CN111233033A - Process method for regulating particle size of titanium dioxide - Google Patents
Process method for regulating particle size of titanium dioxide Download PDFInfo
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- CN111233033A CN111233033A CN202010223702.1A CN202010223702A CN111233033A CN 111233033 A CN111233033 A CN 111233033A CN 202010223702 A CN202010223702 A CN 202010223702A CN 111233033 A CN111233033 A CN 111233033A
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- C01G23/00—Compounds of titanium
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- C—CHEMISTRY; METALLURGY
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- C01P2004/03—Particle morphology depicted by an image obtained by SEM
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- C—CHEMISTRY; METALLURGY
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- C01P2004/00—Particle morphology
- C01P2004/60—Particles characterised by their size
- C01P2004/62—Submicrometer sized, i.e. from 0.1-1 micrometer
Abstract
The invention relates to a process method for regulating and controlling the particle size of titanium dioxide, which regulates and controls the particle size of the titanium dioxide by changing the calcining temperature rise rate; the method specifically comprises the following steps: in the calcining step for preparing the titanium dioxide, a heating rate control sectional calcining mode is adopted, the calcining process is divided into three temperature sections for sectional calcining, the temperature of the first section is 25-800 ℃, the adopted heating rate is 5-10K/min, and the retention time is 155min-77 min; in the second stage, the temperature is increased at 800-950 ℃ at the heating rate of 0.5-1.5K/min and the retention time is 300-100 min; the third section is 950-1000 ℃, the adopted heating rate is 5-7K/min, and the retention time is 10-7 min. The method can finally regulate and control TiO2Has a particle size in the range of 240nm to 260 nm. The invention adjusts TiO by controlling the temperature rise rate of different stages of calcination so as to change the residence time of particles in different temperature stages2The crystal transformation and the crystal growth rate further achieve the purpose of regulating the particle size of the titanium dioxide, and have guiding significance for the actual industrial production.
Description
Technical Field
The invention belongs to the technical field of titanium dioxide production, and particularly relates to a calcination process method for regulating and controlling the particle size of titanium dioxide.
Background
Titanium dioxide is a high-performance white pigment recognized in the world, has the remarkable advantages of large covering power, high decoloring power, good weather resistance and the like, and has stable physicochemical property and excellent electrooptical performance. The domestic industrial production process of titanium dioxide is mainly sulfuric acid process. In the sulfuric acid process, the calcination process of metatitanic acid is the process of forming titanium dioxide, and the crystal form, the particle size and the distribution of calcined kiln waste directly influence the pigment performance of a titanium dioxide finished product, and are very important titanium dioxide quality evaluation indexes. If the particle size of the kiln waste is too large or sintering occurs, crystal lattices are damaged, which may lead to TiO2The hardness is too high, the pigment performances such as brightness and whiteness are not good enough, the product quality is influenced, the capacity consumption in the post-treatment processes such as subsequent grinding and coating can be increased, and the production cost is increased.
Chinese patent CN110357153A discloses a method for preparing high-purity titanium dioxide by using industrial metatitanic acid hydrothermal method: filtering and drying metatitanic acid slurry subjected to hydrothermal washing, heating the metatitanic acid slurry from room temperature to 840-900 ℃ at the heating rate of 10-15 ℃/min, preserving the heat at 840-900 ℃ for 60-300 min, cooling to room temperature, crushing and grinding to obtain high-purity titanium dioxide with the particle size of 150nm-220nm and the rutile content of more than 99.8 percent, wherein the calcination process of the patent is heating to a specified temperature at a specific rate, and the calcination of the patent is described to be mainly used for removing impurities such as moisture, volatile components, ash, sulfate radicals and the like in a sample.
Chinese patent CN103183379B discloses a method for calcining metatitanic acid by flash drying: drying metatitanic acid by flash evaporation until the moisture content is 10-15%, introducing the metatitanic acid into a rotary kiln, calcining the material in three stages, wherein each stage accounts for one third of the whole length of the rotary kiln, the temperature of the first stage is controlled at 700 ℃ and the retention time is 1.5-2 hours, and the first stage mainly has the function of removing crystal water in metatitanic acid again; the temperature of the second stage is controlled at 700-; the temperature of the third stage is controlled at 850 ℃ and 950 ℃, the retention time is 2-2.5 hours, and the third stage mainly has the functions of crystal form conversion, grain size growth and outflow of the calcined qualified product from the lower end of the rotary kiln to a cooling roller. In the course of the invention of the present application, the inventors of the present application found that the following problems exist in the patent: 1. in the invention creation process of the application, the inventor of the application finds that hydrogen bond water removal and multilayer adsorption water removal of metatitanic acid are carried out simultaneously with desulfurization after removing free water. 3. The temperature of the third stage in the patent is controlled at 850-950 ℃, and the calcination temperature does not consider the difference of the correlation rules of the crystal form conversion rate of the crystal and the crystal growth rate and the temperature, so that the aims of controlling the crystal grain size and obtaining high rutile conversion rate cannot be achieved simultaneously.
