Pit Charcoal

[Jan Ysselstein]

Each year I burn wood debris created during cleaning, branch trimming and stuff created by fallen trees. Burning this material in/over a pit seems to create a better fire ( less smoke) and provides the opportunity to save the charcoal created . Below are some pictures of the process, I think they are self explanatory ...at about 15 hrs after covering the pit the steel plate is still to hot to touch...indicating high heat capacity of the content ( may not be good news) or the heat held by new brick pit is something I need to become familiar with, or air is somehow getting in.

I do not recommend this method nor the charcoal it produces ( very soft and friable and lots of fines) but I need to do this anyway and hate to see it all go up in ash and smoke. Here are some pics,

 

The steel plate can not be removed until the metal feels cold..Hole is 4ft deep 4 ft diameter...

By the way there no smoke created during this process.

Jan

 

Edited February 11, 2014 by Jan Ysselstein

[Jason Brown]

Very interesting. Got me thinking about an in-ground yard waste/charcoal powered smelter. Mine will have to have an air supply pipe.

[B. Norris]

Jan,

 

Researching for my own charcoal burns (now curtailed by the local Fire Department,) a common theme was to carefully place the wood into the pit and to start the burn at the top. I assume you get better conversion to charcoal when the bulk of the wood is not afire causing too high temperatures. In this instance, you want lots of smoke because, when it disappears, that is when the fire is getting too hot and signal that it is time to cut off oxygen.

 

~Bruce~

[Jan Ysselstein]

Jason,

 

Burning any slash, first thing is to get a good burn going under the fire..yes that is firewood at the beginning of the burn. In a deep hole air is sucked down to replace the air that has been heated and rising ....you really have to make sure you do not bury wood before it is charring, that is a problem and this burn took longer because I had to slow down to prevent blocking air going low into the furnace. I think you will find the charcoal and smelting better be kept as two distinct activities.

 

Bruce,

I do not want any smoke and am required to burn that way by the local clean air board , creating smoke is the surest way to have burning regulated to extinction. I will post a pic when I uncover the plate...the evolution of gas by the heated wood in the pit supports the burn ( = a flame) and prevents a lot of ash being generated. I am on a learning curve here as I would like to be able to control where the gasses come up and the cold air goes down.

When you say smoke I say flame.

Jan

Edited February 12, 2014 by Jan Ysselstein

[Jan Ysselstein]

I have a charcoal buying problem, Cowboy is too expensive and lousy, homemade is a lot of work and eventually backyard burning will not be allowed, Mesquite sparks a lot and has a lot of ash ( I have no idea what the ash composition is)...I am hoping it is not too refractory.....or my slag will become impossible to process .

On two occasions Phil Baldwin was to weld some wrought iron with Mesquite and he said he could not do it and had to switch to coke and coal to complete the job ( that kind of scares me).

 

I made some iron (steel?) today using 100% Mesquite. The main concern is the ease at which I can work the slag in the resulting metal ( if there is any resulting metal ). I did take some pics. as soon as I see the metal I will forge some to see if it welds and cleans up.

 

Mark,

When I opened the bottom of the furnace I heard some fizzing ...just like opening a soda bottle...have you ever heard that sound..I am taking it as a good omen.

Jan

Edited February 12, 2014 by Jan Ysselstein

[Matt Todd]

In my experience with making charcoal I have found that "baking" the wood works best by using the retort method. I use one 55 gallon drum and the bottom third of a second 55 gallon drum. I fill the top drum with wood to become charcoal and the other third piece I build a fire with scrap wood and "cook" the batch for several days. I can retain 90% of the wood I started out with for my charcoal batch. It makes for pretty good charcoal with only a little spark, not as good as Japanese charcoal but it works.

[Jan Ysselstein]

Matt,

Way to go.

