In the production process of materials that are sensitive to heat, prone to decomposition, oxidation, and require solvent recovery, the dryer needs to work in a vacuum state to heat and stir the production materials, allowing them to fully react and complete the drying process. At the same time, the solvent recovery is completed, the vacuum is turned off, and the atmospheric pressure is restored before the materials can be discharged to meet the needs of the next production process. In the process of drying the above raw materials, the existing vacuum dryer mainly uses a vacuum rake dryer with saturated steam as the heat medium, and this dryer mainly has the following defects:
1. Cannot continuously evacuate and cannot continuously produce
The vacuum rake dryer is a circular cylinder with a steam jacket, and a rake shaft is arranged at the center of the cylinder. The main heat transfer interface of the dryer is the inner surface of the circular cylinder with a steam jacket. The entire process from feeding to discharging takes 6-8 hours, and only one batch of materials can be dried at a time, which cannot be produced continuously.
2. Small heat transfer area and low yield
Due to the solid rake shaft of the vacuum rake dryer, no heating medium can enter the interior, resulting in the heat transfer interface of the dryer being only the inner wall of the cylinder. Due to the large filling capacity of the material inside the dryer, which can only reach 70%, the heat transfer area of the dryer is small, the drying time is long, and the output is low.
Baide DryDevelop and design a vacuum disc blade continuous dryer to solve the problems of existing vacuum rake dryers not being able to continuously vacuum and produce, with small heat transfer area and low output.

Vacuum disc blade dryerProcess flowchart

Vacuum disc blade dryerEquipment structure
The shell of the vacuum disc blade dryer is composed of an inner wall and an outer jacket. The jacket is designed in a honeycomb shape, which means that many concave circular holes with inward flanges are regularly punched out on the jacket wall, and the flanges are welded to the inner wall to increase strength. The dryer shell is designed as a monolithic structure, with a manhole and sight glass at the top for easy observation and maintenance, while avoiding oxidation reactions caused by leakage from the narrow sealing surface of the dryer. The top dome structure design enhances the overall strength of the equipment.
The hollow hot shaft and hollow disc blade structure are key components of the slurry rotary disc dryer. The rotary indirect dryer has two hollow hot shafts, which rotate in opposite directions towards the centerline of the equipment. With the help of the auxiliary feeding plate on the blades, the material is pushed from the center to the wall, and then lifted upwards from the wall, crossing the hollow hot shaft and squeezed to the center of the equipment. For materials with strong abrasiveness, wear-resistant accessories need to be installed.

Vacuum disc blade dryerWorking principle
The material enters the dryer through the feeding port, and the honeycomb jacket and two hollow hot shafts of the dryer are both filled with heating medium. Through the heat conduction between the jacket wall and the hot shaft, the wet material is indirectly heated and dried; The dryer body tilts, with a tilt angle of 0.5-1.0 ° from the feed to the discharge as a whole. Solid materials gradually move towards the discharge port under the stirring of gravity, blades, and sheet materials. Under the continuous stirring of various scrapers, the wet material in the dryer constantly updates its heating interface, and is fully and uniformly heated after coming into contact with the inner wall of the cylinder and the heating disk. The large amount of steam generated during drying is pumped by the vacuum pump through the induced draft duct to the tube condenser, where it exchanges heat with the cooling circulating water in the heat exchange tube of the tube condenser. A large amount of exhaust gas releases heat and is converted into exhaust gas condensate, which is pumped out of the machine by the condensate pump and enters the sewage tank for centralized treatment.

Vacuum disc blade dryerDesign points
1. The propeller shaft is a hollow seamless thick walled tube, with a steam inlet at one end and a condensate outlet at the other end. Several propeller components are arranged in parallel on the shaft;
2. The blade assembly includes two identical hollow disc blades, which are welded in series on a hollow shaft. Each blade is equipped with a scraper on its outer surface, and a steam inlet pipe is provided inside the blade. Each steam inlet pipe is connected to the hollow shaft, and a condensate outlet pipe is provided at the position where each blade is connected to the hollow shaft, and each condensate outlet pipe is connected to the hollow shaft; The blade and scraper are perpendicular to each other. The end of the steam inlet pipe near the hollow shaft extends into the interior of the hollow shaft, while the end of the condensate outlet pipe near the blade does not extend into the interior of the blade;
3. The sealing structure set at both ends of the hollow shaft adopts a dual sealing form of packing seal and cylinder seal. In the sealing component, the packing seal is located near the end of the cylinder, and a cylinder is set at each of the left and right ends outside the packing cover. As the cylinder is always in working condition, it can continuously apply pressure to the packing, keeping the packing in a compressed state and keeping the interior of the cylinder in a vacuum state. It can eliminate the gap formed between the hollow shaft and the packing due to rotation, ensuring reliable sealing. This ensures the required vacuum level inside the vacuum disc blade dryer during operation. Since the equipment can only be fed in and out under normal pressure, it also guarantees the continuous production of the equipment, solving the problem of the existing vacuum rake dryer being unable to continuously vacuum and produce.
4. Two rows of concentric disc blades are evenly arranged on the hollow shaft of the vacuum disc blade dryer. The hollow shaft and blades are both hollow structures, and heating medium can be introduced into their interiors. Steam enters from the steam inlet end of the hollow shaft and then enters each blade through the steam inlet pipe. The condensed water in the blades is collected in the hollow shaft and discharged from its condensed water outlet. During this process, the material is heated in the vacuum continuous dryer due to the heat transferred by the blades and the inner wall of the cylinder, and is stirred under the rotation of the blades and the scraper on them before being discharged from the discharge port. Due to the fact that steam can be introduced into both the hollow shaft and the blade, the single shaft blade vacuum continuous dryer increases the heat transfer area per unit volume, shortens the drying time, increases output, and reduces production costs.
5. To solve the problem of continuous feeding and discharging of the dryer during continuous vacuum operation, the vacuum disc blade dryer is equipped with vacuum switching valves at the outlet of the feed and discharge ports to ensure that the feeding and discharging can only be carried out while maintaining a vacuum inside the equipment.

6. The vacuum disc blade dryer is equipped with a double end mechanical seal at the shaft end, which effectively solves the sealing problem of the blade main shaft. External air cannot enter the interior of the equipment, ensuring that the equipment maintains a continuous vacuum during continuous operation. This solves the problem of the existing vacuum rake dryer not being able to continuously vacuum and produce continuously; The tight welding of multiple hollow disks on the main shaft increases the heat transfer area of the equipment, shortens the drying time, and increases the output, solving the problem of small heat transfer area and low output of existing vacuum rake dryers.