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New furnace: Bigger bloom.


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Walter and I got together today at my place for another smelt. Over the last few smelts I have been progressively making changes to the furnace and finally converted to a brick furnace. I made the bricks myself rather than purchasing the standard size refractory brick. My design required bigger bricks. I also made a cylindrical shape out of insulating blanket and coated it with refractory cement to give it rigidity. The cylinder became the shaft of the furnace.

 

But less writing and more pictures.

 

These are the bricks already casted and ready to be assembled.

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And here they are put together.

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And the an overall picture of the furnace. This is the second time running this kind of furnace for me and other that taking care of patching up the joints between the bricks during the initial expansion that takes places in the pre-heat, it works really well.

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A peek down in the furnace from the top.

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And here it is running during the pre-heat.

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Feeding the beast.

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Beautiful fire.

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Fortunately everything run very smoothly this time around. The arch was tapped and operated flawlessly

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Here is Walter putting the furnace apart. We started charging at 8:00 AM and finished around 2:00 PM.

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More bricks are being removed.

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Just to give an idea of the degree of erosion of the wall just above the tuyeres. The original width of the brick was 3 inches and this is what was left of the wall.

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And finally the bloom. After charging 33 Kg of ore the bloom weighed at 12.7 Kg. This is not only our biggest bloom so far but also the most compacted and the largest yield yet from this kind of small furnace.

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Here is Walter besides the bloom to get an idea of the size. We managed to break the bloom into 4 chuncks while it was still hot using a hatchet as a hot-cutter. The pieces are still too big to fit in my propane forge so I will need to build a charcoal forge in order to process the steel.

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An here is a final picture of the spark test.

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A real fun and productive Saturday for the two of us.

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Very nice Jesus. Congratulations. What will you name the baby?

 

Thanks Mike. I learned from the pro. How 'bout BBB for a name: "Burn Baby Burn."

 

Do you feel the brick method is easier?

Are you using the same refractory for the bricks?

 

Any plans to make the next set of bricks thicker? That set did get fairly thin.

 

Bricks are much easier. I added vermiculite to my standard refractory mix. I would like to make the comsumption of the brick part of the process (like the Japanese do in their big tatara) but I haven't figure out yet how-to. The bricks at the tuyere and just above the tuyere will need to be an inch thicker if I want to run the furnace longer than 6 hours. But as it is now if I can duplicate the yield of this one running it for 6 hours, the result are very satisfactory.

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Did you use any certain method of forming the bricks.

I've not gotten around to doing my run yet, and might have to wait a bit longer as I just got an order for a blade.

What percentage of vermiculite did you add in?

 

I'm not quite catching the meaning of this bit "I would like to make the comsumption of the brick part of the process (like the Japanese do in their big tatara) but I haven't figure out yet how-to."

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Jesus congrats on the the new baby :D That is a sweet looking bloom. Do you mind sharing your recipe for your refractory and some dimensions on your furnace? I am thinking of doing a smelt this coming spring. maybe I can get a few guys to come down and BBQ some ore.

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The bricks are 11 x 3 x 5 inches each. When stacked up they leave a 8 x 8 chamber inside.

The vermiculite is about a third of the mix. The rest is sand and cement.

 

 

I'm not quite catching the meaning of this bit "I would like to make the comsumption of the brick part of the process (like the Japanese do in their big tatara) but I haven't figure out yet how-to."

The way I understand the Japanese process and I may be completely wrong here since I am just trying to reverse-engineer what little I've seen in video and diagrams but I've never been at one of their tatara events, is as follows: The bottom of their furnace is like a trough. It has a "V" shape that in the begginning of the smelt is quite steep allowing to collect the iron and center the initial nucleation of the bloom. As time goes by during the burn the walls will suffer erosion and melt into slag. That causes the walls to progressively recess toward the outside allowing for more room for the bloom to grow mostly sideways. Is that clear? May be others that have seen Akira Kihara do his thing can describe the process better.

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That sums it up nicely. Since beginning this process (the cheap Dutchman, me, and John, the cheap Celt) have been trying different methods where the furnace can be used repeatedly without consumption of materials. We've given up that hope.

 

The best I can suggest is to use materials that will contribute to the bloom in a positive way rather than contaminating it in a way not wanted. Then expect to pay a price in consumables. I like the variation on a theme that you're using though. There is a Japanese model of the kodai (small furnace) that has three parts with the top two sections suffering less of the abuse of the fire and the bottom being rebuilt each time. The large tatara is rebuilt each and everytime they burn. Keep in mind that the Japanese, the Koreans before them and the Chinese both groups likely learned this from, have good reasons for doing it this way. My opinion is that trial and error is a very efficient teacher, especially when some warlord is stamping his or her feet waiting on weapon grade steel. We've had the luxury of leisure to experiment.

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Nice job, Jesus and Walter!

 

And good point, Mike. I've been continuing research on the iron furnaces in east Tennessee, and one of the big variables in how much time they could spend in blast was the life of the refractories. Admittedly they were making cast iron and running a little hotter, but records show they could get anywhere from two weeks to three months out of a liner. Size may have a lot to do with it, since these furnaces are six feet diameter at the tuyeres tapering to 2.5 feet at the top. The hearth portion was usually lined with hard sandstone instead of brick, while the shaft was almost always brick.

