Double cone rotary vacuum dryer

The following is an introduction to the structure, working principle, operating procedures, common faults and solutions of the double cone rotary vacuum dryer. Structure of the double cone rotary vacuum dryer The double cone rotary vacuum dryer is a drying equipment that integrates mixing and vacuum drying. The double cone rotary vacuum dryer system is mainly composed of a double cone rotary vacuum dryer, a condenser, a vacuum system, a heating system, a cooling system, an electronic control system, etc. Working principle of the double cone rotary vacuum dryer A heat source (such as hot water, low-pressure steam or heat transfer oil) is introduced into the closed interlayer, and the heat is transferred to the dried material through the inner shell. Driven by power, the tank body rotates slowly, and the materials in the tank are constantly mixed, thereby achieving the purpose of enhanced drying. The material is in a vacuum state, and the drop in vapor pressure causes the water (solvent) on the surface of the material to reach a saturated state and evaporate, and is discharged and recycled in time by the vacuum pump. The water (solvent) inside the material continuously penetrates the surface, evaporates, and is discharged continuously, and the material is dried in a very short time. Features of double cone rotary vacuum dryer: (1) During vacuum drying, the pressure inside the cylinder is always lower than atmospheric pressure, the number of gas molecules is small, the density is low, and the oxygen content is low, so it can dry easily oxidized drugs and reduce the chance of material contamination. (2) Because the temperature of moisture during vaporization is proportional to the steam pressure, during vacuum drying, the moisture in the material can be vaporized at low temperature, achieving low-temperature drying, which is particularly suitable for the production of drugs with heat-sensitive materials. (3) Vacuum drying can eliminate the surface hardening phenomenon that is easy to occur during normal pressure hot air drying. This is because the pressure difference between the inside and the surface of the vacuum drying material is large. Under the action of the pressure gradient, the moisture quickly moves to the surface, and the surface hardening will not occur. (4) Because the temperature gradient between the inside and outside of the material is small during vacuum drying, the reverse osmosis effect allows the moisture to move and collect independently, effectively overcoming the dispersion phenomenon caused by hot air drying. Double cone rotary vacuum dryer equipment operating procedures Operating procedures 1: Inspection before use 1. Before use, it is necessary to check whether each transmission system is operating normally and whether each fastening part is fastened; 2. Whether the parts that need lubrication have been oiled; 3. Whether the instruments, meters, various pumps and valves are normal; 4. Check whether the instruments, buttons and indicator lights of the electric control cabinet are normal, check whether the grounding wire is in good condition, whether there is leakage and short circuit; 5. Check whether the water, liquid and steam in and out of various pipelines should be unobstructed; 6. Check whether the speed control button is in the zero position; 7. If steam heating is used, check whether the water in the jacket of the dryer drum is drained. After draining the water in the jacket, close the bypass and open the drain valve; 8. Check whether the discharge port and manhole of the dryer drum are airtight, and whether the screws are tightened; 9. Check whether the inside of the dryer drum is clean, and check the drum bag in the dryer frequently to see if it is blocked or damaged. It should be cleaned and replaced in time to keep the vacuum unobstructed; 10. Check whether the discharging tools are complete and clean; 11. Before starting the dryer, make sure that there is no one around the equipment and there are no obstacles before starting. Operation Procedure 2: Startup 1. After receiving the drying notice, start the vacuum pump, open the dryer vacuum pump valve, and close the vent valve to check whether the dryer vacuum meets the requirements. 2. Start the dryer motor power supply, rotate the speed controller button to make the dryer drum rotate slowly, turn the dryer feed drum manhole to the top of the drying table, and stop rotating. 3. Feeding method 3.1 Vacuum extraction Connect the feed port of the dryer to the feed pipe, use vacuum extraction, and after the wet material is extracted, remove the feed pipe and close the feed port valve. 3.2 Feed directly from the dryer drum manhole cover Close the vacuum valve of the dryer drum, open the vent valve, open the vent valve slowly, and close the vent valve after the pressure in the drum is placed at normal pressure. Open the manhole cover and put the material to be dried into the drum. After feeding, cover the manhole cover and tighten the screws. 3.3 Feeding with screw feeder Align the manhole of the dryer drum with the lower discharge port of the screw feeder. Start the motor of the screw feeder to start the screw feeder. Add the material to the drum of the dryer at a certain speed through the screw feeder. After adding the material, turn off the power of the screw feeder. Cover the manhole cover of the dryer drum and tighten the screws. 3.4 Control the feeding amount to 30-50% of the drum volume, and never exceed 65%. 4. After the feeding is completed, open the vacuum valve of the drum, and wait until the vacuum degree in the drum rises to the specified value, then heat and dry. 4.1 Heating with hot water Close the bypass and drain valves, open the water inlet and outlet valves of the dryer drum jacket, and then start the hot water circulation pump for heating. 4.2 Heating with steam Open the drain valve of the dryer jacket, close the bypass, open the steam valve, and control the steam pressure at? Mpa. 4.3 At the beginning of heating, start the speed control button of the dryer drum and control the drum speed at ? r/min, and carry out reduced pressure drying. The maximum drying temperature does not exceed ? ℃, and the drying time is ? hours. Operating Procedure 3: Equipment Maintenance and Inspection 1. During the drying process, the operator is required to check the drying situation every ? min and keep relevant records. 