Abstract
In 1998, Terry McNulty presented an SME paper that surveyed 41 processing plant case histories and identified the dominant causes of success and failure. That survey resulted in creation of four curves, graphically portraying the approximate rates of achievement of design capacity over time for projects that ranged from very successful to marginal to unsuccessful. Identifiable characteristics included maturity of technology, level of understanding of the resource, depth of characterization of the feed material, thoroughness of laboratory development of process design criteria, and the degree of planning and execution of pilot plant test campaigns. Updates were presented at SME 2004 (Denver), COM 2014 (Vancouver), COM 2024 (Halifax) and Extraction 2025 (Phoenix). These so-called “McNulty Ramp-up Curves” have been widely adopted by operating companies and project financing firms for use as a checklist for risk assessment and for ranking competing capital investments.
Most of the case histories underlying the McNulty Curves have been based on traditional commodities. Industry electrification and climate change technologies, as well as the current trend to develop domestic supply chains for non-traditional or critical commodities (such as rare earths, graphite, lithium, nickel, cobalt, gallium, germanium, and antimony), have led to the launch of new mineral projects. While traditional commodity projects can be benchmarked against existing projects to assist in derisking and generating capital and operating cost estimates, this is more difficult for critical mineral projects. Without bench marking, additional engineering studies supported by extensive laboratory programs and comprehensive pilot and/or demonstration plant operations may be required.
This paper will present ramp-up curves for recent critical mineral projects using production data in the public domain. The authors will then contrast the actual ramp-up performance with the predicted ramp-up performance as published in recent prefeasibility and feasibility studies. Clearly, some lessons learned have been incorporated into predicted plant ramp-up performance. We have also observed that aurguments to support optimistic plant ramp-up performance often have not been provided.