OLDGUYS TRIPLE BARREL CHARCOAL RETORT DESIGN

[oldguy]

A crude but fairly inexpensive method of making fairly large amounts of BP charcoal is to insert a slightly vented 15, 20 or 30G steel drum inside a standing 55G steel burn barrel. Stoke the standing 55G burn barrel with scrap wood & fire the whole thing up, with the smaller barrel standing upright inside the outer barrel. Trouble with that method is you basically have no temperature control, it is cumbersome, messy and unsightly. Plus, many city, county & State fire ordinances prohibit the use of outdoor open burning barrels.

 

I have struggled with the issue of making comparatively large amounts of consistent quality pyrotechnic and BP grade charcoal cost effectively for some time. From extensive data on charcoal making, besides the type & size of the wood used. From what I gather charcoal retort temperature control is one key issue of several.

 

 

Obviously starting material affects the characteristics of resulting charcoal. Starting material should be reduced small enough to ensure fast and uniform heating. Both charring temperature and time strongly affects the characteristics of resulting charcoal. Charring retort should have a means of temperature control. Charring retort should be uniformly heated. Charring temperature of 250'C is too low. Charring duration at 300'C (572 F) should be few hours but not over 8 hours. Charring duration at 350'C (662 F) should never exceed one hour. 350 degrees Celsius or 662 degrees Fahrenheit is the "sweet spot". Charring should be stopped when the smoke from the retort vent has ceased.

 

If the retort is slightly pressurized during the charring process, the end result is relatively higher order of charcoal yield, than if not slightly pressurized. Wood contains various degrees of moisture and when heated emits flammable gas. Both will create "pressure" when heated inside a closed vessel. Rather than simply "venting" the retort through an open hole. If a charcoal retort is vented through a steel pipe with a suitable ball type valve in the line, you can increase the involved pressure slightly, to maximize the charcoal yield. Secondly, if the pipe is vented into the fire box, flammable gas will serve as addition fuel, as well as be more environmentally friendly.

Considering all these factors, here is what I came up with:

All major parts are ready made, not very expensive, and modification only requires minimal metal working skills, tools & equipment to build. You can control the heat with the flue dampers & determine working temperatures with hand held IR thermometer gun. You can increase or decrease the upper inner retort internal pressure by plumbing a steel pipe from the upper inner retort down into the lower drum firebox, with an appropriate valve installed in the open space between the two drum. You can view the lower end of the vent pipe by simply opening the firebox door. Once the process is done, simply close the valve to make the upper inner retort air tight & allow everything to cool. Once cooled, the inner upper drum can be easily emptied into a wheel barrow using a rake & slide type trough. Could also serve double duty as a shop heater during winter.

Used steel drums can often be found cheap on Craigslist, or in local Nickel type advertisements.

For a "Barrel Stove Kit", simply input those words in the eBay search engine & you will find many.

Or go to this link: http://www.northerntool.com/

 

Input "barrel stove kit" in the websites search feature. It will return:

Vogelzang Barrel Stove Kit, Model# BK100E, Item# 16160 (on sale around $40)

 

Vogelzang Top Barrel Adapter Kit, Model# BK50E, Item# 16161 (on sale around $20)

 

I am waiting for the UPS guy to deliver the cast iron parts & once here, I will be busy building & testing this design.

 

Edited January 12, 2012 by oldguy

[killforfood]

 

I love the way you intelligently use existing materials to accomplish your goals. As always, an elegant solution. My first two concerns were how to monitor the upper chambers temperature and also how to monitor the outgassing from the charcoal chamber. You've already addressed those in a simple (simple is good) effective way.

 

I can't keep those hand held infrared temperature guns in the shop. I told the guys that I'm just going to start counting home garages and order accordingly.

 

Let me know if you want some Ti turnings to play with. I want to see how successfully you're able to reduce them to usable fractions.

 

Edited January 12, 2012 by killforfood

[oldguy]

PM sent.

