overview

The blade dryer uses steam, hot water, or thermal oil as the heating medium, and the shaft end is equipped with a rotating joint for introducing and exporting the heat medium. The heating medium is divided into two paths, which enter the jacket of the dryer shell and the inner cavity of the blade shaft to heat the body and blade shaft simultaneously. The wet material is heated and dried by conduction heating. The dried wet material is continuously fed into the feeding port of the dryer by the screw feeder. The wet material enters behind the dryer and is flipped and stirred by the rotation of the blade, constantly updating the heating interface. It comes into contact with the body and blade, and is fully heated to evaporate the surface moisture contained in the sludge. At the same time, the wet material is transported in a spiral trajectory towards the discharge port by the rotation of the blade shaft. During the transportation, it continues to stir, allowing the moisture seeping out of the wet material to continue evaporating. Finally, the uniformly dried qualified product is discharged from the discharge port.

During the drying process of the closed-loop rotary blade dryer, if the wet component of the material is solvent or water, it can be recovered. The water and solvent evaporated during drying are separated by a cyclone separator to remove dust, and then sprayed by a multi-stage spray tower. After spraying, the water or solvent is condensed by a condenser and discharged. The exhaust gas still enters the dryer for circulation. Circulating gas can be air or inert gas. The entire drying process is carried out in a closed environment, with the characteristics of no dust and no exhaust emissions.

Characteristics of closed-loop circulation blade dryer equipment

1. The equipment has a compact structure, with a large heat transfer surface per unit volume and a small footprint;

2. The heat utilization rate is high, and the blade type sludge dryer uses conduction heating for heating, with a heat utilization rate of over 90%;

3. The wedge-shaped blade has self-cleaning ability, which compresses and expands the material during rotation, enhancing the heat transfer effect;

4. The gas flow rate inside the dryer is low, resulting in less dust carried out by the gas. After drying, the recovery of gas and dust in the system is convenient, and the scale of tail gas treatment equipment can be reduced, saving equipment investment;

5. Preheat the drying system by introducing air from the circulating fan and preheater into the dryer until the exhaust temperature exceeds 70-80 ℃; Using a condenser to condense the moisture content of exhaust gas to achieve closed-loop circulation,. Realize rapid material processing and no exhaust gas discharge, with a simple structure, energy saving and environmental protection;

6. Due to the partial nitrogen filling inside the closed drying system, there is no combustion or oxidation reaction of this gas, achieving an environmentally friendly and emission free closed-loop blade dryer.

Process flow diagram of closed-loop circulation blade dryer

Optimization design of closed-loop circulating blade dryer

1. Improvement design of condensate discharge system inside the propeller shaft

Based on the characteristic of high dehydration of wet materials, the condensate drainage system inside the blade shaft is improved and designed by adding a device inside the blade to increase the drainage time during blade rotation; Increase the condensate drainage pipe to increase the drainage volume of condensate water. Improve the structure of the original siphon tube to ensure more thorough discharge of condensed water, thereby increasing production.

2. Modification of the external structure of the blade

Some wet materials have high viscosity and poor flowability. In order to make these materials flow forward, when installing a regular blade dryer, the equipment is tilted towards the discharge port at a certain angle. However, when the equipment is tilted, it is difficult to control the flow speed of the material, making it difficult to control the drying moisture of the material. In order to improve the flowability of wet materials inside the blade dryer, the external structure of the blade has been modified to give the blade a forward pushing effect on the material. By changing the rotational speed of the blade shaft, the pushing speed of the material can be controlled to achieve a reasonable pushing speed, maintain a reasonable material level inside the equipment, and ensure full contact between the material and the blade surface, further improving the heat transfer area.

3. Add some devices inside the cylinder

When dried to a moisture content of around 60%, the material is prone to clumping, has a hard surface, and is difficult to break, while the inside is still in the form of a filter cake, which poses great difficulties for further drying of similar materials; On the other hand, during the process of drying similar materials, the materials are prone to gripping the shaft, causing the blades and the heat dissipation surface of the shaft to move together when rotating, resulting in a relatively poor drying effect. In order to overcome this difficulty, we have made improvements to the dryer by adding some devices inside the cylinder to make the agglomerated material easy to break, thereby greatly improving the drying speed.

4. Reduce system exhaust emissions
The blade dryer belongs to a typical conduction type dryer, and its heat transfer and evaporation are achieved by the hot wall rather than gas convection. The function of the exhaust gas is to timely remove the steam generated during the drying process from the dryer. Preheating the closed drying system through a circulating fan and a reheating mechanism, using a multi-stage spray and multi-stage condenser condensation method to reduce the system's exhaust volume, achieve rapid material processing, have a simple structure, and are energy-saving and environmentally friendly.