Air dryer

Introduction Air dryers use a high-speed, flowing hot air stream to suspend wet starches and dry them during air flow. With high heat transfer coefficient, heat transfer area, short drying time and other characteristics. Airflow drying, also known as "flash drying", is the application of dilute phase transport in the solidification of solids in the drying process. The method is that the heating medium and the solid particles to be dried are in direct contact with each other, and the solid particles to be dried are suspended in the fluid. Therefore, the two phases have a large contact area, which strengthens the process of heat and mass transfer, and are widely used in the drying unit operations of bulk materials. .

Air Dryer - Mechanical Category Straight Air Dryer The wet material is added to the vertical tube by the feeder. Air is blown into the fin heater through the blower, heated to a certain temperature and blown into the vertical tube. The speed in the tube is determined by the size of the wet particles. And the density is generally greater than the sedimentation velocity of the particles (about 10-20 m/s). The dried granules are carried out by the intense air flow and are sent to two cyclone separators that are connected in parallel. They are sent via a screw conveyor and the tail gas is vented via a bag filter. Because of the short residence time, it is often necessary to use two or more cascaded processes for some products.

A cyclone airflow dryer. The particles of dried material entrained by the hot air flow enter the cyclone dryer in a tangential direction and generate a rotating motion along the hot wall, so that the particles of the material are in a state of suspended rotation and dried. The wall may be provided with a steam jacket as required. The drying process is greatly strengthened. In addition, due to the smashing of the particles and the wall, the contact area of ​​the gas-solid phase increases, which also strengthens the drying process. It is particularly suitable for heat-sensitive bulk materials that are highly hydrophobic and are not afraid of crushing. However, it is not suitable for materials with high water content, large viscosity, low melting point, easy sublimation and explosion, and easy static effect.

Pulse air dryer Pulse air dryer is a type of air dryer. During the drying operation, the tube diameter is alternately reduced or enlarged to make the air flow and the particles flow at different speeds. The relative velocity and heat transfer area between the air flow and the particles are larger, thereby enhancing the heat and mass transfer rate. In addition, the air flow rate in the enlarged tube is greatly reduced, which in turn increases the drying time.

Air Dryer - Mechanical Principles Wet materials are transported into the dryer at the same time as the heated natural air enters the dryer. The two are fully mixed. Due to the large heat exchange area, they can be evaporated and dried in a very short time.

After drying, the finished product is discharged from the cyclone separator and a small part of the flying powder is recycled by a cyclone dust collector or a bag filter. Q-type airflow dryer is a negative pressure operation, the material does not pass through the fan; QG-type airflow dryer is a positive pressure operation; material through the fan with a grinding effect; FG-type airflow dryer is an exhaust circulation type; JG-type airflow dryer is enhanced The type of air dryer is a combination of flash drying and air drying.

The fan with dispersing effect is especially suitable for airflow drying of heat-sensitive materials. High-speed swirling fan impellers can cleave wet, even agglomerated materials until they disperse, stirring, mixing, and then parallel flow of the material and the hot gas stream during the dispersion process. This type of equipment, suitable for dry filter blocks, but also belongs to the surface moisture content, moisture content ≤ 40%, if the processing volume is large or the finished product requirements dry to less than 15%, you can use two air flow drying. When the moisture content of the material exceeds 40%.

However, when the feed rate is ≤60%, it is difficult to feed materials. Mixers should be used to reduce the feed moisture by mixing dry materials. At this time, the total output of the drying equipment will be greatly reduced. This is economical. It is not balanced. Therefore, the user should first use the mechanical method (centrifugal dehydration or pressure filtration) to reduce the feed moisture as much as possible to ensure the smooth operation of the drying operation.

Airflow Dryer - Mechanical Construction Direct Feed It is currently the most widely used one and is suitable for applications where wet materials are well dispersed and only surface moisture is removed. Such as drying synthetic resins, certain drugs, organic chemicals, coal, starch and flour. If the moisture content of the wet material is high, it can be easily agglomerated when the material is added, and a part of the dried product can be used as a return material and mixed with the wet material in the compound feeder to facilitate the drying operation.

A gas flow drying device with a disperser and a disperser. A squirrel cage disperser is used to disperse the material under the drying tube. It is suitable for bulk materials with low moisture content and good looseness, such as centrifuges, filter cakes of filters, and phosphogypsum, calcium carbonate, sodium fluorosilicate, clay, coffee grounds, sludge residue, corn residue, etc. .

The air flow drying device with a pulverizer device and a pulverizer is equipped with an impact type hammer mill under the air flow drying pipe to crush the wet material, reduce the particle size, increase the surface area of ​​the material, and intensify drying. Therefore, a large amount of moisture is evaporated during the crushing process, and in general, 80% of the amount of vaporized water can be completed. In this way, it is easy to use higher intake air humidity to obtain large production capacity and high heat transfer efficiency.

