Hybrid Oil/Propane Burner

[Jammer]

Do you ever have problems with the propane flashing back into the tube? Mine did this and I didn't realize it, it burnt up the O-ring in the nozzle.

[Harry]

Might be one benefit of running the propane through the nozzle with the compressed air if this causes any problems since all the fuel would be forward of the nozzle. I would kind of think though that with plenty of blower air pushing it along and the style of spin vane David is using it would be tough for the propane to ignite upstream of the nozzle but certainly something to watch for.

With my setup the propane goes in with the compressed air and comes out the tip of the nozzle downstream of the spin vane, upstream of it there is nothing but blower air so no worries there.

[dallen]

Do you ever have problems with the propane flashing back into the tube? Mine did this and I didn't realize it, it burnt up the O-ring in the nozzle.

Haven't yet, mines gonna be kinda hard to flash back that far, (i say this and it will make a lier out of me) I have to have the blower running for mine to even burn the propane the way I have the thing put together. its sort of like Nudges but mine is in so much smaller of a tube. and with that spin vane in the very end of the tube it is pretty much blocked off unless the blower is running. no way for a flame to sustain its self in the tube.

[Harry]

After a couple of weeks now of running the hybrid burner I have to say I am loving it more and more. I added two gauges and a valve to the propane so I have tank side and burner side pressure and can tune the propane by keeping the burner side above PSI of the air and use the valve to meter propane to the burner.

Best guess at this point is I am running 2 or 3 PSI of propane (12 PSI on compressed air and 15 PSI working pressure with the propane added). This really brings the furnace alive, running oil at 1300* can be tricky to keep everything clean because it really wants to run hotter but the tiny amount of propane gives it that kick to keep it clean at the low range. My feeling is that it will also be very helpful in pushing the higher temperatures too. You guys know I am a fanatic about control of the furnace and could give two hoots about blowing flames out the top but if I can dial in 2350* and hold it there all day I would be ecstatic but of course aluminum temps is where my money is so I have to be mindful of that. Seeing where this is going though it look extremely promising in that the best of both worlds is just around the corner and a super clean burn is a welcome side benefit.

I also added a tank to the little Thomas compressor. With a 250 gallon tank and a pressure switch it will run from 14 PSI to 28 PSI, the compressor runs 4 or 5 minutes every half hour to keep up with the nozzle set at 10 PSI air. I had to dial the pressure switch way down because I have no unloader and above 15 PSI it doesnt want to start. I have ordered a pressure switch with an unloader so I am hoping I can pump it up to a 30/50 range for in and out and I also have some better valves and check valves coming.

When I get it all together I will post some pictures of the new setup. Been adding a few other things to the foundry in terms of closing in the furnace area and adding more ventilation which I will also be posting on too.

[Jammer]

Sounds great Harry, I'll keep this all in mind if we ever get moved. I feel like I can't do anything right now because I have to keep everything boxed up.

[Harry]

Made some changes to the burner setup. I added high and low side gauges on the propane line with a nice needle valve between them and ball valve after to shut the propane off easily and isolate the low pressure gauges for times when I want to run higher air pressure.

This allows me to run the regulator from the tank at a pressure higher than the compressed air pressure to overcome back pressure. The needle valve is so I can limit the flow to a very small amount of propane. I have found 2 psi on the low side and 15 psi on the high side works pretty good and since I rarely go above 10 PSI with the compressed air the propane always has enough pressure behind it to continue flowing.

The air controls, gauge at the top shows tank pressure and the gauge at the bottom shows pressure coming out of the regulator. Black hose on the left goes to a 250 gallon tank, the blue hose on the right to the compressor. The red hose is connected to a pressure switch with unloader set at about 40/55 PSI. The little compressor has been cycling about 10 minutes each hour.

The propane bottle is a bleeder tank and on the compressor side of the check valve, when the switch opens and shuts off the compressor the propane tank bleeds off. I am going to set this up as a low point drain on the tank so each time the compressor cycles it will blow off moisture from the main tank provided I can get the water to flow through the check valve while air is going the other direction. Thinking if I place the check valve vertically water should be able to pass down while air is going up.

I had this 4" pipe with a 3" pipe coming out at a 90* angle from it and the bottom capped off from some old burner stuff I was playing with when I was first getting started. Cut a hole in the back to pass the siphon burner through and sit the little bilge blower on the top and it was ready to go. Sorry about the blurry picture but it gets the idea across.

