Technical Papers
Effect of Fuel Property or SCR System on Harmful Exhaust Emissions Such as N2O from Marine Diesel Engines*
Magoshiro Kuwabara**, Yoshio Takasugi**, Sumito Nishio**, Eiko Ishimura**
Yasuharu Nakajima**, Zhang Jie**, Masaaki Kikuchi**
From the viewpoint of global environment protection, regulations for prevention of air pollution from ships have been discussed in the International Maritime Organization (IMO) and the regulations about NOx and SOx are expected to enter into force January 1st. of 2000.
And global warming is recently such as serious problem that it is necessary to reduce greenhouse gas emissions. CO2 and N2O in exhaust gas contribute to global warming.
In addition to the above, IMO will revise the regulations every five years. Then, emission will be expected to be applied to other air pollutants including N2O in the near future.
Under these circumstances, we studied effect of fuel property or SCR (Selective Catalytic Reduction) system on harmful exhaust emissions such as N2O by using a 4-stroke diesel engine.
The following are found:
(1) N2O concentration from Marine Fuel Oil is approximately 10 times as high value as that from Marine Diesel Fuel.
(2) N2O concentration from as diesel engine is influenced more strongly by sulfur content in fuel than by nitrogen content in fuel.
(3) In using same fuel for a diesel engine, N2O concentration is influenced by NOx concentration. N2O concentration increases with an increase in NOx concentration.
(4) In addition to NOx reduction, reduction of N2O and HC is possible by using this SCR system.
1. Introduction
The addition of Annex VI specifying the prevention of air pollution to MARPOL Convention was adopted in IMO (International Maritime Organization). This leads to the regulation of NOx and SOx which are the air pollution substances to be discharged from ships from January, 2000 earliest. The sulfur content contained in the fuel is regulated for SOx, while the quantity of discharge is regulated for NOx. Though the regulation of the NOx emissions this time can be coped with by the adjustment of the engine, this regulated value is reviewed for every 5 years, and it is expected that this regulation becomes more and more stringent.
The global warming presents a serious problem, and it is an important issue to reduce the emission of the cause substances. The cause substances for the global warming to be discharged from marine engines include CO2 and N2O. For CO2, the improvement of the fuel consumption of the engine is effective, but the adjustment of the engine and the use of the emulsion fuel to reduce the NOx emission will worsen the fuel consumption, resulting in the problem to increase the CO2 emission. For N2O, even its actual situation can not be grasped now on how much N2O is discharged from marine engines using heavy oil for the fuel.
The use of the SCR system can greatly reduce the NOx emission, but also adjust the engine in a condition excellent in fuel consumption, and proves to be an effective method leading to the reduction of CO2. However, there is an unclear point how the harmful exhaust emissions such as N2O are influenced by the use of the SCR system.
Thus, the harmful exhaust emissions such as N2O to be discharged from marine engines were examined using Marine Diesel Fuel (MDF) and two kinds of Marine Fuel Oil (MFO), and it was experimentally examined using the SCR system how these harmful exhaust emissions were affected, and the results are reported below.
2. Test apparatus and method
2.1 Test engine
The test engine used in the test is the medium speed 4-cycle engine of 257 kW(350PS)/420 rpm in maximum continuous output, and its principal particulars are shown in Table 1.
* Translated from Journal of MESJ Vol.34, No.2 (Manuscript received Oct. 22, 1998)
** Ship Research Instiute (Shinkawa, Mitaka City)
