Minerals synthesised from fly ash to adsorb carbon dioxide. This is the goal of the Central Mining Institute in Katowice and an international team of scientists.

THE OBJECTIVE of the project ‘COALBYPRO:Innovative management of COAL BY-PROducts leading also to CO2 emissions reduction’ is to develop methods of using fly ashes – by-products of coal combustion – to synthesise zeolites (minerals that can capture CO2). The project is funded under the EU’s Research Fund for Coal and Steel. It is carried out by an international research consortium led by the Centre for Research and Technology Hellas (CERTH) from Greece. Other participants of the project are representatives of three research centres in Czechia and one in Germany.

Zeolites are a unique group of minerals also called ‘molecular sieves’: their structure forms a network of very fine empty cavities. Thanks to them, zeolites can capture various substances just as a sponge absorbs water.

Depending on the diameter of the pores, zeolites adsorb greater or smaller volumes of various particles. Carbon dioxide is captured in the pores more easily than many other gases, with the best effects achieved in the case of zeolites X. This type of the mineral does not occur naturally, but it can be synthesised. As a result, zeolites X can be designed optimally so that they adsorb as much CO2 as possible.

Exhaust Gases Purified with Fly Ash

The researchers’ idea consists in capturing CO2 in fly ashes and in fly ash-derived zeolites. The benefit is twofold, because the procedure allows to capture the unwanted gas and make use of industrial waste at the same time. ‘The most frequently applied method of zeolite synthesis from coal fly ash is hydrothermal treatment. In the case of fly ashes from the combustion of hard coal, the scientists applied hydrothermal synthesis, and in the case of lignite, the ashes were subjected to sintering with sodium hydroxide prior to hydrothermal synthesis. Optimising the parameters (temperature, time) of the process of zeolite (sorbent) synthesis from fly ashes enabled us to reduce the costs of their production,’ explains Prof. Barbara Białecka from the Central Mining Institute, one of the project participants. In addition, the scientists have developed a method to reuse some of the substances needed to create the sorbent several times.

One Step Away from Entering the Market

The researchers have synthesised various types of zeolites from fly ash, including zeolites X. They are developing the principles of a technology of CO2 sorption on an industrial scale. The relevant patent application is pending. Until now, studies of zeolites’ CO2 sorption have been carried out on a laboratory scale. Tests on a semi-technical scale on the PSEA installation located in Czechia are supposed to confirm the effectiveness of the invention. The knowledge on the application of zeolites as gas (including CO2) sorbents is not very common. That is why one of the project’s objectives is to promote its results in order to attract the interest of potential industrial partners. Apart from zeolites X, the scientists have obtained new structures similar to zeolites, which may be used in radioactive waste treatment and in the construction industry.

The Central Mining Institute



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