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EXHAUST GAS SCRUBBER INSTALLED ONBOARD MT “SUULA”

PUBLIC TEST REPORT

20 JUNE, 2010

Compiled by Wärtsilä Finland Ecotech Scrubber Project Team.

© Wärtsilä

© Wärtsilä PUBLIC TEST REPORT (30)

ABSTRACT

Background IMO and EU legislation is clearly moving towards lower levels of permitted exhaust gas sulphur oxide emissions from ships. These regulations offer the choice of compliance by using expensive fuels with less sulphur, or by cleaning exhaust gases thus enabling ships to use cheaper traditional marine fuels. This report describes testing as a part of the development of a marine exhaust gas cleaning system.

Test targets The testing targets of an exhaust gas scrubber installation onboard the MT “Suula” include certification of the scrubber, exhaust gas cleaning performance measurements, analyses of the scrubber effluent and other liquids, testing of effluent cleaning unit operation and analyses of generated sludge, measurements of alkali and water consumption, scrubber noise attenuation and exhaust gas plume observations. In addition some special tests were carried out and system reliability was studied.

Test execution Testing was started in 2008 and completed in 2010. The MT “Suula” travelled mainly around the Baltic Sea, but also visited North Sea harbours. Normal ship operation was not interrupted or limited during the tests. Test data was recorded in many ways, including a tamper-proof recording device. Gas and liquid samples were taken. Classification societies surveyed the certification process.

Test results Test results were very positive. “Germanischer Lloyd” and “Det Norske Veritas” certified the scrubber system. The measured sulphur reduction was excellent, well within the International Maritime Organisation’s (IMO) most stringent limits. Furthermore, other measured exhaust and effluent parameters were favourable. The effluent was very clean, and the sludge produced by the water cleaning unit was found suitable for normal disposal at port reception facilities. The scrubber and its auxiliary systems worked with a good level of reliability. Sea conditions did not affect or limit the scrubber’s use.

Conclusion The marine exhaust gas fresh water scrubber is ready for introduction onto the market.

(30) PUBLIC TEST REPORT © Wärtsilä

TABLE OF CONTENTS 1 INTRODUCTION ........................................................................ 6

1.1 SCRUBBER PROJECT BACKGROUND ............................................................6 1.2 LEGISLATION DEVELOPMENT ...................................................................7 1.3 SCRUBBER ONBOARD THE MT “SUULA” ......................................................8

2 RESEARCH OBJECTIVES ............................................................ 9

2.1 TECHNICAL AND ENVIRONMENTAL OBJECTIVES ..............................................9 2.2 SCRUBBER TEST PROGRAM .....................................................................9

3 TEST RESULTS AND ANALYSES .................................................. 9

3.1 CERTIFICATION TESTS ........................................................................ 10 3.2 PARTICLE MEASUREMENTS .................................................................... 13 3.3 CONTINUOUS EMISSION MONITORING SYSTEM (CEMS) ................................ 14 3.4 SULPHUR TRIOXIDE TEST ..................................................................... 16 3.5 REMOVAL OF NITROGEN OXIDES ............................................................. 17 3.6 DYNAMIC TEST ................................................................................. 17 3.7 PLUME ........................................................................................... 18 3.8 NOISE ........................................................................................... 20 3.9 EFFLUENT COMPOSITION AND QUALITY ..................................................... 21 3.10 TESTS WITH WATER PRODUCED IN AWP-PROCESS ....................................... 23 3.11 SLUDGE QUANTITY AND QUALITY ............................................................ 23 3.12 SYSTEM RELIABILITY .......................................................................... 25 3.13 CORROSION TESTS ............................................................................ 25 3.14 HEALTH AND SAFETY ASPECTS ............................................................... 26 3.15 ENERGY CONSUMPTION ....................................................................... 26

4 LEGISLATION DEVELOPMENT .................................................. 27

4.1 GENERAL ........................................................................................ 27 4.2 IMO RESOLUTION MEPC.185(59) ........................................................ 27 4.3 EU DIRECTIVE 2005/33/EC ................................................................ 28

5 SUMMARY ............................................................................... 29

5.1 TEST TARGET ................................................................................... 29 5.2 TEST RESULTS .................................................................................. 29 5.3 RECOMMENDATIONS ........................................................................... 29 5.4 CONCLUSIONS ................................................................................. 29


Abbreviations

AWP/AWT Advanced Water Purification system, Advanced wastewater treatment system

CEMS Continuous Emission Monitoring System

CO2 Carbon dioxide

EU European Union

GRP Glass Reinforced Plastic

IMO International Maritime Organisation

MARPOL International Convention for the Prevention of Pollution from Ships

MEPC Marine Environmental Protection Committee (IMO)

