Well Josh, I never worked in the c(h)oke ovens, so I'm not sure how the constituents of coal are separated in the process. Turning coal into coke is done in the ovens, by heating the coal in the absence of oxygen. The retort would be part of the by-product recovery system, similar to separating the various parts of crude oil in an oil refinery. The various (gaseous) chemical components of the coal that are driven off during the coking process are recovered and then separated for sale or re-use elsewhere. The steel plant where I worked even owned a couple of interchange tankcars that they used to transport benzene, one of the by-products. Another by-product was coke gas, which was distributed via a very elaborate overhead pipe system to other mills, where it was used as a fuel for reheating slabs and ingots. Very corrosive stuff.
According to a text that I'm reading as I type this, one ton of coal yields roughly the following amount of coal chemicals and coke:
Blast-Furnace Coke......1,200-1,400 lb.
Coke Breeze................100-200 lb.
Coke-Oven Gas............9,500-11,500 cu. ft.
Tar.............................8-12 gal.
Ammonium Sulphate....20-28 lb.
Ammonia Liquor...........15-35 gal.
Light Oil.......................2.5-4 gal.
So, the coke ovens make the coke, and the retort is used to capture and refine the by-products created during the coke-making process.
Wayne