Hybridized RF/conventional web drying offers boost to productivity
Don Horne
Radio Frequency energy has the unique ability to heat a wet substrate throughout its entire thickness with zero lag-time for thermal conductivity from the exterior surface, typical of conventional drying systems.
Often, up to one third of the length of a conventional web dryer is used simply to preheat the web before any real drying is accomplished. For thermally sensitive substrates, the preheat time is even longer.
By adding an RF preheat stage to a conventional drying line, sensible heat, up to the vaporization temperature, can be immediately imparted throughout the thickness of the web such that 100 per cent of the conventional dryer’s length can be used for evaporation, which greatly increases line speeds and productivity. Additionally, the heat transfer is accomplished without the need for excessively high temperatures as the RF energy is generated by the polar water molecules in their liquid phase below 212ºF.
Additionally, because RF energy produces no greenhouse gasses, each additional unit of production provided, has a lower percentage of greenhouse gas when added to a conventional gas-fired dryer making a more eco-friendly final product. Systems have proven ideal for drying or curing aqueous based solutions on cellulose webs, non-woven polymeric battings including medical foams and other insulative continuous products.
New systems are available in a wide range of widths and power levels. Sample testing is also available from the manufacturer.
