Spray Dryer Selection

Catalyst formulation and desired powder properties decide the choice.

Fine to medium coarse powders are produced in co-current spray dryers with rotary atomizers. The particle size distribution is precisely adjusted through control of the atomizer wheel speed. Where inlet drying temperatures are restricted to below 550° C, roof air dispersers promote optimum drying conditions by thorough mixing of the catalyst spray with drying air. If higher inlet temperatures can be used without detriment to the catalyst, a drying chamber with central air disperser is the preferred layout.

Spray dryer with rotary atomizer and roof air disperser (Type SD)

Spray dryer with rotary atomizer and central air disperser (Type SD - high temperature)

Mixed flow spray dryer with nozzle atomizer (Type N)

Coarse grained powders can be produced using low speed atomizer wheel operation. However, this is only feasible for large production requirements involving large diameter drying chambers. Coarse powders from smaller production units are best produced in mixed-flow spray dryers, where nozzles spray the catalyst formulation up into the drying air entering through a roof air disperser.

Catalyst formulations containing organic solvents are dried in an inert gas closed cycle plant. The specified particle size determines the type of atomizer and design of drying chamber. Where high outlet temperatures are required to achieve the specified catalyst residual moisture content, part of the exhaust air can be recycled to preheat the drying air passing to the drying chamber. This partial recycle concept further improves the thermal efficiency of the spray drying process.

All Niro spray dryers are supplied with exhaust air cleaning equipment necessary to meet local particulate emission codes.