Proceedings of the International Symposium on Marine Engineering

(ISME) October 17-21, 2011, Kobe, Japan Paper-ISME501

NOx REDUCTION PERFORMANCES OF MARINE SCR SYSTEM

Yuji WAKATSUKI* and Keisuke MISAWA**

*Marine Diesel Engine Dept., Marine Machinery & Engine Division, Power Systems, Mitsubishi Heavy Industries, Ltd., 1-1-1, Wadasaki-cho, Hyogo-ku, Kobe 652-8585, Japan **Technical Dept., Akasaka Diesels Limited, 670-6, Yanagiaraya, Yaizu, 425-0074, Japan

ABSTRACT In order to deal with certainly coming Tier III of IMO NOx regulation, it will be necessary to use the SCR system for the main diesel engine on the new build vessel. On the other hand, catalyst of SCR has a characteristic of poisoned by sulphur easily under the low temperature condition. The latest model of marine diesel engines have higher engine performance, therefore the temperature of exhaust gas is very low compare with old type engines. Then authors and colleagues tried to make full scale SCR system and use it on the actual engine with condition of exhaust gas with 250C and RMA class fuel oil with sulphur of 0.7%. The reducing agent was 25% ammonia water. The catalysts equipped were vanadia-titania type which was used on diesel engines of cogeneration plants normally. Maybe this trial is the first of the world and we could obtain many precious data.

Keywords: Marine diesel engine, NOx, SCR, exhaust gas, fuel oil, ammonia water, reducing agent, catalyst, temperature, sulphur, ammonium hydrogen sulfate

1. INTRODUCTION

IMO/MEPC decided to regulate NOx from ships start building in 2011. This regulation is second step called Tier II. And more strict regulation called Tier III will start on 2016 only for the designated sea area called ECA. This Tier III regulation must reduce 80% NOx concentration from Tier I. At this present, single technology which can reduce NOx of 80% is only SCR technology. This technology is expected the stable and certainly effective for the NOx reduction on the diesel engines.

In Europe, many marine SCR systems are already adopted. However, most cases are equipped it on the ships installed medium speed four stroke cycle diesel engine as main engine. In a few cases, SCR equipped on the ships installed low speed two stroke cycle diesel engine. All of these SCR for two stroke cycle cases are equipped at before the turbocharger in order to obtain higher temperature exhaust gas.

As everybody knows well, the catalysts inserted in SCR are poisoned by ammonium hydrogen sulfate which generated from ammonia of reducing agent and sulphur oxides of exhaust gas. This poisoning is occurred under the low temperature condition. It is mentioned that the occurring condition of poisoning is 300C or less. In case of the recent low speed diesel engines which have higher engine performance, the exhaust gas temperature is under 300C normally.

On the other hand, it is very difficult to operate the ship with SCR equipped before the turbocharger where can be obtained higher temperature exhaust gas. SCR system has large thermal capacity, therefore, it is difficult to control the turbocharger under the low load condition or transient condition especially. Arrangement of exhaust pipes is also very difficult. As the final result with total decision, it was selected the challenge of SCR equipped after the turbocharger that was reported in this paper.

2. FEATURES AND PROBLEMS OF SCR Before explanation of the SCR challenges, it is

necessary to consider about the features and problems of marine used SCR in order to understand the test cases selected.

First of all, the SCR technology is only one solution without changing of the engine performance. Therefore, the diesel engine can operate with the best reliable condition, the highest economical performance and the lowest CO2 emission. The chemical reaction in the SCR (catalysts) dose not delivers the inconvenient waste.

The volume of SCR reactor is very huge and it is necessary the space to set up it in the engine room. Its construction has better to be able to replace catalysts easily. With consideration of engine room arrangement, the inlet of exhaust gas is lower side of SCR and outlet is upper side.

