CN113582228B

CN113582228B - Preparation method and application of high-whiteness titanium dioxide

Info

Publication number: CN113582228B
Application number: CN202110929298.4A
Authority: CN
Inventors: 何明川; 黄建文; 赵平; 陈湘涛; 李缉勇
Original assignee: Guangdong Hui Yun Titanium Industry Corp ltd
Current assignee: Guangdong Hui Yun Titanium Industry Corp ltd
Priority date: 2021-08-13
Filing date: 2021-08-13
Publication date: 2022-06-03
Anticipated expiration: 2041-08-13
Also published as: CN113582228A

Abstract

The invention provides a preparation method and application of high-whiteness titanium dioxide, and relates to the field of titanium dioxide preparation, wherein the calcination stage in the preparation method comprises the following steps: (1) conveying the filter-pressed metatitanic acid into a first-section dehydration zone through a feed inlet for dehydration, controlling the temperature of the dehydration zone to be T1, and dehydrating until the water content of the metatitanic acid is below 3%; (2) transferring the dehydrated metatitanic acid into a secondary desulfurization zone for desulfurization, controlling the temperature of the desulfurization zone to be T2, and dehydrating until the sulfur content of the metatitanic acid is below 2%; (3) transferring the desulfurized metatitanic acid into a three-section crystal form conversion zone and a particle growth zone, controlling the multi-stage program temperature control of the crystal form conversion zone and the particle growth zone, and finally obtaining a kiln falling product, grinding the kiln falling product, and uniformly mixing powder to obtain the titanium dioxide. The titanium dioxide prepared by the method has higher whiteness and covering power, and can be used in the fields of paint, printing ink, plastics and the like.

Description

Preparation method and application of high-whiteness titanium dioxide

Technical Field

The invention relates to the field of titanium dioxide preparation, and particularly relates to a preparation method and application of high-whiteness titanium dioxide.

Background

Titanium dioxide is a white inorganic pigment, has stable chemical properties, is considered to be the white pigment with the best performance in the world at present, has the advantages of high hardness, good thermal stability, extremely high opacity, high refractive index, strong decoloring force, large covering power and the like, and is widely applied to the industries of coating, plastics, papermaking and the like. The whiteness is one of the most important characteristics of the titanium dioxide, and integrates two optical effects of hue and brightness. Titanium dioxide can reflect light waves with all wavelengths in various visible lights to the same extent, so that the titanium dioxide is white. The whiteness of the titanium dioxide has great influence on the application range of the titanium dioxide, for example, in the industries of coating, papermaking, printing ink and the like, the requirement on color is extremely strict, and if the whiteness of the titanium dioxide is low, the application range of the titanium dioxide can be greatly reduced, and the value of the titanium dioxide is reduced.

Researches show that the calcination process has influence on the whiteness of the titanium dioxide, and the calcination process is generally divided into four stages according to the physicochemical change of the titanium dioxide: the method comprises a dehydration zone, a desulfurization zone, a crystal form transformation zone and a particle growth zone, wherein the influence of the calcination process on the particle size distribution of the titanium dioxide mainly occurs in the crystal form transformation zone and the particle growth zone. The dehydrated and desulfurized titanium dioxide has very fine particle size, still belongs to amorphous titanium dioxide, and needs to be converted into a fixed crystal form in a high-temperature area. When the temperature is raised to a certain extent, anatase crystals are formed and the particles start to grow significantly until particles around 200-400nm are formed. With the increase of the temperature, the particle size of the titanium dioxide particles is gradually increased, however, the particles which grow up are further increased by the long-time calcination at the high temperature, and the hue of the titanium dioxide is deteriorated. In the calcining process, the calcining temperature, the rotating speed of the rotary kiln, the feeding quantity, the thickness of a material layer, the water content of the material and the like have great influence on the transformation of crystal forms and the growth of crystal grains, and the whiteness of the finished titanium dioxide powder can be directly influenced. The material is heated evenly and stably in the calcining process, the particle size of the titanium dioxide particles is controlled within a certain range, and the particle size distribution band is narrow. In practical operation, the following points are mainly required to be controlled: (1) the calcining temperature is formed by controlling the temperature of each part of the rotary kiln in the axial direction, and a specific stable temperature gradient is formed and is mainly realized by adjusting the air quantity, the natural gas quantity and the negative pressure in the kiln; (2) the calcination time can be realized by controlling the optimal residence time of the materials in the kiln and adjusting the rotating speed of the rotary kiln. In addition, when titanium dioxide is calcined at high temperature, impurity elements such as iron, chromium, nickel, copper and the like in titanium dioxide generally exist in an oxide state, and various hues also appear, so that the whiteness of the titanium dioxide is influenced.

