Riddle me this, what type of supposed Engineer would think it is okay to build a demo / pilot plant without conducting a '"fancy DFS" for your actual resource?
The purpose of DFS serves numerous purposes - project viability, financial metrics, resource specifications for one's flow sheet, detailed metallurgy, technological risks, etc. Conducting a bench scale for the flow sheet would address a few of those issues. It is very odd AGY choose not to conduct a DFS - it says a lot about the people running this company !!
