What kind of drying equipment is a fast spin flash dryer

Quick Spin Flash Dryer Overview:

Rapid spin flash Dryer is a fast-growing and widely used drying model, also known as cyclone dryer or rotary fast dryer in China. The fast spin flash dryer organically combines fluidization, swirl, spouting, crushing, and classification technologies. It is an optimized combination of fluidization technology, swirl technology, spouting technology and convective heat transfer technology. The technical content of the equipment is high. , suitable for drying paste, granular, filter cake and slurry materials. The flash dryer has the advantages of high thermal efficiency, short drying time and good energy saving effect. Pseudo-block materials can be directly dried into powdered dry products. Due to the fast drying speed and short heating time of the materials, it is not easy to destroy the components of the dry materials, which is especially beneficial to the drying of heat-sensitive materials. The drying process is completely closed, no impurities are mixed, the quality of the finished product is high, and the operating environment is good. At present, various types of flash dryers have been designed according to different materials, and a series of products have been formed, which are more and more widely used in chemical, pharmaceutical, light industry, food, mining and other industries.

Typical drying materials for fast spin flash dryers are:

Inorganic substances: borax, calcium carbonate, hydroxide, copper sulfate, iron oxide, barium carbonate, magnesium sulfate, antimony trioxide, various heavy metal salts, synthetic cryolite, magnesium carbonate, alumina, aluminum hydroxide, silica Wait

Organics: atrazine (pesticide), lauric acid, benzoic acid, benzoic acid, bactericide, sodium oxalate, cellulose acetate, etc.;

Ceramics: kaolin, silica, clay, etc.;

Dyes: anthraquinone, black iron oxide, indigo pigment, butyric acid, titanium hydroxide, zinc sulfide, various azo dye intermediates.

Food: soy protein, starch, distiller's grains, wheat sugar, wheat starch, etc.

Pesticides, industrial waste, etc-

Fast spin flash dryers generally have the following problems: large one-time investment, large energy consumption, relatively small output, and time-consuming and labor-intensive equipment debugging. Operate under optimal conditions, so the economy is not ideal, resulting in waste. In view of these factors, Jiayi drying technicians have long concluded that the reasons are the following two main aspects. The first is the rational configuration of the system, such as measuring the quality and heat of different materials and different output requirements, determining the heat, air volume, temperature, and bag filtration. The second is how to improve the structure of the host for different materials and different system configurations. By solving these two problems, the output can be further increased, thereby improving the efficiency and achieving the purpose of energy saving. At present, the flash dryer is the main featured product of our company.