It is mentioned detail later, the reducing agent is selected 25% ammonia water. Urea water is not suitable for the lower temperature condition. Ammonia water itself is harmful for the human body. Then, it is necessary the special supplying system from the inlet of outside of ship to the tank and from the tank to the injection nozzle on the exhaust pipe. The boiling point of 25% ammonia water is around 39C. Therefore, in order to avoid the evaporation, it is necessary to equip cooling system or/and air conditioning system for the ammonia water supply system. It is also necessary to equip the control system of ammonia water flow quantity in order to avoid the ammonia leakage to outside. 3. FIRST PHASE TRIALS FOR SCR 3.1 Test Engine

Cooperation with Tokyo University of Marine Science and Technology, these trials were carried out with the test engine 3UEC37LA installed in the internal combustion engine laboratory of this university. Principal

Proceedings of theInternational Symposium on Marine Engineering

(ISME) October 17-21, 2011, Kobe, JapanC6-2 SUMMARY

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jinnaiCopyright of this paper is owned by Japan Institute of Marine Engineering (JIME).This paper is published on the web site of Japan Ship Machinery & EquipmentAssociation (JSMEA) with the permission of JIME.

particulars of this test engine are shown in Table 1.

Table 1 Principal Particulars of the Test Engine Engine type 3UEC37LA Stroke cycle 2 Engine output 1,103 kW Engine speed 188 min-1 Cylinder number 3 Cylinder bore 370 mm Piston stroke 880 mm

This test engine was manufactured by Akasaka Diesels and installed in the laboratory in 1988. Before the SCR test, it was carried out the full maintenance in order to improve its performance. However, the exhaust gas temperature of this engine was still higher. Compare with the latest engines, difference of the exhaust gas temperature was over 50C. This difference could not cancel by only changing the specification of turbocharger. Therefore, it was decided to add the electric air blower in the middle of exhaust pipe and it was achieved to decrease the exhaust gas temperature lower than 250C.

With the preparation of measuring devices, it was ready to start construction of the test rig including the SCR reactor, ammonia water tanks, ammonia water injection system and additional exhaust gas pipes and valves. 3.2 Test Rig Construction

The purpose of this trial was the confirmation of performance of SCR operated under the full flow exhaust gas with temperature of below 250C and using RMA class fuel oil with around 0.5% sulphur content. According to the temperature condition, the reducing agent was used 25% ammonia water. The square honeycomb catalysts inserted in the SCR was vanadia-titania type manufactured by Sakai Chemical Industry that was cooperated this project. This type of catalyst is used generally for the SCR on diesel engines which installed on stationary plants.

The test rig was constructed in the laboratory of Tokyo University of Marine Science and Technology and connected exhaust gas pipe of the test engine 3UEC37LA.

Fig. 1 Test Rig Arrangement for the First Phase Trials

Arrangement plan of the test rig is shown on Fig.1.

The catalysts in the SCR reactor were constructed by two row units and each unit was constructed by 36 pieces of catalyst. Total 72 pieces of catalyst were used for each trial. On the first phase trials, the exhaust gas flow

direction in SCR was the down flow. This arrangement was decided by the land used plant experiences and some information of the marine SCR installed before the turbocharger on the low speed diesel engines.

Two ammonia water tanks were set on the outside of the laboratory. Capacity of one ammonia water tank was 3,000 litters and the shape was cylindrical and material was polyethylene. These tanks were set in the enclosure in order to avoid flow out if the ammonia water leakage occurred. In order to be harmless of vaporized ammonia, the chambers which remove harm of ammonia by the water dilution were set additionally.

The supply of ammonia water to the injection nozzle on the exhaust pipe was carried out by the ammonia water supply pump. It is necessary to measure flow quantity of ammonia water accurately. The control of supplying quantity of ammonia water was carried out by the map control for engine speed.

