Briefly discuss the application of flash dryer in chemical production
Dryer is an important equipment in the chemical industry. It is a machine that uses heat energy to reduce the moisture of materials and is used for drying materials. The dryer vaporizes the wet part of the material through heating to obtain the solid material with specified wet content. The purpose of drying is for material use or further processing needs.
In chemical production, especially in the process of fine chemical industry, we often use powder drying equipment, commonly used powder drying equipment includes: flash dryer, air dryer, microwave dryer, vacuum dryer, double cone dryer and so on. Next, we take the flash dryer as an example for further learning.
The actual scene of flash dryer and different heating methods are shown in the figure.
Introduction of flash dryer
Flash dryer is a new type of continuous drying equipment which integrates drying, crushing and screening. It is especially suitable for drying filter cake, paste and mud paste. The drying time of the wet material in the drying tower is only 5-8 seconds, and the water evaporates instantaneously. The quality of the dried product has a lot to do with the drying temperature, wind speed, air volume and crushing speed.
The flash dryer is composed of heater, feeder, stirring crushing system, classifier, drying main, cyclone separator, bag dust collector, fan and so on.
Flash dryer is by the hot air tangentially into the bottom of the dryer, driven by the stirrer to form a strong rotating wind field. The material enters the dryer by the screw feeder, under the strong action of the high-speed rotating stirring paddle, the material is dispersed by impact, friction and shear force, and the block material is quickly crushed, fully in contact with the hot air, heated and dried. The dried material is carried into the dust collection system by the air stream for collection and treatment, which meets the requirements of environmental protection. Dust content "50mg/m3 tail gas is discharged by the induced draft fan to complete the entire drying process.
the working principle of flash dryer
The hot air enters the annular gap at the bottom of the drying chamber in the tangential direction from the inlet pipe and rises spirally. At the same time, the material is quantitatively added into the tower by the feeder and has full heat exchange with the hot air. The large and wet material is mechanically broken under the action of the agitator, and the material with low wet content and small particle size rises with the rotating air flow and is transported to the separator for gas-solid separation. The finished product is collected and packaged, while the exhaust gas is treated by a dust removal device and emptied.
flash dryer suitable materials
It is suitable for plate and frame filter or centrifuge dewatering slurry, filter cake, paste material. Such as :1 inorganic: boric acid, calcium carbonate, hydroxide, copper sulfate, iron oxide, barium carbonate, antimony trioxide, all kinds of metal hydroxide, all kinds of heavy metal salts, synthetic cryolite, etc.; 2 Organic matter: Atrazine (pesticide insecticide), lauric acid, benzoic acid, benzoic acid, germicidal Dan, sodium oxalate, cellulose acetate, etc. 3 Ceramics: kaolin, silicon trioxide, clay, etc. 4 Dyes: anthraquinone, black iron oxide, indigo pigment, butyric acid, titanium hydroxide, zinc sulfide, various azo dye intermediates.
flash dryer characteristics
1. The use of double air duct tangential air inlet avoids the velocity non-uniformity of the rotating field in the radial flow field.
2. Effectively control the final moisture and fineness, through the coordination and unification of the swirl sheet and the inlet air speed.
3. The rotary blade layout is unique, with small wear, wide contact area, large cutting force and other characteristics.
4. Good at handling heat-sensitive materials, the bottom of the main engine belongs to the high temperature area, the area has high gas speed and high cooling water protection device, to avoid the possibility of coke discoloration of materials.
5. Low system resistance, high thermal efficiency, good operating environment, low labor intensity.
6. The new type of sealing structure for the main machine, the life cycle of the main machine bearing is extended and the bearing seat is equipped with a water spacer circulating cooling device.
7. The drying room has high circumferential gas speed and short residence time of materials, which effectively prevents the material from sticking to the wall and the deterioration of heat-sensitive materials, and can be dried into uniform powder products at one time, eliminating the grinding, screening and other processes.
8. The drying chamber is equipped with grading ring and swirl sheet, and the fineness and final moisture of the material can be adjusted. The special air distribution device reduces the resistance of the equipment and effectively improves the drying uniformity of the material.
9. The bottom of the dryer is equipped with a special cooling device and air pressure seal to avoid deterioration of the material in the bottom high temperature area.
10 Can effectively control the final moisture and fineness, through the feeding, hot air temperature, classifier adjustment, to ensure that the product moisture content and fineness uniform.
11. The organic combination of swirl, fluidization, jet and grinding classification technology, compact equipment, small size, high production efficiency, continuous production, to achieve "small equipment, large production".
12. The material residence time is short, the finished product is of good quality, and can be used for drying heat sensitive materials. Negative pressure or micro negative pressure operation, good tightness, high efficiency, eliminate environmental pollution.
The purified and filtered air is then heated to ~ 230 ° C through the heater and enters the flash dryer. The wet material is fed into the screw feeding mechanism by the conveying device, and the screw feeding device can be stepless speed regulation. After extrusion, the material is forced into the main tower, and then crushed by high-speed rotating blades with different angles, and then affected by high-speed high temperature air into the main drying tower of flash dryer, high-speed rotation, entrain rise, then the air temperature drops rapidly, and the material water evaporates rapidly to complete the drying process. The dried material enters the pulse bag dust collector with high speed and high temperature air flow. The air flow enters from the outside of the filter bag and is discharged upward. In order to prevent the accumulation of material in the filter bag, the pulse solenoid valve is timed and the high-pressure air flow (0.5 ~ 0.6Mpa) is input from the upper part of each filter bag in turn, and the filter bag is repeatedly recoilled to achieve a higher dust removal effect.
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