Chinese patent CN108408770A discloses a sulfur removal process for metatitanic acid, which describes that the calcination process is: raising the temperature to 780 ℃ in 80min, and keeping the temperature at 780 ℃ for 1 h; raising the temperature to 910 ℃ for 15min, and preserving the heat at 910 ℃. In the course of the invention of the present application, the inventors of the present application found that the following problems exist in the patent: in the patent, the temperature rise rate in the process of rising from 780 ℃ to 910 ℃ is high and is more than 8K/min, and the calcination temperature does not consider the difference of the correlation rule between the crystal form conversion rate of the crystal and the crystal growth rate and the temperature, so that the crystal grows rapidly and TiO exists2From sharpThe time for the conversion of titanium form to rutile form is insufficient.
Chinese patent CN110683577A discloses a method for improving whiteness of titanium dioxide by adjusting particle size, which is to dry a metatitanic acid filter cake obtained by filter pressing in front of a kiln at the temperature of 120-160 ℃ for 4-6h, then heat up to 600 ℃ according to 1h, and then calcine in a muffle furnace according to the temperature curve of heating up to 960 ℃ at 1 ℃/min, wherein the final particle size is within the range of 200-390 nm. The inventors of the present application found that the following problems exist in the patent: the temperature of the patent is too slow when the temperature is directly increased from 600 ℃ to 960 ℃, so that the retention time is prolonged, the grain growth is accelerated, and the difference of the grain size distribution is increased.
The key to the quality of the pigment-grade titanium dioxide product is good crystal form composition and proper particle size distribution. The actual situation is that the crystal form and the granularity of the titanium dioxide are influenced by the difference of primary particles of the hydrolysis material metatitanic acid and the agglomeration condition thereof and the difference of heat and mass transfer rates caused by the difference of residence time at each temperature in the calcining process. Moreover, improper high-temperature calcination time can damage the product quality and also can cause increase of production energy consumption. The particle size and the distribution of the titanium dioxide of different batches have larger fluctuation, and the pigment performance of the product is influenced.
Therefore, the method can adjust and control TiO aiming at the particle size distribution of metatitanic acid particles2Particle size calcination processes are currently highly desirable.
Disclosure of Invention
Aiming at the problem that the particle size of titanium dioxide particles is not well controlled in the calcining process of the titanium dioxide pointed out in the background technology, the invention provides a method for regulating and controlling the particle size of the titanium dioxide.
The purpose of the invention can be realized by the following technical scheme:
the invention provides a process method for regulating and controlling the particle size of titanium dioxide, which regulates and controls the particle size of the titanium dioxide by changing the calcining temperature rise rate; the method specifically comprises the following steps: in the calcining step for preparing the titanium dioxide, a heating rate control sectional calcining mode is adopted, the calcining process is divided into three temperature sections for sectional calcining, the temperature of the first section is 25-800 ℃, the adopted heating rate is 5-10K/min, and the retention time is 155min-77 min; in the second stage, the temperature is increased at 800-950 ℃ at the heating rate of 0.5-1.5K/min and the retention time is 300-100 min; the third section is 950-1000 ℃, the adopted heating rate is 5-7K/min, and the retention time is 10-7 min.
In one embodiment of the invention, the calcination process is carried out in a muffle furnace.
In one embodiment of the present invention, the object of the calcination is dried metatitanic acid.
In one embodiment of the present invention, the particle size range of the metatitanic acid is: 2.0-3.5 μm.
After the calcination, the mixture was cooled at room temperature and then subjected to XRD and SEM detection.
The particle size range of the titanium dioxide particles obtained after calcination is 240nm-260 nm.
