value of zinc process, page-16

Hummmmmmms...

Re baghouse /EAF dust. Not sure whether I fully understand the question, but the baghouse is just a unit operation that is commonly used to separate dust from a gas stream. Another method is electrostatic precipitation.

Baghouses are used at the backend of EAF's, so in that case, baghouse dust and EAF dust are one and the same thing. As discussed earlier, there will be zinc in the dust if galvanized scrap is in the charge. The Zn concentration in the dust will increase with % galvanized material. The Zn concentration will be much higher in the dust than in the initial scrap charge.

I'm not sure whether you are also talking about baghouses from other processes. If so... which process?

Re prepainted steel/zincalume.... let's not confuse the issue of regenerating pickle liquor with reclaiming metals from other streams. EARS is appropriate for iron and (apparently) zinc chlorides in an acidic solution. In the process for prepainted zinc or zinc/aluminium coated steel, the oily surface is cleaned in an alkaline bath. Any zinc or aluminium that might be attacked by this solution is in quite a different form than what EARS is for.

Prior to hot-dipping steel coil in zinc or zinc/aluminium alloy, the material is de-scaled through an acid bath. The spent solution is ferrous chloride/hydrochloric acid . Can't see why this would have any zinc.

Galvanizing plants also acid pickle the substrate first. If this is steel.... then no zinc. However, the substrate may have been previously galvanized, in which case you begin to get zinc-rich pickle liquor destined for APG.

I don't know much about the galvanizing industry and could be wrong, but would take a stab at EAF dust being the zinc-rich stream of interest to APG.