Method for preparing rutile type titanium dioxide

Abstract

The invention provides a method for preparing rutile type titanium dioxide, which comprises the following steps: S10, adding metatitanic acid and a first rutile type titanium dioxide primary product into water, and pulping to obtain a pulped material; s20, adding a salt treatment agent into the pulped material to obtain mixed slurry; and S30, introducing the mixed slurry into a microwave oven, and calcining to obtain a second rutile type titanium dioxide primary product. The method has the advantages of being simple in technological process, high in technological efficiency, capable of saving energy, environmentally friendly and the like, has the large-scale condition and is clean energy. After future popularization and application, the efficiency of producing titanium dioxide by a sulfuric acid method can be improved, the greenhouse effect is reduced, and the purpose of green production is achieved.

Description

Technical Field

[0001] The invention relates to the field of sulfuric acid process titanium dioxide production, and in particular to a method for preparing rutile titanium dioxide. Background Art

[0002] Titanium products are widely used in various important fields such as aerospace, aviation, vehicle engineering, coatings, inks, biomedical engineering, etc. Titanium dioxide, scientifically known as titanium dioxide, is a white pigment that is mostly used in coatings, plastics, inks and other fields. The current industrial production methods of titanium dioxide are sulfuric acid method and chlorination method. Among them, the sulfuric acid method is the mainstream method for domestic production. Rutile titanium dioxide has a higher refractive index, hardness, dielectric constant, and density, greater hiding power, higher tinting power, and better weather resistance and stability than anatase titanium dioxide. It has become the best pigment in the industrial production process and has greater practical value. Therefore, rutile titanium dioxide accounts for the vast majority of titanium dioxide production in industrial production.

[0003] The sulfuric acid process uses concentrated sulfuric acid to extract titanium resources from titanium concentrate, hydrolyzes it to produce metatitanic acid, and then calcines it to produce rutile titanium dioxide. During the calcination process, metatitanic acid is dehydrated and desulfurized, undergoes a phase change from an amorphous state to anatase, and then anatase to rutile. At the same time, grain growth occurs, so the calcination process becomes one of the key processes that determine product quality.

[0004] The calcination process of the prior art is to add the salt-treated metatitanic acid slurry into a rotary kiln for heating to achieve the effects of desulfurization and crystal transformation. However, the calcination time of this calcination process is too long, which is prone to overburning or uneven calcination. Usually, the calcination effect can only be adjusted by regulating the flow temperature of the hot gas and the salt treatment ratio. The difficulty is that the heat flow process requires precision, and changing the salt treatment ratio alone cannot effectively control the calcination process.

[0005] Therefore, there is still much room for improvement in the existing industrial titanate calcination crystal transformation technology. Summary of the invention

[0006] In view of the shortcomings of the prior art, the object of the present invention is to provide a method for preparing rutile titanium dioxide.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions: The present invention provides a method for preparing rutile titanium dioxide, which comprises the following steps: S10, adding metatitanic acid and the first rutile titanium dioxide primary product into water for slurrying to obtain a slurry material; S20, adding a salt treatment agent to the pulping material to obtain a mixed pulp; S30, passing the mixed slurry into a microwave oven for calcination to obtain a second rutile titanium dioxide primary product.

[0008] In one embodiment, in step S10, the amount of the first rutile titanium dioxide product added is 5% to 20% of the total mass percentage.

[0009] In one embodiment, in step S10, the particle size of the first rutile titanium dioxide product is 150 nm to 220 nm.

[0010] In one embodiment, in step S10, the concentration of the slurried material is 150 g / L to 500 g / L.

[0011] In one embodiment, in step S20, the salt treatment agent is KOH or K2CO3.

[0012] In one embodiment, the amount of the salt treatment agent added is 0.1% to 2%.

[0013] In one embodiment, in step S30, the process of subjecting the mixed slurry to microwave calcination includes: Rapid heating stage: heating the mixed slurry to 600°C to 800°C at a heating rate of 20°C / min to 100°C / min; and Slow heating and insulation stage: heat the mixed slurry to 850℃~1000℃ at a heating rate of 5℃ / min~10℃ / min, and keep it warm for 0.5h~5h.