Although there is a method of controlling temperature by stages in the calcination process in the prior art mentioned in the background art, the prior art does not know the reaction and crystal transformation mechanism of metatitanic acid in the calcination process, and the temperature program setting either adopts a lower temperature rise rate or a faster temperature rise rate, which is difficult to achieve in controlling TiO2Particle size and crystal form.
According to the research of the invention, the earlier stage of calcining the metatitanic acid is only the dehydration and desulfurization of the metatitanic acid, the conversion rate from amorphous to anatase is very low, and the particle size is almost unchanged, so that the dehydration and desulfurization are found to occur together through theoretical research and experimental demonstration and occur in the earlier stage of calcining, and the calcination is carried out at a higher temperature rise rate from 25-800 ℃, so that the metatitanic acid is dehydrated and desulfurized simultaneously; the invention discovers that dehydration and 700 ℃ occur simultaneously at 300 ℃ to 700 DEG CDesulfurization, in which water is removed in the form of hydrogen-bonded water and multi-layer adsorbed water, and sulfur is removed in the form of Sulfur Oxides (SO)2、SO3) The morphology of (2) is removed.
From 800 ℃ to 950 ℃, anatase TiO2Rutile type TiO2If the supplied heat is too large, the rapid growth of crystals can be promoted besides the transformation of crystal forms, so that the non-uniformity of grain growth is caused; 950 ℃ and 1000 ℃, which is a period of rapid crystal growth, if a slow temperature rise is adopted, the retention time is prolonged, the grain growth is accelerated, the difference of the grain size distribution is increased, and even the sintering phenomenon of particles may occur. Therefore, improper high-temperature calcination time can damage the product quality and also cause increase of production energy consumption.
The invention provides a calcination process of a metatitanic acid raw material with a specific particle size range based on the bulk phase characteristics of the calcined raw material and the associated reaction, phase change and crystal growth rules in the calcination process.
The research of the invention finds that the retention time can influence TiO at the temperature of 800-2Phase transition and crystal growth behavior of the particles. In the front temperature section of the range, under the slow temperature rise rate, the phase change process from anatase to rutile can occur in advance, the particle growth is slow, so that the conversion rate of rutile can be promoted, and TiO can promote the conversion rate of rutile2The particle size is not greatly changed; the opposite is true at fast ramp rates. In the later temperature range and at the slow heating rate, the growth rate of the crystal is accelerated, so that TiO with larger particle size is formed2And (4) crystals. Therefore, the invention divides the calcining process into three temperature sections for sectional calcining, the first section is 25-800 ℃, the adopted heating rate is 5-10K/min, and the retention time is 155-77 min; in the second stage, the temperature is increased at 800-950 ℃ at the heating rate of 0.5-1.5K/min and the retention time is 300-100 min; the third section is 950-1000 ℃, the adopted heating rate is 5-7K/min, and the retention time is 10-7 min.
The titanium dioxide with the particle size range of 240nm-260nm can be finally regulated and controlled by the method for regulating and controlling the calcining temperature. Can achieve the purpose of accurately regulating and controlling TiO2The particle size and the distribution thereof, and the purpose of stabilizing the quality of the product.
Compared with the prior art, the invention has the following advantages and beneficial effects:
the invention controls different heating rates in the calcining stage, thereby changing the retention time to regulate and control the particle size of the titanium dioxide, further achieving the purpose of obtaining titanium dioxide products with different particle size requirements, and having guiding significance for actual industrial production.
Drawings
FIG. 1: TiO at two different heating rates of 0.5K/min and 2K/min2XRD spectrum of (1);
FIG. 2: XRD spectrograms at different final temperatures at a heating rate of 1K/min;
fig. 3 (a): TiO is added with the temperature rise under different heating rates of 0.5, 1, 2, 5 and 10K/min2A particle size diagram;
fig. 3 (b): TiO is added with the temperature rise under different heating rates of 0.5, 1, 2, 5 and 10K/min2A rutile conversion plot;
FIG. 4: SEM electron micrograph.
Detailed Description
The main procedure for preparing titanium dioxide from titanium ore comprises the following steps: crushing titanium ore, acidolysis of titanium ore, settling acidolysis solution, heat filtration, hydrolysis of titanium solution, primary washing, bleaching, secondary washing, salt treatment, drying, calcination, roll milling, ball milling, wet milling, coating, washing, flash drying and gas-powder organic coating. In the following embodiment, the particle size of titanium dioxide is mainly controlled by controlling the calcination stage.
