GAS-L: Re: Drying of Sawdust

[Reedtb2@cs.com]

Dear Grover et al:

The spiral slide around the chimney is VERY ingenious. 

I remember visiting a sawdust pyrolysis plant in which there was a spiral 
vibratory chute.  With the correct pitch and an off center motor-shaker (or 
could be magnetic drive as in vibratory feeders) the sawdust walked UP the 
chute.  If the chimney was in the middle, the hottest part of the chimney 
would contact the wet sawdust, then dry it as it walked UP, and the sawdust 
would then exit the chute at the low temperature part of the chimney, thus 
avoiding "blue haze" (a counterflow arrangement rather than co-flow).

Nice to hear from Prof. Grover, one of our most ingeneous biomass energy 
implementers recently starting a new "midlife" (we hope) career.  I hope with 
part of the career he will continue to give good advice here at CREST.  He 
also turned out many good students in biomass.  

Yours truly,            TOM REED        BEF





In a message dated 1/15/00 4:32:32 AM Mountain Standard Time, 
pdg@del2.vsnl.net.in writes:

<< 
 Sub: Drying of Sawdust
 
 
 Elsen L. Karstad
 
 
 One way to dry sawdust without using a fan is to use the heat from the 
chimney of the furnace where volatiles are burnt and use its hot surface.
 
 
 The technique is to provide continuous spiral slide around the chimney with 
a slope having an angle of about 500 (equivalent to angle of repose for 
sawdust for sliding on an inclined surface). This spiral is covered with 
another circular jacket.
 
 
 The sawdust is added slowly from the top and collected at the bottom. The 
extent of drying depends upon its initial moisture content, rate of sawdust 
addition, chimney temperature at its wall and the time the saw dust spends on 
the spiral (Residence time ). To start with residence time of 20 minutes may 
be taken.
 
 
 If the spiral is flushed with the outer wall of the chimney it also acts as 
heat transfer fin conducting heat and supplying it the contact sawdust. The 
space between fins should be sufficient and only 10 - 15 % of the volume 
should be filled by saw dust. The rest of the empty space is meant for water 
vapour and natural convective air to escape. Hope you find this information 
useful.
 
 
 
 
 Prof. P.D. Grover 
 
 (Ex. Head Chem. Eng. Dept. IIT Delhi)
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