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ZPG-L vacuum ribbon rake dryer
Product Overview: Conventional vacuum rake dryers have many problems, including certain drawbacks in drying fine particles with good flow conditions a
Product details
The rake type vacuum dryer is a novel horizontal intermittent vacuum drying equipment, which has the characteristics of low drying temperature, high drying rate, energy saving, good equipment sealing, and easy solvent recovery. It is particularly suitable for materials that are not resistant to high temperatures, are prone to oxidation at high temperatures, or are prone to powder production during drying (such as various dyes), as well as drying operations that require the recovery of solvents or toxic gases in materials. It has the advantages of quality assurance and does not damage the inherent properties of materials, and is widely used in industries such as petrochemicals, food, medicine, and dyes.
The main contents of the research and development of the new vacuum rake dryer include screw type rake bars, baffle type jackets, special channel type hot shafts, and new sealing structures.
1、 New type of spiral belt rake bar
In chemical production, there are many fine particle materials with small resting angles. The existing rake bar structure of the plate cannot fully play a role in the mixing process of the materials, that is, it cannot continuously update the contact surface between the materials and the cylinder wall, resulting in uneven drying of the materials, wall sticking and coking, and material denaturation. For the concentrated drying of slurry materials with high moisture content, the rake bar structure also prevents the slurry closer to the inner wall from being quickly renewed, resulting in excessive local heating of the slurry and affecting the concentrated drying process of the material.
Vacuum rake dryers are commonly used for low-temperature drying, and the heating medium used is mainly hot water. Hot water is introduced into the jacket of a conventional vacuum rake dryer. If the flow rate is too low, it is easy to form a "short circuit" phenomenon inside the jacket, causing uneven heating of the jacket; If the flow rate is too high, although it can reduce the occurrence of "short circuit" phenomenon, it increases the power consumption of the hot water pump and also requires stricter sealing requirements for the hot water circulation pipeline. Adopting a folded jacket structure, hot water enters the jacket from the inlet and has a fixed flow channel. Therefore, regardless of the flow rate of the hot water, it can flow through every part of the jacket, ensuring uniform heating of the jacket; At the same time, it also increases the turbulence effect of hot water and improves heat transfer efficiency.
3、 Special channel type hot shaft
The shaft and rake teeth of the new vacuum rake dryer are hollow and can be filled with heating medium. Their surface can be used as a heat transfer surface. Therefore, the shaft and rake teeth are collectively referred to as the hot shaft (also known as the stirring shaft). For large vacuum rake dryers, the heat transfer area of the hot shaft accounts for more than 60% of the total heat transfer area, and its heat transfer effect directly affects the drying efficiency of the dryer. In order to improve the heat transfer efficiency of the hot shaft, a special heat medium flow channel was designed in the hot shaft, which greatly enhanced the heat transfer efficiency.
4、 New sealing structure
Packing seals have the advantages of heat resistance, pressure resistance, simple structure, reliable sealing, economy, and easy maintenance, so many dynamic seals use packing seals. However, in the vacuum rake dryer, a separate packing seal is prone to contamination caused by foreign objects mixed into the dried material. Therefore, a new double sealing structure has been developed between the end cover and the hot shaft, which not only avoids foreign objects from falling into the material, but also solves the problem of material leakage.
5、 Anti blocking dust collector
When using a vacuum rake dryer to dry powder, the air and water vapor need to be removed to leave the powder behind. The method of achieving gas-solid separation is to add a filter screen at the outlet. However, for ultrafine powder materials with small particle size, high porosity, and low density such as carbon black, the flying dried fine powder is prone to agglomerate or bridge the filter screen after absorbing water vapor, making it difficult for the vacuum pump to evacuate. The dryer cylinder gradually changes from negative pressure to positive pressure, causing the dryer to malfunction and easily leading to production accidents.
The anti blocking vacuum rake dryer directly connects the gas-solid separation and filtration device with the dryer cylinder, which not only has a compact structure, occupies a small space, is easy to use, and reduces fixed asset investment, but also is more conducive to product quality control because there is no need to collect products from two places, effectively solving the problem of dust clogging the filter screen during the drying process of ultrafine powder materials with small particle size, high porosity, and low density. At the same time, due to the fact that the blowback only automatically starts when the filter is clogged, energy consumption is reduced and production safety is ensured.
Advantages of the new vacuum rake dryer technology
(1) The new vacuum rake dryer has a good sealing structure, which can prevent air from leaking in and causing material oxidation;
(2) Equipped with a nitrogen filling device, it can promptly remove moisture, extend the constant speed drying time, and be used to relieve vacuum at the end of drying;
(3) Select a high vacuum unit and maintain high vacuum for a long time during the deceleration period to remove trace amounts of bound moisture;
(4) The design of the internal heating system has expanded the heat transfer area, improved the heat transfer method, and ensured uniform and stable heat transfer inside, shortening the drying time;
(5) The hollow heating spindle with screw connection can prevent material from sticking during the drying process, while expanding the specific surface area of the material and improving heat and mass transfer rates;
(6) The material selection and surface treatment of the vessel wall can prevent material corrosion and adhesion to the wall surface, which affects product performance and extends equipment life;
The stirring shaft of existing vacuum rake dryers generally adopts a rake arm with rake blade structure, which has certain drawbacks for drying fine particles with good flow state and concentrated drying of slurry materials with high moisture content. In general, the spindle and rake teeth do not have internal heating structures. Although some use hollow shafts and hollow rake teeth, the unreasonable design of the fluid flow channel structure results in low drying efficiency, which directly restricts the scale and enlargement of the equipment; Secondly, using a simple packing sealing structure will seriously affect product quality. Regarding these issues, through experimental research,Baide DryWe have developed a new type of high-efficiency vacuum rake dryer with excellent structure and performance, and its technology has reached contemporary standards.
