Overheated steam drying

Principle of spray drying in overheated steam

Overheated steam is water vapour whose temperature is higher than the boiling temperature at the pressure at which the steam is located.

Spray drying is a very widespread drying technique in the world, which makes it possible to transform liquid products into powder. If the drying gas leaving the appliance is recycled to the heater after separating it from the powder particles, instead of releasing it to the atmosphere, it will very quickly become saturated into steam, which will become the drying gas.

The benefits of overheated steam are :

• Zero ignition and explosion risk
• High specific evaporative flow
• Gaseous discharge reduced to zero
• Energy saving

 

Our industrial pilot

Thanks to the know-how of TECHNI PROCESS it was possible to extrapolate the results obtained during the feasibility study of drying by atomisation into overheated steam carried out at ENSIA on a pilot with an evaporative capacity of 10 L/ h and to draw an industrial pilot with a capacity 40 L/h evaporative.

The latter is composed of:

• a drying loop (made of stainless steel, electrically traced)
• an automatically decomattable filter
• a stainless steel tubular condenser to condense the steam from the product of a product circuit

 

Drying into Overheated steam and product quality

Studies of mineral and biological products have shown that powders obtained by drying with overheated steam have different characteristics than those obtained by drying in air.

The powder obtained by drying with overheated steam is generally:

• Denser
• Agglomerated and less powdery
• More easily wettable
• Has different physico-chemical characteristics