 

Jan

[Matt Todd]

Thanks jan, I forgot to say I'm impressed with your pit. I bet you could smoke a whole pig in that thing

[EricS]

Jan I like your pit. Looks like a great solution for you situation. I have recently built a retort that produces excellent CC . The amount of smoke is minimal as the smoke from the wood gassifying gets burnt in the process. Here are a few pics

This is hickory I like how all details of the wood remain intact.

[Jan Ysselstein]

Eric,

Thanks for posting that unit....it looks very well built . I opened the pit yesterday. Made some cast iron and had to wet some mulch and cover the pit again as it was stil burning. Tomorrow I will try again. The fines ( about 50 percent) contain lots of material which should be good for forging or heat treating fuel. I am experimenting with some means of burning this material very evenly over a length of a typical knife.I will post some pics when I get it resolved .

Jan

[Jan Ysselstein]

Here are some pics of the full pit, unsorted charcoal and The Little Furnace that should ( I hope). The furnace only has 14" above the air inlet ..which is ideal for a friable fuel such as I am producing...it is capable of making cast iron ( because I was operating at the end of Darrells "N" carbon concentration curve) I will dial it in over the next few runs ( I am just as glad to get cast iron as heterogeneous iron blooms).

 

Jan

[Daniel Cauble]

I also just recently built a retort similar to EricS's. Creates really good charcoal and I have a ~75-80% recovery rate. Made a video yesterday with the gasses burning off the wood.

 

[B. Norris]

How does the retort work? Is the barrel totally sealed and if so where do exhaust gases go? What fuels the retort? Is the larger diameter pipe just open at the bottom?

 

~Bruce~

[Daniel Cauble]

http://www.iforgeiron.com/topic/33683-charcoal-retort-very-successful-model-pic-heavy/ <--This particular design belongs to Ian there.

 

Not sure if you can see pics there unless you join.

 

The larger diameter pipe (in my case 7" sch 40 steel) serves as the firebox. It is sealed to the barrel by means of a flange (In my case, I had to fabricate one). I build the fire in that box by loading wood into it by the 4" pipe I have welded to the firebox. The firebox is open on the bottom for the upward draft, with a grate to hold in coals and heat. The firebox also has 1/2" holes drilled into it after it enters the barrel. With the top of the barrel sealed, the only place for the gasses to go is through the holes of which ignite one it reaches proper temp. From there it works similar to a jet engine or venturi. Also note that a 4" pipe is welded to the firebox by means of a bought or fabricated transition. You can see it in EricS's post.

 

Depending on your design, it can be self-sustained in an hour, or in my case 3.

 

EDIT: It is also an insulated barrel. It acts like an oven. By slicing another barrel down the middle and welding it back together with a smaller diameter than what you began, it is placed inside, and the resulting space between both barrels is filled with insulation, and sealed at the top.

Edited February 13, 2014 by Daniel Cauble

[B. Norris]

Aha! Thank you. I do not have a place to burn myself but, a friend does and he uses charcoal too.

 

~Bruce~

[Jerrod Miller]

This may be a silly question, but it is the only part I am having a hard time wrapping my mind around. I may be wrong about some of my description below and that could be what my problem is. If someone knows, please let me know where I am wrong or what I am missing.

 

The beginning of the conversion to charcoal has the wood putting off a lot of gas. This gas displaces the oxygen in the wood chamber therefore the gas will only burn once it leaves the chamber and finds some oxygen. When the process is nearing the end the wood (now charcoal) is giving off less and less gas until it can no longer burn. When there is that little gas (some, but not a lot) coming off the wood that means there is not a lot of pressure in the charcoal chamber. So what keeps the flames at this point from going into the chamber and igniting the charcoal with a little breeze of air from the inlet pipe? Also wouldn't it be a problem once all the gas is done, but the system is still very hot and a bit of air blows in? Is it that this does happen, but just smothers itself fast enough to not be a problem?

 

Half of the above I pieced together as I typed it, so I think I answered myself. If anyone could confirm or correct it I would be grateful. Thanks!

[Lee Sauder]

Jerrod- That can be a problem if your retort is leaky, but think of it this way- it takes two holes to make a breeze. Especially two holes at different heights to create convection.

