As spray drying is the most widely used industrial process involving particle formation and drying, it is natural that the GEA Niro Test Center has the widest range of test plants available for testing the complete range of spray drying techniques.
All pumpable products, both heat or non-heat sensitive, can be processed via GEA Niro’s versatile spray dryers and are able to meet the requirements for small- or large-scale production. GEA Niro’s spray dryers are designed to produce precise properties such as particle size, bulk density, moisture content, solubility, dispersibility etc. to the exact requirements as defined by the plant operator.
Before selecting the design of a spray dryer and the type of atomizer, several properties of the source feed and final product have to be evaluated, hence the need for testing. Factors to be taken into consideration may include the actual liquid to be dried, particle size, distribution and powder quality. This might mean testing with more than one type of technique – thus the opportunities within GEA Niro’s Test Center, where parallel testing can be arranged, are unmatched.
Overview of spray drying techniques
Atomization is achieved by feeding a liquid solution or suspension onto a high speed spinning wheel. The rotary atomizer is placed in the ceiling air disperser and operates with a vaned atomizer wheel for non-abrasive feeds, or with a carbide bushing wheel for abrasive feeds. Other wheel designs are available for special applications. The particle size of the powder produced is controlled through change of wheel speed.
Atomization is achieved by using a compressed gas to atomize the liquid feed. The nozzle is placed close to the outlet of the ceiling air disperser. This arrangement is ideal for heat sensitive feeds and has the added advantage of being able to handle both low and high viscosity liquids. The particle size is controlled by varying the nozzle flow ratio between compressed gas and feed.
Atomization is achieved by pressing a liquid solution or suspension through an orifice in the nozzle by means of a high pressure piston pump or a mono pump. Pressure nozzles are typically used to form coarser powders. Particle size of the product is controlled by the pressure given by the pump.
Two-fluid Nozzle or Pressure Nozzle. The nozzle is placed in the conical section of the drying chamber, spraying upwards into hot air entering the drying chamber through the ceiling air disperser. The fountain mode has the advantage of spray drying higher solid feeds and producing coarser powders. Selection of nozzle type depends on the feed properties and powder specification.