If the fuel is free you don't need to worry about effecientcy that much ?
As long as there's a hot ash bed to gasify it, it should burn as it collapses down. I'm thinking of a horizontal firebox, like a pizza oven.
i think this would soot up a bit too quick (ideal for a used oil fired heater tho)I have a cast heat exchanger from an old baxi bermuda fire that's been knocking about here for ages. Indeed, i tihnk i even have 2-off them.
One of these things -
I had the same idea a while ago, the boiler would be huge, and a bespoke fabrication, but you would cut out any preparation tools to maintain, saws, chippers ect.
A standard euro pallet weights 10 - 24 kg and the softwood would equal 28 - 67 kw/hr.
Softwood is 2.8 kw/hr/kg at 70 % burn effecientcy.
One problem is standard pallets are worth £3 plus each, people drive about collecting them, and what you can pick up for free can be a lot of special sized, broken, and packing wood.
A fire box sized to fit 2 pallets, as one burns away slide in another one. A water jacket boiler with vertical tubes ?
A bin full of burnt nails to weigh in every chrimbo.
I got 11.72 kw to heat 200 L in one hour. From 10 to 60 deg C. But I don't know at what effecientcy water can be heated by solid fuel.
You can guess allsorts but it normally ends in disaster. 60kw requirement is a big house with no real insulation or a very big house indeed with insulation in order, 30kw is a good size detached house to modern standards of insulation
I understand that there are a number of compounds in woodgas, with different temperatures required for efficient combustion (full oxidation) - obviously why slumbered fires have issues with stacks tarring. Providing the bulk of the burn exceeds these temperatures, and the airflow is not disproportionately large (as in blowing away the heat) i cant understand why it would matter how dense the wood was packed.
I don't know about the pallets but I'm sure the pallet are worth something to a pallet yard,I know by me on the dock road if you were to bring em in the guy would give a fiver a pallet.....dunno if he's still around like?
I dont understand why the density of the fuel (ie a whole pallet, vs broken up and stacked tightly) makes too much of a difference. Three things are needed - fuel, air, heat. The packing thing is only going to affect the heat side of the triangle.
I think ill see how much oil tank steel i have left after making some new bunds for my reactor, and then see how well a pallet burns in a simple envelope.
If its good, i can work out how to fit a heat exchanger / burner (for ignition) after that.
We rely on free pallets for our heating and we have one main source who we get our pallets from (unbranded ones, deposit free).That also raises another possible consideration with this design idea. What happens if or when Julian's source of free pallets suddenly dries up when ther bloke realises he might make a few bob from them. You'd need to make the design able to fall back to burning smaller wood pieces efficiently too.
We rely on free pallets for our heating and we have one main source who we get our pallets from (unbranded ones, deposit free).
I was offered a load of free hardwood offcuts which I gratefully took which meant my occasional visits to collect the pallets stopped temporarily.
The manager from my pallet source rang me up in desperation as nobody else wanted their pallets and his limited car parking was being lost to a mountain of pallets, if I didn't take them they would have to pay for a bulk skip to get rid if them.
Talking to a few pals and it seems to be common here in the SW to pay for removal of pallets, nobody wants them except around bonfire night!