First, the vacuum dryer The vacuum kneading dryer is a conductive heat transfer dryer. The material is not directly in contact with the heating medium, and is suitable for drying a small amount of mud-like or paste-like materials which are not resistant to high temperature and easy to be oxidized, and the water content is 15% to 90%. The blades of the horizontal jaw mixer in the dryer are made of cast iron or steel and are mounted on a square shaft with half of the blades to the left and the other half to the right. The shaft speed is 7~8r/min, which is driven by the motor with gearbox. At the same time, the automatic steering device is adopted to change the rotation direction of the shaft and change the rotation direction of the agitator every 5~8 minutes. In operation, first start the agitator, add the dried material, and close the feed port. At the same time, it is heated by steam, and the pressure of heating steam is generally 0.2~0.4Mpa (gauge pressure). The water vapor and the non-condensable gas are extracted by a vacuum pump, and when the material is generally dried, the degree of vacuum is about 700 mmHg. The moisture evaporation intensity of such a dryer varies depending on the nature of the material, humidity, heating steam pressure, and degree of vacuum. For example, when the degree of vacuum is 700 mmHg and the heating steam pressure is 0.2 MPa (gauge pressure), the potato starch is dried from 40% to 20% of the initial moisture, and the water evaporation intensity of the dryer is 5-7 kg/m2?h. The operation of the vacuum kneading dryer is lower than that of the box drier, and the useful moisture in the material can be recovered, the operating conditions are good, and the management is convenient. The disadvantage is that the production capacity is low, the structure of the device is relatively complicated, and the blades of the agitator are easily damaged. Such dryers are used more in the dye and pharmaceutical industries. For example, drying of a vat dye intermediate, an oxime sulfonic acid, a reduced olive green R, a salicylic acid intermediate, a Kupron polymer, a diamino hydrazine, and the like. The structure of the vacuum sputum dryer is shown in Figure 2-28. Figure 2-28 Schematic diagram of vacuum kneading dryer equipment 1 - outer casing; 2 - steam jacket; 3 - horizontal agitator; 4 - transmission Second, the plate dryer (1) Foreword The plate dryer is also called a tray dryer. It was introduced in the dry monograph published in Japan in the early years. In recent years, China's Shanghai, Shijiazhuang and other places have been successfully developed. It is a multi-layer fixed hollow heating disc (also known as a loading tray), which is developed on the basis of intermittently stirring and conducting the dryer, and has been comprehensively improved. Conductive-based drying unit. The drying process is to pass the heat carrier into the hollow disks of each layer, and indirectly heat the wet material contacted on the disk surface by means of heat conduction, and the wetness of the continuously moving material under the mechanical action of the rotary blade The fraction is evaporated at the operating temperature and its vapor is withdrawn from the plant exhaust to continuously obtain a qualified dry product at the bottom of the equipment. Plate dryers have been in development for decades. In recent years, many countries have applied it to the fields of chemicals, dyes, pesticides, plastics, medicine and food, and have continuously improved and improved in use. Compared with traditional drying equipment, it has the advantages of high thermal efficiency, energy saving, uniform drying, good product quality, small footprint, less auxiliary equipment, less pollution, continuous production, convenient operation and wide application range. Therefore, it has broad prospects for development in drying technology, which has attracted more and more people's attention and research. Equipment types and specifications have been serialized, industrialized and large-scale, and have been developed into an industrial drying device. (II) Equipment structure and operation mechanism Now only one of the types is taken as an example to illustrate its structure and operation principle. The equipment is mainly composed of a cylinder body and a frame, a hollow hollow heating plate, a main shaft, a cross arm and a rakes blade, a disc feeder, a hopper tray and a finished product outlet, an exhaust gas outlet, a heat carrier inlet and outlet pipe, an inspection door, a worm wheel reducer, A continuously variable transmission and a motor. The main component of the equipment is a hollow heating plate, and the hollow part is welded with a baffle plate to strengthen, which not only increases the rigidity and strength, but also improves the heat transfer effect, and