Plant Optimization

PLANT OPTIMIZATION STUDIES CONTRIBUTE SIGNIFICANT VALUE

SGS Minerals Services has a long-time and growing reputation for in-plant improvement and optimization studies. Recent studies in PGE operations have brought one plant from the verge of bankruptcy to a healthy, profitable business, and, in a separate plant, has increased mineral recovery by as much as 6%. A systematic approach can determine if similar improvements can be made in your plants.

What is Plant Optimization?

Plant optimization studies range from basic survey design and supervision, to complete survey programs. At all times, the work is done in close association with plant personnel. When necessary, SGS Minerals Services may provide all the manpower and equipment required to complete sampling, and sample processing, sizing and assaying services or we work with existing staff.

Why Optimize a Plant?

Optimizing of plant operations can considerably increase profits with only a small outlay in costs. Payback time for this outlay is commonly weeks or months. Any improvement in product recovery or quality, with minimum capital outlay, results in additional revenues that directly increase profit.

The following situations would most likely benefit from plant optimization:

• Newly-commissioned plants
• Plants that have experienced gradual changes  in ore type, evolution of the treatment scheme and/or personnel changes
• Existing operations that do not have a formal and systematic optimization program

Overall Plant Optimization Process

SGS Minerals Services' plant optimization service usually begins with a pre-audit and follows with cycles of optimization. Any major improvement in plant results will occur after the first cycle, but, since it is difficult to forecast exactly how a plant will react to the changes, a second survey may well indicate further beneficial changes needed.

Pre-audit Process

The primary objective of the pre-audit is to establish how much potential improvement could be gained by formal plant optimization, and what the optimization program would entail. It can also sometimes reveal immediate opportunities for process improvement.

The pre-audit includes:

• Statistical review of operating performance.
• Calibration of plant performance against standard laboratory testing.
• Basic metallurgical diagnostic work.
• Discussions with plant management to establish client priorities and an appreciation of the background to plant operations.

Cycle(s) of Optimization

After the pre-audit, most plant optimization programs follow at least one cycle of optimization. This cycle is segmented into several discrete phases.

Plant Operations

Throughout this exercise metallurgical performance is carefully scrutinized. Increased shift sampling, by SGS Minerals Services or plant personnel, provides a more detailed, day-by-day analysis of how the plant is operating. This information yields evidence of individual unit process or circuit performance, circuit overloading and the creation of large, often deleterious, circulating loads. Diagnostic studies are conducted on the circuit feed and tail streams to characterize the ongoing responsiveness of the ore to standardized laboratory treatment.

Plant Survey

The plant survey is the core part of the plant optimization program. It is designed to provide:

• A snapshot of the typical concentrator operation (benchmark for circuit optimization)
• A mass balance to obtain equipment loading information
• A comprehensive distribution of critical elements throughout the flowsheet
• Product quality information for the various flowsheet stages
• Performance information on circuits or individual unit operations
• Samples for selected diagnostic analyses
• Samples for mineralogical examination
• Information regarding grinding efficiency

Diagnostic Testing

The survey data completes the picture of what is happening in the plant, and diagnostic testing is used to identify why. Several approaches are used:

Size-by-size assaying to

• Evaluate size distribution and metal distribution in a circuit feed
• Establish liberation limitations
• Diagnose process mechanisms, e.g. efficiency of recovery in individual size fractions
• Determine metallurgical and economical implications of potential changes (e.g. modifying the size distribution of the feed to the grinding circuit could  have certain potential benefits)

Grinding diagnostic work to

• Quantify the efficiency of the grind
• Provide an indication of the potential benefits associated with grinding circuit optimization i.e. reduction in energy consumption, increased fineness of grind, reduction in slimes production

Such tests include

• Bond rod and ball mill grindability testing
• MacPherson autogenous work index testing
• JKTech drop-weight testing
• JKSimMet simulation and modeling

In-plant testing to

• Simulate a wide range of process changes on site, either at the bench or pilot scale
• Define viable solutions to identified problems or circuit limitations

Mineralogy

Process mineralogy looks at the disposition of the individual minerals in the products, and often explains why certain processes are not behaving as expected or desired.

Selected plant samples can be subjected to a wide range of mineralogical analyses:

Ore Mineralogy

Techniques available include qualitative optical microscopy to fully automated, quantitative techniques including QemSCAN and optical image analysis.

Trace Element Deportment Analysis

Used to understand the deportment of precious elements and deleterious trace elements such as mercury and selenium. Techniques used include electron microprobe, proton microprobe and ion microprobe (SIMS).

Process Solution Chemical Analyses and Surface Chemical Analyses

In hydrometallurgical plants, and to some extent in other processes, the study of the chemical compositions of the solutions is equally as important as the mineral compositions. Chemical changes can result in more rapid recovery, or increased recovery of the values.

Review of Data and Process Recommendations

Once the findings have been reported, and recommendations made, SGS Minerals Services is often asked to consult with diverse groups, including technical personnel, plant and senior mine management and the corporate board to help implement the changes.