In order to improve the boring speed and prevent the dry and uneven, usually mechanical mixing or rotating the container itself to increase or constantly update the heat transfer surface of the material, it is necessary to further study the adhesion of heat transfer organization. The dry equipment itself is expensive, but its characteristic is that the dust collecting system has small load, high thermal efficiency and easy recovery of the solvent. The total cost is much lower than that of the direct drying method.
(1) belt dryer
The belt dryer consists of several independent cell segments. Each unit consists of a circulating fan, heating equipment, fresh air intake system and exhaust emission system which is either alone or shared. The operation parameters of the drying medium quantity, temperature, humidity and exhaust gas circulation can be independently manipulated, and then the reliability and operation conditions of the dryer can be ensured. The machine has sensitive operation and wet material feeding. The drying process is carried out in the completely sealed box, and the working conditions are better to avoid the leakage of dust. It is especially suitable for dehydrated vegetables, Chinese herbal pieces and other materials with high moisture content and high temperature.
(2) drum scraper dryer
The drum scraper dryer is a continuous operation device which passes through a rolling cylinder and uses heat conduction to make liquid phase material or strip material attached to the outer wall of the cylinder. The material which needs drunting treatment is poured into the receiving trough of the drum dryer by the upper trough. The drums are driven by the drive equipment and rolled at the prescribed speed. Material is made up of membrane equipment and film on roller wall. The cylinder body is connected into the heating medium, and the heating cylinder body is heated by the wall of the cylinder to vaporize the material film, and then scraps the material to the dry request by scraper, and then carries it through the screw to the storage tank for packaging. The moisture content removed by transpiration can be introduced into the corresponding treatment equipment through the closed cover and the water vapor can be directly discharged from the exhaust pipe of the roof to the atmosphere. The machine is mainly used for processing liquid materials. It can be heated by steam, hot water or hot oil, and can be dried by cooling water. According to different material properties and process requirements, immersion, sprinkling, grinding and auxiliary feeding methods can be used.
(3) hollow blade dryer (leaf dryer)
Hollow impeller dryer, also known as leaf dryer, is mainly composed of W shell with jacket and two hollow propeller blades and transmission equipment. A hollow blade is placed on the shaft, and a rotary joint with heat medium is arranged at the shaft end. The heat required for dry moisture is transported to the material by the inner wall and the hollow blade wall of the W groove with a jacket. In the dry process, the hollow shaft with hollow blades is mixed with the heated material and mixed with the material, and then the heating surface is renewed. It is a continuous conduction heating dryer. The heating medium is steam, hot water or heat conducting oil. The heating medium is passed into the shell jacket and two hollow paddles, and the material is heated and dried by means of conduction heating. The structure of different material hollow paddles is different.
The machine is suitable for handling all kinds of materials with good thermal stability such as paste, granular and powdery. It can also dry and heat sensitive materials and recover solvents in dry process under special conditions. Commonly used in carbon black, light calcium carbonate, titanium dioxide, barium carbonate, nitrile uric acid, gypsum, clay, manganese dioxide, nylon and polyester chips, polyethylene, polypropylene (solvent recovery) and other materials drying or cooling.
(4) vacuum rake dryer
The dry material is added from the middle side of the vacuum rake dryer. When the material is touching with the shell wall, the appearance is constantly updated, and the dry material is directly heated by steam (or hot water and heat conducting oil), but the material water vaporizes, and the vaporized water is evacuated by the vacuum pump in time. The dry material is heated directly by the heat carrier, so that the moisture in the material is vaporized, and the vaporized water is discharged in time by the vacuum pump.
Because the vacuum level is high, the steam pressure on the surface of the dry material is far greater than that of the vapour space inside the dryer shell in the range of 400 ~ 700mmHg. Then it is conducive to the discharge of moisture and external moisture in dry materials, which is conducive to the movement of water molecules in dry materials and to the boring purpose. The vacuum rake dryer is suitable for materials that are heat sensitive, oxidizable at high temperature or easily hardened when dry. Typical dry materials include sodium acrylonsulfonate, CMC, phthalocyanine blue, dye intermediate, carboxymethyl starch, maltodextrin, anthraquinone sulfonic acid and so on.