[0014] In one embodiment, during the rapid temperature rise period, calcination is performed by introducing the mixed slurry into the microwave oven while turning on the microwave oven to heat the mixture.

[0015] In one embodiment, when the amount of the mixed slurry introduced into the microwave oven reaches 60% to 90% of the volume of the oven body of the microwave oven, the introduction of the mixed slurry is stopped.

[0016] In one embodiment, in step S30, the mixed slurry is introduced into a plurality of vertical microwave ovens arranged in parallel for calcination.

[0017] Compared with the prior art, the beneficial technical effects of the present invention are: The present invention makes full use of the strong dielectric property of the primary rutile titanium dioxide product, so that the metatitanic acid calcination process can be completed quickly. After the primary rutile titanium dioxide product is mixed with metatitanic acid, it can also replace the expensive calcination seed. In addition, the selective rapid heating of microwaves is conducive to reducing the phenomenon of local overburning, and is also conducive to the transformation of metatitanic acid into rutile. After adding the salt treatment agent, the rutile is stably formed and not easy to sinter.

[0018] The present invention adopts a process of calcining by using a plurality of vertical microwave ovens arranged in parallel, which can avoid the use of expensive and fragile large-scale microwave shielding materials, and the production parameters and products are more flexible and controllable, which can effectively save the production time of sulfuric acid titanium dioxide, improve production efficiency, save energy and protect the environment, and have low equipment requirements, which is an optimization of the existing process. The method of the present invention obtains a titanium dioxide calcining process with high rutile conversion rate, high qualified rate and better quality.

[0019] The method of the present invention has the advantages of simple process flow, high process efficiency, energy saving and environmental protection, and is suitable for large-scale production and is a clean energy source. After being promoted and applied in the future, it can increase the efficiency of sulfuric acid process for producing titanium dioxide, reduce the greenhouse effect and achieve the purpose of green production. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0021] Figure 1 The schematic flow chart of the method for preparing rutile titanium dioxide of the present invention is shown in FIG. DETAILED DESCRIPTION

[0022] The following is a further detailed description of the embodiments of the present disclosure in conjunction with the accompanying drawings and examples. The detailed description of the following embodiments and the accompanying drawings are used to exemplarily illustrate the principles of the present disclosure, but cannot be used to limit the scope of the present disclosure. The present disclosure can be implemented in many different forms and is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

[0023] The present disclosure provides these embodiments to make the present disclosure thorough and complete, and to fully express the scope of the present disclosure to those skilled in the art. It should be noted that unless otherwise specifically stated, the relative arrangement of the parts and steps, the composition of the materials, the numerical expressions and the numerical values ​​set forth in these embodiments should be interpreted as being merely exemplary, and not as limiting.

[0024] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0025] The terms "including" and "having" and any variations thereof in the specification and claims of the present invention and the above-mentioned drawings are intended to cover non-exclusive inclusions; the terms "first", "second", etc. in the specification and claims of the present disclosure or the above-mentioned drawings are used to distinguish different objects, rather than to describe a specific order. "Multiple" means two or more, unless otherwise clearly and specifically limited.

[0026] like Figure 1 As shown, the present invention provides a method for preparing rutile titanium dioxide, which comprises the following steps: S10, adding metatitanic acid and the first rutile titanium dioxide primary product into water for slurrying to obtain a slurry material.

[0027] S20, adding a salt treatment agent to the pulped material to obtain a mixed pulp.

[0028] S30, passing the mixed slurry into a microwave oven for calcination to obtain a second rutile titanium dioxide primary product.

