Impingement drying is a new, very efficient way of drying the paper web. The drying medium of impingement drying is air. Very efficient drying is obtained by blowing hot, high velocity air onto the sheet and circulating the air back to the dryer. The air is normally heated up by gas burners, which causes less CO2 emissions than e.g. combustion of coil.
This method yields considerably higher specific evaporation rate than conventional cylinder drying. The evaporation rate of cylinder drying, 20-40 kg H2O/m²h (according to TAPPI), increases to a level of about 100 kg H2O/m²h (per dryer area). Thus several times higher evaporation rates than those of the conventional cylinder drying are achieved.
Impingement drying technology is especially efficient at the beginning of the dryer section where the cold web easily attaches to the hot cylinder surface, which causes runnability problems. In this area the best results of impingement drying are achieved.
Metso impingement drying offers an advanced and sophisticated way to increase machine production, efficiency and end product quality, in an energy-efficient way, on both new and rebuilt paper or board machines.
For impingement drying we have three different solutions:
- OptiDry Twin
- OptiDry Vertical
- OptiDry Horizontal
"We are very pleased with the fact that the OptiDry Vertical dryer achieved the guaranteed drying capacity so fast and that the start-up was so easy."
Steinbeis PM 4
The OptiDry dryer enabled production increase without increasing the machine length. We are very satisfied with this concept,” says Jukka Kotilainen, Production Manager of PM 8.
UPM Tervasaari PM 8