2. The vacuum gauge and thermometer should be checked regularly. Regularly check whether the rotation of each moving part is flexible enough. If any problem is found, the machine should be stopped and repaired in time, and it should not be used reluctantly. 3. The cylindrical worm gear reducer (or continuously variable transmission) should be maintained according to its manual. 5. After the filter in the tank is dried once, the powder adsorbed around it should be removed to make the filter unobstructed. 5. The chain of the chain drive should be refueled at least once a month. 6. The rotary bearing seal ring (made of fluororubber) is used between the vacuum tube of the main engine and the main engine. When a leak is found, it should be replaced immediately. 7. Depending on the operation time, the machine should be inspected and repaired once every six months to one year. During the inspection, it should be assembled in the original position, and the spacing and tolerance of each part should be adjusted, and the corresponding grease (oil) should be replaced or supplemented according to regulations. Operation Procedure 4: Stopping and discharging 1. After drying, close the steam valve and drain valve (or close the hot water inlet and recovery valve), open the circulating cooling water of the dryer for cooling, and turn off the circulating cooling water when the temperature in the mixed dryer is below ? ℃. Adjust the speed control button to stop the dryer, and make the dryer drum discharge port downward, and turn off the power of the dryer. At the same time, close the vacuum valve of the mixed dryer, open the vent valve, vent, and stop the vacuum pump, then replace the cloth cover of the dryer discharge port and connect it to the screw feeder receiving port, and start the screw feeder at the same time to start discharging. When discharging, control the speed of the material through the valve handle of the discharge port. 2. After discharging, turn off the screw feeder. Clean and clear the equipment and site. Operating Procedure 5: Precautions for Use 1. Open: Press the drum motor button, start the regulator power supply, control the speed to slowly increase from zero, generally six revolutions per minute; 2. Close: Slowly adjust the regulator drum to zero, turn off the regulator power supply, and turn off the drum motor button; 3. Be sure to pay attention when operating the forward and reverse rotation. After the drum is closed, wait until the motor stops rotating before controlling the forward and reverse rotation, otherwise the motor will be damaged. The forward and reverse rotation judgment method is that from the side of the motor, it should turn counterclockwise to forward rotation and must not be reversed; 4. Pay attention when pumping materials, slowly rotate and stop in a good position (the drum mouth is tilted against the operating table), pay attention to safety when installing the pipeline, and prevent over-intake, and the material must not contain block-like hard objects. After washing, the suction hose must be removed before turning. 5. There must be a vacuum in the drum during the heating operation, otherwise it will close the material or explode; 6. It is strictly forbidden for personnel to approach the drum during operation to prevent mechanical damage; 7. When drying, the steam must be turned on slowly, and the pressure cannot exceed after turning on? Mpa (the design value of the jacket pressure is 0.25Mpa), the temperature of the material should not be too high when it is drying, which will affect the quality of the finished product. 8. When the screw feeder or screw discharging machine is running, it is forbidden to put your hands into the inner wall to operate to prevent entanglement. 9. Before cleaning the inner wall, you must apply to the relevant department and obtain relevant certificates before the operator can enter the drum to take out the drum bag. 10. When the finished product is poured into the hopper, no metal or other debris can be mixed in to avoid accidents. 11. The feeding speed should be slow and uniform. 12. After each shift of use, the machine cavity must be cleaned. When the drum is feeding and discharging materials, you should pay attention to climbing operations and wear protective equipment such as masks and gloves. You must wear a safety belt and a safety helmet when climbing onto the drum platform to operate. The main power supply of the attic must be turned off when the drum is discharging, sucking, and shoveling materials in the middle. Common faults and solutions of double cone rotary vacuum dryer Common fault 1: Too much loading Since the loading amount of the dryer is related to the bulk density of the material (referring to the mass of the material per unit volume), in general, the material specific gravity is calculated as 0.6 g/cm3 when the dryer is designed. If it exceeds this specific gravity, on the one hand, it will affect the drying efficiency of the material; on the other hand, long-term operation will reduce the service life of the motor, turbine reducer, sprocket, chain, bearing, etc. In general, the filling rate of the double cone rotary vacuum dryer (the ratio of the actual filling volume to the volume of the drying cylinder) is usually between 30% and 50%, and the vacuum cover in the double cone dryer cannot be covered, otherwise it will affect the drying rate. Common fault 2: The vacuum degree is too low or too high The double cone rotary vacuum dryer often has the problem of too low or too high vacuum during the drying process, which will not only affect the efficiency and quality of the material drying, but also affect the production safety of the workshop. Although the higher the vacuum degree, the more conducive it is to the vaporization of water at low temperature, but too high vacuum is not conducive to heat conduction and affects the drying effect of the material. There may be four reasons for the vacuum being too low or too high: leakage of the mechanical seal at the vacuum end; leakage or blockage of the vacuum pipe; blockage of the filter; and difficulty in evaporating the material solvent due to the hot water or steam temperature being too low. To solve such problems, it is necessary to consider the temperature of the hot water and steam of the dryer, and to conduct regular inspections during use, as well as to perform maintenance and cleaning. Common Fault Three: The outer layer of the cylinder liner falls off. In