On Jul 25, 2010, at 7:28 AM, [email protected] wrote: > > Hi Brian, > > Boy does this sound familiar! I posted the same question about 3 years ago. > I haven't seen Greg's response yet so maybe I am reitering but here is my > take. First I would check to see how much tar is in your piping.
Unfortunately, quite a bit. Our first couple of efforts were, to use your word, UGLY! And that stuff is so stuck/set in place it will never come out! But how much is continuing to accumulate? I can't say for sure, given what is there from the first couple of runs, but I don't think much, if any more is accumulating. > If there is no tar declare victory and move on. This is what an UGLY tar > flare looks like: > > http://groups.yahoo.com/group/WoodGas/photos/album/118107394/pic/1187813934/view?picmode=&mode=tn&order=ordinal&start=1&count=20&dir=asc Hmm, couldn't get to that video. > > This made tons of tar. Yours looks a little better. > > What size and quantity of nozzles are you running? We have 26 ports at 3/8-inch diameter each. > My first thought is to smash them flat Creating "nozzles" for our input is/was beyond our skill set. We aren't engineers and our financial resources are limited. So from our naive and cheap point of view, nozzles were a Bad Thing. We went for simple and our air input manifold simply has holes drilled out as our input ports. We like simple. > or swap them out for smaller ones to increase your blast rate. You want the > oxygen to penetrate to the centerline of the machine to burn any tars that > are shielded by CO2. Hmm. Have no way to know if our air is getting all the way to the center of the fuel column. Our TCs inside the firetube are installed such that the tips of the TCs penetrate the fuel column by 1.5 to 2.0 inches. Whether they've been bent down by the downward flow of wood fuel, I don't know. I'll look specifically for that issue next time we burn down our fuel load far enough to see the TCs inside the firetube. However, since we're delivering air under pressure, current runs are around 40 psi (2.76 bar), I'd guess were getting through to center but I truly don't know. We want to experiment with a little higher pressure but we need to tweak our air delivery design to be able to do that. > > Next I would try reducing your nozzle tip diameter. I started with mine WAY > to big. Bigger increases the amount of stuff pyrolizing thus making more tar > gas for the amount of oxygen available to burn it. Tar gas is the "heating > oil for reduction", but too much can gum up the works just like an overly > rich home heating furnace. > > Lastly I would lower your nozzles closer to the restriction. Our ports are IMMEDIATELY below our hearth restriction. But our restriction isn't much. We were/are very adverse to anything that might create a fuel bridging issue so we really only gave the hearth restriction a small token nod. > Your temperatures look pretty good so you don't need much distance for > reduction. I do everything above the restriction(yes, my rig is not the > norm) and only run 14 inches for combustion and reduction. The vertical distance from our air input ports to the floor of the grate is about 7 or 8 inches. -brian > > Stephen > -----Original Message----- > From: Brian and Cara Paasch <[email protected]> > To: Discussion of biomass pyrolysis and gasification > <[email protected]> > Sent: Sat, Jul 24, 2010 10:08 pm > Subject: [Gasification] Can't get to blue flare > > > Hi all, > We recently started testing our downdraft gasifier. So far we haven't been > able > o move from a yellow/red flare to a blue flare. I've searched the > gasification > rchives and as best I understand, we need more air running through our > system. > s that correct? We've increased the air over previous test runs but our > flare > s showing no sign of going from yellow to blue. > As shown in this video: > http://www.youtube.com/watch?v=9X6WPlhyOWc&feature=channel > we have a pretty clean flare, no obvious smoke, but day or night, our flare > is > ost certainly NOT blue. > Anything else we should be considering? > Thanks! > -brian > PS Our wood moisture content is less than 15%. > _______________________________________________ Gasification mailing list [email protected] http://listserv.repp.org/mailman/listinfo/gasification_listserv.repp.org http://gasifiers.bioenergylists.org http://info.bioenergylists.org