MT Motor Tanker

NaOH Sodium hydroxide

NOx Nitrogen Oxides

PAHphe Polycyclic Aromatic Hydrocarbons, phenanthrene equivalence

SECA SOx Emission Control Area

SOx Sulphur Oxide


1 INTRODUCTION

1.1 Scrubber project background Within the Finnish maritime cluster, the first idea to initiate a marine SOx-scrubber development project was born in 2005 and was based on developing environmental legislation for the reduction of emission of sulphur oxides. Four companies started to discuss the possibility of developing a marine scrubber. These four companies developed a project plan and an application for R&D funding together. Wärtsilä was selected as project leader. The scrubber project was considered a challenging, cross-scientific R&D project, offering opportunities for partners to increase their knowledge and opening possibilities for cooperation between research institutes and universities with relevant enterprises. One of the reasons for public economical funding was the beneficial ecological effect of the project.

In September 2007 the project steering committee decided to install a test scrubber on the tanker MT "Suula", owned by Neste Shipping. The first start of this scrubber was on the 10th November 2008 and was simultaneously the beginning of the project testing phase.

Figure 1. Exhaust gas scrubber onboard the MT "Suula".


1.2 Legislation development The MARPOL Annex VI convention was adopted by the IMO in 1997 and ratified in 2004. The most important regulation was and still is regulation 14, limiting the emission of sulphur oxides in SOx Emission Control Areas (SECAs) to a level corresponding to 1.5 % sulphur in the fuel.

The IMO revised MARPOL Annex VI regulations for the prevention of air pollution from ships among others include the following parts relevant for this R&D project:

Regulation 3, exceptions and exemptions, covers trials for ship emission abatement technology research and emissions from petroleum activity.

Regulation 4, equivalents, allows alternative fitting, material, appliance, procedure, fuels or compliance methods. Selective catalytic reduction and scrubbers are permitted.

Regulation 14, sulphur oxides and particles, limits the use of high sulphur fuels. The reduction scale is globally from 4.50 to 0.50 % sulphur and inside the emission control areas from 1.50 to 0.10 % sulphur. No “Micro-Areas” are specified in the rules.

Regulation 17 requires port reception facilities for scrubber residues.

Global sulphur limits in fuel mass are shown in figure 2. Fuel type is not regulated which means that both HFO and distillate are permitted. Exhaust gas cleaning is an allowed alternative under Regulation 4 to achieve any regulated limit.

Figure 2. IMO sulphur limits for years 2008-2020 (% mass).


1.3 Scrubber onboard the MT “Suula” The scrubber principle is shown in figure 3. A medium speed 680 kW auxiliary engine feeds exhaust gas to the scrubber. The installed scrubber system is of type: fresh water, closed loop, main stream, wet sump and packed bed. The material is glass reinforced plastic (GRP). In use, uncleaned effluent is not pumped into sea from the scrubber. Impurities are collected in effluent treatment unit, pumped to the sludge tank and finally moved onshore for final disposal.

The working principle of a fresh water scrubber is based on a process whereby acid can be neutralised using an alkaline chemical. In a scrubber, exhaust gas sulphur oxides are removed to wash water which contains sodium hydroxide. As a result, the chemical sulphur compounds sulphates are formed from the exhaust gas sulphur. These neutralised products flow into the sea through the water treatment process. Adding the resulting sulphur compounds to seawater is not a problem because seawater contains some 1015 (1,000,000,000,000,000) tonnes of sulphur in seawater as sulphate overall.

The scrubber consumes technical fresh water which evaporates into the atmosphere with the exhaust gas. This evaporation is minimized with the use of the scrubbing water cooler.

Figure 3. Fresh water scrubber operational principle.


2 RESEARCH OBJECTIVES

2.1 Technical and environmental objectives The technical target of the project was to develop a suitable abatement technology, based on scrubbers, for sulphur oxides in the exhaust gases of marine diesel engines and oil-fired boilers. Scrubbers are widely known in land-based applications. However, in the marine environment, specific IMO regulations and ship design requirements prevented a straight adaptation of land-based designed scrubbers for marine applications.

The general environmental goals of Wärtsilä Corporation are as follows: Supply power solutions offering high efficiency with low environmental

load. Continuously improve the environmental performance of its products and

services. Enable the tightening of the relevant international environmental

regulations of e.g. IMO and World Bank which are considered a basis for R&D.

These objectives were also guidelines for this project. By using scrubber technology, the sulphur content in the atmosphere could be drastically reduced or virtually eliminated.

