There are many types of drying equipment, but there are not many equipments that can directly dry the dye filter cake. In order to solve the problem of drying high-viscosity paste materials in the chemical industry, a rotary flash dryer was successfully developed in 1970. After two large structural improvements and stereotypes, the machine structure has the following advantages:
(1) The bottom of the drying chamber is provided with an inverted conical structure, so that the hot air circulation cross section is continuously expanded from the bottom to the top, the bottom gas velocity is high, and the upper gas velocity is low, so that the lower large particles and the upper small particles can be well fluidized. status. The inverted cone structure also shortens the length of the agitator shaft cantilever and increases operational reliability and stability. The bearing is located at the machine to avoid long-term work in the high temperature zone and prolong the service life;
(2) While the wet material is dispersed and pulverized by the stirring teeth, it is twisted toward the wall of the vessel and bonded to the inner wall. The top of the stirring tooth is provided with a scraper, which can scrape off the material adhering to the wall in time to prevent overheating;
(3) The upper part of the drying chamber is provided with a grading ring, and its function is mainly to separate the material with large or no granules from the qualified product, and block in the drying room, which can effectively ensure the moisture requirement of the product;
(4) Cold air protection at the entrance of the hot air at the bottom of the cone prevents the material from coming into contact with the high temperature air to cause overheating and deterioration;
(5) Continuous operation, feeding amount, hot air temperature, product fineness can be controlled within a certain range, thus ensuring various indicators of dry products;
(6) The equipment is compact in structure and small in floor space. It integrates drying, pulverization and grading. It is an optimized combination of fluidization technology, swirling technology, pulverization grading technology, spray technology and convection heat transfer technology, which greatly simplifies the production process and saves equipment investment and operation costs.
First, the basic process introduction
The basic process, the wet material from the previous process (such as filter cake) is directly put into the feeder. The screw feeder uses stepless speed change to send the wet material to the dryer for drying. Fresh air enters the air filter and is heated by direct or indirect heaters. The agitator at the bottom of the dryer rotates at a speed of about 200 rpm to 500 rpm to promote fluidization of the wet material. Mainly relying on the hot air entering the drying chamber from the annular gap of the air distributor for fluidization. The tail gas is taken away from the top of the red bean machine with powder, and discharged from the star discharger through the bag filter 5 .
Second, the description of the working process of the rotary flash dryer
How Rotary Flash Dryer Works
According to the structure of the rotary flash dryer, the working process can be divided into four stages: crushing, gas-solid mixing, drying, and grading. These four working processes are also not available at the same time by other dryers.
(1) Crushing Because the rotary flash dryer is mainly used for the drying of the paste-like material, the material is broken by the stirring blade and the high-speed airflow immediately after entering the dryer, maximally increasing the dispersion of the material and the wet material per unit volume. Surface area.
(2) Gas-solid hybrid rotary flash dryer generally uses air as the heat carrier, and whether it can effectively achieve gas-solid mixing is the main factor affecting the drying rate. The stirring paddle of the rotary flash dryer breaks up the material and produces a dispersion effect, and the air entering the dryer is also in a highly turbulent state, and the gas-solid mixing is quickly achieved. At the same time, the bulk material falls down under the force of gravity. Since the bottom of the dryer is an inverted cone structure, the velocity of the airflow is large, up to 60 m/s, which ensures that the bulk material is in a good fluidization state and is surrounded by hot air.
(3) After the material in the drying stage is pulverized, it is blown up by the hot air flowing from the bottom at high speed, forming a relatively stable fluidized bed in the drying chamber, and drying and transferring the heat and mass transfer between the material and the hot air. Part of the water evaporates at this stage. The material with high water content and small specific surface area has a high density and falls down in the drying chamber. Since the gas velocity at the bottom is high, the falling velocity is zero after the sedimentation reaches a certain position, and the gravity and the buoyancy are balanced at this time. After further crushing and drying, the buoyancy is greater than gravity, and the material begins to move upwards, and is discharged and dried by classification.
(4) Grading stage The classifier is a ring-shaped baffle installed in the lower part of the discharge port of the dryer. The material rises with the airflow. Due to the centrifugal force, the rotating radius of the large and dry materials is increased by the centrifugal force. When the radius of rotation is greater than the radius of the step ring, the material is blocked from the drying chamber until the requirements are met before the dryer can be discharged through the classifier. When the material is added to the dryer, it is in a fluidized state of rotation. After the mass is crushed, the diameter is rapidly reduced and the water is evaporated. The material is screwed up under the entrainment of the gas, and the smaller and dry material is in the inner ring, and the larger and damp material produces a centrifugal force greater in the outer layer near the wall. However, the large particles of the outer layer are continuously pulverized and dried, and the centrifugal force is also reduced to move toward the inner ring, and the gas is taken out when the water meets the requirements.
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