The benefit of pyrometallurgy before a copper cell is the low quantities of chemicals used versus through put. What you seem to be working towards will generate a lot of waste liquors if you scale it up.
As not always easy and straightforward, apparent push was always towards pyro due to reduction of volume, that is for sure. As an old saying, look what big guys are doing, and it is probably the state of the art and most economic way currently developed
I definitely won't rely on a respirator alone, just as protection from some of the less nasty stuff during recovery (and with excellent ventilation) and supplemental protection on the refining side.
I've already researched the process I plan to use for recovery, it's sound. I'll be using a sodium hydroxide plus slowly added H2O2, while monitoring the Redox potential. Yes, this is a piranha solution and eats flesh very quickly. I know of a plumber who removed a P-trap after someone was kind enough to use 3 bottles of drain opener on a clogged sink, the kind that's hydroxide plus bleach. It immediately removed all the flesh down to the bone. I'll be adding the H2O2 slowly, and after base metal recovery I'll deactivate it with some Manganese oxide which rapidly catalyses H2O2 to water and oxygen (else on drying you can have sodium peroxide, very nasty stuff). Yes, everything involved in any extractive metallurgy is hazardous. I don't want to use the pyro technique as it's terribly polluting, produces carcinogens, and it's hard to clean up the gasses generated. I am aware that people use fire for this often and on a very large scale it is practical.
Scale wise I'm not going too big, and I will test before I build equipment to verify. Random ideas get expensive very quickly. Fortunately I'm fairly good at doing library and internet research which eliminates many ideas quickly. Still, I will test all reactions in a small beaker first. I will have a pH and Redox probe and will test samples often, especially at first
I quite cannot relate to the statement that pyrometallurgy is terribly polluting and creating carcinogenic waste more than hydrometallurgy. I am in this "business" for quite a few years, two or three in bigger scale for most of the time. Pyro is much easier to handle, if done right no toxic outgas is produced (and overwhelmigly less ammount of outgas to scrubb as with hydro) and if toxic waste as some metal slags is produced, it is fraction of the volume which is created by hydro treatment.
Rule of thumb is you need 4L of HCL and 1L of HNO3 to dissolve 1kg of base metal such as copper/nickel/tin alloys usually found in e-scrap. Say you want to process e-stuff that is net weight of 15kg in BM + precious metals. You will need to apply at least 75 L of acids, creating some 75L of acidic heavy metal waste. Which you then need to either cement or basify with unhealthy ammount of hydroxide, creating hydroxide or cement metal slime, which you either dispose or give/sell to large smelters. And I will say you, you better have few tons of it, because in smaller lots,
they don´t even respond to your request to take the metals FOR FREE.
On the other hand, you can pyrolyze/incinerate the lot of e-stuff down to metallic ingot containing every metal imaginable in one puddle. Then you apply pyrometallurgy magic, for example you oxidize reactive base metals like remains of iron (which should be avoided as much as possible in the feed), tin and lead by oxygen sparging of the melt (cost of the oxidant = 0 USD, in comparison with nitric acid around 1-2 USD/L tech grade bulk). You obtain relatively usable copper ingots with PM contained, which you then DOES NOT DISSOLVE, but electrowin to get payable copper and PM slimes.
These 15kg of BM would represent around 2 L of the molten metal. 35x fold difference against hydrometallurgy. And your tin and lead are nicely contained in the slag with volume equivalent to few bricks. Plus sellable copper benefit, not bleeding with hard to filter awful hydroxide cakes which nobody wants.
I am going pyro anytime I possibly can for the sake of my mental health and cost + time saving. Of course it need bigger starting capital, like building your own gas-furnance of suitable proportion, or even better - purchasing larger induction furnance. We have 35 kW one, and surprisingly you can get one under 5000USD, brand new from China. Electricity is much cheaper and effective than gas nowdays. Crucibles of these proportions are nowhere cheap, but if you are clever enough, you purchase dead-burnt magnesia for few bucks, and from mix of portland cement and magnesia press your own crucibles or scorifying/cupelling boats/trays. Or line the fine purchased SiC/graphite/clay crucibles with magnesia from inside to protect the crucible and greatly prolong it´s life.
