As the urgency of fight against climate change is growing, so does the price of emission allowances. It may soon pay off for industrial companies to invest in technologies that help capture carbon dioxide from the flue gases, instead of paying for allowances that authorize them to emit greenhouse gases into the atmosphere. One of the methods to extract CO2 from the flue gases is spray columns with spray nozzles called atomizers. Experts of the Faculty of Mechanical Engineering of Brno University of Technology are working hard on this development.

The word “atomizer” sounds like a complex concept, but in fact we are surrounded by it in our everyday lives. Every day, we use devices that can spray liquid into space – in medicine, drugstores, household cleaning or flower care. "The purpose of an atomizer is to transform a liquid into small droplets that are then more suitable for the application than the liquid as a whole. For example, they have a significantly larger total area, even a thousand or millions of times larger than a liquid in compact form. Thanks to this characteristic, the droplets can soak up or evaporate more quickly, they can be applied in an easier way, or may bind various pollutants," says Jan Jedelský, head of the Spray Laboratory of the Faculty of Mechanical Engineering of the Brno University of Technology, describing the general principle.

Significantly more sophisticated atomizers could help fight greenhouse gases and other pollutants. "Spray cleaning of exhaust gases using nozzles or atomizers has already been developed from the chemical and process point of view, but no one has considered which type of nozzle is the most suitable, how to optimize its parameters and maximize the effect of the resulting aerosol. We decided to use our know-how and in 2020 we embarked on the development of a new nozzle that should be as efficient as possible and therefore energy-saving," says Jedelský.

A CO2 spray capture device can be imagined as a chamber into which polluted gas, typically flue gas, for example generated by a coal or gas power plant, comes from below, and where a liquid is sprayed from above. This liquid then which scavenges pollutants, specifically carbon dioxide, from the flue gas. The CO2 is then removed from the liquid by further processes and – ideally in its original form – returns to the system where it circulates.

Spray capture of CO2 from flue gases is not yet used on an industrial scale. However, rising prices of emission allowances make the extraction of greenhouse gases a topic that will soon become interesting even for large companies. Although the prices of emission allowances fell significantly during March this year, they had been rising steadily over the past eight years, up to about thirty times their price in 2013. In February this year, a ton of CO2 emitted traded just under one hundred euros. "Thanks to this shift, the motivation to deploy similar technologies is growing. And it is therefore important that they work as efficiently and cheaply as possible and that their operation also makes sense in terms of energy consumption," Jedelský explains.

The weak point of the process is the question of what to do with the "collected" carbon dioxide next. Scientists around the world are already working on this and Jan Jedelský believes that they will find a solution, whether it is the storage of carbon dioxide in underground cavities or perhaps pushing it into the seabed. "It will only be good if we learn to capture carbon dioxide. It has been stored underground in fossil fuels for a long time, and we have to compensate somehow for the fact that we are releasing it massively today. If a lot is invested in this area, we as humanity will be able to deploy these technologies in a few years," Jedelský believes.

With a team of colleagues of the Department of Thermomechanics and Environmental Engineering, he is heading towards a general design of an improved atomizer, which is to be ready at the end of this year. "We will know how the system should work, but we will not be able to offer it to companies as a ready-made solution, because for each application it will be necessary to customize the atomizer individually. However, our database and proposed solution will be the first step in optimizing this equipment for a specific operation. The results of our research will be publicly available," concludes Jedelský.