New theories about dense gases and liquids can help capture carbon

The transport of dense gases and liquids is becoming increasingly relevant in relation to carbon capture. Research published in the Journal of Chemical Physics can help you understand more about how to do this most efficiently.

Gas must be compressed before transporting over long distances. This can be done by increasing the pressure of the gas or converting it to a liquid. For this to occur safely and efficiently, you need to understand as much as possible how the gas works before and during transportation.

High density gases are affected by changes in pressure and temperature, and there has been no fundamental theory of various high density gases and liquids up until now.

“We are developing a theory that explains the transport properties of dense gases and liquids,” the doctorate said. Vegard Gjeldvik Jervell, a researcher at NTNU’s Thermodynamics Group and Porelab Center of Excellence.

His supervisors are Professor Øivind Wilhelmsen and Professor Morten Hammer of the Thermodynamics Group at NTNU’s Ministry of Chemistry, both of whom are affiliated with Porelab.

In fact, it is somewhat surprising that this research community has made such important advances in explaining the transport properties of dense gases and liquids. This task is extremely difficult. This is because knowledge of how molecules interact under a wide range of conditions is required.

“For the past 50 years, experts in this field have argued that it is impossible to develop liquid collision theory,” Wilhelmsen said.

Certainly not, but why is it so beneficial to have a common theory explaining how gas behaves during transport?

“The foundations of existing methods rely on challenging and expensive experiments,” Jervell explained.

The theory becomes even more important when you decide to start capturing CO2 from many different sources. This is because it involves large-scale transportation.

Inaccurate model

Wilhelmsen was recently contacted by a gas carrier, leading to a “Aha” moment.

“The company wanted to understand how the gas behaved during transit. The software they paid a lot was not that accurate, especially when gas mixing was involved,” Wilhelmsen explained.

New theories reduce the need for expensive experimental work.

Wilhelmsen realized that many of the answers the company was looking for could be provided by thermodynamic groups. This meant that the research group could work in a much easier way than the company could achieve on its own.

“In some cases, models even provide more accurate answers than they can achieve through experiments,” Hammer said.

Of course, models do not completely replace labs, but researchers know which fields the models excel in and certainly understand where additional experiments are needed.

“This theory is very accurate for tight mixtures of gases, an area where other models struggle, but at this point it is still not accurate enough for liquids at low temperatures,” Hammer explained.

Jervell took a thorough approach and investigated many of the tight mixtures of gas.

“We built the theory from scratch. We started with molecular interactions and developed the theory so that we could measure properties in the lab,” Jervell said.

New theories can provide more insight into the properties of various high density gases.

A versatile theory

“Now we can more reliably predict what will happen under a variety of conditions. Theories are built on a solid foundation, so we can provide accurate answers even in areas where no experiments are being conducted,” Jervell said.

This is especially important when it comes to gas mixing, as it is simply too time consuming to experiment with all possible combinations. This model can already provide insight into the viscosity of gases under a variety of conditions, and also provides information on their thermal conductivity and diffusion rate.

“It’s a truly versatile theory,” concluded Wilhelmsen.