Providing a process method for regulating and controlling the particle size of titanium dioxide, wherein the particle size of the titanium dioxide is regulated and controlled by changing the calcining temperature rise rate; the method specifically comprises the following steps: in the calcining step for preparing the titanium dioxide, a heating rate control sectional calcining mode is adopted, the calcining process is divided into three temperature sections for sectional calcining, the temperature of the first section is 25-800 ℃, the adopted heating rate is 5-10K/min, and the retention time is 155min-77 min; in the second stage, the temperature is increased at 800-950 ℃ at the heating rate of 0.5-1.5K/min and the retention time is 300-100 min; the third section is 950-1000 ℃, the adopted heating rate is 5-7K/min, and the retention time is 10-7 min.
In the process of calcinationIn the process, the metatitanic acid is dehydrated and desulfurized firstly, and then the TiO is added2The crystal form transformation occurs, from amorphous form to anatase form; a phase transition ensues from the anatase to the rutile form with concomitant crystal growth. In the calcining process, different heating rates and residence times under different temperature sections can have important influence on the particle size of the titanium dioxide.
In one embodiment, the calcination process is performed in a muffle furnace.
Cooling at room temperature after calcining, grinding by using a grinding machine, and then carrying out XRD and SEM detection.
The invention is described in detail below with reference to the figures and specific embodiments.
Example 1
1.1, obtaining an experimental raw material metatitanic acid:
taking hydrolyzed slurry in the traditional sulfuric acid method titanium dioxide production process as a raw material, carrying out suction filtration, washing with deionized water at 60 ℃ for one time, and filtering; according to metatitanic acid slurry TiO2Adding deionized water with concentration of 300g/L, pulping, and stirring in a constant temperature water bath at 70 deg.C for 30 min; then adding the following components in turn: adding 98% concentrated sulfuric acid according to the concentration of 100g/L of slurry, and washing industrial Ti with the concentration of 1.3g/L in the slurry3+The Ti content in the solution, the calcined crystal seed and the slurry is TiO24.0 percent of calcined seed crystal is calculated, and the seed crystal needs to be stirred for 30min after each feeding; then, the slurry is filtered, and is subjected to secondary washing by using deionized water at 60 ℃ and is filtered; and (3) putting the filter cake into an oven, and drying for 6h at the temperature of 120 ℃ to obtain an experimental raw material metatitanic acid.
1.2 non-staged calcination of metatitanic acid
And (3) putting a proper amount of dried metatitanic acid sample into a crucible, putting the crucible into a muffle furnace for calcining, and calcining the sample from room temperature to 950 ℃ by respectively adopting the heating rates of 0.5K/min and 2.0K/min. And taking out the calcined product, cooling to room temperature, grinding by using a grinder, and then carrying out SEM and XRD detection.
Referring to FIG. 1, TiO is heated at two heating rates of 0.5K/min and 2K/min2The XRD spectrum (figure 1) shows that under the condition of not adding salt treatment agent and seed crystal, the temperature rise rate is low (0.5K/min)The rutile (110) crystal face characteristic peak intensity in the sample is obviously higher than that of TiO with higher heating rate (2K/min)2The characteristic peak of the rutile (110) crystal face is strong, namely the rutile content of the sample at a low temperature rising rate is higher.
Example 2
2.1, obtaining an experimental raw material metatitanic acid:
taking hydrolyzed slurry in the traditional sulfuric acid method titanium dioxide production process as a raw material, carrying out suction filtration, washing with deionized water at 60 ℃ for one time, and filtering; according to metatitanic acid slurry TiO2Adding deionized water with concentration of 300g/L, pulping, and stirring in a constant temperature water bath at 70 deg.C for 30 min; then adding the following components in turn: adding 98% concentrated sulfuric acid according to the concentration of 100g/L of slurry, and washing industrial Ti with the concentration of 1.3g/L in the slurry3+The Ti content in the solution, the calcined crystal seed and the slurry is TiO24.0 percent of calcined seed crystal is calculated, and the seed crystal needs to be stirred for 30min after each feeding; then, the slurry is filtered, and is subjected to secondary washing by using deionized water at 60 ℃ and is filtered; pulping the second-washing filter cake with deionized water, dispersing, adding TiO2Calculated mass fraction 0.2% of soluble phosphonium salt reagent (in P)2O5Calculated by K) and 0.25 percent of soluble potassium salt (calculated by K)2Calculated as O) and 0.25 percent of soluble aluminum salt reagent (calculated as Al)2O3Metering), stirring for 1h at normal temperature, and filtering; putting the filter cake into a drying oven, and drying for 6 hours at the temperature of 120 ℃; the metatitanic acid used as the experimental material in this example was obtained.
