marine engines emission and dispersion in fuel switching operation a case study for the port of naples

doi: 10.1016/j.egypro.2016.11.047 Energy Procedia 101 2016 368 – 375 ScienceDirect 71st Conference of the Italian Thermal Machines Engineering Association, ATI2016, 14-16 September

1876-6102 © 2016 The Authors Published by Elsevier Ltd This is an open access article under the CC BY-NC-ND license

( http://creativecommons.org/licenses/by-nc-nd/4.0/ ).

Peer-review under responsibility of the Scientific Committee of ATI 2016.

doi: 10.1016/j.egypro.2016.11.047

Energy Procedia 101 ( 2016 ) 368 – 375

ScienceDirect

71st Conference of the Italian Thermal Machines Engineering Association, ATI2016, 14-16

September 2016, Turin, Italy Marine engines emission and dispersion in fuel switching operation:

a case study for the port of Naples Giuseppe Langella, Paolo Iodice*, Amedeo Amoresano, Adolfo Senatore

Dipartimento di ingegneria Industriale, Università degli Studi di Napoli Federico II, Via Claudio 21, Naples 80125, Italy

Abstract

This study analyses the production and the dispersion of air pollutants produced by ship engines of great displacement during the approaching phase to the seaports In agreement with the present environmental rules, several scenarios were examined, considering the possibility of fuel switch, from heavy fuel oil to marine gasoil After characterizing the emissions during this fuel change-over, and taking into account the most frequent routes, we analyzed the specific case of the port of Naples For this case-study we evaluated different scenarios of pollutants dispersion from ships arriving and departing, by using the Gaussian model ISC and considering in particular the effect on the coastal zone adjacent to the port The results are represented graphically and provide valuable insights about the impact of marine traffic on air quality Such information may be seen as useful tools for the improvement of maritime legislation on emissions, since emission of air pollutants from ships of large size is a key factor in air quality state in the surrounding areas to ports

© 2016 The Authors Published by Elsevier Ltd

Peer-review under responsibility of the Scientific Committee of ATI 2016

Keywords:Marine diesel engines; pollutant emission and dispersion; fuel change-over

1 Introduction

Marine transport is a vital sector for the global economy since over 80% of freight is transported by ships [1] That is also the most energy efficient and sustainable mode of transportation of goods from an environmental perspective, whereas CO2 emissions required to carry a ton of freight per kilometer by sea are just 25% of those on

* Corresponding author Tel.: +390817683277; fax: +39081 2394165

E-mail address: paolo.iodice@unina.it

© 2016 The Authors Published by Elsevier Ltd This is an open access article under the CC BY-NC-ND license

( http://creativecommons.org/licenses/by-nc-nd/4.0/ ).

Peer-review under responsibility of the Scientific Committee of ATI 2016.

road transport for the same distance, and only 1% of those provided by the air transport Ports represents certainly a concentrated area of marine transport, so they are a major and growing source of pollution, and can impose significant health risks on nearby communities [2]

Emissions by ship traffic are becoming a significant source of air pollution in cities near major ports, also considering widespread actions world-wide to reduce emissions deriving from road transport sector during the last years [3]-[5] Recent evaluations of global sulfur and nitrogen oxide emissions from international shipping report 6.49 Tg S and 6.87 Tg N, respectively [6] Although ship emissions nowadays constitute only a small fraction of total global emissions, they could have relevant environmental influence on coastal areas near ports with heavy ship traffic as highlighted in studies for regions in Europe, Asia and North America [7]-[12]

However, today ships represent a major unregulated source category Furthermore, emissions from shipping activities are growing Ship emissions will increase significantly in next 10–40 years owing to expanding international commerce [13] As a result, it is necessary to understand atmospheric impacts of these emissions, especially on regional air quality

This study evaluates the environmental impact of ship emissions on the coastal zone nearby the port of Naples (South Italy) which is one of the busiest Italian port In particular, the study covers emissions from large size two-stroke diesel engines, taking into account the fuel change-over from heavy fuel oil (HFO) to marine gasoil (MGO) and vice-versa, moving toward and away from the port In order to calculate the polluting concentrations from ships and to assess the resulting air quality state in the area surrounding the port of Naples, this analysis was carried out by using the Gaussian model ISC The modelling approach presented in this study can be considered as an important assessment tool for the local environmental authorities [14], since it can be applied in order to evaluate both the compliance of air quality with the limit values established by current legislation, and the influence of various scenarios of pollutant emission from arriving and sailing ships on the local air quality state

2 Ship emission and fuel change-over

As widely known, the air emissions from marine traffic are regulated by Annex VI of MARPOL 73/78 (Marine Pollution), promulgated by the IMO in 1997 and subsequently amended This regulation has been transposed in Europe by Directive 2005/33/ EC and in Italy by DM 205 of 6 November 2007 In particular, these regulations govern SOx and NOx emissions which are present in the exhaust gases of internal combustion engines for ships of large size

