Clean Transportation on the World’s Oceans
With over 40 billion ton-kilometers of cargo, maritime shipping is the most important mode of transport for the global economy and a key accelerator of globalization. Almost all of the ships that sail the seven seas are powered by diesel engines. But, in addition to CO2, these emit huge volumes of aggressive sulfur dioxide in particular. This gas is equally responsible for the formation of acid rain and the acidification of sea water as it is for causing chronic respiratory diseases. There is however an effective method of flue gas desulfurization – using hydrated lime from Fels. The idea has received the Xella Innovation Award.
The heavy fuel oil used by deep sea shipping is a by-product of the petrochemicals industry. According to the Federal Ministry of Transport and Digital Infrastructure (BMVI) this oil has an average sulfur content of 2.7 percent. Its toxicity would therefore be some three thousand times greater than that of automotive fuels. The 55,000 merchant ships that consume 370 million tons of heavy fuel oil each year emit some 20 million tons of sulfur dioxide (SOx) globally. This is about the same as 400 large scale coal-fired power stations.
In order to tackle the problems associated with this, the International Maritime Organization (IMO) has decided to progressively reduce the sulfur content of marine fuels. The current threshold value in the Emission Control Areas (ECAs) – which include the North Sea and Baltic Sea – is one percent, but from 2015 this will be reduced to just 0.1 percent. The current threshold value for global shipping is 3.5 percent, but from 2020 a maximum of 0.5 percent will be permitted.
Additional costs of 250 euro per ton of fuel
But this imposes huge costs on shipping companies because low-sulfur fuels are considerably more expensive. The heavy fuel oil (HFO) used to-date costs approx. 400 euro per ton while reduced-sulfur marine gas oil (MGO) currently costs approx. 650 euro. This means that the proportion of overall costs attributable to fuel will increase from the current 50 percent to 70 percent of overall operating costs. For a 10 MW ship this would mean additional costs of up to 3 million euro per annum.
While the European Union has stipulated the use of low-sulfur fuels for seagoing vessels from 2015, it is still permissible to use high-sulfur heavy fuel oil if the SOx threshold values can be maintained by using an efficient exhaust gas cleaning system. Currently, two exhaust gas cleaning systems are in use:
Dry EGCS process diagram
The dry scrubbing process (dry EGCS) and the wet scrubbing system that utilizes sodium hydroxide solution. The dry EGCS process – which is based on dry exhaust gas cleaning using hydrated lime pellets in a packed bed filter – is more advantageous because of its lower susceptibility to failure and comparatively low acquisition and operating cost. For this exhaust gas cleaning system, which is certified by Germanische Lloyd, the hydrated lime pellets (NautiCal) from Fels are the optimum absorbing material. These specially developed pellets take the form of a granulate with a grain size of two to six millimeters. The spent absorbing material is returned and can be used in other sectors of industry. The first dry EGCS system loaded with Fels NautiCal has been successfully commissioned on a new ConRo ship (roll-on/roll-off loading).
The excellent separation efficiency of NautiCal has now been confirmed by independent testing institutes. With its myriad benefits, it’s no wonder that we have given this innovative product from Fels the Xella Innovation Award 2012.