[Stoves] Fire Stump / stump-incuts

[Fireside Hearth]

Hello Crispin, 

         I really do appreciate that you are taking so much time to help me understand. 
 
                     Our design is not that out of the ordinary where primary and secondary combustion and air delivery are concerned. I have developed a pin wheel of sorts which can be rotated to the right or left opening or closing air channels. This allows me to shut down one or both depending on the stage of the fire. My secondary tubes are preheated from the bottom of the stove up to the bottom side of our combustor. Both the lower burn chamber and the combustor are built to promote as much turbulence as possible for good mixing of air/fuel. Once through this process the spent exhaust enters an upper chamber where some combustion will continue but most is complete during the passing through the combustor due to very high temperatures. we insulate very heavily sides of the stove for close clearance as well as internal temperature. Most of the usable heat is focused out out the glass door and cook top.
Again, thank you....R&B

From: crispinpigott at gmail.com
To: stoves at lists.bioenergylists.org
Date: Thu, 28 Jul 2011 22:28:16 -0400
Subject: Re: [Stoves] Fire Stump /  stump-incuts



Dear Roger >Why isn't the secondary combustion process be applied in cooking? or another angle why could these appliances do both jobs? Secondary and even tertiary combustion is commonly applied in stoves. In fact even an open fire has secondary combustion of the gaseous products that evolve from the solid fuel. In some cases, the secondary air enters the combustion area together with the primary, and sometimes it is brought in via a separate channel (esp through a number of holes). On occasion the secondary air is blown in with a fan or a chimney (which is a natural draft ‘fan’ in that it provides something like forced air). There are combustors that provide most of the secondary air with the primary air, and add a small amount of secondary (sort of ‘supplementary’ air) above the primary combustion area. An example of this the GTZ 7 series stove (now renamed GIZ 7 because they changed the name of the organisation). It has a grate setup that allows most of the needed secondary air to pass through a thin layer of burning coke where it is preheated and partly used. There follows a small set of holes (about 8) that let in just enough secondary air to complete the burning. This has the result that the amount of air pissing into the fire is minimised, but enough. The result is a very high flame temperature. Stoves that are known for having very restricted primary and lots of secondary are the gasifiers like the CampStove from Tom Reed. His stove has a small fan and most of the air, nearly all of it, is secondary. There are natural draft gasifiers and pyrolysers (that deliberately make char) which accomplish the same thing using slightly taller stoves that basically have a short chimney section inside.  They are all built to create gases then burn them at a secondary stage. The GIZ 7 stoves can arguably be analysed as having three sets of air supplied: primary air to devolatilise the coal or wood, then secondary air preheated by passing through a thin layer of nearly burned fuel, then preheated secondary air that passes through a set of holes about in the middle of the flaming area (combustion chamber). This last ‘air’ is tertiary in that it is one of three supplies, however there are only really two burning areas: the primary one and the secondary one. Not every stove fits easily into simple categorisation. I would be interested in hear from you what has been built. Is the primary or secondary air deliberately pre-heated before entering the fire? Do you control the amount of secondary air during the burn (for example closing it off when the fire gets low(er)? RegardsCrispin 
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