I agree, toilet flush or finger snap "SIMPLE" is a good thing.

 

With a few pipe elbows & some additional pipe you can also move the pipe valve out from between the upper & lower drums & position the valve a foot or 2 to the left or right of the drums.

So, the valve is not in such a hot spot.

 

Posting a pic of an open top steel 55G drum for those who have never seen one.

 

 

Edited January 12, 2012 by oldguy

[NightHawkInLight]

Very cool, the last week I've been looking for barrels just for this use (among others). I was planning on turning it into a burner without a kit. I didn't know they made them, and so reasonably priced! Thanks for the ideas

[dan999ification]

a lovely contained stove and something worth thinking of if the neighbours dont like the smoke [i burn mine off] and you have to keep the mess to a minimum, i know from your last retort that you would let it pressurize to something like 15 psi, proceed with caution if you want the same pressure in here these drums implode at about 15 psi [vacuum] but can take more pushing out, i would keep an eye on the jet/flame before you plumb it in to the lower drum to make sure, the smoke/gas output will change through cooking along with the internal pressure and will have to be controlled maybe constantly if you want to maintain the same pressure [ i still like the pressure relief valve idea if a suitable one could be found].

 

dan.

 

 

[oldguy]

No where near 15 PSI is needed for this to work. A very slight amount of pressure will suffice.

The valve is the one DANGER issue.

Fire this up loaded with the valve closed & leaving it that way would create a nasty situation, as the inner upper drum could burst rather energeticly.

 

So, ALWAYS be careful of that.

 

Before I used a autclave type retort that would take up to 30 PSI. Even then, I only ran it to 15 PSI, so I had a wide safety margin.

I gave up on those, because they wereto expensive, not large enough & I had trouble with the pressure vent contols, as they kept gumming up.

 

 

[M1l2n]

Nice job brother

[Peret]

The valve will probably gum up with tar, especially if it's in a cool area. That could be the weak spot of the design. Maybe a straight clear vertical pipe would be safer? With a 30 gallon drum, even that might build up quite a head of pressure.

[oldguy]

I agree the "valve" is the weak spot in the design.

 

But bear with me, this is only a "design".

Admittedly, I jumped the gun posting the design before I had it built & fully tested.

Only actual testing will determine what, if any modifications will be required to perfect it's functionality.

 

But, I don't think tar (cold, warm or hot) will plug a stainless steel ball valve with a maximum operating pressure of 2 or 3000 PSI. Which is what I intend to use. Certainly, tar is sticky, but it has a degree of fluidity, especial so under pressure & heat. In a sense, the pipe will also be self cleaning, in that as the initial heat drives off moisture as steam. That steam hopefully will help to clean the pipe & valve. The valve could also be removed and cleaned, every so often.

 

The "head pressure" would be dependent on the diameter of the vent pipe.

I intend to use a 1 inch steel pipe & valve for the first test run to see how it works, as that is what I have on hand.

If a 1 inch pipe & valve builds up excessive head pressure running with the valve wide open?

I will simply add another one the same size or scale up to a larger pipe & valve if necessary.

 

Standard mild steel 30 & 55 G drums are generally designed to handle 14 psig.

Typical drums will deform at 8-10 psig and rupture violently at 35 - 40 psig.

So long as this system stays far below that, I see no issues.

To be on the safe side a pop off valve could be added in front of the valve, to insure safety.

 

Because this system has a fire box air inlet that can be regulated, as well as 2 additional flue dampers.

Those heat control features "should" allow for a wide degree of versatility throughout the process.

 

There are a lot of bright minds on the forum.

I certainly welcome any constructive advice on how to improve the design.

 

EDIT TO ADD:

How about I use a 1 1/4, 1 1/2 or 2 inch steel vent pipe & valve to start.

Comments welcome.