[0029] It should be understood by those skilled in the art that microwaves have the characteristics of rapid heating, uniform heating, and environmental protection. Under normal circumstances, the ability of metatitanic acid to absorb microwaves and convert them into thermal energy is insufficient, that is, the dielectric properties are poor, and microwaves cannot effectively heat metatitanic acid to its rutile transformation temperature. Compared with metatitanic acid, rutile titanium dioxide has strong dielectric properties and converts microwave energy faster. Therefore, this property can be used to mix a certain proportion of the existing rutile titanium dioxide primary product (i.e., the first rutile titanium dioxide primary product) with metatitanic acid and then perform crystal transformation in a microwave heating furnace, thereby achieving the effect of uniform heating and rapid temperature rise, and improving the production efficiency of the newly produced rutile titanium dioxide primary product (i.e., the second rutile titanium dioxide primary product).

[0030] In one embodiment, in step S10, the first rutile titanium dioxide primary product is a product obtained by a method known in the prior art, and the addition amount of the first rutile titanium dioxide primary product is 5% to 20% of the total mass percentage. In one embodiment, in step S10, the particle size of the first rutile titanium dioxide primary product is 150nm to 220nm. In one embodiment, in step S10, the concentration of the slurry material is 150g / L to 500g / L.

[0031] Since rutile titanium dioxide has strong dielectric properties, adding 5% to 20% of the first rutile titanium dioxide primary product can make the microwave heating process heat up quickly and speed up production efficiency. The present invention controls the particle size of the first rutile titanium dioxide primary product to 150nm to 220nm, so that the first rutile titanium dioxide primary product also plays the role of a seed crystal, and thus, it can replace the use of expensive calcined seeds. Since the particle size of the first rutile titanium dioxide primary product will continue to grow during the insulation period, if the particle size of the first rutile titanium dioxide primary product is too large, the excessively large particles will grow into a particle size that affects the pigment properties of the final product during the insulation period, which is not conducive to obtaining pigment-grade titanium dioxide. In addition, if the particle size of the first rutile titanium dioxide primary product is too small, the excessively small particle size will affect the normal growth of the particles and affect the production time of the final product. Therefore, the particle size of the first rutile titanium dioxide primary product should be controlled within an appropriate range.

[0032] In one embodiment, in step S20, the present invention uses a single salt treatment inhibitor, such as KOH or K2CO3, and the amount of the salt treatment agent added is 0.1% to 2%. Using an excessive amount of salt treatment inhibitor will greatly increase the rutile conversion temperature, which is not conducive to reducing production costs. If the inhibitor is not used, the rutile will be sintered due to the excessively fast heating efficiency. Adding an appropriate amount of salt treatment agent can ensure that the metatitanic acid will not be overburned during strong heating, and sintering will not occur, thereby making the heating simpler and more direct.

[0033] In one embodiment, in step S30, the process of microwave calcining the mixed slurry includes a rapid heating section and a slow heating and insulation section in sequence. During the rapid heating section, the mixed slurry is heated to 600°C to 800°C at a heating rate of 20°C / min to 100°C / min. This stage requires rapid dehydration and desulfurization of the material to reduce the volume and increase the amount of material entering the furnace. During the slow heating and insulation section, the mixed slurry is heated to 850°C to 1000°C at a heating rate of 5°C / min to 10°C / min, and is kept warm for 0.5h to 5h. The rapid heating section can achieve the purpose of dehydration and desulfurization. The rapid heating at this time will not only not affect the pigment performance of the final product, but also effectively save calcination time. The high temperature period is an important period for crystal transformation. Since too fast a temperature rise is not conducive to the complete, orderly and defect-free transformation of the crystal, and is not conducive to the particle morphology forming, the present invention adopts slow temperature rise and heat preservation to achieve the purpose of crystal regulation. The heat preservation process can provide a certain time to facilitate the regulation of rutile particle size. In addition, since the salt treatment inhibitor will increase the rutile crystal transformation temperature, the heat preservation temperature needs to refer to the amount of salt treatment inhibitor added.

