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miquel

The Catalan forge... "Farga Catalana"

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Hello everyone from Catalonia.

We are a couple of friends, Josep and Miquel and we have been smelting since March 2008. We have tried many different furnace designs in the last few years which you can see here: http://www.youtube.com/user/mikquels

 

Just over a year ago that we started our current project. An iron oxide reduction furnace based in the process developed in Catalonia during the 11-19th centuries: "The Catalan Forge."

Since antiquity, iron had been smelted in different furnaces by layering ore and charcoal over several hours and most of this furnaces suffered from a low yield ratio. The Catalan forge was in its time renowned for the increased yield and the improved quality of the iron produced. The operation of the Catalan forge is quite unique, as most the ore introduced in the furnace is loaded in the first charge.

The furnace is a short hearth in the shape of an inverted pyramid. A distinctive trait of the Catalan process is the air supply being carried out through the use of a copper tuyere and a water trompe.

 

Through all the documentation that I reviewed for this project, the only constant is that there were no consistent dimensions for the furnace or a routine procedure to run it. There is information available about the dimensions of specific “fargas” (furnaces) and each one of them has different dimensions, wall tapers and tuyere sections. It is said that the first order of the day when the “foguer” (furnace foreman) was replaced was to take down the previous furnace and built a new one to his own specs. The “foguer” was responsible for the technical details, operation and ultimately responsible for the quality of iron being produced. There were no fixed dimensions and everything was done by making an educated guess.

We built ours proportionally smaller than the originals to accommodate our own limitations. We did not have a stream of water to feed the trompe but we came up with an alternative solution as you will see in future posts. Making the copper tuyere was also challenging as you will see.

Let’s start with the furnace construction. Square plan using regular bricks joined with refractory mortar. More to come…

 

 

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Thank you, Miquel. I am so glad that you have decided to share your experiences here. There is a lot to learn from your experiments.

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Welcome Miquel!!!!

 

Can't wait to see this puppy in action. I heard a water powered air supply may be in the works for this. Awesome!

 

You should post your copper tuyere making experience here as well. Lots of people would love to see that.

 

Good to see you here. Thanks for sharing.

 

Mark

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Thank you, Miquel. I am so glad that you have decided to share your experiences here. There is a lot to learn from your experiments.

 

After a few years of learning from the posts in this forum, I am happy to be able to give something back.

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Welcome Miquel!!!!

 

Can't wait to see this puppy in action. I heard a water powered air supply may be in the works for this. Awesome!

 

You should post your copper tuyere making experience here as well. Lots of people would love to see that.

 

Good to see you here. Thanks for sharing.

 

Mark

 

 

Mark, thank you for your welcome. As time permits, ?I will post the information about the water trompe, the copper tuyere, the furnace and the masser.

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Very cool! Thank you for posting your expiriments, I'm very interested in the trompe as well.

 

Zeb

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Hello everyone from Catalonia.

We are a couple of friends, Josep and Miquel and we have been smelting since March 2008. We have tried many different furnace designs in the last few years which you can see here: http://www.youtube.com/user/mikquels

 

 

Miquel,

Welcome and thank you for posting what is going to be a very interesting experiment.

 

Jan

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Here is the description of our water trompe.

 

This is quite an ingenious way of blowing air into the furnace. It is based on the Venturi effect and it is the most characteristic element of the Catalan forge. I would say, it is its defining element.

 

The trompe allows for an adjustable air flow with little maintenance issues and no physical effort compared to bellows.

 

In our first test we build the trompe using round pipes made from transparent methacrilate so we could see what was happening. We soon realize a problem: the water and the air were spinning down the pipe instead of running down the pipe due to the Coriolis effect.

 

The antique trompe which we had seen were made using a square pipe with a section of about 7.5x7.5". We did not realize the importance of the square section. As it turns out, the square section provides the most efficient and speedier flow of water.

 

Since our furnace was built to about 50% the size of the originals, we also reduced the section of the trompe proportionally.

 

 

We then moved to using a square pipe 4x4". After some calculations of volumen, pressure and speed, we figure out that the ideal flow would be around 220 gpm. We could only manage to get two pumps rated at 90 gpm for a total of about 180 gpm.

 

Three sections adding up to 17 feet.

 

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This is the top section with the water return with an adjustable narrowing and air entry ports. Since we did not have a stream of water to feed the trompe, we opted for using the water pumps in a closed circuit.

 

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Detail of the adjustable choke and air ports.

 

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We put a window in the top section to monitor water flow.

 

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This is the reservoir where the water and air mix is separated.

The blue hoses are for the water return and the red for the air.

 

 

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Here is the trompe at half power operating on one single pump.

 

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Edited by miquel

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Very impressive! Thank you so much for sharing this, I may have to build a similar trompe. Am I correct that the height of the water column has a direct effect on the air pressure? Water velocity at the venturi effects air volume?

 

Zeb

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Thank you Miquel, this is fantastic. I have wanted to play with this idea but haven't got to it- now I can just watch yours! I will be interested to see what effect you think the moisture has on the smelt, and what other advantages and disadvantages you find. I bet it sounds nice!

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So very cool Miquel!!!!

Thanks for sharing.

 

Mark

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Seriously cool indeed! Thanks for doing this, the importance of the square pipe had not occurred to me.

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Very impressive! Thank you so much for sharing this, I may have to build a similar trompe. Am I correct that the height of the water column has a direct effect on the air pressure? Water velocity at the venturi effects air volume?

 

Zeb

 

 

To improve efficiency we looked into the water flow, the height and section of the pipe. Too short and the air pressure will be lost. Increasing the water flow, results in higher entry pressure, more speed at the choke, creating more suction and a greater amount of air will be mixed with the water.

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Thank you Miquel, this is fantastic. I have wanted to play with this idea but haven't got to it- now I can just watch yours! I will be interested to see what effect you think the moisture has on the smelt, and what other advantages and disadvantages you find. I bet it sounds nice!

 

 

 

Some people say that air moisture is beneficial to the reduction process. I will go back o this later.

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Thank you every one for your comments.

 

 

Many times we dismissed the way the ancient foreman/crews run these furnaces. Like the way we ignored the importance of the square section of the pipe. We also did not believe that a copper tuyere would withstand heat better than one made of iron or stainless steel. We also thought that moisture would have a negative effect on the smelt...

Edited by miquel

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The next challenge is the copper tuyere.

 

One way to go about it would be to roll up copper plate of the correct thickness. But we were more interested in doing a molten copper pour even though we had no previous experience or knowledge about the process. Any excuse to learn something new and experiment with something interesting.

 

We first made the mold using iron pipes.

 

 

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Edited by miquel

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Fonen%20coure.png?psid=1

 

 

 

Miquel,

That is quite amazing! I cannot agree more with your statement " Any excuse to learn something new and experiment with something interesting". That path may be a little slower, but much more valuable.

 

Jan

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I just thought I'd add a quick comment about moisture and iron oxides. Ancient Greek potters used an oxidation/reduction/oxidation firing to get their black and red ware. The reducing atmosphere was produced by closing the flues and piling in green wood. The wood not only burned incompletely, but let vast quantities of moisture into the kiln which causes a reaction turning FeO to Fe3O4.

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Isn't that oxidation?

 

Yes, sorry. A terracotta pot has Fe2O3 in it, which is reduced to FeO. H2O reacts with the FeO (as well as CO with Fe2O3, I think), to produce the black Fe3O4.

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It was an epic fail. The copper became soldered to the pipes and we had no choice but to cut it in sections in order to reclaim the copper.

 

 

 

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Edited by miquel

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