exerts the advantage of high utilization rate of conduction drying heat energy. There are heat carrier inlet and outlet pipes on each layer of heating plate. Generally, the upper layers are made of low-pressure saturated steam or hot water, hot oil in series, parallel or series-parallel input heating to control the temperature of each layer; and the bottom two layers are connected to cooling water. To reduce product temperature, recover heat and ensure quality. The heating plate is fixed on the frame of the cylinder at a certain interval, and is placed horizontally. Each layer is equipped with a cross arm frame, and the upper and lower layers are staggered and fixed at 45° on the central spindle, and the worm wheel reducer and the continuously variable transmission are arranged. And the motor and other drives, slowly rotate at 0.6~3.7 (r/min). Each of the booms is provided with a plurality of detachable hoe-shaped rakes or flat squeegees arranged equidistantly. The 耙 leaf adopts hinged and reed oscillating structure, so that the bottom edge floats evenly on the disk surface, and the angle of the 耙 leaf can be adjusted arbitrarily according to the material properties to ensure that the material is continuously advancing on the disk surface. The material to be dried is continuously fed from the top disc feeder to the inner ring surface of the uppermost first heating layer of the equipment, and under the mechanical action of the rotary rakes, while tumbling and stirring, moving forward from the inside to the outside , the zigzag is covered on the entire surface of the disk, and is heated by contact; then the material falls from the outer edge to the outer surface of the outer layer of the second heating plate below, and is moved from the outside to the inside under the action of the reversely mounted raft leaves. To the inner edge, fall to the inner ring surface of the third heating plate. By analogy, the materials are moved layer by layer from top to bottom, and are continuously heated and dried. The evaporated moisture is mixed with the exhaust gas in the equipment and naturally discharged from the upper outlet. Finally, the dry material falls onto the lower tray, and is continuously discharged from the raking blade to the bottom discharge port to obtain a qualified dry product. According to product performance, drying requirements and processing capacity, the plate dryer adopts a series of steps such as stepless speed regulation of the spindle, manual adjustment of the height of the disc feeder to adjust the height of the heating plate, control of the temperature distribution of each layer of the heating plate, and final cooling and cooling. The superior performance of the plate dryer. See Figure 2-29 for a schematic diagram of the structure of the plate dryer. Figure 2-29 Schematic diagram of the equipment of the plate dryer 1 - feeder; 2 - exhaust port; 3 - spindle and rakes; 4 - heating plate; 5 - cylinder; 6 - discharge port; 7 - steam inlet; 8—condensed water outlet; 9—continuous speed changer Third, paddle dryer (I) Overview of the paddle dryer As early as in the 1970s, the development of the paddle dryer was carried out by the unit. The technical conditions and the designed hot shaft structure were too complicated, so they stopped halfway. With the reform and opening up of China and the continuous introduction of foreign equipment, the domestic information in this area has been increasing. Therefore, some units in China have developed it, and a series of models have been formed. The paddle dryer is a horizontal agitating dryer with heat conduction. Because the agitating blade is shaped like a paddle, the solid is called a paddle dryer, and the foreign is also called a trough dryer or a stirring dryer. The paddle dryer has been developed abroad for many years. At present, this model is represented by Nara Machinery Co., Ltd. of Japan Co., Ltd., and has developed two-axis and four-axis structures and more than 10 specifications. The paddle dryer is a two-axis (or four-axis) horizontal mixing and drying device. It was first developed by the former Federal Republic of Germany. After that, Japan introduced the technology and improved it. It developed two-axis and four-axis structures and more than ten specifications. The heat required for the drying of the device is indirectly heated by heat conduction, so that the drying process does not require or require a small amount of gas to carry away the moisture. This greatly reduces the heat loss caused by the gas and improves the heat utilization rate. It is an energy-saving drying device. It is suitable for the drying of granules and powder materials, and can also be dried for paste materials. (II) Equipment structure The structure of the double-shaft paddle dryer is shown in Figure 2-30. The