Application of the hottest conduction heat transfe

2022-08-21
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Application of conduction heat transfer drying equipment in pharmaceutical industry

conduction drying method indirectly transfers the heat required for drying through metal surfaces. The drying rate is lower than that of direct drying. During constant rate drying, the product temperature has nothing to do with the temperature of the heating source, which is roughly the same as the saturation temperature of the gas pressure in the device. In order to improve the drying rate and prevent uneven drying, mechanical stirring or rotating the container itself is usually used to increase or constantly update the heat transfer surface of materials. Therefore, it is necessary for Vittorio Pellegrini, director of IIT graphene laboratory and chairman of the administrative committee of graphene flagship company (VIT hopes to bring help to you). Torio Pellegrini said that it is necessary to further study the adhesion of heat transfer mechanisms. The drying device itself is expensive, but its characteristics are that the load of the dust collection system is small, the thermal efficiency is high, the solvent is easy to recover, and the total cost is much cheaper than the direct drying method

(1) belt dryer

belt dryer is composed of several independent unit sections. Each unit section includes circulating fan, heating device, separate or public fresh air suction system and tail gas discharge system. The operating parameters of drying medium quantity, temperature, humidity and tail gas circulation can be controlled independently, so as to ensure the reliability of the belt dryer and the optimization of operating conditions for everyone to understand. The belt dryer operates flexibly, the wet material is fed, and the drying process is carried out in a completely sealed box. The working conditions are good, avoiding the leakage of dust. It is used for drying flaky, strip and granular materials with good air permeability. It is particularly suitable for dehydrated vegetables, Chinese herbal medicine slices and other materials with high water content and high material temperature

(2) drum scraper dryer

drum scraper dryer is a continuous operation equipment that dries the liquid phase materials or ribbon materials attached to the outer wall of the cylinder by means of heat conduction through a rotating cylinder. The feed liquid to be dried flows into the receiving tank of the drum dryer from the high-level tank. Driven by the transmission device, the drying drum rotates at the specified speed. The material is formed on the wall of the drum by the film distribution device. The heating medium is continuously introduced into the cylinder, the cylinder is heated, the moisture of the material film is vaporized by the heat transfer of the cylinder wall, and then the materials that meet the drying requirements are scraped off by the scraper, and are transported to the storage tank through the screw for packaging. The moisture removed by evaporation can be introduced into the corresponding treatment device through a closed cover depending on its nature; Generally, it is water vapor, which can be directly discharged into the atmosphere through the exhaust pipe on the top of the hood. The 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, roller assisted and other feeding methods can be adopted

(3) hollow blade dryer (blade dryer)

hollow blade dryer, also known as blade dryer, is mainly composed of W-shaped shell with jacket, two hollow blade shafts and transmission devices. Hollow blades are arranged on the shaft, and the shaft end is equipped with a rotary joint for the introduction of thermal medium. The heat required for drying water is transmitted to the material by the inner wall of the W-shaped groove with jacket and the hollow blade wall. During the drying process of materials, the hollow shaft with hollow blades heats the materials while stirring the materials, so as to update the heating surface. It is a continuous conduction heating dryer. The heating medium is steam, hot water or heat transfer oil. The heating medium is introduced into the jacket of the shell and two hollow paddle shafts, and the materials are heated and dried by means of conduction heating. The structure of hollow paddle shafts of different materials is different

this machine is suitable for processing all kinds of paste, granular, powder and other materials with good thermal stability. Under special conditions, it can also dry heat sensitive materials and recover solvents in the drying process. It is commonly used for drying or cooling carbon black, light calcium carbonate, titanium dioxide, barium carbonate, cyanuric acid, gypsum, clay, manganese dioxide, nylon and polyester chips, polyethylene, polypropylene (recycled solvent) and other materials

(4) vacuum rake dryer

dry materials are added from the middle of the shell of the vacuum rake dryer. Under the stirring of the constantly rotating rake teeth, when the materials contact the shell wall, the surface is constantly updated, and the dried materials are heated by steam (or hot water, heat transfer oil), but the moisture of the materials vaporizes, and the vaporized moisture is pumped out by the vacuum pump in time. The dried material is indirectly heated by the heat carrier, so that the water in the material vaporizes, and the vaporized water is discharged in time by the vacuum pump

due to the high operating vacuum, generally in the range of 400 ~ 700mmhg, the water vapor pressure on the surface of the dried material is much greater than the water vapor pressure in the evaporation space in the dryer shell. Thus, it is conducive to the discharge of internal water and surface water of the dried material, and is conducive to the movement of water molecules of the dried material, so as to achieve the purpose of drying. The vacuum rake dryer is applicable to materials that are heat sensitive and easy to oxidize under high temperature or harden during drying, as well as materials that need to be recovered from the steam discharged during drying. Typical dry materials include sodium propene sulfonate, CMC, phthalocyanine blue, dye intermediates, carboxymethyl starch, maltodextrin, anthraquinone sulfonic acid, etc

(5) double cone rotary vacuum dryer

the double cone rotary vacuum dryer body is slightly olive shaped, with covers at both ends, and two shafts are set in the middle to support the body. The body is jacketed for heating, and the body can rotate during drying, so that the materials are often replaced and contacted with the wall, which overcomes the defect of low thermal efficiency in the vacuum oven because the materials are mainly transmitted by the heating cylinder. Rotary vacuum dryers have been widely used in fine chemicals, medicine, etc., and are not suitable for materials with high viscosity or strong adhesion in the process of rotation. The equipment is mainly used for the concentration, mixing and drying of powdery, granular and fibrous materials in the pharmaceutical, chemical, food and other industries, and materials that need low-temperature drying (such as biochemical products), and is more suitable for the drying of materials that are easy to oxidize, volatile, strongly stimulated by heat sensitivity, toxic materials and materials that are not allowed to damage crystals

(6) vacuum oven

after decompression, the evaporation temperature of volatile matter contained in material evaporation can be reduced, which is suitable for the drying of various heat sensitive and oxide prone materials. This device is usually a cylindrical shell or other shell that can bear vacuum operation. It uses electric heat or hot water and heat transfer oil to supply heat through heating plates or heating tubes. It is suitable for small batch intermittent production

oven is a general-purpose drying equipment with a wide range of applications. It is a tray type intermittent drying equipment, which is used in pharmaceutical, chemical and food industries. Heating, curing, drying and dehydration of materials and products in light industry, heavy industry and other industries. Such as bulk drugs, crude drugs, herbal pieces, extracts, powders, granules, granules, water pills, packaging bottles, pigments and dyes, dehydrated vegetables, dried fruits and melons, sausages, plastic resins, electrical components, baking paint, etc

(7) freeze dryer

freeze dryer is to cool and freeze the feed liquid first, and then reduce the pressure to sublimate the ice to obtain dry materials. Because the whole process is carried out below the freezing point, it is often used for the drying of thermal sensitive articles. Because it is difficult to heat the frozen materials under vacuum, and the condensing and sublimating steam under reduced pressure requires a large refrigeration system, the drying cost is large. Freeze the moisture in the highly heat sensitive material and keep it below the freezing point under high vacuum. It sublimates moisture and separates it from materials. It has first-rate technology and good reputation in the industry. The loss of active ingredients in the material is less, but the drying rate is low

the above are the basic types of several common drying devices. We can carry out variant development on the basis of the original basic model according to the specific requirements of users and material drying process

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