Views: 890 Author: Site Editor Publish Time: 2020-01-27 Origin: Site
Plastic hot air dryers are commonly used drying equipment in the production and processing of plastics. During the use of the hot air dryer, some faults may be encountered. It is necessary to check, analyze the cause of the fault, and solve it in time to ensure that the equipment can work normally.
The drying process of plastic particles by industrial dryer is relatively simple, but in some cases, the particles can not be completely dried. The factors affecting the drying effect are as follows.
1. Airflow: The dry hot air transfers heat to the particles in the dry silo, removes moisture from the surface of the pellets, and returns the moisture to the dryer. Therefore, there must be sufficient gas flow to heat the resin to the drying temperature and maintain this temperature for a certain period of time.
2. Dew point: In the dryer, the wet air is first removed to contain very low residual moisture. Then, the relative humidity is reduced by heating the air. At this time, the steam pressure of dry air is low. By heating, the water molecules inside the particles get rid of the bonding force and diffuse to the air around the particles.
3. Time: In the air around the particles, the absorption of heat and the diffusion of water molecules to the surface of the particles take a certain amount of time. Therefore, the resin supplier should specify the time it takes for a material to dry effectively at the proper temperature and dew point.
When there is a problem of poor drying, the problem should be discovered from the following three aspects.
1. Dryer Status
Pay particular attention to air filters and hoses when inspecting the dryer. A blocked filter or a flattened hose can reduce airflow and affect the operation of the dryer. A damaged filter can contaminate the desiccant and inhibit its ability to absorb moisture; a broken hose can introduce humid ambient air into the dry airflow. In this case, the desiccant causes premature moisture absorption and high dew point. The poor heat preservation measures of the hose and the dry silo also affect the drying temperature.
2. The Channel of Dryer
In the channel of dryer, the drying temperature should be measured at the entrance of the silo in order to compensate for the heat loss of the dryer in the hose. If the material is not dried enough after it comes out of the dryer, it should be checked whether there is enough space in the drying bin to provide sufficient and effective drying time. Therefore, attention should be paid to the size and shape of granular or crushed materials, which will affect the bulk density and residence time of dry materials. When the dry air comes out of the top of the dryer, most of the heat has been released. If the return air overheats the desiccant, it will reduce its ability to adsorb moisture from the dry air. So it need check the return air temperature of the dryer. In order to prevent the temperature of reflux air from getting higher, as long as a heat exchanger is installed on the reflux air channel, it can ensure that the desiccant can effectively remove the moisture in the dry air.
3. Regeneration and Cooling of Desiccants
The hygroscopic capacity of the desiccant is limited, so the moisture it adsorbs must be removed by regeneration. Dew point readings can help identify problems, so the dry air dew point value should be monitored throughout the drying process. If the dew point immediately peaks after the desiccant is replaced, it indicates that the desiccant is not sufficiently cooled before it is placed, so that it does not adsorb moisture well. If the desiccant is not properly cooled, the peak temperature will appear, and the sudden change of temperature will reduce the drying ability of the desiccant to heat sensitive materials such as ionomers, amorphous polyesters and so on. If the dew point reading is normal after the drying agent bed is replaced, but the dew point rises rapidly before the drying cycle of the drying agent ends, it indicates that the ambient air may enter the closed air path and cause the dryer to absorb moisture prematurely. If the dew point reading is close to the dew point reading of reflux air, it indicates that the regeneration channel is completely invalid or the desiccant is seriously polluted.
Fast troubleshooting in production directly affects the output, so it is very important to find out the fault and solve it quickly. It requires more professional knowledge and some maintenance experience. Because each equipment has different circuits and configurations. Here is just a comprehensive introduction of troubleshooting for dryer. I hope it will help you a little.