Preparation method of double-effect crystal seeds for sulfuric acid process titanium dioxide production

Abstract

The present invention discloses a method for preparing dual-effect seed crystals for sulfuric acid process titanium dioxide production, comprising the following steps: S1, adding a titanium tetrachloride aqueous solution at an alkali-to-titanium ratio of 1.4 to 1.8 to a sodium hydroxide solution having a mass concentration of 5% to 25% under stirring and external cooling conditions to obtain a preliminary neutralized material; S2, heating the preliminary neutralized material to between 65°C and 90°C and maintaining the temperature for 60 to 120 minutes; S3, 5 to 10 minutes before the end of the temperature maintenance in step S2, adding industrial titanium liquid to the preliminary neutralized material under stirring, wherein the amount of TiO2 in the industrial titanium liquid added is 10% to 40% of the amount of TiO2 in the titanium tetrachloride aqueous solution in step S1, and the addition time is 80 to 120 seconds; S4, after adding the industrial titanium liquid, heating the system temperature again to 90 to 98°C and maintaining the temperature for 5 to 10 minutes to complete the seed crystal preparation. The present invention can obtain dual-effect seed crystals with good induction of hydrolysis and rutile conversion effects.

Description

Technical Field

[0001] The invention relates to the technical field of titanium dioxide preparation, and in particular to a method for preparing double-effect crystal seeds for sulfuric acid process titanium dioxide production. Background Art

[0002] There are two common hydrolysis processes used in the sulfuric acid process for titanium dioxide production: an external seed hydrolysis process, in which titanyl sulfate rapidly induces hydrolysis, and an autogenous seed hydrolysis process, in which pre-added titanium liquid reacts with bottom water to generate seeds that induce hydrolysis of the subsequently added titanium liquid. Whether using either the external seed hydrolysis or autogenous seed hydrolysis process, calcined seeds are required before calcination to induce the conversion of titanium dioxide to rutile. The calcined seeds are prepared separately from metatitanic acid through an alkali dissolution, washing, and acid dissolution process. The preparation cost of one ton of calcined seeds (based on TiO2) is approximately 7,000 yuan. The amount of calcined seeds required to produce one ton of rutile titanium dioxide generally ranges from 4% to 6% (based on the mass ratio of TiO2). This translates to a cost of 280 to 420 yuan per ton of rutile titanium dioxide for calcined seeds, a significant disadvantage for the increasingly competitive sulfuric acid process for titanium dioxide production.

[0003] If adding a single seed crystal could both induce the hydrolysis process and produce rutile titanium dioxide during the calcination stage, the production process would undoubtedly be greatly simplified, making the process easier to operate and improving product quality. This type of seed crystal is referred to as a dual-effect seed crystal. Therefore, it is necessary to develop a dual-effect seed crystal with excellent dual-effect induction properties. Summary of the Invention

[0004] The main purpose of the present invention is to provide a method for preparing double-effect crystal seeds for sulfuric acid process titanium dioxide production, so as to solve the problems of complex process and high cost caused by the additional addition of calcined crystal seeds in the prior art.

[0005] According to one aspect of the present invention, a method for preparing double-effect seed crystals for sulfuric acid process titanium dioxide production is provided, comprising the following steps:

[0006] S1, adding a titanium tetrachloride aqueous solution at an alkali-to-titanium ratio of 1.4 to 1.8 to a sodium hydroxide solution having a mass concentration of 5% to 25% under stirring and external cooling to obtain a preliminary neutralized material;

[0007] S2, heating the preliminary neutralized material to between 65 and 90° C. and keeping the temperature therefor for 60 to 120 minutes;

[0008] S3, 5 to 10 minutes before the end of the insulation in step S2, adding industrial titanium liquid to the preliminary neutralized material under stirring, the amount of TiO2 added to the industrial titanium liquid being 10% to 40% of the amount of TiO2 in the titanium tetrachloride aqueous solution in step S1, and the addition time being 80 to 120 seconds;

[0009] S4, after adding the industrial titanium liquid, the system temperature is raised to 90-98°C again and kept warm for 5-10 minutes to complete the seed crystal preparation.

[0010] According to one embodiment of the present invention, in step S1, the concentration of TiO2 in the titanium tetrachloride aqueous solution is 100-300 g / L, and the mass ratio of HCl to TiO2 in the titanium tetrachloride aqueous solution is 1.65-1.825.

[0011] According to one embodiment of the present invention, in step S1, the titanium tetrachloride aqueous solution is required to be clear and transparent, and no white turbidity appears when it is left at room temperature for more than 24 hours.

