What is paddle dryer?
Paddle dryer is a kind of low-speed stirring dryer, which sets stirring paddles inside the equipment so that the wet material section is in full contact with the heat carrier and hot surface under the stirring of the paddles, so as to achieve the purpose of drying low-speed stirring dryer. The structure form is generally horizontal, double-axis, or four-axis. The paddle dryer is divided into hot air type and conduction type. In the conduction type, the hot carrier is not in direct contact with the dried material, but the hot surface is in contact with the material. The advantages of the conduction type are that the material is not easily contaminated, has high thermal efficiency, small exhaust volume, and is relatively small in size, which is conducive to saving energy and preventing air pollution. The sludge paddle dryer is the most common type of machine for paddle dryers, which is the paddle dryer for sludge.
Working principle of paddle dryer
The material enters the heat exchange chamber along the inlet baffle and is turned and lifted by the high-speed rotating paddle, the material is mixed with the high-temperature hot gas, and the moisture on its surface is transformed into water vapor after heat absorption. Under the action of the paddle, the material from the heat exchange chamber is into the first drying chamber, the material is also turned by the paddle, lifting, in mixing with the hot air, the surface residual moisture is further vaporized. When the separation chamber for material gas separation from the discharge port. In the role of the induced draft fan, the airflow in the drying chamber is in a certain direction, high-temperature hot air from the air inlet into the drying chamber, and low-temperature hot air, and water vapor gas mixture from the exhaust port are pumped out. This is the paddle dryer working
The drying chamber
is the drying space of the paddle dryer, which is a metal cylinder with an oval cross-section, large at the top and small at the bottom, and the stirring shaft is installed at its lower part. The drying chamber is divided into 4 spaces by two curtains and a baffle, which are: heat exchange chamber, first drying chamber, second drying chamber, and separation chamber. Their functions are as described before. The drying chamber is also equipped with inlet and outlet ports, air inlet and outlet ports, access holes, and observation holes. The air-material partition is set at the air inlet, which has the function of blocking the material from blocking the air inlet and distributing the hot air evenly. The curtain inside the drying chamber is joined together by several steel plates and can be lifted up, which helps to increase the operation space when replacing the paddle and liner plate and other maintenance work. At the bottom of the drying chamber, because the stirring paddle keeps turning the material, it is greatly worn, so it is equipped with a wear-resistant lining plate, which is bolted to the body and is very convenient to replace. The base of the tail end of the drying chamber is a movable leg, which can prevent the barrel from thermal expansion and contraction to produce internal stress on the paddle dryer damage.
Composition of paddle dryer
Paddle dryer consists of two to four intermeshing blade shafts, a W-shaped housing with a sheath, a base and a drive component. The whole drying process of the material is carried out in an airtight condition, and the organic volatile gases and malodorous gases are sent to the exhaust gas treatment equipment in an airtight atmosphere to prevent environmental pollution.
The paddle dryer has a compact structure and covers a small area. From the structure of the equipment, it can be seen that the heat required for drying is mainly supplied by the wall of the hollow blade placed on the hollow shaft, while the heat transfer from the jacket wall is only a small part. Therefore, the heat transfer area per unit volume of the equipment is large, which can save the equipment floor space and reduce the infrastructure investment. High thermal utilization rate. The sludge dryer uses conduction heating, all heat transfer surfaces are covered with materials to reduce heat loss; there is no hot air to take away heat, and the heat utilization rate can reach more than 90%.
The wedge-shaped blades of the paddle dryer have a self-cleaning capability, which allows them to improve the heat transfer of the blades. Rotating blade slope and particle or powder layer of the movement of the lax force occurs so that the sludge attached to the heating slope automatic blade adhere to the effective heat transfer function. In addition, because the two axes of the blade reverse rotation, replacement segmentation tightening (when the two axes blade closer to each other) and expansion (when the two axes blade farther away from each other) of the mixing function, heat transfer uniformity, heat transfer effect to improve. Typical use of paddle dryer in environmental protection industrial materials: electroplating sludge, pharmaceutical plants, coal ash, etc. The paddle dryer is heated directly instead of taking away much heat. The outer wall of the paddle dryer is equipped with thermal insulation, which greatly reduces energy consumption. The paddle dryer can directly heat or cool pastes, granules, powders and slurries, and can complete unit operations such as drying, cooling, heating, sterilization, reaction and low-temperature combustion.
Feature of paddle dryer
a. The equipment structure is compact and the installation covers a small area. As can be seen from the structure of the equipment, the heat required for drying is mainly provided by the wall surface of the hollow paddles arranged on the hollow shaft, while the heat transfer from the wall surface of the jacket only accounts for a small part. Therefore, the heat transfer surface per unit volume of the equipment is large, which can save the equipment floor space and reduce the infrastructure investment.
b. High heat utilization rate. Sludge dryer adopts conduction heating method for heating, and all heat transfer surfaces are covered by materials, which reduces heat loss; no hot air takes away heat, and heat utilization rate can reach more than 90%.
c. The wedge-shaped paddle has a self-cleaning capability that enhances the paddle's heat transfer action. The dispersion force generated by the inclined surface of the rotating paddle and the joint motion of the particle or powder layer makes the sludge attached to the heating inclined surface remove automatically, and the paddle maintains an efficient heat transfer function. In addition, due to the reverse rotation of the two shaft paddles, the heat transfer is uniform and the heat transfer effect is improved by alternately segmenting the compression (when the two shaft paddle surfaces are closest together) and expansion (when the two shaft paddle surfaces are farthest apart) mixing functions.
Rotary vacuum paddle dryer
Rotary vacuum paddle dryer is widely used for drying materials in cement, mining, construction, chemical, food, compound fertilizer and other industries. The lower feeder installed inside the machinery has a thermocouple to control the drying temperature. The temperature change at the feed end of the dryer can be controlled by a thermometer displaying the internal drying temperature (generally 250-350°C).
Applications of rotary vacuum paddle dryer
a. Although the rotary paddle dryer can dry materials involving many industries, it is mainly used in the drying of metal and non-metallic minerals, as well as the cement industry and coal mine slime clay.
b. When using the vacuum paddle dryer to dry various materials, further equipment improvements are made to make it possible to make reasonable use of the machinery when drying various materials, making it possible to carry out simple operations regardless of which materials are dried.
c. Rotary vacuum paddle dryer is mainly used for building materials, metallurgy, chemical industry, cement plant limestone slag, coal drying powder, slag, clay, and stone.
Hollow paddle dryer
Hollow paddle dryer is a kind of horizontal stirring dryer mainly for heat conduction. This kind of industrial paddle dryer is suitable for drying granular and powder materials, and it can also dry paste materials smoothly.
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