1.1 type and structure
Fluidized bed dryers generally have two major categories:
One type is horizontal rectangular and vertical circular motors driven directly on a fluidized bed, characterized by a simple fluidized bed structure, easy installation, and low cost;
The other type is the plate spring type in which the vibrator is separated from the motor and fixed at one end of the fluidized bed. The vibration and transmission mechanism is complex and the cost is high. It is generally used in large-scale fluidized-bed dryers, and the operation is stable. Fluidized state.
The current horizontal selection of the rubber industry horizontal rectangular vibration fluidized bed
Dryer. Horizontal rectangular vibration fluidized bed dryer structure shown in Figure 1. It consists of the housing, distribution plate, vibrator (including vibration motor and vibration isolation spring) and hot air and cold air system. The vibrator generally includes two counter-rotating eccentric motors, which are called self-synchronizing two-axis inertial linear vibrators. Hot air enters through the perforated distribution plate from the bottom up, and the material enters from above the back. The material is fluidized in the fluidized bed by hot air and vibration. At the same time, heat and mass exchange occurs. The dried material is cooled and transported by vibration. To the discharge port, cold, hot air from the upper part of the exhaust outlet.
1.2 Features
Ordinary fluidized bed in the dry particulate material, the following problems may occur: When the smaller particle size to form a ditch flow or die bed, the particle distribution of a large range of entrapment will be quite serious; due to the anti-mixing of particles, the material in the machine retention Different times, the particles after drying have uneven water content; When the humidity of the material is large, agglomeration and agglomeration may occur to deteriorate the fluidization. The vibrating fluidized bed is made by applying vibration in a common fluidized bed, and is a successful modified type of the ordinary fluidized bed, which overcomes the above-mentioned insufficiency of the ordinary fluidized bed. Compared with the ordinary fluidized bed dryer, vibrating fluidized bed has the following advantages:
(1) In the ordinary fluidized bed, the fluidization of the material is completely realized by the air flow, and the fluidization and the transport in the vibrating fluidized bed are mainly performed by vibration. The material exhibits an ideal fluidization state under the double action of exciting force and hot air with a certain pressure, so that the material is in full contact with the hot air.
(2) Due to the addition of vibration, the minimum fluidizing velocity of the material is reduced and the fluidization phenomenon occurs earlier. In particular, the particulate material close to the bottom of the gas distribution plate begins to fluidize first, which helps to eliminate the wall phenomenon and improve the fluidization quality .
(3) hot air entering the dryer is mainly used for heat and mass transfer in the drying process. Using a higher inlet air temperature, increasing the material thickness, you can get a higher thermal efficiency. General thermal vibration of the fluidized bed dryer in the 30% to 60% efficiency. Therefore, greatly reduce the air volume, only ordinary fluidized bed dryer gas volume 20% to 30%. The load of the powder recovery system is reduced, and the phenomenon of fine powder entrainment is generally reduced. Supporting the heat, fans, cyclones and other specifications are also reduced accordingly, significant energy-saving effect.
(4) The vibrating fluidized bed can dry the material with wider particle distribution and has a more uniform residence time. It can also dry materials with viscosity or thermoplasticity to reduce the requirement of material uniformity and regularity, and obtain uniform and dry products easily.
(5) The bed structure is improved, the heat transfer coefficient is increased, the phase boundary area is increased, and the degree of turbulence in the boundary layer is increased, and the drying process is strengthened.
(6) The initial channeling problem of fluidization can be reduced, the operational stability is good, and the operating gas velocity and bed pressure drop are lower than those of a conventional fluidized bed dryer. Because there is no intense backmixing, damage to the material particles is small.
