REDUCING ROTOMOLDING ENERGY FOOTPRINT
In October, if you were one of the rotational moulders who had the opportunity to attend the ARMO conference in Lyon, you saw first hand, many of the advances in energy efficiency occurring in the world. Global events like Lyon 2012 provide a great learning tool and promote awareness on ways to reduce energy use. Welcome to the last energy and sustainability article for Rotoworld in 2012.
The Europeans have really made great strides in reducing energy over the last 20 years, in large part a result of European Union regulations implemented to curtail carbon dioxide emissions by all industries (including rotational moulding). The EU is probably the strongest advocate of climate change prevention. With these regulations, include taxing energy consumption; the intended result has been to force companies to reduce the inefficient use of energy while maintaining profitability. Unlike other regions that enjoy cheaper fuel costs, the European industries face these challenges yet continue to be strong financially.
I believe that, in time, energy will become more expensive globally as these resources becomes scarcer and extraction more difficult. It will become a competitive advantage for those moulders who can reduce their energy footprint. Rotational moulding has poor conversion efficiency (3%-8% with energy converted to kg of finished product) so there are lots of opportunities to improve.
From my travels throughout the global rotational moulding community, I’ve seen more companies eliminate water-cooling (air only) from their process. Air only is actually quite effective as it reduces warpage, avoids the challenges associated with collecting and draining excess water, and can extend the life of the tooling (avoids shocking the metal components). One more advantage of air-only cooling is that you can implement a strategy to insulate the arms. If you don’t require water then it becomes possible to insulate the arms because you avoid the negative effect of insulation becoming saturated with water and adding to the large heat sink associated with the arm construction. There are a number of materials available that can effectively shield the heat. My company and others are investigating these options and I hope to report back to the industry early next year.
From our initial assessment, I also believe that the energy savings, with arm insulation, won’t be limited to the heating cycle only. Cooling should also be accelerated using the same rational. This opportunity was demonstrated by the work of LightManufacturing in California. This unique company has become a real game changer in rotational moulding and has mastered the use of solar energy in the process. While essentially eliminating any need for carbon based energy, they have shown that by focusing heat at the tooling only (eliminating an oven)
they have reduced cycle times in heating and cooling.
Another development that I introduced in a presentation at Lyon 2012 is the strategy of pre-processing polymer to reduce heat cycles. My company has been undergoing trials on this over the last year and we’ve demonstrated as much as 18% shorter heat cycle times. This is significant and our initial trials have been shown that there could be more opportunities to increase these savings. At this time, we’ve only introduced the heat to the polymer by the use of a high shear mixer. The process is fast and repeatable. The downside is that it requires new energy into the process, something we would like to avoid. We’ve identified another strategy using waste heat from the process and we hope to report back to the industry later in 2013.
Finally, for this article I’d like to outline another opportunity to reduce the heat cycle that I also presented in Lyon. This strategy involves the use of air directors. Because there are a wide variety of oven configurations available in commercial and custom-built machines, there is no real standard in airflow. My company has invested a considerable amount of time to study airflow and the effect it has on cycle time reduction. We’ve developed special fluted directors that can focus the airflow and optimize the heat transfer to the polymer. There have been challenges specific to part geometry and orientation on the arm but I can report that we’ve been able to demonstrate cycle reductions approaching 20%.
My company is not the only contributor in this effort to make the process more efficient. I’ve had the opportunity to visit other facilities worldwide that are developing strategies to get more from the energy we use. Together I think that we can all make the difference to raise the bar for our process.
Bill Spenceley is the President/Owner of Flexahopper Plastics Ltd. located in Lethbridge, Alberta, Canada. He has been involved in the industry for over 30 years, travels extensively and currently serves as President of the Association of Rotational Molders. He has been a frequent presenter on energy reduction in rotational moulding and holds a BS Chemistry with studies in Chemical Engineering.