Flash dryer is a continuous drying plant used for drying variety of wet cakes by disintegrating wet cake into fine powder and dried by hot air to form powder. The whole process is fully automatic requiring no handling or human involvement.
WORKING PRINCIPLE OF FLASH DRYER
Flash dryer is a continuous drying plant used for drying variety of wet cakes by disintegrating wet cake into fine powder and dried by hot air to form powder. The whole process is fully automatic requiring no handling or human involvement. The feed rate is adjusted automatically as per the variation in moisture content in wet cake thereby achieving consistent product quality.
The principle of Flash Drying is to evaporate surface moisture instantaneously. The word “flash” is used, as the drying time is very less from milli to few seconds. It is well known fact that the surface area of wet lump increases as the size of lump decreases. The wet cake is disintegrated into fines to increase the surface area. The drying is instantaneous and the material remains at wet bulb temperature of air. Hence it is also called as "wet bulb drying".
The air velocities are similar to that of pneumatic conveying. The powder remains suspended in air and gets conveyed while drying. Hence it is also called as pneumatic dryer. The retention of a given solids particles in the system is very short, typically in seconds.
These make it ideal for drying heat sensitive, easily oxidized, materials that cannot be exposed to process conditions for extended periods.
Flash dryer is energy efficient, requiring no intermediate material handling. It is a continuous production machine suitable for pasty / sticky wet cakes. These unique features make it ideal replacement for conventional tray and rotary drying.
• Wet cake is fed in feed mechanism. The feed mechanism consists of balance tank, stirrer and screw feeder.
• The stirrer feeds the screw feeder. The screw feeder gives controlled feed at rated capacity to disintegrator.
• The air after passing through Air Filter is heated in Oil fired hot air generator or steam / thermic fluid based radiator.
• Hot air and wet cake get thoroughly mixed in the cage mill type disintegrator. Disintegration and drying of wet cake takes place in disintegrator.
• Wet cake is rapidly dried and about 50% drying take place in the disintegrator.
• Drying duct conveys the pulverized material to cyclone. Drying gets completed in conveying duct.
• The time taken by disintegrated powder to travel through drying duct is called residence time of drying.
• The material looses moisture that is absorbed by hot air. The temperature of air reduces while its humidity increases.
• Powder is further dried in cyclone. Separation of dried powder and air takes place in cyclone. Powder is discharged from cyclone through powder discharge valves.
• Fine particles escaped from cyclone are conveyed to bag filter.
• Bag filter recovers the fine particles. The air coming out of bag filter is dust free and confirms to pollution control norms.
• Two blowers, one at inlet & other at outlet, working on Push-Pull principle maintain the airflow in the system.
• Push-Pull principle ensures that the ambient pressure is maintained at feeding system to avoid dusting of material. Also it avoids extreme pressures (either positive or negative) in the system.
• The powder collected from cyclone and bag filter can be pneumatically conveyed to storage bin or bagging section.
MAIN COMPONENTS OF FLASH DRYER
1. Feeding Mechanism
2. Cage Mill Disintegrator
3. F. D. Fan and I. D. Fan
4. Drying cum Conveying Duct
5. Control Panel & Instrumentation
OTHER COMPONENTS OF FLASH DRYER
1. AIR FILTER
2. HOT AIR GENERATOR
4. SECONDARY DISINTEGRATOR.
5. BAG FILTER
6. ROTARY AIR VALVE
Easy to Operate:
1. Fully automatic machine consisting of following
• Appropriate safety interlocks.
• PID temperature controller for ensuring constant air inlet temperature. Steady state of burner giving minimum maintenance of burner.
• PID temperature controller with variable speed drive for screw feeder ensuring constant air outlet temperature.
• Audio alarms for any deviation from the set parameter.
• Continuous monitoring / recording of vital parameters.
2. Parameters like airflow rate, fuel firing rate, temperatures and so on, are set once for all for a given material properties at the time of commissioning. Hence it is easy to operate in subsequent runs.
Easy to diagnose problems:
1. The dryer is easy to diagnose for problems due to following facilities-
• Continuous visual indication.
• Manometers for pressure drops of critical components.
• Viewing windows at strategic locations.
2. In our service manual exhaustive troubleshooting chart is given. Prior to handing over the dryer our service engineer educates the operators by simulating various operating conditions.
This makes the Flash Dryer user friendly.
EXCLUSIVE FEATURES OF FLASH DRYING PLANT
• Reduced running cost.
• Continuous production machine without human touch.
• Ideal replacement for tray drying of wet cakes.
• Extremely sticky /pasty wet cake can be handled.
• Particle size as fine as 500 mesh is achievable.
• Low residence time – minimum exposure to heat – retains original product quality.
• On line particle size reduction-eliminating need of separate pulverizer.
• No product degradation or charring.
• Proprietary design of disintegrator ensures uniform mixing of wet cake and hot air giving consistent and homogeneous powder quality.
• Fully Automatic – needs little running attention.
• Negligible material dusting.
• High volume processing.
• Large filtering area of Bag filter – reduced pressure drop – large savings in power consumption of blower.
• Measurement of pressure drops at various places facilitates easy trouble shooting and maintenance.
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