Exclusive Pilkington interview

As a Lead Technologist at Pilkington UK, part of NSG Group, Graham Unwin has applied his formidable skills in developing and applying numerical models to help optimise glass forming and hone the design of electrically-heated/boosted furnaces. Mr Unwin spoke exclusively to Glass Worldwide to discuss the importance of his role in relation to NSG Group’s current goals, and to reflect on receiving the 9th GS Modelling Award from Czech glass melting specialist Glass Service this summer. The full version of this article appears in the Sept/Oct 2023 issue that has been mailed globally and is also now available free of charge in the digital archive*.

Exclusive Pilkington interview

GW: What first attracted you to a career in the glass industry and has it lived up to your expectations?

I was always interested in manufacturing and especially how mathematical modelling could contribute to understanding and improving it. The glass industry offered a wide range of interesting challenges where modelling could make a real contribution.

In 1987 I joined Pilkington UK, now part of NSG Group, straight after my degree in Mathematics from Liverpool University. My first role was as a Technologist in the Applied Mathematics team within the Science Group in R&D. This involved writing and using simulation software to model the flows and temperatures of glass and tin in a float bath. I was also working on electric melting models for both boosting and cold top. In 1994 I moved into the Furnace Modelling team as a Senior Research Scientist. In this role I was using and modifying 3D Computational Fluid Dynamics (CFD) programs to model the glass flows and temperatures within the furnace. This was used for trouble shooting, new product development and assessing design changes. In 1997 the modelling teams were combined. Since that time, I have been involved with updating and using the various in-house modelling codes as well as using commercial simulation packages. I have also carried out physical model studies where a scale model is built out of Perspex and a model fluid chosen to give the required flow characteristics. It is particularly well suited to modelling glass stirring and free surface flows. In 2015 I became a Lead Technologist.

After over 35 years I still find the work interesting and challenging so it has lived up to my expectations.

GW: How has the flat glass industry changed during your time working in it?

In many ways the industry has changed massively but a float line is still very recognisable from what it looked like when I started. The biggest change is probably the introduction of on-line coated products. These products now deliver a wide range of properties from low emissivity, antimicrobial and solar control through to self-cleaning glass. The other major change is the increase in automation on a line with less direct manual intervention now required. Alongside this, the amount and quality of data collected has increased hugely. Through the last 35 years the flat glass industry has constantly changed. These changes have often been small and incremental but over the years add up to a very different manufacturing industry now, compared to the late 1980s.

GW: Are there any stand-out achievements, either as an individual or as a team, that you are particularly proud of?

All the achievements have come as part of a team – most often multidisciplinary teams. I have been very fortunate to work with some incredibly talented people throughout my career. This includes many colleagues in NSG Group, people in academia (especially at Oxford, Cambridge and Liverpool Universities) and also people in the wider glass industry.

On the modelling side, work carried out with colleagues to significantly improve our tin flow modelling was particularly pleasing. It allowed us to model float baths with a greatly improved accuracy giving much better agreement between the model and plant data.

Other projects of note include making high iron (>2% Fe2O3) glasses for the first time as it was the model work that gave the confidence to try it on plant. Projects where furnaces have been rebuilt to a make a completely different product mix are always interesting. Models have been used to assess a wide range of design options and guide the final design. To then see the furnace start up and run successfully is always pleasing.

GW: What currently are the main priorities and development goals for your department within NSG Group?

The main goals all revolve around sustainability and especially decarbonisation. We need to ensure we have the right modelling tools in place to simulate things like increased use of electric melting, hydrogen and other low-carbon fuel firing and using low carbon raw materials.

GW: In general, how relevant is NSG Group’s investment into sustainability to your job and how are efforts co-ordinated within the wider group?

Sustainability is very relevant to just about everything we are currently working on. NSG Group has challenging targets to meet by 2030 and there are many R&D projects geared to achieving these. Model work is vital in testing ideas and showing how things will work if they are implemented. It is also important in highlighting possible drawbacks of a proposal.

GW: And what importance is put on R&D?

R&D is leading many sustainability projects in a range of areas, but it is also supporting projects being led by other parts of the group. The whole company has a focus on sustainability with R&D a vital part of the effort.

