Thinking of having a crack at making charcoal.

[Woodworks]

I have been wondering what to do with the product that our branch logger makes and considering making some charcoal. I have had a read through some of the other charcoal threads to give me some ideas.

 

I want to keep it cheap to start with as I may find it does not work or is too difficult to sell. My first thoughts are something like this but burying the sides, back and top with earth to add insulation. Biochar at the Centre for Alternative Technology: business opportunity for small woodland owners or climate change solution | Woodlands.co.uk

 

I have a large old steel water tank that could work as the enclosure and can pick up 50 gallon barrels with clamp on lids easily. For recirculating the gas to underside of the barrel many pictures I have seen show a pipe looping round to the underside of the barrel but I was wondering why they don't just have small holes in the bottom of the barrel as I presume the gas is under pressure so would get forced out wherever the holes are.

 

Thoughts?

[hedgesparrow]

what you need is a 40 gallon oil drum. cut the top out right to the edge then cut the other end just inside the tap hole. this will allow the lid to fit on the lip you have left.

waiting to go and see a chap to see it done in the flesh, then i can crack on making some.

[csservices]

Or better still get one with the lift off lid, if I remember I will take some pics of mine tomorrow

[openspaceman]

I have a large old steel water tank that could work as the enclosure and can pick up 50 gallon barrels with clamp on lids easily. For recirculating the gas to underside of the barrel many pictures I have seen show a pipe looping round to the underside of the barrel but I was wondering why they don't just have small holes in the bottom of the barrel as I presume the gas is under pressure so would get forced out wherever the holes are.

 

Thoughts?

 

The main thing is to use very dry wood, the reason being that the actual process of pyrolysis ( splitting wood with heat) is very nearly neutral in energy input ( i.e. slightly exothermic between 330C and 440C) that all the energy needed is to raise the charge to that temperature. However boiling water away first is rather energy intensive, the steam you drive off contains about 0.75kWh(thermal) for every kg you drive off and in practice even with good heat exchange you'll need double. That's about 30% of the energy in 1kg of dry wood. Much better to let the sun do most of this ( but there are ways around)

 

If you use a barrel in a tank method simply invert the filled barrel with a leaky lid into some sand or ash, this is to allow the gas out but not allow air back in as the charge cools. A russian guy, Yury Yudkevitch, developed this using multiple barrels as retort. A retort keeps the fire outside but its disadvantage is all the heat has to be delivered through the sides.

 

Yury has the fire surround the inverted barrel which once it gets hot the offgas exits the bottom and joins the fire to continue heating the barrel. I used a simple 70W fan to keep the flames low so the heat was rising up the walls of the barrel. Barrels do not last long because whilst the temperature inside the barrel only needs to be ~400C the flame temperature is over 1200C and oxidising.

 

For speed at the cost of a bit of yield, if the wood is fairly small and very dry just light a small fire in the bottom of a barrel and once it takes add wood slowly, always maintaining a flame, this is a form of kiln. You will find once it's going the flame moves up the barrel and air cannot get back down to the newly formed char. This is in essence a modified pit method as described in Sylva. The guys in the weald would dig a trench and start a fire in the bottom, to which they would add the dry bavins or faggots, once the fire died down they covered the lot with earth and waited for it to cool.

 

It was also the way I was taught to get hot coals for a barbecue in a barrel cut longitudinally above the half way. A certain amount of air control can be had by slightly rotating the barrel.

 

Again the wood must be dry or you will not establish a flame without burning your char.

[smiles]

If you just have the holes at the bottom of the barrel,the wood inside will be exposed to the flames and then start to burn itself - whereas the manifold keeps the exposed flame away from the wood.

I guess that it would work when the wood inside got hot enough to start gassing - but you may have lost a fair amount of it by then!

[Woodworks]

Thanks chaps

 

Smiles. Yep it dawned on me last night that all I would do is set fire to the contents of the barrel. I thought there would be a good reason for the pipes but worth checking.

 

Openspaceman. Thanks for a comprehensive description. I like trying to understand what is going on not just getting a result. Yes the wood will be dry to 20/25%. Do you think the design I posted in the Cat link is suitable?

 

Cssservises. Looking forward to seeing your set up.

 

Hedgsparrow. I think I can get barrels with a detachable lid but if not I will give it a go.

[openspaceman]

Yes the wood will be dry to 20/25%.

 

Do you think the design I posted in the Cat link is suitable?

 

25% is barely dry in this context, it will still sizzle.

 

The test is to split a small bit into many pieces and stuff them tightly into a bean can with a few holes in the bottom such that the tops are level with the lip, pour a teaspoon of barbecue starter and light the top. If you end up with the pyrolysis front moving down and a clean flame then it#s fairly dry.

 

The twin retort that you linked to was revived in this country by a guy called Robbie Webster copying a south african design which I think was itself a crib of the Lurgi from before WW2. The method doesn't appeal to me because of the wasted heat and poor heat exchange surfaces.

 

PM me if you want to try a couple of simple experiments.

[csservices]

Right pics of my charcoal burner, this is as simple as you get really, 45 gallon drum with a lift off lid, drill 4 holes in the base about 1 inch diameter (its upside down in pic to show holes) stand it on 3-4 bricks, surround the base with earth leaving a hole for air to draw through, light a small fire in the base, using kindling or charcoal, once burnig hot add in the wood for charcoaling ideally about 3inch diameter at the biggest, biggest wood in first progressively getting smaller to the top, I usually go down to about inch to inch and half, once its burning hot and even, check this by spitting on the drum not scientific but a good indicator it will sizzle if nice and hot all round, put the lid on and prop up on one side with a small log, wear some welding gloves and be aware this can sometimes make it flare! once the dense white smoke reduces to a blue/clear haze shut the lid down and bang it on firmly and close off the air gap at the base with soil and firm down, if any smoke is escaping round the base seal with soil until it stops, job done, leave for 24 hours to burnout completely before opening, from lighting to shutting down should take 5-6 hrs sometimes less depending on type of wood and dryness

[Matt_Oldfield]

Excellent thread, been thinking of doing this myself for a while, just for a bit of fun and charcoal for my own barbeque!

 

Excellent post CSSERVICES, was thinking of doing the same thing, good to know it works!

 

Definitely going to crack on with this soon!

[hedgesparrow]

thank you for the clear concise details how to do it. will go down wood and start doing some. i knew approx just needed the exact way now i know.

need to get some more oil drums so i can have a few going at the same time.