[Jerrod Miller]

That is kind of what I figured, that any swirling of air through the inlet->chimney would be pretty negligible in terms of leaking into the charcoal chamber (assuming you have no leaks in it besides the designed gas holes). Thanks Lee.

Oh, and thanks Jan, Daniel, and Eric for all the info posted here. This project just moved up on my to-do list.

[Jan Ysselstein]

Jerrod,

Glad you like the topic. I am just about done with the pit full of charcoal...1 batch of cast iron, 1bloom of cast iron and slag...one bloom still in furnace as the rains started. The last furnace shaft is better suited for the charcoal size ..I went down from 14" diameter steel shaft to 10 inch refractory lined steel.

This charcoal requires no chopping and with the new furnace diameter my waste is now down to 30% ( as I can add more small pieces) . I was a little surprized at how this brick lined charcoal furnace worked...there were no large lumps of charcoal in the pit at all..normally I have to recycle a few thick pieces. This system retained a lot of heat and allowed the process to continue way beyond what I had experienced in the past

I may have enough left for a very short run.

The Mesquite charcoal test wast a bust...however a little fragment of metal gave an insight into the cooling of very pure white iron.

Jan

[Jan Ysselstein]

"I may have enough left for a very short iron run".

 

 

The last of the pit charcoal (run#1) filled up 1 55 gallon drum ...which I used up today on a short iron run...it was easy to calculate the % fines ( by volume) using the drum, I am not using 25% of the charcoal due to fines.

I have no idea how much iron I put into the furnace as I had to screen out fines and measure ore at each addition...1 gallon of charcoal to 1 lb. of ore...and even with a 10" diameter stack, I could barely keep up. Every time I turned around the level had dropped 5-6 inches or so.

 

A while back I did this process with only pine wood and the resulting blooms are blue in color...Tomorrow I will have a look at the color of this bloom ( if I have a bloom) to see if pine wood was a variable in the color of the metal.

 

The second batch of charcoal ( made yesterday) is sitting in the pit and should be enough for 3-4 runs. This burn was a little tricky and required the occasional use of a leaf blower to keep the fire lively and smoke free. If this has not cooled by tomorrow I will inject some CO2 into the pit.

 

A grate for burning the fines is needed..I have gathered some volunteers for experimentation and am open to suggestion ...a grate for burning charcoal fines ( 1/8" to 3/8" diameter bits).

 

Jan

 

 

[Jan Ysselstein]

OK...

 

Let's take a look at yesterday's run ...guessing at the numbers I had 50 gallons of charcoal but only used 75% or 37 gallons .....it takes 20 gallons to start my furnace ( filling and a little warm up). I must have used 17 gallons during the run = 18 additions of about 1lb. each ( by volume). I did pick up some dropped/spilled bits and can assume 20 additions were added =+/- 2 additions.

 

Twenty # of magnetite has a total Fe content of about 14 lbs Let's look at what we found,

 

Two completely separate blooms were found 1 at the bottom of all cast iron 4# (cleaned)

1 above the bottom bloom of all steel at 4# (cleaned)

Cast iron bits and pieces totaled 2#

Partially reduced iron ore, magnetic fines which when burned with a torch show burning iron 1.5 #

 

So 11.5# / 14 were recovered or about 80% the bloom products yielded about 57% of the total iron added or 40% of ore weight added.

 

The high yield is of no particular advantage if the labour involved is high...but it is fun to see where the stuff goes.

The stack and the ceramic air inlet survived the run and the furnace is ready to go. The charcoal in the pit (run#2) is cooling and the next run is planned.

Here are some pics of the results

Jan

Upper bloom, as charcoal cover was removed

Cleaned cast iron bloom ( I may save this as a little sculpture)

Cleaned upper bloom

Every thing together

 

Jan

Edited November 24, 2014 by Jan Ysselstein

[Jerrod Miller]

Any comments about the blue tint you referenced yesterday? Did you see it this time too?

