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2 TransNav : International Journal on Marine Navigation and Safety of Sea Transportation

2 2015

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Technologies for the Reduction of Nitrogen Oxides Emissions

Arsenie P., Martinas G., Gheorghe C., Arsenie A.

TransNav : International Journal on Marine Navigation and Safety of Sea Transportation

2015

Vol. 9, no. 2

251--256

When it comes to gas turbines, their main problem concerning pollutant emissions is represented by nitric oxides. Among other emissions, sulphur oxides being much reduced due to the use of liquid distilled and gas fuels with a low content of sulphur. Using water or steam injection became the favourite method during the '80s and especially the '90s since "dry" methods and catalytic reduction were both at the beginning of the development phase. Catalytic convertors have been used since the '80s and they are still used although the costs of renewing the catalyst are very high. In the last twenty years a gradual decrease has been registered on the limits of nitric oxides from 75 ppm to 25 ppm, and now the target is oriented towards the 9 ppm level. The evolution of burning technologies of combustion makes it possible to control the level of production of nitric oxides even from the source without being necessary to use "humid" methods. This, of course, opened the market for gas turbines because they can function even in areas with limited quality water reserves, such as maritime platforms and in the desert. In this paper, we are going to show that, although water injection is still used, "dry" control technologies of burning became favourite methods for the majority of users on the industrial power generators market. The great dependency between the creation of nitric oxides and the temperature reveals the effect of direct water or steam injection on reducing nitric oxides. Recent research showed that a reduction up to 85% of nitric oxides may be obtained by using the water or steam injection all together with the improvement of aerodynamic character of the burning room.

Solution to Reduce Air Environmental Pollution from Ships

Pham H.T., Nguyen T.M.

TransNav : International Journal on Marine Navigation and Safety of Sea Transportation

2015

Vol. 9, no. 2

257--261

Exhaust gas emissions from ships are increasingly polluting the air environment seriously. Therefore, the MARPOL 73/78 Annex VI is applied for all ships from 2017, Annex VI provided that the concentrations of NOx,SOx CO contained in ship’s exhaust gases must be less than 6.4 g/kWh, 0.6 g/kWh, and 5.5g/kWh respectively. Today, there are many solutions to reduce pollution emissions from exhaust gas of ships, such as improving combustion, using oil emulsion, using biofuel,…However, these solutions also have a handful of disadventages such as being unable to thoroughly resoulve problems, high cost, and very difficult to improve the quality of ship exhaust gas emissions for old ships. Exhaust gas treatment method uses a centralized treatment system where exhaust gas from the thermal engines is taken in a centralized treatment system before discharging into the air. After centralized treatment system, in comparision with raw exhaust gas, soot can be reduced by 98%, NOx can be reduced by 75%, SOx can be reduced by 80%. This method of treatment is not only low cost, good quality but also make marine heat-engines still use traditional fuels as well as need not improve its structure.