With an ever-greater focus on the potential effects of climate change, the world is looking to alternative, and in particular, renewable forms of energy. While storage of energy is a particular problem, electricity grid stability is another. While there is a move to a much more distributed supply grid, it is clear that there will be a continuing need for base load power, particularly for industrial applications in the short to medium term. Europe and the US have seen significant increases in the use of biomass materials as an alternative fuel source to coal to help mitigate environmental impacts.
The use of biofuels provides a significant problem for power stations since the calorific value of biofuel is, for the most part, significantly lower than that of coal. This requires significantly higher volumes of biomass to be transported, stored, and handled, leading to some significant challenges. Many of the materials that form biomass have significantly different handling characteristics when compared to many of the mined and processed materials we are used to dealing with.
Biofuels come in a variety of forms. Pelletized fuels are more regular in shape and have reasonably predictable handling characteristics, but the cost of pelletizing is one that industry would prefer to avoid. Raw biomaterials are often stringy and exhibit significant compressibility, which is difficult to handle reliably.
This move to handle a much wider range of bulk materials with very different bulk properties is not limited to the power industry. This is an issue for many industries that have a need to handle and transport bulk materials. The challenges are around feeding these materials into conveyors and retrieving these materials from bins and silos under gravity. A particular problem is predicting material behavior in such a way that the analytical tools we use for design of systems can be used reliably.
However, these problems are not new. The significant increase in recycling technologies developed over the last 20 years or so have seen these challenges grow, leading to significant work to understand the mechanisms that underpin the material behavior. For example, the permeability to gas flow of these materials under a variety of degrees of compression and the degree to which water will drain from these materials in the saturated state. A state often required for recycling processes.
There are no magic solutions to these challenges but a real need for the science to catch up with the technology needs of industry. In recent years, collaborative research has been undertaken between the University of Newcastle, Australia and the University of Pittsburgh in the US on understanding the stress states of these materials when conveyed through pipelines. The team at Pittsburgh has developed a ‘smart’ particle that is able to sense the accelerations applied to particles which has allowed a much better understanding of the interaction between particles when being conveyed in pipelines. While the findings have been remarkable and have advanced our understanding of pipeline transport there is much to do in translating this knowledge to practical outcomes for industry.
We are not alone in these endeavors and there are many groups around the world working to better understand the behavior of such materials. However, it is work of this nature that has the potential to develop our understanding in the field of materials handling and will help us to develop a better understanding of the behavior of a new range of bulk materials that are being encountered by industry. The challenge is to transform this new knowledge into usable technology that benefits industry.
Professor Mark Jones holds the chair in bulk solids handling at the University of Newcastle, Australia. He is also the director of the Centre for Bulk Solids and Particulate Technologies and director of TUNRA Bulk Solids Handling Research Associates. For more information, visit www.bulksolids.com.au.