Experimental waste oil burner, how to stop mild steel flaking?

[tttonyyy]

I've not posted here for a while. I'm currently experimenting with burning waste oil, without buying expensive components.

Compressor aside, the spray nozzle and fuel pump I'm using for this cost just the wrong side of a tenner - just a few 1/4 bsp stainless fittings, with the needle from an inkjet refill kit and the end of an air duster nozzle. The fuel pump is a washer jet gear pump from China with some tail-light bulbs in series with it to slow it down.

The flame tube was made by a friend of mine.

The fuel flow (in this case I think it was a mix of engine oil, diesel and veg oil) and air flow can be adjusted to change the burn but until I've finished the new, extended nozzle I'm assembling I can't stop it burning too far back in the tube (before the throat of the venturi):

Mark II will be run from a vending machine vane pump, which I hope will be able to cope with straight engine oil/waste glycerol from making biodiesel, which is too thick for the washer jet pump to cope with (it just slips the plastic gears on the shaft).

But the immediate issue I have is that the early burn can get the metal of the tube yellow hot, and the mild steel has started to flake.

Is there anything I can do to prevent this with a coating of some sort, or heating and brushing with powdered aluminium etc?

All good fun!

 

[chunkolini]

Interesting stuff and great photos.

 

[rtbcomp]

I'd be thinking in terms of using stainless steel - some washing machines have stainless outer drums which might yield suitable material. (Others have plastic outer drums, I don't think they'd be any good).

 

[tttonyyy]

Stainless would be the ultimate way to go, that's for sure.

There's also some videos of it here, with various fuel/air mixes:

https://www.youtube.com/playlist?list=PLC2kHvkqNbv6qK55q8ccoZrCZY-Or2Q4o

 

[normspanners]

Somebody on www made a rocket stove WOB, and had the same problems, he ended useing stainless but that eventually just turned to dust.
But I havnt been able to find the blog /forum again.
I was going to use refractory cement with stainless needles in the mix to cast one.

 

[tttonyyy]

Where are you buying your stainless needles? I'm having trouble finding 1.6mm/2.0mm OD stainless tubing in decent lengths - I've ordered these, but they've got a long way to travel: http://www.ebay.co.uk/itm/271909498165

 

[normspanners]

No the stainless needles are just that, very fine stainless (like fibre's ) to strengthen the mix.
as per concrete fibre mix

 

[tttonyyy]

Cripes. I'd be interested to hear how you get on with that.

 

[Fintray]

I don't think any type of coating is going to protect the tube from the heat. You have identified that the flame is burning too far back inside the tube whereas it should be "funnelled" by the tube but not actually impinge on it. Just thinking of the way a normal pressure jet burner works.

 

[wyn]

You could try a ceramic refractory coating..something like "ITC 213" for coating metal

I'm not too sure if it's available in the UK.

 

[waddycall]

Should there be so much flame inside the tube? Perhaps you have a flame speed/light back issue as it seems to be burning before the aeration hole in the venturi

 

[captain-destructo]

i have seen these made without a venturi just a straight pipe some with lots of holes in it along its length

 

[vbottles]

Have you made this from plans or made it up? How much compressed air are you running through this burner? If it's a reasonable amount why have any holes in the burner using the venturi effect? I would also fit a straight tube with another wider piece fitted on the end to be a flame holder.
Are you planning on running this in a forge/furnace? If you are you may not need a flame holder.
Andrew

 

[octo0072000]

you might want to have a look at Babinton waste oil burners

 

[tttonyyy]

We've played with Babingtons (and Turk burners), here's a slightly less sophisticated Babington built by a friend:

The Babington we found it quite hard to keep lit, depending on the fuel, and of course you have to scavenge the leftovers that dribble to the bottom somehow (gravity to tank or pumped). You'll note in the video above there's a constant arc maintained at the point the flame starts, which in my mind is cheating!

Actually it was my friend's commercial Delavan syphon nozzle imported from the US that inspired me to try building something similar at a lesser cost (Delaven nozzle and adapter to fit it cost the wrong side of £60 including VAT and postage).

In answer to the air question, it varies depending on the fuel. For the thin liquids (like diesel) it's definitely less than 1cfm, so it doesn't need a mighty compressor to run it - part of the reason for venturi with air ports - the idea is that the compressed air energy is used to blow the fuel into small droplets, and the rest of the air for the burn can then be introduced by venturi.

I always have glycerol to dispose of so using it for heat in some way (heating the outbuilding or house) appeals greatly.

 

[Gareth J]

Water cooled stainless? Be nice to get some of that heat into some water I'd imagine... Or would this cool combustion too much and leave you with a sludgy mess...?

 

[vbottles]

Thanks for explaining the holes for the venturi effect. There seems to be an issue of lack of air velocity to stop the flame front burning back into the burner. What size hole is the compressed air going through? As the venturi burners I've made are under 1mm and work fine to about 3psi.
Not sure if this helps as I don't know this style of burner. I have used a home built blown air oil burner to run a crucible furnace at about 1400 C. Very simple and hot.
Andrew

 

[Bladevane]

Picture a Bunsen burner which is a good example of premix combustion when the collar is open to admit air. You don't get the flame front even sitting on the Bunsen tip and a similar effect is what you should be aiming for.

 

[tttonyyy]

I'm genuinely not sure - there are too many variables!

If the fuel flow is increase the burn happens mostly outside the tube:

...but this seems to be a lot cooler. As I would like to burn glycerol/glycerine, getting a high temperature is a concern, in order to avoid generation of acrolein.

I've yet to see if my vane pump will pump glycerol directly*, and if the air flow is enough to break it into drops suitable for burning, so this might all be academic, though it is good fun



*I broke a circlip that holds the pump head end together and the one I purchased to replace it with is a smidgen too large to fit (should be 47mm, it's a touch larger)

 

[tttonyyy]

What size hole is the compressed air going through? As the venturi burners I've made are under 1mm and work fine to about 3psi.
Not sure if this helps as I don't know this style of burner. I have used a home built blown air oil burner to run a crucible furnace at about 1400 C. Very simple and hot.
Andrew

The cross sectional area for air is 1.4mm2 and 1.1mm2 for fuel. I'm increasing the fuel are in the second build for more viscous fuels. Pressure for delivered air again varies depending on the fuel type and the quantity delivered - I've been running it at around 20psi. It's pretty sedate below that, above that with lighter fuels it pulses like it wants to blow itself out.

Have you got pictures of your burner? I would be most interested to see them.