2.2 investigation of different calcination end-point temperatures for TiO2Influence of the phase transformation Process
Taking a proper amount of dried metatitanic acid sample into a crucible, putting the crucible into a muffle furnace for calcining, and respectively heating to 500 ℃, 600 ℃, 700 ℃, 800 ℃, 850 ℃, 900 ℃ and 1000 ℃ from 25 ℃ at a heating rate of 1K/min. And taking out the calcined product, cooling to room temperature, grinding by using a grinder, and then carrying out SEM and XRD detection.
Referring to FIG. 2, the calcination was carried out to three different end-point temperatures TiO of 850 deg.C, 900 deg.C and 1000 deg.C2The XRD spectrum (figure 2) shows that the characteristic peak intensity of the rutile (110) crystal face in the sample is obviously high at 900 ℃ at the temperature rising rate of 1K/minThe peak intensity at 850 ℃ indicates a high rutile conversion for the 900 ℃ sample.
2.3 investigating different heating rates for TiO2Influence of particle size and Crystal form
The experimental steps are as follows: 2.1, obtaining the dried metatitanic acid. Taking a proper amount of dried metatitanic acid sample into a crucible, putting the crucible into a muffle furnace for calcining, raising the temperature of the crucible from 25 ℃ to 1000 ℃ at the heating rates of 0.2K/min, 0.5K/min, 1K/min, 2K/min and 5K/min, taking out the calcined product, cooling to room temperature, grinding by using a grinder, and then carrying out SEM and XRD detection.
Referring to FIG. 3, TiO2 at different heating rates of 0.5K/min, 1K/min, 2K/min, 5K/min, and 10K/min2Particle size (FIG. 3a) and rutile conversion (FIG. 3b) of the samples it can be seen that the dehydration desulfurization step is predominantly carried out before 900 ℃ and the anatase to rutile conversion process is predominantly carried out after 900 ℃. TiO at low ramp rates2The crystal grains complete the phase transformation process earlier, and the crystal grains are aggregated, fused and grown earlier in the phase transformation process, so that the grain size is larger.
Referring to the SEM electron micrograph of FIG. 4 and the particle size plot of FIG. 3a, when the calcination temperature reached above 950 deg.C, the difference between the particle sizes of the samples calcined at the fastest heating rate and the samples calcined at the slowest heating rate reached above 100 nm. The slope of the particle size curve of the particles is gradually reduced along with the reduction of the temperature rise rate in the temperature rise process, so that the temperature rise rate is increased in a high-temperature section, the retention time of a sample is shortened, and the particle size of crystal grains can be effectively reduced.
Example 3
Taking hydrolyzed slurry in the traditional sulfuric acid method titanium dioxide production process as a raw material, carrying out suction filtration on the hydrolyzed slurry, carrying out primary washing by using deionized water at 60 ℃, and cleaning industrial waste acid in the slurry to obtain a metatitanic acid filter cake; after primary washing, the metatitanic acid filter cake is dispersed by deionized pulping, the concentration of metatitanic acid slurry TiO2 is adjusted to be about 300g/L, and the metatitanic acid slurry is placed in a constant temperature water bath at 70 ℃ and stirred for 30 min; then adding 100 g/L98% concentrated sulfuric acid, and stirring for 30 min; taking industrial Ti3+Solution and calcined seed crystal, Ti3+The adding amount is 1 concentration in the washing slurryAbout 3g/L, stirring for 30min, and then adding TiO according to the Ti content in the slurry2And (3) calcining the seed crystal with the mass fraction of 4.0%, stirring for 30min, carrying out suction filtration on the bleached slurry, and carrying out secondary washing by using deionized water at the temperature of 60 ℃. And then, performing a salt treatment step, pulping and dispersing the second washing cake by using deionized water, and adding: in terms of Ti content in the slurry, in terms of TiO2Calculated mass fraction 0.2% of soluble phosphonium salt reagent (in P)2O5Calculated by K) and 0.25 percent of soluble potassium salt (calculated by K)2Calculated as O) and 0.25 percent of soluble aluminum salt reagent (calculated as Al)2O3Metering), stirring for 1h at normal temperature, putting into an oven, and drying at 120 ℃ for about 6h until the sample is dried and cracked into blocks.