[0034] In one embodiment, during the rapid heating period, calcination is performed by introducing the mixed slurry into the microwave oven while turning on the microwave oven to heat the mixture. The method of heating while adding the mixed slurry utilizes the strong dielectric property of water. The microwave allows the mixed slurry to rapidly remove free water within a few seconds, and the volume of the mixed slurry decreases accordingly, and the amount of the mixed slurry fed into the furnace increases accordingly. In one embodiment, when the amount of the mixed slurry introduced into the microwave oven (i.e., the amount of the mixed slurry fed into the furnace) reaches 60% to 90% of the furnace volume of the microwave oven, the introduction of the mixed slurry is stopped. The amount of the mixed slurry fed into the furnace is related to the removal of desulfurization gas and crystal water. If the furnace space of the microwave oven is too small, the system pressure will be too high, and if the space is too large, the production efficiency of the final product will be affected.

[0035] In the prior art, it is usually considered to use a microwave rotary kiln to replace a traditional rotary kiln of the same size for calcination. However, on the one hand, the size of the microwave rotary kiln is large, and the microwave field is affected by the penetration properties of the microwave itself and is difficult to be evenly distributed, and the uniformity of the product obtained by calcining the mixed slurry is poor. On the other hand, there is a technical problem that microwave shielding materials are difficult to be super-large in the large-scale microwave equipment. Based on this, compared with passing the same amount of mixed slurry into one microwave rotary kiln, in step S30 of the present invention, the mixed slurry is passed into a plurality of vertical microwave ovens arranged in parallel for calcination. The same amount of mixed slurry is dispersed into vertical microwave ovens of relatively small size, and the amount of mixed slurry in each vertical microwave oven is relatively reduced. Under the condition of the same amount of charge, the microwave field distribution of each vertical microwave oven is more uniform, and various process parameters are more controllable, so that titanium dioxide primary products under different conditions can be prepared at the same time, making production more flexible and technical reserves more diverse.

[0036] The specific embodiments of the present invention are described in detail below. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0037] Example 1 The metatitanic acid produced by hydrolysis and the first rutile titanium dioxide primary product are added to water for slurrying to obtain a slurry material. The addition amount of the first rutile titanium dioxide primary product is 5%, the particle size is 150 nm, and the concentration of the slurry material is 150 g / L.

[0038] 0.1% KOH salt treating agent was added to the pulped material to obtain a mixed pulp.

[0039] While the mixed slurry is introduced into the microwave oven, the microwave oven is turned on to rapidly heat the mixed slurry at a heating rate of 20°C / min, so that the mixed slurry is rapidly heated to 800°C. During the rapid heating period, the mixed slurry introduced rapidly removes free water, the volume of the mixed slurry decreases, and the amount of the mixed slurry entering the furnace increases relatively. When the amount of the mixed slurry entering the furnace reaches 60% of the furnace volume of the microwave oven, the introduction of the mixed slurry is stopped. Then, the microwave output power is adjusted, and the high-temperature material obtained in the rapid heating section is heated to 850°C at a heating rate of 5°C / min, and kept warm for 5h, after which the second rutile titanium dioxide primary product is obtained, the rutile conversion rate is 98%, the tinting power is 1700, and the qualified rate of the second rutile titanium dioxide primary product is 91.5%.

[0040] Example 2 The metatitanic acid produced by hydrolysis and the first rutile titanium dioxide primary product are added to water for slurrying to obtain a slurry material. The addition amount of the first rutile titanium dioxide primary product is 8%, the particle size is 180 nm, and the concentration of the slurry material is 200 g / L.

[0041] 0.5% KOH salt treating agent was added to the pulped material to obtain a mixed pulp.

[0042] While the mixed slurry is introduced into the microwave oven, the microwave oven is turned on to rapidly heat the mixed slurry at a heating rate of 30°C / min, so that the mixed slurry is rapidly heated to 600°C. During the rapid heating period, the mixed slurry introduced rapidly removes free water, the volume of the mixed slurry decreases, and the amount of the mixed slurry entering the furnace increases relatively. When the amount of the mixed slurry entering the furnace reaches 70% of the furnace volume of the microwave oven, the introduction of the mixed slurry is stopped. Then, the microwave output power is adjusted, and the high-temperature material obtained in the rapid heating section is heated to 850°C at a heating rate of 10°C / min, and kept warm for 3 hours, after which the second rutile titanium dioxide primary product is obtained, the rutile conversion rate is 99.5%, the tinting power is 1710, and the qualified rate of the second rutile titanium dioxide primary product is 92.1%.

