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Titanium dioxide drying technology
2020-07-23

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Recommended Dryer Model: XSG Series Flash Dryer

 

1. Product Overview:

Titanium dioxide is considered to be a kind of white pigment with better performance in the world. It is widely used in coatings, plastics, papermaking, printing, ink, chemical fiber, rubber, cosmetics and other industries. Titanium dioxide is chemically stable and generally does not react with most substances. In nature, titanium dioxide has three crystals: slab titanium, anatase, and rutile. The coating industry is a large user of titanium dioxide, especially rutile titanium dioxide, most of which is consumed by the coating industry. The coating made of titanium dioxide has bright colors, strong coloring power, strong dosage, low dosage, and many varieties. It can protect the stability of the medium, and can enhance the mechanical strength and adhesion of the paint film to prevent cracks. Prevent UV and moisture penetration, and extend the life of the paint film.

The plastics industry is the second largest user. Adding titanium dioxide to plastics can improve the heat resistance, light resistance and weather resistance of plastic products. It is the improvement of the physical and chemical properties of plastic products, enhancing the mechanical strength of products and extending their service life.

The paper industry is the third largest user of titanium dioxide. As a paper filler, it is mainly used in high-grade paper and thin paper. Adding titanium dioxide to the paper can make the paper have better whiteness, good gloss, high strength, thin and smooth, no penetration when printing, and light quality. Titanium dioxide for papermaking generally uses anatase titanium dioxide without surface treatment, which can act as an optical brightener and enhance the whiteness of paper. However, laminated paper requires the use of rutile titanium dioxide after surface treatment to meet the requirements of light resistance and heat resistance.

Titanium dioxide is also an indispensable white pigment in advanced inks. The ink containing titanium dioxide is durable and does not change color, the surface has good wettability and is easy to disperse. Titanium dioxide used in the ink industry can be rutile or anatase.

The textile and chemical fiber industry is another important application field of titanium dioxide. Titanium dioxide for chemical fiber is mainly used as matting agent. Since the anatase type is softer than the gold-red type, the anatase type is generally used. Titanium dioxide for chemical fiber generally does not require surface treatment, but some special varieties require surface treatment in order to reduce the photochemical effect of titanium dioxide and avoid the degradation of fibers under the photocatalysis of titanium dioxide.

The enamel industry is an important application field of titanium dioxide. Enamel grade titanium dioxide has high purity, good whiteness, fresh color, uniform particle size, strong refractive index and high achromatic power. It has strong opacification and opacity, making the coating thin after coating. Smooth and acid-resistant, it can be mixed evenly with other materials in the enamel manufacturing process, without agglomeration, and easy to melt.

Ceramic industry is also an important application field of titanium dioxide. Ceramic grade titanium dioxide has high purity, uniform particle size, high refractive index, excellent high temperature resistance, and remains gray at 1200 degrees for 1 hour. High opacity, thin coating, light weight, widely used in ceramics, construction, decoration and other materials.

There are two methods for manufacturing titanium dioxide: sulfuric acid method and chlorination method. Among them, 56% are chlorination products. More than 70% of these products are produced by major titanium dioxide factories such as DuPont in the United States. The sulphuric acid method is still the main method for titanium dioxide factories in other countries including China.

Sulfuric acid method: It is the acid hydrolysis reaction between titanium iron powder and concentrated sulfuric acid to produce ferrous sulfate, which is hydrolyzed to produce metatitanic acid, and then calcined and crushed to obtain titanium dioxide product. This method can produce anatase and rutile titanium dioxide. The advantage of the sulfuric acid method is that ilmenite and sulfuric acid can be used as raw materials at low prices. The technology is relatively mature, the equipment is simple, and the anti-corrosion materials are easy to solve. The disadvantage is that the process is long and can only be intermittent operation, wet operation, high sulfuric acid, water consumption, waste and by-products, and great environmental pollution.

Chlorination method: Chlorination method is to mix rutile or high-titanium powder with coke and then chlorinate titanium tetrachloride at high temperature, then oxidize at high temperature, and then filter, wash, dry and crush to obtain titanium dioxide product. The chlorination method can only produce rutile products. The advantage of the chlorination method is the short process and easy expansion of production capacity. High degree of continuous automation, relatively low energy consumption, less "three wastes" and high quality products.

Based on the material characteristics of titanium dioxide, based on the digestion and absorption of better foreign equipment and technology, the self-developed dryer has been successfully applied in the drying of titanium dioxide.

2. Technology Overview:

The flash dryer is mainly composed of air inlet system, heating system, feeding system, drying host, dust collecting system, exhaust system, control system and so on. When working, the wet material enters the drying chamber by the screw feeder. The material meets the hot air rotating at high speed in the drying chamber. The fine powder material is carried by the hot air to the upper end of the drying chamber, and the material that cannot be taken down falls at the bottom of the drying chamber. It is crushed by the crushing device at the bottom, the material is quickly dispersed, and the contact area between the material and the hot air increases rapidly. Under the action of centrifugal force (the top has a classification device), the product that reaches the degree of dryness and a certain degree of fineness is blown out of the classification device, and the material is quickly dried in this process.

3. Technology Principle:

The flash dryer has the advantages of high technology content, high standardization, environmental protection, safety, low consumption, simple maintenance, etc. In terms of design structure:

(1).The bottom of the dryer is provided with an inverted cone structure, which gradually expands the drying gas flow section from bottom to top. The bottom airflow is relatively large, and the upper airflow is relatively small, so as to ensure that the large particles in the lower part are in a fluidized state, while the upper part is small The particles are also in a fluidized state, and the hot air is rotated along the vertebral body, increasing the bottom wind speed, reducing the length of the cantilever part of the stirring shaft, and increasing the safety and reliability of the operation; the bearing can be placed outside the machine to effectively prevent the bearing from high temperature Zone work, thereby extending the life of the bearing.

(2).The scraper is set on the mixing teeth, the material is thrown to the wall of the machine while being crushed by the mixing teeth, and sticks to the wall surface. If it is not scraped in time, the equipment will vibrate in serious cases, even causing the mixer to suffocate. . A scraper is provided on the stirring teeth, which can peel off the materials sticking to the machine wall in time to avoid sticking to the wall.

(3).The rotation speed of the stirring shaft is controlled by the stepless speed regulating motor. Choose different speeds according to the product size requirements. The faster the stirring shaft speed, the smaller the product size.

(4).The classifier is set on the upper part of the dryer. By changing the hole diameter of the classifier and the height of the classifying section, the air flow rate can be changed to control the size and number of particles leaving the dryer, the final moisture content and the residence time of materials in the drying section.

(5).The rotation speed of the screw conveyor of the feeder is controlled by the inorganic speed regulating motor. Control the feeding speed according to the material properties and drying process parameters.

(6).The equipment has a compact structure, small footprint, and integrates drying, crushing, and classification. It is an organic combination of cyclone technology, fluidization technology, spray technology, and convection technology. It does not need to be crushed and sieved after drying, which simplifies the production process saves power and equipment costs.

4. Dryer working process:

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