actual production, the glass-lined liner of the rotary cylinder is very easy to be damaged if it is not used and maintained correctly. Especially for acidic and alkaline materials, the drying discharge is not clean, the material is easy to form a wall, damage the cylinder liner, and affect the service life of the dryer. To solve such problems, you only need to select a suitable dryer according to the nature of the material, ensure that the material is discharged cleanly during use, conduct regular inspections, and perform maintenance and cleaning. Common fault 4: Too much air flow during "emptying" In actual production applications, when filling the vacuum, the double cone rotary vacuum dryer may experience phenomena such as bending of the vacuum tube, damage to the sealing sleeve, deformation and even breakage of the filter head. This is because during the drying process, air is put into the tank to recoil the filter head. At this time, the tank has reached a high vacuum degree, which will cause a strong impact of positive and negative airflows and damage the vacuum system. Therefore, after the material is dried, the tank needs to be emptied. When emptying, the emptying valve must be used to control its flow, that is, first open the valve a little, and then slowly increase it after the vacuum degree in the tank gradually decreases; or add a pressure reducing valve to control the flow of air. Common fault 5: Excessive noise During the use of the dryer, the dryer's feet are loose, the worm gear reducer (gearbox) is damaged, the bearing is damaged, the chain is too loose or too tight, etc., which causes excessive noise. For damage to the reducer, bearings and chains, you only need to check regularly, pay attention to adding lubricating oil, troubleshoot in time, and do preventive maintenance. Common fault six: leakage at the inlet and outlet. Leakage at the inlet and outlet is generally caused by the sticking or damage of the sealing strip. Just clean the material on the surface or replace the sealing strip. In the actual production management of the workshop, preventive maintenance should be done well and wearing parts should be replaced in advance. Common fault seven: material walling. In actual production, if material walling occurs, it will not only affect the mass transfer and heat transfer inside the dryer, thereby affecting the properties of the entire batch of materials, resulting in unqualified products, but also affect the service life of the dryer. Regarding the problem of reducing the walling of materials in the double-cone rotary vacuum dryer, the following solutions have been studied and discussed: Inner cavity wall coating: According to the specific properties of the material, a specific anti-walling protective layer is applied to the double-cone rotary vacuum dryer to prevent the material from walling. However, this has high requirements for the coating. On the one hand, the physical properties of the coating must be considered; on the other hand, whether cross contamination will occur must be considered. Adding medium balls to the drying materials: In the process of drying materials, adding inert medium balls to mix with the materials can effectively reduce the wall formation of the materials. However, in the process of selecting medium balls, the influence of the shape of the medium balls on the inner tank of the dryer should be fully considered, and the separation and recovery process with the materials in the later stage should also be considered. Improving the smoothness of the cavity wall: Before drying each batch of materials, improving the smoothness of the cavity wall can effectively reduce the degree of wall formation of the materials. However, before drying, the cavity wall of the dryer should be cleaned regularly, which also greatly increases the workload of the workers in the drying room. Optimization of control of steps such as feeding, temperature rise, and speed: According to the properties of the materials, before drying, optimizing the steps of feeding, temperature rise, and speed of the dryer can also effectively reduce the degree of wall formation of the materials. However, for special materials, optimizing the steps of feeding, temperature rise, and speed of the dryer requires relevant orthogonal optimization tests to obtain the optimal drying conditions. Under normal circumstances, variable temperature drying is often used, that is, the temperature is low at the beginning of drying, and the temperature is gradually increased to increase the drying speed. Improve the crystallization effect of the material's previous process: This method mainly changes the crystal structure of the material from a process perspective, changes the crystallization or desolvation process of the material, and can fundamentally eliminate the wall of the material. However, while changing the process, there is a greater risk to the quality and properties of the material, and it is difficult to fundamentally change the process. Dry product backmixing: Before drying each batch of wet materials, add a certain amount of dry products from the previous batch, and use a mixed drying method to effectively eliminate the wall of the material and may also improve the drying efficiency of the material. Equipment selection: Choose different dryer equipment models according to the properties of the material. At present, in addition to the double-cone rotary vacuum dryer, the most widely used drying equipment mainly includes: tray oven, drum vacuum dryer, V-shaped mixing dryer and three-in-one filter dryer, airflow dryer, etc. When selecting other drying equipment, it is also necessary to consider the properties of the material (including the viscosity, allowable temperature, bulk density and slip angle of the material), drying temperature, working vacuum degree and filling rate. The above is a series of knowledge introduction on the structure, principle, performance characteristics, operating procedures, common faults and solutions of the double-cone rotary vacuum dryer. Double cone rotary vacuum dryer is suitable for the concentration, mixing, drying of powder, granular and fiber materials in the chemical, pharmaceutical, food and other industries, as well as materials that need to be dried at low temperature (such as biochemical products, etc.).

News

Double cone rotary vacuum dryer structure, working principle, operating procedures, common faults and solutions