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The Catalan forge... "Farga Catalana"


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Interesting picture. Looking at the placement of the tuyere in relationship to the depth of the hearth and surrounding walls makes me reconsider the strict separations between a stack furnace and a simple hearth and whether or not it would be possible to smelt in a hearth and not just re-melt.

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I am not sure we can rely on the tuyere placement after the rebuilt which only happened a few years ago from the ruins of the old shop.

If I were to trust my intuition, I don’t think the current tuyere height is correct…

forn%20farga%202.png?psid=1

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Great stuff Miquel! Looks like a nice bloom.

 

Zeb

 

 

The bloom is beautiful by itself. Sometimes I feel bad when I hammer it down. I think will keep this one as a museum piece…

miquel.

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Your project is really very interesting.

I can feel the fire in your Farga and in your minds and hearts!

 

Looking forward to follow your progress.

 

The best about a new experiment is finding again something lost in time…

 

miq<uel.

Edited by miquel
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Experimental data from running the Catalan Forge.

... Preheat 3 hours.

... Charging time 4 hours.

--- Charcoal:

Initial charge 40 kg. Most of the combustion takes place near the tuyere. We added an additional 30 kg for a burn rate of 2.91 kg of charcoal every 10 minutes.

--- Ore: 22 Kg of hematite and siderite.

--- Bloom weight: 7.5 kg.

... Final yield: 34.09%.

--- Charcoal consumption per kg of metal produced: 9.3

 

For a first experience, we are very pleased. In the next we hope to increase the ore by and additional 15 or 20 kg.

 

miquel.

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Miquel,

Thank you for the details, I am sure those numbers will change as familiarity is aquired. What stood out in some of the pictures is the charcoal seize ..it was large when compared to us users of narrow tube furnaces and regenerative blowers. Did you cut the charcoal or use it as is?

 

Jan

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Miquel,

Thank you for the details, I am sure those numbers will change as familiarity is aquired. What stood out in some of the pictures is the charcoal seize ..it was large when compared to us users of narrow tube furnaces and regenerative blowers. Did you cut the charcoal or use it as is?

 

Jan

 

 

We did chopped the charcoal but we did not think that going smaller was necessary. What do you think? Chopping it to a smaller size will result in more loses to fines and dust. The size we have used seems to allow for good combustion.

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We noticed significant differences in the burn rate and the yield in terms of charcoal burned per kg of bloom produced when comparing our data to that of the antique Catalan forges.

Data from antique Catalan forge:

... Charcoal used 544 kg.

...Charging time 6 hours.

Burn rate: 14.9 kg charcoal every 10 minutes.

... Ore 487 kg.

... Bloom 151.6 kg.

Yield: 31.1%

... Charcoal burnt per kg of metal produced: 3.58

In addition to the above, in the old furnaces they added 100 liters of water. It is not clear why. May be to increase gas formation or to increase the temperature, or both.

miquel.

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Miquel,

The only problem I have ever had with charcoal is when it was made too fine...some of us get away with using relatively small charcoal because we have high pressure blowers. I would stay with coarser charcoal in the furnace ...there is a good write up in English in John Percy's book...

 

http://books.google.com/books?id=RYpBAAAAIAAJ&printsec=frontcover&dq=JOHN+PERCY+IRON&hl=en&sa=X&ei=4RUKUceoOeamiQKK2IG4DA&ved=0CD8Q6AEwAw#v=onepage&q=JOHN%20PERCY%20IRON&f=false

 

The recurring concept I run into when reading regarding the Catalan process is a period 1-2 hrs when the ore is being reduced at a lower temperature than the later part of the process.

Jan

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In the old Catalan forges they used very finely chopped charcoal, even mixed with fines to slow down the burn rate in the foremost half of the furnace.

We ruled out that possibility because our oven wasn’t as big as the originals and we were afraid of chocking the process.

In the data that I have of the original operation, the air pressure increases progressively during the run. Nobody knows what unit of measure they used, they wrote as a “?“ but we can get an idea of the progression. An increase in the air pressure meant an increase in the operating temperature.

At the beginning and for 10 minutes they used 18?.

From minute 10 to 75 they used 8?.

From minute 76 to 142 they used 10?.

From minute 143 to 184 they used 14?.

From minute 185 to 230 they used 16?.

