Greg Thanks for sharing.
I want to try a few ideas for myself to see if this is indeed possible on the small split logs I can produce locally. Our heating needs, and indeed modest on account of the mild climate here, but I would like to find an efficient solution for all the thousands of acres of neglected coppiced hardwood. Cast iron victorian stoves may be quaint, but I am sure there are ways to improve the overall efficiency with radical redesign. The main burner/heat exchanger on our 24kW gas boiler is no bigger than a gallon paint tin. Perhaps there is design lesson to be learned here Anything to reduce mechanical handling and processing of wood fuels has to be a step in the right direction Happy New Year Ken On 26 December 2013 19:22, Greg Manning <[email protected]> wrote: > Greetings Ken, and list members. > > Ken, I'm going to point you to a video of the "underside" of a whole log > (or split) "cordwood as we call it here" stove that is a downdraft gasifier. > > I can speak at length privately, however only somewhat on list, as this is > a proprietary design. > > Here's the link to the video: > http://youtu.be/DNYCfgEdYpg > > Greg Manning > > > On Thu, Dec 26, 2013 at 12:59 PM, Ken Boak <[email protected]> wrote: > >> >> Happy Christmas to the gasification list. >> >> At this time of year, during the festive holiday season, I get a bit more >> time to manage the running of our woodstove, as it rapidly warms the room >> and produces a cheery effect. >> >> Our property is fairly conventionally heated by natural gas, but a few >> years back, I took the decision to invest in a woodstove with back-boiler, >> to provide an alternative or back-up to the gas fired system. >> >> The woodstove has a flat steel tank at the rear, the "back boilerr", in >> place of a couple of the firebricks lining. This circulates heated water >> entirely by the thermosyphon principle to a radiator located in the >> bedroom/workroom directly above the stove. So in effect the stove heats the >> living room/kitchen area directly, and the room upstairs by circulating >> hot water. >> >> No electricity is required for circulation, and if worse-case we had an >> extended power outage, this stove would provide heat and comfort in the two >> main occupied areas of the house. Stoking it and attending it is often more >> interesting than what is being shown on TV! >> >> With a few days off work, I have had time to monitor the stove and make >> some assessments of its overall performance. Its a fairly traditional >> stove, a rectangular box,, made from bolted together cast iron panels and >> partly lined with firebrick. It's described as a multifuel stove - having >> been supplied with a cast iron removable grate for burning coal - which is >> not used when burning wood. It's approximately 24" wide, 12" deep and 18" >> tall. >> >> In the UK, a common size for firewood logs, intended for the domestic >> woodstove is about 10" (254mm) long, and equal to a 1/4 round taken from a >> limb that may have been 5 or 6" in diameter. The reason for this is that >> there is a lot of coppiced hardwood, which has become mis-managed in the >> last 20 years, so there are a lot of trees with 6" diameter shoots. The >> popularity of the "firewood processor" machine, means that a lot of this >> wood is now coming on the market as domestic firewood, and sold to >> suburbanites at vastly inflated prices (about $0.50 per kilo). >> >> I am burning a mixture of kiln dried Silver Birch, and air dried other >> species which includes ash, oak and sweet chestnut. The silver birch splits >> well and makes excellent kindling. One log is split into 8 or 10 kindling >> sticks and these are built into a pyramid around 2 or 3 sheets of scrunched >> up newspaper. Lighting is quick and easy - as the birch is kiln dried, and >> within 5 minutes you will have a roaring fire and the larger logs can be >> added. >> >> The logs have an average weight of approximately 1 kg. I have found that >> a normal burn rate of these is two per hour. I burn two at a time, and >> each hour, add a further two to the burning char bed from the previous >> logs. With firewood having a calorific value of approximately 4kWh/kg - I >> estimate the fuel input is in the order of 8 to 10kW. >> >> Of course, with a traditional stove, so much of the heat energy is lost >> up the chimney, and goes to create the draft. The efficiency of the stove, >> might be in the region of 50% - somewhat better than the open wood fire. >> It occurred to me that by way of a 2 stage gasification process, it would >> be possible to increase the overall system efficiency, resulting in less >> wood consumption, or more heat output per log. >> >> This leads to a question - is it possible to design a gasifier aimed at >> handling whole log gasification - where a log is 10" long and no more than >> 6" across? Can you recreate the temperatures, turbulence and reactants, >> found within the combustion zone of the woodstove, and use this to >> thermally process a single firewood log, at the rate of one every 30 >> minutes or so? >> >> I've had some ideas on how this can be done, effectively using a length >> of 6" diameter stovepipe/fluepipe to make a compact gasifier. Logs would >> be loaded in from the top, and the length of the pipe chosen to perhaps >> hold 4 logs at any time - about 1m (40") tall. The bottom log would sit >> in the combustion zone - so the end of this log is constantly under the >> action of the air nozzles. The logs above are subjected to the elevated >> temperatures and begin to pyrolise, char and split on their descent down >> the tube. >> >> Beneath the combustion zone would be a fairly conventional hearth, and >> reduction zone, with the char supported by a grate below that. For an >> overall idea of the system - think of HS Mukundas open top gasifier. >> >> Use of twin-wall stainless flue pipe would allow the air to be pre-heated >> in the outer annulus - adding to the overall efficiency. The hot syn-gas >> could be burned in whatever appropriate burner geometry deemed necessary >> for either radiant space heating or water heating with a suitable heat >> exchanger coil. >> >> I hope to try to build a prototype of this over the next 10 days (a >> working gasification holiday?) and to see whether a log can be reduced in >> this manner. If all that is needed is heat, then the restrictions to >> produce a tar free gas need not apply. If one can use whole logs, without >> having to resort to woodchip - then this will be a considerable saving in >> mechanical handling and wood processing. >> >> At the end of the day - this gasifying stove needs to be as simple to >> operate as the existing woodstove. Reloading with a couple of logs each >> hour, and no sophisticated need for fan- forced draft or electricity to >> operate. Draft would come from the chimney as per now - about 25 to 30 >> feet, 6" diameter. >> >> If anyone has experience of something similar - please let me know. >> >> >> Happy Holidays >> >> >> >> Ken >> >> >> >> >> >> _______________________________________________ >> Gasification 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/gasification_lists.bioenergylists.org >> >> for more Gasifiers, News and Information see our web site: >> http://gasifiers.bioenergylists.org/ >> >> > > _______________________________________________ > Gasification 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/gasification_lists.bioenergylists.org > > for more Gasifiers, News and Information see our web site: > http://gasifiers.bioenergylists.org/ > >
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