[Mark Green]

Jan,

So, I assume, you wanted these results?

The cast, and steel blooms.

By cleaned, you manually clean them by breaking off the slag that will detach, with a hammer? Cold??

You just let the fire burn down? With/without air on? What is your air pressure/vol.

 

Great return.

Have you smelted using a door/plinth design, where you can remove the bloom, and knock off most of the outer slag while hot?

 

That cast lump would make a great piece of art.

 

Cool.

[Jan Ysselstein]

Jerrod,

I found some blue steel on another bloom from earlier in the week, blue color is not due to Pine Charcoal but may be related to using rice hulls in the furnace bottom. The blue must be some vapour deposited layer of silica/iron/oxygen ( maybe).

 

Mark,

Remember the song "You don't always get what you want, but if you work real hard, you will get what you get ". I seem to have a very hard time guessing what a bloom will be like by looking at the outside. What I wanted is..... solid blooms of low carbon iron ( until I cut some with a chop saw I did not think I had that...but now I do)..I will always take cast iron , especially clean cast iron.

 

Cleaned, is cleaned cold with a mining pick and axe. I let the fire burn down with air and cover the metal can with rice hulls until it all cools. I have not used the door method as I do not tap slag anymore I just struggle with it cold..when I get my press finished ( waiting for parts from FedEX ) I will be fishing the bloom out of that furnace with tongs while it is hot...maybe I can send something down the shaft to really liquify all the slag.

 

I have no idea what my air pressure and volumes are ..I do use a regenerative blower, once set, if flow rates change and do not come back, I know I am into a problem ( first thing I do is clear the air inlet) . I look at the flame and compare it to the length of the furnace above the air inlet....this furnace flame was two heights...when I got close to the furnace I could feel iron sand raining down on me. Based on some reading about Indian furnaces..I started the fire in the shaft when the shaft was 2/3 full of charcoal and watched the heat travel down to the air inlet.

 

So the first pit furnace run gave me 4 runs , two of the blooms I am not cutting..one is cast and impossible to cut..the other is not too pretty either. This Friday afternoon I should have a chance to forge some of this material.

By the way these clay sleeves are about $25 each ( good for two runs I hope) and I hope to make the whole lower structure out of just sand/clay/? kind of a ganister.

 

Jan

 

This is what was smelted with run 1 of the charcoal pit, todays blooms on the left

Edited February 20, 2014 by Jan Ysselstein

[Jan Ysselstein]

Planning the next run.

 

There is a bit of a frenzy at play as I only have a very small window of opportunity to have a charcoal smelting fire outside, due to severe drought conditions in California.

 

Cast iron, I have two options here ( hopefully later today)

 

1) remelting/reducing all the bits and pieces I have collected by cleaning the blooms ( I will post a pic when I do it ) lots of this material is a mix of iron and slag,some has

cast iron attached. Pre reduced iron ore will also be added.

 

2) Repeat the last run, paying attention to what was happening during the first 11 additions ...let's say the furnace is about 43" deep and each ore addition is preceded by a

charcoal addition of 1 gallon or about 5" in the furnace shaft.

Addition 1 saw the whole shaft full of charcoal ( including its allottd 5") or 38" of "free" charcoal

Addition 2 saw the whole shaft full of charcoal minus the 5" allotted to addition1

Addition 11 did not see any "free" charcoal other than its 5" allotment

 

So sometime at about addition 10 or 11, the furnace characteristics changed ..on the next run I will make sure each addition has more than its 5" of charcoal for reduction....either by adding 1.5 gallons per pound of ore or by adding an additional gallon of charcoal say every 5th addition.

 

I can also wrap a blanket round the furnace to keep the wind from cooling it as I am committed to the Fe3O4 to FeO to Fe route..which requires higher temps.

 

If we get a couple of good clean cast iron runs we can have a look at reducing cast iron to steel. I have 4 methods in mind and am sure some of you will be adding some to that list.

 

Jan

Edited February 20, 2014 by Jan Ysselstein