Method for reducing viscosity of chlorination process titanium dioxide primary product slurry

Abstract

The invention belongs to the field of titanium dioxide production, and particularly relates to a method for reducing chlorination process titanium dioxide primary product slurry viscosity, which comprises the following steps: inputting deionized water into a pulping tank, starting a stirrer and a pH meter, adding a chlorination process titanium dioxide primary product collected by a bag filter, a hydrogen peroxide solution and a sodium hydroxide solution, and controlling the pH value of the slurry to be 6.0-7.0; inputting the salt-containing slurry into a diaphragm filter press for washing and filter pressing to obtain a filter cake; deionized water and the filter cake are input into a dispersion tank, a stirrer and a pH meter are started, and a sodium hydroxide solution is added to adjust the pH value of the slurry to 9.5-10.5; and adding a certain amount of dispersing agent, uniformly stirring, inputting the slurry into a sand mill, sanding and screening to obtain the low-viscosity sanded slurry. According to the method, the viscosity of the chlorination process titanium dioxide primary product slurry can be reduced, the dispersion stability of titanium dioxide particles in the slurry is improved, the surface post-treatment effect is improved, and then the pigment performance and the application performance of the titanium dioxide product are improved.

Description

Technical Field

[0001] The invention belongs to the field of titanium dioxide production, and in particular relates to a method for reducing the viscosity of primary slurry of titanium dioxide produced by a chloride process. Background Art

[0002] Titanium dioxide is commonly known as titanium dioxide. Titanium dioxide has very stable physical and chemical properties, is non-toxic and harmless, and has excellent optical properties such as high refractive index, optimal opacity, optimal whiteness and brightness. It is the best white pigment in the world and is widely used in coatings, plastics, papermaking, inks, electronics and other fields.

[0003] The production process of titanium dioxide mainly includes sulfuric acid method and chlorination method. The chlorination process has developed rapidly in recent years due to its advantages of high product quality, high added value, advanced technology, environmentally friendly production, and continuous production. The chlorination process mainly includes chlorination refining process, oxidation process and surface post-treatment process. The properties of the titanium dioxide primary product produced by the oxidation process directly affect the surface post-treatment effect, and then affect the quality of titanium dioxide products. At present, the oxidation process is to oxidize titanium tetrachloride into titanium dioxide and then cool and separate the gas and solid to obtain the titanium dioxide primary product. Some chlorine gas remains in the titanium dioxide primary product. In the subsequent sand milling and dispersion process, it will enter the titanium dioxide slurry system to form salt substances, resulting in an increase in the viscosity of the slurry, causing some fine particles to re-condense into coarse particles, resulting in uneven coating on the particle surface, and even some particles cannot be coated, which ultimately affects the pigment properties and application performance of the titanium dioxide product.

[0004] Therefore, how to reduce the viscosity of the primary slurry of chloride-process titanium dioxide has become an urgent problem to be solved. Summary of the invention

[0005] In view of this, the object of the present invention is to provide a method for reducing the viscosity of the primary slurry of titanium dioxide produced by the chloride process, which method can reduce the viscosity of the primary slurry of titanium dioxide produced by the chloride process, improve the dispersion stability of titanium dioxide particles in the slurry, make the titanium dioxide film layer after inorganic coating more uniform, and thus improve the pigment performance and application performance of the titanium dioxide product.

[0006] The present invention provides a method for reducing the viscosity of a primary slurry of titanium dioxide produced by a chloride process, comprising the following steps:

[0007] a) introducing deionized water for pulping into a pulping tank, starting an agitator and a pH meter, adding a chloride titanium dioxide primary product collected by a bag filter, a hydrogen peroxide solution and a sodium hydroxide solution with a mass percentage concentration of 10%, and controlling the pH value of the slurry to be 6.0-7.0 to obtain a salt-containing slurry;

[0008] b) inputting the salt-containing slurry into a membrane filter press for washing and filtering to obtain a filter cake;

[0009] c) feeding the deionized water for dispersion and the filter cake into a dispersion tank, starting the agitator and the pH meter, and adding a sodium hydroxide solution with a mass percentage concentration of 10% to adjust the pH value of the slurry to 9.5-10.5;

[0010] d) adding a certain amount of dispersant to the dispersion tank and stirring evenly to obtain a pre-sand-milling slurry; the dispersant is at least one of sodium silicate, sodium hexametaphosphate, sodium polycarboxylate and ammonium polyacrylate, and the amount of the dispersant added is 0.15-0.4% of the mass of the filter cake;

[0011] e) inputting the slurry before sand grinding into a sand mill for sand grinding and dispersion, and then sieving with a vibrating screen to obtain the slurry after sand grinding.

