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Flux Recipe Formulation Help (6 replies and 7 comments)
If you are reducing the arsenic and then putting the ore back in an oxidizing circuit, you may be oxidizing the arsenic also, so I am wondering about your two stage process. None the less, a couple of suggestions: You can try scorifying the matte in scorifying ceramic dish after wrapping the matte in a lead sheet so that there is extra lead present and after it is complete (the litharge eye closes in the center of the dish), you can then try fire assaying the residual button with a standard flux. Alternatively, you might try adding an iron nail (a large nail for a standard fire assay charge of 1 Assay ton) with some niter in your flux and a little flurospar to increase the fluidity.
Thanks for the reply. I'm not attempting an assay, but rather trying to formulate a flux recipe for smelting the calcine to produce dore.The two stage roasting was recommended for high arsnic ores in a document that I read on this website. I'll try to locate a link.
Are you using Pb as a collector metal?
Or adding enough Flour and KnO3 to reduce the litharge to metallic lead? I'm working on a similar Arsenopyrite, Chalcopyrite, Quartzite Galena Ore. I'm getting no matte layer with this recipe.
1000g ore sample unwashed/unwashed
So no added Silica.
1000g Soda Ash
1000g Borax
20g Anti-Borax as needed to thin slag layer before pouring.
150g Pb as collector
I'm going to try this next
Because I'm loosing around 11g of Pb each 1.1kg charge in a #6 crucible using the same prille in each of 3 total runs.
1Kg ore washed & Roasted
1kg Soda Ash
500g Borax
150g litharge
30g flour
30g KnO3
Anti-Borax as slag thinner. This should give me a 147g prill and a clean separation.
I am having similar problem arsenic and sulfur. I tried all kinds of flux combo's, roasted 5 hr then roasted 12 hr, lead in the smelt and nothing. The assay's say a gram per pound of cons. I tried acids. Everything comes down to the same, arsenic and sulfur. Any sure way of removing them first? Thanks
My base recipe was:
40% fused borax, 25% potassium nitrate, 20% soda ash, 15% silica.
I chose this as a starting point because it has been successful with other local sulfide ore that I've smelted. I tried other formulations, including variations of the above as well as the classic Chapman's Flux.
I am in the Bradshaw mountains of Arizona. I am having similar issues with unoxidized pyrite showing up in the smelts.
Are you roasting your ore prior to smelting? If you're still seeing non oxidized pyrite after roasting than you didn't get enough air in your roast. This is common when the ore is not crushed finely enough or left stationary during the roasting process. If you're not roasting your sulfide ore before smelting than you will have a lot of problems. Small amounts of unoxidized sulfide can be managed by adding an oxidizer such as potassium nitrate to your flux formula.
Yes. I am roasting. I noticed that if I use a spatula to lift the ore up into the air when it's flowing red hot and drop it that it Sparks and appears to be oxidizing. I run it through a hammer Mill first. I am pretty sure I'm not getting it ground fine enough and I am thinking of trying something like a flash roaster, fashioned similar to a flash smelter.. I looked at it under a microscope after roasting and I can still see bright dimensional pyrite, so I am pretty sure I'm not grinding it enough before the roast.
I screen mine to -100# before roasting, I've had success using a cast iron skillet over an open fire. I stir frequently for about 2 hours and then let it sit on the coals overnight. Using this method I've oxidized 95%-98% of the sulfide, I account for the remaining percentage by adding oxidizer to my flux charge.
Have you refined your recipe? I am back to the drawing board. I have several varying pyrite ore samples all containing different forms of pyrite, and heavy sulfide content.
I started as basic as I hoped to get away with, and have continued to try and thin the charge for a better pour.
how much sulfur and arsenic are we talking about here? Percentages?
Hello, I am an artisnal miner in northern Arizona and am having trouble fluxing a sulfide ore. The ore is composed mainly of arsenopyrite, pyrite, galena, and polybasite. There is minor barite present as well. The ore was crushed to 150 micron and calcined using a two stage process, 90 minutes at 900F in a reducing atmosphere (to reduce arsnic), and again for 4 hours at 900f in an oxidizing atmosphere to drive off sulfur. The calcine was prepared in 100g samples for flux testing. I have attempted several flux formulations with varying composition of silica, borax, soda ash and potassium nitrate, all of which have produced a matte button. Attempts to further smelt the matte have been unsuccessful. In my latest test I tried adding litharge to a high nitrate, low silica flux and managed to still make matte. Any help would be appreciated, I have a background in physics but chemistry is still new to me. Thanks!