22 May 2002

B4-25 Energy-efficient evaporative dehydrator based on steam heat pump technology


An energy-efficient dehydrator was conceived for the purpose of the watery-waste recyclings.
The steam generated from preheated wastes is compressed to condense at an elevated temperature
to reheat the wastes. The condensate is drained out by a steam trap. This is a kind of heat pump
using H2O as a working fluid in an open cycle.
An experimental dehydrator was prototyped to investigate the performance characteristics.
The steam compressor used was an oil-free wing-type driven by a 7.5 kW-motor. A steam condenser
acting as a rotating agitator was tried to improve heat transfer. Measured distillation rates
and COPs were close to the predicted, 100 kg per hour and 10 respectively.
Lees of shochu (distilled wheat spirits) was dried from the initial water ratio of 9.00 to 0.13.
Sum of the latent heat of vaporization divided by the integrated electricity consumption was approximately
7, that is translated into the reductions to less than one quarter in the primary energy
consumption and in the carbon dioxide emission when compared with the conventional dryers.