Hi Brian,
Check out this guy’s videos. http://www.youtube.com/watch?v=nQxIXDo-egA
I chose something different but this seems like a good system if I wanted something small and was dealing with an easy to pour substance like pellets of chips.
David
Thanks for the link… his principle seems to be heating from the inside out, drawing the tar gases from the bottom, and open burning. What is a little bit off-putting is the amount of smoke- I’m practically paranoid about smoke abatement, which isn’t that difficult- I use a little bit of propane in the stove during start-up- and I’d be a bit uneasy about lifting, flipping, and burying a hot barrel for it to cool. Another possibility would be a TLUD, but with my own refinement of feeding pellets in from the bottom, and skimming char from the top.
I managed to finish the weekend with a two hour flare- the scheme to char wood pellets in the Simple Fire vessel was a limited success-slow and smoky, but I managed to get a full vessel that lit and flared very quickly- a pale blue flame with yellow tips. I did notice that I could get a much bigger flame by blowing down the tuyere, so it looks like the limiting factor is the little combi boiler fan- a hairdryer as a forced air fan, anyone? I’m trying out a mild steel tuyere, accepting that it will get eaten away, and I had the candidate engine running on propane… the weekends aren’t really long enough.
To be continued…
I was hoping to get an engine running this weekend- didn’t quite make it, but I’m well on the way- the Kawasaki suitcase genny has a particularly easy air filter box to couple into, and I’ve got some valves, tubes, and a mixing chamber waiting. Charcoal production… it looked like I was overpowering the secondary combustion volume of the stove, and putting a smaller burner in dramatically reduced the smoke, feeding in a little bit of propane reduced it to zero. I’m experimenting with a TLUD approach and a long scoop to harvest the char with modest success- has anyone got a TLUD working without forced air on a chamber about 200mm diameter? Remember, I’ve got a pretty demanding set of requirements for char production- smoke free is essential, I want a “Load It, Light It, Leave It” approach, but I’d settle for an hourly intervention while I get on with something else.
I have a 150 mm (6") TLUD that is running right now to heat water for dishwashing. After 25 minutes, the very dry hardwood slices of Mesquite will be nothing but glowing coals, and the water is hot enough for washing dishes. Dump these coals from the bottom of the stove into an airtight container, or a bucket of water and before use, sort through them looking for any wood not totally converted to charcoal. I sort mine on wire hardware cloth (1/8" mesh) so the ash falls out. You can download a .pdf of free plans. Google on “Anderson Champion TLUD”. For a 200 mm (8") burn pot, you can use the Anderson design, or build a Peko Pe. Neither of these smoke, It takes me about a week of cooking/boiling to get two gallons of sifted/sorted and dried charcoal. Until you figure out the fuel requirements, have a small hand cranked BBQ fan ready so you can inject some extra primary air at the end of the burn, because that is when any smoke will appear, IF it is going to smoke.
Hi Brian, Here is a link to another way to make charcoal.
http://driveonwood.com/content/charcoal-made-easy-way
It is about as basic as it gets and if you use dry wood (20%MC or less) it is almost smoke free. I get about a wheelbarrow load of charcoal from each 55 drum of wood I process. This method does require some skill but I feel that is easily learned. It isn’t dummy proof. When using this method the fire is checked on about every hour during the three hour burn.
Gary in PA
A rewarding weekend so far- thanks for the tips on charcoal making- I’ve had a little breakthrough with a TLUD stove and wood pellets- with a twist. I’ve made two stackable burn pots with hook points to handle them while hot, so that as the top one finishes, it starts the bottom one, and gets emptied, refilled, and placed on the bottom, so that the process can happen more or less continuously, reducing the smoke as the burn finishes. I’ve got a weed wand, which is great for starting an even burn on top. I managed to get a barrel of chips straight from a tree surgeon, and promptly had a “What the Hell was I thinking?” moment by trying to burn them straight away, resulting in a couple of very smoky hours that I won’t be able to claim back. I’m about 95% of the way to a first attempt at running the genny, or was when the MIG gas ran out. To be continued…
I will have to try that; gives you more of a continuous burn. Could you post some pics…
David
Nuthin’ fancy- basically two- for now- chopped fire extinguishers. The bottom sections have slots cut to form a grate, three pins on the bottom to locate into the lower pot, eyes left and right to lift it hot, and one on the bottom to tip it out. The middle cylinders become the chimney. So far, only tested on wood pellets- can’t as yet speak for the results on less evenly sized woodchips, but it produced good char, and without any forced air. More data to follow when available.
The engine run didn’t quite materialise by close of play. It’s a cord start, and my game plan is to start on petrol in the carb, wean it from petrol to propane, and then onto char gas using a lambda probe. I suspect there are too many air leaks in my Mk1 mixer unit, but it’ll get a good thinking about during the week.
I’ve added a photo of a mild steel tuyere after a low power run on the flare- for now, I’m just treating the tuyere tube as sacrificial- chop it off and weld another bit on.
To be continued…
Tantalisingly close to running the genny, but not quite there yet. For complex reasons, I’m starting on petrol, weaning onto propane, then trying to wean onto the gasifier. So far, with the pipework in my setup, and the burn zone nice and bright, I can back the propane flow to 75% and no lower. Prime suspects are the restrictions within the gasifier- the tuyere is about 800mm of 12mm inside diameter gas pipe, so it might be worth moving up a size, and what I haven’t been doing is screening the char to remove anything below 3mm- it’s a dust abatement thing. My current check is: can I blow down the tuyere? One question- I’ve got a lambda sensor on the exhaust for juggling the gas mixture- is there any reason why I shouldn’t rely on it for running on char gas?