[0012] According to one embodiment of the present invention, before step S1, the method further comprises preparing an aqueous solution of titanium tetrachloride, wherein the system temperature is maintained below 20°C during the preparation process.

[0013] According to one embodiment of the present invention, in step S1, the addition time of the titanium tetrachloride aqueous solution is 80 to 120 seconds.

[0014] According to one embodiment of the present invention, in step S1, the system is indirectly cooled before and during the addition process to ensure that the system temperature is between 30°C and 40°C after the addition is completed.

[0015] According to one embodiment of the present invention, in step S2, the temperature is increased at a heating rate of 5 to 10°C / min.

[0016] According to one embodiment of the present invention, in step S3, the titanium dioxide concentration of the industrial titanium liquid is 150-250 g / L, the F value is 1.70-2.00, and the iron-titanium ratio is 0.2-0.5.

[0017] According to one embodiment of the present invention, in step S3, the industrial titanium liquid is preheated and reaches the same temperature as the insulation temperature in step S2.

[0018] According to another aspect of the present invention, a method for producing titanium dioxide using a sulfuric acid process is proposed, comprising: adding a double-effect seed crystal prepared according to the preparation method described in any of the above embodiments to an industrial titanium liquid for hydrolysis to obtain metatitanic acid, and calcining the metatitanic acid without adding a calcined seed crystal to obtain rutile titanium dioxide.

[0019] In the preparation method of dual-effect seed crystals for sulfuric acid process titanium dioxide production according to an embodiment of the present invention, hydrated titanium dioxide with uniform particles and appropriate particle size is obtained through step S1, the ability of the seed crystals to induce hydrolysis and induce rutile conversion is balanced through step S2, and the ratio of anatase microcrystals and amorphous hydrated titanium dioxide in the seed crystal system is further adjusted through steps S3 and S4 to ensure that the number and size of the seed crystals inducing hydrolysis are optimal, thereby obtaining dual-effect seed crystals with better effects of inducing hydrolysis and inducing rutile conversion. DETAILED DESCRIPTION

[0020] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the embodiments of the present invention are further described in detail below in conjunction with specific embodiments.

[0021] It should be noted that all expressions using "first" and "second" in the embodiments of the present invention are for distinguishing two non-identical entities with the same name or non-identical parameters. It can be seen that "first" and "second" are only for the convenience of expression and should not be understood as limitations on the embodiments of the present invention. Subsequent embodiments will not explain this one by one.

[0022] The present invention provides a method for preparing double-effect seed crystals for sulfuric acid process titanium dioxide production, comprising the following steps:

[0023] S1, adding a titanium tetrachloride aqueous solution (i.e., a titanium dichloride solution, prepared by adding water to titanium tetrachloride) at an alkali-titanium ratio of 1.4 to 1.8 (in the embodiments of the present invention, the alkali-titanium ratio is the mass ratio of alkali to TiO2) to a sodium hydroxide solution having a mass concentration of 5% to 25% under stirring and external cooling to obtain a preliminary neutralized material;

[0024] S2, heating the preliminary neutralized material to between 65 and 90° C. and keeping the temperature therefor for 60 to 120 minutes;

[0025] S3, 5 to 10 minutes before the end of the insulation in step S2, adding industrial titanium liquid (i.e., industrial titanyl sulfate solution) to the preliminary neutralized material under stirring, wherein the amount of TiO2 added to the industrial titanium liquid is 10% to 40% of the amount of TiO2 in the titanium tetrachloride aqueous solution in step S1, and the addition time is 80 to 120 seconds;

[0026] S4, after adding the industrial titanium liquid, the system temperature is raised to 90-98°C again and kept warm for 5-10 minutes to complete the seed crystal preparation.

[0027] In an embodiment of the present invention, by adding a titanium tetrachloride aqueous solution to a sodium hydroxide solution with a mass concentration of 5% to 25% according to an alkali-titanium ratio of 1.4 to 1.8 in step S1, it is possible to ensure that uniformly hydrated titanium dioxide particles are generated, and by performing external cooling, the growth of the initially generated hydrated titanium dioxide particles can be suppressed. The holding temperature in step S2 can balance the ability of the seed crystals to induce hydrolysis and induce rutile conversion. A holding temperature below 65°C can easily lead to insufficient promotion of rutile conversion by the seed crystals during the calcination process. A holding temperature that is too high, especially above 90°C, will result in a low hydrolysis rate during the induced hydrolysis process and larger metatitanic acid particles generated. The holding time is also set to balance the ability of the seed crystals to induce hydrolysis and induce rutile conversion. By adding industrial titanium liquid in step S3 and heating and holding the temperature again in step S4, the ratio of anatase microcrystals and amorphous hydrated titanium dioxide in the seed crystal system can be further adjusted to ensure that the number and size of the seed crystals that induce hydrolysis are both optimal. Therefore, the above technical solution of the present invention can obtain dual-effect seed crystals with good effects of inducing hydrolysis and inducing rutile conversion.