2.2 Scrubber test program The scrubber test program was assorted to following segments:

System start-up Certification tests Exhaust gas cleaning efficiency tests Particle tests Noise tests Dynamic tests Sludge tests Tests with cleaned sewage water (AWP test) Corrosion tests Exhaust gas plume measurements

3 TEST RESULTS AND ANALYSES

The scrubber’s own automation system was used for measurement data collection. In addition, manual parameter recording was used to help with this work. Accredited and special measurements were done by subcontractors like Pöyry Finland Oy, Turku University of Applied Sciences or Wärtsilä Vibration, Environment and Measurement Technology Department. These organizations produced their own reporting.

Several fuel, gas and water samples were taken from the scrubber system during the test period. These samples were analyzed later in accredited laboratories.


Certification required classification society inspections onboard the MT “Suula”. Germanischer Lloyd and Det Norske Veritas had their own personnel involved in the certification process.

3.1 Certification tests The purpose of the tests was to demonstrate the scrubber performance to the certifying bodies for certification of the unit under the IMO Marpol regulations. The certification process was started in accordance with IMO Resolution MEPC.170(57). These regulations were slightly improved when the IMO in July 2009 adopted IMO Resolution MEPC.184 (59).

These regulations define limits for parameters which were measured during the tests. The accredited independent body, Pöyry Finland Oy, carried out measurements and the tests were performed with both high (3.4 %) and low sulphur (1.5 %) heavy fuel oil.

The Wärtsilä scrubber system is designed to efficiently remove the sulphur from the exhaust gases. The certification tests were performed with four different scrubber load levels (8 %, 40 %, 70 % and 100 %) and emission measurements took place simultaneously before and after the scrubber. SO2 reduction is demonstrated by measuring SO2 and CO2 concentrations in the exhaust gas after the scrubber. The results are presented in Table 1. Measured sulphur dioxide removal efficiency was 100 % for all operating conditions, throughout the load range, even when using high sulphur fuel.

Test 1 2 3 4 5 6 7 8

Engine test load % 8 40 70 100 8 40 70 100

Fuel sulphur content % m/m

1.5 1.5 1.5 1.5 3.4 3.4 3.4 3.4

SO2 after scrubber (*) ppm-v 0 0 0 0 0 0 0 0

CO2 after scrubber %-v 4.7 6.1 6.5 6.6 4.6 6.0 6.4 6.7

SO2/CO2 ratio ppm/% 0 0 0 0 0 0 0 0

(*) A ‘0’ value indicates the result was below measurable limits (~2 ppm). Measurement equipment from a 3rd party accredited company has an accuracy of ±2 ppm. For reference 0.1 % S corresponds to 20...30 ppm.

As a part of the certification test, effluent quality was demonstrated to classification societies. The Wärtsilä scrubber fulfils all the effluent quality requirements due to the efficient Wärtsilä water treatment unit. The IMO resolution MEPC.184 (59) defines limits for pH, turbidity, PAHphe and nitrate content. Also, metals in the effluent were measured. The tests showed that after the water treatment unit, PAHphe concentration (figure 4) and turbidity (figure 5) are clearly under IMO limits.

Table 1. Sulphur removal efficiency during certification tests.


Figure 4. Phenanthrene in the effluent.

Figure 5. Turbidity in the effluent.

Sodium Hydroxide (NaOH) is added to the scrubbing water circulation to maintain the process pH and consequently the efficiency of SO2 removal. Due to efficient NaOH dosing and monitoring, the pH of the effluent was over 6.5 which is the IMO limit for the effluent pH (figure 6). Certification tests also proved that nitrate concentration in the effluent is under IMO limits.


Figure 6. pH in the effluent.

Figure 7. Nitrate in the effluent.

One of the main targets of the MT "Suula" project was to get approval for the scrubber. For the Suula tests, a separate two-day program was created. As well as the performance, the safety of the installation was approved. Wärtsilä SOx scrubber performed successfully in the tests, and is the first ever marine scrubber issued with a certificate. The certification was carried out by major classification societies: Det Norske Veritas and Germanischer Lloyd.

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PH IN THE EFFLUENTIMO limit: The pH of the effluent should not be lower than 6.5.

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DISCHARGE WATER NITRATE CONCENTRATIONSuula

Test load 100%.

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Under MARPOL regulations, it is mandatory to keep certain exhaust gas cleaning system documents onboard. Such documents are, for example, the EGC-SOx Technical Manual (ETM) which describes the cleaning system technology, system performance and maintenance needs.

Another important document is the EGC Record book which is a log book for service and maintenance. The onboard Monitoring Manual (OMM) describes the monitoring instruments of the cleaning system and contains a device list, maintenance requirements and calibration procedures. All MARPOL-related documents were approved during the Suula certification process.