The exhaust gas dilution blower was operated by the feed back control with exhaust gas temperature. 3.3 Measurements of Exhaust Gas and Fuel Oil

Measurements of exhaust gas were carried out for nitrogen oxides (NOx), oxygen (O2), carbon monoxide (CO), carbon dioxide (CO2) and sulphur oxides (SOx) with temperature and pressure.

NOx and O2 measurements were carried out at exhaust gas outlet of the turbocharger, inlet and outlet of SCR. NOx was measured by the Chemiluminescence detection method. O2 was measured by the zirconia method. The performance of SCR was decided by the difference of the concentration of NOx between inlet and outlet of SCR.

In order to calculate the exhaust gas flow quantity, the measurements of CO, CO2, temperature and pressure were carried out. CO and CO2 were measured by non- dispersive infrared absorbance method (NDIR).

SOx (converted to SO2) measurement was also carried out by NDIR. Measuring results of SOx was always closed with the results of calculation from sulphur content of the used fuel oil.

Measurement of fuel oil used also carried out by the analysis specialty company. Table 2 shows examples of analysis result of fuel oil used on the first phase and the second phase of this test series. The fuel oil used on the first phase except the fourth trial was around 0.7% of sulphur content and the second phase include the fourth trial was around 0.07%. Both fuel oil were not special. They were obtained easily anytime in Japan.

Table 2 Result of Fuel Oil Analysis (Examples) Item Unit No.1-3 trials No.4-8 trials Density g/cm3 0.8704 0.8765 Kinematic Viscosity mm2/s 2.926 2.736 Flash Point C 88.5 81.5 Cetane Index 44.7 40.7 Carbon Residue mass% 0.03 0.03 Carbon mass% 86.63 87.70 Hydrogen mass% 12.40 12.20 Nitrogen mass% 0.02 0.02 Sulphur mass% 0.73 0.065 Higher Heating Value J/g 44980 45120 Lower Heating Value J/g 42270 42410

Test Engine 3UEC37LA

SCR Reactor

Silencer

Ammonia Water Tanks

Ammonia Water Injection Nozzle

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3.4 Test Results of the First Phase In the test period of the first phase trial, as mentioned

before, the exhaust gas through SCR was flowed full quantity of 100% load of the test engine. The dilute air from the additional air blower also passed through SCR. The temperature of the gas through SCR was 250C. The exhaust gas characteristics were shown at Table 3. This test engine was manufactured in 1988 and then, the NOx concentration of the exhaust gas was not suit for IMO regulation.

Table 3 Exhaust Gas Characteristics at Inlet of SCR Kind of Gas Measuring Value

NOx 1585 - 1977 ppm O2 14.3 - 14.8 %

CO2 4.3 - 4.7 % CO 35.9 - 74.0 ppm

Flow quantity 7199 - 8036 Nm3/h

Fig.2 Photograph of the First Phase Test Rig

In the first phase trials, the test of SCR was carried

out four trials and each trial aim to spend about 100 hours for full load operation. The first trial operation was not successful. It had some problems in the measuring systems and could not evaluate the test result accurately. After the first trial, it was improved some measuring lines and add the pre-treatment system. According to these changing, the accuracy of measurement was improved and evaluation for the trial became possible.

The second trail of the first phase was also not suitable result. The NOx reduction rate of starting period was below 80% and finishing period was about 40%. It was considered that the cause of low performance at starting period was the inclined flow of exhaust gas at the inlet of SCR. Then, the CFD gas flow analysis of inside of exhaust gas pipe and SCR reactor was carried out. According to the result of analysis, the rectification of exhaust gas flow was tried by some punching plates. It was confirmed that the pressure distribution at the just inlet of catalysts by the pressure measurement which was used the Pitot tubes at the third trial.

After above improvement, NOx reduction rate was increased more than 10% in the third trial of the first phase. It could confirm the effect of rectification, however, the decreasing tendency of NOx reduction rate was same condition compare with the former trials before the gas

flow improvement. The main reason of decreasing SCR performance was considered that the catalysts poisoning by the ammonium hydrogen sulfate which was generated from the ammonia of reducing agent and sulphur oxides of exhaust gas. Sulphur oxides were generated at the combustion of the fuel oil contained sulphur. Therefore, in the next fourth trial, it was carried out with using the lower sulphur content fuel oil.

