Spray granulator dryer is an important equipment in the production process of PTC thermal ceramics. The equipment is expensive, complex in composition, and difficult to use and maintain. The good operation of the equipment can not only ensure the normal production of PTC thermal ceramics, but also can prolong the service life of the equipment and reduce the production cost. Therefore, it is necessary to properly operate the equipment and enhance the maintenance.
1 principle and composition of spray granulator dryer
Granulation is a very important process in the production of PTC heat-sensitive ceramic sheets. The quality of the pellets directly affects the appearance, mechanical properties, and temperature-resistance characteristics of the PTC ceramic sheet. Granulation refers to the addition of a certain amount of binder in a finely ground powder, which is uniformly blended to form a granular powder. This powder has good fluidity and rolling properties, so that it can be used in the tableting process. Films with better strength and less cracking can be obtained. The spray drying method is used for granulation in industrial production. The basic principle is that the powder with binder is sprayed into the prilling tower with a sprayer for atomization. The mist droplets in the tower are dried into particles by the hot airflow in the tower. The powder is then discharged from the bottom of the drying tower.
The pressure spray granulator dryer used by the company is mainly composed of a feeding system, a drying equipment system, a dust removal system, a heating system and an electrical system. Each system also includes some related equipment.
The feeding system consists of a mixing tank, a filter, a diaphragm pump and a spray gun. The ball-milled secondary slurry is transferred from the ball mill to the mixing tank, which is pumped by the diaphragm pump and conveyed, and then passes through the spray gun into the drying tower.
The slurry enters the drying tower from the nozzle of the spray gun and begins the process of spray granulation and drying. The specific process is divided into three stages:
(1) Slurry atomization. The slurry is pressed by the diaphragm pump in the feeding system from the nozzle into the drying tower at a certain pressure. The pressure energy is converted into kinetic energy. The slurry is ejected from the nozzle from the bottom up, forming a layer of high-speed liquid film, and the liquid film is split into Droplets. The droplet size produced by atomization is inversely proportional to the pressure, and the productivity of the nozzle is proportional to the square of the pressure.
(2) The pellets are dried into balls. The mist particles and the hot air work in a mixed flow mode. The hot air enters the tower through the hot air distributor on the top cover. The hot air distributor generates a down stream air flow, and the mist sprays heat from bottom to top. Air flow. The droplets form a sphere due to the surface tension, and at the same time, the droplets have a large surface area, in which the moisture rapidly evaporates and dries, and finally shrinks to form a dry spherical particle powder.
(3) The granular powder is discharged. The resulting spherical particulate powder gradually settles in the drying tower and separates from the hot air. The funnel-shaped cavity in the lower part of the tower collects the particulate material and discharges it from the discharge opening. The finer particles, together with the dry air, are drawn by a suction fan connected to the upper part of the funnel and enter the dust removal system. A blower, a drying tower, and an exhaust fan for conveying hot air to the drying tower constitute a drying system.
The dust removal system consists of high efficiency cyclone separator, bag filter, centrifugal fan and so on. The blower feeds the finer particles together with the drying air into the high efficiency cyclone separator. After effective separation, finer particles are collected in the collection tube at the bottom of the separator, and the remaining exhaust gas containing a very small amount of fine particles is sucked into the bag filter by a centrifugal fan and collected again to achieve a harmless treatment of the exhaust gas. The exhaust gas is discharged from the chimney.
In addition, a heating system consisting of an electric heater and a gas-fired hot air oven provides hot air for the drying tower. Electrical control cabinets and on-site sensors installed at the inlet and outlet ports to monitor the temperature of the electrical system to monitor and control all major aspects of the entire spray granulator dryer to ensure the normal operation of the entire equipment.