However, the research on the calcination temperature gradient and the like is not many at present, and the research on the influence of the calcination temperature on the quality of titanium dioxide is recorded in "nature science" of plastic chemical company of jinling, tokyo, south kyo, first volume in 2017, first volume "of the research: in the document, through experiments on the change of the calcination temperature in the production process of the sulfuric acid process rutile type titanium dioxide, five different temperature values of 880 ℃, 900 ℃, 920 ℃, 940 ℃ and 960 ℃ are selected, and the influence of the rutile content, the whiteness and the achromatism in product indexes under various temperature conditions under the condition that other indexes are not changed is researched. The experimental results show that: the rutile content in the finished product increases with the increase of the calcination temperature; the whiteness of the dry powder of the product is reduced along with the rise of the temperature, and the reduction speed is higher when the temperature is higher; the decoloring power of the product increases and then decreases with increasing temperature. When the temperature is 920 ℃, the comprehensive quality indexes of the product are the best. However, the temperature disclosed in this document is the kiln head temperature, and the temperatures at other stages and the rotation speed of the rotary kiln are not studied.

Chinese patent application 201510010457.5 discloses a calcination method for preparing rutile titanium dioxide, which can reduce the energy consumption in the production process of rutile titanium dioxide. In the method, the calcining temperature and the heat preservation time in the calcining process are determined by the following modes: determining the theoretical transformation temperature range and the heat preservation time range of the production raw materials; determining specific calcining temperature and heat preservation time to calcine the sample of the production raw material, and readjusting the calcining temperature and the heat preservation time to calcine the sample of the production raw material if the conversion rate does not meet the requirements of the production process; until the conversion rate meets the requirements of the production process; on the basis of the calcination temperature T and the heat preservation time T, calcination is carried out at the calcination temperatures of T +10, T +20 and T +30 (DEG C) for the heat preservation times of T-30, T-20, T +10, T +20 and T +30(min), and the optimal calcination temperature and heat preservation time are obtained through detection. The method reduces energy consumption and production cost. However, the application focuses on the degree of correlation between the conversion rate of raw materials, the calcination temperature and the holding time, and does not focus on the influence of correlation between other conditions such as parameters of rotary kiln rotation speed, whiteness and the like.

Aiming at the problems in the prior art, a preparation method and application of high-whiteness titanium dioxide with more comprehensive investigation indexes and better performance are urgently needed to be found.

Disclosure of Invention

The invention provides a preparation method and application of high-whiteness titanium dioxide aiming at the problems in the prior art, and the titanium dioxide prepared by the optimized preparation method has excellent performance and can be applied to the fields of coatings, plastics and the like.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows:

the invention provides a preparation method of titanium dioxide, which comprises the following steps in a calcination stage:

(1) conveying the filter-pressed metatitanic acid into a first-stage dehydration zone through a rotary kiln feed inlet for dehydration, controlling the temperature of the dehydration zone to be T1, and dehydrating until the water content of the metatitanic acid is below 3% (mass fraction);

(2) transferring the dehydrated metatitanic acid into a two-stage desulfurization area of a rotary kiln for desulfurization, controlling the temperature of the desulfurization area to be T2, and dehydrating until the sulfur content of the metatitanic acid is below 2% (mass fraction);

(3) transferring the desulfurized metatitanic acid into a three-section crystal form conversion zone and a particle growth zone, controlling the multi-stage program temperature control of the crystal form conversion zone and the particle growth zone, and finally obtaining a kiln falling product, grinding the kiln falling product, and uniformly mixing powder to obtain the titanium dioxide.

Further, the rotary speed of the rotary kiln during the steps (1) to (2) is 4 to 8 min/rotation, preferably 6 min/rotation, and the value is determined according to the condition of the rotary kiln.

Further, the temperature T1 in the step (1) is 200-400 ℃, preferably 300 ℃.

Further, the temperature T2 in the step (2) is 600-800 ℃, preferably 700 ℃.

Further, the multi-stage program temperature control in step (3) specifically includes: the multi-stage program temperature control in the step (3) specifically comprises: the temperature is controlled to T3 in the range of 850-.

Further, the T3 is preferably 850 ℃, the T4 is preferably 920 ℃, and the T5 is preferably 970 ℃.

