Brief analysis on equipment improvement of vacuum rake dryer

There are many problems in the structure of conventional rake vacuum dryers. Generally, neither the shaft nor the rake teeth have internal heating structures. Although some use hollow shafts and hollow rake teeth, due to the unreasonable design of the fluid flow channel structure, the drying efficiency is low, which directly restricts the scale and enlargement of the equipment; secondly, the use of a simple packing seal structure will seriously affect the product quality. In response to these problems, through experimental research, our technicians have developed a new rake vacuum dryer with excellent structure and performance. Its technical level has reached the contemporary international level. The main contents of the research and development of the new rake vacuum dryer include a baffle type jacket, a special flow channel type hot shaft and a new sealing structure.

Working principle of rake vacuum dryer:
 The rake vacuum dryer is mainly composed of a stirring shaft, cylinder, transmission system and sealing device. The heat required for drying is mainly provided by the stirring shaft and cylinder jacket. When the heating medium is introduced into the equipment, the heat is indirectly heated through the jacket and the stirring shaft. The moisture in the wet material is heated and vaporized, and the vaporized moisture is promptly removed by the vacuum system. With the continuous rotation of the stirring shaft, the contact between the material and the heating surface is constantly updated, so that the material is heated evenly, thereby achieving a good drying effect.

The new rake vacuum dryer mainly improves the baffle type jacket inside the dryer, the special flow channel type hot shaft, and the sealing structure.

(1) Baffle type jacket
 Rake vacuum dryers are mostly used in low-temperature drying, and the heating medium used is mainly hot water. Hot water flows into the jacket of a conventional vacuum rake dryer. If the flow rate is too small, it is easy to form a "short circuit" phenomenon in the jacket, resulting in uneven heating of the jacket. If the flow rate is too high, although the "short circuit" phenomenon can be reduced, the power consumption of the hot water pump is increased, and the sealing requirements for the hot water circulation pipeline are also stricter. The baffle-type jacket structure is adopted. After the hot water enters the jacket from the inlet, due to the fixed flow channel, the hot water can flow through every part of the jacket regardless of the flow rate of the hot water, so that the jacket is evenly heated. At the same time, the turbulent flow effect of the hot water is increased and the heat transfer efficiency is improved. 
 (2) Special flow channel type hot axis
The shaft and rake teeth of the new rake vacuum dryer are hollow and can pass into the heating medium, and their surface can be used as a heat transfer surface. Therefore, the shaft and rake teeth are collectively called the hot axis (also known as the stirring shaft).  
For large rake vacuum 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 effect of the hot shaft, a special heat medium flow channel is designed in the hot shaft, thereby greatly enhancing the heat transfer.  
　　  
 (3) New sealing structure
Packing seals have the advantages of heat resistance, pressure resistance, simple structure, reliable sealing, economy, and easy maintenance. Therefore, many dynamic seals use packing seals. However, in a vacuum rake dryer, a separate packing seal can easily cause foreign matter to be mixed into the dried material, causing contamination. Therefore, a new double-seal structure has been developed between the end cover and the hot shaft, which not only prevents foreign matter from falling into the material, but also solves the problem of material leakage.