accident caused by the reaction. Continue to raise the temperature to 80-90 ° C, keep warm for 1 h, measure the trivalent titanium concentration after cooling, and filter the solution if necessary. The reduction rate is calculated as follows:
To reduce 100kg Ti0 2 and require aluminum powder xkg, the reaction formula is as follows: [next]
[Example] The present invention has a titanic acid slurry having a titanium dioxide concentration of 200 g/L of 1.5 m 3 , and if the aluminum bleaching requires a slurry sulfuric acid concentration of 70 g/L, the aluminum powder is added in an amount of 0.5% (calculated as Ti0 2 ), How many kiloliters of industrial sulfuric acid and how many kilograms of aluminum powder are needed at a concentration of 92%?
Solution: The required industrial sulfuric acid is:
70×1000×1.5=105(kg)
92% of industrial sulfuric acid is required:
105÷92%=114.13(kg)
The volume of industrial sulfuric acid required is:
114.13÷1.824=62. 57(L)
Need aluminum powder for:
200×1000×1.5×0.5%=1.5(kg)
5公斤。 Thus, 92% of industrial sulfuric acid 62. 57L and aluminum powder 1. 5kg.
XI. Advantages of directly using aluminum liquid after freezing and removing iron to obtain trivalent titanium solution and preparation method thereof
The advantage of directly reducing the aluminum (or zinc ) to reduce the aluminum (or zinc ) to obtain a trivalent titanium solution bleaching reducing agent is that the acid consumption is small, the solvent is short, no coalescence instability and easy operation. The method is characterized in that the concentration of the titanic acid slurry is controlled as high as possible, and the concentration of the free acid is as low as possible, so that the adsorption amount of the trivalent titanium on the metatitanic acid is increased to improve the bleaching effect. The preparation method is as follows.
(1) In order to prevent the aluminum sulfate formed by reduction with aluminum from crystallizing in the trivalent titanium solution, it is diluted with water in the titanium solution to control the total titanium concentration to about 80 g/L.
2 added total titanium amount of 1. 5-2.0 times of sulfuric acid.
3 The temperature is raised to 70 ° C, and the aluminum powder slurry uniformly mixed with water is slowly added in portions.
4 Control the reduction temperature at 80 °C.
5 After the reduction is completed, the temperature is kept at 85-90 ° C for 1 h. In order to prevent the trivalent titanium from being oxidized by air, the stirring should not be too fast.
6 Cool to room temperature and remove solid impurities by filtration to ensure bleaching quality.
7 Trivalent titanium is a strong reducing agent, which is easily oxidized by oxygen in the air to reduce the reduction effect, so the storage should not exceed 48 hours.
In order to reduce the cost of production, some manufacturers use iron powder instead of aluminum powder to prepare trivalent titanium solution. However, the trivalent titanium liquid prepared by this method has more impurities and has an impact on the quality of the finished product, so many manufacturers dare not use.
12. Reasons for not measuring trivalent titanium or measuring too high or too low trivalent titanium when bleaching metatitanic acid, adverse effects and remedial measures
In order to ensure that all the ferric iron in the metatitanic acid is reduced to ferrous iron, it is necessary to maintain a certain amount of trivalent titanium in the slurry from beginning to end. Because the oxidation potential of trivalent titanium is larger than that of ferrous iron, that is, trivalent titanium is more oxidized than ferrous iron, and the presence of trivalent titanium indicates that trivalent iron is not contained in the slurry.
Trivalent titanium is not detected in the slurry, indicating that the ferric iron has not been completely reduced to divalent iron. If the slurry is calcined, the finished product will have a yellow phase due to the inclusion of Fe 2 0 3 ; If the trivalent titanium is too low, the trivalent titanium is quickly oxidized by oxygen in the water after bleaching, and then the ferrous iron is oxidized to ferric iron, and the ferric iron is easily hydrolyzed to form hydroxide. Iron is difficult to remove, causing the yellow phase of the finished product when the satin is burned; if the trivalent titanium of the slurry is too high, the washing is easy to wash off the trivalent titanium to reduce the recovery rate. If the trivalent titanium is still satin-burned after bleaching, and the satin is not fully oxidized to tetravalent titanium, the finished product will be gray phase due to the inclusion of Ti 2 0 3 . [next]
The reason for not measuring trivalent titanium is as follows: 1 the amount of reducing agent added is insufficient; 2 the amount of iron in the metatitanic acid is high, and the added trivalent titanium is not enough to reduce all the ferric iron into divalent iron; The quality of the reducing agent is poor, the heating temperature is too high, and passivation occurs; 4 the bleaching temperature is low, the acidity is improperly controlled or the stirring speed is too fast, and the trivalent titanium in the slurry is reoxidized. The remedy is to replenish the reducing agent so that the trivalent titanium in the slurry is maintained between 0.3-0.5 g/L. And improve the operating conditions, properly extend the holding time, so that the reduction is complete; the reason for the low trivalent titanium content is mainly because the amount of reducing agent added is insufficient, and the reducing agent should be added. The reason why the trivalent titanium is too high is as follows: 1 the reducing agent is added too much; 2 the stirring is uneven, and some of the metatitanic acid has not infiltrated the reducing agent. The remedy is as follows: 1 accurately calculate the amount of reducing agent to be added; 2 prolong the stirring time, so that the reducing agent evenly infiltrates into the slurry.
13. The reduced metatitanic acid should be washed with deionized water.
Because ordinary tap water also contains a small amount of iron and other impurities. If it is washed with ordinary tap water, it will re-contaminate with metatitanic acid and will not achieve the purpose of bleaching. Therefore, the reduced metatitanic acid cannot be washed with ordinary tap water, but washed with deionized water.