Taking a proper amount of dried metatitanic acid sample to a crucible, putting the crucible into a muffle furnace for calcining, raising the temperature from 25 ℃ to 800 ℃ (the retention time is 155min) at a temperature raising rate of 5K/min, then raising the temperature from 800 ℃ to 950 ℃ (the retention time is 300min) at a temperature raising rate of 0.5K/min, and finally raising the temperature from 950 ℃ to 1000 ℃ (the retention time is 10min) at a temperature raising rate of 5K/min, and finishing calcining. And taking out the calcined product, cooling to room temperature, grinding by using a grinder, and then carrying out SEM and XRD detection, wherein the final rutile conversion rate is 98.7%, and the average particle size is 241 nm.
Example 4
Taking hydrolyzed slurry in the traditional sulfuric acid method titanium dioxide production process as a raw material, carrying out suction filtration on the hydrolyzed slurry, carrying out primary washing by using deionized water at 60 ℃, and cleaning industrial waste acid in the slurry to obtain a metatitanic acid filter cake; after primary washing, the metatitanic acid filter cake is dispersed by deionized pulping, the concentration of metatitanic acid slurry TiO2 is adjusted to be about 300g/L, and the metatitanic acid slurry is placed in a constant temperature water bath at 70 ℃ and stirred for 30 min; then adding 100 g/L98% concentrated sulfuric acid, and stirring for 30 min; taking industrial Ti3+Solution and calcined seed crystal, Ti3+The adding amount is about 1.3g/L in the first washing slurry, the mixture is stirred for 30min, and then TiO according to the Ti content in the slurry is added into the slurry2And (3) calcining the seed crystal with the mass fraction of 4.0%, stirring for 30min, carrying out suction filtration on the bleached slurry, and carrying out secondary washing by using deionized water at the temperature of 60 ℃. Then go intoAnd (3) performing salt treatment, namely pulping and dispersing the second washing cake by using deionized water, and adding: in terms of Ti content in the slurry, in terms of TiO2Calculated mass fraction 0.2% of soluble phosphonium salt reagent (in P)2O5Calculated by K) and 0.25 percent of soluble potassium salt (calculated by K)2Calculated as O) and 0.25 percent of soluble aluminum salt reagent (calculated as Al)2O3Metering), stirring for 1h at normal temperature, putting into an oven, and drying at 120 ℃ for about 6h until the sample is dried and cracked into blocks.
Taking a proper amount of dried metatitanic acid sample to a crucible, putting the crucible into a muffle furnace for calcining, raising the temperature from 25 ℃ to 800 ℃ (the retention time is 155min) at a temperature raising rate of 5K/min, then raising the temperature from 800 ℃ to 950 ℃ (the retention time is 300min) at a temperature raising rate of 0.5K/min, and finally raising the temperature from 950 ℃ to 1000 ℃ (the retention time is 7min) at a temperature raising rate of 7K/min, thus finishing calcining. And taking out the calcined product, cooling to room temperature, grinding by using a grinder, and then carrying out SEM and XRD detection, wherein the final rutile conversion rate is 99%, and the average particle size is 243 nm.
Example 5
Taking hydrolyzed slurry in the traditional sulfuric acid method titanium dioxide production process as a raw material, carrying out suction filtration on the hydrolyzed slurry, carrying out primary washing by using deionized water at 60 ℃, and cleaning industrial waste acid in the slurry to obtain a metatitanic acid filter cake; after primary washing, the metatitanic acid filter cake is dispersed by deionized pulping, the concentration of metatitanic acid slurry TiO2 is adjusted to be about 300g/L, and the metatitanic acid slurry is placed in a constant temperature water bath at 70 ℃ and stirred for 30 min; then adding 100 g/L98% concentrated sulfuric acid, and stirring for 30 min; taking industrial Ti3+Solution and calcined seed crystal, Ti3+The adding amount is about 1.3g/L in the first washing slurry, the mixture is stirred for 30min, and then TiO according to the Ti content in the slurry is added into the slurry2And (3) calcining the seed crystal with the mass fraction of 4.0%, stirring for 30min, carrying out suction filtration on the bleached slurry, and carrying out secondary washing by using deionized water at the temperature of 60 ℃. And then, performing a salt treatment step, pulping and dispersing the second washing cake by using deionized water, and adding: in terms of Ti content in the slurry, in terms of TiO2Calculated mass fraction 0.2% of soluble phosphonium salt reagent (in P)2O5Calculated by K) and 0.25 percent of soluble potassium salt (calculated by K)2Calculated as O) and 0.25 percent of soluble aluminum salt reagent (calculated as Al)2O3Metering), stirring for 1h at normal temperature, putting into an oven, and drying at 120 ℃ for about 6h until the sample is dried and cracked into blocks.