3.2 Particle measurements Particle washing tests were performed with the standard ISO-8178, and Turku University of Applied Sciences carried out the measurements.

Particles were measured before and after the scrubber and tests were performed with five different scrubber load levels (10 %, 25 %, 50 %, 75 % and 100 %). The fuel sulphur contents were 1.5 % and 2.1 %.

Tests proved that the scrubber system removes exhaust gas particles from the exhaust gas. The highest particle reduction (65 %) was with high sulphur fuel and with an engine test load of 75 %.

Figure 8. Particulate reduction in scrubber.

PARTICULATE MEASUREMENTS ISO-8178Reduction (%)

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3.3 Continuous Emission Monitoring System (CEMS) A CEMS was used to monitor sulphur dioxide, nitric oxides, oxygen and carbon dioxide content in exhaust gases during the tests. In the following charts, the accuracy of the system is shown. CEMS results were compared to measurements of an accredited company (Pöyry Finland Oy). Based on the manufacturer’s information, all the analyser channels have been tested and approved to be within the requirements of the MEPC.103 (49) Chapter 5 Appendix 3. Careful installation, maintenance and calibration processes are needed to guarantee reliable operation of the CEMS.

The analyser type used in MT “Suula” had exhaust gas sampling lines and sampling probes which were electrically heated. This arrangement consumed energy and there were some air leaks, failure currents and moisture problems, especially in the sampling lines after the scrubber. Dirty exhaust gases had to be filtered before the analyser and these filters had to be replaced frequently. Also, the calibration gases for the analyser had to be stored onboard. One extra weakness in the CEMS was the limited age of some analyser components.

The pilot test demonstrated reliable means for monitoring, documentation and certification of the scrubbers also without CEMS.

Figure 9. CEMS accuracy in CO2 measurements

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Figure 10. CEMS accuracy in NOx measurements

Figure 11. CEMS accuracy in SO2 measurements

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Pöyry Finland ppm 0 0 0 0 0 0 0 0

CEMS ppm 2.3 2.3 0.8 0.8 0 0 0 0

Portable instrument ppm 0 0 0 0 0 0 0 0

CO2 after scrubber

Pöyry Finland %-v 4.7 6.1 6.5 6.6 4.6 6 6.4 6.7

CEMS %-v 4.45 5.8 6.15 6.45 4.3 5.65 6.05 6.3

Portable instrument %-v - 5.8 6.13 6.45 4.4 5.8 6.2 6.5

3.4 Sulphur trioxide test SO3 was measured from the exhaust gas after the scrubber, with Pöyry Finland Oy carrying out the measurements. It was determined by applying the method EPA8. SO3 is very difficult to measure; a continuous measurement method is not available. Therefore, the SO3 content in the exhaust gases was measured only with an engine test load of 100 %. The measurement results showed that after the scrubber, no sulphite was detected in the exhaust gas.

Unit Value

Engine test load % 100

Fuel sulphur content % m/m 1.44

Sulphite (SO3-) mg/m3n dry 0

Based on the IMO regulations, SO3 content in the exhaust gas shall not be measured. When considering the results of the EPA8, the approach of IMO is reasonable; SO3 is an exhaust gas parameter not to be monitored.

Table 2. Comparison between different exhaust gas measurement devices.

Table 3. SO3 reduction in scrubber.


3.5 Removal of nitrogen oxides The scrubber NOx removal efficiency was tested during the Suula tests. The NOx reduction was tested with both high and low sulphur fuel and four different scrubber load levels. The average NOx reduction was with high sulphur fuel 8.1 % and with low sulphur fuel 5.3 % (figure 15).

Figure 12. Scrubber NOx reduction.

3.6 Dynamic test A dynamic test was carried out to measure how well the scrubber works during engine power transients. During the test, the engine was exposed to artificially fast load variations in both directions. These results are shown in the chart below. Sulphur dioxide concentration in exhaust gas was continuously practically zero when engine load increased from 200 kW to 440 kW and decreased to zero. The scrubber automation system was able to maintain stable parameters and 100 % SOx reduction throughout all transients.

SCRUBBER NOx REDUCTIONScrubber performance was tested with low sulphur fuel and high sulphur fuel

and on four different scrubber load levels (8, 40, 80 and 100%).

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Figure 13. Wash water pH, exhaust gas CO2 and exhaust gas SO2 historical trend

recorded in dynamic test. The CO2 concentration is load dependent also in steady-state conditions, being an inherent feature of engine aspiration.

