Smelting and propane efficiency ?

[mac1911]

So over the years I have been getting better at increasing my smelt to fuel ratio.
When I set up a nice wind block pick warmer days and have everything ready I get right around 500lbs lead for a 15lb blue rhino tank.
Some times I do a little better but I feel like 30lbs of smelt to 1lb of fuel seems to be a good starting point.

I scored a used tank last week with 6lbs of fuel left in it. Previous owner said local spot would not fill it because it was a blue rhino tank. took it home and weighed it. 24lbs with a tar weight of 18lbs---smelted down 75lbs of range scrap and flashing used 1.8lbs fuel.

Definitely loose some efficiency when you get low on fuel the burner does not have the same umph. I will run the free tank to empty and go exchange it right now local exchange for blue rhino is 14.98

[Cosmic_Charlie]

I think my yield is similar to yours. Smelting has not become a chore and is still enjoyable for me so I don't worry much about propane cost. I should be looking for more scrap about now too.

[kevin c]

I get 250# X 4 melts out of a 20# tank (~15# propane?). That's using a covered pot with a fiberglass insulating jacket and a windbreak around the stand, and includes the propane using a weed burner on top to speed melting. It also helps that my scrap is not mined out of a berm anymore; it seems to take a lot more heat to melt mined bullets because of the insulating qualities of the jackets and dirt.

[Idz]

useful info if you want to calculate efficiency:
propane (C3H8) = 21514 btu/lb
Pb Cp=0.03 btu/(lb*F), latent heat=9.65 btu/lb, melt T=621 F
Cu Cp=0.09 btu/(lb*F)
steel pot = 17 lbs, Cp= 0.12 btu/(lb*F)

a typical melt example for me:
scrap wt=23 lbs assume mostly copper, Pb=75.25 lbs lead ingot yield, measured smelt temp = 650F, starting temp = 50F,
1.5 lb of propane burned

Pb heating = 0.03(650-50)75.25= 1355 btu
Pb melting = 9.65(75.25) = 726 btu
Cu heating = 0.09(650-50)23 = 1242 btu
pot heating= 0.12(650-50)17 = 1224 btu

Total = 4547 btu

C3H8 1.5 lbx21514 btu/lb=32270btu
efficiency = 4547/32270= 14%

[Conditor22]

The trick is limiting heat loss and directing ALL the heat to where you need it.

A coffee can shield cut to fit around the burner and direct the heat to the bottom of your smelting pot will decrease the required heat.

My propane smelting pot has a ring going down to the burner grate and areas bent out around the side for flame/heat to go up the outside of the tank


Using a lid also helps contain the heat in the pot (and limit smoke and smell)

[jsizemore]

My local propane outfit charges me $14 to put 20lbs in my tank. I melt 1600lbs with a full tank. The flames never get beyond the edge of my 10 qt. dutch oven. Takes 40 minutes from load WW's to pouring ingots. I use an old sheet metal jacket from a hot water heater for a wind shield and the top sheet metal for a lid

[Cosmic_Charlie]

The trick is limiting heat loss and directing ALL the heat to where you need it.

A coffee can shield cut to fit around the burner and direct the heat to the bottom of your smelting pot will decrease the required heat.

My propane smelting pot has a ring going down to the burner grate and areas bent out around the side for flame/heat to go up the outside of the tank


Using a lid also helps contain the heat in the pot (and limit smoke and smell)

Nice set up there.

[kevin c]

jsizemore and conditor22 both may be onto something as far as how to use the BTU’s effectively. Before I insulated and shielded my double jet burner, I’d crank it all the way up (200,000+ BTU’s) and barely melt anything. All that energy just went to heat up the air above the pot.

Trapping the heat below and around the pot by having the flame at the right distance below the pot, having a skirt and jacket to channel and hold heat seem to let me turn the heat down significantly. I do turn it up, though, if I’m impatient.

[mac1911]

I get 250# X 4 melts out of a 20# tank (~15# propane?). That's using a covered pot with a fiberglass insulating jacket and a windbreak around the stand, and includes the propane using a weed burner on top to speed melting. It also helps that my scrap is not mined out of a berm anymore; it seems to take a lot more heat to melt mined bullets because of the insulating qualities of the jackets and dirt.

so 1000lbs , nice. I have a wind break but its not insulated. I do need to do something with my "lp tank smelting pot" I do feel like the heat whips up and around the curve of the tank.

