Ann: Q4 2023 SX Operations Update, Cloncurry, page-14

Interesting they refer to metallurgical advice. Previous metallurgical advice was that they clearly were not able to achieve any of the production estimates used, given the huge variation from what they originally planned to do, which would have provided good cashflow. They just ignored any competent advice, terminated the consultant, and shopped around until they found someone prepared to tell them what they wanted (just like Tombola did, and we know how that ended).
Earlier they were claiming copper recovery figures of 80%. That may have been for the SX transfer, but it is the recovery and grade of solution off the heap leach that are needed for production. The SX plant copper extraction capacity is vastly oversized for their requirements, so will never be a bottleneck to production. 80% of bugger all is still bugger all.
As for claiming hot weather as the reason for low production, that is the opposite of all previous operational experience for that and many other SX plants, as previously it was cold weather that restricted production, due to solubility issues reducing transfer grades to the crystalisation plant. It is copper solution grade, acid addition and temperature differential in plant that drive crystal production, not absolute temperature. A bit of a failure of basic copper sulphate chemistry knowledge in making that statement.
At the end of the day, the lower than predicted copper sulphate production comes down to too little copper leaching from the heap leach and at too low a rate. To make money off heap leaching you need an economic leach rate in terms of copper units and PLS grade. The decisions not to agglomerate and not to add acid to the material when stacked mean that economic leach rates would take months and probably not be achieved for the ores used. The fact that a lot of the ore was actually material which had been previously under leach by at the Mt Norma operations. It was obvious to the board from the start of trading on the ASX of TNC in June 2023 that the copper sulphate plant would not be profitable until substantial additional acid leachable ore was delivered to site, something which is still not shown in any of their public announcements. Yet they continued to make public statements to the effect that copper sulphate production would cover operating and ongoing exploration costs.