“Let’s talk plasma” with Dr Tim Johnson
By Dr Tim Johnson
Usually when I attend a conference on behalf of Tetronics I am about the average age of the other delegates. Not this time. Suddenly, I am old enough to be the father of most of the other people here, because this is a university-based conference hosted by the University of Liverpool. Yes, this is the snappily-titled International Workshop on Plasmas for Energy and Environmental Applications, or IWPEEA for short. It’s a bit of an opportunity to see a few new perspectives, and not just about my age. Even the location has taken me a little off-guard. The conference is taking place in the bustling centre of Liverpool, right opposite the glorious Victorian Lime Street Station and surrounded by one of the finest collections of civic buildings anywhere in the country. I’ve never been to this part of Liverpool before and that’s certainly opened my eyes. But most of all of course, there is the conference.
For most of the year, the contact we have as an organisation with other people interested in plasma is pretty limited, because there are very few companies worldwide who work with plasma, and even fewer who do it successfully, and all of them are our competitors. Instead, here my colleague (Yuki) and I are surrounded by enthusiastic postgrads, post docs and lecturers working with all manner of plasmas – corona, puled jet, falling film, gliding arc, packed bed dielectric, microplasma, you name it, it’s here. It is all a great reminder of the incredible variety of things that come under the heading of ‘plasma’, which in this case are all ‘non-thermal’ plasma variants. Time for a quick lesson I think.
You see there are two basic versions of plasma: low temperature and thermal. Not surprisingly, the key difference from a practical point of view is that one works in processes at temperatures below around 500°C and the other focuses typically on processes above around 1000°C. Tetronics specialises in the second of these and nearly everyone else here is dealing with the first, and that’s another thing I’m not used to. The fascinating and unexpected things that these cooler cousin plasmas can do makes our type of plasma seem rather brutal by comparison.
And yet, for all that there are some surprising overlaps. One big topic here is how to take carbon dioxide and turn it into more useful chemicals or gases using green electrical power. In some cases, these cunning little plasmas are effectively reversing the burning process by extracting oxygen and carbon monoxide from carbon dioxide, which still seems like pure alchemy to me. We ourselves have had a fair amount of interest from some large carbon dioxide generators previously about mixing it with natural gas and using cheap renewable electrical power to convert the gas back into a fuel again. Don’t worry if you didn’t quite get that first time around – I didn’t either.
The thing that struck me the most though was how the teams represented at the conference were using plasmas of various sorts throughout the process. Most of the chemical processes being discussed use a combination of plasma and a catalyst to achieve improved results. Some groups were using plasma in the production of these catalysts, whilst other groups were focusing on the use of plasma and catalyst together to make a chemical process work better than ever before. Then, as the catalyst becomes contaminated with ‘poisons’ during the process, other groups were using yet more types of plasma to clean up the catalysts to enable them to be reused. What made this especially interesting from Tetronics’ point of view is that the most common types of catalyst on show are those based around nickel on an aluminium oxide substrate. So, to this list of uses for plasma we can now add that when the catalysts finally reach their sell-by date, Tetronics thermal plasma can be used to recover the nickel from the catalyst, so that more catalysts can be made.
It all fits in with a trend we have been seeing at Tetronics recently, namely a strong upswing in interest in treating waste catalysts that contain nickel, and at considerable concentrations too. Back in the 1980’s and 1990’s, Tetronics were very successful in developing and supplying plants for recovering base metals including nickel from waste streams. Some 20 to 30 years on, are we are seeing a need for the very same technology from Tetronics? Bring it on!