[mac1911]

My local propane outfit charges me $14 to put 20lbs in my tank. I melt 1600lbs with a full tank. The flames never get beyond the edge of my 10 qt. dutch oven. Takes 40 minutes from load WW's to pouring ingots. I use an old sheet metal jacket from a hot water heater for a wind shield and the top sheet metal for a lid

nice, local fill places here are $19-21 and if you dont know any better they are dumping 15lbs in them and calling it full. They also charge you the same price even if your tank is not empty.

they do not list any min or max amounts they charge a fee to fill your tank. A few places give the same reason why Rhino tanks only fill to 15lbs.

[2ridgebacks]

As has been pointed out, retaining the heat s important. I do that with a fabricated pot with 3/8 walls and a 1/2 bottom. Then, I firebrick from the ground to the top of the pit, capping with steel plate. This encapsulates the burner and pot. After the first batch, I can melt 700lbs in around 20 minutes if memory serves me correct. That’s running a 250k burn at a fast idle.

[2ridgebacks]

Sorry for the sideways pic. 14lb ingots for reference.

[mtgrs737]

I had my propane buddies make me up a hose fill kit to do regular tanks and my forklift tanks from my 500 gallon home bulk tank. My last fill was 99 cents a gallon and I don't have to drive my tank to a fill station and pay them their price. I have a 100 lb. tank that I run off of and keep the 20 lb. tanks for the BBQ.

[ioon44]

I get well over 1000 lbs from a 20 lb propane tank, I have wind shields and inner liner with top covers for pot and outer shields.

[mac1911]

where do you get the firebrick. I cant find anything local other than the thin bricks for lining wood stoves and it would cost a small fortune building any type of fire brick walls

Im starting to think my burner is not "big" enough in BTUs? IIRC mine is 150,000? Where does one get a 250,000 BTU burner. I do have a 20 psi regulator, should I go with 30 psi adjustable ?

[shaune509]

Any brick yard will have standard fire brick, it is the refractory brick that is harder to locate in some locals. For what we are trying to do by holding in heat and reducing wind at the pot regular fire brick will work better as they are more weather resistant and the mass retains heat were refractory bricks insulate and are softer so more apt to absorb water and suffer breakage. Standard fire bricks are $, cut stove bricks are $$, refractory bricks are $$$$.
Shaune509

[2ridgebacks]

It must be standard fire brick, because the best I remember it was under two dollars each. It came from a local Brickyard.

[bobthenailer]

Using propane turkey fryer with a cast iron dutch oven with a lid and a SS heat wall around oven to keep heat in , made from a thin SS pot with the bottom cut out. you can get well over 1000lbs smelted with 1 propane tank

[mac1911]

useful info if you want to calculate efficiency:
propane (C3H8) = 21514 btu/lb
Pb Cp=0.03 btu/(lb*F), latent heat=9.65 btu/lb, melt T=621 F
Cu Cp=0.09 btu/(lb*F)
steel pot = 17 lbs, Cp= 0.12 btu/(lb*F)

a typical melt example for me:
scrap wt=23 lbs assume mostly copper, Pb=75.25 lbs lead ingot yield, measured smelt temp = 650F, starting temp = 50F,
1.5 lb of propane burned

Pb heating = 0.03(650-50)75.25= 1355 btu
Pb melting = 9.65(75.25) = 726 btu
Cu heating = 0.09(650-50)23 = 1242 btu
pot heating= 0.12(650-50)17 = 1224 btu

Total = 4547 btu

C3H8 1.5 lbx21514 btu/lb=32270btu
efficiency = 4547/32270= 14%



I wish I knew what all of this meant.... seeing 14% seems that LP tank smelting is not the most efficient but probably the cheapest over all.
No idea what a really nice smelter would go for LP or electric that would really increase anything in the end. I do know just by using a wind block My melt time decreases a good amount.

[Atonic]

If you are concerned about efficiency then stop using blue rhino etc. Find someplace that charges you for the amount filled. Tractor supply is my goto.