The fourth trial with fuel oil of sulphur content of 0.07% was carried out and obtained better performance of SCR. At least, decreasing tendency of NOx reduction rate improved certainly. The SCR performance of finishing period was almost same condition of the starting. Fig.3 shows the comparison of the trend data of the NOx reduction rate on both of the third and fourth trials.

Operating Hours

NOx Concentration

NOx Reduction Rate

NOx SCR Inlet of 4th Trial NOx SCR Outlet of 4th TrialNOx Reduction Rate 4th Trial NOx Reduction Rate 3rd Trial

Fig.3 Trend Data of NOx Concentration of the Fourth Trial

and NOx Reduction Rate Comparison with the Third Trial 3.5 Analysis Results of Catalysts Tried

In order to confirm the results of above mentioned trials, each catalyst was sampled and carried out the evaluation test under 250C condition and reviving trial under 300C condition on the laboratory test rig of Sakai Chemical Industry. Evaluation of the used catalyst was done by the rate of constant of reaction velocity (K/K0) which explained by the below equation (1);

K = -AV ln( 1 - / 100 ) (1) K: constant of reaction velocity AV: area velocity [Nm3/m2h] AV = SV / AP SV: space velocity [l/h] AP: contact area per volume [m2/m3] : NOx reduction rate [%]

(K0: K value of new catalyst)

It was obtained results which were shown on Table 4. This result of analysis was same as trend of NOx reduction tendencies of the trials on the test engine. In this table, the first trial and the second trial are same condition, and then the second trial analysis was omitted.

Table 4 Comparison of the Result of Analysis Number of Trial Running Hours K/K0

New Catalyst 0 1.00 First Trial 69 0.48 Third Trial 85 0.37 Fourth Trial 85 0.79

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It was considered from the results of the first and third trials on Table 4 that the poisoning of catalyst was progressed depending on the running hours. And it was understood very clear from the results of third and fourth trials which was the effect of sulphur content of fuel oil.

The laboratory analysis was also tried to operate with high temperature gas flow (300C, 24 hours) and analyzed and obtained the result of K = 0.99 from the sample of catalyst tested at the third trial.

In the first trial on the test engine, it was also tried the reviving catalysts with 300C (tuning with additional air blower) and twelve hours operation after first trial finished. These catalysts sampled after reviving trial and analyzed. The result was K = 1.00. It meant same as quite new condition. It also meant the main reason of decreasing catalyst performance was poisoning by ammonium hydrogen sulfate because ammonium hydrogen sulfate was mentioned generally to release from a catalyst in the circumstance of more than 300C.

Color of surface of catalyst also changed. Before using, it was milky white and after the trial some part especially upper stream part of catalyst was dark brown or black. However, after reviving test, it returned to close a white color. It was considered that the color of dark brown or black was the color of ammonium hydrogen sulfate. 4. SECOND PHASE TRIALS FOR SCR 4.1 Test Rig Reconstruction

After the first phase trials, in order to progress the trials effectively, the test rig was reconstructed. There were the four small test lines divided from the branched off exhaust gas pipe in the reconstructed test rig. It was possible to carry out the tests of four kinds of different conditions at the same time. Each exhaust gas passage had two catalysts in line, one ammonia water injection nozzle and one exhaust gas heater. The flow quantity of exhaust gas which passed through one catalyst piece was able to keep same quantity of the first phase trials. The exhaust gas heater and the additional air blower which installed in the first phase could control the exhaust gas temperature at the inlet of the catalyst freely. Outline arrangement of the reconstructed test rig for the second phase trials is shown in Fig.4 and the photograph is shown in Fig.5.

