Hollow Paddle Dryer

Overview

  The hollow paddle dryer relies on indirect heating through heat conduction for the heat required for drying, so the drying process requires no or only a small amount of gas to carry away moisture. This greatly reduces the heat loss carried away by the airflow, improves heat utilization, and makes it an energy-saving drying device. Paddle dryers are widely used in the petrochemical, chemical, metallurgical, food, pharmaceutical, pesticide, and other industries for drying powdery, granular, filter cake, and slurry materials.
  Based on the absorption of advanced domestic and foreign technologies, Wuxi Dongsheng Spray Drying Machinery Factory has improved and optimized the design of the wedge-shaped hollow paddle dryer, which can indirectly heat or cool paste-like, granular, powdery, 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 paddles in the equipment feature high heat transfer efficiency and a self-cleaning function for the heat transfer surface.

Working Principle

  The heat transfer surfaces of the hollow paddle dryer consist of several parts, including the paddles, the stirring shaft, and the walls, with the paddles accounting for a large proportion of the heat transfer area. Therefore, the equipment has a compact structure and a large heat transfer area per unit volume. In addition, the stirring and mixing cause the material to tumble vigorously, resulting in a high heat transfer coefficient. As a result, both the floor space and the space required are very small, saving on plant construction costs. The drying process uses a small amount of gas at a low flow velocity, so the amount of dust carried away by the gas is small. This makes dust recovery after drying convenient, and the recovery equipment is small in size, saving on equipment investment. For drying processes that require solvent recovery, the solvent concentration can be greatly increased. Due to the special paddle structure, the material is alternately squeezed and relaxed during the drying process, which enhances drying. The filling rate of the material in the drying chamber is very high, reaching 80%–90%. The residence time of the material can be adjusted from a few minutes to several hours by regulating parameters such as the feed rate, the stirring shaft speed, and the material filling degree. In addition, the material moves from the feed inlet to the discharge outlet inside the dryer essentially in a plug-flow manner, resulting in a narrow residence time distribution and therefore a uniform moisture content in the product. The paddles have a certain axial angle on the stirring shaft, enabling continuous drying of the material.

Features

  1. Compact equipment structure, large effective heat transfer area, and small floor space
  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, preventing material from sticking to the walls
  4. Low energy consumption and low operating costs
  5. Low dust entrainment and low material loss
  6. Indirect heating without contaminating the material
  7. Low paddle shaft speed, which does not damage the shape or properties of the product
  8. High operational flexibility, stable and reliable operation

Applications

  1. Petrochemical industry: polyolefin powder, polycarbonate resin, high-density and low-density polyethylene, linear low-density polyethylene, polyacetal pellets, Nylon 6, Nylon 66, Nylon 12, cellulose acetate, polyphenylene sulfide, acrylic 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, MSG factory waste residue, coal ash.
  3. Feed industry: soy sauce residue, bone-based feed, distiller's grains, food scraps, apple pomace, orange peel, soybean meal, chicken bone feed, fish meal, feed additives, biological sludge.
  4. Food industry: starch, cocoa beans, corn kernels, salt, modified starch, pharmaceuticals.
  5. Chemical industry: soda ash, NPK compound fertilizer, kaolin, bentonite, white carbon black, carbon black, phosphogypsum, sodium fluoride, nitric acid, calcium, magnesium carbonate, sodium cyanide, aluminum hydroxide, barium sulfate, calcium sulfate, calcium carbonate, dyes, molecular sieves, saponin.