In this week’s In-depth industry insight feature, Ship Efficiency Review examines the evolution of selective catalytic reduction technology as a method for reducing Nitrogen Oxides (NOx) emissions.
The Selective Catalytic Reduction (SCR) of Nitrogen Oxides (NOx) using ammonia as a reducing agent was originally patented by the Engelhard Corporation in 1957.
During SCR a catalyst promotes the reaction between NOx and a reducing agent at the relatively low temperatures of an exhaust stream. It is a process that produces harmless nitrogen and water.
It was not until the late 1970s, that the first large-scale onshore application of SCR technology took place. However, from initial installations in stationary onshore industries, its application spread to automotives and locomotives and on to the marine sector.
The first commercial installation of a SCR system onboard a ship did not take place until 1989 onboard a 37,000 DWT deep-sea bulk carrier, the Pacific Princess, following the pioneering of marine SCR technology by Haldor-Topsøe and MAN B&W. It was in 1997 a marine SCR was installed for the first time on a ferry, the M/S Stena Jutlandica on all main and auxiliary engines.
The SCR process, during which a catalyst promotes the reaction between NOx and a reducing agent at the relatively low temperatures of an exhaust stream, has since gained ground to become an established technology in the industry. This is thanks to the catalyst effect that stricter controls over ship NOx emissions by the International Maritime Organization (IMO), regionally, and at the port level are having.
When examining the overall uptake of SCR systems in the industry, it is obvious that certain ship types have seen much greater uptake. Over the past few years SCR systems have been predominantly installed on RoPax, Ro-Ro, ferries, and cruise ships. This is a bi-product of these types of vessels spending large amounts, or all of their time in NOx Emission Control Areas (ECAs) and in regional NOx enforcement zones.
DNV GL’s recent “Shipping 2020” report forecasted that at least 30–40 % of newbuildings will be fitted with exhaust gas recirculation (EGR) or SCR systems by 2016 to meet emission requirements. The Classification society agrees that the 80 % reduction requirement in ECAs of Tier 3 regulation is undoubtedly the main motivator.
Regional regulations also have a large part to play in marine SCR system uptake. Take the Norwegian NOx tax and NOx fund as a leading example of how a regional regulation can influence technology uptake. Introduced in 2007, the NOx tax aims to reduce emissions by enforcing a tax of ~ US $2.00/kg of NOx emitted from Norwegian registered ships within 250 nautical miles (nm) from Norway’s coast. This also applies to all ships under foreign flag operating in Norway’s territorial waters (i.e. within 12 nm of the Norwegian base line). The annual income of the NOx Fund is used as financial support to enterprises that have engaged in abatement measures to reduce their NOx emissions.
Port incentive schemes are also having an impact on uptake. For example, the Port of Los Angeles awards ships with installed SCR systems eligible for an incentive grant on a per call basis.
To date, more than 500 marine SCR systems have been installed and SCR technology has been successfully installed across a wide range of ships types, engine types and operated with different fuel types. This figure will only increase as the industry remains firmly in the spotlight over its emissions and environmental impact.