3.7 Plume Some of the scrubbing water is evaporated in the scrubber and thus the clean exhaust gas after the scrubber has a high relative humidity, although the absolute water content is lower than in normal exhaust gases without a scrubber. High water content in the exhaust gases may appear as white plume coming out of the exhaust pipe. To minimize the evaporation (and fresh water consumption), the scrubbing water is cooled with sea water in a heat exchanger. This arrangement reduces the visibility of white plume.

A dedicated plume test was done in order to visually evaluate the plume. The test was done in summer 2009 in Porvoo harbour. The engine load was relatively stable during the test and the sea water cooling pump capacity was varied to see the impact on scrubbing water temperature, and consequently on exhaust gas temperature and water content (plume). The test was based on visual observations.

Auxiliary engine no.3 stopped

Wash water pH

CO2 in exhaust gas SO2 content in exhaust

gas (sulphur in fuel)

Load of auxiliary engine no.3

Auxiliary engine no.3 loaded alone

Two auxiliary engines loaded

Shaft generator loaded alone

Auxiliary engine no. 3 running without load


Figure 14. Sea water cooling on (normal operation mode).

Figure 15. Sea water cooling off (abnormal operation mode).

Test conditions:

Engine load 320… 350 kW Ambient air temperature 22… 24 °C

Fuel sulphur content 2.1 % Wind speed 9… 11 m/s

Sea water temperature 9 °C

Based on the observations made during the test, the following was concluded:

Sea water cooling of the scrubbing water has a notable effect on exhaust gas plume.

With normal cooling, the plume is very thin, transparent and very rapidly mixed with the ambient air.

With the cooling switched off, the plume is a thick white cloud, however it does still mix rapidly with ambient air.

During all operating conditions the plume lift was very good. A change was noticed only in the thickness of the plume. Down wash, condensation or acid rain was never detected.


3.8 Noise The noise properties of the scrubber were estimated by sound pressure measurements on the top of the chimney. The layout of the test system made it possible to guide the exhaust gases either through the original silencer or through the scrubber. The sound pressure in both cases was measured in different directions. The average 1/3-octave spectrum of the values at a distance of 2 meters are presented in the results graph.

At low frequencies (12.5 Hz to 100 Hz), the silencing properties of the test scrubber are quite equal to the original exhaust noise silencer. This frequency range is dominant in linear scale (dotted lines in figure 16).

At higher frequencies (1 kHz and upwards), the silencing properties of the test scrubber and the silencer are also equal. The noise in this frequency range is relatively low and thus not significant.

At mid-frequencies (in this case 150 Hz to 1 kHz), the silencer is more efficient than the test scrubber.

However, the highest dominating noise peak at 125 Hz on the A-weighed scale in dB(A) emitted through the original silencer is reduced when conducting the gas through the test scrubber instead of the silencer. Therefore, the scrubber and silencer emitted the same total noise level in terms of dB(A).

The size of the test scrubber is smaller than commercial applications. Therefore it can be expected that the scrubbers in larger commercial installations will show better performance than a silencer at low frequencies (such as the ignition frequency). On the other hand, a slight reduction of the noise attenuation at mid frequencies may be expected.

Figure 16. Sound pressure from the scrubber exhaust pipe.

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Sound pressure 2 m away from the top of the chimneyComparison between the scrubber and the silencer

Silencer, Linear weighing, total = 105 dB

Scrubber, Linear weighing, total = 107 dB

Silencer, A-weighing, total = 80 dBA

Scrubber, A-weighing, total = 80 dBA


3.9 Effluent composition and quality The bleed-off treatment unit removes the accumulated impurities from the scrubbing water. Clean effluent from the unit is discharged overboard. The water treatment unit performance tests were part of a broader testing programme of the Wärtsilä scrubber.

The water quality has been a significant research target and over 70 water samples were taken from the scrubbing water, effluent and technical water. The tests were performed with fuel sulphur content of 1.5 %, 2.2 % and 3.4 %. Also, as a part of the certification tests, the effluent quality was demonstrated to classification societies, showing that the Wärtsilä scrubber fulfils all the effluent quality requirements. The effluent quality tests confirmed that the main component (beside water) in the effluent is harmless sulphate.

Water %-mass >75

Sulphate %-mass <25

Sulphite %-mass <1

Nitrate %-mass <0.2

Nitrite %-mass <0.2

Metals as sum %-mass <0.006

Hydrocarbons as sum C10-C40 %-mass <0.0001

The bleed-off treatment unit cleaning efficiency was excellent regardless of the fuel sulphur content. The reduction of the hydrocarbons C10-C40 and the PAH (Polycyclic aromatic hydrocarbons) was almost 100 % at the bleed-off treatment unit when tested with different fuel sulphur contents.

