Not a lot of progress this weekend- it’s been p**sing down, as we say in the UK. We’ve got occasion to say it a lot. I did get some hardwood chips charred in a scaled down two barrel system, and what should I find in the middle of the footpath last week, but one of the local flowering cherry trees, brought down by St Jude’s Storm. After making diligent enquiries, and establishing with reasonable confidence, your honour, that I could help myself to a chunk, I managed, with an extremely crooked bowsaw, to get most of the trunk, and I managed , with an awful lot of gas for smoke abatement, to char about a quarter of it. I should really know about moisture content by now. The question is: how do I get wood dry, when storing it under cover for a year just isn’t an option? Retort or drying kiln? Hotbox powered by the car’s cooling system? A basket in the engine bay? Alternatively… have a look:
Pallet wood hasn’t been treated with anything nastier than heat. Somebody’s already spent the energy to heat it to 56C for 30 minutes. I suspect that it’s not so much "How long to get them dry enough?, more “How long can you leave them in the p**sing rain before they’re too wet?” They practically jump out of rubbish heaps and chase me down the road. What’s not to like?
One other question- moisture testers- are they any good?
Hi Brian, To make wood into charcoal, you must remove the water as you know. Two ways to do it. Be patient and let the sun heat the wood and allow the moisture to dissipate. In a temperate area such as England, you will also need to cover the wood. The second way is to put the wood in some device and apply heat to it. This is faster, but requires an external heat source.
Do you have any roof space where you could stack wood? A deck? A broken down car? Along your fence? Make a deal with a local tree trimmer? There has to be something around you can use. The pallets make good charcoal so if they are following you home, get an electric chain saw and cut them apart. The nails are easy to pull from the charcoal with a magnet.
Keep thinking, the light bulb will go on one day soon.
Gary in PA
Thanks for the replies- in fairness to myself, I should point out that in my own urban back yard situation, space really is at a premium, and a further point might be that a pile of wood with drying air circulation could potentially become, or be seen as a pile of inflammable material with combustion air circulation. With pallet scrap so readily available and free, so easily stored on my Landy roof rack, so easily processed in the tunnel stove, and so benign, I’m inclined to run with that for a bit, but use the heat currently wasted for kiln drying or retort processing of small amounts of tree wood. Whatever way, I’ve got 100 litres+ of gasifier char stockpiled- lets get gasifying.
One little question- with a two barrel burn, do the brands form at the top or the bottom, or wherever they feel like?
I’ve only done 1 batch in a double-barrel setup so I don’t know exactly, but logic tells me that the brands are in the bottom middle where the oxygen never gets to when the heat is also there.
Has it been that long? I’ve had a bit of a break, but I’ve got 150 litres of processed char just waiting to be gasified. I did a flare run last night, and by lucky accident stuffed a piece of sponge into the pipework just before the fan that throttled the gas flow to a level where, with no moderation, the combustion temperature settled at “orange” - about 900C, and with a water spray I could control it between orange and dark orange- I’d guess between 850 and 950C. I got a spark-free yellow flare- I suspect due to sodium in the water, but best of all, a plain mild steel tuyere survived intact. Next step, regulate the combustion temperature by throttling the air intake.
A quick update, with some photos of the current gasifier and filter setup. The cyclone and sponge filter came together more or less by accident- the cyclone was originally for dust abatement during charcoal grinding, but it seems to work well coupled to the flare fan. I’m experimenting with water moderation to keep the temperature down to orange, and throttling the intake air during startup, and I’m getting away with just using a scaffolding pipe tuyere. From the flare run earlier this evening…I used about 9 litres of char over a 45 minute run, and sprayed an estimated 1.5 litres of water down the tuyere, more or less continuously, of which about 200 ml ended up collected in the cyclone bucket. The flame was pinkish yellow, and spark free, so the filter appears to be working… A promising run- hopefully I’ll get an engine run in next weekend.