GW: What are your thoughts on the challenge to create a CO2-neutral flat glass industry? By what means can this be achieved by NSG Group and in what timeframe?

Creating a CO2-neutral flat glass industry is going to be incredibly challenging, but it is a challenge the industry must meet. With float furnaces typically getting rebuilt only every 15 years, we need to consider at every repair [that] all the required provision is included in the design to introduce CO2-reducing technologies. We already have some tools available to help, like electric boosting, but their use will need to be significantly expanded. Alongside this there is a whole range of technologies which need developing and testing. It is not yet clear how furnace designs will change in the coming years, but it is certain that they will change and modelling will be important in guiding that.

GW: What alternative glass melting technologies are you exploring to reduce the company’s carbon footprint and what are your preferred alternatives for the future?

In the short term, increased use of electric boost and low-carbon fuel firing will be important. Alongside this we are investigating things like carbon capture, low-carbon raw materials and increased use of cullet. In the longer term, I think it is likely that all-electric melters will be required. The huge challenge for the flat glass industry is how to build them so they deliver the high throughputs, good quality and long campaign lengths currently achieved.

GW: What did it mean to you personally to be recognised as the recipient of the prestigious 9th GS Modelling Award?

The GS award came as a complete surprise and honour to me. This is highlighted when you look at the list of previous recipients of the award, which includes many people I have known and greatly respected for their contribution to furnace modelling over many years.

GW: How useful to your business are the GS International Seminars on Furnace Design – Operation and Process Simulation in Velke Karlovice, Czech Republic [see the full Sept/Oct issue for a review of the 16th International Seminar on Furnace Design]?

The GS seminar is an important event. It is really the only event dedicated to furnace modelling and gives an important opportunity to meet other modellers from across the industry and hear their views on important developments and challenges.

GW: How do good business relationships with leading technology suppliers such as Glass Service contribute to the success of your role?

Good relationships with the likes of Glass Service are important. Whereas most of my work is concentrated on flat glass, they see the whole glass industry from a wider perspective. For example, developments they make to their simulation software can point to new ways of thinking we should be considering.

GW: How important do you consider the use of Computational Fluid Dynamics to be to the successful design and operation of glass melting furnaces?

This is one of the biggest changes I have seen during my career. CFD is now vital for the successful design and operation of a furnace. It offers a tool to test a wide range of ideas out before implementing them on a furnace. We would not now make a design change without first modelling it. Similarly, CFD gives an understanding of what is happening to the glass within the furnace and quantifies the impact of changing the input settings like fuel or waist pipe depth.

It was CFD combustion modelling by one of my colleagues, Mike Haden, that gave us the confidence to run the ‘world first’ hydrogen firing trials at the Pilkington UK float furnace in 2021. The knowledge gained in modelling syngas many years ago was vital to understanding the effects of the low luminosity flame that you get from hydrogen.

With the current opportunities around sustainability and especially decarbonisation, there is a clear focus on modelling throughout the industry. There are lots of possible scenarios to consider and modelling, especially using CFD, makes a very important contribution to this. The pressure to constantly develop the models and improve how we use them is there, so I see a bright future for modelling within the glass industry

GW: What have been the main advancements in CFD during your time in the industry and how important will modelling be to furnaces of the future?

In the early days, CFD was a fast-developing tool which was greatly helped by rapid increases in available computer power. The CFD programs we now use have greatly increased capability in just about all areas, including things like meshing, turbulence models, time-dependent calculations through to the post processing. The output from the models used to be a large file of numbers that were interpreted by hand. We are now able to quickly produce all sorts of plots showing flows, temperatures and bubble tracks as well as the key numbers from a simulation. CFD is now a fairly mature technology. Over the years we have learned how to model a particular situation, how to interpret the results and present them to people who are not modellers. We now understand the limitations of the modelling – knowing what it is good at, and equally importantly, where it is less reliable.

GW: Are there examples of successful CFD projects undertaken and delivered within NSG Group/Pilkington UK that you would like to highlight?

