Haldor Topsøe ECO-Jet wins award; reducing soot, HC and heavy metal emissions from ships powered by bunker fuel

5 December 2014

Haldor Topsøe A/S has won the Danish Engineering Product Award 2014 (in Danish Ingeniørens Produktpris 2014) for its new ECO-Jet solution. The product is a newly developed catalytic process capable of reducing emission of harmful substances such as soot, hydrocarbons and heavy metals from ships powered by bunker fuel, also known as fuel oil.

Particulate filter systems are developed for diesel engine exhaust with a relatively low sulfur and ash content. These systems can not be employed for maritime engines fueled with bunker oil, which contains very heavy hydrocarbons and polyaromatic compounds and is heavily contaminated with compounds which do not burn and end up as ash in the exhaust.

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The ECO-Jet catalytic process was developed over a number of years in cooperation with an Italian partner, EcoSpray. The process reduces up to 95% of soot emission from ships using bunker fuel and is the first of its kind. The ECO-Jet process also removes other harmful substances from the exhaust of engines using bunker fuel, for instance poisonous hydrocarbons and metals including vanadium, iron, nickel, silicon and sodium. The solution can be combined with a scrubber process to remove sulfur from flue gases. Bunker fuel may contain as much as 3.5 per cent sulfur.

According to the recently published patent (WO2014169967), essential features of ECO-Jet are a continuous passive regeneration of particulate filters by catalyzing the filters with soot combustion and hydrocarbon oxidation catalysts, thereby improving the fuel consumption by keeping the pressure drop over the particulate filters low and by periodically and effectively blowing off of ash by pulse injection of air into outlet of the filters. The catalysts remove sticky hydrocarbon-containing soot that facilitates the ash removal.

Soot in the exhaust gas from the engine contains further inorganic ash that cannot combust and therefore will accumulate in the filter over time and build up the pressure drop. Consequently, the ash must be removed by periodical reversing the flow direction of the exhaust gas through the filter or blowing off the ash by impulsed injection of air.

Basic steps in the process include:

• operating the engine at a load to obtain an exhaust temperature of the exhaust gas of at least 325°C;

• passing the exhaust gas at exhaust gas temperature 325 °C to 550 °C through at least one filter unit each comprising at least one particulate filter and capturing the soot, ash and heavy metals contained in the exhaust gas;

• continuously burning the captured soot and adhered hydrocarbons off the at least one particulate filter by contact with a catalyst on the filter;

• periodically disconnecting at least one filter unit from flow of the exhaust gas unit and closing the outlet of the at least one particulate filter; and

• subsequently pulse-injecting air into the closed outlet of the at least one particulate filter in reverse to the previous flow of the exhaust gas and blowing the captured ash and remaining amounts of soot together with the heavy metals off the filter.

The catalyst comprises titanium dioxide, oxides of vanadium and tungsten and metallic palladium; the catalyst reduces the ignition temperature of the trapped soot down to 350°C and at optimal process conditions further down to 325°C.

When they put out to sea, large ships using bunker fuel emit harmful black smoke, and this smoke represents a major source of air pollution locally and globally. With Topsøe’s new process, we have an operational technology in place that is able to reduce emissions of soot and heavy metals. The process has interesting, environmental perspectives and, for Topsøe, promising commercial perspectives as well.

According to Topsøe Senior Scientist Keld Johansen, while ships could sail on environmentally friendly marine fuel with a sulfur content less than 0.1%, such conversion is still much too expensive:

For many years now, the ship industry has discussed using environmentally friendly fuel. The problem is, however, that the global refinery capacity is still too small to replace bunker fuel. That is why we have to treat the exhaust from bunker fuel in another way. And with our catalytic process, this is feasible now.

Topsøe’s new emission process is the result of several pilot projects. The largest pilot was the cruise ship MS Queen Victoria, which accommodates more than 2,000 passengers.

Resources

• “Method And System For The Removal Of Particulate Matter Soot, Ash And Heavy Metals From Engine Exhaust Gas” (WO/2014/169967)