The International Council on Clean Transportation (ICCT) has recenlty issued a Working Paper based on a survey of technical literature and industry reports which assess equipment costs, environmental side effects, urea and catalyst availability and disposal, and the overall system costs of SCR in the marine sector
ICCT paper investigates the current status of selective catalytic reduction (SCR), a technology that is key to meeting Tier III requirements. Challenges and costs of the technology, including applicability to various engine and vessel types, potential environmental side effects, urea and catalyst availability and disposal, and anticipated system costs, are discussed. Based on this evaluation of technological capabilities and history of successful application of SCR technology to maritime vessels, no substantial equipment, supply chain, or cost barriers exist that would necessitate the delay of IMO’s Tier III requirements.
| In 2008 the Marine Environmental Protection Committee (MEPC) of the International Maritime Organization (IMO) agreed upon progressively stricter limitations for nitrogen oxide (NOx) emissions from vessels based on their date of engine installation, with the strictest Tier III requirements to take effect in designated Emission Control Areas (ECA) beginning in 2016. At MEPC-66 in April 2014, an amendment that would delay the introduction of the Tier III standards to 2021 will be considered based on concerns arising from perceived equipment, supply chain, and cost barriers raised at MEPC-65 |
NOx Limits in MARPOL Annex VI
| Tier | Effective Date | NOx Limit (g/kWh) | ||
| N < 130 | 130 <=N<2000 | N > 2000 | ||
| Tier I** | 2000 | 17 | 45*n-0.2 | 9.8 |
| Tier II | 2011 | 14.4 | 44*n-0.2 | 7.7 |
| Tier III*** | 2016 | 3.4 | 9*n-0.2 | 1.96 |
“n” refers to rated engine speed (rpm)
* Excluding ships with marine diesel engines less than 130 kW or ships solely for emergency purposes
** Annex VI entered into force in 2004, but it applies retroactively to new engines larger than 300 kW installed on ships on or after January 1, 2000
*** Tier III applies only in emission control areas
Overview of SCR in marine applications
SCR is the only technology currently available to achieve compliance with the Tier III NOX standards for all applicable engines
Other technologies can either achieve Tier II standard or achieve Tier III standard for only a subset of applicable engines. SCR has been recognized as one of the most promising means of controlling NOX by a variety of countries and regulatory authorities. State-of-the-art SCR systems are capable of reducing NOX emissions by more than 90% under certain conditions. Furthermore, SCR has proven popular with equipment manufacturers because it allows NOx control with little or no fuel efficiency penalty, and sometimes a net benefit. This occurs because manufacturers can tune their engines for maximum fuel efficiency and use SCR to clean up the resulting “engine out” NOX. Today, SCR is a well-proven technology with over 500 applications in the marine sector in 2013
A number of manufacturing companies have invested in SCR in the 25 years since it was first applied to marine vessels. A significant number of companies based in Europe, the US and Asia are delivering marine SCR technologies capable of meeting current and future NOX reduction requirements. Table below presents a non- exhaustive list of companies pursuing engine, SCR and catalyst technologies. These companies supply full SCR systems, components, reagent, or some combination of the three. The collaborations between engine designer, builder and catalyst designer facilitate the development and delivery of a complete emissions reduction system
| Engine Technologies | SCR and Catalyst Technologies |
| Wartsila | Haldor Topsoe |
| MAN | Johnson Matthey |
| MTU | Hitachi Zosen |
| ABC | Panasia |
| Bergen Engines | Tenneco |
| Yanmar | Cormetech |
| Hitachi Zosen | Ceram (Ibiden Group) |
| Mitsubishi Heavy Industry | Nano |
| Mitsui | Dansk Teknologi |
| Himsen | Mecmar |
| Daihatsu | HUG Engineering |
CSR System Costs
Growth and development in CSR technology have been seen in areas such as stationary power plants where industrial SCR systems are similar to marine diesel systems. In all applications over time, production advances in the use of industrial SCR technology has been seen to reduce capital costs. Additionally, stabilization of costs of materials with increased demand suggests an increase in SCR suppliers, which is creating competition in the market, driving technology innovation and overall decreases in capital cost. This results in higher availability of SCR at more reasonable costs.
The International Association for Catalytic Control of Ship Emissions to Air (IACCSEA) developed a cost estimation model for SCR installation and operation. Application of the model provides a sample calculation that is indicative of the ranges of costs and benefits anticipated for marine SCR applications. Using the example of a 10 MW engine, powering a vessel of 20,000 DWT using HFO that spends 1500 hours annually in a NOX ECA, the capital expenditure cost (including system installation) will be of the order of $725,000 US. The major operational costs required to meet IMO Tier III from an IMO Tier I baseline NOX level would range from $2 to $5 million depending upon urea cost, while catalyst recharge would require on the order of $500,000 US. There will be a fuel penalty associated with increased backpressure associated with the SCR system and a potential fuel efficiency gain when operating a fuel optimized engine/SCR system. After taking into account a backpressure penalty (2%), a 4% fuel-efficiency gain generates fuel saving of $625,000. This equates to a total (undiscounted) operation cost of between $104,000 and $224,000 per year, or approximately $900 to $2000 per tonne of NOX reduced.
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Conclusions SCR is a well-proven technology. Those vessels with the longest track records using it have accumulated upwards of 80,000 hours of operation over the past two decades. In the more than two decades in which SCR technology has been fitted to vessels, a number of manufacturing companies have invested in the technology. Today a significant number of companies based in Europe, the US, and Asia are delivering marine SCR technologies to meet current and future NOX reduction requirements. It is notable that many of the applications to date have been retrofits, which can be more costly and difficult to operate than systems installed on new engines. Since IMO’s Tier III requirements will drive OEM applications, even fewer problems may be expected in the future. This review has identified no systematic barriers to meeting Tier III requirements in 2016 through the use of SCR. Vanadium-based SCR systems, supplemented where necessary with strategies to boost exhaust temperature in low-load operations, will be capable of reducing NOx over a sufficient range of operational conditions, particularly when paired with the 0.1% sulfur fuel that will be made available in sulfur emission control areas. Production and distribution of urea to marine vessels should be manageable given the relatively small volumes to be delivered, the limited number of ports that need to be served, and the identification of best practices in Europe. Environmental byproducts, notably ammonia slip and excess CO2 emissions, are not expected to be generated in significant volumes. Finally, the costs of installing and operating SCR are modest and are expected to fall over time as the Tier III requirements generate greater innovation and competition among manufacturers and suppliers. Based on this evaluation of technological capabilities and history of successful application of SCR technology to maritime vessels, we find no substantial equipment, supply chain, or cost barriers that would significantly inhibit the implementation of MARPOL NOX Tier III regulations for applicable vessels in 2016 as established by the IMO in 2008. |
More details may be found at the ICCT Working Paper entitled as ”Feasibility of IMO Annex VI Tier III implementation using Selective Catalytic Reduction”
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