[0043] Example 3 The metatitanic acid produced by hydrolysis and the first rutile titanium dioxide primary product are added to water for slurrying to obtain a slurry material. The addition amount of the first rutile titanium dioxide primary product is 20%, the particle size is 200 nm, and the concentration of the slurry material is 400 g / L.

[0044] 0.8% K2CO3 salt treating agent was added to the pulped material to obtain a mixed pulp.

[0045] While the mixed slurry is introduced into the microwave oven, the microwave oven is turned on to rapidly heat the mixed slurry at a heating rate of 60°C / min, so that the mixed slurry is rapidly heated to 700°C. During the rapid heating period, the mixed slurry introduced rapidly removes free water, the volume of the mixed slurry decreases, and the amount of the mixed slurry entering the furnace increases relatively. When the amount of the mixed slurry entering the furnace reaches 80% of the furnace volume of the microwave oven, the introduction of the mixed slurry is stopped. Then, the microwave output power is adjusted, and the high-temperature material obtained in the rapid heating section is heated to 900°C at a heating rate of 5°C / min, and kept warm for 0.5h, after which the second rutile titanium dioxide primary product is obtained, the rutile conversion rate is 99.2%, the tinting power is 1750, and the qualified rate of the second rutile titanium dioxide primary product is 94.2%.

[0046] Example 4 The metatitanic acid produced by hydrolysis and the first rutile titanium dioxide primary product are added to water for slurrying to obtain a slurry material. The addition amount of the first rutile titanium dioxide primary product is 15%, the particle size is 210 nm, and the concentration of the slurry material is 500 g / L.

[0047] 1.2% K2CO3 salt treating agent was added to the pulped material to obtain a mixed pulp.

[0048] While the mixed slurry is introduced into the microwave oven, the microwave oven is turned on to rapidly heat the mixed slurry at a heating rate of 50°C / min, so that the mixed slurry is rapidly heated to 800°C. During the rapid heating period, the mixed slurry introduced rapidly removes free water, the volume of the mixed slurry decreases, and the amount of the mixed slurry entering the furnace increases relatively. When the amount of the mixed slurry entering the furnace reaches 90% of the furnace volume of the microwave oven, the introduction of the mixed slurry is stopped. Then, the microwave output power is adjusted, and the high-temperature material obtained in the rapid heating section is heated to 950°C at a heating rate of 10°C / min, and kept warm for 5 hours, after which the second rutile titanium dioxide primary product is obtained, the rutile conversion rate is 99.2%, the tinting power is 1780, and the qualified rate of the second rutile titanium dioxide primary product is 95.6%.

[0049] Example 5 The metatitanic acid produced by hydrolysis and the first rutile titanium dioxide primary product are added to water for slurrying to obtain a slurry material. The addition amount of the first rutile titanium dioxide primary product is 10%, the particle size is 220 nm, and the concentration of the slurry material is 300 g / L.

[0050] 2% KOH salt treating agent was added to the pulped material to obtain a mixed pulp.

[0051] While the mixed slurry is introduced into the microwave oven, the microwave oven is turned on and the temperature is rapidly increased at a heating rate of 100°C / min, so that the mixed slurry is rapidly heated to 800°C. During the rapid heating period, the mixed slurry introduced rapidly removes free water, the volume of the mixed slurry decreases, and the amount of the mixed slurry entering the furnace increases relatively. When the amount of the mixed slurry entering the furnace reaches 90% of the furnace volume of the microwave oven, the introduction of the mixed slurry is stopped. Then, the microwave output power is adjusted, and the high-temperature material obtained in the rapid heating section is heated to 1000°C at a heating rate of 8°C / min, and kept warm for 3 hours, after which the second rutile titanium dioxide primary product is obtained, the rutile conversion rate is 99.6%, the tinting power is 1740, and the qualified rate of the second rutile titanium dioxide primary product is 95%.