Unbalance of exhaust gas quantity occurred on the different test line with the different test condition was controlled by the flow quantity adjust damper. Dusts of exhaust gas were laid on the front surface of each catalyst unit in the first phase trials, therefore, the soot blowers equipped on each front surface of catalyst in order to remove dusts from the catalyst surfaces.

In accordance with the consideration of the actual ship arrangement of SCR equipped after turbocharger, SCR will be equipped between the diesel engine and the funnel. Therefore, in the reconstructed test rig, the exhaust gas flow direction in SCR was the up flow.

Each line has the exhaust gas components measuring devices, thermometers and pressure gages. The ammonia water injection quantity also controlled by engine speed as same as the first phase trials.

Additionally, as mentioned before, the boiling point of 25% ammonia water is around 39C. Then, especially

in the summer time, according to the higher room temperature and the shrunken ammonia water injection system, sometime ammonia water was boiled and blocked slender ammonia water pipes. In order to avoid blockade, it was necessary to cool down the ammonia water supply system by the air conditioning device.

Fig. 4 Test Rig Arrangement for the Second Phase Trials

Fig.5 Photograph of the Second Phase Test Rig

4.2 Test Results of the Second Phase

In the second phase trials, it is confirmed temperature condition, heat reviving and effect of soot blow with RMA class fuel oil contained about 0.07% sulphur. The test engine was operated 85% load and additional dilute air was cooled down the exhaust gas to 230C and the heater equipped each line heated up the exhaust gas to each target temperature. All trials except the last trial were operated total about 100 hours. The four trials of second phase named the fifth to the eighth trial.

In the fifth trial, it was confirmed that the influences of exhaust gas temperature for the SCR mainly. The lowest one was 230C and the highest was 330C. Depend on the exhaust gas temperature decreasing, the rate of NOx reduction was also decreased. It was confirmed that the decreasing tendency of the rate of NOx reduction with running hours was depended on the exhaust gas temperature. In the case of the temperature of 330C, it

Heater

Dilute Air

Ammonia Water Injection

SCR Reactor Inlet Line D

Line A Line B

Line C

To Silencer Exhaust Gas Branched Off

Flow Quantity Adjust Damper

Soot Blower

Soot Blower

Catalysts

To Silencer

SCR Reactor Outlet

Exhaust Gas Engine Outlet

Heater

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was not confirmed the tendency of decreasing the SCR performance with the running hours. However, all trials were similar results because of the lower sulphur content fuel oil.

In the sixth trial, it was tried the heat reviving process. The trials carried out 15 hours normal operation and 5 hours heat reviving operation and repeated 5 times. The exhaust gas temperature of heat reviving was 350C.

The test results of the sixth trial were very similar with the fifth trial. All cases were not so different and the tendency of SCR performance was slightly different depend on the exhaust gas temperature. However, in all trials, the SCR performances were back to initial condition after the heat reviving process. Therefore, it was confirmed that the poisoned catalysts could be revived by the short time heating. In this case, it was carried out NOx reduction continuously with ammonia water injection during the heat reviving process. Fig. 6 shows the test result of heat reviving process (350C) under the 250C operation.

Operating Hours

NOx Concentration

NOx Reduction Rate

NOx (Inlet) NOx (Outlet) NOx Reduction Rate

HeatReviving

HeatReviving

HeatReviving

HeatReviving

HeatReviving

Fig.6 Test Result of Heat Reviving Process

The tests of the seventh trial were confirmation and

comparison of dust removal effect. The dust removal devices were the simple soot blowing system and the small electrostatic precipitator (EP). The result of dust removal effect was not obtained clear difference in only 100 hours operation. There was slightly difference between with soot blowing system and without it. It was also not confirmed the influences to SCR efficiency in 100 hours. It was too short to confirm such effect. On another trial, it was confirmed the effect of the diesel particulate filter (DPF) and obtained similar result. It was necessary some soot removing system because upper flow side surface of catalyst was covered by dust. It was considered that this dust was not good effect for NOx reduction performance of catalyst. Finally, the simple soot blowing system was selected. One of the reasons of this selection was simple construction device.

