Hollow paddle dryer is a horizontal stirring continuous drying equipment based on heat conduction. Because the stirring blades are shaped like paddles, it is called paddle dryer, and it is also called trough dryer or stirring dryer abroad.

Because the heat required for drying of this equipment relies on indirect heating by heat conduction, the drying process does not require or only requires a small amount of gas to take away moisture. It greatly reduces the heat loss of this part carried away by the airflow, improves the heat utilization rate, and is an energy-saving drying equipment. Hollow paddle dryers are widely used in the drying of powdered, granular, filter cake, and slurry materials in petrochemical, chemical, metallurgical, food, pharmaceutical, pesticide and other industries.

Changzhou Lima Drying Engineering Co., Ltd. has improved and optimized the design of the wedge-shaped hollow paddle dryer based on the absorption of advanced technologies at home and abroad. It can indirectly heat or cool paste, granular, powdered, and slurry materials, and can complete unit operations such as drying, cooling, heating, sterilization, reaction, and low-temperature calcination. The special wedge-shaped stirring heat transfer paddle in the equipment has a high heat transfer efficiency and a self-cleaning function of the heat transfer surface.

Hollow paddle dryer Working principle

The heat transfer surface of the hollow paddle dryer consists of blades, stirring shaft, wall surface, etc., and the heat transfer area of the blades accounts for a large part, so the equipment has a compact structure and a large heat transfer area per unit volume. In addition, stirring and mixing cause the materials to tumble violently, thereby obtaining a high heat transfer coefficient, so the floor space and space are very small, saving the cost of plant construction. The drying process uses less gas, the flow rate is low, and the amount of dust carried away by the gas is small, so the gas dust is easy to recover after drying, and the recovery equipment is small in size, which can save equipment investment. For the drying process that requires solvent recovery, the solvent concentration can be greatly increased. Due to the special structure of the paddles, the material is alternately squeezed and relaxed during the drying process, which strengthens the drying. The filling rate of the material in the drying chamber is very high, which can reach 80%-90%. The residence time of the material can be adjusted by adjusting the parameters such as the feeding speed, the stirring shaft speed, and the material filling degree, which can be adjusted arbitrarily from a few minutes to a few hours. In addition, the movement of the material from the feeding port to the discharge port in the dryer is basically a piston movement, and the residence time distribution is narrow, so the moisture content of the product is uniform. The paddle has a certain axial angle on the stirring shaft, so the material can be dried continuously.

Hollow paddle dryer equipment structure

Take the double-shaft type as an example to introduce its structure (hollow paddle dryers can be divided into single, double, and four). It consists of a W-shaped shell with a jacketed end face, an upper cover, two hollow shafts with blades, end covers at both ends, a rotating joint with a medium, a metal hose, and a transmission mechanism including gears and sprockets.

The core of the hollow paddle dryer equipment is two hollow shafts and hollow stirring paddles welded on the shaft. The paddle is a wedge-shaped hollow semicircle that can be passed through the heating medium. In addition to playing a stirring role, it is also the heat transfer body of the equipment. The two main heat transfer sides of the paddle are inclined, so when the material contacts the inclined surface, as the blade rotates, the particles quickly slide away from the inclined surface, so that the heat transfer surface is constantly updated and the heat transfer is enhanced. A scraper is provided at the triangular bottom of the paddle to scrape up the material deposited on the bottom of the shell to prevent dead corners.

There are certain requirements for the arrangement of the blades and the size of each part. In addition to the blades, auxiliary mechanisms are also provided in the feeding area, drying area, and discharging area to ensure stable operation of the whole machine and uniform drying. In addition, the residence time can also be adjusted.

Hollow paddle dryer equipment features

The main features of the hollow paddle dryer are:

1. The Hollow paddle dryer equipment has a compact structure, a large effective heat transfer area, and a small footprint

2. Uniform stirring, high thermal efficiency, and good drying effect

3. The paddle shafts can mesh with each other and have a self-cleaning effect to prevent the material from sticking to the wall

4. Low energy consumption and low operating costs

5. Small dust entrainment and less material loss

6. Indirect heating and no pollution to materials

7. The paddle shaft has a low speed and does not damage the shape and properties of the product

10. The equipment has large operating flexibility and runs smoothly and reliably

Application

Hollow paddle dryers have been successfully used in food, chemical, petrochemical, dyes, industrial sludge and other fields. The heat transfer, cooling and stirring characteristics of the equipment enable it to complete the following unit operations: calcination (low temperature), cooling, drying (solvent recovery), heating (melting), reaction and sterilization. The stirring blade is also a heat transfer surface, which increases the heat transfer area per unit effective volume and shortens the processing time. The wedge-shaped blade heat transfer surface also has a self-cleaning function. The compression-expansion stirring function makes the material mixed evenly. The material moves in a "piston flow" along the axial direction. In the axial range, the temperature, humidity and mixing degree gradient of the material are very small.

Using heat transfer oil as the heat medium, the Hollow paddle dryer equipment can complete low-temperature calcination. For example: calcium sulfate dihydrate (CaSO4·2H2O) is calcined and converted into calcium sulfate hemihydrate (CaSO4·1/2H2O). Sodium bicarbonate (NaHCO3) is calcined and converted into soda ash (Na2CO3), etc.

Introducing a cooling medium such as water, cooling brine, etc. can be used for cooling. For example, the paddle type cooling machine used in the soda ash industry replaces the old air cooling cooling machine, saving energy and tail gas treatment equipment, reducing operating costs, and can also be used for cooling titanium dioxide, nickel-iron alloy powder and various powdery and granular materials. In a single machine, the material can be cooled from 1000℃ to less than 40℃.

The main function of the drying equipment is not to use hot air, so that solvent recovery, energy consumption, and environmental control are in an ideal state for easy handling. It is particularly suitable for solvent recovery, flammable and oxidizable heat-sensitive materials. It has been widely used in the fine chemical, petrochemical, and dye industries.

The uniformity of temperature, humidity, and mixing degree in the axial range allows the equipment to be used for heating or melting, or for some solid material reactions. It has been successfully used in the compound fertilizer and modified starch industries. The hollow paddle dryer can be used to sterilize food and flour. The large heating area per unit effective volume quickly heats the material to the sterilization temperature, avoiding long-term heating and changing the quality of the material.

Applicable materials

1. Petrochemical industry: polyolefin powder, polycarbonate resin, high and low density polyethylene, linear low density polyethylene, polyacetal particles, nylon 6, nylon 66, nylon 12, acetate fiber, polyphenylene sulfide, propylene resin, engineering plastics, polyvinyl chloride, polyvinyl alcohol, polystyrene, polypropylene, polyester, polyoxymethylene, styrene-acrylonitrile copolymer, ethylene-propylene copolymer.

2. Environmental protection industry: PTA sludge, electroplating sewage sludge, boiler soot, pharmaceutical factory waste residue, sugar factory waste residue, monosodium glutamate factory waste residue, coal ash.

3. Feed industry: soy sauce residue, bone-based feed, wine lees, food scraps, apple residue, orange peel, soybean meal, chicken bone feed, fish meal, feed additives, biological sludge.

4. Food industry: starch, cocoa beans, corn kernels, salt, modified starch, medicines.

5. Chemical industry: soda ash, nitrogen, phosphorus and potassium compound fertilizer, kaolin, bentonite, white carbon black, carbon black, phosphogypsum, sodium oxide fluoride, nitric acid, calcium, magnesium carbonate, sodium cyanide, aluminum hydroxide, barium sulfate, calcium sulfate, calcium carbonate, dyes, molecular sieves, saponin.

Hollow Paddle Dryer Specifications