A fine idea for a greener future
Powder coatings are well-known for their intrinsic environmentally-friendly credentials - no VOCs, no harmful substances, low waste, low energy consumption - but the green story doesn’t end there. AkzoNobel is looking to reduce its own carbon footprint by a minimum of 20% by 2015 (based on 2008 levels). Should the business expand during that time, then we have pledged that our carbon footprint must be no greater than 2008 levels.
This means looking at all aspects of the business from recycling packaging to installing motion light sensors; reducing energy consumption to ensuring, as far as possible, raw materials come from renewable sources. But it’s in our methods of production where we felt we could have the most impact. Hence, in 2005, we set up the Process Innovation Team. “Essentially, I sent two people off to walk around, observe our production processes, ask awkward questions, and come back with ideas,” explains Frank van Ooijen, Operations Director.
One of the first things noticed by the team was the amount of very fine powder particles - or ‘fines’ - that are inevitably created as waste during the milling process. (This is the final stage in the production process after the resin and pigments have been heated and mixed, rolled into sheets and broken into thumbnail size ‘chips’ which are then milled to the required particle size.) Although these fines are mixed with waste dust, they are perfect quality powder; yet the majority of the waste was going into landfill. Was there a way of extracting these fine particles - which make up about 25% of the waste - reconstituting them and then re-milling them to the required particle size? And, crucially, a way that fitted in to the flow of the production process without adding significantly to time and costs? As van Ooijen neatly puts it: “We needed an engineering solution that was economically viable.”
The answers were ‘yes’ and ‘yes’. The ultra fine ‘waste’ powder is collected from the filtration stacks and then compressed between rollers where the heat caused by the pressure forces the particles to melt and form into larger chips which can be re-milled to the required particle size. “We designed the compacting rollers to fit next to the filter bags so there’s no intermediate storage and handling,” explains Andy Morgan, the Process Innovation Team’s research associate. “At a conservative estimate, we reckon around 2% of product was being lost in fines. On a global basis, if we could re-process this, it would mean we could save 4000 tonnes of powder a year.”
Because the compactor is integrated into the production process, it uses very little extra energy and adds negligibly to time and labour costs. So far, the compacting rollers have been installed in five factories throughout Europe and Australia. And, adds Andy, “the rollers pay for themselves within four months.”
Another neat idea that Andy and his engineering colleague, Steve Wilburn, have come up with goes under the deceptively simple name of ‘Blowing Bubbles’. They had noticed that some types of the powder resin ‘chips’ were easier, and quicker, to mill into particles than others, and produced less waste. This, it turned out, was related to how brittle they were. Or, to put it another way, how many ‘bubbles’ there were in the material (more bubbles; less resistance). “So the problem became, how to put bubbles there on purpose?” explains Morgan.
After various trials, they settled on the simple technique of pumping water, under pressure, into the extruder (where the resins and pigments are mixed). As the extruder works at temperatures of 110 degrees C to 130 degrees C, the water evaporates which, on cooling, leaves a series of bubbles in the material. Hey presto, it’s more brittle and grinds more easily. “It means the throughput of the mill increases, as fewer pieces of material have to go through twice to reach the right particle size,” explains Morgan. “And there’s the added benefit that the mill uses less energy as we can either grind twice as fast or go slower and use half the power.” Plus there’s less waste. So, a three-in-one solution!
We don’t just keep our ‘green’ expertise to ourselves. “We’re always willing to help customers become more efficient.,” notes van Ooijen. “They might run their ovens at too high a temperature or leave them on too long. Or we monitor their application lines and find ways of running them more efficiently. Or we might suggest changing to a low temperature cure product. In many case, it’s just common sense rather than rocket science.”