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Bulk Materials Handling – The Way Ahead

May 29, 2013

Throughout the world, the handling and processing of bulk materials, often referred to as bulk solids, are key operations in a great number of industries. Such industries are wide ranging, including pharmaceutical, food production, manufacturing, agriculture, power generation, and, at the ‘heavy’ end, mining and mineral production. Bulk materials predominately comprise particles of granular form ranging from micron size, such as fine powders and industrially created dust, to large rocks, a meter or more in size, as occur in Run-of-Mine ore in the mining and resources industries. Other bulk materials are non-granular in form, such as paper pulp, silage, domestic waste, and wood chips.
    Fundamental to the design of efficient and reliable handling systems is a thorough understanding of the way these complex and varied bulk materials behave under storage, flow, and handling operations. This requires a basic knowledge of the science and technology of particles and their bulk properties, and the way these properties are influenced by process and environmental conditions such as temperature, moisture, and consolidation. In view of the high component costs of bulk handling in industrial operations, it is essential that the handling of bulk materials be performed as efficiently and reliably as possible. The need for strict environmental controls over emissions and dust generation must also be considered.
    The foregoing remarks underpin the ongoing needs for research, professional education, and knowledge dissemination, which are essential to the future developments in bulk materials handling. By way of background, here are three examples that illustrate key contributions over the past 50 years are cited:
     Firstly, reference is made to the bulk solids research of Jenike and Johanson that emanated from the University of Utah in the early 1960s. The results of this work, together with the worldwide research that followed, has provided a sound basis for the design of such items as storage bins, stockpiles, feeders, and transfers. There has been wide acceptance by industry of this important technology.
    Secondly, in the area of transportation, long distance overland belt conveying is considered. Studies have shown that the most efficient and economically viable solution is to employ belt widths in the range 800 to 1200mm in combination with higher belt speeds. Speeds ranging from 6 to 10m/s are now a practical reality. Noting that the indentation idler rolling resistance losses can consume as much as 60% or more of the conveyor drive power, one current area of research is aimed at the reduction of these losses. To this end, new belt indentation-resistant rubber compounds are being developed, along with belt tension and idler spacing optimization studies. Another area concerns the reduction of the losses due to the flexing of the belt and bulk material as the belt moves over the support idlers. Typically these losses may consume 15-20% of the drive power.
    Thirdly, the advances in computer simulation are acknowledged. For example, Discrete Element Modeling (DEM) is now a widely accepted analysis tool for handling plant design, particularly transfer chutes.  There is no doubt that the animated, graphical computer display of the way bulk materials flow through a bin or transfer chute has the advantage of conveying a sense of realism. However, as a cautionary note, there are currently some pitfalls. These involve the long computer run times, days and sometimes a week or more. Also there is some uncertainty in specifying the correct material parameters for the simulation model and the influence of the assumptions made on the credibility of the results. For these reasons, the combination of the continuum mechanics approach with DEM is recommended.
    As a final comment, over my 50 years of research and consulting in bulk materials handling, I have been continually reminded that the problems in industry are often orders of magnitude more difficult than the level of research available to solve them. So research has to play catch-up. This has been the motivating influence for the University of Newcastle, Australia, and its associated industrial consulting arm of TUNRA, to initiate the introduction of the subject areas of bulk materials handling into the engineering curriculum. The ongoing teaching, research, and industrial consulting over the past 37 years, have proved to be most successful. It is important that this continues.   
    Alan Roberts is an Emeritus Professor at the University of Newcastle, Australia, and the Founding Director of the University’s Research and Consulting Company, TUNRA Bulk Solids, which he established in 1975. Roberts has been involved in bulk solids handling for 50 years, and has been published widely in this field.

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