From minute 231 to the end they used 18?.

In our experiment we increased the pressure when we noted that the charcoal column in the foremost half of the furnace started to diminish.

miquel.

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Miquel,

Thank you, that tells a lot. You may want to ask your interpreter to organize a fundraiser here (on this site) of some kind, to help you with your charcoal purchases ( I will gladly contribute ). By the time this gets nailed down you are going to spend a lot of money on charcoal.

 

Jan

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Miquel,

Thank you, that tells a lot. You may want to ask your interpreter to organize a fundraiser here (on this site) of some kind, to help you with your charcoal purchases ( I will gladly contribute ). By the time this gets nailed down you are going to spend a lot of money on charcoal.

 

Jan

Jan,

 

What you are proposing is not a bad idea at all. People like Miquel, you and I and many others have spent our own energy, time and money to advance the knowledge of smelting and then share freely what we have found out on the forum. It would certainly help to have some sort of contribution to further our research but I would not want to do anything without the permission of the forum moderators and making sure that they is a clear understanding as to how the funds would utilized. In other words, there would need to be a clear accountability process.

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Great stuff Miquel!

 

With the historic numbers, Was that one large bloom, or a number of smaller ones? I would think it would be very tough to get a 150kg bloom out of the furnace.

I would think that a lot of the difference in the numbers, is due a lot to experience. Once you have a dozen or so under your belt, I will bet that these numbers get a lot closer. Plus, if you had a good stout gang one day, you could try to make 3-4 blooms at a time. With the furnace hot, and feeding in the next charges, I would think a lot of burn energy is saved. Plus you don't have that huge starter fill. That is where a bunch of your total came from.


The water may have been used to slow the charcoal while a bloom was removed, and things were set up for the next run.


Great fun mate!!!! Keep up the good work.

 

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So, reading the description in the book above. the water is used to make a mass of damp, packed charcoal fines, above the layered in charges. Then the bellows is cranked up, and the process moves on from there.
very cool old book. Thanks for sharing Jan

If this description is accurate Miquel, you should follow this recipe next time and see what you get. It looks like what you did on your first run was very close.
I'll bet the damp charcoal trick is the key though.

 

Cool stuff. Just makes me want to go out there and build one of these again. Now that a have a bit of a clue how it all works :)

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Miquel,

 

" In the old Catalan forges they used very finely chopped charcoal, even mixed with fines to slow down the burn rate in the foremost half of the furnace.

We ruled out that possibility because our oven wasn’t as big as the originals and we were afraid of chocking the process.

In the data that I have of the original operation, the air pressure increases progressively during the run. Nobody knows what unit of measure they used, they wrote as a “?“ but we can get an idea of the progression. An increase in the air pressure meant an increase in the operating temperature.

At the beginning and for 10 minutes they used 18?.

From minute 10 to 75 they used 8?.

From minute 76 to 142 they used 10?.

From minute 143 to 184 they used 14?.

From minute 185 to 230 they used 16?.

From minute 231 to the end they used 18?.

In our experiment we increased the pressure when we noted that the charcoal column in the foremost half of the furnace started to diminish."

Miquel,

Here is a graph bloomery operators should have some familiarity with..especially those of us who may want to shift gears during the process,

What is missing is the conversion of Hematite to magnetite which I have in another book (which I cannot find right now). Hematite to Magnetite will happen even if the percent CO is not that high, but it does require some heat. The Kelvin scale has the same units as the Celsius scale Celsius= Kelvin minus 273 Zero K = absolute zero

This wet paste of charcoal powder and very fine iron ore keeps coming up in the literature..in some of the historic methods when the author states "a little water" I assume he/she may mean " a little water" or may be meaning "a little water and clay mixture". In the case of the Catalan forge I am sure there was lots of clean water around and the former was intended.

It is possible the paste of charcoal and iron ore was added to redirect the hot reducing gasses in the furnace and forcing them through area of the bed of mostly ore..if this creates a greater resistance to flow it would also slow down the burn rate (though that may not have been the primary intent). The nice thing about that paste is , when the water is gone and there is no cohesion left, the charcoal does not become a blocking mass but flows out with the hot gasses.

Jesus,

At one time there was a fundraising effort to pay for forum operating expenses and using PayPal it seemed to go pretty smoothly. I would not worry too much about the accountability factor.

