Improved low-temperature activity for marine selective catalytic reduction systems
Journal article, 2016

Through the international work carried out recently by International Maritime Organization Marine Environment Protection Committee, the need for improved selective catalytic reduction systems for marine applications at low and transient temperatures has been acknowledged. It is of importance to improve the low-temperature activity to achieve compliance with the upcoming stricter International Maritime Organization NOX regulation (Tier III, 80% reduction) for ships. This study therefore investigates the possibilities to improve the low-temperature activity for a commercial vanadium-based urea-selective catalytic reduction catalyst for marine applications. By altering the NO2/NOX ratio, the reaction proceeds in the fast selective catalytic reduction reaction regime, which is especially beneficial at low and transient temperatures and in combination with SO2 and H2O. For both steady-state and transient modes, it is suggested that an improved low-temperature activity for the marine selective catalytic reduction system can be achieved by increasing the NO2/NOX ratio to 50%, whereby utilizing the fast selective catalytic reduction reaction scheme. The fast selective catalytic reduction can significantly improve the NOX reduction already at 250 degrees C in the presence of water or sulfur. The fast selective catalytic reduction will, however, require an increased NO2 fraction in the exhaust gases, preferably 50%, which may be achieved by placing an oxidation catalyst upstream of the selective catalytic reduction. The use of an oxidation catalyst upstream of the selective catalytic reduction can offer a possibility to achieve International Maritime Organization Tier III compliance at low and transient temperatures, but to avoid formation of ammonium nitrates and possible ammonium sulfates, temperatures should be kept above 250 degrees C in combination with marine fuels with a maximum of 0.10 wt% S.

sulfur dioxide

NOX reduction

water

marine applications

Urea-selective catalytic reduction catalyst

Author

Mathias Magnusson

Chalmers, Shipping and Marine Technology, Maritime Environmental Sciences

Erik Fridell

Chalmers, Shipping and Marine Technology, Maritime Environmental Sciences

Hanna Härelind

Chalmers, Chemistry and Chemical Engineering, Applied Chemistry, Applied Surface Chemistry

Competence Centre for Catalysis (KCK)

Proceedings of the Institution of Mechanical Engineers Part M: Journal of Engineering for the Maritime Environment

1475-0902 (ISSN)

Vol. 230 1 126-135

Driving Forces

Sustainable development

Areas of Advance

Transport

Materials Science

Subject Categories

Microbiology

Organic Chemistry

DOI

10.1177/1475090214536546

More information

Created

10/8/2017