CFD has played an important role in many projects. It was fundamental in understanding the effect of using electric boost when that was first introduced and successfully operated by Pilkington UK in the 1990s. It is again being widely used as we look to use higher levels of boost for decarbonisation. CFD was also important when we were designing furnaces to make low-iron glass for the solar market. The optimum design for such a furnace has many differences when compared to a tank designed to make clear or tinted glasses. Several such furnaces have now been designed, built and successfully operated.

GW: How influential do you expect initiatives such as Glass Futures to be in creating a long-term future for Europe’s flat glass industry?

Glass Futures offers an opportunity to test ideas on an intermediate scale. Without this, you need to go directly from lab scale tests and modelling to a full-size float line. Given the obvious reluctance to take any risk with a float line, having the opportunity to try things out on a small glass production line is important. We are collaborating with Glass Futures, and other partners in the wider glass industry, on a number of projects to help accelerate and deliver solutions to our common challenges faster and more effectively.

GW: How important is it for you and members of your team to serve on relevant ICG committees and what benefits do you derive from these initiatives?

We have served on numerous ICG technical committees over many years and have been involved in TC21 (furnace design and operation) for over 30 years. The committees offer a good way of keeping up to date with technical developments in the industry. An important aspect is meeting people working in similar technologies across the whole of the glass industry.

GW: What activities does the TC21 undertake and how have your contributed over the years?

TC21 is there to improve furnace modelling techniques across the industry. Over the years it has organised ‘round robin’ simulations of different furnaces where each contributor used their own modelling approach. All the results were then discussed and reported. In the early days when CFD was developing quickly, these offered important insights to modelling techniques and the different models available. The challenge in more recent times, certainly from the glass manufacturers, has been finding the time to contribute to the round robins when there are so many other time pressures. However, TC21 still provides interesting discussions on current modelling issues and an opportunity to meet modellers from other parts of the industry.

GW: What are your hopes and expectations for glass melting installations in the next 20 years in terms of campaign life, throughput, energy, emissions and cost?

I would be surprised if campaign lengths continue to increase in the coming years. Given the pressures to rapidly introduce new technologies, I think it is likely that furnaces will be built to have shorter campaigns going forward. If we do go to all-electric melters, it is probably inevitable that we will have to get used shorter campaigns. The high throughputs we have on float lines do offer good thermal efficiency, so I think there is a strong desire to maintain them. Whether this is possible will depend on many things including the fuels we will be using in the future to melt the glass.

I think it is clear that in 20 years’ time the industry will not be operating furnaces which are 100% gas or oil-fired. It is obviously a lot more difficult to predict what the mix of fuels will be but glass making is an energy-intensive industry and will remain so.

The other emissions from glass making – apart from CO2 – have reduced significantly over the last 30 years with Pollution Control Plants to clean the waste gases now widespread. I would expect new technologies to develop which will further reduce the emissions of NOx, SOx and particulates. The cost of glass will be strongly influenced by the cost of fuel, so again, it is not clear how this will change in future. Many of the costs in producing glass come back to the energy required both directly and in processing the raw materials. As an industry we must strive to become as energy-efficient as possible but will not get away from input fuel costs.

When I started work, CFD was in its infancy; Digitisation (Machine Learning, AI, digital twins, etc.) is now at that stage. We are still working out how best to use it; in which areas it can make a useful contribution and where it is less well suited. Over the coming years I am sure these techniques will become as widespread and useful as CFD in helping us to design, build and operate furnaces most efficiently.


Images: Glass Service Vice Presidents Erik Muijsenberg and Petr Chmelař with GS Modelling Award recipients Aaron Huber (2017), Bruno Purnode (2019) and Graham Unwin (2023) + the NSG European Technical Centre at Lathom, UK.


Further Information: 

Pilkington Group Limited (part of the NSG Group), Lathom, Lancashire, UK
tel: +44 1695 50000
web: www.pilkington.com

* The full version of this article appears in the bumper Sept/Oct issue that has been mailed globally. The digital version of this issue can also currently be read free of charge in its entirety in the Digital Archive (sponsored by FIC) of over 65 issues of Glass Worldwide at https://www.glassworldwide.co.uk/Digital-Issues. To receive the paper copy, all future issues and a free copy of the Who’s Who / Annual Review 2023-24 yearbook, subscribe now at https://www.glassworldwide.co.uk/subscription-choice