Cupola furnace ?

Discussion in 'Furnaces and their construction' started by DavidF, Mar 20, 2019.

  1. DavidF

    DavidF Administrator Staff Member Banner Member

    They have it for .80 cents a pound. But it sounds like the pieces might be too small??
    I dunno, I'm still researching. Cant anything be simple?
     
  2. OMM

    OMM Silver

    Just build it!

    $.80 a pound (or a $1.20 pound) is really nothing, in the big scale things. The thing is, you don’t get Coke for free (unless you know and willing to work with somebody crooked). One of my cast-iron foundries uses Coke. They will sell it for $1.10 a pound CAD.

    Show us the pieces you got, and the pieces you may need, (And maybe some of us have the extra pieces that you need). We are a society that might have leftovers.

    Sometimes drawings and scaled down prototypes can be helpful when incountering a new endeavour.
     
    Last edited: Oct 27, 2019
  3. DavidF

    DavidF Administrator Staff Member Banner Member

    I have been told by a couple of people now not to go under a 14" bore as they can be finicky to operate any smaller. I have 2 tanks laying around that I can use. One is 18" which would give me a 12" bore and the other is a 25" tank that would give me a 19" bore. the 19" bore would take 23 bags of refractory with an estimated cost of $1,610.00 and the "12 bore would take 14 bags of refractory with an cost of $980.00
    It would be nice to build two different sizes to save on fuel if doing smaller melts but I figure whoever comes to help pour is going to want to cast couple of parts as well.
    I just keep bouncing back to the availability to obtain the coke. Hopefully I will all ways be able to find a supply but just in case im looking into other options. One would be coking my own fuel. It looks like I would be able to do this in my kiln by heating up the coal to 1000C but I worry about the smell. The other is to use anthracite, but I would need to make up some sort of a heat exchanger to pre heat the blast air to get it to burn, but might not be feasible for such a small furnace. Third option would be a fuel blend, using 75% anthracite and 25% charcoal. I have no idea how this would work out......
    Of my 3 options, I think i should have a go at coking my own fuel before I go too far down the rabbit hole... or perhaps an experiment with the charcoal and anthracite....
     
    Tobho Mott likes this.
  4. So what sources of coking coal are there: iron foundries, steel mills, gasworks, steam railway enthusiasts and coal fired power stations. Possibly a steam railway group could use a casting or two, the first thing that gets stolen off a locomotive are the large cast brass manufacturer's plate, they get traded for big bucks amongst collectors. The only coking coal I have is 1977 vintage peanut coking coal from a power station.
     
  5. DavidF

    DavidF Administrator Staff Member Banner Member

    Getting coal is not a problem, getting coke just keeps getting more difficult from what I've heard so far. Right now I can get coke. But what about a year from now? If my local foundry supplier goes out of business, then what? It's the only place locally that I know of where I can get small quantities of coke.
    I picked up about 3 lbs of coal out of the dredge pile where I work today. Going to try and coke it in my kiln next week to see how things go..
    It ain't rocket science unless it blows up. ;)
     
  6. It looks like the main issue is going to be the smoke generated as the coal roasts. Here's an except from Wikipedia's beehive oven page:

    "Although they made a top-quality fuel, beehive ovens poisoned the surrounding landscape. After 1900, the serious environmental damage of beehive coking attracted national notice, even though the damage had plagued the district for decades. "The smoke and gas from some ovens destroy all vegetation around the small mining communities," noted W. J. Lauck of the U.S. Immigration Commission in 1911. Passing through the region on train, University of Wisconsin president Charles van Hise saw "long rows of beehive ovens from which flame is bursting and dense clouds of smoke issuing, making the sky dark. By night the scene is rendered indescribably vivid by these numerous burning pits. The beehive ovens make the entire region of coke manufacture one of dulled sky, cheerless and unhealthful".

    In China, beehive ovens were not banned until 1996, and this ban was not fully effective until 2011."
     
  7. joe yard

    joe yard Silver

    Unfortunately I have never had the chance to get up close and personal with a copola.
    Back before I retired I was lucky in that I was in a job that consisted of industrial weighing and weight control. My job was primarily in the ranges of 2 to 20,000 Lb. This put me in several of the foundries with inductive furnaces ranging from 500 to 10,000 Lb. Believe it or not most of the inductive furnaces set on a scale. There is a little spot under them when they are in the up position to work on them. It can only be described as hell’s closet. Two of these foundries still used cupolas. One was the Acron Indiana Foundry 41° 2'5.42"N, 86° 1'19.85"W. They had a small copula that they made 1 melt a day and relined it after every use. It was expensive and work intensive. They also had 1 500 lb inductive furnace. The other foundry was the Bremen castings Bremen Indiana 41°27'5.54"N 86°10'8.12"W. This foundry used a large copula that was fed with a front end loader. I have no idea how often this one was relined. When you look on google Earth now the Bremen foundry does not have the large coke pile and there is signs of roof work where the copula was. At the time of my departure 5 years ago. This foundry was running 3- 4000Lb inductive furnaces along with the copula,
    They are phasing out the copulas fast. There are many advantages to electric melts. This will make the search for coke ever more difficult.
    Joe
     
