By : Afaf Hithnawi Dr: Mohammad Sabbah Spray drying 1

Out line Definition. Main terms of spray drying. Stages of spray drying. Atomizer type. Advantages,disadvantages. 2

Definition : Physical separation process for solid particles from solution, suspended particles, slurries, and pasts by using sources of heat (thermal energy), to form powders (solid products). 3

Main terms of spray drying : 1-Solution with can be pumped (flow). 2-Non sintering solid particles. 3- High temperature demand ( source of energy). 4-product with high solubility, hygroscopicity. 4

Stages of conventional spray drying: 1-Heating of hot drying medium. 2-Atomization of feed into droplet. 3-Spray-air contact and drying droplet. 4-Product recovery and air treatment.. 5

Atomizer types: 1-Centrefugal atomizers(Rotary): droplet size range with (1-600) micron can be produced. -_Rotary atomization based on centrifugal energy,. rotating wheel and speed of rotation _And these variables are selected according to the liquid product and. required dried properties 6

2-Pressure nozzle A device designed to control the direction or characteristics of a fluid flow (especially to increase velocity) as it exits (or Droplet size micron))enters) an enclosed chamber or pipe. Advantages : _ simple and cheap. _No moving part. _Low energy consumption. Limitations : _Low capacity (feed rat for nozzle) _high tendency to clots. 7

3-Two fluid nozzles(Pneumatic) _ Droplet size( micron). _Produce a spray by using a second fluid,such as compressed air or steam, to atomize the feed. advantages : -no moving part -produce product with very small size. Limitation : -high energy consumption. -high tendency to erosion. 8

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Air direction compared with feed direction 10

Advantages of spray drying 1-continuos and easy to control process. 2-rapid and non-contact draying. 3- The droplets are small 4-Applicable to toxic and explosive materials. 5-Good properties for the spray-dried powder so it can be easily compressed into the form of tablets. 6-labor cost is low since the materials is dried in single operation without handling. 11

Disadvantages of spry draying 1- solid materials cannot be dried. 2- the equipment is very costly and bulky. 3- there is a lot of heat wasted 4-heat degradation possibility in high -temperature spray drying. 12

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