TPU Proposed To Capture Carbon Dioxide In Flue-Gas Emission Using Gas Hydrates

TPU researchers have developed and experimentally tested a technology for capturing carbon dioxide from real flue gases using gas hydrates, gas compounds in an aqueous shell that, depending on their composition, are called "combustible ice." In the hydrate structure, water molecules form a kind of "cell" that holds gas molecules inside. Studies have shown that this method makes it possible to isolate up to 98% of carbon dioxide from flue gases and use it further in industry.

The research was supported by the federal program of the Ministry of Education and Science of the Russian Federation "Priority 2030" of the national project "Youth and Children". The results of the research have been published in Journal of Environmental Chemical Engineering (Q1, IF: 7,5).

Modern industrial enterprises use various carbon dioxide capture technologies. Cryogenic distillation, physical and chemical adsorption are among the most common. However, these methods require significant energy consumption, expensive reagents, and often lead to equipment corrosion.

Researchers at Tomsk Polytechnic University have proposed a technology that allows "catching" carbon dioxide in a mixture of flue gases. To do this, they proposed using gas hydrates, compounds of gas in an aqueous shell. Due to its crystal lattice, the hydrate "locks" carbon dioxide inside itself, leaving other gases outside. This hydrate can then be regasified to produce concentrated CO_₂ suitable for further use or storage.

Flue gases contain a mixture of gases of oxygen, nitrogen oxide, sulfur, carbon monoxide, methane and other impurities. They can not only be filtered and disposed of, but also used effectively. Our proposed technology can isolate carbon dioxide from flue gases as effectively, cheaply and energy-efficiently as possible when burning traditional fuels. Since we use water instead of expensive reagents. According to our estimates, this approach requires about half as much energy per unit mass of CO_₂ as similar technologies, which consequently reduces capturing cost compared to traditional absorption.,— notes Nikita Shlegel, one of the authors of the study, head of the Laboratory of Gas Hydrates at the TPU Research School of High-Energy Process Physics.

The TPU researchers experimentally tested the developed technology. To do this, they received a smoke mixture from burning three common types of fuels — coal, fuel oil and natural gas. The researchers fed it into the reactor with water to form hydrate. After hydrate formation, the TPU researchers removed the unreacted gas, and a portion of the flue mixture was fed back into the reactor. This made it possible to fill the hydrate grid with gas as much as possible.

Analysis of hydrates obtained from smoke mixtures showed that they can capture carbon dioxide with an efficiency of over 92%. Separately, for flue emissions of natural gas, this figure reached 98.2%, for fuel oil — 92.7%, for coal — 92%.

Separately, the TPU researchers analyzed the composition of the hydrates obtained. The results showed that hydrates from coal combustion flue emissions contain 92.2% carbon dioxide, hydrates from natural gas combustion flue emissions contain 95.6% carbon dioxide, and those from fuel oil combustion flue emissions contain 92.6% carbon dioxide. Natural gas emissions produced the purest hydrate, since it did not contain sulfur oxide. The hydrates from coal and fuel oil had to be additionally "cleaned".

Based on the results obtained, the TPU researchers derived mathematical equations that make it possible to calculate the composition of the gas mixture, the reactor volume, the volume of the supplied flue mixture and the temperature, as well as predict the time required to isolate CO ₂ from flue gases in industrial conditions. This will allow to scale up the technology in the future.

Researchers from the TPU School of Energy and Power Engineering and the Research School of High-Energy Process Physics participated in the study.