Further, the rotation speed in the first stage is n1, the rotation speed in the second stage is n2, and the rotation speed in the third stage is n 3.

Furthermore, the heat preservation time of the first stage is t1, the heat preservation time of the second stage is t2, and the heat preservation time of the third stage is t 3. The range value of t1 is 50-100min, preferably 80min, the range value of t2 is 100-150min, preferably 120min, and the range value of t3 is 15-20min, preferably 18 min.

Further, if T3-T2 is more than or equal to 0 and less than or equal to 100 ℃, then the temperature is controlled

If T3-T2 > 100 ℃, then the

The above-mentioned

N3 is 4-8 min/r; wherein L is the horizontal distance between the position of the metatitanic acid in the rotary kiln and the feeding port (L only considers the distance between the metatitanic acid and the feeding port and does not consider the spreading distance of the metatitanic acid), and D is the inner diameter of the rotary kiln. n1 and n2 are calculated to retain only integer bits.

The titanium dioxide prepared by the preparation method can be applied to the fields of paint, printing ink, plastics or papermaking.

The technical effects obtained by the invention are as follows:

(1) in the implementation process, the calcination temperatures corresponding to different calcination stages of the titanium dioxide are found to have certain influence on the particle size distribution of the obtained titanium dioxide and the condition of forming species of related impurities in the titanium dioxide, such as iron species and the like, so that the performance of the titanium dioxide is greatly influenced, therefore, the invention can better promote the conversion and growth of crystal forms by controlling the calcination temperatures of different stages and according to the temperature and the specific rotating speed of a rotary kiln, and reduce the influence of the species formed by the impurities on whiteness in the process to the greatest extent, so that related parameters can be designed according to the actual condition of the rotary kiln during industrial production to prepare the high-whiteness rutile type titanium dioxide;

(2) according to the invention, the energy can be better saved by adopting a sectional calcination mode, the temperature and the rotating speed of each stage are coordinated, the useless work in the calcination process is reduced, the calcination can be more efficiently completed, the calcination can be completed in a shorter time, and the performance of a titanium dioxide product is obviously improved;

(3) the titanium dioxide obtained by the invention has good formation condition and particle size distribution condition of impurity oxides, the particle size of titanium dioxide particles can be controlled to be about 300mn, the whiteness of the finally obtained titanium dioxide is more than or equal to 99.50%, the rutile conversion rate is between 98.5 and 99.5 percent, and the oil absorption value is less than or equal to 18g/100g, and the prepared titanium dioxide has excellent performance (such as high covering power) and can be applied to the fields of coatings, plastics and the like.

Detailed Description

It should be noted that the raw materials used in the present invention are all common commercial products, and thus the sources thereof are not particularly limited.

Example 1

The preparation method of the titanium dioxide comprises the following steps in a calcination stage:

(1) conveying the filter-pressed metatitanic acid into a first-stage dehydration zone through a feed inlet for dehydration, controlling the temperature of the dehydration zone to be T1, and dehydrating until the water content of the metatitanic acid is below 3% (mass fraction);

(2) transferring the dehydrated metatitanic acid into a second-stage desulfurization zone for desulfurization, controlling the temperature of the desulfurization zone to be T2, and dehydrating until the sulfur content of the metatitanic acid is below 2% (mass fraction);

The rotary speed of the rotary kiln in the processes of the steps (1) to (2) is 4 min/revolution.

The temperature T1 in the step (1) is 200 ℃, the temperature T2 in the step (2) is 600 ℃, and the multi-stage program temperature control in the step (3) specifically comprises the following steps: the temperature is controlled to T3 in the first stage, 850 ℃ in T3, the temperature is kept, the temperature is controlled to T4 in the second stage, 900 ℃ in T4, the temperature is kept, and the temperature is controlled to T5 in the third stage, 950 ℃ in T5. The heat preservation time of the first stage is t1, the heat preservation time of the second stage is t2, and the heat preservation time of the third stage is t3, specifically, t1 is 50min, t2 is 100min, and t3 is 15 min.

Wherein if T3-T2 is more than or equal to 0 and less than or equal to 100 ℃, the temperature is

If T3-T2 is more than 100 ℃, then

N3 is 4 min/r; wherein L is the horizontal distance between the position of the metatitanic acid in the rotary kiln and the feeding port, and D is the inner diameter of the rotary kiln. That is, L is 40m, D is 3m, n1 is 7 min/rev, and n2 is 4 min/rev.