[0012] Preferably, in step a), the mass ratio of the deionized water for pulping to the primary product of chloride titanium dioxide is (1.6-2):1.

[0013] Preferably, in step a), the mass percentage concentration of the hydrogen peroxide solution is 10-30%, and the amount of the hydrogen peroxide solution added is 0.2-0.6% of the initial quality of the chloride process titanium dioxide.

[0014] Preferably, the mass ratio of the washing water used in the membrane filter press in step b) to the primary product of chloride process titanium dioxide in step a) is (10-20):1.

[0015] Preferably, the amount of washing water used for the membrane filter press in step b) is appropriately increased as the sodium chloride content of the salt-containing slurry in step a) increases.

[0016] Preferably, in step b), the sodium chloride mass content of the filter cake does not exceed 0.3%.

[0017] Preferably, in step c), the mass ratio of the deionized water for dispersion to the filter cake is (0.7-1.4):1.

[0018] Preferably, in step d), the pH value of the slurry before sand grinding is controlled at 11.0 to 11.5.

[0019] Preferably, in step e), the rotation speed of the sand milling dispersion is 2600-3000 r / min.

[0020] Compared with the prior art, the method provided by the present invention introduces hydrogen peroxide solution and sodium hydroxide solution into the primary slurry system of titanium dioxide powder produced by the chloride process to convert chlorine into sodium chloride, then washes away the sodium chloride by washing and filtering, and finally disperses the filter cake with low salt content and performs sand milling and screening. This can reduce the viscosity of the primary slurry of titanium dioxide powder produced by the chloride process, improve the dispersion stability of titanium dioxide particles in the slurry, help improve the surface post-treatment effect, and further improve the pigment performance and application performance of the titanium dioxide product. DETAILED DESCRIPTION

[0021] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] The present invention provides a method for reducing the viscosity of a primary slurry of titanium dioxide produced by a chloride process, comprising the following steps:

[0023] a) introducing deionized water for pulping into a pulping tank, starting an agitator and a pH meter, adding a chloride titanium dioxide primary product collected by a bag filter, a hydrogen peroxide solution and a sodium hydroxide solution with a mass percentage concentration of 10%, and controlling the pH value of the slurry to be 6.0-7.0 to obtain a salt-containing slurry;

[0024] b) inputting the salt-containing slurry into a membrane filter press for washing and filtering to obtain a filter cake;

[0025] c) feeding the deionized water for dispersion and the filter cake into a dispersion tank, starting the agitator and the pH meter, and adding a sodium hydroxide solution with a mass percentage concentration of 10% to adjust the pH value of the slurry to 9.5-10.5;

[0026] d) adding a certain amount of dispersant into the dispersion tank and stirring to obtain a slurry before sand grinding;

[0027] e) inputting the slurry before sand grinding into a sand mill for sand grinding and dispersion, and then sieving with a vibrating screen to obtain the slurry after sand grinding.

[0028] In the method provided by the present invention, in step a), the mass ratio of the deionized water for pulping to the primary product of chloride titanium dioxide is preferably (1.6-2):1, specifically 1.6:1, 1.7:1, 1.8:1, 1.9:1 or 2:1.

[0029] In the method provided by the present invention, in step a), the mass percentage concentration of the hydrogen peroxide solution is preferably 10-30%, specifically 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29% or 30%; the amount of the hydrogen peroxide solution added is preferably 0.2-0.6% of the initial mass of the chloride titanium dioxide powder, specifically 0.2%, 0.3%, 0.4%, 0.5% or 0.6%, which can be adjusted according to the mass of the initial mass of the chloride titanium dioxide powder and the mass percentage concentration of the hydrogen peroxide solution.

[0030] In the method provided by the present invention, the mass ratio of the washing water used in the diaphragm filter press in step b) to the primary product of chloride process titanium dioxide in step a) is preferably (10-20):1, specifically 10:1, 11:1, 12:1, 13:1, 14:1, 15:1, 16:1, 17:1, 18:1, 19:1 or 20:1, and can be appropriately increased according to the increase of sodium chloride content in the salt-containing slurry.

[0031] In the method provided by the present invention, in step b), the mass content of sodium chloride in the filter cake is preferably no more than 0.3%.

[0032] In the method provided by the present invention, in step c), the mass ratio of the deionized water for dispersion to the filter cake is preferably (0.7-1.4):1, specifically 0.7:1, 0.8:1, 0.9:1, 1:1, 1.1:1, 1.2:1, 1.3:1 or 1.4:1.