How fast spin flash dryer works
The clean air heated by the heat exchanger is blown into the air inlet, spun into the annular gap at the bottom of the drying chamber at a suitable speed, and then enters the drying chamber in the tangential direction, and rises in a spiral shape; The speed-regulated feeder is quantitatively fed into the tower. In the drying tower, the material and the hot air undergo sufficient and efficient mass-heat conversion, and the dried powder material is transported to the cyclone along with the hot air, where the finished product is collected and packaged, and the exhaust gas is further processed by the dust removal device and then emptied.
The bottom of the drying tower is equipped with a volute tangential air distributor and agitator, and the speed of the agitator is steplessly regulated by adjusting the speed of the external motor. The agitator has two functions: it can drive the hot air entering the drying chamber from the distribution chamber to generate a high-speed rotating airflow, thereby forming a stable fluidized bed, avoiding instability such as spouting and channeling caused by local sticking. Fluidization; secondly, due to the high-speed rotation of multiple sets of blades on the agitator, the bulk materials are continuously pulverized, so that the outer dry and inner wet particles are continuously wrapped, peeled, and crushed, and the surface is constantly updated, which increases the heat exchange area. Thereby, the quality and heat exchange are strengthened, and the drying rate is improved. In addition, the gap between the blade on the agitator and the wall of the drying tower is extremely small, and the material adhering to the wall is cleaned up in time to prevent the material from staying for a long time and denaturing. In order to ensure that the material does not decompose and decompose, there is a cooling jacket in the tower wall, which can guarantee 100% quality for heat-sensitive materials. The tangential air distributor of the volute type makes the tangentially entering hot air evenly rise through the bottom annular gap in a spiral shape, and the reasonable annular gap wind speed ensures good fluidization and drying of the material.
In the middle and lower part of the drying tower, the quantitative feeder with stepless speed regulation continuously feeds the material. At the same time, the material is crushed by the agitator at the bottom and then blown up by the high-speed rotating hot air, forming a relatively stable fluidized layer in the drying chamber. There is a rapid and sufficient exchange of heat and water between the material and the hot air, and most of the water evaporation is completed in this process. The material particles with high moisture content and small specific surface settle in the drying chamber because their gravity is greater than buoyancy, and they are continuously dried during the sinking process. When its gravity is less than buoyancy, the particles begin to move upward.
In the upper part of the drying chamber, there is a conical annular baffle, that is, a classifier. The material rises with the swirling airflow. Due to the centrifugal force, the bulky materials that do not meet the moisture requirements (that is, the specific gravity is larger) are affected by the centrifugal force, and their rotation radius increases. When the rotation radius is greater than the radius of the classifier, It is blocked in the drying room for further drying and pulverization, and it does not overflow until it meets the requirements. The finer pulverized body is dried in the middle of the drying chamber and then rises with the air entrainment. Because its particle size is small and meets the water content requirement (that is, the specific gravity is small), the centrifugal force is relatively small, and its rotation radius is smaller than that of the classifier. The airflow is discharged and sent to the collection device.
Features of fast spin flash dryer:
1. The inner cone structure is set at the bottom of the drying chamber, so that the cross-sectional area of the dryer gas flow continuously increases from bottom to top, the bottom gas velocity is relatively large, and the upper gas velocity is relatively small, thus ensuring that the large particles in the lower part are in a fluidized state At the same time, the small particles in the upper part are also in a fluidized state. The inner cone structure also shortens the length of the cantilever part of the stirring shaft, thereby increasing the reliability of operation. In addition, this structure can effectively prevent the bearing from working in a bad state in a high temperature area, thereby prolonging the service life of the bearing.
2. A scraper is set on the stirring teeth. When the material is rotated and crushed by the stirring teeth, it is thrown to the wall of the vessel and sticks to the wall. If the material stuck to the wall is not scraped off in time, there will be serious "scarring" phenomenon, resulting in abnormal operate. The scraper is installed on the stirring teeth to ensure that the material is peeled off before it is firmly bonded to the wall.
3. A grading ring is set on the top of the drying chamber. Its function is mainly to separate and block the materials with large particles and not yet dried, and continue to dry, so as to ensure that the product has a narrow particle size distribution and a uniform moisture content.
4. A cooling jacket is set at the hot air inlet of the cone bottom. The temperature where the hot air starts to come into contact with the material is very high, generally close to the temperature of the hot air, much higher than the temperature in the bed layer. During the operation, it is inevitable that a small part of the material will stick near the annular gap, and the residence time is too long, which will cause the material Deterioration, or even melting, in order to avoid this phenomenon, adding a local jacket can reduce the temperature of the wall of the device, so that the operation can be carried out smoothly.

5. In the high temperature area of the stirring bearing, oil cooling device is used to better protect the bearing, and compressed air is used to sweep the gap between the bearing and the stirring shaft to prevent dust from entering the bearing from the gap, which can make the bearing better. Smooth operation extends service life.

The above structural features of the flash dryer make its performance compared with other dryers have the following advantages:
1. High drying strength. Because the material is micronized by centrifugation, shearing, collision and friction, it is in a highly dispersed state, and the relative velocity between the gas and solid phases is relatively large, which strengthens mass and heat transfer.
2. Suitable for heat-sensitive materials. The high temperature area at the bottom of the dryer has a high gas velocity, and it is difficult for the material to directly contact the hot surface; in addition, it is equipped with a cooling jacket and a stirring tooth with an advantageous plate, which solves the problem of the material sticking to the wall and coking.
3. The process is simplified. Compared with other types of dryers, using a flash dryer to dry paste, mud, filter cake and other materials can be dried into a uniform powder product at one time, eliminating the need for crushing, screening and other processes.
4. Effectively control the final moisture and fineness. The adjustment of the feed and hot air temperature and the coordination of the classifier can fully control the final moisture content and finished product particle size, thus ensuring the uniform moisture content and fineness of the product.