[0052] Comparative Example 1 The metatitanic acid produced by hydrolysis was mixed with 2% KOH salt treatment agent to obtain a mixed slurry. It was directly added to a microwave heating furnace and heated rapidly at a heating rate of 100℃ / min to quickly heat the mixed slurry to 800℃. During the rapid heating period, the mixed slurry introduced rapidly removed free water, the volume of the mixed slurry decreased, and the amount of the mixed slurry entering the furnace increased relatively. When the amount of the mixed slurry entering the furnace reached 90% of the furnace volume of the microwave oven, the introduction of the mixed slurry was stopped. Then, the microwave output power was adjusted, and the high-temperature material obtained in the rapid heating section was heated to 1000℃ at a heating rate of 8℃ / min, and kept warm for 3h, after which the initial rutile titanium dioxide was obtained, with a rutile conversion rate of 95.5%, a tinting power of 1680, and a qualified rate of 80%.

[0053] It should be particularly pointed out that the various components or steps in the above-mentioned embodiments can be cross-linked, replaced, added, or deleted with each other. Therefore, the combinations formed by these reasonable arrangements and combinations should also fall within the scope of protection of the present invention, and the scope of protection of the present invention should not be limited to the embodiments.

[0054] A person skilled in the art should understand that the discussion of any of the above embodiments is only exemplary 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; under the concept of the embodiments of the present invention, the technical features in the above embodiments or different embodiments can also be combined, and there are many other changes in different aspects of the embodiments of the present invention as described above, which are not provided in detail for the sake of simplicity. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the embodiments of the present invention should be included in the protection scope of the embodiments of the present invention.

Claims

1. A method for preparing rutile titanium dioxide, characterized in that: The method comprises the following steps: S10, adding metatitanic acid and the first rutile titanium dioxide primary product into water for slurrying to obtain a slurry material; S20, adding a salt treatment agent to the pulping material to obtain a mixed pulp; S30, passing the mixed slurry into a microwave oven for calcination to obtain a second rutile titanium dioxide primary product.

2. The method for preparing rutile titanium dioxide according to claim 1, characterized in that: In step S10, the amount of the first rutile titanium dioxide product added is 5% to 20% of the total mass percentage.

3. The method for preparing rutile titanium dioxide according to claim 1, characterized in that: In step S10, the particle size of the first rutile titanium dioxide primary product is 150 nm to 220 nm.

4. The method for preparing rutile titanium dioxide according to claim 1, characterized in that: In step S10, the concentration of the pulped material is 150 g / L to 500 g / L.

5. The method for preparing rutile titanium dioxide according to claim 1, characterized in that: In step S20, the salt treatment agent is KOH or K2CO3.

6. The method for preparing rutile titanium dioxide according to claim 5, characterized in that: The amount of salt treatment agent added is 0.1% to 2%.

7. The method for preparing rutile titanium dioxide according to claim 1, characterized in that: In step S30, the process of subjecting the mixed slurry to microwave calcination includes: Rapid heating stage: heating the mixed slurry to 600°C to 800°C at a heating rate of 20°C / min to 100°C / min; and Slow heating and insulation stage: heat the mixed slurry to 850℃~1000℃ at a heating rate of 5℃ / min~10℃ / min, and keep it warm for 0.5h~5h.

8. The method for preparing rutile titanium dioxide according to claim 7, characterized in that: During the rapid heating stage, calcination is carried out by introducing the mixed slurry into the microwave oven while turning on the microwave oven to heat the mixture.

9. The method for preparing rutile titanium dioxide according to claim 8, characterized in that: When the amount of the mixed slurry introduced into the microwave oven reaches 60% to 90% of the volume of the oven body of the microwave oven, the introduction of the mixed slurry is stopped.

10. The method for preparing rutile titanium dioxide according to claim 1, characterized in that: In step S30, the mixed slurry is introduced into a plurality of vertical microwave ovens arranged in parallel for calcination.

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