  8. DavidF

    DavidF Administrator Staff Member Banner Member

    I dont expect it to be too bad. Just doing small quantities at a time ( at night).
    But if it is overly pungent, I'll set up a scrubber and make some sulfuric acid while I'm at it. :D
     
  9. Rocketman

    Rocketman Silver Banner Member

    Lining a cupola is an art form as well.
    The 60" bore cupola we had at the foundry I worked was an interesting beast.
    It was lined with a rammable hardface (supposed to be replaced yearly) and then had a sacrificial lining of "alabama mud" gunned in before every pour. The alabama mud was some native mix of clay from a riverbank in Alabama, hah. I don't recall the specifics of the stuff. The glazed area in the melt zone would be chipped out in the poor sections after each pour and re gunned. I did participate in a gunning one night though where I had to stand back to back with a guy on a plank inside the bore, holding a big halogen light over top my head backwards, so the gunning guy could see what he was doing. Wearing a big rubber parka. Couldn't hear shit while the gun was running and had to hobble to match his movements. 0/10, would not recommend.

    The sacrificial lining melts throughout the pour and contributes to the slag.
    There is some weird chemistry that happens with the lining at elevated temps, and determines what kind of flux you need to create your slag. I don't recall exactly but it was acid vs. base flux. If you used the wrong kind it will eat the cupola. (The most common flux source for cupolas is Limestone)
    Given the cost of castable refractory I think the common method is to use firebrick nearest your stack, buried in castable or rammable refractory, and then lined with your sacrificial lining on top.

    The floor of the cupola apparently is also an art form - it was formed out of plain greensand and had to have a specific slope.
    The doors would be shut and a bucket of greensand dumped in, and then two guys lowered down the bore from the top to form the floor. I believe the hand-picked pieces of bed coke were also placed by hand, at least the initial layer on top of the floor. (they are a different size from your charge coke)
    The doors that made the bottom of the cupola were vented with holes, that permitted carbon monoxide gas to diffuse through the floor. It would be touched off to prevent buildup and flames would lick across it during the melt. I am not sure how important this would be on a small cupola.

    Dropping the bottom of the Cupola at the end of the pour was a sight to behold. (but also you couldn't look at it too long)

    Regarding Anthracite: Coke is the preferred fuel not only because of its purity, but also its mechanical properties. In the book The Cupola Furnace: A Practical Treatise on the Construction and Management of Foundry Cupolas ( I read some years ago) the author described using anthracite, and it tended to fracture while burning and block airflow as fines developed creating excessive backpressure. The coke holds its shape and does not obstruct airflow.

    I have a copy of Steve Chastain's cupola book here somewhere, I will have to locate it and give it another read. I believe I had settled on a 10" bore cupola when I had the drive to build one, as that provided a significant tap size and melt rate, much larger and the manpower needed to manage such a pour became excessive, as did a place to put such a quantity of iron.
     
  10. Al2O3

    Al2O3 Administrator Staff Member Banner Member

  11. Found a video about lost foam casting a six cylinder engine at the 1:48 mark, it looks like a wet sleeve design so probably a diesel engine of some description.

     
  12. _Jason

    _Jason Silver

    Mr Pete recently filmed a local high school class's attempt at a cupola. Perhaps there's a couple take-aways here for the good of the group?

     
  13. DavidF

    DavidF Administrator Staff Member Banner Member

    Thats a good video even though they did not get to a point where they could pour the iron. Funny thing is i was sitting here arm chair casting saying "your overloading it" and sure enough..... Probably because I had read about that in the 537 page book posted earlier.... Think they may have been a bit shy on the combustion air as well.... I wonder what is the cost of the fruity pebbles they melted, would be nice to not have to acquire and bust up scraps. The other thing I noticed is that the slag hole is very close to the same height as the tap hole...
    Im on vacation starting tomorrow. Going to clean up the shops, organize, and build some shelves and with any luck ill start putting the cut wheel to steel next week. But I still haven't decided if im going to build a 12" bore or the 19" bore cupola.
     
  14. Tony

    Tony Copper

    I work for the biggest grey iron foundry in the country, I can assure you we are not phasing out cupolas any time soon. Electric melt is not nearly as profitable. In fact our newest plants all run huge cupolas. Coke is out there and available, the problem is getting it in small batches. We order it by the train car load. We actually sift out all the small pieces that you would probably want for a hobby cupola and sell them. I'll try to find out where they get sold to.
     
    dennis and DavidF like this.
  15. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    Cool Tony, would that be Waupaca?

    Best,
    Kelly
     
  16. Tony

    Tony Copper

    Yes
     
  17. Ironsides

    Ironsides Silver

    I had a look at mrpete video. They are wasting their time trying to reduce iron ore in such a small furnace. They would be better of melting scrap iron to get liquid iron to fill their molds.
     
    _Jason likes this.

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