1) The document discusses improving selective catalytic reduction (SCR) systems for reducing nitrogen oxide (NOx) emissions from marine applications. 2) SCR is identified as one of the most effective NOx abatement technologies available, but little research has been conducted on marine SCR systems. 3) The thesis investigated parameters and aspects that need consideration for installing and operating marine urea-SCR systems with high NOx reduction efficiency, including catalytic reactor experiments and the human-machine aspects of practical SCR installation experiences.

1. NOx Abatement Technique for Marine Applications
Improved SCR Systems
MATHIAS MAGNUSSON
Department of Shipping and Marine Technology
Division of Sustainable Ship Propulsion
Chalmers University of Technology
Abstract
Growing awareness of the environmental implications of emissions of nitrogen oxides
(NOX), such as eutrophication and acidification on land and at sea, has contributed to
the development of more stringent international NOx legislations within the
framework of IMO, with the most stringent legislation, Tier III, representing a NOx
reduction of approximately 80% compared with today’s engines. Several NOx
abatement technologies are available on the market, the most effective of which may
be Selective Catalytic Reduction (SCR). Little research has been conducted into
marine SCR however. The NOx emissions from the international sea transport in the
EU are projected to increase by 67% between 2000 and 2020, thereby exceeding the
total of all land-based sources in the EU-25 by 2020 unless further action is taken. It
has also been suggested that approximately 15% of all anthropogenic NOx emissions
originates from vessels, and, combined with this, about 70% of all emissions take place
less than 400 km from land, which may indicate that NOx emissions from vessels are
important. Hence, the purpose of this thesis was to investigate and present certain
parameters and aspects that may need to be considered in the pursuit of installing and
successfully operating a urea-SCR system for marine applications with high overall
NOx reduction efficiency. The thesis therefore considers two tracks: catalytic flow
reactor experiments and human-machine aspects of practical experiences of SCR
installations. As a final conclusion of this thesis, it may be argued that SCR is a highly
efficient NOx abatement technology. There are some risks of different types of
deactivation, however, of which the specific deactivation by the formation of ammonia
sulfates may, to a certain extent, be avoided by careful design and operation of SCR,
e.g. monitoring exhaust gas temperature, exhaust gas flow and sulfur concentrations.
The overall efficiency of the marine SCR systems may never reach its full potential,
however, if the crew members and managers are not provided with appropriate and
sufficient knowledge of how the system works and what the prerequisites are to
achieve successful SCR operation, i.e. the investigation of technical issues is a necessity
but not necessarily sufficient for the safe, efficient and sustainable operation of SCR.
Suggestions for further work may include flow reactor experiments to investigate the
potential effects of different types of marine urea and marine fuels.
Keywords: urea-SCR catalyst, NOx reduction, Marine applications, Sulfur dioxide,
Water, Human-Machine system, Human element