Fluidized bed drying equipment is a mechanical device that uses fluidization technology to physically or chemically process fluids or solid particles, such as drying, leaching, adsorption and ion exchange, particle mixing, and the like. Fluidized bed drying equipment is widely used in chemical, food, ceramic, pharmaceutical and other industries due to its high heat transfer rate, compact structure and easy operation. Fluidization technology originated in 1921, and was first applied to dry industrialization. It was the Dole-Oleph solid fluidization unit established in the United States in 1948, and it was not until 1958 that China began to develop this technology. During the fluidized bed drying process, the bulk material is placed on the orifice plate, and the lower part conveys the gas, so that the material particles are in a suspended state, just like the liquid boils, so that the material particles are in full contact with the gas, and rapid heat transfer and moisture transfer are performed. Fluidized drying has been widely developed and applied due to its advantages of good heat transfer effect, uniform temperature distribution, diverse operation modes, adjustable material residence time, low investment cost and small maintenance workload. Before the reform and opening up, China basically had no formal industrial production. Individual production enterprises, design institutes, universities and colleges designed and produced some cylindrical or horizontal multi-chamber fluidized beds, and they began to contact vibration. Fluidized bed and fluidized bed of inert particles. According to incomplete survey results, by 1971, there were more than 40 enterprises using fluidized beds in the country, which were distributed in the chemical, light industry, pharmaceutical and other industries. The materials involved were PTFE, polyester granules and chlorine. Dozens of ammonium, sodium salicylate, anhydrous sodium sulfite, aminopyrine, oxytetracycline, and catalysts. However, due to the limited level of domestic specialized production at that time, the promotion of new technologies could only be carried out in a small scale within the industry, and the speed and scale of development were limited.
In the early days of reform and opening up, the state advocated the introduction of advanced technology, domestic chemical, pharmaceutical, food and other industries, and introduced a large number of fluidized bed dryers representing the advanced level of the world, such as the spray + vibrating fluidized bed introduced by Heilongjiang Anda Dairy Factory. Stage drying system, multi-chamber fluidized bed and airflow + fluidized bed two-stage drying device introduced by Liaoyang Petrochemical, Yanshan Petrochemical, Qilu Petrochemical, etc., vibrating fluidized bed introduced by Hubei Yingcheng Salt Mine and Tianjin Soda Plant, introduction of Yingkou Salt Field The internal heat fluidized bed, the fluidized bed granulation drying equipment introduced by Beijing Pharmaceutical Factory, and the stirred fluidized bed introduced by Jilin Panshi Pesticide Factory. The introduction of these advanced equipment has greatly broadened the horizon of the domestic drying industry and promoted the innovation of products. At the same time, some enterprises in the domestic drying industry have also taken measures such as introduction, horizontal integration, digestion and absorption to increase the intensity of new product development. In 1982, Tieling Seiko Machinery Factory cooperated with Northeast Institute of Technology (now Northeastern University) to develop a vibrating fluidized bed dryer. The domestic company took the lead in commercializing this advanced technology and was well received by users. The market potential is huge. At the beginning of the reform and opening up, there were only a dozen research institutes and colleges and universities that were interested in drying technology in China, and there were few professional production plants.
The rapid development of pharmaceutical production technology has led to the unprecedented prosperity of pharmaceutical machinery, and the product technology of medicinal fluidized bed drying equipment has also risen. Due to the inherent advantages of fluidized bed drying and the continuous improvement and improvement of equipment technology, it has been more and more popularized and applied in the pharmaceutical process, but its application has certain limitations, such as: drying The granularity of the material is relatively strict. The particle size is too small to be entrained by the gas stream. The particle size is too large to be fluidized. When several materials are mixed together, the relative density of several materials should be close to each other; generally, the water content is too high. Easy to agglomerate materials, otherwise it is prone to walling or bed-breaking, and so on. However, fluidized bed drying equipment has been increasingly recognized for its excellent performance, and its widespread use in pharmaceutical production is not surprising.
By the end of 1990, the research units engaged in drying technology had been specialized in chemical engineering at various universities, and there were more than 20 production companies. In the past 10 years, with the continuous development of the national economy, the drying technology has also made great progress. Professional production enterprises have also increased by more than 10 times to more than 300. At present, almost all conventional fluidized bed dryers can be produced domestically.
Working principle and structure of vibrating fluidized bed dryer
The wet material entering the fluidized bed is in contact with the hot air above the air distribution plate, and the material particles are suspended in the air flow to form a fluidized state. The material particles in the fluidized state are uniformly and thoroughly mixed with the hot air, and the heat transfer and mass transfer are performed very strongly, and the moisture is removed to achieve drying. The qualified product is discharged from the discharge port of the fluidized bed, and the dust-containing gas is purified by the dust removing device and discharged into the atmosphere by the induced draft fan.
When the granular material is dried in a common fluidized bed dryer, the material particles should be uniform and have certain specifications, otherwise the groove flow and the stagnation zone will be formed. When the particle size distribution is wide, the entrainment is serious, and the moisture is easy to agglomerate when the humidity is large. And because of the particle back-mixing, the particle residence time distribution range is large, and the particle moisture content is uneven, thus limiting the use range of the ordinary fluidized bed dryer. In order to overcome its shortcomings, a lot of research has been done abroad to improve the performance of fluidized bed dryers. Especially in today's energy shortage, the mass transfer heat transfer process is strengthened, energy conservation and quality are improved, and the fluidized bed dryer has wide adaptability and economic rationality. The vibrating fluidized bed dryer has great significance. The vibrating fluidized bed dryer has the advantages of advanced design, reliable quality, wide application range, remarkable energy conservation and the ability to dry materials that are difficult to dry on other dryers. Therefore, the vibrating fluidized bed dryer is widely welcomed by various industries.