The main contents of the research and development of the new vacuum rake dryer include screw type rake bars, baffle type jackets, special channel type hot shafts, and new sealing structures.
1、 New type of spiral belt rake bar
In chemical production, there are many fine particle materials with small resting angles. The existing rake bar structure of the plate cannot fully play a role in the mixing process of the materials, that is, it cannot continuously update the contact surface between the materials and the cylinder wall, resulting in uneven drying of the materials, wall sticking and coking, and material denaturation. For the concentrated drying of slurry materials with high moisture content, the rake bar structure also prevents the slurry closer to the inner wall from being quickly renewed, resulting in excessive local heating of the slurry and affecting the concentrated drying process of the material.
In response to the above drawbacks, Baide Drying has improved the main shaft mixing structure of the vacuum rake dryer, adopting a screw belt structure instead of the original mixing form of the rake rod and rake blade. The spiral belt mixing device consists of a main shaft, a rake rod inner spiral belt, and an outer spiral belt. The spiral directions of the two spiral belts are opposite. When the rotating shaft of the spiral belt rotates, the two spiral belts simultaneously stir the material up and down, and the inner and outer spiral belts also cause the material to move axially in opposite directions to each other. Therefore, the material forms an axial reciprocating motion in the mixing chamber. Due to the different turning radii of the outer edges of the two spiral belts, the stirring speed of the material is also different, which is conducive to the radial distribution and mixing of the material. The double helix structure has a strong mixing effect on materials, so in addition to its distribution effect, it also has a partial dispersing effect, which can break up clumped materials.
Vacuum rake dryers are commonly used for low-temperature drying, and the heating medium used is mainly hot water. Hot water is introduced into the jacket of a conventional vacuum rake dryer. If the flow rate is too low, it is easy to form a "short circuit" phenomenon inside the jacket, causing uneven heating of the jacket; If the flow rate is too high, although it can reduce the occurrence of "short circuit" phenomenon, it increases the power consumption of the hot water pump and also requires stricter sealing requirements for the hot water circulation pipeline. Adopting a folded jacket structure, hot water enters the jacket from the inlet and has a fixed flow channel. Therefore, regardless of the flow rate of the hot water, it can flow through every part of the jacket, ensuring uniform heating of the jacket; At the same time, it also increases the turbulence effect of hot water and improves heat transfer efficiency.
3、 Special channel type hot shaft
The shaft and rake teeth of the new vacuum rake dryer are hollow and can be filled with heating medium. Their surface can be used as a heat transfer surface. Therefore, the shaft and rake teeth are collectively referred to as the hot shaft (also known as the stirring shaft). For large vacuum rake dryers, the heat transfer area of the hot shaft accounts for more than 60% of the total heat transfer area, and its heat transfer effect directly affects the drying efficiency of the dryer. In order to improve the heat transfer efficiency of the hot shaft, a special heat medium flow channel was designed in the hot shaft, which greatly enhanced the heat transfer efficiency.
4、 New sealing structure
Packing seals have the advantages of heat resistance, pressure resistance, simple structure, reliable sealing, economy, and easy maintenance, so many dynamic seals use packing seals. However, in the vacuum rake dryer, a separate packing seal is prone to contamination caused by foreign objects mixed into the dried material. Therefore, a new double sealing structure has been developed between the end cover and the hot shaft, which not only avoids foreign objects from falling into the material, but also solves the problem of material leakage.
5、 Anti blocking dust collector
When using a vacuum rake dryer to dry powder, the air and water vapor need to be removed to leave the powder behind. The method of achieving gas-solid separation is to add a filter screen at the outlet. However, for ultrafine powder materials with small particle size, high porosity, and low density such as carbon black, the flying dried fine powder is prone to agglomerate or bridge the filter screen after absorbing water vapor, making it difficult for the vacuum pump to evacuate. The dryer cylinder gradually changes from negative pressure to positive pressure, causing the dryer to malfunction and easily leading to production accidents.
The anti blocking vacuum rake dryer directly connects the gas-solid separation and filtration device with the dryer cylinder, which not only has a compact structure, occupies a small space, is easy to use, and reduces fixed asset investment, but also is more conducive to product quality control because there is no need to collect products from two places, effectively solving the problem of dust clogging the filter screen during the drying process of ultrafine powder materials with small particle size, high porosity, and low density. At the same time, due to the fact that the blowback only automatically starts when the filter is clogged, energy consumption is reduced and production safety is ensured.
Advantages of the new vacuum rake dryer technology
(1) The new vacuum rake dryer has a good sealing structure, which can prevent air from leaking in and causing material oxidation;
(2) Equipped with a nitrogen filling device, it can promptly remove moisture, extend the constant speed drying time, and be used to relieve vacuum at the end of drying;
(3) Select a high vacuum unit and maintain high vacuum for a long time during the deceleration period to remove trace amounts of bound moisture;
(4) The design of the internal heating system has expanded the heat transfer area, improved the heat transfer method, and ensured uniform and stable heat transfer inside, shortening the drying time;
(5) The hollow heating spindle with screw connection can prevent material from sticking during the drying process, while expanding the specific surface area of the material and improving heat and mass transfer rates;
(6) The material selection and surface treatment of the vessel wall can prevent material corrosion and adhesion to the wall surface, which affects product performance and extends equipment life;
(7) The design of dust removal and condensation water devices can not only prevent the harm of powder to the vacuum pump in the later stage of drying, but also qualitatively observe the effluent process and understand the drying status.
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