24 November 2020

Customer case study around a demanding plasma vacuum application

By Armand Bergsma & Tim Righart 

In this blog, we zoom in on the impact of implementing innovative process pressure control products into a research process reactor. We see the pressure challenges from our customer DIFFER  and share how they solved their challenges through the implementation of precision pressure control products from PCS, resulting in significant improvements in the research process and research outcomes.

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Background: Plasma Solar Fuel Devices research

The DIFFER research team Plasma Solar Fuel Devices (PSFD) conducts research on plasma technologies to convert and store sustainable energy in chemicals and fuels, so called Solar Fuels. Part of this research focuses on the thermodynamics inside their plasma reactor. DIFFER has built a research reactor that uses a plasma operating in high-pressure range of 50 to 950 mbar abs, to dissociate CO2 into CO. In practice this is a CO2 plasma operating in a relatively small vacuum.

Pressure challenges for the research team

Pressure control plays a vital role here, as any pressure change typically causes changes in the plasma properties, such as the diffusion, plasma size and shape, the temperature, the flow pattern and the residence time of particles. All these changes are influencing each other and lead to different chemistry, heavily affecting the CO2 conversion process and thereby the yield of that process. Clearly, avoiding pressure changes as much as possible was an important yet challenging goal for the research team.

Plasma changes significantly with only small change in pressureIn the animation we see the sensitivity of the plasma for pressure changes, recorded with two different cameras. As the pressure increases we see the plasma become brighter, thinner and longer.

The system’s reactor operates at subatmospheric pressure to generate the plasma, requiring a very high range of valve flow coefficients (Cv) to be set with high precision. It was impossible to achieve the desired precision and stability of the plasma operational pressure in the initial set-up, because of the combination of a vacuum pump and a manually piloted high-end butterfly valve.  Furthermore, the system was restricting the research as it was not possible to investigate the plasma at higher pressures, resulting in negative impact on the quality and predictability/reliability of the research data.

A different approach was needed to control the vacuum in the research set-up to enable the researchers to focus on the actual subject of their research: understanding the plasma behavior at a desired pressure level, without pressure control issues getting in the way.

Pressure Control Solutions

The researchers concluded that more stable, accurate and frictionless pressure control would be an important success factor for their research project. While being aware that they operated under quite unusual process conditions, they aimed for proven technology and secure performance of their research set-up.

When DIFFER researcher Tim Righart first learned about Equilibar ® and Pressure Control Solutions, he could hardly believe that this dome-loaded back pressure technology could work also for their application. After all, they operated a very demanding set-up, using a medium as complex as plasma (with its inevitable occurrence of pollution and leakage), and that operates under very high temperatures, which might damage the diaphragm. Without much hope or confidence, the team contacted PCS.

Tim remembers how the team had to overcome some reluctance to try a radically different approach to pressure control:

“We didn’t know any better than to constantly tweak the manual pilot controller until we got it right. Pressure changes in our plasma system were so regular, that we simply couldn’t imagine a product that could take this away. It was only for the knowledge and experience demonstrated by Armand Bergsma, that we were willing to give this a try.”

Project outcome: precision process control turned into the solution

As mentioned, accurate and stable pressure control across longer operating times and complex process conditions was a key requirement to overcome the challenges that the researchers were facing. This would help to understand precisely what is going on in the research system and investigate the properties of the plasma at the set pressure level. PCS recommended to use an Equilibar vacuum regulator (EVR GSD8 Series) to be built into the research set-up.

Despite their initial reserves, the researchers were amazed of the effects of the instrument on their research process:

  • Ease of use improved enormously
  • Full vacuum range could now be operated; precision up to 3mbar abs was achieved:
    • Meaning much better level of accuracy at higher pressures

Differ plasma reactor including PCS precision pressure control productsAlthough the customer already was quite satisfied with this improvement, the level of accuracy for lower pressures could still be optimized. PCS offered as a next step to replace the pilot controller with a different model of our own design, the so-called ERC Series. The ERC integrated with the research system seamlessly and allowed for direct operation, unlike the previously used butterfly valve. It provided the customer with “plug and play” functionality for optimal ease-of-use and resulted in unparalleled precision.

Process optimization & customer satisfaction

Tim describes that the improvement achieved in the process conditions of the system have been significant for the whole team, minimizing downtime or unpredictable research results:

“Even colleagues who hadn’t been involved directly in the pressure control discussions came down to have a look, as everybody in the group experienced how much better our system was now our control problems were solved! … Pressure in the system is now just another setpoint you pick and don’t have to worry about anymore.”

Want to know more?

View the whole customer case study: PCS Case Study – Better Process Control for Better Process Outcomes.

Are you interested in finetuning your application also? Do you run a system that could benefit from more accurate, stable and predictable process control? Please contact us or visit our products pages for more information.

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