Air dryer has several twisted pipes which are in vertical placement. This dryer has advantages of direct heating, fast drying, easy installation and less land occupation. The output is usually less than seven hundred kilograms. It can dry wood powder whose moisture content is at most thirty percent.
Drum dryer is one of the simplest and easiest biomass energy drying equipment. The pipe is long and straight, which is more easy to transport and install. It can deal with wood powder with eighty percent moisture content. Its output is around one ton.