 

Looking at some of the brick I've recovered, they seem to be fireclay grogged with iron cinder. I think that's fairly brilliant, myself. As the brick erodes, the slag continually glazes the liner and contributes iron back into the charge. How's that for a good use for slag? :lol: The sandstone contributes a lot of silicates to the slag, which was needed for the next step of turning cast into wrought.

 

Dang, I love iron... :blink::lol:

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Dang, I love iron... :blink::lol:

 

I don't Alan...most of the time it royally "T's" me off.

 

Well done Jesus and Walter!

 

There is a book out there with some mix recipes for bricks from England......Mike has had it and others for two years now...guess he reads slow.

 

Ric

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Hi guys,

 

Nice work and a nice bloom! :D

 

I've been in contact with Dominique Bargiel, a french smith and one of the best furnace maker in France. He making his brick using kaolin clay and straw with good results.

He has now made three furnaces with them and they vitrified over a centimeter or two and have not moved since...

 

might be worth trying...

 

Antoine

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Jesus what ratio do yo mix the sand and cement? If you don't mind please and thanks for the info.

 

Mostly sand Mike. Just enough cement to hold things together. So I would say 1/3 vermiculite, 1/2 sand and the rest cement.

 

It is all trial and error. Each time we run one of these things we learn a thing or two. Then we apply that to the next one.

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If I may press for one more detail, are you using the white or brown vermiculite? I think the rest of us want to avoid as much as the "error" part of our trials...

 

Thanks for showing us what you've done so far, it is inspiring and educating. Time to get busy.

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There is a book out there with some mix recipes for bricks from England......Mike has had it and others for two years now...guess he reads slow. Ric

 

Slow covers it. The day job stuff gets read pretty quick. This stuff is like a fine meal that requires digestion.

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If I may press for one more detail, are you using the white or brown vermiculite? I think the rest of us want to avoid as much as the "error" part of our trials...

 

Thanks for showing us what you've done so far, it is inspiring and educating. Time to get busy.

 

 

I did not know they had different types of vermiculite. The one I used is golden color. I just walked to the garden supply store and asked for vermiculite. It came in a huge bag that was light as a pillow full of feathers. Another advantage is that it made the bricks a lot ligther and easier to move around.

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Jesus, I guess the part I was confused on was that the walls were already eroding, so I thought maybe there was something more to it that I wasn't already getting.

So you're wanting them to erode more to add slag...so I was kinda thinking "Hrm it already kinda does that so what's he mean" :huh:

You're meaning more in a controlled method?

 

Might have to give the bricks at try instead of the shell method. Be easier I think making them.

Just make up a form and have a go at casting them.

 

 

So a wooden form like regular bricks, then let them have a while to dry out...did you do any curing before hand?

Definitely sounds like fun, I'll have to make up some forms when I get a chance.

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That's right. Trying to control the rate of erosion to allow the bloom to grow from the center of the furnace.

 

Here are the forms that I made to cast the bricks.

 

IMG_8816.jpg

 

IMG_8823.jpg

 

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The first time I run this kind of smelter I cured the bricks with a slow fire. This time I did not. There was quite a bit of steam during the pre-heat and expansion of the joints between the bricks. In retrospect I should have cured the bricks before hand again. Also the vermiculite contains quite a bit of water in it.

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Outstanding.

 

When you say "cement", though, are you using regular portland cement, or something more exotic like satanite or mizzou?

 

 

And Ric, do you remember where you got those pre-cast wool tubes we used at Harley's? I forget what you said before.

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Hi Jesus

 

Thats a one off biggest blooms that i have seen comming out of that type of smelter....GREAT WORK.

 

Jesus you try to get contoll of this erosion in side the smelter, right?

That 2 run of mine whit new desing last summer did work but slag is kinda problem...at least i think in my desing.

Clay, sement,sand did had sevire erosion but slag blugged the airholes...this was also my mistake..they where too low??

I learned that it´s damn difficult and lots of work and if i dont greate som remedy for it....maby i let it be.Brick desing works just nice,

so it only gives a headage if it dot work.

 

This desing of your looks realy good, smaler upper part and bigger lower part ( in side dimentions)

SO i just thiking here but.... can it work just fine if lower part is say 20" diam inside and upper part is 10"

Just like your desing but pit bigger scale?

 

Jesus im intersted fuel ration? How much charcoal was used? How about preheat time?

 

Damn guys....its allmost winter here..and im dyeing to run new bloom....it´s so much fun :lol:

 

Great work

 

Niko

Edited by Niko Hynninen
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Thanks for the pictures Jesus...the forms were kinda what I had in mind.

Definitely gonna have to get around to making some bricks, sounds easier than the shell, I'd bought a piece of stove pipe to use for the center for casting the refractory, maybe I'll just turn that into a mini forge now.

 

Any special refractory mortar between the joints or just good old furnace cement?

 

Niko, winter would be a nice time for a smelt, nice and cool with a hot fire =P

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