[0033] In the method provided by the present invention, in step d), the dispersant is at least one of sodium silicate, sodium hexametaphosphate, sodium polycarboxylate and ammonium polyacrylate, more specifically sodium silicate and ammonium polyacrylate, or sodium hexametaphosphate and sodium polycarboxylate; the mass ratio of sodium silicate and ammonium polyacrylate is preferably (1-3):1, specifically 2:1; the mass ratio of sodium hexametaphosphate and sodium polycarboxylate is preferably 1:(1-3), specifically 1:2. In the present invention, the amount of the dispersant added is 0.15-0.4% of the mass of the filter cake, specifically 0.15%, 0.18%, 0.2%, 0.23%, 0.25%, 0.28%, 0.3%, 0.33%, 0.35%, 0.38% or 0.4%, which can be selected according to the solid content of the filter cake.

[0034] In the method provided by the present invention, in step d), the pH value of the slurry before sand grinding is preferably controlled at 11.0 to 11.5.

[0035] In the method provided by the present invention, in step e), the rotation speed of the sand milling dispersion is preferably 2600-3000 r / min, specifically 2600 r / min, 2650 r / min, 2700 r / min, 2750 r / min, 2800 r / min, 2850 r / min, 2900 r / min, 2950 r / min or 3000 r / min.

[0036] For the purpose of greater clarity, the invention is described in detail through the following examples.

[0037] Example 1

[0038] 1600g of deionized water was introduced into a pulping tank, and the agitator and pH meter were started. 1000g of primary chloride titanium dioxide collected by a bag filter, 2.0g of a 30% by mass hydrogen peroxide solution, and 12mL of a 10% by mass sodium hydroxide solution were added. The pH value of the slurry was controlled to be 6.0-7.0, and the sodium chloride content of the salt-containing slurry was detected. The salt-containing slurry was introduced into a membrane filter press, washed with 14kg of deionized water, and a filter cake (NaCl content ≤ 0.3wt%) was obtained by filter pressing. 1100g of deionized water was added. and 1500g of filter cake are input into a dispersion tank, the agitator and the pH meter are started, and a 10% by mass sodium hydroxide solution is added to adjust the pH value of the slurry to 9.5-10.5; 2.0g of sodium silicate and 1.0g of ammonium polyacrylate dispersant are added, and the mixture is stirred evenly to obtain a slurry before sand milling, and the pH value of the slurry before sand milling needs to be controlled at 11.0-11.5; the slurry before sand milling is input into a sand mill, the sand milling speed is set to 3000r / min, the sand milling time is set to 30min, and after sand milling, a 500-mesh vibrating screen is used for sieving to obtain a slurry after sand milling.

[0039] Example 2

[0040] 1800g of deionized water was introduced into a pulping tank, and the agitator and pH meter were started. 1000g of primary chloride titanium dioxide collected by a bag filter, 3.0g of a 20% by mass hydrogen peroxide solution, and 11mL of a 10% by mass sodium hydroxide solution were added. The pH value of the slurry was controlled to be 6.0-7.0, and the sodium chloride content of the salt-containing slurry was detected. The salt-containing slurry was introduced into a membrane filter press, washed with 12kg of deionized water, and a filter cake (NaCl content ≤ 0.3wt%) was obtained by filter pressing. 1300g of deionized water was added. and 1500g of filter cake are input into a dispersion tank, the agitator and the pH meter are started, and a 10% by mass sodium hydroxide solution is added to adjust the pH value of the slurry to 9.5-10.5; 1.0g of sodium hexametaphosphate and 2.0g of sodium polycarboxylate dispersant are added, and the mixture is stirred evenly to obtain a slurry before sand milling, and the pH value of the slurry before sand milling needs to be controlled at 11.0-11.5; the slurry before sand milling is input into a sand mill, the sand milling speed is set to 2800r / min, the sand milling time is set to 30min, and after sand milling, a 500-mesh vibrating screen is used for sieving to obtain a slurry after sand milling.

[0041] Example 3

[0042] 2000g of deionized water was introduced into a pulping tank, and the agitator and pH meter were started. 1000g of the primary product of chloride titanium dioxide collected by a bag filter, 6.0g of a 10% by mass hydrogen peroxide solution, and 10mL of a 10% by mass sodium hydroxide solution were added. The pH value of the slurry was controlled to be 6.0-7.0, and the sodium chloride content of the salt-containing slurry was detected. The salt-containing slurry was introduced into a membrane filter press, washed with 10kg of deionized water, and filtered to obtain a filter cake (NaCl content ≤ 0.3wt%). 1500g of the primary product of chloride titanium dioxide collected by a bag filter was added. g deionized water and 1500 g filter cake are input into a dispersion tank, the agitator and the pH meter are started, and a 10% by mass sodium hydroxide solution is added to adjust the pH value of the slurry to 9.5-10.5; 3.0 g sodium silicate dispersant is added, and the mixture is stirred evenly to obtain a slurry before sand milling, and the pH value of the slurry before sand milling needs to be controlled at 11.0-11.5; the slurry before sand milling is input into a sand mill, the sand milling speed is set to 2600 r / min, the sand milling time is set to 30 min, and after sand milling, a 500-mesh vibrating screen is used for sieving to obtain a slurry after sand milling.