The last eighth trial was carried out for the comparison test of catalyst. The smaller honeycomb pitch catalyst and two kinds of new developed catalysts were adopted and they were operated 50 hours on the test rig with 250C of exhaust gas. It was obtained a few tendencies, however, it was too short period to judge them reasonably. It is necessary more trials and consideration to obtain the conclusion.

It is not able to say that the present material and construction of catalyst is not suitable for the marine application. Especially, these catalysts have many actual

results on stationary plants of medium speed diesel engines. And the material and manufacturing costs are also important. In the marine application, the SCR reactor will become the huge device. Therefore, the higher cost precious material like platinum will not be allowed to use. 4.3 Analysis Results of Catalysts Tried

As same as the first phase trials, each catalyst tried was confirmed the performance by K/K0 which explained section 3.5 and equation (1) in this paper. On the second phase, it was able to compare the data of different trials. Therefore, the comparison of K/K0 was able to carry out by not only on each trial but also on each test condition. The compared test conditions were the exhaust gas temperature, the heat reviving process, the dust removing method and new material and construction.

Table 5 shows comparison of K/K0 from the results of different exhaust gas temperatures. These data were obtained on the fifth trial without the dust removal system and heat reviving process. It was able to understand that the performance of catalyst decreased depending on the exhaust gas temperature with RMA class fuel oil including 0.07% of sulphur content.

Table 5 Comparison of the Result of Analysis Exhaust Gas Temperature Running Hours K/K0

New Catalyst 0 1.00 330C 100 1.00 250C 100 0.90 230C 100 0.75

Table 6 shows comparison of effect of the heat

reviving process without the dust removal system. This result shows that the short period heat reviving process will be useful to operate SCR for a long term under the low exhaust gas temperature.

Table 6 Comparison of the Result of Analysis Exhaust Gas Temperature Running Hours K/K0

New Catalyst 0 1.00 300C 100 1.02 280C 100 1.01 250C 100 1.03 230C 100 1.02

Table 7 Comparison of the Result of Analysis Dust Removal Systems Running Hours K/K0

New Catalyst 0 1.00 Nothing + HR 100 1.03

Soot Blower + HR 100 0.99 Nothing 100 0.90

EP 100 0.88 DPF 100 0.93

+ HR: with heat reviving process

Table 7 shows comparison of effect of dust removal system, soot blowing system, EP and DPF. All data compared were test results with 250C of exhaust gas temperature. Only the comparison of the soot blowing system was carried out under the condition with the heat reviving process. All systems were considered that they were effective for the NOx reduction performance, however, these data did not indicate so big difference.

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Before the heat reviving process

Direction of exhaust gas flow

After the heat reviving process

Direction of exhaust gas flow

Fig. 7 Catalyst Surface Condition before and after the Heat Reviving Process

In the seventh trial in the second phase test, it was

confirmed that difference of catalyst between before heat reviving process and after that. Fig. 7 shows the pictures of catalysts of each condition. Dark colored part indicated catalyst poisoned by ammonium hydrogen sulfate. On the same part of each catalyst, the color of catalyst surface of after the heat reviving process was brighter than before. Depend on the K/K0 estimation, the catalyst after reviving process was nearly equal to new catalyst. (Table 7)

Table 8 shows comparison of K/K0 for the new developed catalysts. This comparison data were catalysts operated with 250C without the heat reviving process and dust removing system. As mentioned above, it was too short period to judge them. It is necessary to carry out the longer term trial.

