[Gasification] using wet fuel-Steve Redmond

Sat Dec 16 12:00:13 CST 2006

 Steve  (and list).

 I gota ask...  how do you light it (the VTHR)....

My downdraft gasifier is lit through the back side of the tuyeres and is a
continuous burn unit (since incoming feedstock rests on top of the burning
stuff, it's very a liken to an upside-down version of your VTHR, (except
with the addition of tuyeres and a reduction throat.).

Greg Manning

-----Original Message-----
From: gasification-bounces at listserv.repp.org
[mailto:gasification-bounces at listserv.repp.org]On Behalf Of Steve Redmond
Sent: Saturday, December 16, 2006 11:29 AM
To: gasification at listserv.repp.org
Cc: gasification at listserv.repp.org
Subject: Re: [Gasification] using wet fuel-Steve Redmond

Hi Tom,

The grate temperature in my furnace is at ambient temperture throughout all
but the very last minutes of the burn.

It is made of 1/2" mild steel expanded metal mesh which would burn instantly
in even a small welding flame of a torch.

It is in as-installed condition after over 100 burns and 200 hours of
furnace use.

It requires no maintenance, except the sweeping through it of about 1/2" of
ash after a burn, left from 50 lbs of chips containing about 250,000 Btu HHV

It is not a continuously fed design, but a strict stratified batch burn. The
bed depth is irrelevant to the burn rate, other than limiting the air
supply. Think of a porous candle.

The base of the candle (the grate) is at ambient. The length of the candle
is irrelevant. The heat is all located at the top of the fuel. The
temperature differential is absolutely startified. A few inches below the
embers the furnace wall is at ambient. Therefore ceramics are completely out
of place here, since they crack with temp differentials like this. Mild
steel works well for the furnace walls.

You cannot add fuel to this furnace, without destroying the reaction, and
reverting to a smoky smoulder.

You light it at one end, and wait til it's done. If you want to put it out,
just add some fuel.

--Steve

----- Original Message -----
From: "Tom Miles" <tmiles at trmiles.com>
To: "'Steve Redmond'" <skiprock at earthlink.net>; "'A Gasification'"
<gasification at listserv.repp.org>
Sent: Saturday, December 16, 2006 11:58 AM
Subject: RE: [Gasification] What is the process he is trying to describe?

> Steve,
>
> The deep bed combustor you are using is reminiscent of the deep bed
burning
> studies that Ken Ragland and Mark Bryden did for whole trees in 1995-1996.
> You'll find a paper published in Energy & Fuels (1996) on the subject
which
> describes the mechanisms and the dehydration, gasification and combustion
> reactions involved. (See abstract and citation below).
>
> In St. Petersburg (formerly Leningrad) professor Pomerantsev did extensive
> studies of deep bed wood chip burning in the 1950s and 1960s. He designed
> furnaces and boilers based on deep bed burning which were built through
out
> Russia. Working with Russian combustion engineers and boiler manufactures
we
> improved the Pomerantsev furnace as part of a USAID funded project
> (2001-2005). Descriptions of the operation of the furnace are mostly in
> Russian.
>
> The design of continuously fed furnaces based on deep bed principles is
> problematic due to the very high temperatures that develop when you have a
> heavy bed of carbon burning at the grate. It becomes a blast furnace
> environment. The high cost of maintenance has meant that it has not been
> used very often in this country.
>
> Tom Miles
>
> Numerical Modeling of a Deep, Fixed Bed Combustor
> Kenneth M. Bryden* and Kenneth W. Ragland
> Department of Mechanical Engineering, University of Wisconsin Madison,
> Madison, Wisconsin 53706 Energy & Fuels 1996, 10, 269-275
> Received October 2, 1995. Revised Manuscript Received January 4, 1996X
>
> Abstract:
> A computational model to evaluate the anticipated performance
> characteristics of a deep, fixed bed combustor/gasifier utilizing whole
> trees as the source of fuel is presented. This combustor/gasifier is the
> heat source for a proposed steam-driven electric power plant utilizing
whole
> trees as the source of fuel. In the simulation model presented, hardwood
> logs 20 cm in diameter are burned in a 3.7 m deep fuel bed. Solid and gas
> velocity and CO, CO2, H2O, hydrocarbon, and O2 profiles are calculated.
This
> deep bed combustor obtains high energy release rates per unit area due to
> the high inlet air velocity and extended reaction zone. The lowest portion
> of the overall bed is an oxidizing region and the remainder of the bed
acts
> as a gasification and drying region. The overfire air region completes the
> combustion. Approximately 40% of the energy is released in the lower
> oxidizing region. The wood consumption rate obtained from the
computational
> model is compared with test results obtained from full scale testing. The
> wood consumption rate predicted by the model is 2630 kg/(m2 h) which
matches
> well the consumption rate of 2670 kg/(m2 h) observed during the 2 h test
> period of the field test. This corresponds to a heat release rate of 9.6
> MW/m2. The model is used to investigate the performance of the combustor
> under a variety of load conditions, fuel sizes, and moisture conditions.
>
>
http://pubs.acs.org/cgi-bin/abstract.cgi/enfuem/1996/10/i02/abs/ef950193p.ht
> ml
>
>
> WTE Plant (Ken Ragland to the Bioenergy List Discussion August 2005
>
http://listserv.repp.org/pipermail/bioenergy_listserv.repp.org/2005-August/0
> 10128.html
>
> Whole Tree Energy Power Plant (2005)
> http://www.mrec.org/confer/2005_WholeTreeEnergy.pdf
>
>
>
>
>
>
> --
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>

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