using a charcoal retort to heat log shed?

[openspaceman]

That should work, with a thermostatic valve (e.g. vehicle radiator system) to stop it from running too hot or cold.

 

No need to get hung up about a wet system to transfer the heat

 

We have been looking at extracting the huge amount of extra energy available during a charcoal burn. The main interest is in using the surplus gas to generate electricity (there is enough to run a 10kW genset for days!) but we have also looked at the surplus thermal energy and run a paper exercise on how much there is, how heat generation profiles with time and considered what you might do with it.

 

Alec

 

We did this and ran the offgas to power a gas turbine but the complexity increased the capital cost out of all proportion to the energy value

[flatyre]

It makes so much sense to get some value out of the flare, up around 70% of the calorific value in the wood can end up there.

 

Do you intend for the brash to be the initial support fuel or for it to make into char?

 

The quickest char volume I ever made was with 3 month old oak lop and top, after the cordwood and timber was gone, into a ring kiln using the pit method (now referred to as "flame curtain" by biochar makers). The heat from this could be entrained into a gas:gas heat exchanger and an induced draught fan, using a thermostatic air bleed to keep the temperature low enough.

 

You do need dry wood to sensibly make charcoal because water slows everything down, it takes far longer to dry wood than it takes to pyrolyse it.

 

What area are you?

 

to be honest until it was up and running (just a theory at this stage) I don't know what will be used and where, probably use semi seasoned wood, the kind of stuff that's too small for logs but big enough to make good sized lumpwood char without needing days in the kiln, and the brash, conifer and whatever else can be used as the primary fuel. Its all just theory at the moment but seems like a waste of heat running a charcoal kiln next door to a log store. In Northern Ireland by the way:confused1:

[Woodworks]

I don't know what will be used and where, probably use semi seasoned wood, the kind of stuff that's too small for logs but big enough to make good sized lumpwood char without needing days in the kiln, and the brash, conifer and whatever else can be used as the primary fuel. Its all just theory at the moment but seems like a waste of heat running a charcoal kiln next door to a log store. In Northern Ireland by the way:confused1:

 

I used the product from a branch logger so sub 75mm. This small material does make great charcoal but think you will benefit massively from properly drying it.

[agg221]

No need to get hung up about a wet system to transfer the heat

 

We did this and ran the offgas to power a gas turbine but the complexity increased the capital cost out of all proportion to the energy value

 

We are keeping things relatively simple with internal combustion and unpressurized gas storage.

 

Alec

[openspaceman]

to be honest until it was up and running (just a theory at this stage) I don't know what will be used and where, probably use semi seasoned wood, the kind of stuff that's too small for logs but big enough to make good sized lumpwood char without needing days in the kiln, and the brash, conifer and whatever else can be used as the primary fuel. Its all just theory at the moment but seems like a waste of heat running a charcoal kiln next door to a log store. In Northern Ireland by the way:confused1:

 

 

 

Firstly lop and top dry quite fast so using a flame curtain will produce you some lumpwood, you can always burn the fines for some additional heat elsewhere. As Woodworks says the branch logger output seems ideal (though I have only burned a few bags of slabwood). Chunked up it would fit in a simple device, shame you are too far away as I have most of the bits and pieces to find new homes for.

 

There is easily enough heat in the offgas to both dry and pyrolyse the wood but the limitations are in the retort. This is not a problem with dry wood but if the wood has even moderate mc then the drying has to take place in the retort and it just takes too long to get the heat through the container wall and into the retort, a kiln does not have this limitation. With both an issue comes from the moisture affects the offgas, lowering its calorific value and making it difficult to flare. So it makes sense to take wood hot from the kiln and into the retort.

[openspaceman]

We are keeping things relatively simple with internal combustion and unpressurized gas storage.

 

Alec

 

Perceived wisdom is that woodgas (from the total gasification of wood) needs to be created at above 800C in order for the tars and vapours to be cracked to simple gases, CO, H2 and CH4. Whilst big wood distillers did run large ic engines (and a gas turbine is ic) on the offgas it was after the vapours , like vinegar and alcohol and creosote had been recovered, the residual tars were often a long term pollutant of the site for years after. They also had to decoke the engine on a weekly basis with picks and shovels

 

Making charcoal in a retort tends to be around the 500C mark.