Continuous measurement of the PAHphe equivalence in a reliable way is challenging using existing technology. Firstly the device has to detect the minimal amount of the specific PAH compound in flowing water, and secondly the device must be capable of measuring the concentration of this compound. Traditional sampling and laboratory analyses onshore are a more reliable approach to monitor the PAH content in effluent. Research work will continue to find best methodology for PAH monitoring in the effluent.

The bleed-off treatment unit removes metals efficiently from the scrubber water. The analysed metals from the effluent are defined in the IMO Resolution MEPC.184(59). The turbidity criterion in the IMO Resolution limits the permissible amount of metals.

Table 4. Main components in the effluent.


Figure 17. Reduction in concentration of chemical components in the bleed-off

treatment unit with fuel sulphur content 3.4 % m/m.

Figure 18. Reduction in concentration of chemical components in the bleed-off

treatment unit with fuel sulphur content 1.5 % m/m.

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REDUCTION OF COMPONENTS IN THE BLEED-OFF TREATMENT UNITFuel sulphur content 3.4 % m/m

Hydrocarbons as sum C10-C40

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PAH-16: Phenanthrene

Metals as sum

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3.10 Tests with water produced in AWP-process Black and grey water from vessels can be treated by using Advanced Wastewater Treatment systems (AWP) that provide biological treatment, solid removal and disinfection. The applicability of the effluent from AWP system as a water source to a SOx-scrubber was tested in June 2009. The test was performed by Turku University of Applied Sciences at the request of Wärtsilä Finland Oy. The purpose of the test was to evaluate potential sensory (smell), microbiological and chemical factors that may affect the usability of AWP water as the water source for Wärtsilä’s SOx- scrubber.

The AWP effluent from a modern cruise ship was collected and used in the field test. During the test run the AWP water was fed into the scrubber system to replace the existing scrubbing water. Various microbial studies were made from the samples taken from the scrubber system before, during and at the end of the test run to reveal the viability of selected bacteria and viruses in the scrubber conditions. Also, chemical analyses were made to follow the changes in the chemical composition of the scrubber water during the test. The chemical and microbiological analyses were performed in the laboratory.

During the test no changes in the SOx-scrubber water composition were found that could make the use of AWP water inapplicable to the scrubber use. These field tests did not reveal any potential negative consequences on human health or comfort.

3.11 Sludge quantity and quality The impurities in the exhaust gas are trapped in scrubbing water. The bleed-off is cleaned in a treatment plant and the cleaned effluent can be discharged into the sea. The impurities are left in the sludge, which is collected into the sludge tank to be emptied into port waste reception facilities. The amount of generated sludge is approximately 0.1 to 0.4 kg/MWh, in other words less than 10 % of ‘normal’ sludge.

Sludge generated in the scrubber process is similar to other engine room sludge, and can therefore be conducted to the same tank. The scrubber sludge may not to be incinerated. Therefore in ships where ‘normal’ engine room sludge is incinerated, the scrubber sludge is conducted to separate sludge tank.

The sludge samples have been taken from the scrubber pilot plant. The samples were analysed in accredited laboratories. The fuel sulphur content during the sludge Sampling was 1.49 % m/m. The following tables represent the typical

Composition and properties of scrubber sludge:

Unit Value Laboratory

Dry matter % 21.3 Nablabs

Table 5. Analysed results from the sludge



pH 5.6 Eurofins

Density kg/l 1.0406 Eurofins

Ash 550ºC % d.m 58.9 Eurofins

Oil Hydrocarbons as sum mg/kg d.m 252000 Eurofins

Metals as sum mg/kg d.m 52977 Eurofins

Calorimetric heat value MJ/kg 17.22 Nablabs

Effective heat value MJ/kg 16.25 Nablabs


PAH-16 sum µg/l 33 Eurofins

Benzene µg/l <d.l Eurofins

Toluene µg/l <d.l Eurofins

Ethylbenzene µg/l <d.l Eurofins

m/p-Xylene µg/l <d.l Eurofins

o-Xylene µg/l <d.l Eurofins

MTBE µg/l <d.l Eurofins

TAME µg/l <d.l Eurofins

Hydrocarbons as sum mg/l 3,8 Eurofins

Chloride (Cl) mg/kg 60 Eurofins

Sulphate (SO4) mg/kg 25600 Eurofins

Nitrate (NO3) mg/kg 157 Eurofins

Nitrite (NO2) mg/kg <d.l. Eurofins <d.l. = below reliable determination limit of analysis method dm = dry matter

The scrubber sludge contains water (79 %) and dry matter (21 %). The composition of the dry sludge is mainly hydrocarbons, ash and metals. The water emulsion contains hydrocarbons, metals and sulphate. Sludge quantity and quality depend on fuel oil quality. Coagulation and flocculation chemicals are added in bleed-off treatment processes, and the composition of such chemicals is reflected in the sludge analysis.