2 daily operations and precautions
In the daily production process, necessary preparations must be made before starting the equipment. First, check the looseness of the joints between the bearings and the sealing parts of the various devices, and the lubricating oil conditions of the various mechanical parts and whether the respective water, wind, and slurry valve ports are in the desired positions. Then turn on the power to check the voltage and the instrument is normal, and finally check the amount of slurry in the slurry mixing tank and the concentration, etc., if there is a problem should be promptly ruled out.
Then turn on the blower, exhaust fan, then turn on the heating switch to start warming. When the outlet temperature reaches the set temperature (usually about 130 °C), start the feed pump and dust removal system. When the pump pressure reached 2 MPa, the spray gun was turned on to start granulation. After the equipment is running, it is necessary to observe the atomization conditions and the working condition of the material pump in time. If there is a phenomenon of blocking the gun, the nozzle must be cleaned or replaced immediately. After normal operation of the equipment, it is also necessary to receive materials periodically, check the operation of each system at regular intervals, record the process parameters, and pay attention to cleaning the vibrating screen.
At the end of granulation, the heating device should be shut down first to stop the operation of the gas engine. Then close the gun valve, replace the gun, unscrew the nozzle and rinse it clean. When the inlet temperature is reduced below 100°C, the operation of the blower and the exhaust fan can be stopped. Then clean the excess material in the drying tower and the dust collector, close the dust collector and the air hammer, and finally turn off the main power supply to complete the production operation.
In the event of an emergency, the equipment must be shut down immediately. The blower and material pump should be shut down first. If there is a sudden power outage, the gas engine should be pulled out to cool the tower body naturally, then the sewage valve is opened, the slurry in the slurry pipeline is drained, and the equipment is cleaned.
3 Maintenance and Maintenance
Granulation is an important part of the PTC production process. Maintaining the normal operation of equipment is a necessary condition for ensuring the stability of PTC production. Regular cleaning, maintenance, and maintenance can help identify problems in a timely manner, resolve potential problems, reduce downtime, and ensure normal production.
If the equipment is operated for a long time or due to improper operation, aggregates may appear in some equipment and affect normal operation. At this time, it is necessary to stop the work for cleaning. For the cleaning of the aggregates in the drying tower, the sweeping door should be opened, the funnel-shaped bottom aggregate should be removed with a long broom, the discharge valve should be opened, and the tower should be flushed with tap water. The removal of dust from the cyclone separator also requires the opening of a cyclone separator, sweeping the aggregate with a broom, and flushing with water if necessary. For the cleaning of the bag filter, the control switch should be turned on, hit continuously, then open the cleaning door, hit the bag filter, and finally replace the filter bag. For the cleaning of the slurry piping system, the bi-directional filter drain valve should be opened, the filter screen and piping should be cleaned, and then the material pump should be opened to replace the material with water, and to clean the pump tube, voltage regulation package and piping. After a period of time (generally 600 hours or so), the spray granulator drier needs to be inspected and maintained. For the feeding system, check the filters, pipes, valves, nozzles, etc., to see if there is any blockage, regular cleaning, and check the nozzle wear for timely replacement. The material pump should be inspected for oil leakage, whether the pressure is normal, and whether the oil level is normal. For the fan, check whether the shaft and the bearing are hot and have no vibration or noise. If necessary, clean the fan blade and balance the fan blades. For the heater, check whether the heat pipe is normal. If necessary, clean the filter at the three places of the oil pipe, oil pump and nozzle. In addition, it should also pay attention to whether the motor has any heat, vibration, noise, etc., and whether the control cabinet's instruments and electrical appliances are working properly.
In addition, the equipment must be partially dismantled and repaired by maintenance personnel during the operation of the equipment for approximately 2400 hours (ordinary/discontinued production).
N-Butyl-N-Methylpyrrolidinium Bromide,N-Butyl-N-Methylpyrrolidinium Bromide 93457-69-3,Cas 93457-69-3,Pyrrolidine Ionic Liquids
HENAN BON INDUSTRIAL(CHEMICAL) CO.,LTD , https://www.bonchemical.com