And a new air spinner, this works better than anything I have tried to date. It is the air spinner from a home heating burner and I just cut it out of the ring it was in and it fits perfect in the 3" tuyere on my furnaces. I tacked a washer onto the back of it and a 1/2" cut down pipe coupling to that. Before welding the coupling on I used it to make threads on the siphon nozzle, could have used a 1/2" pipe die but I would have had to hunt for that and this worked fine, a little cutting fluid and a few trips on and off and the brass nozzle had some pretty nice threads on it.

And another shot of the air spinner. I run it on until the tip of the Hago nozzle is just past the washer. The conical shape of this and the layout of the slots for air really focuses the flame. I will try and get some pictures of this because it is purdy. Now instead of a huge flame the size of the tuyere the rapidly expands I have a flame that comes out about 1 1/2" diameter that comes to point and never touches the walls of the tuyere

And heres a video of the furnace running and a little panning around to show the various parts. I still need to route wiring and hoses and mount the controls off my shelf, just put everything together there as I was seeing what works.



At just before a minute and half into the video you will hear the flame sputtering then smooth back out. I turned off the propane out of view of the camera then turned it back on. This seems like it is going to work out great for dialing back to pour then just by opening the valve going right back to where it was.

I weighed the propane tank and use in three hours of running was right at 1 1/2 lbs so 1/2 lb per hour.

[Nudge]

That is rather interesting with the lpg. I dont seem to have the problem with my furnace sputtering is it because you have the oil turned down too low?

[Harry]

I had thought for quite awhile about adding propane to the mix, it occurred to me after noticing that the furnace just runs better while the plumbers torch is in there during lighting. David put his together and I thought I better get on the ball to keep up with the Jones Will have to see if I get to be first adding oxygen, that is next on my list. I think the oxygen will be nice for speeding up the end of iron melts pushing that last few hundred degrees that sometimes want to be allusive.

David took a different route adding the propane to the blower air stream while I added it to the compressed air, this took a little more in terms of hardware because I have to be able to keep the pressure higher on the tank regulator than the compressed air then regulate flow with the needle valve to overcome the back pressure and inject the propane into the air line.

The sputtering I believe is due to the siphon nozzle starving itself, kind of sucking the reserve in the nozzle out then waiting for more. I run my oil flow very low once the furnace is hot because it just doesnt take much to hold a target of ~1300* for aluminum. With the propane going it smooths it out. I dont have any problem with this using just air and oil either but it is a different mix ratio and all I am cutting off is the propane.

As I mentioned before I really like this addition. The extra flexibility in tuning the furnace and the cleaner burn are both welcome enhancements.

[dallen]

sounds like you hit on something you really like Harry, you will have to excuse me but the weather's been so screwed up here that I haven't even taken the time to modify a spacer ring that I need to shorten up for my next try with my oil burner or get the Thomas compressor mounter on a two wheeler although I did look at a Hand Truck at Northern Tools yesterday.

Who knows maybe this front thats coming thru now will blow out and I'll get a couple of days of decent weather because I also have a modified flask pattern that I need to pour to see if it will work so that I can cast a larger handle/alignment pin mount flask side with a retainment bar on the inside, the flask pattern I could probably do with the weather but when its raining or the winds blowing 40 MPH is just isn't much fun casting.

David.

[Harry]

Yup, I do like this setup a lot but then I have been very happy with the way the siphon nozzle has worked from the beginning. It just keeps getting better. I can hardly believe how well this thing is running now. It is kind of like when I first made a batch of home brew petrobond, it was so far and above anything I had used prior I was stoked but then I got the sand I use now and was blown away with the difference.

I have been quite impressed with the Thomas pump. If it holds up anywhere near what I am expecting in terms of life it will just end up being one of those since sliced bread deals. At 400W to run it and cycling 10 minutes or less with the big tank it is just about free to run. I picked up a bunch of 3/4" pvc today and will be running air lines around the shop soon. Getting power in was great in reducing the number of cords laying and hanging around now I will be getting rid of the hoses I have laying everywhere.

The so very little amount of propane (1/2 lb an hr) is also well worth the small extra cost for the big difference it makes in the way the furnace runs.

The next thing I am going to work on will be the air spinner. Going to work on focusing the flame more in trying to make the flame hotter faster if that makes sense. The goal is to get complete combustion of all the fuel in a nice tight flame. Going to try something very similar to the air spinner I have now but a deeper conical shape with the slits for the air running further along it. Keep thinking also about a refractory flare that would glow red hot around the start of the flame front which I think would further push the liquid fuel to vaporizing quickly.