Forgive my feeding this necro, but in an attempt to bury this thread that must be well search indexed for a common problem that exists in various forms to this day. I will provide the solution to the bin problem, which somehow has been overlooked for 9 years in favor of trolling necrotic replies. Excluding: Areyar who while necroing also provided a solution.
Problem: Charcoal in bins can't be used by smelters
Solution: Don't put them in bins. Make sure the only stockpiles that accept charcoal(bars - other - Coal) don't allow bins.
To elegantly do so in the current version, use an input stockpile(3-6 tiles) > hauling route + mincart stop > output single tile Quantam stockpile.
My Setup in 40.24:
Workshops&Q-piles
Ore Q-pile settings
Q-pile contents(under yellow X)
Explanation text for above images:
The ore stockpiles are set to accept all Metallic Ore, all Economic Stone(flux etc), one other stone (raw adamantine), Only Coal from Bars/Blocks, Only Adamantine Strands from Cloth.
The weapon and armor piles accept anything but masterwork & artifact metal armor, so I can easily designate the single square with hundreds of crap items for melting at magma smelter.
Craftdorfshops were added as a hasty afterthought for adamantine strands. Wood furnaces since I have no liginite and must make charcoal by infuriating elves. These additions put the entire production process tightly packed in the one little workshop area. The central stairwell(white x) leads to a simple wood stockpile below and Masterwork & ammo piles above.
For completeness here are the lavatubes for the magma shops and woodpiles 1z below.
And the masterworks(steel, silver, adamantine & an artifact copper shield) sitting 2z's above.
My only complaints about my own setup: ores from one side of map always end up in the closer of the ore piles.. so smelters walk into the adjecent complex to get what they need.
My next fort will have only one of each type of Q-Pile feeding 2 workshops each.
TL(DR)ButReadAnywayBONUS TIP: No more Useless Ring/Amulet/Toy etc. Artifacts!
I just set both of my magma forges to allow only dabbling weaponsmiths, then used therapist to group by highest moodable skill, and select all highest mood craftdwarfcrap peasants and enable weaponsmithing. I now have 40 of the 120 worthless bastards converted to highest mood = weaponsmiths, with the other 80 waiting their turn on a forge to go from dabbling to novice. I can easily melt all their worthless copper and silver shortswords back to bars.
If any more peasants decide to have a mood before the conversion completes. I will lock them up and starve them as soon as they claim to avoid them stealing any more candy for turtle shell bone helmets or even more worthless garbage!