Taking a proper amount of dried metatitanic acid sample to a crucible, putting the crucible into a muffle furnace for calcining, heating from 25 ℃ to 800 ℃ (the retention time is 77min) at a heating rate of 10K/min, then heating from 800 ℃ to 950 ℃ (the retention time is 100min) at a heating rate of 1.5K/min, and finally heating from 950 ℃ to 1000 ℃ (the retention time is 10min) at a heating rate of 5K/min, and finishing calcining. And taking out the calcined product, cooling to room temperature, grinding by using a grinder, and then carrying out SEM and XRD detection, wherein the final rutile conversion rate is 98.1%, and the average particle size is 260 nm.
Example 6
Taking hydrolyzed slurry in the traditional sulfuric acid method titanium dioxide production process as a raw material, carrying out suction filtration on the hydrolyzed slurry, carrying out primary washing by using deionized water at 60 ℃, and cleaning industrial waste acid in the slurry to obtain a metatitanic acid filter cake; after primary washing, the metatitanic acid filter cake is dispersed by deionized pulping, the concentration of metatitanic acid slurry TiO2 is adjusted to be about 300g/L, and the metatitanic acid slurry is placed in a constant temperature water bath at 70 ℃ and stirred for 30 min; then adding 100 g/L98% concentrated sulfuric acid, and stirring for 30 min; taking industrial Ti3+Solution and calcined seed crystal, Ti3+The adding amount is about 1.3g/L in the first washing slurry, the mixture is stirred for 30min, and then TiO according to the Ti content in the slurry is added into the slurry2And (3) calcining the seed crystal with the mass fraction of 4.0%, stirring for 30min, carrying out suction filtration on the bleached slurry, and carrying out secondary washing by using deionized water at the temperature of 60 ℃. And then, performing a salt treatment step, pulping and dispersing the second washing cake by using deionized water, and adding: in terms of Ti content in the slurry, in terms of TiO2Calculated mass fraction 0.2% of soluble phosphonium salt reagent (in P)2O5Calculated by K) and 0.25 percent of soluble potassium salt (calculated by K)2Calculated as O) and 0.25 percent of soluble aluminum salt reagent (calculated as Al)2O3Metering), stirring for 1h at normal temperature, putting into an oven, and drying at 120 ℃ for about 6h until the sample is dried and cracked into blocks.
Taking a proper amount of dried metatitanic acid sample to a crucible, putting the crucible into a muffle furnace for calcining, heating from 25 ℃ to 800 ℃ (the retention time is 77min) at a heating rate of 10K/min, then heating from 800 ℃ to 950 ℃ (the retention time is 100min) at a heating rate of 1.5K/min, and finally heating from 950 ℃ to 1000 ℃ (the retention time is 7min) at a heating rate of 7K/min, thus finishing calcining. And taking out the calcined product, cooling to room temperature, grinding by using a grinder, and then carrying out SEM and XRD detection, wherein the final rutile conversion rate is 98.5%, and the average particle size is 257 nm.
Example 7
Taking hydrolyzed slurry in the traditional sulfuric acid method titanium dioxide production process as a raw material, carrying out suction filtration on the hydrolyzed slurry, carrying out primary washing by using deionized water at 60 ℃, and cleaning industrial waste acid in the slurry to obtain a metatitanic acid filter cake; after primary washing, the metatitanic acid filter cake is dispersed by deionized pulping, the concentration of metatitanic acid slurry TiO2 is adjusted to 300g/L, and the metatitanic acid slurry is placed in a constant temperature water bath at 70 ℃ and stirred for 30 min; then adding 100 g/L98% concentrated sulfuric acid, and stirring for 30 min; taking industrial Ti3+Solution and calcined seed crystal, Ti3+Adding into washing slurry with concentration of 1.3g/L, stirring for 30min, and adding into the slurry according to Ti content in the slurry and TiO content2And (3) calcining the seed crystal with the mass fraction of 4.0%, stirring for 30min, carrying out suction filtration on the bleached slurry, and carrying out secondary washing by using deionized water at the temperature of 60 ℃. And then, performing a salt treatment step, pulping and dispersing the second washing cake by using deionized water, and adding: in terms of Ti content in the slurry, in terms of TiO2Calculated mass fraction 0.2% of soluble phosphonium salt reagent (in P)2O5Calculated by K) and 0.25 percent of soluble potassium salt (calculated by K)2Calculated as O) and 0.25 percent of soluble aluminum salt reagent (calculated as Al)2O3Metering), stirring for 1h at normal temperature, putting into an oven, and drying at 120 ℃ for about 6h until the sample is dried and cracked into blocks.
