4metals said:
Kevin,
Thank you for posting this thread, it is interesting.
Concerning the pots of lead oxide poured off from the stationary furnace that are added back into the rotary furnace, is that remelting performed as part of your job with you getting credit for the values recovered? I hope so because I will bet they are holding values! While skimming the surface it is impossible not to skim a little molten lead. That lead has your values in the alloy.
Another secondary point is that burning off of the lead is a rather toxic way to go. Cupellation with a bone ash hearth will still result in 10% of the lead volatilized but 90% is absorbed into the bone ash so you don't have to breathe it.
What you are doing is oxidizing lead metal into lead oxide and removing the lead oxide, along with the other base metal oxides, from a floating surface slag. Essentially the exact opposite of a litharge assay fusion.
Thank you sir.
The lead which is used as the main collector metals and its final poured off lead oxide belong to my partner. So I dont get paid or anything for that.
As for the values being in those lead oxide, I have tested this myself twice, gathered all the lead oxides which we have accumlated using my stationary furnace, and melt them in our own furnace and result was absolutley 0g of values.
I also remelt the slags from my previous operations, and from over 500 kg of slags which was smelted using rotary furnace, we only recovered 2.2g of gold at the end. This was from many different batches, which tells me still a good recovery rate and minimal losses.
But I will do what Barren mention to just break a few slags and pan it.
Also skimming is where these operators got skills, This is a simple test they do to make sure the lead is not coming off with the skimmed oxides, as they tilt the furnace, they collect a small sample on the metallic part of a shovel, if it is lead oxide mixed with base metals, once cooled, that stuff on metallic part of shovel will just fall as one piece, but it contains silver or value it will stick to shovel.
They claim once the silver is added, it will collect all the PMs in the molten lead.
As for fumes, we use the following filter and scrubbing system,
It contains cooling section, bag house and cyclone, all the lead fumes are collected by bags in the bag house. These recovered lead can make up to 6% of the lead used up in operation. Also recovered once a year.
So it is very enviromentally friendly operation, and local EPA approved.
Regards
Kj