On Saturday, for a few tantalising minutes, I had the Landy running on the Simple Fire. I coupled onto the top of the oil bath air cleaner, effectively filtering the gas twice, started up on LPG, lit up and gradually weaned the engine off LPG. I was hoping for a tickover, it seemed happier at higher revs off load. I was pouring, rather than spraying water down the pipe, with a marked increase in revs each time. It was a lash-up system, and I packed up when the daylight ran out, but the concept was proven- sometimes tantalising is good. To do… reconnect the lambda probe, seal off some air leaks, fix up a screen wash pump for water feed, and get some longer runs in. To be continued…
Currently nursung the grandmother of all colds, but I managed to get in a brief but encouraging run on the Landy over the weekend. I discovered that the ball valve I was using for gas/air balance was way too small, but by cutting an extra hole in the plastic pipework, I was able to get it weaned over, and watch the lambda reading change dramatically between “much too rich” and “much too lean” as I added water- the water does seem to make a big difference to the calorific value of the gas, but the little screenwash pump I was using proved woefully inadequate for continuous use. So… two inputs that need to be controlled, the water feed and air intake, according to two readings, the lambda probe, and the combustion zone temperature. To my mind, it’s getting time for Arduinos and stepper motors and 3D printing of throttle bodies. The to-do list is getting bigger, free time isn’t ;-(
Getting there. The most interesting development was getting a butterfly valve for the air intake/mixture balance 3d printed in nylon. I used Openscad to design it, sent the STL file to a print service, and received and fitted it on Saturday- the photos are attached, and I can upload the source if anyone’s interested. After a disappointing run last weekend, today’s run was more encouraging. I managed to get about 20 minutes from the point where I switched the LPG off until the output pipes got too hot to touch. I used a gravity fed water drip from a 25 litre can on the roof rack, and a plain scaffolding pipe tuyere, which seemed to withstand the orange combustion without problems. To do, though- fit a feed hopper to replenish the char and get longer runs, and open up the prospect of refilling when the system is hot, well aware of the risks of a blowback, add a condenser and trap to get the moisture out, and program the Arduino to run the LPG stepper valve. The butterfly valve… spent mosy of it’s time closed- I used a much smaller ball valve to tweak the mixture. Was air getting in somewhere? To be investigated… Quick question for the US contingent… if I say “scaffolding pipe” does it mean the same thing across the pond? Galvanized mild steel pipe, 48.3mm OD, 40mm ID? http://jamclasses.drbanjo.com/static/dimages/valve1.jpeg http://jamclasses.drbanjo.com/static/dimages/valve2.jpeg
It’s two half shells that ty-rap round the scaff pipe, the butterfly, and a D-shaft that fits through. I’m a terrible photographer, so it’s not clear from the photos, but I’ll try to get the rendering up tomorrow.
Managed to get an hour or so of runs with the new feed hopper- I used up about 16 litres of char- a bit frustrating, because I’m used to monitoring the lambda probe, and I didn’t have my multimeter, and against my better judgement I used rigid PVC hose straight out of the gasifier, with predictable results. I have got the Arduino LPG stepper valve control working on the bench, and I’ve got some ideas in my head for the MkII mixer valve. Getting there…
A photo of the current setup flaring is attached- there’s a lot of background clutter, but you should be able to make out from left to right, the feed hopper, the gasifier itself sitting in a water jacket with a water drip down the tuyere,an inverted U tube for cooling and condensation. and the cyclone and blower. There’s a sponge filter within the cyclone. I got about an hour’s run on the Landy- the questions are: can I trust the ring latch lids on the cyclone and feed hopper as gastight, can I get the feed hopper flowing more reliably, and replenishing the reduction zone without having to shake it, and can I take the lid off the hopper for hot refuelling safely? I did find that by turning up the water drip to douse the combustion zone, I can get a safe and controlled shutdown without any problems firing it up he next day.
