Oil furnace for cast iron. I need help

[MuellerNick]

Hi!

I do have a (waste) oil burner. It works perfect for CI (cast iron).
But I simply don't get that damned thing to melt CI. I once got the CI to melt, but it didn't reach pouring temperature, it flowed like honey on a cold day.

Now I have watched all YT videos back and forth, read all the internet in any language to find out what I am doing wrong. But I don't see it.
All I can conclude: Why can't *I* do it!?

The furnace is made out of a 200 l oil drum. Inside of it went 3 cm of refractory concrete (pre-mix I bought). On the outside I do have 3 cm of ceramic fiber isolation.

The air is blown in through a 60 mm tube. The tube is tangential to the inner of the furnace, just above the bottom of it. The blower is from a VW cabinet A/C. It is powered by a adjustable power supply (20 V, 20 A).

The "burner" is just a tube with 3 mm inner diameter. At the cold end, I blow in a bit of air to spray the oil. 1 cm more towards the hot end, oil is fed in by a throttle. I once had a jet at the hot end of the tube, but I removed it. It made no difference (at least, that was my impression).

So, if anybody has a similar setup and gets CI to pouring temperature, I'd **really** be glad if we could find the little trick I must have missed.


Thanks a lot in advance!
(desperate) Nick

PS:
I tried it once more today. With the result that the furnace was burning on the outside.

 

[aonemarine]

It's probably just a matter of the air fuel ratio. Try forcing more air in for starters. Pictures would be a great help to identify the problem. Is the furnace smoking when running?

 

[MuellerNick]

I'll make pictures, when the sun is shining again. It is night here right now. I'll also give more precise dimensions.

Re the smoke:
I can get whatever kind of smoke you want: Black or smoke of non-burning oil. Except the magic smoke that melts CI.
But I adjust it to be not smoking.
I have measured how much air I can blow through the furnace. It are 200 m^3 per hour. That about matches the 20 l / hour of oil that I can (but don't) burn.

I thought about an air-fluel ratio sensor. But the one I got was kaputt. The other one I got, together with the electronics didn't work with them.

So I try to match the A/F ration by eyeballing and open up the fuel 'til I get sooth and then reduce again. Also looking at the flame's color, it is just a very bright yellow. Doesn't matter that much how I adjust the mixture.

I have no pre-heating of the oil (it is fed by a pressurized tank) or the air.


Nick

 

[aonemarine]

Hang in there Nick, the first few times I tried to melt iron it just wouldn't. Then one day I got it figured out and now it comes easy.

 

[MuellerNick]

Then one day I got it figured out

And what was "it" that made the change? What do you watch for to make it work?


Nick

 

[metalmad]

Hi Nick
Im a total novice at casting, so take what I say with a grain of salt, but could it be your 200 litre drum is just too big for your burner?
I have not had a go at CI yet but my furnice is made out of a 20 liter drum.
would yours not be that much harder to get up to temp?
Pete

 

[aonemarine]

I was watching the color of the crucible on the inside of it to judge the temp. Cant really tell much from the flame, but the crucible told all. Once I hit the right spot the crucible went from red orange to yellow white...

 

[aonemarine]

Hi Nick
Im a total novice at casting, so take what I say with a grain of salt, but could it be your 200 litre drum is just too big for your burner?
I have not had a go at CI yet but my furnice is made out of a 20 liter drum.
would yours not be that much harder to get up to temp?
Pete

Hmmm, 200 L drum is 24" in dia, 3cm fiber and 3cm castable leaves a bore size of about 19 1/2".......thats pretty light on insulation (provided my math is right)

 

[aonemarine]

http://submarineboat.com/casting_furnaces.htm
This should help...

 

[MuellerNick]

OK, here are some pictures:

Left is the pressurized 40 l tank. Made out of a truck's compressed air tank and a few fittings welded on.
Right of it is the blower, then the fuel inlet and part of the furnace.


The blower.


The fuel "system". Left is an air inlet (throttled) that blows the oil (inlet is right of it) through the long tube.


The furnace.


Look inside of it. Inner diameter is 35 cm, almost 50 cm high. There is a riser where I put my crucible on. That riser is 10 cm high.
The red line points to the end of the tube of the fuel inlet.

I calculated the heat losses through the insulation. I don't remember the value, but is was quite low compared to the power output.
Edit: The liner is glowing orange, the crucible is at a bright yellow.


What might help me is your design of the "burner".
Do you pre-heat the oil?
Do you have a more sophisticated spraying of the fuel, or do you just relay on the oil evaporating when it hits the hot wall?

http://submarineboat.com/casting_furnaces.htm
This should help...

He has never cast iron with it.


Nick

 

[aonemarine]

Sounds like you are very very close to iron temps. I use a delavan nozzle and thin my waste oil with diesel. You should be able to burn waste oil unthined with your set up. Try more air, or take the easy way out and thin with diesel.

 

[jasonh]

Nick:

It's true that the svseeker/submarine boat guy mostly melts bronze, but the guy he got his burner design from melts iron. It's an oil/propane burner and it uses an atomizing nozzle normally intended for a heating furnace.

[ame]http://www.youtube.com/watch?v=P-A8uoWdBB8[/ame]

A siphon oil nozzle:
http://www.patriot-supply.com/products/showitem.cfm/DELAVAN_30609_7

With an adapter:
http://www.patriot-supply.com/products/showitem.cfm/DELAVAN_17147

Jason H.

 

[MuellerNick]

I use a delavan nozzle

So I need one too!
Not available here.

So could you please give me the dimensions. I found pictures of them already.
There is a central jet with a straight bore where the oil exits. What's the bore please?
Then, around that is a conical jet with some whirling-groves for the air.
What pressure do you have for the air?
What pressure does the oil have?

That would be of great help!

TIA,
Nick

 

[aonemarine]

Nick, I will get you dimensions tomorrow if I can, if not then in the next day or so. There is another option as well, go to the steam automobile club of America forum and do a key word search for "atomizing burner" and you will find some drawings posted by Rolly for an excellent burner. Make sure you set search options for all time, as it was a post from over a year ago. The thread is still there, I just checked, but I'm at work now and have no way to attach the link.

 

[aonemarine]

As for my oil pressure, its just gravity fed. I have no idea on the air, but it isn't much. I adjust the burner for the best flame I can get, then turn on the blower and adjust the blower speed for best temperature. Not real scientific, but the burner makes a certain sound when its just right while the blower is off.

 

[MuellerNick]

Nick, I will get you dimensions tomorrow if I can,

I can wait 'till next year (20 minutes to go).
I'll search for the burner in the forum you suggested. Thanks for the hint, that sounds promising!
So, the pressures don't seem to be high or too critical. Sounds like DIY leads to (finally) success.

All that sounds really good, thanks for your help!
I see how far I come tomorrow. Casting CI this week would be a great start for the year to come.

Nick

 

[robcas631]

Interesting please keep me informed.

 

[robcas631]

Nick,

Happy New Year!

Rob

 

[aonemarine]

http://steamautomobile.com/phorum5214/read.php?1,18912,page=1
heres the link...

 

[MuellerNick]

Found this cross-sectional drawing of the said Delavan type SNA nozzle:



aonemarine, could you please give me the diameters at 1 and 2? Also, what is the throughput of fuel (per hour) with your nozzle, or what type is it so I can look up the throughput.

Thanks a lot!
Nick