Table 8 Comparison of the Result of Analysis Catalyst Type Running Hours K/K0 New Catalyst 0 1.00 Conventional 100 0.90 Smaller Pitch 50 0.92 New Type I 50 0.78 New Type I 50 0.81 New Type II 50 0.85

5. CONCLUSION

In case of all actual vessels in service installed low speed diesel engine equipped marine SCR, all SCR reactors were equipped before the turbochargers because of the lower temperature of exhaust gas after the turbochargers. However, SCR equipped before the turbochargers was inconvenient for the maneuvering of the ship. The SCR reactor is very large device compare with the main diesel engine. Therefore, the thermal capacity of SCR is also large, and it makes slow responsibility against the changing of engine speed. In case of operation under emergency or low speed or rough sea condition, the ship will not be able to control freely. Sometime, the ship will be possible to fall into very dangerous condition with SCR. Then, the ship will have to cut the SCR operation in this case.

On the other hand, NOx reduction is necessary in the coastal area where the NOx from the ship influences to the land area. In almost coastal areas, the ships operate with lower speed. Therefore, an SCR equipped before the turbochargers will not give a good performance. This was a main reason why the authors investigated the possibility of the SCR equipped after the turbochargers on a low speed diesel engine as same as the SCR with the medium speed diesel engines on the many European ships.

These many trials were carried out on the years of 2008 (the first phase) and 2009 (the second phase) mainly

and concluded in 2010. It was obtained the good results, especially, the possibility of SCR adoption became higher. The SCR will be able to equip on the position after the turbochargers and supply enough NOx reduction performance in the ECA.

Fuel oil used will have to be RMA class with sulphur content of 0.1% or less. It will be considered that ECA will be regulated SOx and PM mostly. Therefore, in almost ECA, the ships will have to use the fuel with sulphur content of 0.1% or less. In this circumstances, from the results of the reported trials, the possibility of the SCR after the turbochargers increases. The heat reviving process and the dust removal system are useful devices and necessary for the long term using of SCR system. 6. ACKNOWLEDGEMENT

This national project called Super Clean Marine Diesel was supported by the Nippon Foundation. The research and development contract for the large slow speed diesel engines application was carried out by the Japan Marine Equipment Association, Akasaka Diesels Limited and Mitsubishi Heavy Industries, Ltd. The project was coached by Dr. Tatsuro Tsukamoto of Tokyo University of Marine Science and Technology and cooperated by Sakai Chemical Industry Co., Ltd. The authors thank all peoples related with this project and colleagues who supported this activities and consideration.

This project is carrying out continuously and the marine SCR equipped on the actual vessels. The authors expect that the project would be finished successfully and the results will be helpful for the international activities of IMO regulation. 7. REFERENCES (1) Motomura, O., Maeda, K., Kondo, J., Tatsumi, K.,

Okabe, M. and Oda, Y., Dynamic Characteristic of a Two-Stroke Slow Speed Diesel Engine with De-NOx System, (in Japanese), Journal of the MESJ, Vol.34, No.1 (1999), pp.41-47.

(2) Nakayama, N., Yamashita, H., Ueshima, K., Arahori, Y., Okada, Y. and Tokuoka, T., On-Board Tests using Selective Catalytic Reduction (SCR) Pilot Reactor, (in Japanese), Journal of the MESJ, Vol.33, No.5 (1998), pp.332-339.

(3) Yaguchi, K., Yoshida, T., Sato, K., Kobayashi, T. and Ishii, A., High NOx Reduction System Mounted on 500 GT Class Vessel, ISME Yokohama 1995, pp.92-98.

(4) Sasaki, K. and Aabo, K., SCR Experience on MAN B&W 2-stroke Diesel Engines and New NOx Reduction Methods, (in Japanese), Journal of the JIME, Vol.43, No.3 (2008), pp87-94.

(5) Fujita, K., Nochi, K., Wakatsuki, Y., Miyanagi, A. and Hiraoka, N., Development of Selective Catalytic Reduction for Low-speed Marine Diesel Engines, MHI Technical Review, Vol.47, No.3 (2010), pp48-52

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