Faced with the ongoing issue of the proper disposal of organic waste, a new technology has been developed that could be the answer to manufacturers, producers and municipalities that seek "friendly" disposal methods.
For example, in a dry state, organic waste products are
usable as alternative fuel or can be transformed to charcoal, but they normally
have high initial moisture content and need long residence times during drying.
The resulting products often are non-uniform in shape and size, contaminated, sensitive
to heat, prone to ignition or emit volatiles.
For drying green waste, the use of either rotary drum dryers,
belt dryers or fluid bed dryers has been state of the art. But those types of
dryers may have the disadvantages of insufficient product-residence times,
partial overheating of the solid, inability to use low temperature secondary
heat or poor solid mixing.
To avoid such problems, Almo Process Technology Inc., Middletown,
Ohio, has developed the rolling bed dryer.
“The use of low temperature waste heat for drying becomes
possible, says Tom Schroeder, Almo president. Waste heat is abundant, especially
at many recycling companies and municipalities, he says.
In the rolling bed dryer, the non-uniform bulk material is
steadily and homogeneously mixed, staying in the dryer for long retention times,
despite the equipment's compact design, Schroeder says. "Even irregular
shredded organic waste or unwieldy bulk like branches and tree cuttings, bark
and leaves or unevenly cut wood chips is conveyed by the dryer in a reliable
way,” he says.
installed the first dryers at Topell Energy in The Netherlands, where two of
the units convert wood waste into charcoal by a pyrolysis process called
torrefaction. The charcoal is pelletized to be stored, transported, and then
used at power stations to make electricity.