Foreword

Spray granulation drying machine is a PTC thermistor ceramics production process important equipment, the higher the price of equipment, complex composition, use and maintenance more difficult. The good functioning of the device, not only to ensure the normal PTC thermistor ceramics production, it can also be appropriate to extend the useful life of equipment, reduce production costs, so the correct operation of the equipment, and strengthen the maintenance is necessary.

1 spray granulation drying machine theory and composition

Granulation is PTC thermistor ceramic production process is very important process, the quality of the pellets directly affect the PTC ceramic appearance, mechanical properties and resistance-temperature characteristics. Granulation refers added finely ground powder in an amount of adhesive evenly to reconcile and make it a granular powder, the powder has good flowability and rolling resistance, so that the tabletting process It can be obtained with good strength, not delamination of the film. In the industrial production using spray drying granulation, the basic principle is the powder with a binder, with a sprayer sprayed into the granulation tower atomized droplets are dried tower tower hot air into granules like powder, then discharged from the bottom of the drying tower.

The company uses a pressure-type spray granulation dryer is mainly composed of feeding system, drying equipment system, dust removal system, heating system and electrical system components, and each system also includes a number of related equipment.

Feed system consists of mixing barrels, filters, diaphragm pump and spray gun and other components. Good secondary milling slurry transferred from the mill to the mixing bucket, the diaphragm is drawn through the filter and transfer, and then through the gun into the drying tower.

Slurry from the spray gun nozzle into a drying tower began to spray granulation drying process, the specific process is divided into three stages:

(1) slurry atomization. Slurry from the feeding system to a certain pressure from the nozzle diaphragm is pressed into the drying tower, the energy is converted into kinetic energy of the pressure, the slurry from the nozzle from the bottom up, forming a layer of high-speed film, then the film is split into droplets. Droplet size and spray pressure generated inversely proportional to the square of the production capacity and the nozzle pressure.

(2) drying the fog particles into a ball. Fog particles mixed with the hot air flow in the manner of work, the hot air is entering the tower, hot air distributor produce a downward flow of air flow through the hot wire air distributor on the top cover, by the droplets sprayed into the heat up air stream. Since the droplet to form a spherical surface tension effects, and because the droplet having a large surface area, wherein the rapid evaporation of water and dried, and the contraction of the final dried powder of spherical particles.

(3) powder particles discharged. Spherical particles formed in the drying tower powder is gradually settling, separation and hot air, the lower portion of the column so that the funnel cavity pellets were pooled and discharged from the discharge port. Fine particulate material together with the dry air from the blower is connected to the upper portion of the funnel-shaped dust extraction into the system. The drying tower conveying hot air blower, exhaust fan and formed a drying tower drying system.

Dust removal system by the high efficiency cyclone, bag filter, centrifugal fans and other components. The exhaust fan finer particulate material together with the dry air into the high efficiency cyclone. After the effective separation of fine particulate material into the collection tube separator at the bottom of the recovery, the remaining fine particulate material containing a very small amount of gas inhaled by the centrifugal fan again after a bag filter dust collection, to achieve a harmless treatment of exhaust gas, and finally the exhaust gas discharged from the chimney.

In addition, electric heaters and other heating stove gas engine system consisting of dry air heating Tati. Electrical control cabinet and installation of electrical systems in the inlet and outlet temperature monitoring site sensors and other components of each of the major aspects of the entire spray granulation drying machine monitoring and control to ensure the normal operation of the entire apparatus.

2 daily operation and precautions

In the daily production process, the equipment should be carried out before starting the necessary preparatory work. First check the bearings and seals each portion of the device for loose connections, lubricating mechanical parts and the status of each individual water, wind, and other slurry pipe valve port is in the desired position. Then check the voltage and power meter is normal, the last check slurry mixing barrel and the amount of slurry concentration, etc., if there is a problem should be immediately removed.

Then turn open blower, exhaust fan, and then open the heating switch to warm up. When the discharge port temperature reaches the set temperature (usually about 130 ℃), start the feed pump and dust removal system. When the pump pressure reaches 2MPa, Open gun start granulation. Equipment operation should be observed in the case of spray pump and material working conditions, if there is blocking phenomenon gun nozzles need cleaning or replacement immediately. After the normal operation of equipment, but also the timing receipts, regularly check the operation of each system, recording the process parameters, and pay attention to clean up the vibration filter sieve.

At the end of granulation, should first shut down the heating device, the gas engine stops running. Then close the gun valve replacement gun, unscrew the nozzle and rinse. When the inlet temperature is reduced to below 100 ℃ can stop the blower and exhaust fan running. Then clean up the drying tower and more than expected in the dust, and dust close air hammer, and finally close the mains, complete production operations.

In case of emergency, the device must be shut down immediately, it should first shut down the feed pump and blower. If it encountered a power outage, you should pull out the gas engine, so that the natural cooling tower, and then open the drain valve, drain pipes feed the pulp slurry, and cleaning equipment.

3 Maintenance

PTC granulation is an important part of the production process to maintain the normal operation of the equipment is necessary to ensure that PTC produce a stable condition. Regular cleaning, maintenance and care will help to discover and solve potential failures, reduce downtime, ensure the production of normal and stable.

Long-running equipment or improper operation, there will be some of the equipment within the aggregate affect the normal operation, this time to be stopped for cleaning. For drying tower aggregate cleaning, cleaning door should be opened with a long broom to sweep the bottom of the funnel-shaped aggregates, open the discharge valve, rinse with tap water column. Within the cyclone dust clears, we need to enable cyclone, with a broom sweeping aggregates, also wash with water if necessary. For bag filter cleaning, open the control switch, pounded, and then open the cleaning door, knock bag filter, and finally replace the filter bag. For Cleanup slurry pipeline system, open the drain valve bi-directional filter, clean filter screen and lines, and then open the feed pump, water and raw material, cleaning pump, the regulator bag and pipe. After a period of time (usually about 600h) operation, need to spray granulation drying machine carry out the necessary inspection and maintenance.

For the feeder system, you should check the filters, pipes, valves, nozzles, etc., to see whether the blockage, regular cleaning, checking, nozzle wear to be replaced. The feed pump should be checked for leaks, pressure is normal, the oil level is normal and the like. For fans, you should check whether the shaft and bearing short of oil fever, with or without vibration, noise, cleaning fan blades when necessary and to make balance proofreading. For the heater, you should check whether the normal heat pipe, washing pipe, pump, nozzle three of the filter when necessary. In addition, should pay attention to each motor or without fever, vibration, abnormal sound, etc., if the control cabinet instrumentation and electrical work and so on.

In addition, the operation of the device is about 2 400h (generally take advantage of the shutdown period), required by the service personnel partial disintegration and maintenance.