Improving the assessment of process reagent plants and utilities for high temperature hydrometallurgical process plant during early stage project development

Abstract

The current approach taken during the early stages of project development for high temperature hydrometallurgical plants (HTHPs) does not allow time for evaluating process reagent plants or adequately assessing the potential to recover low grade waste heat (LGWH). Therefore, there is a greater risk of making sub-optimal decisions when selecting process reagent plant technology and integrating LGWH recovery into the overall facility design. These decisions have a detrimental impact on energy efficiency and economic outcomes.The primary reason for the lack of integration of process reagents plants -and the related assessment of LGWH available for recovery -lies in the absence of a modified gated project development methodology, including the necessary models, to allow for better decision making in the early stages of project development.A modified project development process has been developed for use from the Scoping Study (FEL-1) stage to Front End Engineering Design (FEL-3). This methodology will allow project design engineers to independently and efficientlyusing minimal effort -evaluate and rank process reagent technologies by plant type and also by combination, for a given set of technical and financial parameters.The methodology includes the use of empirical models for hydrometallurgical plant and process reagent plant prediction, which have been developed based on actual plant design data. The models can cater for different hydrometallurgical plant scopes and a range of plant capacities. The evaluation was undertaken using a purposedesigned, integrated technical and financial model.Case studies based on a nickel laterite flowsheet were developed to demonstrate the evaluation process; the ultimate objective was to select and rank the combinations of process reagent plant technologies. The evaluation also identified how changes in major operating cost inputs affected technology selection.The benefits of applying the developed methodology during Pre-feasibility Study Level (FEL-2) include earlier selection of process reagent plant technology and specification for Front End Engineering Design (FEL-3). As a result, more definitive information is provided for procurement activities. Additionally, this approach Page iii produces an integrated overall plant facility design, maximising the project's economic value and minimising future evaluation effort and potential re-work.The key outcomes from the research were:  Electric power generation of up to 50% of total plant load is potentially available using organic Rankine cycle LGWH recovery technology for the metals plant scope, with corresponding significant greenhouse gas emission reductions. The methodology could be extended to include other material flows such as water, process flow sheets with similar characteristics, and the design and evaluation of suitable engineered multi-component systems. The viability of the recovery of LGWH is improved when included in the early stages of design, as the options can be appropriately assessed in conjunction wit...