Based on the test results from MT “Suula”, waste reception facilities in Finland and Sweden have confirmed that the sludge from the scrubber bleed-off treatment unit can be safely handled and disposed of in ports in the same way as other sludge from ships’ engine rooms.

It is also technically possible to reduce the water content of the sludge. In this process, sludge from which the water has been removed is packed in sacks.

Table 6. Analysed results from the sludge’s dry matter

Table 7. Analysed results from the sludge’s aqueous phase


3.12 System reliability The system performed well.

The scrubber hull was made of GRP which proved to be an excellent solution in contact with corrosive liquids inside the scrubber. Exhaust gas heat was well under control and no material failures were detected.

Automation and process control was based on Wärtsilä’s diesel engine control components which were known to be robust and reliable. As normal with process automation, the control parameters needed some tuning during the test period. In addition, control interface and programs could be developed.

The standard of the main instruments in the system were “process industry quality” with good corrosion protection. However, some components suffered from low quality. The amount of water and dirt in instrument air is most important for the reliability of pneumatic control components. The CEMS system should be designed to be operated with wet exhaust gases.

Furthermore, mechanical components, for instance pumps and pump shaft sealings, must be selected carefully. Some components and instruments in the scrubber system require regular maintenance.

Ship inclinations, accelerations, vibrations and load transients caused no interruptions to scrubber operation. Rough sea states had no effect on sulphur reduction.

The main challenge for the test scrubber was winter. Suula’s installation was temporary and therefore installed outside the funnel. The running profile of the system was not continuous. Therefore freezing occurred in the scrubber during system lay days. This is not relevant for permanent, commercial scrubbers as they will be installed in warm conditions in the funnel or a similar enclosure.

3.13 Corrosion tests The purpose of the coating test was to determine the tank coating’s resistance to corrosion. Coating samples from three different suppliers were installed in bleed-off water and in Sodium Hydroxide for three months. After the test period, the samples were delivered to coating manufactures for evaluation.

All coating samples endured bleed-off water and Sodium Hydroxide and no corrosion in the samples was detected.


Figure 19. Coating test piece before (left) and after (right) the test.

3.14 Health and safety aspects Wärtsilä scrubber tests onboard the MT Suula did not reveal any potential negative consequences on human health. Several different kind of testing were performed and no dangerous situations or accidents happened thanks to a safety programme. The fresh water exhaust gas scrubber uses a NaOH (Caustic Soda) solution with a maximum concentration of 50 %. Alternatively, a 20 % NaOH solution can be used. NaOH was present in the NaOH bunkering, storage and NaOH feed system on the Suula. During the tests, NaOH was stored and handled safely and no dangerous situations occurred.

Scrubbing water is the water circulating in the system. Water is circulated from the scrubber or a separate process tank through a seawater cooler and back to the scrubber. Scrubbing water is not a health hazard. Also the applicability of the effluent from an Advanced Water Purification (AWP)-type sewage water treatment system as a water source to a SOx-scrubber was tested in June 2009. The test run in this field test revealed no negative findings for human health or comfort.

Particles can be harmful for health. The size of the particles is directly linked to their potential for causing health problems. Small particles of less than 10 micrometers in diameter cause problems because they can get deep into the respiratory system and affect the lungs and heart. The tests confirmed that scrubbed exhaust gases contain less particles than normal exhaust gases.

3.15 Energy consumption The tests confirmed required water pressure and flow rates. Thus it was confirmed that the pumping power requirement of commercial scrubber installations in nominal conditions will be around 0.3 % of the engine power, regardless of the vertical position of the scrubber in the vessel. Additionally, miscellaneous control systems and other devices consume insignificant amounts of electric power in commercial applications.


4 LEGISLATION DEVELOPMENT

4.1 General In this project, the regulations with regards documentation, performance demonstration, onboard verification and certification were thoroughly and successfully tested on the scrubber installed on the MT “Suula”.

4.2 IMO Resolution MEPC.185(59) Continuous PAH monitoring

Continuous measurement of the PAHphe equivalence onboard is challenging. This is due to the small concentrations and limited selectivity of available measurement methods. There are furthermore no existing international standards for measuring PAH compounds on-line.

Traditional PAH measurement methodology

Traditional sampling and laboratory analyses onshore is a more reliable approach to monitor the PAH content in effluent. The effluent samples should be taken for analysis to a laboratory accredited according to the standard EN ISO/IEC 17025.

