Steam Activation of Oil Shale to Enhance the Porosity of Produced Semicoke

ABSTRACT

Finding a recycling method for waste materials is attracting increasing attention. In Estonia, semicoke from the shale oil industry is a material that can be used for adsorbent production. For this application, it is important to characterize the surface properties and enhance the porosity. In this study, different pyrolysis temperatures (from 500 to 800 °C) and steam activation parameters were applied to determine their influences on the surface properties of oil shale semicoke. It was found that pyrolysis at 700°C resulted in the highest Brunauer – Emmett–Teller surface area of 59 m²/g. To investigate the effect of activation, up to 70% vol of steam was added to the pyrolysis environment for different durations (15–60 min). Although the effect was relatively small, shorter activation times and less steam resulted in larger surface areas. The highest surface areas (68–69 m²/g) were achieved when activation was carried out for 15 to 30 min with 25–50% vol of steam in the environment after pyrolysis at 700°C. It can be concluded that longer activation and more steam causes widening and collapsing of some pore structures, resulting in a decrease in the surface area and total pore volume.

KEYWORDS:

• Oil shale
• semicoke
• pyrolysis
• steam activation
• surface area

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This research was financed by the Estonian Research Council Grant (PSG266)

Notes on contributors

Heliis Pikkor

Heliis Pikkor is a PhD student at Department of Energy Technology at Tallinn University of Technology. Her research topics are mainly related to the oil shale industry, especially studying the porous characteristics of solid wastes produced in the industry and finding ways to improve their properties.

Heidi Lees

Heidi Lees is a researcher at Department of Energy Technology at Tallinn University of Technology. She finished her PhD studies at Department of Chemistry and Biotechnology at Tallinn University of Technology. She has specialized in analytical chemistry. Now her research area is connected to porosity as well as chromatographic methods.

Alar Konist

Alar Konist is a professor at Department of Energy Technology at Tallinn University of Technology. He is an expert in biomass and oil shale combustion technologies and in environmental protection. He also studies oil shale pyrolysis and gasification kinetics and is an expert in oxy-fuel combustion.

Oliver Järvik

Oliver Järvik is a senior researcher at Department of Energy Technology at Tallinn University of Technology. He gained his PhD degree in the field of environmental engineering and has a long experience in thermal processing and characterisation of oil shale.

Birgit Maaten

Birgit Maaten is a senior researcher at Department of Energy Technology at Tallinn University of Technology. She has a long experience with compositional and kinetic analysis of oil shale pyrolysis and in experimental analysis of combustion characteristics of oil shale under different atmospheres.