Ron, I think there is a mis-understanding.
My iCans ONLY have primary air air holes in the bottom of the iCan. I start with fewer and smaller until I get a distribution pattern, number of holes, and hole size that is well tuned to the fuel type, size, form factor, and other stove parameters - such as surface area of the pyrolysis zone. I place the iCan inside a second, larger, can for 1] wind protection; lateral heat loss mitigation; safely contain loose bits of red hot charcoal; and so forth. The question is to "vent" this outer can to allow primary air access or not. If the choice is to vent, then where to place the holes for the primary air to enter? These holes in the OUTER can, are NOT on the bottom of the outer can so as to allow it to safely contain any hot bits. So the question is simple, how much venting do you create and where on the side of the outer can do you put the vents. I agree that the ability to regulate the primary air flow into the iCan, the air flow to sustain the pyrolysis, would be very useful. My design goal is simply to create the easiest, and least expensive, introduction into the world of pyrolysis and biochar for young people. Sometimes good enough is just right. I also agree with and second your comments about Nat at World Stove. Cheers, Jock Jock Gill P.O. Box 3 Peacham, VT 05862 Carbon Negative Solutions (G) (802) 503-1258 On Dec 5, 2010, at 4:00 PM, [email protected] wrote: > Crispin, Jock, lists > > I think some of the ideas here may be counterproductive. See below. > > > ----- Original Message ----- > From: "Crispin Pemberton-Pigott" <[email protected]> > To: "Jock Gill" <[email protected]>, [email protected], "Stanley > Richard" <[email protected]> > Cc: "Discussion of biomass cooking stoves" <[email protected]> > Sent: Sunday, December 5, 2010 8:03:44 AM > Subject: Re: [Stoves] [biochar-policy] More on briquettes and pellets > > Dear Jock > > Very nice web pages and a well presented instructions provided by the link. > > I have a question relating to the iCan. > > Have you tried elevating the primary air holes in the outer can above the > bottom? I understand from the photos that the elevated holes are only on the > inner cans. > > [RWL: I would go in the opposite direction - put all primary air holes > on the bottom inner can surface - to get more uniform (vertical only) air > flow] > > The reason I ask is that I have found benefit from making the primary air > travel downwards at least part of the vertical height. The preheats the air > slightly and provides negative buoyancy reducing draft. As the inner can > starts to heat up, it increases the negative buoyancy because the inner can > is hotter and this interaction tend to self-regulate the power. > > [RWL: I don's see the value in reducing draft anywhere - we work hard > usually to achieve it. Re regulating power, I have always been amazed that > with a fixed primary air supply, the power level (as indicated by the > apparent rate of steam bubble formation) was amazingly uniform - over a full > hour. It is easy and cheap to control power levels through controlling > (only) the amount of primary air. I think turn-down ratio is a very > important parameter that needs a lot more work. No gas or electric stove (I > presume propane, ethanol, etc) manufacturer would give you less than about > 3:1 for turn-down ratio. This parameter I think is one of the main reasons > we are going to see increased stove use of the discarded fans used for > cooling computers. >
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