Diesel Technology

June 9, 2009, Posted by Krisna Ditya Utama at 8:21 am


Emtec, Nymo and Pon Power develop NOx-reducing system for marine engines


STT Emtec AB, AS Nymo and Pon Power Scandinavia have announced the launch of Marine DNOx, a new exhaust gas recirculation (EGR) system for NOx reduction. The system has been developed specifically for small- and medium-sized vessels with high-speed diesel engines offering up to 2 MW of output in the maritime and offshore sectors.


The Sweden-based STT Emtec provides emissions reduction equipment, including EGR systems for automotive applications. AS Nymo of Norway owns two fully capable yards in Grimstad and Eydehavn and provides a wide range of services to the offshore and shipping industries. Pon Power Scandinavia is the dealer of Caterpillar and MaK engines in Scandinavia.

Under a recently signed agreement between the companies, STT Emtec will develop and manufacture Marine DNOx in its production facility in Sweden, while Nymo will be responsible for distribution and installation of Marine DNOx to the maritime and offshore communities throughout Norway.

Pon Power Scandinavia will be responsible for marketing to the Norwegian market for all Cat and MaK applications. “Our customers are asking for NOx abatement equipment, and it is with great satisfaction we now can offer this,” said Jannik Stanger, head of research and development at Pon Power Scandinavia.

“STT Emtec has a successful history of providing NOx-reduction systems to the automotive industry around the world. The launch of the Marine DNOx is a direct result of our knowledge of NOx-reduction technologies in the automotive sector, but has been tailored to the specific needs of ships,” said Anders Björk, CEO of STT Emtec. “Marine DNOx is the culmination of several years of research and development work and will provide vessel owners with a cost-effective solution to the challenge of NOx reduction.”

Following the establishment of the NOx Fund in Norway in 2007, there is an increasing demand for NOx reduction from stationary and marine sources. Marine DNOx is designed to allow vessel owners to significantly reduce their NOx emissions, improving their environmental performance and, in turn, resulting in lower NOx tax payments.


“EGR is a well-known and cost-effective method for reducing NOx from automotive diesel engines. By recirculating a part of the exhaust gas back into the air inlet, NOx emissions can be reduced up to 50%,” said Björk. “Together, STT Emtec, Nymo and Pon Power Scandinavia have taken this EGR technology one step further by now introducing EGR for marine applications.”

Technical development and field trials are under way on the Simon Møkster supply ship Strilmøy, which is outfitted with four Caterpillar 3516B engines. Production of the system will begin for the Norwegian market this year.

Rolf Urfjell, managing director, AS Nymo, said, “As a leading supplier of services to vessel owners — from service and repair to product installations and retrofits — we are now seeing increasing demand for NOx technologies that are both simple to install and cost-effective. Marine DNOx ideally meets these requirements. We are delighted that our partnership with STT Emtec and Pon Power Scandinavia will allow us to offer this robust and proven NOx reduction technology, bringing significant benefits to vessel ownersthroughout Norway.”

The DNOx works by using a pickup to lead some of the exhaust gas through a particulate filter to trap the solid parts. The cleaned gas is cooled and led via an EGR valve to the air intake system, which is positioned after the inlet filter but before the turbocharger compressor. The EGR gas and the intake air become completely homogenized and the engine gets an air mixture that contains less oxygen but more carbon dioxide and water than the ambient air. A lower oxygen content in the air and a lower combustion temperature result in less formation of NOx.

The lower combustion temperature is caused by the higher heat capacity of carbon dioxide and water in comparison with air; in other words, more energy is required to heat these gases. It is, however, important to control the rate of the oxygen. If it is too low, the result will be higher fuel consumption and particulate emissions. A careful control of the amount of recirculated exhaust gases is important to achieve the optimum balance.

One challenge has been to avoid sulfuric oxidation in the exhaust gases. The heavier fuel oils contain sulfur, and because of this the system contains no catalytic converter, which would be typically used in on-road applications. The particulate filter is burned clean by hot air generated from a hot-air gun located in front of the filter.

“The fact is that all reduction of NOx, which takes place in the combustion zone, is based on making the combustion less efficient. This results in a certain increase of the specific fuel consumption, and the emissions of particulates increase as well,” said Nils Myers of STT Emtec. “However, the EGR technology will lessen this effect and a 40% reduction of NOx can be achieved with a hardly measurable increase of the specific fuel consumption and emissions of particulates. The NOx emissions can be further reduced, but then with higher specific fuel consumption and particulates emissions.”

The EGR technology is particularly suitable at partial load operation, a mode of operation often seen in marine applications like supply vessels and fishing boats. “Our technology is also well suited for retrofit applications, and since it is light and takes a relatively small space, two men can carry and install the system in less than a week,” said Myers. “The work can be done by local staff under supervision by Nymo/STT Emtec.

”We have also started up a project with Nymo and Pon Power Scandinavia in order to further develop the technology to fit low-speed diesel engines,” Myers continued, “and we plan to get a test engine in operation before the end of 2009.”


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