Did a bit of work on the stacked TLUD stove- previously, it was working well as a very unstable stack of burn pots and a chimney. I’ve made up three support legs for the chimney, but at the moment, the secondary air is getting too close to the top of the char. I know what the next evolution is going to be, though.
To be continued…
Brian Hughes: I’d guess that your 12mm/0.5" gas pipe might be too small. Gary Gilmore’s Simple-Fire uses a pipe with twice the ID (25mm/1") and thus 1/2 the restriction.
Hi Brian, I’ll agree with the other Brian that a 12mm (0.5") pipe is tooooo small. What I am finding (so far) is your nozzle can be too small in diameter, but making it too big (within reason) is not a problem. In other words, the suction from the engine will determine how much air it pulls into the gas generator so long as you do not resrict it with a nozzle too small. If the nozzle is lets in more air than the engine pulls, so what? It will only pull in what the engine demands.
I’d also recommend you get the fines out of your charcoal. Anything under 1/8" or 2mm has the potential to inpede the flow of gas. I know this systems works and works well if everything is in order. Hopefully you can get your engine running soon. Don’t get discouraged, it really does work!
Gary in PA
Just checked- the tuyere was nominal 3/4" gas pipe with an ID of 0.824". I’ve got a length of 1 1/4" with an ID of 1.38 to try out tomorrow. I can see the fines being a nuisance, mainly as a sure fire way of upsetting the neighbours- thats’s why I’m aiming to do everything in-vessel. Any screening will have to wait for a damp drizzly day, not a major problem in the UK. I might, in the fullness of time try this:
http://www.puffergas.com/fireballs/charcoal-fireballs.html
or better still, find somebody with a vegetable patch who knows what terra preta is, and then the whole operation becomes carbon negative- I just keep seeing more and more potential spin-offs, but I’ve no doubt that it will work eventually. “Tantalizingly close” is no bad thing.
I did have one “Doh!” moment when I opened up the carefully sealed up flare fan, expecting to find the impeller clogged with tar, but actually spinning the wrong way. It’s flaring better now…
I wonder how well that process would work with just regular sawdust and tar condensate from a WK gassifier…
AIUI, if you’ve got a cement mixer, a garden sprayer and some starch, you’re in business. If I’m losing 25% of charcoal production as fines, Then it’s not worth bothering with- use them as biochar. If i’m losing 75%, then it’s definitely worth trying.
A horrible wet day today- used it to empty and screen the gasifier using a kitchen sieve with about a 1 mm mesh. I found two alarming large lumps of cast iron, presumably that used to be mild steel tuyere tips, but between the bigger diameter tuyere and less fines, I seem to be getting better gas flow, and I did two long flare runs. One thing I noticed- I tried to boil a pan of water on the flare, but the charcoal gas flame doesn’t seem to be that hot- I can easily move my bare hand through the flame. The pattern that’s emerging is that when the outlet pipes get too hot to touch, the gas stops burning. I’m currently spraying water down the tuyere, but it’s an object lesson in why combustion zone cooling is essential. It is heating up the bucket of water that I’ve got it sitting in quite nicely, so what I’m wondering is: could I give it a jacket of woodchips to char, feed the tar gases into the air intake for cracking, and get it self-stabilising? For future investigation. For now, fingers crossed for an engine run tomorrow.
Funny enough I have melted metal pictures like that… As to the non combustion When the temp at the outlet pipe goes up you no longer have enough charcoal above the nozzle. The reaction does not have enough charcoal to run through so is passing through and burning down to carbon dioxide and heat. Good luck on the engine run…
David
Nice paper weights! This just shows the need for cooling the nozzle, if you are going to use any steel. Your idea of charing wood chips and feeding the tars into the air intake are spot on. It works. The tars, water vapor and other volitales produced by heating wood will help cool the oxidation zone too. This is the same proceedure used in a wood gasifier. The wood gasifier needs that hot bed of charcoal to crack the tars comming off the wood.
The problem you will encounter is how do you cool your nozzle while the wood chips are comming up to temp? First they will emit water vapor and later smoke. This requires someone on hand to monitor what is happening and making changes to the air/gas mixture as well as moderating the oxidation zone temps. Kind of hard to automate with all the variables., BUT it does work.
Gary in PA
What are these “problems” you speak of? Are they something to do with “non trivial engineering challenges”? “Refinement priorities?” “Clearly identifiable bottlenecks”, maybe?
Have a look at this:
http://www.processassociates.com/process/heat/metcolor.htm
and this
it doesn’t seem like that big a deal actually estimating, measuring or deriving the hot spot temperature- the question is: Is there a sweet spot, or sweet range, that’s hot enough to crack whatever’s going in, but not too hot to melt a mild steel tuyere? AIUI, within the range, cooler= longer runs.
One thing, I’m not scared of Arduinos, PICs, stepper motors and electronics in general. I would be a missionary for lambda probes- this site converted me:
http://www.lambdapower.co.uk/TechNotes/technotes_index.asp
There’s only about half a dozen “zones” an engine can be in, and a lambda probe gives you a quick answer to the too rich/too lean question. There’s a controller already in place on the Landy for the LPG.
The technology is out there…
Tantalizingly closer. Yesterday I had the engine running very slowly, very briefly, and with enough confidence that the float chamber was empty to keep me believing. Today… spring is here, the weather is freezing, the snow is falling, the back “garden” is a mudbath. Not a day for experimenting.