The vibrating fluidized bed dryer is driven by a vibration motor to vibrate the machine, and the material jumps forward under the action of the exciting force in a given direction, while the vibrating fluidized bed dries the hot air input at the bottom of the machine to make the material fluid. In the state, the material particles are in full contact with the hot air to achieve the desired drying effect. The material enters from the mouth of the vibrating fluidized bed dryer. The material on the vibrating bed of the vibrating fluidized bed dryer is in orthogonal contact with the hot air passing through the lower part of the vibrating trough. The humid air is led out by the induced air, and the dry material is discharged from the discharge port. discharge.
Main features of vibrating fluidized bed dryer
1. Vibrating fluidized bed dryer is driven by vibration motor, which has stable operation, low noise, long service life and convenient maintenance.
2. The vibration of the vibrating fluidized bed dryer makes the material easy to reach the fluidized state and increases the effective heat transfer coefficient, so the thermal efficiency is high. The bed temperature distribution is uniform and there is no local overheating. Uniform fluidization, no dead angles and blow through. Vibration plays a role in transportation and is also conducive to energy conservation. It can save 30-60% energy compared to general drying equipment.
3. The thickness of the material layer and the moving speed and amplitude of the machine can be adjusted steplessly. The adjustability is good and the speed is wide.
4, the material surface damage is small, can be used for the drying of fragile materials, material particles can also be used when irregular, does not affect the effect.
5. The vibrating fluidized bed dryer adopts a fully enclosed structure, which effectively prevents cross-contamination of materials from the outside, cleans the environment and improves working conditions.
6. The vibration promotes fluidization, which reduces the air demand and reduces the entrainment rate of the particles.
Fluidized bed dryer classification for applicable materials
In less than 100 years, fluidized bed drying equipment has been greatly developed and widely used by researchers through continuous improvement and innovation. There are many types, and the fluidized bed used is different depending on the nature of the material to be dried. According to its structure, it can be roughly divided into: single-layer and multi-layer cylindrical fluidized type, horizontal multi-chamber fluidized type, and stirred. Fluidization type, vibration fluidization type, centrifugal fluidization type, pulse fluidization type, etc. With the continuous development of the application technology of fluidized bed drying equipment, its types and materials are more and more suitable, and it has been widely used in chemical, light industry, medicine, food and other industries. Due to the different requirements of different materials and products for drying, different forms of fluidized bed dryers have emerged. According to its type, it is described as follows:
1. Single layer fluidized bed dryer
The single-layer fluidized bed dryer is the simplest type of machine and can be divided into continuous and intermittent operation methods. The continuous operation residence time is widely distributed, so it is often applied to products that are relatively easy to dry or products that are not very strict with drying specifications. Intermittent operation can be used for the drying of materials with high water content. For some materials with uneven graininess and certain viscosity, a low bed operation with a stirrer in the bed is often used.
The device is simple in operation, convenient in maintenance, stable in bed temperature, good in drying effect, but long in operation cycle.
This machine is suitable for drying of ammonium sulfate, ammonium chloride, anhydrous sodium sulfite, polytetrafluoroethylene, calcium gluconate, basic Qinglian dye, catalyst particles, anhydride casein, coconut, salt and other materials.
2. Multi-layer fluidized bed dryer
Since the multi-layer fluidized bed dryer has a uniform distribution of residence time, the actual drying time required is shorter than that of a single-layer fluidized bed. It can improve the uniformity of water content of dry products and easily control the dry quality of products. However, due to the increased number of layers in the multi-layer fluidized bed dryer, the formation of a stable fluidization state between the layers increases the annual complexity of the equipment structure. For the removal of moisture-bound materials, it is appropriate to use a multi-layer fluidized bed.
Multi-layer fluidized bed dryer is suitable for drying of polyester pellets, sodium salicylate, aminopyrine, oxytetracycline, chlortetracycline, tetracycline, tablet starch granules, powdered sugar, feed, plastic, grain and other granular materials.
3. Horizontal multi-chamber fluidized bed dryer
The horizontal multi-chamber fluidized bed drying equipment overcomes the complicated structure of the multi-layer fluidized bed, the resistance of the bed bed, etc. The wet material is continuously added to the first chamber of the dryer by the feeder, and since the material is in a fluidized state, it can be freely The first room is back to the next room. The dried material is discharged from the discharge port of the final drying chamber, and various granular materials and heat sensitive materials which are difficult to dry can be dried and gradually extended to powdery materials.
This kind of dryer is suitable for polyvinyl chloride resin, polypropylene resin, nylon 1010, o-chlorobenzoic acid, tetracycline, oxytetracycline, chloramphenicol, liver powder, powdered sugar, citric acid, oxalic acid, chlorinated rubber and other materials. dry.
Fluidized bed drying equipment has been widely used in chemical materials, light industry, medicine, food, plastics, grain and oil, slag, salt, tobacco and other industries, granular materials, powder materials, bulk materials, fibrous materials, The drying, cooling and humidification of special shaped materials are also used for drying, cooling and cooling humidification.
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