[Gasification] Empirical data on dryer systems

Sat Dec 9 05:11:45 CST 2006

Greetings Erik..

First off, Dryers are Ancillary equipment, to the gasification process (Even
though dry and consistent feedstock is paramount to gasification). In my
opinion, most of what is posted on this list is based in/on theory,
speculation, and some wishful thinking, NOT based on "hands on"  evaluation,
use, or "tinkering".

To me, this is fine, I am a "Hands On" person, I run and build gasifiers for
evaluation, modify, and re-evaluate, hoping to better the performance of the
said gasifier.

Now, to get back to the reply... Ancillary equipment, Even though very
important to the process as a whole, rarely gets spoken about here, there
are many areas, storage, transport, drying, sizing, & acquisition of
feedstock that without them, gasification would not happen, but alas, I
guess these areas are seemingly unimportant to most on this (and other)
lists, I guess they are "Dull" subjects... (So where is gasification,  up
there with "Pixel Chicks" that my granddaughter speaks of, this winter ?)
J/K

The Drying Process I use is simple, the sun and an inclined sheet of heavy
wire screen mounted in a large tiltable frame, chips are loaded onto the
screen, screen is inclined, and about 3 hours later, the chips start to
slide, or tumble down (moisture released, they are now lighter in mass, and
slide down), screen is tipped up, and chips are gathered into the back of a
tilting box, one ton truck, then the whole process is started again.

I know this is "simple", but very cost effective, even though somewhat time
consuming, (Generally I'm at the same location, splitting and bundling  cord
wood for resale, while the chips are drying).

Oh, the inclined screen.... it takes 3 bucket fulls of my tractors front end
loader, to fill the screen.....

Greg Manning.

-----Original Message-----
From: gasification-bounces at listserv.repp.org
[mailto:gasification-bounces at listserv.repp.org]On Behalf Of Rodenhuis, E.J.
(Erik Jan,Student TBK)
Sent: Saturday, December 09, 2006 4:25 AM
To: gasification at listserv.repp.org
Subject: Re: [Gasification] Empirical data on dryer systems

Hey all!

Is this topic not worth considering a thought? I hoped to get some get
some ideas and figures about dryers. Couldn't find much discussion on
this topic in the archives Or do you just not have a clue ;-)

Erik

-----Oorspronkelijk bericht-----
Van: gasification-bounces at listserv.repp.org
[mailto:gasification-bounces at listserv.repp.org] Namens Rodenhuis, E.J.
(Erik Jan,Student TBK)
Verzonden: donderdag 7 december 2006 13:46
Aan: gasification at listserv.repp.org
Onderwerp: [Gasification] Empirical data on dryer systems

Dear list,

For downdraught gasification of biomass generally is assumed that the
moisture content of the biomass is below 15% (wb). As the moisture
content of green wood is mostly higher and I have seen sawmills use
water-cooled band saws, you need to dry the wood waste before it is
suitable to gasify. Main options seem to be drum drying of flash/ring
drying.

Drum Drying:

-        Co-current to reduce fire hazard

-        Tair,in = 230 - 1100 degr. Celsius

-        Tair, out = 70 - 110 degr. Celsius

-        Empirical data on energy consumption 5 - 12 GJ/ton of water
evaporated, see poster presentation Mani:
http://www.biocap.ca/images/pdfs/conferencePosters/Mani_S_P1.pdf

-        General statements made in diverse publications: "high"
investment cost, "low energy use"

 Flash Drying

-        short residence time < 30 sec

-        drying at lower temperatures Tair,in = 100 - 650 degr Celsius

-        "low investment, high energy use"

A few other systems available:
http://barr-rosin.com/english/pdf/airstream.pdf

As we have will have with a downdraught gasifier with an ic-engine some
low quality waste energy streams are available, namely from gas cooling
(gas-gas shell-and-tube heat exchanger) and from the exhaust gases, I am
interested to know what the general ideas about which drying system
suits best. There might be some other criteria like the controllability
of the process and fire hazards.

Maybe there is somebody who can give some rule of thumb for investment
cost and energy consumption of a 1 ton/h drying system. When assuming
that we want to dry the wood waste (let's assume chips) from MCwet 30%
to a moisture content of 15% we need to evaporate 115 kg H2O/h.

Any hints or leads to good literature on the web on this topic??

Regards,

Erik Jan Rodenhuis

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