A rotary drum dryer is a long horizontal cylinder carried on two riding tyres and driven through a gear ring. Wet material enters through a screw conveyor at the hot end, meets the combustion gas from the furnace, and travels the length of the drum while it dries. At the discharge end a cyclone drops the dry product and a bag filter or wet scrubber handles the exhaust.
What most buyers never see is the inside. Welded to the shell are spiral lifting flights, and they do the real work: as the drum turns, the flights scoop material up the wall and drop it back through the gas stream as a curtain. That curtain is the heat exchange surface. Flights that are worn, blocked or badly pitched give a wet load out of a hot drum, and no amount of extra fuel fixes it. Slope and speed control how long the curtain stays in the gas: a steeper drum moves material through faster and drier material needs a gentler slope.
Temperature is a balance, not a setting to maximise. Inlet gas that is too hot scorches the surface of the wood, seals the moisture inside and creates a real fire risk in the dust collector. Outlet temperature tells you more than inlet: if the outlet stays low, the material is still wet, not cold gas.
Two things are worth preparing before the dryer arrives. First, screen the material — oversize chips and knots stay wet while everything around them dries, and they come out as a wet lump. Second, decide the heat source: wood waste from your own yard is the cheapest fuel, gas and diesel are the convenient ones. Every drum dryer also needs its dust collection designed with it, because dry wood dust in a hot gas stream is the part of the plant that must never be an afterthought.
Zhengzhou Weiwei Machinery has been manufacturing biomass and feed machinery since 1980, holds CE and ISO9001, and supplies dryers, crushers, mills and complete lines.
Tell us the material, its moisture now and the moisture you need, plus your daily tonnage and available fuel. We will size the drum and the furnace to match.
