Chillers and dryers are also widely used in various industries. Through the previous articles, I believe that you also know that the classification of chiller is very wide, such as air-cooled chiller, water-cooled chiller, screw chiller and many more. The classification of dryers is also more detailed. Here are seven types of dryers, including vacuum rake dryers, belt dryers, roller scraper dryers, and so on, according to the mainstream distribution.
First, the vacuum harrow dryer
The drying material is added from the middle of the vacuum rake dryer. Under the stirring of the continuously rotating rake teeth, the surface is continuously updated when the material contacts the housing wall, and the dried material is subject to steam (or hot water, thermal oil ) Indirect heating, but the material moisture is vaporized, and the vaporized moisture is pumped away by the vacuum pump in time. The dried material is indirectly heated by the heat carrier, so that the water in the material is vaporized, and the vaporized water is discharged by the vacuum pump in time. Due to the high operating vacuum, generally within the range of 400-700mmHg, the water vapor pressure on the surface of the material to be dried is much greater than the water vapor pressure in the evaporation space in the dryer housing. Therefore, it is beneficial for the drainage of the internal moisture and surface moisture of the material to be dried, and for the movement of water molecules of the material to be dried to achieve the purpose of drying. The vacuum harrow dryer is suitable for materials that are thermally sensitive, easily oxidized at high temperatures, or materials that tend to compact during drying, and materials that must be recovered from the steam discharged during drying. Typical dry materials are sodium propylene sulfonate, CMC, phthalocyanine blue, dye intermediates, carboxymethyl starch, maltodextrin, and anthraquinone sulfonic acid.
The belt dryer consists of several independent unit sections. Each unit segment includes a circulating fan, heating unit, separate or shared fresh air intake system and exhaust system. The operating parameters of the amount of drying medium, temperature, humidity and exhaust gas circulation can be independently controlled, so as to ensure the reliability of the dryer and optimize the operating conditions. With a dryer, the operation is flexible, the wet material is fed, and the drying process is performed in a completely sealed box. The working conditions are better, and the leakage of dust is avoided. It is used for drying sheet, strip and granular materials with good air permeability. It is especially suitable for materials with high water content such as dehydrated vegetables and Chinese medicine decoction pieces and the material temperature is not allowed to be high.
Third, the roller scraper dryer
The drum scraper dryer is a continuous operation device that uses a rotating cylinder to dry liquid-phase materials or strip-shaped materials attached to the outer wall of the cylinder in a thermally conductive manner. The material liquid to be dried flows from the high-level tank into the receiving tank of the drum dryer. Driven by the transmission device, the drying drum rotates at a specified speed. The material is formed by a film distribution device to form a material film on the wall of the drum. A heating medium is continuously introduced into the cylinder, the cylinder is heated, and the moisture of the material film is vaporized by heat transfer from the cylinder wall, and then the materials that meet the drying requirements are scraped off by a scraper, and then conveyed to the storage tank by a spiral for packaging. The moisture removed by evaporation can be introduced into the corresponding processing device through a closed cover depending on its nature; generally, water vapor can be directly released into the atmosphere through the exhaust pipe on the top of the cover. This machine is mainly used for processing liquid materials. It 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, immersion, spray, milling and auxiliary feeding methods can be used.
Four, hollow paddle dryer
Hollow blade dryers, also called blade dryers, are mainly composed of a W-shaped casing with a jacket, two hollow blade shafts and a transmission device. Hollow blades are arranged on the shaft, and a rotary joint for introducing a heat medium is installed at the shaft end. The heat required to dry the moisture is conducted to the material by the inner wall of the jacketed W-shaped groove and the hollow blade wall. During the drying of the material, the hollow shaft with hollow blades stirs the material while heating the material, thereby renewing the heating surface. It is a continuous conduction heating dryer. The heating medium is steam, hot water or thermal oil. The heating medium is introduced into the shell jacket and the two hollow blade shafts, and the materials are heated and dried by conduction heating. The hollow blade shaft structure of different materials is different.
This machine is suitable for processing all kinds of paste, granule, powder and other materials with good thermal stability. Under special conditions, it can also dry heat-sensitive materials and recover solvents during the drying process. Commonly used in the drying or cooling of carbon black, light calcium carbonate, titanium dioxide, barium carbonate, nitrile uric acid, gypsum, clay, manganese dioxide, nylon and polyester chips, polyethylene, polypropylene (recycled solvent) and other materials.
Five, double cone rotary vacuum dryer
The double-cone rotary vacuum dryer has a slightly olive-shaped body, with two ends covered, and two shafts in the middle to support the body. The device body has a jacket for heating, and the device body can be rotated during drying, so that the material and the device wall are often replaced and contacted, which overcomes the shortcomings of the material in the vacuum oven which mainly relies on the conduction of the heating cylinder and the thermal efficiency is low. Rotary vacuum dryers have been widely used in fine chemicals and medicine, and are not suitable for materials with high viscosity or strong adhesion during the rotation process. This equipment is mainly used for the concentration, mixing, drying and low temperature drying of powdery, granular and fibrous materials in the pharmaceutical, chemical, food and other industries (such as biochemical products). It is more suitable for easy oxidation, volatility and heat sensitivity. Drying of strongly irritating, toxic materials and materials that do not allow crystal damage.
Six, freeze dryer
The freeze-dryer first freezes and freezes the material liquid, and then decompresses the ice to obtain dry materials. Since the whole process is performed below the freezing point, it is often used for drying of heat-sensitive items. Due to the difficulty of heating the frozen materials under vacuum, and the need for a large refrigeration system to condense and sublimate water vapor under reduced pressure, the drying cost is large. Freeze the moisture in highly heat-sensitive materials and keep them below freezing temperature under high vacuum. Sublimate moisture to separate from material. There is less loss of effective ingredients in the material, but the drying rate is low.
Seven, vacuum oven
Since the decompression, the evaporation temperature of the volatiles contained in the material can be reduced, which is suitable for the drying of various heat-sensitive and easily oxidizable materials. This device is usually a cylinder or other housing that can be operated under vacuum. The electric heating or hot water and heat-conducting oil are used to supply heat through a heating plate or a heating tube, which is suitable for batch production in small batches.
The oven is a general-purpose drying equipment with a wide application area. It belongs to a disc-frame intermittent drying equipment and is used in pharmaceutical, chemical and food. Heat curing, drying and dehydration of materials and products in industries such as light industry and heavy industry. Such as raw materials, crude drugs, Chinese medicine pieces, extracts, powders, granules, granules, water pills, packaging bottles, pigments and dyes, dehydrated vegetables, dried fruits, sausages, plastic resins, electrical components, baking paint, etc.
The above seven categories can be said to have covered all the dryers. Of course, the product classification method will have more titles by different characteristics, but basic knowledge of the above is sufficient. For more information, please visit http: // www. .ylscps.com
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