[0028] In some embodiments, in step S1, the concentration of TiO2 in the titanium tetrachloride aqueous solution is 100-300 g / L, and the mass ratio of HCl to TiO2 in the titanium tetrachloride aqueous solution is 1.65-1.825, thereby ensuring the generation of hydrated titanium dioxide with suitable particles.

[0029] In some embodiments, before step S1, the method further includes preparing an aqueous solution of titanium tetrachloride, wherein the system temperature is maintained below 20°C during the preparation process. In some embodiments, in step S1, the aqueous solution of titanium tetrachloride is required to be clear and transparent, and no white turbidity appears after standing at room temperature for more than 24 hours. 1.65 to 1.825 in step S1 are theoretical values ​​of the HCl / TiO2 mass ratio in titanium tetrachloride. In the actual preparation process of the solution, HCl will volatilize. If the volatilization amount is too much, the obtained solution will be unstable and easily hydrolyzed. The volatilization amount of hydrochloric acid can be reduced by maintaining the system temperature below 20°C during the preparation process. The limitation of the HCl / TiO2 mass ratio, the observation of standing and the requirement of solution clarification in step S1 are all for the purpose of preventing the hydrolysis of the aqueous solution of titanium tetrachloride.

[0030] In some embodiments, in step S1, the addition time of the titanium tetrachloride aqueous solution is 80 to 120 seconds. In some embodiments, in step S1, the system is indirectly cooled before and during the addition process to ensure that the system temperature is between 30°C and 40°C at the end of the addition. By controlling the addition time of the titanium tetrachloride aqueous solution and the system temperature, the particle size of the initially generated hydrated titanium dioxide particles can be ensured to be within an appropriate range. If the temperature is too high, the particles will easily grow, and if the temperature is too low, the energy consumption will be high and subsequent rapid heating will be difficult. In addition, rapid stirring is required during the addition process.

[0031] In some embodiments, in step S2, the temperature is increased at a rate of 5 to 10°C / min. A faster rate of temperature increase in step S2 is preferred to keep the reacted preliminary neutralized material at a higher temperature as much as possible to avoid excessive retention time during the temperature increase process, which may cause particle growth and agglomeration.

[0032] In some embodiments, in step S3, the titanium dioxide concentration of the industrial titanium solution is 150-250 g / L, the F value is 1.70-2.00, and the iron-titanium ratio is 0.2-0.5. In some embodiments, in step S3, the industrial titanium solution is preheated to the same temperature as the holding temperature in step S2. This allows for optimal adjustment of the ratio of anatase microcrystals to amorphous hydrated titanium dioxide in the seed system.

[0033] After the seed crystals are prepared, they can be used in a certain proportion according to the conventional steps of adding seed crystals and hydrolyzing them according to production needs. The amount of seed crystals can be regulated by the mass ratio of 1% to 4% of the industrial titanium liquid used for seed crystal preparation and the titanium dioxide in the industrial titanium liquid used for hydrolysis in step S3. The amount of seed crystals can be adjusted according to the needs for preparing rutile titanium dioxide for special purposes.

[0034] The use of the above-mentioned dual-effect seed crystals can induce hydrolysis so that the hydrolysis rate meets the requirement of greater than or equal to 96%. At the same time, the obtained titanic acid does not need to be added with calcined seed crystals after washing. Rutile titanium dioxide can be obtained at the same temperature or even lower temperature according to the same salt treatment formula.

[0035] The present invention also proposes a method for producing titanium dioxide using a sulfuric acid process, comprising: adding a double-effect seed crystal prepared according to the preparation method described in any of the above embodiments to an industrial titanium liquid for hydrolysis to obtain metatitanic acid, and calcining the metatitanic acid without adding a calcined seed crystal to obtain rutile titanium dioxide.

[0036] The following describes the specific embodiments.

[0037] Example 1

[0038] (1) 500 ml of a titanium tetrachloride aqueous solution having a TiO2 concentration of 120 g / L and a HCl / TiO2 mass ratio of 1.68 was added to a 20% sodium hydroxide solution (435 g) under stirring and external cooling at an alkali-titanium ratio of 1.45. The addition time of the titanium tetrachloride aqueous solution was 118 s, and the temperature at the end of the addition was 34° C. to obtain a preliminary neutralized material.

