Experts from TUNRA Bulk Solids look at some of the current bulk handling tech trends and how new testing and simulation techniques are required to keep up in an evolving landscape.
The depletion of high-grade mines, combined with advancement in mineral processing technologies, has transformed sub-economic minerals into valuable ores.
Tailings valorisation, alongside the decrease in popularity of dams as storage facilities after major accidents of Mariana in 2015 and Brumadinho in 2019 has also led to changes. Now, there is a significant increase in the need for storage and handling of “dry” tailings, and the consequent need for flow properties testing and characterisation of materials that were previously less frequent.
Tailings, lower-grade, and below water table ores all have something in common: they are typically difficult to handle and can be very challenging to test with traditional testing technologies.
Direct shear tester and design charts have come a long way since Andrew Jenike’s pioneering work in the mid-1960s on storage and flow of bulk solids, and they still form the basis for the design of materials handling facilities.
However, these methods have limitations and may not produce useful results in the case of very plastic materials. Furthermore, the trend towards sustainable mining and energy sources requires handling materials with previously unseen characteristics, such as the rapid increase in global demand for rare-earth metals. This increase in demand brings many challenges that include the need for new methods of materials handling assessment.
Increased focus on sustainability generates the need for improved design:
There is a continued focus on environmental and health concerns related to dust emissions in the energy and resources industry. In Australia, the Work Health and Safety Act and Regulations set out the limits of exposure both in terms of a Time Weighted Average (TWA) and Short-Term Exposure Limit (STEL), which must be observed.
Dust remains a key challenge in designing and operating specific links in the materials handling chain including transfer chutes and train loading, as well as in the holistic management of rail and port operations. With the short supply of water continuing to be a key challenge, active dust suppression is being replaced wherever possible by passive dust control through effective design.
This has propelled the use of characterisation techniques such as the determination of the Dust Extinction Moisture for materials beyond coal, even though the dustiness test (Australian Standard AS 4156.6-2000) was originally developed for Australian coal.
The combined use of laboratory characterisation including the dustiness and wind tunnel testing, and computational simulations like Computational Fluid Dynamics (CFD) to assess dust propagation and scale modelling, have become a design requirement for many operations, with some major players conducting regular tests several times a year.
Plant efficiency requirements drive advanced monitoring and simulation techniques:
Higher throughputs are needed to meet demand while keeping changes to existing plant to a minimum. This results in an increased number of brownfield projects with very challenging design requirements. Stopping production for unplanned maintenance is a costly exercise, and so, to avoid downtime, facilities are now increasing the use of online monitoring techniques. These include moisture measurement, elemental composition, and online wear monitoring through IoT or wireless sensors to monitor liner thickness and estimate remaining liner life.
The rise in computing power and advanced simulation techniques have acted as a catalyst for the development of more accurate means of predicting performance. A good example of an advanced simulation technique is Discrete Element Method (DEM) modelling, which has grown in importance and is now becoming a design requirement for many applications. Another technique more recently being applied to bulk solids handling applications is Smooth-Particle Hydrodynamics (SPH), which shows excellent promise.
DEM as an engineering tool can be readily deployed in a range of applications to improve site operations. However, it is still evolving through continued development of calibration techniques, such as laboratory testing and the use of laser scanning, drones and site data. Its underlying models are continuously progressing as well: new breakage models allow the assessment of breakage in situations where particle integrity is key, such as when handling iron ore pellets, sinter or coke.
SPH, on the other hand, is a numerical technology for modelling viscous fluid flow that is quickly maturing from being confined to the academic and research space to finding practical applications within industry. It has seen increased application in the minerals processing universe, used for applications such as tailings flow, wet screening and slurry chutes.
What the future holds
In a world where large amounts of data are easily accessible, turning data into knowledge is the next step for value generation. The future of materials handling industry requires online measurement turning into decision-making. For instance, some plants are looking into using online elemental composition and moisture measurement to define which materials should go through a certain handling line at a given time.
The changes in materials handled, the need for higher throughputs and stricter environmental regulations have also contributed to a push for further research and development in the materials handling field: research into highly adhesive materials is laying the ground for new testing methods, as well as new calibration procedures to ensure that DEM simulations reflect material flow more accurately in conditions that traditional approaches may not suit.
The future of materials handling is bright, and applied research is the only pathway forward.