14 points to pay attention to when purchasing a fast spin flash dryer
1. The physical and chemical properties of the materials to be dried
Material form, water content, water content, crystal water, particle size, bulk density, viscosity, heat sensitivity, softening point, phase transition point, thixotropy, toxicity, corrosiveness, odor, flammability, explosiveness, electrostatic property, air permeability , agglomeration, easy crushing of crystals or particles, etc. will affect the drying effect.
2. Drying characteristics of materials
The drying curve, critical moisture content and equilibrium moisture content under the proposed drying conditions.
3. Drying output requirements and long-term planning.
4. The influence of material commodity value and drying effect on it. Such as the influence of product moisture, pollution, temperature, wear, pulverization, pulverization, rehydration, etc. on commodity value.
5. Requirements for material recovery rate.
6. The upper and lower sequence process of material drying process. (state method involving feeding and discharging)
7. The drying method of the material in the past or the drying method of similar products.
8. Available heat sources (coal, fuel oil, electricity, steam, natural gas)
9. There are no special requirements for the size of the installation site of the spin flash dryer.
10. Environmental protection requirements - restrictions on dust emission, noise, vibration, odor, volatile matter, etc.
11. The amount of purchase capital that may be invested, and the price of local labor, land, and energy.
12. The operator level and maintenance ability of the dryer user.
13. Local ambient temperature and humidity
This mainly refers to the influence of weather changes on drying. Generally, flash dryers use atmospheric heating as the drying medium. The higher the atmospheric temperature and the lower the humidity, the more conducive to drying. Humidity and high air humidity are not conducive to the performance of the dryer's capacity and affect the output.
my country has a vast territory, and the air humidity in the north and south is very different. In some parts of the south, the humidity in winter is only 0.008kg water/kg absolutely dry air, while in spring and summer, the atmospheric humidity is as high as 0.025kg water/kg absolutely dry air, which is more than three times that of the former. For hot air drying at low exhaust temperature (<90°C), the air humidity increases in spring and summer, the drying rate will inevitably decrease, and the required time will increase. Due to the increase of atmospheric humidity, the equilibrium water content of the material will inevitably increase, and these factors will reduce the drying output, and in some cases, the output will decrease by more than 30-50%.
14. Factors affecting the production capacity of flash dryer
Due to the same drying method, the heat energy consumed by drying and dehydrating one kilogram is basically the same, and the heat source capacity of the dryer is also certain. Therefore, the main technical indicator of the dryer-drying capacity is often based on the dehydration volume per hour (or the maximum dehydration capacity). quantity) is based on. This indicator is measured under certain conditions, such as wet material type, initial moisture content, final moisture content, hot air temperature, ambient temperature and humidity, etc. As long as one of the conditions changes, it will have an impact on the production capacity of the dryer, and sometimes the impact will be greater. They are described below.
(1) Types of wet materials
The type of wet material here refers to the combination of material and moisture. Wet material can be divided into:

1.1 For thin-tube porous materials, the moisture is mainly combined in the materials by capillary force, such as sand, silica, activated carbon, biscuit ceramics, etc., the binding strength of moisture and materials is small, and drying is easier;

1.2 For colloidal materials, the penetration and combination of moisture and materials are dominant, such as glue, flour mass, etc. This material generally has high viscosity, high bonding strength between moisture and materials, and is difficult to dry;

1.3 Capillary porous colloidal materials have the properties of the above two types of materials, such as peat, clay, wood, fabrics, grains, leather, etc. There are the most types of materials, but there are also differences in the form of moisture binding between such materials, under the same conditions The difficulty of dehydration is also different. The shape of the material also has a great influence on drying, such as granular materials, larger particles are more difficult to dry than smaller particles, while large lumps with smaller thickness are easier to dry than larger ones.
(2) Moisture content of wet material,
Moisture content (moisture content) is the percentage of moisture in the total weight of wet materials.
The initial moisture content refers to the moisture content of the wet material before entering the dryer. Usually, as long as the wet material can work in the dryer, the higher the initial moisture content, the more fully the dewatering ability exhibited by the dryer will be exerted. Conversely, when the initial moisture content is higher and the final moisture content is constant, the dryer can achieve the maximum dehydration capacity, but the output of dry material decreases.

(3) Final moisture content
Generally, the post-drying stage is in the slow-speed drying stage. The lower the final moisture content is required, the greater the drying difficulty, the longer the required drying time and the lower the thermal efficiency, which also affects the output.
(4) Hot air temperature
The hot air temperature or drying medium temperature is the most sensitive condition in drying. The higher the temperature of the hot air, the more heat energy it contains, and the lower the relative humidity of the hot air, the stronger the ability to absorb and carry moisture, which is very beneficial to drying, and the drying thermal efficiency is also high. In many Drying Equipment, when other conditions remain unchanged, the dehydration capacity of the dryer is basically proportional to the change of the hot air temperature. When selecting drying equipment, it is necessary to have sufficient data on the limit temperature of the damaged material. When the material allows, try to choose a high temperature medium. It should be noted that, for many drying methods, especially rapid drying, the temperature of the dried material is much lower than the temperature of the drying medium. For example, although the hot air temperature of the airflow dryer is as high as 250 °C, the discharge temperature is generally below 60 °C .