cornish wood burner

I would think similar principles applies as in a larger chip boiler. A constant fuel supply gives constant O2, constant exhaust temp and a constant heat output. Fuel input every 10 seconds for maximum output. Obviously your stove will have bigger gaps between stoking but little and often seems the right way to me.

Hi open spaceman Always worked on 4KWh/kg @20% and 3.5@ 30%, boiler efficiency at 90%? With a little cleaning time gave me 50 tonne Walking floor holding 120 tonnes of chip, the chip then drops into a cross auger (extract) that then feeds the stoker auger. Photocells look across the extract to start the walking floor. Another photo in the stoker feed chamber to start the extract. Our de- ashing is on timers so fairly simple there. I have made timers to give an air blast over the photocells which shift most chip but still get some problems mid auger. 200,000 ltr accumulator tank through the byroads was interesting. The 3MW was our first and I had little input in the design layout but for the second I made sure things were to my liking and especially that there were no sloping augers. Lesson learned the hard way. The first install company are still installing near vertical augers which only work with screened chip. We looked at one of their systems when choosing the 1MW. They obviously have not learnt so lost a sale. Totally agree about the out of spec chip and I too enjoy the snagging and fine tuning. Hate drive chains, lost a couple but job for the apprentice now I think. If you ever are passing Plymouth and would like a look around pm me.

That would be the nails I expect unless he was running too hot. Pallets might be very dry and some are treated so he might have needed to turn his air down a bit The burning is no problem its getting the chip into the furnace. The chip locks together and does not flow properly, (bridges). It can jam augers if they are marginal. The longer pieces trip safety devices, flaps and finger activated switches. They block photocell line of sight then the chip feed stops and the boiler goes out. To be avoided if you rely on your boiler.

Looks very much like shredded pallets. Sorry to be brutal but if you were chipping my round wood you wouldn't get to fill a second trailer. Too many other things can go wrong running biomass boilers without knowingly introducing problems. That said if the wood you were chipping was very old and brittle then you might expect something like your picture. Problem is when wood gets to that stage it absorbes water quickly. I try to dry for a couple of years with good airflow and chip before the wood goes over.

Certainly on my garden hedge the ash covered in ivy is not doing so well as the clear ones. I have noticed the deteriation over the last 15 years as the ivy coverage increased and now it is starting to drop larger dead wood. I am no expert but it appears to me competition rather than coincedence.

The other problem with shredded chip is bridging in the delivery/ holding system. That sort of chip would bridge across walking floor elements causing a cavern you could stand up in.( if you are crazy enough to do it )

Merry Christmas open spaceman I guess it is all relative. We run our RHI funded 1 MW. 24/7 and hope to put through up to 50 tonnes a week. Both our boilers have walking floors with the feed controlled via phoocells. Auger size on the 1 MW is about 250 as far as I remember but is prone to long pieces hanging across the auger blocking a photocell. Runs out of chip then of course. Another rarer trick is for a long piece to poke the blockage flap open same as yours. Sometimes we get zero blockages in 500 tonnes but a batch with some overlenght bits in can easily result in many stops. Our 3 MW has 330 dia augers and is far more forgiving as it needs longer pieces to bridge or stick into the photocell line of sight. It did have trouble with very dry fines rattling down the auger and eventually causing a jam. It was install too steep by the installer but we changed this and has been OK since. We buy our wood in but use around 3000 tonnes pa depending on the temperatures.

5 boilers burning 20 tonnes per week means they will be very small. Therefore the chip delivery system will almost certainly be very sensitive to any out of spec chip. If you do buy a chipper you need to make sure it is absolutely top notch to provide this standard of chip. One of our boilers can burn more than 20 tonnes a day and overlength pieces can still stop it. As matter of interest why didn't your woodland owner go for a centralized system with one larger less sensitive boiler. Unless the houses are very large distances apart it must be the cheaper and certainly the more reliable way RHI funded drying I presume.

Agreed. We have to park a pallet inside to brace against the wind

Last day today, been doing last minute repairs before the holiday. Tomorrow off, on call Christmas and boxing day, definitely in on Saturday cleaning out and feeding the boiler. Back Monday. You self-employed guys have it SO easy!! Have a good Christmas all.

Only problem I can see is for £200 a day you are charging a fair chunk of the cost of an electric splitter so a lot would do it themselves.

After a bad day that made me smile, Thanks Treequip

I think your first job tomorrow should be a sharpening lesson, give him a saw then keeping it sharp is his responsibility. Practice makes perfect as the saying goes. Sounds like he will get plenty of practice.

Hi John We have some experience using contract chippers and the heizos you mention are a bit small. I am not sure what power you have but I would have thought a minimum of 300hp to be remotely competitive. You will be competing with outfits that can chip 25mc wood for £8 a ton. As a guide we use machines driven by 360 to 780 hp. Why only G30, that has to be the slowest and the most power hungry. Moisture content has a big influence on price and desirability. I cannot say what you would get per tonne but possibly if you could air dry the wood then sell direct you might have a sideline market. The sun takes some beating for cost of drying.

3MW wood burner sprung a leak, stone went through a telehandler tyre, puncture in my car tyre and my lad broke my last jigsaw blade. Average sort of day. Time for a beer I think!!!

Assume 4 KWh/kg so a 8kw stove should use about 2.5kg/h allowing for some inefficiency So burning 10hours a day then 25kg/ day Hard or soft little difference in weight used just need to feed it more often with softwood as less dense.

How about an ad in Gumtree or local free ads etc. There must be a lot of people in your area that will process and burn softwood if it is cheap enough / free.

One thing that I havn't seen mentioned here is how good the seals are on our storage cans. I would think unmixed petrol does not deteriate in a jerry can with a perfect seal but keeping fuel in a plastic container with a less than perfect seal would allow deteriation.

20% sub 3mm for G30 spec chip. Heizo is a good chipper and I would be very suprised if you are producing more fines than this. Might be time for a blade sharpen if you are.

I agree that wet wood is easier to chip than dry but if you hire a chipper it will almost certainly be a decent machine so it will not be bothered by dry wood. Normally we get a few hundred tonnes before the blades need sharpening. Certainly if you try and chip with blunt blades then you will get excess fines.

Why don't you air dry your wood first and then chip it. Presumably you do this with firewood

That sounds about right. It varies obviously but in rainy Cornwall an average day is around 80% by day going to 100% at night. I expect inland should be a bit drier but I still would expect several nights near 100% RH.

If you consider a winter night with 100% RH which most are then from the graph it looks like wood will dry down to just under 30%

The winter days will be fine its the nights that are the problem. Part of my day job requires RH control of glass houses. We have very accurate monitoring and it is amazing to see the jump in RH as the sun goes down. Air movement is what you need when the RH is at a level to take the moisture but look at the graph and you will see the result of 100% RH. By having a open tunnel in the winter you are feeding moisture into the logs exactly opposite to the summer good work. Condensation and moisture laden air will increase the MC of your wood at night in winter.

Hi Mikeyne Your poly tunnel sounds good. Have you put in vents either end to get some air flow through. Probably closed in winter open in summer. One point in winter we have more night than day so I expect that is mainly at night when the moisture is reabsorbed. Lower night temps and the RH will go to 100%. Certainly does in Cornwall, 98 % by day as well ATM. If you could get a stack of wood to its expected minimum mc at the end of summer it might be an advantage to cover the logs with polythene /insulation to restrict the moisture being reabsorbed. Not tried it but it might be an interesting experiment.