I did have a shot at building a Drizzler, with a twist- no grate as such, just a pick-up tuyere, reducing the fabrication to two tubes in the lid of a ring latch pail, and preloaded with charcoal, I managed to get it flaring fairly quickly. It would inspire me to put a much bigger tuyers in the Gilmore gasifier, and get from charcoal fuel/charcoal reduction zone to wood fuel/charcoal reduction zone. Now, how would this work? A Drizzler, replenishing it’s own reduction zone, and an auger to bring the charcoal to the top. Collect the overspill, and you’ve got a carbon negative biochar breeder… Maybe further down the line.
Hi Brian, I don’t have a problem opening up a hot charcoal gasifier to refill it as long as a few precautions are taken. NEVER open to refuel until no charcoal gas is being pulled from the generator.(turn off the fan and shut off the engine) You do not in any way want to pull oxygen into the charcoal gas reactor because it will mix with the carbon monoxide and form an explosive mixture that will ignite (KABOOM) Open the cover but do not stick your head over the opening. Some carbon monoxide will escape and you do not want to breath it. At worst, you may get a little flame appear near the opening where oxygen kind of mixes with the CO, but nothing to get excited about. Pour your charcoal in, put the lid back on and start up the fan and wait a minute for the charcoal gas to get rich enough to burn.
Gary in PA.
My own refuelling protocol is to cool the combustion zone as far as possible with water or another possibility, Co2 from a cylinder, plug the tuyere and ensure one way or another that the gas is exhausted, then open the lid, pour in the char and close it asap. The obvious option to me is to have twin gasifiers, one of which could be cooled for fuelling. The best option would be to have a gas-tight lock, with all the technical challenges of a gas seal that allows solid fuel through.
Update… Last weekend I did a long flare run without the filter to get a rough idea of the amount of particles emerging, and how well the ash is getting cleared, and how well my setup would adapt to Drizzling. I’m effectively topping up the charcoal bed from a feed hopper, so there’s a constant height of charcoal. I was hoping to see more sparks through the run- are ash fines too small to show up as sparks, or is the ash stagnating in the gasifier and storing up trouble? Drizzling seemed to work as long as I stuck to fairly large wood pellets- once I started putting fine sawdust down, it gradually clogged up with fines- no real problem- just poke it with the poking stick. By accident, rather than design, I can see through the window in the feed hopper right down to the surface at the end of the run- it was glowing much brighter than I expected with the fines dancing on the surface, and still producing a flare, although with loads of sparks. To a degree, it blows my theory of cooling within the charcoal out of the water. I’m still no closer to to a decisive answer to the question: cool the charcoal, cool the gas quickly, or cool it slowly?
What I have found are solar garden lights in the local Poundworld shop, with a little solar panel included that give a useful voltage from the light coming out of the tuyere- hopefully I can press one into service to gauge the combustion temperature, and control the water drip.
Slow progress, but progress nonetheless. A couple of disappointing gasifier runs- I seem to be hitting a wall with the gasifier capacity- I’m aiming for control of the lambda between very rich and very lean using the 3d printed air inlet valve- so far the pattern is: close the valve completely to get it running very lean. Air leaks or caking at the bottom of the tuyere? To be investigated. What I am pleased about is a little twist on Gary’s two barrel method in the photo. Have you ever seen a wooden grate before? Once the fire burns down to the wooden supports, it dumps the fire into the bottom drum, away from primary air, with no intervention- load it, light it, leave it, get on with something else, and come back to a drum of char. No welding, and all done with 25 litre drums that they’re throwing away from the factory next door.
Hope the Argos meet-up goes well. I’m heading off to a couple of festivals in a couple of weeks. Small World seem pretty keen to have a couple of burners going, so see how that goes.
Had a good look for leaks, but it looks like the worst was through the printed 3d valve that I was so pleased with. At the loads I’m running the at at the moment, I suspect I might have better control with a much smaller valve. The smaller lash-up Drizzler seems to be outperforming the bigger setup with the charcoal feed hopper- it’s a 25 litre can with a ring latch top with the tuyere and gas outlet welded to the lid- a Simple Fire in every detail except the tuyere diameter- it’s around 50-60 mm diameter. I pre-load it with charcoal and start it up as a Simple Fire, then chuck wood pellets in.