[0039] (2) The preliminary neutralization material is heated to 65°C at a heating rate of 6°C / min and kept warm for 120 minutes; the industrial titanium liquid with a titanium dioxide concentration of 220 g / L, an F value of 1.85, and an iron-titanium ratio of 0.23 is also heated to 65°C in advance, and the industrial titanium liquid is added to the system when the preliminary neutralization material is kept warm for 112 minutes. The amount added is 15% of the TiO2 amount in the titanium tetrachloride aqueous solution (9 g TiO2, 40.9 ml industrial titanium liquid), and the addition time is 85 seconds.

[0040] (3) After adding the industrial titanium liquid, the system temperature is raised to 90°C again and kept warm for 10 minutes. The seed crystal preparation is completed.

[0041] Then, the amount of seed crystals is added to the hydrolyzed titanium liquid according to the mass ratio of 2% of the industrial titanium liquid used for seed preparation and the titanium dioxide in the industrial titanium liquid used for hydrolysis, and hydrolysis is carried out according to the conventional external seed hydrolysis process to obtain titanic acid, and the hydrolysis rate is detected to be 96.6%; after washing, the titanic acid is treated with zinc salt (the amount added is shown in Table 1, but no calcined seed crystals are added) and calcined. After calcination according to the calcination system shown in Table 2, the rutile conversion rate is detected to be 99.2%; the rutile conversion rate of the sample obtained by conventional external seed hydrolysis of titanic acid and treatment with zinc salt (the amount added is shown in Table 1) (the calcination system is also as shown in Table 2) is 88.9%.

[0042] Example 2

[0043] (1) 300 ml of a titanium tetrachloride aqueous solution having a TiO2 concentration of 200 g / L and a HCl / TiO2 mass ratio of 1.72 was added to a 12% sodium hydroxide solution (800 g) under stirring and external cooling at an alkali-titanium ratio of 1.60. The addition time of the titanium tetrachloride aqueous solution was 97 s, and the temperature at the end of the addition was 39° C. to obtain a preliminary neutralized material.

[0044] (2) The preliminary neutralization material is heated to 90°C at a heating rate of 9°C / min and kept warm for 70 minutes; an industrial titanium liquid with a titanium dioxide concentration of 190 g / L, an F value of 1.85, and an iron-titanium ratio of 0.31 is also heated to 90°C in advance, and the industrial titanium liquid is added to the system when the preliminary neutralization material is kept warm for 65 minutes. The amount added is 30% of the TiO2 amount in the titanium tetrachloride aqueous solution (18 g TiO2, 94.7 ml industrial titanium liquid), and the addition time is 105 seconds.

[0045] (3) After adding the industrial titanium liquid, the system temperature was raised to 98°C again and kept warm for 5 minutes. The seed crystal preparation was completed.

[0046] Then, the amount of seed crystals is added to the hydrolyzed titanium liquid according to the mass ratio of 2% of the industrial titanium liquid used for seed preparation and the titanium dioxide in the industrial titanium liquid used for hydrolysis, and hydrolysis is carried out according to the conventional external seed hydrolysis process to obtain titanic acid, and the detected hydrolysis rate is 98.2%; after washing, the titanic acid is treated with zinc salt (the amount added is shown in Table 1, but no calcined seed crystals are added) and calcined. After calcination according to the calcination system shown in Table 2, the rutile conversion rate is 98.5%; the sample obtained by conventional external seed hydrolysis of titanic acid and calcination of zinc salt (the amount added is shown in Table 1) (the calcination system is also as shown in Table 2) has a rutile conversion rate of 90.1%.

[0047] Example 3

[0048] (1) 200 ml of a titanium tetrachloride aqueous solution having a TiO2 concentration of 300 g / L and a HCl / TiO2 mass ratio of 1.80 was added to an 8% sodium hydroxide solution (1350 g) under stirring and external cooling at an alkali-titanium ratio of 1.80. The addition time of the titanium tetrachloride aqueous solution was 83 s, and the temperature at the end of the addition was 31° C. to obtain a preliminary neutralized material.

[0049] (2) The preliminary neutralization material is heated to 80°C at a heating rate of 8°C / min and kept warm for 100 minutes; an industrial titanium liquid with a titanium dioxide concentration of 160 g / L, an F value of 1.95, and an iron-titanium ratio of 0.50 is also heated to 80°C in advance, and the industrial titanium liquid is added to the system when the preliminary neutralization material is kept warm for 90 minutes. The amount added is 20% of the TiO2 amount in the titanium tetrachloride aqueous solution (12 g TiO2, 75 ml industrial titanium liquid), and the addition time is 96 seconds.