Example 2

(3) transferring the desulfurized metatitanic acid into a three-section crystal form conversion area and a particle growth area, controlling the multi-stage program temperature control of the crystal form conversion area and the particle growth area, and finally obtaining a kiln falling product, grinding the kiln falling product, and uniformly mixing powder to obtain the titanium dioxide.

The rotary speed of the rotary kiln in the processes of the steps (1) to (2) is 8 min/revolution.

The temperature T1 in the step (1) is 400 ℃, the temperature T2 in the step (2) is 800 ℃, and the multi-stage program temperature control in the step (3) specifically comprises the following steps: the temperature is controlled to T3 in the first stage, 880 ℃ at T3, the temperature is maintained, the temperature is controlled to T4 in the second stage, 930 ℃ at T4, the temperature is maintained, and the temperature is controlled to T5 in the third stage, 1000 ℃ at T5. The heat preservation time of the first stage is t1, the heat preservation time of the second stage is t2, and the heat preservation time of the third stage is t3, specifically, t1 is 100min, t2 is 150min, and t3 is 20 min.

Wherein, if the value is more than or equal to 0 and less than or equal to T3-T2 and less than or equal to 100At a temperature of

If T3-T2 is more than 100 ℃, then

N3 is 4 min/r; wherein L is the horizontal distance between the position of the metatitanic acid in the rotary kiln and the feeding port, and D is the inner diameter of the rotary kiln. That is, L is 40m, D is 3m, n1 is 2 min/rev, and n2 is 3 min/rev.

Example 3

The rotary speed of the rotary kiln in the processes of the steps (1) to (2) is 6 min/revolution.

The temperature T1 in the step (1) is 300 ℃, the temperature T2 in the step (2) is 700 ℃, and the multi-stage program temperature control in the step (3) specifically comprises the following steps: the temperature is controlled to T3 in the range of 850 ℃ in the first stage, the temperature is kept, the temperature is controlled to T4 in the second stage and is kept at T4 of 920 ℃, and the temperature is controlled to T5 in the third stage and is kept at T5 of 970 ℃. The heat preservation time of the first stage is t1, the heat preservation time of the second stage is t2, and the heat preservation time of the third stage is t3, specifically, t1 is 80min, t2 is 120min, and t3 is 18 min.

If T3-T2 is more than 100 ℃, then

N3 is 4 min/r; wherein L is the horizontal distance between the position of the metatitanic acid in the rotary kiln and the feeding port, and D is the inner diameter of the rotary kiln. That is, L is 40m, D is 3m, n1 is 3 min/rev, and n2 is 5 min/rev.

Comparative example 1

The only difference from example 3 is that n1 and n2 are not calculated according to the formula of the present invention, but are both limited to 6 min/revolution.

Comparative example 2

The only difference from example 3 is that the temperature T3 was 800 ℃, the temperature T4 was 950 ℃, the temperature T5 was 1000 ℃, the holding time T1 was 40min, T2 was 165min, and T3 was 13min (in this case, n1 was 3 min/rev, and n2 was 8 min/rev).

Comparative example 3

The only difference from example 3 is that the temperature in step (3) is not controlled by multi-stage program, and is directly controlled to 970 ℃, and the holding time is 218 min.

Titanium dioxide performance study in the invention

The test method comprises the following steps:

sample preparation: titanium dioxide in examples 1-3 and comparative examples 1-3.

Test 1:

whiteness: preheating a whiteness meter for 30min, adjusting the whiteness meter to a working state, placing a titanium dioxide sample in a powder device, covering the powder device by using a clean glass plate, compacting the sample, rotating, removing the glass plate to ensure that the surface of the sample is smooth and has no flaws or spots, and placing the sample in the whiteness meter to measure whiteness.

Test 2:

oil absorption value: respectively weighing 5g of titanium dioxide in each example, placing the titanium dioxide on a clean glass plate, dropwise adding dioctyl phthalate with known weight on the glass plate, submitting for one time and grinding for one time, observing that a sample is changed into an agglomeration state from dispersion until the titanium dioxide is completely wetted and becomes an integral mass, weighing the weight of the dioctyl phthalate, and calculating an oil absorption value according to the following formula:

wherein P is the oil absorption value, M1 is the total weight of the dropping bottle and the dioctyl phthalate before dropping, M2 is the total weight of the dropping bottle and the dioctyl phthalate after dropping, and M is the weight of the titanium dioxide sample.

