High and dry
Demand for high efficiency spray dryers has increased in recent years, leading to the development of product specific applications of spray drying technology, according to Anhydro, an engineering company that is part of Ivensys APV.
Demand for high efficiency spray dryers has increased in recent years, leading to the development of product specific applications of spray drying technology, according to Anhydro, an engineering company that is part of Ivensys APV.
It is important to minimise deposits within the drying chamber, particularly in the case of high value products. Deposits are caused by four main factors: electrostatic forces; stickiness due to moisture in the powder; stickiness due to thermoplastic properties in the powder; and deposits on horizontal surfaces.
There are several ways of reducing these deposits:
• Pneumatic hammers are an efficient means of reducing deposits caused by electrostatic forces, but are not so effective on wet deposits, where size and shape have a significant impact.
• The air broom is a rotating pipe with fine slots along its entire length. The high velocity in the slots results in a mechanic blow, which removes most sticking particles.
• The wall sweep system consists of a number of tangentially oriented slots located in the drying chamber wall. These wall sweep slots are supplied by preheated air at moderate to high pressure.
The methods are well-known and proven solutions. The challenge, according to Anhydro, is to use them in combination, which optimises efficiency for new product applications.