Crispin, I find that we agree on two key points that others do not seem to.
1. Keeping the fire in the combustion chamber; 2. That only a SMALL amount of primary air is needed in a well tuned TLUD. I generally see way too many and too large primary air holes used. I tell students to start with too small primary air holes such that the pyrolysis fails. I then have them enlarge the holes in 1/64th drill bit increments. Occasionally I suggest adding a very few more holes. Pretty quickly they find the smallest amount of primary air that works for the given biomass. It is easy to make holes larger, but a real challenge to make them smaller ;-) My goal is complete conversion of all biomass to charcoal, no unconverted bits in the final results. I also aim for a the best yield that also passes the usual simple quality tests, such as Hugh's no soap test, no floaters in the quenching water, little ash - clear water after quenching, not milky, etc. It is very good to find another who shares my views on location of combustion as well as the amount of primary required. But pardon my ignorance. In the last paragraph you mention EA, which I take to be excess secondary air? When you talk about range, range of what? I will get one of my heating professionals to measure my stack gases when I get a chance latter this Spring. Many thanks. Jock Jock Gill Marketing & Communications Whitfield Biochar, LLC Burlington, WA www.whitfieldbiochar.com Cell: (617) 449-8111 Sent from my iPad On Feb 26, 2013, at 12:05 PM, Crispin Pemberton-Pigott <[email protected]> wrote: > Dear Jock > > Only taking up one issue: > > >Further, reducing the secondary air increases the heat in system and > >increases the pull on the primary air = faster pyrolysis. But it also > >reduces the turbulence promoted by vigorous secondary air. > > The turbulence is a consequence of the shape and orientation of the incoming > air ducting. You can’t get a good system working and then drop the secondary > air without compensating for the mixing issues and the primary air flow, as > you pointed out. The increase in temperature (from the drop in excess air) > increases immediately the heat transfer efficiency and reduces CO and PM > (until the ‘bottom is reached’). > > If the draft is strong, you need only a tiny amount of primary air. To burn > clean you have to decrease the EA as much as possible. For biomass you should > be looking in the 70-100% range for a small stove (O2 in the exhaust @ 8-10%). > > Regards > Crispin > > _______________________________________________ > Stoves mailing list > > to Send a Message to the list, use the email address > [email protected] > > to UNSUBSCRIBE or Change your List Settings use the web page > http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists.org > > for more Biomass Cooking Stoves, News and Information see our web site: > http://www.bioenergylists.org/ >
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