Intelligent ore measurement
CONVEYED flow quality measurement in real time provides the next level of plant control where there is higher variability in composition than sites expect, but a solution has been developed by analyser experts Scantech.
The Scantech GEOSCAN-M elemental analyser provides real and innovative approach using proven, real time measurement solutions for conveyed flow quality management.
Natural quality variability
Mined material is not homogeneous; in some cases the mining process accentuates the quality variability by adding dilution or waste as a result of the way the good and poor quality materials are interspersed, and so cannot be selectively removed.
Materials handling may mix the more and less valuable components to generate a blend.
Actual measurements show that this mixing still leaves considerable variability by the time the material reaches the next stage in the process.
Processes have been developed to take the as-received material and utilise separation techniques to recover valuable components and discard unwanted material as waste.
Such processes work well when the feed is relatively good and of consistent quality, but respond poorly to high variability in the feed quality, with recovery and efficiency sacrificed.
A major opportunity exists to improve existing process performance in most plants – resource companies recognise that in order to control feed quality, it needs to be measured.
Benefits from measurement
Scantech has designed its analysis equipment so that it can be easily installed on conveyor systems, allowing for continuous real time quality measurement.
It maximises benefits by integrating with existing infrastructure for bulk flows and providing opportunities for gains in process control by measuring and reacting to changes in material quality.
GEOSCAN-M
The GEOSCAN-M is a high-performance elemental analyser utilising Prompt Gamma Neutron Activation Analysis (PGNAA) to measure the elemental composition continuously in real time, through the full conveyed cross section, so that the entire flow can be representatively measured.
The GEOSCAN-M utilises a Californium-252 source to excite the elemental nuclei in the conveyed flow with neutrons, which in turn emit gamma rays that are detected by a high-specification detector array above the conveyor, allowing individual elements to be measured directly.
This configuration, combined with proprietary software, yields measurement performance that is unmatched in the minerals industry.
The GEOSCAN-M is combined with Scantech’s TBM microwave moisture analyser, and takes an input signal from a belt weigher to provide tonnage-weighted average dry basis elemental and moisture results on a short analysis period to the plant control system.
The GEOSCAN can be configured to measure over shorter or longer time increments depending on the application.
Where bulk sorting is required, short analysis – say every 30 seconds – allows for a minimal sorting increment mass, whereas for blending purposes, a longer measurement time of, say five minutes, may be appropriate.
Typically results are reported every one or two minutes.
Mining applications
Ore quality in the ground is defined from drilling, sampling, laboratory analysis and geological modelling to assess geological continuity and grade distribution.
The resulting information is used to create a mining plan so that suitable material can be extracted in a sequence that satisfies operational and mining lease regulatory requirements.
Quality of most conveyed ores can be measured in real time with a GEOSCAN-M to determine the multi-elemental composition.
The analysis not only confirms the aforementioned mining plan, but offers results with a much finer resolution, allowing for real, positive control of the plant.
Moisture can be measured using a TBM moisture analyser, typically to accuracies better than 0.5pc.
Moisture content can also impact the process performance and measurement may also assist with dust management or dry tonnage basis calculations.
Bulk ore diversion
Detection of waste or different ore qualities can be used to divert increments of conveyed flow to different stockpiles.
Bulk diversion (bulk ore sorting) requires a flow diversion process to be activated by the plant control system using real time GEOSCAN-M measurements.
Delay time between GEOSCAN and diverter is taken into account so that each increment is diverted as accurately as possible.
Low quality material can be rejected entirely, so it is not processed or diverted to a stockpile.
Only high specification analysers have proven effective for bulk ore sorting as very short measurement times with good measurement accuracy are needed to optimise selectivity (<10t per increment for 1,000t/hr flow) and maximise confidence in diversion decisions.
GEOSCAN-M is also suitable for measuring pebble recycle quality to determine whether pebble flow increments should be diverted or processed.
Ore blending
GEOSCAN-M can measure the conveyed flows and adjust the proportion sourced from different quality stockpiles.
Adjusting the blend in real time allows a more consistent feed quality to the process plant, improving its performance, as high variation leads to inefficiencies, e.g. in metal recovery.
Measurement of such components as acid-consuming gangue, sulphide content, clay content and moisture in the feed can be used for optimising flow rates, reagent dosing, metal recovery and concentrate/ product allocation.
Even very small improvements in process plant performance and consumable savings will achieve very fast analyser payback.
Blending can also be used for products to ensure specification compliance and particularly to blend out high contaminant levels.
Plant performance
Most plants perform most efficiently when a consistent quality feed material is provided, so knowing when there is a major change in feed quality before it arrives in the plant is useful for ensuring appropriate control systems responses.
Geometallurgical domain changes may also be detected in plant feed through elemental measurement, which may assist process operators to continuously improve plant performance as recognition of certain ore types can be related to previous process performance.
Who is Scantech?
For more than 35 years, Scantech has been leading the development of innovative solutions using continuous, conveyed bulk analysis technologies that penetrate the full flow and produce representative, accurate, timely and reliable results, with 1100 units sold in 60 countries worldwide.
Focus on the minerals sector has resulted in a high-specification, minimal maintenance, robust design to exceed typical measurement expectations.
The highly qualified, experienced and motivated support team provides a wealth of knowledge in optimising applications and performance. Authors: Scantech technical manager Dr Luke Balzan, and minerals consultant Henry Kurth. h.kurth@scantech.com.au l.balzan@scantech.com.au sales@scantech.com.au Scantech International will exhibit at IMARC booth A13.