Edited January 13, 2012 by oldguy

[dagabu]

I think the design is sound and the ball valve should suffice for building head pressure but I do like the 2" valve for bleeding the pressure off in a hurry. Also, a simple weighted pressure release on top would take care of any concerns of over pressuring.

 

-dag

[NightHawkInLight]

Also, a simple weighted pressure release on top would take care of any concerns of over pressuring.

 

That's a very good idea. I don't think there would be any problems with a 1 1/2" or 2" vent, but you wouldn't want to be surprised. When liquids are boiled off, whether water or oils in the wood, they reduce the temperature which keeps everything happening at a stable rate. When you constrict the vent and raise the pressure it prevents all of that heat from escaping which would raise the overall temperature much quicker than you might expect, boiling off even more fluid and raising the pressure further...It could be a nasty cycle that occurs in a matter of seconds after a minor valve adjustment. Next time you're boiling pasta on the stove you can see just the effect by putting a little pressure on the lid and watching how quickly the pressure spikes. The higher pressure raises the boiling point of any liquids that would be in the chamber which would slow the cycle slightly, but not enough to keep it from bursting.

 

I think I might be exaggerating the danger a little in all I just said, but that's how I try to keep these sort of projects safe when I work on them myself. What's the worst case scenario, and how do I correct for it.

 

Something else a large weighted valve on the top would be good for is the first portion of cooking the charcoal if you're using green or damp wood. If it were just vented into your burner you would be smothering your fire with a cloud of water vapor. If you've got a big weighted valve on top, you can just close the ball valve to the burner entirely for the first 15 minutes or so while things get started.

[oldguy]

I think the design is sound and the ball valve should suffice for building head pressure but I do like the 2" valve for bleeding the pressure off in a hurry. Also, a simple weighted pressure release on top would take care of any concerns of over pressuring. -dag

 

The object of the 1 inch pipe & valve is COST.

I have a lot of 1 inch pipe nipples, unions, elbows, etc, and several valves on hand.

If you go bigger than 1 inch with pipe or valves, cost goes up rapidly.

Industrial quailty 2 inch valves are expensive, unless you find good DEALS on them.

 

So, I am going to try it with 1 inch pipe & valve first.

 

But, with your great & simple suggestion, will add a a weighted pressure relief to the upper inner 30G drum as a safety feature.

I have several large pressure cookers rated to 30 psi.I weighed the pressure relief safety weight on several (rated to operate at 15 psi).

They all weigh 3.5 ounces. So it doesn't take a lot of weight to hold in far less pressure than that.

[dagabu]

The object of the 1 inch pipe & valve is COST.

I have a lot of 1 inch pipe nipples, unions, elbows, etc, and several valves on hand.

If you go bigger than 1 inch with pipe or valves, cost goes up rapidly.

Industrial quailty 2 inch valves are expensive, unless you find good DEALS on them.

 

Good point, I just don't want to hear about you splattered across your property so I suggested the weighted pressure relief valve. Easy-peasy.

 

-dag

[oldguy]

Good point, I just don't want to hear about you splattered across your property so I suggested the weighted pressure relief valve. Easy-peasy.

-dag

 

 

The 30G drum being inside the upper 55G drum, which is closed.

Makes for a wide margin of safety also.

The 30G drum wouldn't blow up if over pressured

It would simply split a seam.

 

But your EASY PEASY pressure relief weight makes it impossibe to over pressure the 30G drum.

Good call on that.

[dagabu]

But your EASY PEASY pressure relief weight makes it impossibe to over pressure the 30G drum.

Good call on that.

 

just lookin out for your Big Guy!

 

-dag

[oldguy]

Assuming the kinks get worked out and my triple barrel charcoal retort design functions as well as I presume. I am looking forward with great anticipation to trying a bunch of differing things with it, besides runs of larger sized alder & white pine. One of the first will be to see how difficult it will be to a “saw dust” run, a planer “shavings” run & a wood “meal” run.

