Any new small charcoal retorts out there?

[openspaceman]

Main snag is too much heat. To protect the internals I now have various insulation materials on there way but the snag with this is temperatures will now be higher still.

 

Yes

 

 

 

 

 

Options as I see it are

 

Starve it of air but presume this will result in lots of gases going up the flue unburnt then have flaring out the top?

 

Yes and in itself this is not bad except it will be like running an engine with the choke on, dark smoke instead of a clean flare.

 

 

 

 

 

Build a much larger fire box so temperature are lower.

 

I don't follow this, you can have a smaller fire initially but once the offgas is fed under the retort that becomes the fuel that gets it all too hot.

 

 

 

 

 

Butterfly valve on flue?

 

 

 

Well a a means to direct the offgas away from under the retort, I'd tend to avid valves or anything the tars can foul up.

 

 

Insulate charge chamber so everything runs at high temps but steel survives. Looking at the Pressvess video it looks like this is the route they take.

 

Not seen it

[HertsWood]

Hi Richard,

 

I had about 25 brown ends from the second batch but they've just been put back in to cook with the 3rd batch

 

I suspect volume of charcoal will go up the more burns I do and the better the production process evolves.

 

The Haith grader arrived on Saturday...

 

Regarding what goes into the retort; I source the majority of my timber for either WoodFuel or charcoal from the woodland management operations we carry out for clients.

I try and use as much of the tree as possible with only smaller branch wood being left as habitat piles.

 

I'm working in woods at the moment, where we are coppicing lots of Alder, clearing Sycamore and thinning Ash. With the odd patch of Oak and hornbeam thrown in for good measure.

[richardwale]

Looks great. So how many Kgs do you think you get from each burn?

[Woodworks]

That's 50% volume, it will be lower weight, are you allowed to sell charcoal by volume now?

 

No idea but we do. I just fill a bucket to around the 12 litre mark and pour it into a bag. We don't put any weight or volume on the bag but they are around 2kg.

 

The idea with a much larger fire box is just a greater area to heat and have natural losses through the sides. It gets the same amount of gas either way so would be cooler.

Edited April 12, 2017 by Woodworks

[Woodworks]

In this video you can see the charge chamber wrapped in insulation at 5 min 23

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[openspaceman]

We were required to weigh our and did it at the riddling stage with a bag stitcher to close the bags

 

 

 

The idea with a much larger fire box is just a greater area to heat and have natural losses through the sides. It gets the same amount of gas either way so would be cooler.

 

I cannot see the benefit.

 

Traditionally you allow in more excess air or recirculate exhaust gas to lower firebox temperature but in this case it makes more sense to divert the offgas away.

 

The problem is too much heat and the flame temperature will be up around 1200C-1600C yet you only want to heat the retort contents to ~500C

[openspaceman]

In this video you can see the charge chamber wrapped in insulation at 5 min 23

 

That's a weel built device compared with my Heath Robinson efforts.

 

Yes it makes sense to use the cerablanket/kaowool like this to reduce overall heat loss. What all these lurgi based devices fail to address is making use of the flared offgas to do work and the manual loading and unloading.

 

If you think about the insulation : here it is not being used to protect the steel as the steel is cooled on the ouside by ambient air, so you can use a thinner layer of the expensive cerablanket and then add an outer layer of cheaper rockwool/fiberglass with the steel sandcwiched in the middle to protect it. In this retort the limiting factor is the steel which contains the wood as this is subject to the fire heat from below and the 500C inside. So you really need to control the heat in the fire once gases are being evolved.

 

With these two chamber retorts has anyone managed to load one whilst the first is gassing?

 

Yury's ekolon hot swapped cassettes so once it was all running no further fuel was needed.

 

Consider the offgas from pyrolysis of dry wood will have an average adiabatic flame temperature of over 1500C and has 70% of the energy in the original dry wood (maybe 50% in retorts as the low temperature means the char has low fixed carbon). You only want to heat the wood to 500C, you can run a dryer with anything above 40C and you can heat a building with underfloor heat with 30C so the process lends itself to running a cacaded series of processes each downstream one utilising the rejected heat from the one before.

[richardwale]

If the wood is completely carbonised is it ok to cook with if it was treated in any way before it was burnt?

[agg221]

If the wood is completely carbonised is it ok to cook with if it was treated in any way before it was burnt?

 

Depends what it was treated with.

 

The wood is going to get a lot hotter as you burn it than it did when you pyrolysed it. This means different things will come off. If you can be confident that the wood was treated with an organic biocide (the type of thing you can buy in B&Q) then it will have thermally decomposed, just like the wood has. If it was commercially treated then it could be copper, if it's modern it could potentially be boron-based, if it's older it could well be copper chrome arsenate (CCA). Burning the charcoal will also add oxygen, so the remaining compounds will convert to oxides. I don't fancy arsenic trioxide flavouring on my burgers myself....

 

Alec

[openspaceman]

Depends what it was treated with.

 

The wood is going to get a lot hotter as you burn it than it did when you pyrolysed it. This means different things will come off. If you can be confident that the wood was treated with an organic biocide (the type of thing you can buy in B&Q) then it will have thermally decomposed, just like the wood has. If it was commercially treated then it could be copper, if it's modern it could potentially be boron-based, if it's older it could well be copper chrome arsenate (CCA). Burning the charcoal will also add oxygen, so the remaining compounds will convert to oxides. I don't fancy arsenic trioxide flavouring on my burgers myself....

 

Alec

 

To add to Alec's post: if you burn Chromated Copper Arsenate treated timber you will volatise the arsenic and some chromium and copper, the worse long term problem is the chromium will be given of as the hexavalent form rather than the trivalent state in the wood. The remainder will be in the ash so the char will contain some

 

I think there is up to 5kg of CCA salt in a m3 of treated wood (but not all the thickness will be treated).

 

Modern treatments also contain copper

 

Creosote is likely to produce sooty particulates which will contain polycyclic aromatic compounds.