[0050] (3) After adding the industrial titanium liquid, the system temperature was raised to 94°C again and kept warm for 8 minutes. The seed crystal preparation was completed.

[0051] Then, the amount of seed crystals is added to the hydrolyzed titanium liquid according to the mass ratio of 2% of the industrial titanium liquid used for seed preparation and the titanium dioxide in the industrial titanium liquid used for hydrolysis, and hydrolysis is carried out according to the conventional external seed hydrolysis process to obtain titanic acid, and the detected hydrolysis rate is 97.3%; after washing, the titanic acid is treated with zinc salt (the amount added is shown in Table 1, but no calcined seed crystals are added) and calcined. After calcination according to the calcination system shown in Table 2, the rutile conversion rate is 99.5%; the sample obtained by conventional external seed hydrolysis of titanic acid and treatment with zinc salt (the amount added is shown in Table 1) (the calcination system is also as shown in Table 2) has a rutile conversion rate of 93.7%.

[0052] Table 1 Salt treatment system

[0053]

[0054] Table 2 Calcination system

[0055]

[0056] Those skilled in the art should understand that the discussion of any of the above embodiments is merely illustrative and is not intended to imply that the scope of the disclosure of the embodiments of the present invention (including the claims) is limited to these examples. Within the spirit of the embodiments of the present invention, the technical features of the above embodiments or different embodiments may be combined, and there are many other variations of the different aspects of the embodiments of the present invention described above, which are not provided in detail for the sake of clarity. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the embodiments of the present invention should be included within the scope of protection of the embodiments of the present invention.

Claims

1. A method for preparing double-effect seed crystals for sulfuric acid process titanium dioxide production, characterized in that: The following steps are involved: S1, adding a titanium tetrachloride aqueous solution at an alkali-to-titanium ratio of 1.4 to 1.8 to a sodium hydroxide solution having a mass concentration of 5% to 25% under stirring and external cooling to obtain a preliminary neutralized material; S2, heating the preliminary neutralized material to between 65 and 90° C. and keeping the temperature therefor for 60 to 120 minutes; S3, 5 to 10 minutes before the end of the insulation in step S2, adding industrial titanium liquid to the preliminary neutralized material under stirring, the amount of TiO2 added to the industrial titanium liquid is 10% to 40% of the amount of TiO2 in the titanium tetrachloride aqueous solution in step S1, and the addition time is 80 to 120 seconds; S4, after adding the industrial titanium liquid, the system temperature is raised to 90-98°C again and kept at this temperature for 5-10 minutes to complete the seed crystal preparation; In step S1, the concentration of TiO2 in the titanium tetrachloride aqueous solution is 100-300 g / L, and the mass ratio of HCl to TiO2 in the titanium tetrachloride aqueous solution is 1.65-1.

825.

2. The method according to claim 1, characterized in that In step S1, the titanium tetrachloride aqueous solution is required to be clear and transparent, and no white turbidity appears after being left to stand at room temperature for more than 24 hours.

3. The method according to claim 1, characterized in that Before step S1, the method further comprises preparing an aqueous solution of titanium tetrachloride, wherein the system temperature is maintained below 20°C during the preparation process.

4. The method according to claim 1, wherein In step S1, the addition time of the titanium tetrachloride aqueous solution is 80 to 120 seconds.

5. The method according to claim 1, wherein In step S1, the system is indirectly cooled before and during the addition to ensure that the system temperature is between 30°C and 40°C after the addition is completed.

6. The method according to claim 1, wherein In step S2, the temperature is increased at a heating rate of 5 to 10°C / min.

7. The method according to claim 1, characterized in that In step S3, the titanium dioxide concentration of the industrial titanium liquid is 150-250 g / L, the F value is 1.70-2.00, and the iron-titanium ratio is 0.2-0.

5.

8. The method according to claim 1, characterized in that In step S3, the industrial titanium liquid is preheated and reaches the same temperature as the holding temperature in step S2.

9. A method for producing titanium dioxide using a sulfuric acid process, characterized in that: include: The double-effect seed crystals prepared by the preparation method according to any one of claims 1 to 8 are added to industrial titanium liquid for hydrolysis to obtain metatitanic acid, and the metatitanic acid is calcined without adding calcined seed crystals to obtain rutile titanium dioxide.

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