…just making sure that I’ve got the theory straight. Am I correct in assuming that the charcoal gas must leave the charcoal bed cool? If the surface temperature gets too hot, I’m assuming that:
*Hot CO, in the absence of excess carbon, will become carbon dioxide and soot as it cools.
*This is a limiting factor in the running time of a given gasifier.
*Any attempt to harvest the heat from the hot gas is doomed- any heat capture needs to be from the charcoal itself- a poor conductor.
I’m trying to steer away from “It can’t be done because…” towards “The technical challenges are…”
Hi Brian, Terms like hot and cold are so relative! Hot CO in the absenced of excess carbon will stay CO. If it gets up to 2,000F, what happens to it? I don’t know. I do know what will happen if you mix it with O2 though.
Why do you want to harvest heat from the gas? If you want heat, grab it from the engine or from the charcoal making process.
Just my $0.02 worth!
Where would the CO get the extra oxygen to go to CO2? If there is no oxygen left in the gas stream (which there shouldn’t be) after the CO leaves the charcoal bed, it pretty much has to remain CO.
It looks as though you got some quotations from somewhere. I dont’ see the validity of the quote that excess CARBON is gonna cause CO to revert to CO2. Seems to me that you’d have to get C2O or something like that, which just does not work out,valence-wise.
I don’t understand the quot about “–harvest the heat from the hot gas is doomed—” either. I have a Chinese gasifier (n wood chips) that uses water for cooling the gas. My system’s heat exchanger heats about one gallon of water per minute from about 50 degrees f to about 100 degrees f. I wouldn’t see any problem using that water to fill up a hot tub or swimming pool. I 'spose there could be problem if you were recirculating water or air through a cooler where you couldn’t wring enough heat out of the transfer fluid to keep the temperature down whete you needed it.
Intersting premises. The internet just like on print media can be tricky as some very smart fellows with thier earlier beliefs once stated/printed openly then get stuck with them no matter how much they may later shout out, “I know better now. I was wrong back then.” I’d sure like to be able to deleate about half of the earlier stuff I’ve put up concernign gasification.
CO is very unstable. CO2 is very stable. Either can be converted to the other with an energy change help. Heat IS an energy input. Compression turbulence an energy input. Forcing either of these gases past a turbulence edge at sonic velocities such as a pipe inlet/outlet edge or a throttling valve edge will cause an energy input and can cause a reversion or conversion from one to the other. This can be enhanced with the presence of additional extra oxegens or carbons. But, since both CO and CO2 contain these molocules already, extra is not absolutly needed.
Example: on my HOT operated airtight woodheating stoves I never have to soot scrape off the front side glass doors. If/when I soot them up I just “dissapear” it off with an edge of metals destructive Hot over aired combustion cycle. This sooting Only ever happens in a cool starting up combustion process. Lower system air starved Hot gasifing operating these and then close coupled upper chamber combusting with 2000F secondary air never soots up anything, anywhere in these stoves.
So . . . a lot more complicated relationships CO <-> CO2 in a real world device useage than than can be easily pencil out.
Rapidly cooling “freezing” CO as stated in a lot of the historical literature will certainly help to stablize it. “Freezing” mean rapidly cooling it with a liquid or forced air heat exchanger. Some soot does drop out here but only by wieght of fuel put in 0.0x% of the fuel put into thew system. Separate it out, collect it and cycle it back into the top of the process. No big deal.
Useable amounts of heat is pulled out in this heat removal freezing/stablizing step.
Some use this heat as a very significant input improvement into their gasifier for fuel efficiency benifits.
Others; farm this heat out for outside of the gasifier system purposes.
As PeteS says this is enough heat in the output gas to easily usable warm up a soaking hot tub or supply from a two hour gasification cycle a full half of a small families daily domestic hot water needs. Not theory. Only crafty shyness over my now old man white chest hair and a seen sneeky video camera kept a tub image of me gas heated tubbing off of the internet a couple of years ago.
Yesterday my wife showed me a certain local small falcon bird that could actually stop in flight and hover in place, then resume flight and hover stop again. It did this continuously through three complete cycles trying to scare out field mice.
95% of even todays put up info says only hummingbirds can do this! Not that long ago the only in thier head types would print up with known aerodynamics that hummingbird flight was impossible! These birds are not “new” - been around for thousands of years. Easily observable. All forms of wood fuel useage including woodcharcoal is also old, old much practical man observed for anyone willing to take the time effort to use, do, look and see, feel and smell. And airtight reactors doing gasification has been around for neigh onto 180 years now.