Better step for remove iron with HCL

[orvi]

Iron (without roasting) or iron oxide (after roasting) removal is not required in most cases of pyrite processing. The best way is to use direct smelting of pyrite concentrate with Na2CO3 and lead as a collector (in this case you don't need roasting at all - all iron will form iron-sodium slag). The second way is to use a high-temperature thiosulfate-ammonium-copper leaching process. Iron oxides will leave intact in the leaching wastes.

Depends on quantity of the cons and richness. As for pyrite, you need to add whole lot of soda to break possible matte layer forming. All doable, but with poor quality cons, cost of the flux will be quite ramping. If leaching is applicable, it is a way to go. Slow roasting at lower temperatures with good scrubber (for SO2 and possible arsenic) will leave iron oxides, which are relatively easy to pulverize even more, and then leaching is relatively effective if setup is right.