[0043] Comparative Example

[0044] 1800g of deionized water was input into a pulping tank, the agitator and the pH meter were started, 1000g of primary chloride titanium dioxide collected by a bag filter was added, and 10% by mass of sodium hydroxide solution was added to adjust the pH value of the slurry to 7.0-8.0 to obtain a salt-containing slurry; 3.0g of sodium silicate dispersant was added and stirred evenly to obtain a slurry before sand milling; the slurry before sand milling was input into a sand mill, the sand milling speed was set to 2800r / min, the sand milling time was set to 30min, and after sand milling, a 500-mesh vibrating screen was used for sieving to obtain a slurry after sand milling.

[0045] Performance Testing

[0046] The viscosity of the salt-containing slurries and the sand-milled slurries prepared in the above Examples 1 to 3 and the comparative example was tested, and the results are shown in Table 1:

[0047] Table 1 Viscosity of salt-containing slurry and slurry after sand grinding

[0048]

[0049] It can be seen from Table 1 that the viscosity of the sand-milled slurry obtained by the method for reducing the viscosity of the primary slurry of chloride-process titanium dioxide provided by the present invention is less than 50 mPa·s, which is better than the comparative example and meets the requirements of the surface post-treatment on the viscosity of the titanium dioxide slurry.

[0050] The method for reducing the viscosity of the primary product slurry of titanium dioxide powder produced by the chloride process of the present invention comprises the following steps: introducing hydrogen peroxide solution and sodium hydroxide solution into the primary product slurry system of titanium dioxide powder produced by the chloride process to convert chlorine into sodium chloride, then washing away the sodium chloride by washing and filtering, and finally dispersing the filter cake with low salt content and performing sand milling and screening. The viscosity of the primary product slurry of titanium dioxide powder produced by the chloride process of the present invention can be reduced, the dispersion stability of titanium dioxide particles in the slurry can be improved, the surface post-treatment effect can be improved, and the pigment performance and application performance of the titanium dioxide product can be improved.

[0051] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for reducing the viscosity of a primary slurry of chloride-process titanium dioxide, characterized in that: The following steps are involved: a) introducing deionized water for pulping into a pulping tank, starting an agitator and a pH meter, adding a chloride titanium dioxide primary product collected by a bag filter, a hydrogen peroxide solution and a sodium hydroxide solution with a mass percentage concentration of 10%, and controlling the pH value of the slurry to be 6.0-7.0 to obtain a salt-containing slurry; b) inputting the salt-containing slurry into a membrane filter press for washing and filtering to obtain a filter cake; c) feeding the deionized water for dispersion and the filter cake into a dispersion tank, starting the agitator and the pH meter, and adding a sodium hydroxide solution with a mass percentage concentration of 10% to adjust the pH value of the slurry to 9.5-10.5; d) adding a certain amount of dispersant to the dispersion tank and stirring evenly to obtain a pre-sand-milling slurry; the dispersant is at least one of sodium silicate, sodium hexametaphosphate, sodium polycarboxylate and ammonium polyacrylate, and the amount of the dispersant added is 0.15-0.4% of the mass of the filter cake; e) inputting the slurry before sand grinding into a sand mill for sand grinding and dispersion, and then sieving with a vibrating screen to obtain the slurry after sand grinding.

2. The method according to claim 1, characterized in that In step a), the mass ratio of the deionized water for pulping to the primary product of chloride titanium dioxide is (1.6-2):

1.

3. The method according to claim 1, characterized in that In step a), the mass percentage concentration of the hydrogen peroxide solution is 10-30%, and the amount of the hydrogen peroxide solution added is 0.2-0.6% of the initial quality of the chloride process titanium dioxide.

4. The method according to claim 1, characterized in that: The mass ratio of the washing water used in the membrane filter press in step b) to the primary product of chloride process titanium dioxide in step a) is (10-20):

1.

5. The method according to claim 1, characterized in that In step b), the sodium chloride mass content of the filter cake does not exceed 0.3%.

6. The method according to claim 1, characterized in that In step c), the mass ratio of the deionized water for dispersion to the filter cake is (0.7-1.4):

1.

7. The method according to claim 1, characterized in that In step d), the pH value of the slurry before sand grinding is controlled at 11.0-11.

5.

8. The method according to claim 1, characterized in that In step e), the rotation speed of the sand milling dispersion is 2600-3000 r / min.

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