 

What I envision with all 3 is to fill heavy weight Kraft paper grocery type bags, load the 30G drum with the Kraft paper bags and see what it takes to turn out differing types of optimal pyrotechnic grade charcoals out of various types of sawdust, shavings & wood meal. Because the “density” inside the retort would be so low, I assume it would not take long to get the job done.

 

 

[FrankRizzo]

Very cool! Are you using those drum closure rings on the inside barrel as well?

[oldguy]

Very cool! Are you using those drum closure rings on the inside barrel as well?

 

You have to used an open end drum, with a lid & clamp closure ring on the upper inner 30G drum.

Otherwise you would not have access, to load & unload it.

[oldguy]

Still twiddling my thumbs waiting for the cast iron kit parts to arrive via UPS ground.

 

In the mean time I am pondering ways to make this charcoal retort design more efficient.

One of which I suppose would be to insulate the exterior of the upper & lower drums.

 

So, I googled the hell out of so called "fireproof" insulation.

Most of which doesn't appear to stand up to this application.

I want to keep the cost & weight down & don't want it to be butt ugly either.

Any suggestions?

Edited January 17, 2012 by oldguy

[warthog]

I like butt ugly myself. It is how I prove I made it myself. If it looks good, no one I know will believe I didn't just buy it or have it made. I am not the handiest of folks though, if there are no runs in the spray paint, I didn't do it.

 

 

That is easily the sweetest charcoal cooker I have seen to date OG. You rock when it comes to this stuff.

[dagabu]

Still twiddling my thumbs waiting for the cast iron kit parts to arrive via UPS ground.

 

In the mean time I am pondering ways to make this charcoal retort design more efficient.

One of which I suppose would be to insulate the exterior of the upper & lower drums.

 

So, I googled the hell out of so called "fireproof" insulation.

Most of which doesn't appear to stand up to this application.

I want to keep the cost & weight down & don't want it to be butt ugly either.

Any suggestions?

 

Hawthorn fire clay, we use it to mold and patch fire bricks. Runs about $.25 a pound at pottery shops. If you can get asbestos cloth, wrap the barrel in it and pour the Hawthorne slurry (stiff like cement) all around to fill the cavity. It will crack over time but is an excellent fire brick material.

 

Look it up first though, I think there may be another item to add but since its been four years since we made bricks, I don't have clear memory any more.

 

-dag

[oldguy]

Thanks Dag, your suggestion gave me more idea's.

 

I did some more research & found that PERLITE would work, super lightweight & inexpensive in 4 cubic ft bags locally from a hydroponics place.

Also found a local source of Green Stripe fireclay, also inexpensive.

 

What I am thinking is to cut the ends off another 55G drum, then split the drum down the middle.

Then use that as a sheet metal skin around the upper drum, then pour in a slurry of a grout like mixture made of mostly Perlite.

With just enough fireclay & silica sand mixed together to form a workable grout.

 

I might do that with both the upper & lower outer drum.

But, once built I think I will fire it up naked first to burn off the paint & see how hot the temps in the upper drum go.

 

Also might mention you want to use a valve that is WOG (water-oil-gas) rated that has a high WSP (working steam pressure) rating.

So the seats in the valve don't die the first time you fire the rig up.

 

　

Edited January 17, 2012 by oldguy

[oldguy]

That is easily the sweetest charcoal cooker I have seen to date OG. You rock when it comes to this stuff.

 

Thanks for the kind words.

Just hope the sumbitch works as well as I hope.

Cast iron should arrive tomarrow.

Edited January 17, 2012 by oldguy

[dagabu]

Thanks Dag, your suggestion gave me more idea's.

 

I did some more research & found that PERLITE would work, super lightweight & inexpensive in 4 cubic ft bags locally from a hydroponics place.

 

 

DOUGH! What a great idea! Sorry I missed that one.

 

-dag

[oldguy]

Anybody have any idea what the cost verses reward in efficiency is if the outer drums are well insulated?