Test 3:

covering power: weighing the total weight of a cup filled with a sample and a soft brush, coating the titanium dioxide sample on a black and white grid clean ground glass plate (required to meet the regulation of GB/T1726 plus 1979), wherein the method is fast and uniform during coating, drying the coated glass plate in an electric heating blast box for 30min, placing the dried glass plate in a dark box, forming an inclination angle of 30-45 degrees between the ground glass plate and the horizontal plane, observing under a 15W fluorescent lamp, and calculating according to the following formula on the basis that the coating completely covers the black and white grid:

wherein X is the covering power, m1 is the total weight of the sample cup and the soft brush before being brushed, m2 is the total weight of the sample cup and the soft brush after being brushed, and S is the area of the black and white glass plate brushed with the titanium dioxide, and the unit is cm²。

TABLE 1

Examples of the invention	Whiteness (%)	Oil absorption number (g/100g)	Hiding power (g/m)²)
				Example 1	99.50	17.53	22.3
Example 2	99.65	17.05	21.5
				Example 3	99.78	16.64	20.2
Comparative example 1	97.22	17.65	23.0
				Comparative example 2	96.84	18.03	23.9
Comparative example 3	94.79	18.74	24.7

As can be seen from Table 1, the whiteness of the rutile titanium dioxide in each example of the invention is more than 99.50%, and the rutile titanium dioxide has high whiteness and excellent oil absorption value and covering power. In comparison, in each comparative example, parameters such as whiteness and the like of the titanium dioxide are reduced, for example, in comparative example 1, when the rotary kiln rotation speed does not follow a specific formula in the invention, the whiteness and the covering power are obviously changed, in comparative example 2, when the temperature and the heat preservation time are changed, performance indexes are correspondingly reduced, so that the temperature, the heat preservation time, the rotary kiln rotation speed and the like can greatly influence the distribution particle size of the titanium dioxide and the formation and distribution conditions of related impurities, and the titanium dioxide with high whiteness, covering power and low oil absorption can be obtained only under the specific temperature and rotation speed change rule conditions. And finally, in the comparative example 3, when the multi-stage program temperature control is not carried out, the overall performance of the finally prepared titanium dioxide is suddenly reduced, so that the key effect of the multi-stage temperature control process in the titanium dioxide production process can be seen.

Finally, it should be noted that the above-mentioned contents are only used for illustrating the technical solutions of the present invention, and not for limiting the protection scope of the present invention, and that the simple modifications or equivalent substitutions of the technical solutions of the present invention by those of ordinary skill in the art can be made without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A preparation method of titanium dioxide is characterized by comprising the following steps: the calcination phase comprises the following steps:

(1) conveying the filter-pressed metatitanic acid into a first-section dehydration zone through a rotary kiln feed inlet for dehydration, controlling the temperature of the dehydration zone to be T1, and dehydrating until the water content of the metatitanic acid is below 3%;

(2) transferring the dehydrated metatitanic acid into a two-stage desulfurization area of a rotary kiln for desulfurization, controlling the temperature of the desulfurization area to be T2, and dehydrating until the sulfur content of the metatitanic acid is below 2%;

(3) transferring the desulfurized metatitanic acid into three sections of crystal form transformation areas and particle growth areas, controlling the multi-stage program temperature control of the crystal form transformation areas and the particle growth areas, and finally obtaining a kiln falling product, grinding the kiln falling product, and uniformly mixing powder to obtain titanium dioxide; the multi-stage program temperature control in the step (3) specifically comprises: the temperature is controlled to T3 in the range of 850-;

the rotating speed of the first stage is n1, the rotating speed of the second stage is n2, and the rotating speed of the third stage is n 3;

the heat preservation time of the first stage is t1, the heat preservation time of the second stage is t2, and the heat preservation time of the third stage is t 3; the range value of t1 is 50-100min, the range value of t2 is 100-150min, and the range value of t3 is 15-20 min;

if T3-T2 is more than or equal to 0 and less than or equal to 100 ℃, then

If T3-T2 > 100 ℃, then the

The above-mentioned

N3 is 4-8 min/r; wherein L is the horizontal distance between the position of the metatitanic acid in the rotary kiln and the feeding port, and D is the inner diameter of the rotary kiln.

2. The method of claim 1, wherein: the temperature T1 in the step (1) is 200-400 ℃.

3. The method of claim 1, wherein: the temperature T2 in the step (2) is 600-800 ℃.

4. The production method according to claim 1, characterized in that: the rotary speed of the rotary kiln in the processes of the steps (1) to (2) is 4-8 min/revolution.

5. Use of titanium dioxide prepared by the process according to any one of claims 1 to 4 for the preparation of coatings, inks, plastics or paper.