The traditional tested and standardized method for aqueous PAH determination is a manual analytical laboratory method. In this method, a representative effluent water sample is first extracted with dichloromethane or diethylether (liquid/liquid extraction), then exchanged with hexane over a steam bath and fractionated and purified by alumina/silica gel chromatography.

After the sample preparation described above, PAH compounds are measured by gas chromatography using an ion trap mass selective detector (GC/MS). Method detection limit is about 1- 8 ng/l in water. The calibration of analysis system is done by known concentrations of PAH (internal standards). In this method both gaseous (dissolved) PAH compounds as well as PAH in particles are transferred into extraction solution from which the Total PAH (TPAH) is analyzed by a GC/MS system.

This method is standardized internationally including e.g. the following standards: EPA 3510 (Separatory funnel liquid-liquid extraction), EPA 8310 (Polynuclear aromatic hydrocarbons - analysis and result calculations) and NS9810 (Water analysis - Clean up procedure of water samples for the determination of polycyclic aromatic hydrocarbons (PAH).

Proposal

It is proposed to offer sampling and onshore analysis as a part of certification as an alternative to continuous PAH monitoring in section 10 of Resolution MEPC.184(59), similar to the demonstration procedure for nitrate concentration.


4.3 EU Directive 2005/33/EC The following is worth considering when updating the Directive:

Article 4c, §4, second bullet, “…are fitted with continuous emission monitoring equipment”: When this text was written originally more than five years ago, it was to some extent justified for the reasons mentioned below. Now there is reason to consider making amendments:

1. At that time, the discussion about emission abatement technology focussed purely on sea water (SW) scrubbing. Since then also fresh water (FW) scrubbing (existing technology in many applications, including stationary diesel power plants) has been introduced to the marine market.

2. Emission monitoring can help in determining SW scrubber performance considering variations of sea water composition in different sea areas. In contrast to SW scrubbing, FW scrubbing is completely independent of the sea water composition (alkalinity) and therefore shows no variations in SOx-reduction performance.

3. Since the Directive was written, the IMO has adopted procedures for certifying (type approval) the performance, documentation and verification procedures of a scrubber without continuous emission monitoring systems. This is known as Scheme A in IMO Resolution MEPC.184(59), adopted in July 2009 in MEPC 59. Therefore emission monitoring is no longer necessary to verify the performance of a scrubber.

4. In addition to a robust type approval procedure, scheme A under Resolution MEPC.184(59) also requires a range of parameters to be continuously recorded in a tamper-proof recording device during operation throughout the life-time of the ship. These parameters are listed in §4.4.7, and include a range of scrubbing water and gas pressures and pressure drops, temperatures and flow rates, and combustion equipment load. Additionally §4.4.8 requires daily spot checks of the exhaust gas quality in terms of SOx-emissions. All these together can be considered at least as reliable as a continuous emission monitoring system.

5. Although continuous emission monitoring systems are frequently used in the process industry, monitoring systems of SOx in exhaust gases of a diesel engine is technically a complication. This is well documented in a CIMAC report Number 23 / 2005, Appendix 4, clearly explaining the technical challenges, which also were confirmed in Wärtsilä pilot scrubber tests.

Article 4c, §4, second bullet could e.g. be expanded by adding “…equipment, or can demonstrate required performance documented in an IMO certificate, and…”


5 SUMMARY

5.1 Test target In this project, a new product for ships, a fresh water scrubber, was installed on the MT “Suula”. This scrubber type is capable of working in any sea area regardless of water composition, including brackish waters and harbour areas. The targets of the tests were a demonstration of performance and functionality in marine environment, and to obtain operational experience and certification.

5.2 Test results All test targets were achieved. The measured SOx-reduction was excellent, complying with the most stringent IMO and EU regulations. The effluent fulfilled IMO wash water discharge criteria with good margins.

The test demonstrated that exhaust gas cleaning systems are capable of safe operation and efficient performance onboard a ship in a marine environment, including rolling and pitching at open sea, vibrations, load variations, seasonal changes, etc. No condensation of the exhaust gas plume occurred outside the stack.

The scrubber sludge can be disposed of safely.

5.3 Recommendations Based on the “Suula” tests, the following actions are recommended:

Development of IMO Resolution MEPC.184(59) to include effluent PAHphe monitoring based on sampling and laboratory analysis as an alternative to continuous monitoring.

Harmonization of EU Directive 2005/33/EC regulations with IMO Marpol. Under Marpol, verification of performance and operation can be carried out either with type approval in combination with recording of process parameters, or alternatively with a CEMS.

Product training for ship designers, shipowners and ship staff will be important in the scrubber introduction phase.

5.4 Conclusions The marine exhaust gas fresh water scrubber is ready for introduction onto the market.

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