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Fulmen
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It works, even if it's a bit slow. IIRC the initial reaction is slow, but increases a bit once you have copper in solution. But any air-powered
reaction will be slow, that's just the price to pay for free oxidizer. So what? Time is cheap if you don't have to monitor the reaction. I don't think
sulfuric acid and air will be any faster.
One benefit of this reaction is that it produces a dense copper carbonate powder of uniform composition, something that is impossible with direct
precipitation.
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clearly_not_atara
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You might be able to kickstart the reaction with ammonium persulfate like I suggested earlier. It's Cu(NH3)2(+) that gets oxidized by oxygen to
Cu(NH3)4(2+)
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Sulaiman
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I think that if you 'burn' the copper eg on a BBQ grill) to form an oxide layer it will dissolve in HCl much easier.
When the reaction slows, burn the copper again.
CAUTION : Hobby Chemist, not Professional or even Amateur
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Fulmen
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That should work, but I doubt it will be fast. And it will require more work and energy. For a small batch it's probably doable but for 20kg? Air
oxidation is slow, but it can be done with little effort and a small aquarium air pump. I've done this both with ammonia/CO2 and sulfuric acid, albeit
not on such quantities.
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pesco
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Chemicals pricing and availability depends on your location. In most places HCl is the cheapest mineral acid. Can be even cheaper, if you make it
yourself and you can easily do it in huge amounts for free or nearly free. Just pyrolyze some PVC, preferably uPVC or CPVC and you'll have gallons of
HCl.
From that pile of Cu I would select some somewhat clean pieces and
1) electrolyze in NaCl solution to obtain Cu2O or CuO. Best precursor to Cu salts.
2) melt some cables (purer) to get nice electrode for electrochemistry or cementation of Ag
Other bits, dirty, tiny wires, difficult to strip or mixed with Sn/Fe I would stick in sealed steel paint can or similar and pyrolyze. Gasses pass
through water to scrub HCl and then into the fire to neutralize. If the fire is HOT (500+ °C) and the gasses stay there for around 1-2 seconds then
all the nasties will get destroyed.
Once pyrolyzed and Cu exposed flood it with HCl.
PET bottles outside work very well. PET is UV stable and bottles wont disintegrate after a while spilling the content. I have PET bottles in full sun
for couple years and they seem to be still like new, just dirty  . I keep the
bottles inside old aquarium placed on its side. That way rain doesn't get into the bottles, even very strong wind wont knock them down and the
temperature get a bit higher when Sun is out speeding up reactions.
HCl works initially slow, but once some Cu dissolves the dissolution speeds up. If you place and aerator in the bottles then it is pretty fast.
Aquarium airpumps work great, they are cheap and need very little electricity. Wouldn't bother with peroxide, too expensive in these amounts and not
necessary, especially if you are not in a hurry.
Dissolution by HCl is not as fast as HNO3, but the later is nearly everywhere difficult to obtain and WAY more expensive than HCl.
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Fulmen
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HCl + nitrates should work as a substitute for nitric acid.
We're not banging rocks together here. We know how to put a man back together.
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