jacketed end face is a W-shaped casing, an upper cover, two hollow shafts with blades, and end covers at both ends. It is composed of a rotary joint with a heat medium, a metal hose, and a transmission mechanism including a gear and a sprocket. The core of the device is two hollow shafts and hollow mixing blades welded to the shaft. The blade shape is a wedge-shaped hollow semicircle, which can pass through the heating medium. In addition to stirring, it is also the heat transfer body of the equipment. The two main heat transfer sides of the blade are inclined. Therefore, when the material is in contact with the inclined surface, the particles will quickly slide away from the inclined surface to make the heat transfer. The surface is constantly updated to enhance heat transfer. A scraper is provided at the bottom of the triangle of the blade to scrape the material deposited on the bottom of the shell to prevent a dead angle. The layout of the blade and the size of each part have certain requirements, and in addition to the blade in the feeding zone, drying zone and discharge zone, an auxiliary mechanism is also provided to ensure stable operation and uniform drying. In addition, the residence time can also be adjusted. The heating medium of the device can be either steam or hot oil or hot water, but the heat carrier has different phase states, and the hollow shaft structure is also different. When heated by steam, the hot shaft has a simple structure; when heated with hot water, the shaft structure is complicated, especially when it is necessary to consider the flow rate of the liquid in the tube. Large paddle drying equipment has a shaft diameter of about 500 mm, so sealing is a big problem. In the 1970s and 1980s, the sealing problems of the shafts were not well solved. In the operation, solid powders often leaked to the two end caps. Therefore, a discharge opening is usually provided at the bottom of the end cap to periodically remove the material from the end cap. This not only causes inconvenience to the operation, but also increases the wear of the shaft due to the leakage of dust, which affects the life of the equipment. In addition, for flammable and explosive gases, it is often necessary to provide a reverse blower at the seal to prevent leakage of flammable and explosive gases. For the sealing problem of large shafts, foreign countries have been better solved in recent years. There is basically no accumulation of material at the end cover, and there is no need for regular cleaning and back blowing. (3) Equipment performance and characteristics 1. It can be known from the structure of the equipment that the heat required for drying is indirectly heated by the jacket and the wall surface of the blade. Therefore, the drying process can use no or only a small amount of gas to carry the moisture fraction of the material evaporation, and the heat utilization rate can reach 80% to 90%. 2. The heat transfer surface of the device is composed of two parts: a blade and a wall surface, wherein the heat transfer surface of the blade occupies a large part, so the device has a compact structure, a large heat transfer surface per unit volume, and a small floor space, which can save investment costs. 3. The drying process uses less gas, has a lower flow rate, and less dust is carried away by the gas. Therefore, the gas dust is easily recovered after drying, and the recycling equipment is simple, saving equipment investment. For the drying process with solvent recovery, the solvent concentration in the gas can be increased, the solvent recovery equipment can be reduced or the process can be shortened. 4. Due to the special structure of the blade, the material is alternately squeezed and relaxed during the drying process, enhancing the drying. In addition, when the two blades are reversely rotated in a staggered manner, they have a self-cleaning action, and thus can be applied to viscous and paste materials. 5. The material retention rate in the dryer is very high, and the residence time is adjusted by the feeding rate, the rotation speed, the storage amount, etc., and is arbitrarily selected between several minutes and several hours, so that it is suitable for materials that are easy to dry and difficult to dry. In addition, although there are many stirring blades in the dryer, the material flows in the plug from the feeding port to the discharging port in the dryer, and the residence time is narrow, so the product is evenly dried. In addition, the mixing and mixing make the material violently turn, thereby obtaining a high heat transfer coefficient, generally reaching 120-350 W/m2 ? K, so the floor space and space are small, saving the capital cost of the plant. The amount of gas used in the drying process is small, the flow rate is low, and the amount of