Air dryer-machine uses air dryer The hot air enters the dryer and rapidly impacts the material and mixes with the material in an instant to maximize the contact area between the material and the air, thereby quickly evaporating moisture. The gas-solid two phases are separated by dust removal. After getting the product. The pulse air drying is based on the straight tube air dryer with a thicker buffer tube. The purpose is to increase the relative motion of the gas-solid two phases and increase the drying rate. It is suitable for the drying of filter cake materials with little or no stickiness, and it usually needs mechanical dehydration before drying. The drying time of the air dryer is generally 1-4 seconds, and the product has left the dryer before the temperature has risen, so it is suitable for drying heat-sensitive materials.

The dry water form is dominated by surface water, and it is more difficult to meet the technological requirements for materials containing more internal water. The machine can be designed into a blast system, inducer system, and drum inducer system based on process requirements. The blower can double as a diffuser. In the drum induced draft fan system, the fan can be infinitely variable by the frequency converter, and the “0 pressure” of the system can be accurately controlled at the inlet or at the air leakage location of the cyclone separator. For flammable and explosive materials, ordinary welding pipes are easy to accumulate and lead to high temperatures. The factory has a unique processing technology to ensure that the materials such as the inner wall of the drying pipe and the flange connection are absolutely smooth to ensure that the materials do not stay in the device.

Drying strength, equipment investment Province: air flow drying equipment is the largest amount of processing, evaporation capacity of water from 50kg/h-1500kg/h, while the equipment is small, investment, is not comparable to other drying equipment.

High degree of automation and good product quality: The air-drying materials are all in the pipeline, and the drying time is very short (only 0.5 to 2 seconds). Therefore, automation can be achieved, products are not in contact with the outside world, pollution is small, and the quality is good.

Air Dryer Drying Strength High Air Flow Drying Due to the high gas velocity, the particles are well dispersed in the gas phase, and the total surface area of ​​the particles can be regarded as the dry effective area. Therefore, the drying effective area is greatly increased. At the same time, due to the dispersion and agitation during drying, the vaporized surface is continuously renewed. Therefore, the dry heat transfer and mass transfer processes have greater strength. Short drying time The gas-solid two-phase contact time is very short. The drying time is generally 0.5 to 2 seconds and the longest is 5 seconds. Heat denaturation of a material is generally a function of temperature and time. Therefore, heat-sensitive or low-melting materials do not cause overheating or decomposition and affect their quality.

Airflow Dryer High Thermal Efficiency Airflow drying uses gas-solid phase cocurrent operation, and, in the surface gasification phase, the material is always in the wet bulb temperature of the gas with which it is connected, generally does not exceed 60 ~ 65 °C, the temperature of the material rises at the end of drying At this stage, the gas temperature has been greatly reduced and the product temperature will not exceed 70-90°C. Therefore, high temperature gas can be used. An air-drying tube with a diameter of 0.7m and a length of 10-15m can process 25 tons of coal or 15 tons of ammonium sulfate per hour. Air dryer has simple equipment, small footprint and low investment. Compared with the rotary dryer, the floor space is reduced by 60% and the investment is about 80%. At the same time, the unit processes of drying, smashing, sieving and conveying can be combined to operate, which not only simplifies the flow, but also facilitates the automatic control of the operation. Wide range of applications Air drying can be used for a variety of powdered materials.

In the choice of heating method, the airflow drying equipment has greater adaptability, the user can use steam, electricity, hot stove heating according to the conditions of the region, and can also choose according to the material heat-resistant temperature (or hot air temperature): ≤ 150 °C When steam heating is available, ≤200°C, electric heating (or steam heating, electric compensation or heat-conducting oil heating); ≤300°C, coal-fired hot air furnace; ≤600°C, oil-fired hot air furnace.

Air Dryer - Mechanical Maintenance Daily Maintenance Content 1. Check the automatic drain valve on the prefilter before every shift every day.

2. Check whether the tower changing and boosting are normal.

3. Check operating conditions, inlet pressure, inlet temperature, and air flow.

4. Check the moisture indicator, blue for dry, pink for wet.

5. Check if the muffler is dirty, and if the regeneration tower back pressure is too high, the muffler needs to be replaced.

6. Check the pre-filter and post-filter pressure drop. If the pressure drop exceeds 0.5 bar, replace the filter element.

Monthly maintenance content 1. Check the air filter with no heat and air flow dryer. Replace if necessary.

2. Check the air filter of the air dryer guide filter and replace if necessary.

3. Check the suction filter of the air dryer and replace if necessary.

Quarterly maintenance content 1. Check the front and rear filter cartridges, check for clogging and possible damage, and replace as necessary.

2. Use compressed air to purge the safety valve.

3. Check the dew point status of the output.