[Gasification] Empirical data on dryer systems

Tue Dec 12 18:30:05 CST 2006

Dear list, 

For the ones that took the time to reply on my question, it is much
appreciated! I will shortly react on some of the things said. 

To Greg: I think that of all the 'dull topics', the drying is
particularly important, because we can think of some waste heat streams
when using a gasifier with ic-engine. When presenting the process of
biomass-to-energy as a black box (as the ones that make a living out of
designing and selling systems have to do), some flexibility regarding
the biomass used (both morphology and moisture content) is very
desirable. A commercial system needs to handle the biomass stream as it
occurs. We can do this by installing dryers or further integrating the
drying and gasification process (as done by DTU Denmark with the 2-stage
systems). (Thanks Rex, for reminding me). From this view drying,
gasification and tar removal connect to each other.
For small systems solar or hybrid systems might be useful and suiting
the drying needs, for a bigger scale it will consume to much storage
capacity and take to much fuel handling. I think everyone agrees on
that.

To Mark L.: the big drawback of counter-current drying with hot air
stream is a bigger fire hazard. Please explain your vision regarding
possible fire hazards.

To Tom: Thanks for your reply concerning different drying systems, as
you probably expected it leads to a lot new questions. The suitability
of a particular drying systems seems to depend on the morphology of the
biomass and the needed scale of drying. Maybe it would be useful if we
could line up the different technologies in a diagram with on one axis
the particle size and on the other the scale of drying (volume/mass of
biomass, or maybe better: mass of water to evaporate per unit of time).
I came across a few reports on drying systems, but most of them are
qualitative and not quantitative. Maybe some info is freely available,
but I did not find good figures for energy consumption for the amount of
water to evaporate for different systems. If somebody knows some good
sources, please recommend them through this list. 

To John: I like to know some more about your rotary drum dryer. What
capacity? You say you use hot air, at what temperature? Do you use
exhaust gases or another waste heat stream?

To Darren: In the publication about the CLEW project from Cleland and
Purvis www.epa.gov/appcdwww/apb/CLEW.pdf this pilot plant is evaluated.
>From this publication: "... consistent bulk drying of hogged wood (25 to
40% moisture, wet basis) to 10 to 13% moisture with exhaust/air at ~ 193
degrees C (380 degrees F);~ 4 hour residence time...". Average feeding
of gasifier: 1800 lbs of dried wood/hour (816 kg/h). It gives a good
idea of what is possible with the system.

To Marc S.: My compliments on the informative site. The advantages of
the technology are given. One strikes the eye: "fourth times as
efficient as a traditional rotary dryer". I am very interested what
numbers this claim is based on. Is it possible for you to supply these
numbers? 

Thanks again and regards,

Erik

-----Oorspronkelijk bericht-----
Van: gasification-bounces at listserv.repp.org
[mailto:gasification-bounces at listserv.repp.org] Namens Marc Smith
Verzonden: dinsdag 12 december 2006 21:12
Aan: gasification at listserv.repp.org
Onderwerp: Re: [Gasification] Empirical data on dryer systems

Dear List,

Traditional horizontal dryers are extremely inefficient; maybe cheap but
depending on the waste being treated many other factors come into play.
We
currently have over hundreds of plants in operation using cyclone drying
technology. 

 http://www.kleanindustries.com/s/CycloneDryers.asp?ReportID=126496

Marc

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