dust carried away by the gas is small, so that the gas dust is easily recovered after drying, and the recycling equipment is small in size, which can save equipment investment. For a drying process that requires recovery of the solvent, the solvent concentration can be greatly increased. The disadvantage of the paddle dryer is that the structure is complicated, the processing is difficult, and the design of the large dryer is difficult. (4) Dry material of the paddle dryer, alcohol residue, oxytetracycline residue, erythromycin residue, fly ash, skin powder, clay, kaolin, iron oxide yellow, magnesium trisilicate, alumina, H acid, Mycelium, nitroaniline, ***, chlordane, indigo, ASN resin, 1010 antioxidant, DM accelerator, and the like. Figure 2-30 Paddle dryer 1 - transmission; 2 - main engine; 3 - heater; 4 - cyclone separator; 5 - induced draft fan Fourth, 耙 dryer The rake dryer has been used in chemical production for more than 80 years. The rake dryer is suitable for drying heat sensitive or organic solvent-containing materials under vacuum conditions. It is characterized by low energy consumption and high thermal efficiency, which can reach more than 80%. It is easy to operate and has a wide range of adaptability. Although the jaw dryer is an older model, the structure and function of the jaw dryer are constantly being developed and are still one of the main drying equipment. In foreign countries, many large chemical plants still have a large number of rake dryers in use. (I) Main structure and process of the rake dryer The rake dryer mainly consists of a casing, a jacket, a stirrer and a transmission. The wet material is added by the feed port of the rake dryer, and the material is turned by the angle between the molar and the axis, and is also axially reciprocated and filled with the dryer (mainly the lower part). The heat carrier passes into the jacket and conducts heat through the walls of the vessel. The vaporized water vapor (or solvent) is separated from the material by a filter. After drying, the product is pushed out by the molars to the discharge port, which is an intermittent operation. (II) Performance of vacuum kneading dryer Vacuum kneading dryer uses steam jacket and hollow shaft molar to indirectly heat the material and exhaust it under high vacuum. Therefore, it is especially suitable for heat sensitive materials which are easy to oxidize at high temperature. Or materials that are prone to powder when dry (such as various dyes), and materials that must be recovered from steam that is removed during drying. The vacuum kneading dryer has a moisture content of up to 90% at the inlet of the dried material, and the lowest is only 15%. The material to be dried is slurried, creamy, granulated, powdery, or fibrous. The moisture content of these materials after drying is generally 0.1% or even lower. The material to be dried is added from above the casing. When the material is in contact with the wall of the casing and the molars under the stirring of the rotating teeth, the surface is continuously updated, and the dried object is indirectly heated by steam (or hot water, etc.). The material moisture is vaporized, and the vaporized water is pumped away by the vacuum pump in time. Due to the high degree of operating vacuum, generally in the range of 400~700mmHg, the water vapor pressure on the surface of the dried material is much larger than the water vapor pressure in the evaporation space in the drying shell, which is beneficial to the movement of the water molecules of the dried material. It is good for the drying of the internal moisture and surface moisture of the dried material. The steam jacket and the hollow shaft are used to heat the material, thus increasing the heat transfer area. The plain bearing housing is mounted directly on the arch caps at both ends. The arch cover is connected with the flange of the cylinder and is sealed with the main shaft, and the whole machine is compact. The gap between the hollow shaft and the inner wall of the cylinder is not more than 2 mm; in addition, the chain tube is hung on the hollow shaft tube to remove the accumulated material, thereby improving the heat transfer coefficient. There is a thermometer cannula on the inlet nozzle, and an olive-shaped manifold is welded on the spindle shaft tube, and the raft leaves are welded. When the main shaft rotates, the material enters from the middle feeding port of the upper part of the cylinder, and the rakes push the material to both ends. When reversing, the material is twisted from the two ends to the middle, and the cycle is repeated. The moisture is taken away from the vacuum pump interface of the feeding port. The dust (solution) entrained in the water is collected by the condenser and the trap, and the lower discharge port is discharged.