The initial contact between spray droplets and drying air controls evaporation rates
and product temperatures in the dryer. There are three modes of Contact:
Co- current
Drying air and particles move through the drying chamber in the same direction.
Product temperatures on discharge form the dryer are lower than the exhaust air
temperature, and hence this is an ideal mode for drying heat sensitive products. When
operating with rotary atomizer, the air disperser creates a high degree of air rotation,
giving uniform temperatures throughout the drying chamber. However, an alternative
non- rotating airflow is often used in tower or Filtermat- type spray dryers using nozzle
atomizers with equal success.
Counter- current
Drying air and particles move through the drying chamber in opposite directions. This
mode is suitable for products, which require a degree of heat treatment during drying.
The temperature of the powder leaving the dryer is usually higher than the exhaust air
temperatures.
Mixed flow
Particle movement through the drying chamber experiences both co- current and
counter- current phases. This mode is suitable for heat stable products where coarse
powder requirements necessitate the use of nozzle atomizers, spraying upwards into
an incoming airflow, or for heat sensitive products where the atomizer sprays droplets
downwards towards an integrated fluid bed and the air inlet and outlet are located at
the top of the drying chamber.
The initial contact between spray droplets and drying air controls evaporation ratesand product temperatures in the dryer. There are three modes of Contact:Co- currentDrying air and particles move through the drying chamber in the same direction.Product temperatures on discharge form the dryer are lower than the exhaust airtemperature, and hence this is an ideal mode for drying heat sensitive products. Whenoperating with rotary atomizer, the air disperser creates a high degree of air rotation,giving uniform temperatures throughout the drying chamber. However, an alternativenon- rotating airflow is often used in tower or Filtermat- type spray dryers using nozzleatomizers with equal success.Counter- currentDrying air and particles move through the drying chamber in opposite directions. Thismode is suitable for products, which require a degree of heat treatment during drying.The temperature of the powder leaving the dryer is usually higher than the exhaust airtemperatures.Mixed flowParticle movement through the drying chamber experiences both co- current andcounter- current phases. This mode is suitable for heat stable products where coarsepowder requirements necessitate the use of nozzle atomizers, spraying upwards intoan incoming airflow, or for heat sensitive products where the atomizer sprays dropletsdownwards towards an integrated fluid bed and the air inlet and outlet are located atthe top of the drying chamber.
การแปล กรุณารอสักครู่..
