[Gasification] What is the process he is trying to describe?

[Greg Manning]

 Steve, (and List)

 First off, I commend you.... Long "licky" blue flames tell there own story
(as well as your expert and informative homepages) I've been to your site
more than once, and like you, I'm heavily into woodchips (not blocks or
chunks).

I've gone the downdraft method, to run an engine and generator with excess
heat being taken from the engines water jacket, and prime heat being used to
"polish" the incoming woodchips down to 4-5%MC, (this leaves just enough
water to shift the process slightly, into that blue flame area, in my
configuration). Engine runs an AC generator.

 Would you say your system is in the 150,000 to 200,000 BTU mark ?
 How long a burn do you get off of 50lbs (22.6kg) of "wet" chips ?

 For your  2500 gallon storage tank, is it insulated? if so, to what R value
?

 Sorry if I'm asking lots of questions, but you are the first person I've
come across, that is solely doing woodchips....(that also has a website)...

 If you are interested, see my site on downdraft.

 http://www.inetlink.ca/a31ford/cgcmb/

 Greg Manning,



-----Original Message-----
From: gasification-bounces at listserv.repp.org
[mailto:gasification-bounces at listserv.repp.org]On Behalf Of Steve Redmond
Sent: Friday, December 15, 2006 11:15 AM
To: gasification at listserv.repp.org
Subject: [Gasification] What is the process he is trying to describe?


Hello, just found this link and this thread inadvertently through a web
search and thought wanted to comment on the suggestion by CAVM.

I'm not quite sure of the nomenclature below or the referenced photo, but I
wouldn't describe the VTHR furnace combustor as "turbulent."

While definitions of turbulence can vary from subjective to quantitative, I
tend to think of turbulent combustion chambers as requiring some kind of
blower or air injection above the embers, often at right angle to the draft,
or such high pressure updraft below and such shallow irregular fuel beds or
particles that turbulence is visible in the flame shape, if not in the
movement of the particles themselves.

The furnace I'm studying has a 26 inch deep fuel bed, generally runs without
secondary air admittance on negative pressure in the combustion chamber, has
been frequently run on natural draft alone, and the flames are characterized
by stable elongtated semi-transparent form, with visible stable vertical
striations tending to indicate laminar flow of the gasses. In fact you might
define the lines in the flames as laminae.

Whether it is true laminar flow is subject to more sophisticated analysis
than I can perform, so we probably should label this statement as
subjective. But the last thing I think of when I see these unusual and
characteristic flames is turbulent combustion.

It is difficult to photograph because of the low light level and low flame
luminance. As a result even a high ASA low light camera I've used provides a
time exposure, and exaggerates incandesence, thus blurring the slowly
changing flames and masking the vertical striations and distinctive flame
shapes

In this furnace, mixing of air and fuel gasses occurs beneath (prior to) the
ember line, so what burns is pre-mixed gas passing through gaps in the chip
bed. The consistent draft, low pressure differential and even distribution
due to the depth of the bed mean these gaps act as simple flat plate nozzles
and provide a smooth flow for the mixed gasses.

I tend to think of fluidized bed combustion as a sort of ultimate turbulent
method of chip combustion, and of the VTHR test furnace as an example of the
opposite. While some turbulence certainly exists in the imperfect nature of
any combustion chamber, it is not the mechanism that best characterizes this
one.

Best regards,

--Steve

Steve Redmond

On Thu, 7 Dec 2006 21:53:26 EST, CAVM at aol.com wrote:


>(http://www.sredmond.com/vthr_index.htm)


It looks like a turbulent top lit top burning combustor as has been
discussed a number of times on the stoves list.

A picture of an old one of mine is at:

http://www.wokingnursery.co.uk/agwaste/chipburner.html

AJH


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