Taking a proper amount of dried metatitanic acid sample to a crucible, putting the crucible into a muffle furnace for calcining, raising the temperature from 25 ℃ to 800 ℃ (the retention time is 155min) at the temperature raising rate of 5K/min or 10K/min, then raising the temperature from 800 ℃ to 950 ℃ (the retention time is 300min) at the temperature raising rate of 0.5K/min or 1.5K/min, and finally raising the temperature from 950 ℃ to 1000 ℃ (the retention time is 10min) at the temperature raising rate of 5K/min or 7K/min, and finishing the calcining. The calcined product was taken out and cooled to room temperature, and after being ground by a mill, the calcined product was examined by SEM and XRD, and the final rutile conversion and the average particle size were respectively shown in table 1.
TABLE 1 Effect of different temperature ramp rates on rutile conversion and average particle size
The embodiments described above are described to facilitate an understanding and use of the invention by those skilled in the art. It will be readily apparent to those skilled in the art that various modifications to these embodiments may be made, and the generic principles described herein may be applied to other embodiments without the use of the inventive faculty. Therefore, the present invention is not limited to the above embodiments, and those skilled in the art should make improvements and modifications within the scope of the present invention based on the disclosure of the present invention.
Claims (9)
1. A technological method for regulating and controlling the particle size of titanium dioxide is characterized in that the particle size of the titanium dioxide is regulated and controlled by changing the calcination temperature rise rate; the method specifically comprises the following steps:
in the calcining step for preparing the titanium dioxide, a heating rate control sectional calcining mode is adopted, the calcining process is divided into three temperature sections for sectional calcining, the temperature of the first section is 25-800 ℃, the adopted heating rate is 5-10K/min, and the retention time is 155min-77 min; in the second stage, the temperature is increased at 800-950 ℃ at the heating rate of 0.5-1.5K/min and the retention time is 300-100 min; the third section is 950-1000 ℃, the adopted heating rate is 5-7K/min, and the retention time is 10-7 min.
2. The process method for regulating and controlling the particle size of titanium dioxide according to claim 1, wherein the calcination process is performed in a muffle furnace.
3. The process method for regulating and controlling the particle size of titanium dioxide according to claim 1, wherein the calcined object is dried metatitanic acid.
4. The process method for regulating and controlling the particle size of titanium dioxide according to claim 3, wherein the particle size range of metatitanic acid is as follows: 2.0-3.5 μm.
5. The process method for regulating and controlling the particle size of titanium dioxide by changing the calcination temperature rise rate according to claim 1, which is characterized in that: the particle size range of the titanium dioxide particles obtained after calcination is 240nm-260 nm.
6. The process method for regulating and controlling the particle size of titanium dioxide by changing the calcination temperature rise rate according to claim 1, which is characterized in that: the rutile conversion rate of the titanium dioxide particles obtained after calcination is more than 98 percent.
7. The process method for regulating and controlling the particle size of titanium dioxide by changing the calcination temperature rise rate according to claim 1, which is characterized in that: the metatitanic acid is dehydrated and desulfurized at the same time within the temperature range of 300 ℃ to 700 ℃, wherein the moisture is removed in the form of hydrogen bond water and multi-layer absorbed water, and the sulfur is in the form of sulfur oxide SO2、SO3The morphology of (2) is removed.
8. The process method for regulating and controlling the particle size of titanium dioxide by changing the calcination temperature rise rate according to claim 1, which is characterized in that: from 800 ℃ to 950 ℃, anatase TiO2Rutile type TiO2And (4) transformation.
9. The process method for regulating and controlling the particle size of titanium dioxide by changing the calcination temperature rise rate according to claim 1, which is characterized in that: 950 ℃ and 1000 ℃ is the period of rapid growth of titanium dioxide crystals.
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