[Stoves] [MHAtech] Re: Top lit updraft combustors

[Tom Miles]

In our enthusiasm to make char let’s not claim high yields from gasification unless we can identify the qualities and composition of the char. 15% to 20% is typical. Yields above 20% would suggest a high level of tars, or labile carbon, or ash, which is fine if that is the carbon you want. If you want hygroscopic char, then you have get below 20% volatile matter. When you do that your carbon yields go down to the 15%-20% range. Maximum theoretical yield from wood pyrolysis is about 33% (Antal, 1983?) It has been stated here before many times but when you add air (gasification) some of the oxygen reacts directly with the carbon, converting it to CO2 and providing heat to drive the gasification process. Most of the air probably burns CO, H2 and other gases from heating the fuel.

 

Tom 

 

From: Ronal W. Larson [mailto:rongretlarson at comcast.net] 
Sent: Monday, December 18, 2017 8:16 PM
To: Tom Miles <tmiles at trmiles.com>; kgharris <kgharris at sonic.net>
Cc: Discussion of biomass <stoves at lists.bioenergylists.org>; Law, Steven (MOECC) <Steven.Law at ontario.ca>; Crispin Pemberton-Pigott <crispinpigott at outlook.com>; Sauve, Terrence (OMAFRA) <Terrence.Sauve at ontario.ca>
Subject: Re: [Stoves] [MHAtech] Re: Top lit updraft combustors

 

Tom,  and ccs (and adding Kirk Harris - who has reported some high energy-in-char numbers)

 

              

 

              1.  Can you clarify what you mean by ”similar gasifiers?   I certainly agree that 25% energy capture in Norbert’s system would be hard - but I don’t think he is calling his present heating approach a “gasifier”

 

              2,  I think/hope Kirk is over 25% char by weight (over 30+% energy) char for his TLUDs.  The numbers I have been citing are only TLUDs - which would be a major shift for Norbert.  Stopping a “burn” to maximize char needs a name.

              

Ron

 

 

On Dec 18, 2017, at 5:15 PM, Tom Miles <tmiles at trmiles.com <mailto:tmiles at trmiles.com> > wrote:

 

Similar Gasifiers get 15%-20% yields. I would question 25% or more. 

T R Miles Technical Consultants Inc.

tmiles at trmiles.com <mailto:tmiles at trmiles.com> 

Sent from mobile. 


On Dec 18, 2017, at 6:50 PM, Norbert Senf <norbert.senf at gmail.com <mailto:norbert.senf at gmail.com> > wrote:

On Mon, Dec 18, 2017 at 6:22 PM, Ronal W. Larson <rongretlarson at comcast.net <mailto:rongretlarson at comcast.net> > wrote:

[RWL:  I sometimes hear of reverse flow in chimneys.  Not  to worry in your systems?

 

It can be an issue with cold starts, but is not a safety concern because there will be noxious smoke, which is obvious. There are various workarounds/fixes for this

In normal operation, the heater is warm, and will keep powering the chimney draft long after the fire is out until all the heat is sucked out of the mass.

During the charcoal phase, when the thermal mass has been heated, chimney draft is never an issue.

This is quite the opposite of "airtight" stoves that you fill with wood and then turn down for an overnight burn. During the middle-of-the-night charcoal phase, draft can get low and house depressurization can cause a reversal and CO spillage. 

 

[RWL:  No - medium .  I almost never varied a percentage point from 25% by weight (multiply by about 30/18 to get energy).  But we hear 30% by weight sometimes (low temperature char).

 

Thanks, interesting to know what a good number for yield would be ...............N



-- 

Norbert Senf
Masonry Stove Builders
25 Brouse Road, RR 5
Shawville Québec J0X 2Y0
819.647.5092
www.heatkit.com <http://www.heatkit.com/> 

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