Jan

Edited by Jan Ysselstein
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Jan wrote:

"It is possible the paste of charcoal and iron ore was added to redirect the hot reducing gasses in the furnace and forcing them through area of the bed of mostly ore..if this creates a greater resistance to flow it would also slow down the burn rate (though that may not have been the primary intent). The nice thing about that paste is , when the water is gone and there is no cohesion left, the charcoal does not become a blocking mass but flows out with the hot gasses."

I'll bet that is right on the money.

Mark

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Great stuff Miquel!

 

With the historic numbers, Was that one large bloom, or a number of smaller ones? I would think it would be very tough to get a 150kg bloom out of the furnace.

 

I would think that a lot of the difference in the numbers, is due a lot to experience. Once you have a dozen or so under your belt, I will bet that these numbers get a lot closer. Plus, if you had a good stout gang one day, you could try to make 3-4 blooms at a time. With the furnace hot, and feeding in the next charges, I would think a lot of burn energy is saved. Plus you don't have that huge starter fill. That is where a bunch of your total came from.

 

The water may have been used to slow the charcoal while a bloom was removed, and things were set up for the next run.

 

Great fun mate!!!! Keep up the good work.

 

 

In the old Catalan forges a single bloom weighting 150 kg (330 lbs.) ?was made at a time. Any leftovers remained in place and became part of the next bloom.

They operated the furnace six days a week in shifts of 12 hours each. Each shift made two blooms.

Our next plan is to make two blooms in a row.

 

 

miquel.

Edited by miquel
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Here is a graph bloomery operators should have some familiarity with..especially those of us who may want to shift gears during the process,


attachicon.gifPredominance.jpg


What is missing is the conversion of Hematite to magnetite which I have in another book (which I cannot find right now). Hematite to Magnetite will happen even if the percent CO is not that high, but it does require some heat. The Kelvin scale has the same units as the Celsius scale Celsius= Kelvin minus 273 Zero K = absolute zero



This wet paste of charcoal powder and very fine iron ore keeps coming up in the literature..in some of the historic methods when the author states "a little water" I assume he/she may mean " a little water" or may be meaning "a little water and clay mixture". In the case of the Catalan forge I am sure there was lots of clean water around and the former was intended.


It is possible the paste of charcoal and iron ore was added to redirect the hot reducing gasses in the furnace and forcing them through area of the bed of mostly ore..if this creates a greater resistance to flow it would also slow down the burn rate (though that may not have been the primary intent). The nice thing about that paste is , when the water is gone and there is no cohesion left, the charcoal does not become a blocking mass but flows out with the hot gasses.



Jan




Charcoal fines, ashes and water. It’s likely that the theories are correct and we suspect so, but the behavior in a smaller scale furnace may be different.


miquel.

Edited by miquel
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Miquel,

 

I think scaling things down will create a lot of problems ( do you run down the street and tell the neighbors not to hang out the laundry on a smelting day?) . I looked up the two iron ores you are using and looked at the heating pattern of the old Catalan forge process that you posted. The ores have calcining temperatures at which what remains is porous and very reactive...if the calcining happens at too high a temperature the porosity will decrease. So the old timers got the furnace hot at #18? to make sure carbon monoxide was being formed then ran slowly to calcine/reduce the ore.... .

By the way the "S" curve on that graph is the Carbon/CO/CO2 equilibrium curve...though nothing is really at equilibrium in a furnace, it does give one an idea of the temperature at which CO becomes very high in concentration.

 

If you have a PayPal account send me a PM and I will contribute a little to your charcoal kitty.

 

Jan

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Thank you, Jan. Very generous of you. I am eager to try again and if I need your contribution I will let you know.

In the meantime, next time will have a “paella” dish ready for you…

 

 

miquel.

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My apologies Mark, I remember you very well.

 

 

Mark Green

Publicado 24 de enero 2013 - 17:09

Was it a pain, to clean the slag out from the bottom of the smelter, after the smelt?

One of the? mistakes we made was that we could not figure out a way out for the slag. It settled at a lower level than we thought it would. After removing the bloom and stopping the trompe, we could hear the slag bubbling at the bottom of the furnace. Part of the slag was in contact with the tuyere and there was some erosion in the tuyere at that spot. After the slag cooled down and solidified it was very easy to remove it.

miquel.

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