Conduction drying is also called contact drying, very suitable for wet particles, and conduction dryer thermal efficiency is higher. The evaporated water vapour or organic solvent is extracted by vacuum or discharged by a small amount of air, which is the main carrier of moisture content. Vacuum operation is recommended for heat-sensitive granular materials. In the conduction dryer, the blade dryer is used to dry paste materials. A rotary dryer with an inner flow tube has been designed and put into use. Vacuum drying is expensive to operate. It is only recommended when the material must be dried under low temperature or hypoxia state, or when the material will deteriorate when it is dried under heating medium and high temperature.
(1) Hollow blade dryer (blade dryer) Hollow blade dryer, also known as the blade dryer, mainly with a jacket W shaped shell and two hollow blade shaft and transmission device composition. The shaft is arranged with hollow blades, and the shaft end is equipped with a rotating joint for hot medium introduction. The heat required to dry the water is transmitted to the material by the inner wall of the W-shaped groove with a jacket and the hollow blade wall. In the drying process of the material, the hollow shaft with hollow blade is used to heat the material and stir the material at the same time, so as to renew the heating surface. It is a continuous conduction heating dryer. The heating medium is steam, hot water or heat conducting oil. The heating medium was passed into the shell jacket and two hollow blade shafts, and the materials were heated and dried by conducting heating. The structure of hollow blade shafts of different materials was different.
The machine is suitable for processing all kinds of materials with good thermal stability, such as paste, granule, powder, etc. It can also dry heat-sensitive materials and recover solvent in the drying process under special conditions. It is often used for drying or cooling materials such as carbon black, light calcium carbonate, titanium dioxide, barium carbonate, nitrile uric acid, gypsum, clay, manganese dioxide, nylon and polyester chips, polyethylene, polypropylene (recycled solvent), etc.
2 vacuum rake dryer dry material from vacuum rake dryer shell above middle, constantly rotating stirring rake tine, material, when in contact with the shell wall surface constantly updated, dry material by indirect heating steam or hot water, heat conduction oil, but the material moisture evaporation, evaporation of moisture from the vacuum pump away in time. The dry material is indirectly heated by the heat carrier to vaporize the water in the material, and the vaporized water is discharged in time by the vacuum pump. Due to the high vacuum degree of operation, generally within the range of 400 ~ 700mmHg, the water vapor pressure on the surface of the dried material is much higher than the water vapor pressure in the evaporation space in the dryer housing. Thus, it is beneficial to the discharge of moisture inside and on the surface of the dried material and to the movement of water molecules of the dried material to achieve the purpose of drying. Vacuum rake dryer is suitable for materials that are heat-sensitive, easy to oxidize at high temperature or easy to harden during drying, as well as materials that must be recovered by steam discharged during drying. Typical dry materials have sodium acrylate, CMC, phthalocyanine blue, dye intermediates, carboxymethyl starch, maltodextrin, anthraquinone sulfonic acid and so on.
(3) Belt drier A belt drier is composed of several independent unit segments. Each unit segment includes a circulating fan, a heating unit, a separate or communal fresh air pumping system, and an exhaust discharge system. The operation parameters of drying medium quantity, temperature, humidity and tail gas circulation can be independently controlled, so as to ensure the reliability of the operation and optimize the operating conditions of the belt dryer. Flexible operation, wet material feeding, drying process in a completely sealed box, good working conditions, to avoid the leakage of dust. It is suitable for drying sheet, strip and granule materials with good air permeability, especially for dehydrated vegetables, Chinese medicine prepared slices and other materials with high water content but not high temperature.
(4) Drum Scraper Dryer Drum Scraper dryer is a rotating cylinder, in the way of heat conduction, attached to the outer wall of the cylinder liquid phase material or ribbon material, a continuous operating equipment for drying. The material liquid to be dried flows into the receiving tank of the drum dryer from the high slot. The drying drum rotates at the specified speed under the driving device. The material is formed on the surface of the drum wall by a film distributing device. Heating medium is continuously passed into the cylinder, heating the cylinder body, heat transfer by the cylinder wall to vaporize the wet material film, and then through the scraper to meet the drying requirements of the material scraping down, through the spiral transport to the storage tank, for packaging. Depending on its nature, the moisture content removed by evaporation may be introduced into the corresponding treatment device through a sealed cover; It is usually water vapor and can be released directly into the atmosphere from the exhaust pipe at the top of the hood. This machine is mainly used for treating liquid materials, which can be heated and dried by steam, hot water or hot oil, and cooled by cold water. According to different material properties and process requirements, it can adopt immersive, spray, roll and auxiliary feeding methods.
(5) Double-cone rotary vacuum dryer Double-cone rotary vacuum dryer body is slightly like olive shape, both ends are covered, and two axes are set in the middle to support the body. The body is equipped with a jacket for heating, and the body can be rotated during drying, so that the material and the wall of the device are in constant contact, which overcomes the disadvantage of low thermal efficiency of materials in vacuum oven mainly relying on the conduction of the heating barrel. Rotary vacuum dryer has been widely used in fine chemical industry, medicine, etc. It is not suitable for materials with high viscosity or strong adhesion in rotary process. The equipment is mainly used for the concentration, mixing, drying and low-temperature drying of powder, granular and fibrous materials (such as biochemical products, etc.) in the pharmaceutical, chemical, food and other industries. It is more suitable for the drying of materials that are easy to oxidize, volatile, heat sensitive, strong stimulation, toxic materials and materials that are not allowed to destroy crystals.
(6) The evaporation temperature of volatiles contained in the evaporation of materials can be reduced after the vacuum oven is decompressed. It is suitable for drying all kinds of heat-sensitive and easily oxidized materials. This device is usually a cylinder or other shell capable of vacuum operation, in which electric heat or hot water and heat conduction oil are heated through a heating plate or a heating tube. It is suitable for small batch batch production.
Oven is a general drying equipment, applicable to a wide range, tray type intermittent drying equipment, used in pharmaceutical, chemical, food. Heating, curing, drying and dehydration of materials and products in light industry, heavy industry and other industries. Such as API, raw medicine, Chinese medicine yinpian, extract, powder, granule, granule, water pill, packaging bottle, pigment dye, dehydrated vegetable, dried melon and fruit, sausage, plastic resin, electrical components, baking paint, etc.
(7) Freeze-drying Machine Freeze-drying machine is to obtain dry materials by first cooling and freezing the material liquid and then decompressing and sublimating the ice. Since the whole process takes place below the freezing point, it is often used for drying heat-sensitive items. It is difficult to heat frozen materials in vacuum, and the water vapor condensing and sublimating under reduced pressure needs a larger refrigeration system, so the drying cost is high. Freeze moisture in highly heat-sensitive materials and keep them below freezing in a high vacuum. To sublimate water and separate it from material. The loss of effective components in the material is small, but the drying rate is low.
On 2018-08-08 11:45:46