The limits on the emission of SOx are two, one more compelling relative to ports and SECA areas and one less compelling relative to all other areas Ships that do not have systems to reduce SOx emissions, such as sea water scrubbers, must therefore be prepared using two different types of fuel, HFO and MDO (or MGO), the first for areas not subjected to emission control, the second for emission control areas and ports

When a ship is going to pass through an emission control area, it has to start a fuel change over procedure, in time and in such a way that the engine will be burning MGO at the inlet of the area

Fuel change-over must be performed carefully in order to avoid engine failure [15],[16] There is not a universal procedure to do it but some items must be monitored:

x Fuel viscosity must be kept within the range 2-20 cSt;

x Fuel temperature variation rate at fuel pump inlet, should not exceed 2°C/minute

A low value of viscosity can cause:

x reduced lubricant effectiveness, resulting in excessive wear and possible failure of the injection pump;

x fuel leaks from pumps, valves and piston rings, preventing the ship to reach the maximum power

About the temperature of the fuel, typically, HFO is heated to about 150 °C and has to be changed to MGO, used

at about 40 °C, so the temperature gap is about 110 °C Considering the allowed rate of change of 2 °C/minute, the process of replacing the fuel should last a minimum 55 minutes to carry out safely

A quick change from HFO to MGO can cause overheating of MGO which causes a rapid loss of viscosity and gassing in the fuel system Likewise, a too rapid a change from unheated MGO to HFO can lead to excessive cooling of HFO and therefore excessive viscosity to the injectors resulting in possible loss of power or shutdown

Therefore it is recommended to make the change of fuel with the engine at low power levels The load, however, should not be too low otherwise the mixing time of HFO and MGO in the service system increases with a consequent risk of precipitation of asphaltenes, clogging of filters and therefore loss of power or engine failure Once the propulsion system has stabilized with the use of new fuel and all the components are at normal operating temperatures, the propulsion plant can be brought back to the normal power level and the ship can proceed in port areas and in those subject to restrictions

Another issue related to the use of low sulphur fuels, is the need to use a lubricating oil with different Base Number (BN) Because of the high acid levels on the cylinder liner when using heavy fuel oil with a 2% sulphur content, a lubricating oil with BN (or TBN) of about 70 is recommended Such BN value ensures the neutralization

of sulphuric acid (H2SO4) and sulphur trioxide formed by SO2 and SO3 In case of long-term operation with low sulphur fuels, it is recommended to switch to a lubricating oil with BN (or TBN) 40 or 50 It is generally recommended to use a lubricant with BN (or TBN) 40 50 or even for the short term operation if the sulphur content

is less than 1%

Before starting the changeover procedure form HFO (120 °C) to MGO (room temperature) it is necessary to close the fuel heating lines until the output temperature at the fuel pumps decreases from 120° C to about 80 °C; it takes about 2-3 hours In order to protect the fuel injection system against rapid temperature changes, which can cause the bonding of the fuel valves, piston fuel pump and intake valve, the changeover is performed as follows:

x preheating of diesel fuel in the tank at about 50 °C, if possible;

x interruption of steam to fuel preheating system;

x reduction of engine load at 3/4 load MCR (Maximum Continuous Rating);

x transition to MGO when the heavy fuel oil temperature in the preheater has dropped by about 25 °C but, in any case, not less than 75 °C

So, in summary, in order to complete the fuel change-over, assuring that all HFO residue is consumed in the fuel system, the procedure must begin, in general, at least 3 hours before the SECA area and the fuel line should be started to be heated at least 2/3 hours before the start of procedure

3 Case study: the port of Naples

The present work has been focused on pollutant emitted by merchant ships transiting in the port of Naples Analysis domain (Fig.1) is a 10 km x 10 km area including the piers for large ships, the coastal area adjacent and the sea area interested by ship manoeuvres approaching the port The domain has been discretized with a 32x32 elements square grid and three main routes have been considered for ships entering and exiting the port We used a Gaussian model ISC [17] to assess the production and dispersion of NOx, SOx and PM along the routes

The meteorological data needed to run these simulations like wind speed, wind direction, temperature, humidity, etc., properly processed, were collected at the Naples airport weather station;

However, in general the modelling approach adopted has certain inherent limitations, both concerning the evaluation of emissions and atmospheric dispersion Gaussian dispersion modelling, in fact, does not allow for the detailed structure of buildings and obstacles, and in general for complex orography; the computed concentrations should be interpreted as spatially averaged values, while for instance, inside a street canyon the actual concentrations can vary substantially On the other hand, the use of fairly simple dispersion model facilitates the evaluation of the hourly time series of meteorological and emission conditions for one year, which is required for the computation of statistical concentration parameters, defined in national health-based air quality guidelines This modelling approach, therefore, can be considered as an important assessment tool for the local environmental management, because it can be applied in order to assess the compliance of air quality with the guidelines and limit values (together with the measured concentrations) and the influence of various emission activities on air quality

