Using electrospun nanofibers to counter NOx emission from heavy shipping

Using electrospun nanofibers to counter NOx emission from heavy shipping

Monday 02 Mar 15

Contact

Vincenzo Esposito
Professor
DTU Energy
+45 46 77 56 37

Project BlueShip

Partners in BlueShip: DTU Energy (DK), Next Technotessile (IT), Labor (IT), Linari (IT), Akretia (D) and Stogda (Poland).

Read more about BlueShip: www.blueship-fp7.eu/

Maritime shipping has grown fourfold in 20 years and the pollution from shipping is fast becoming a serious health problem on land. DTU Energy is part of the EU project BlueShip to reduce NOx emissions by inventing a new lighter and more efficient Selective Catalyst Reduction-unit for heavy ships.

Maritime shipping carries about 90 percent of global trade. The ever increasing demand for global trade has led to a huge growth in ship traffic with four times as many ships at sea in 2014 than in 1992, corresponding to an annual growth of 6-10%.

This is good for the global economy but bad for the environment and public health as the ships are fueled by heavy bunker oil. This is the least refined fuel from the refineries and is almost not liquid; when combusted it releases heavy metals, sulfates (SOx), nitrogen oxides (NOx) and small particulates. It is estimated that emissions from shipping contributes with 14% of the total air pollution in Denmark.

Project BlueShip will help reduce NOx emissions from ships by halving the size and weight of the traditional Selective Catalyst Reduction system, SCR, reducing their cost and allowing more widespread deployment of NOx-cleaning systems in ships.

Better suited for ships 

Traditional SCR units operate by adding ammonia to the last stages of the exhaust fumes and sending them through very big stacks of porous, monolithic bricks of ceramic catalysts with a high surface area where the ammonia react with and destroy the NOx. The units are cheap, effective and work very well; but they are also very cumbersome, difficult to clean with poor reusability, and they react badly to the vibrations of a ship.

“Current SCR units are well suited for stationary applications such as cement and power plants where the vibrations and size don’t matter, whereas ships have more limitations”, senior researcher Vincenzo Esposito, DTU Energy, says.

DTU Energy at the Technical University of Denmark is expert in fluegas purification and leading in the field of novel materials and processing for ceramic components, making DTU Energy a perfect partner for the EU-sponsored Project BlueShip. Here the DTU researchers work with three industrial partners from the European shipping industry and researchers from Italy to transform the classical SCR into a lighter and more compact SCR better suited for the vibrations of heavy ships.

 “We intend to reduce size and weight of the SCR by 50 percent, reduce the purchase and installation cost by 20 percent and the operational and maintenance cost by 15 percent.”

Using millions of nanofibers 

The structure and key elements of the new SCR are currently being patented. The key idea is that the composition of the new SCR will be based on electrospun nanofibers with much higher surface area.

Electrospinning is an up-and-coming technique, where a starting solution is ejected as a droplet from a small needle into a very strong electric field. The field pulls the droplet into a very thin fiber. The end result is a mesh with very high surface area consisting of thin fibers, each measuring 30-50 nanometers across. A gram of the ceramic material is thus composed of millions upon millions of ceramic based nanofibers.

“A single gram of the fibers we produce have more than 40 square meters of reactive surface area in comparison to only a few square meter reactive surface areas per gram in the traditional porous SCR monolith. We are talking about a factor of ten more reactive area, enabling us to have much larger surface area in a smaller space”, Vincenzo Esposito explains.

He adds that the efficiency in terms of catalytic activity is the same as in current products.

“The main difference is that all our porosity is interconnected, whereas the standard SCR has large inactive areas, and we have a very high specific surface area. So we can reduce the size by half by changing the design and the morphology of the units.”

This will result in small exchangeable NOx-reducing units, to be introduced in smaller ships previously having too little room for SCR units, while opening up room for additional cleaning technologies at the bigger ships, enabling emissions to be cut further.

“We are confident that the new design and morphology of our SCR units will reduce the pollution from the international shipping quite a lot”, Vincenzo Esposito adds.

Good news for public health 

This is very good news for public health. In 2011, the Danish Centre for Energy, Environment and Health (CEEH) estimated that the emissions from international shipping were annually responsible for 50,000 premature deaths in Europe due to pollution-related diseases.

Project BlueShip is still in the process of getting the electrospun fibers incorporated in a working SCR system. The initial tests are promising and a prototype is expected early 2016.