Fig 1 The port of Naples and the analysis domain

The chimneys of the vessels are not fixed but moving sources, so they have been simulated by a number (60, 20 for each main route) of fixed emission sources along the main routes, emitting the same total amount of NOx, SOx and PM produced by the ship traffic

Starting from traffic data acquired by Maritime Coastal Authority of the Port of Naples, we consider about 10500 (2014 data) ships entering the port in a year That means 30 ships entering and 30 ships leaving in a day

The total emission of each pollutant emitted in the in a day area, i.e for NOx, can be calculated by:

ܧேை௫ǡௗሾ ௚

ௗ௔௬ሿ ൌ ܧேை௫ሾ ௚

௞ௐ௛ሿ ή ܲሾܹ݇ሿ ή௅ሾ௞௠ሿ

௩ቂೖ೘೓ቃή ݊௦ሾ ଵ

ௗ௔௬ሿ (1)

where ܧேை௫ is the emission rate of the ship engine, P is the actual power rate of the ship engine, L is the route length, v is the ship velocity along the route and n s is the total number of ships crossing the area in a day (30 + 30 in the case study)

We considered that ships entering and leaving the port have the main engine at 25% of its power rate and a low velocity of about 5 miles per hour (9 km/h) Spreading the total emission along the routes, each virtual source point emits continuously with the following rate:

ܧேை௫ǡ௩௦௣ሾ௚

௛ሿ ൌாಿೀೣǡ೏ሾ

೒

೏ೌ೤ ሿ

Once known the emission rates of NOx, SOx and PM, the average height and diameter of the chimneys, the average temperature and speed of the exhaust gas, the model provided the concentration maps of such pollutants

above the entire domain (10 km x 10 km) Three cases have been examined, as reported:

1 HFO Case Burning HFO (0,6% Sulphur content) during the whole approaching manoeuvre to the port; in this case the fuel changeover takes place within the port;

2 HFO-MGO Case Gradual fuel switch from HFO to MGO during the whole approaching manoeuvre;

3 MGO Case Burning MGO (0,15 Sulphur content) during the whole approaching manoeuvre to the port; in this case the fuel changeover takes place before the approaching manoeuvre

For the second case, we assumed a linear variation of emission rates between the values assumed for HFO and MGO

In order to evaluate different scenarios of pollutants dispersion from ships arriving and departing, the specific model suggested for this investigation is the Gaussian model ISC Its mathematical formulation is frequently used to simulate the horizontal and vertical dispersion of air pollutants downwind from the emissive sources [18] Gaussian model deals dispersion of air pollutants as being carried downwind in a definite plume, under vertical and horizontal mixing in the neighbouring atmosphere; the plume of air pollutants diffuses vertically and horizontally, with a consequent decrease in concentration as it moves downwind Besides, mixing with the nearby atmospheric air is greatest on the border of the plume, so causing lesser concentrations outward from the centre of the plume, and this decrease in pollutant concentration outward from the centre is studied through a “normal” statistical distribution Analysis domain is a 10 km x 10 km area comprising the piers for large ships, the coastal area adjacent and the sea area interested by ship manoeuvres approaching the port This domain was discretized with a 32x32 elements square grid and three main routes were considered for ships entering and leaving the port The gas atmospheric dispersion was analysed on this particular domain characterized by receptors positioned at 2 m altitude Under these conditions, the application of the dispersion model determined the pollutant concentrations due to the arriving and sailing ships The main results of the simulations provided by the model are shown in the maps of the following figures, in which it’s possible to evaluate the average concentrations in μg/m3 of NOX at ground level in the form of iso-concentration lines for the examined cases

Fig 2 NOx concentration HFO Case

Fig 3 NOx concentration HFO-MGO Case

Fig 4 NOx concentration MGO Case

Similar simulations have been provided by the model for the average concentrations of SOX and PM in μg/m3 By the analysis of results the HFO-MGO case gives better results than those expected across the coastal zone This can

be recognized by comparing Figure 5 and Figure 6 In Figure 5 it is reported the average concentration value of the specific pollutant above the whole domain, while Figure 6 reports the same parameter but only across the coastal zone

Across the coastal area, the average concentrations of NOx, SOx and PM for the HFO-MGO Case, does not have

a linear reduction as it was presumed and as it is for the whole domain Therefore the change of the fuel during the entrance to the port involves a considerable benefit , greater than that expected, in terms of reducing the concentrations of SOx, NOx and PM

Fig 5 Average pollutant concentrations over the whole analysis domain against fuel type

Fig 6 Average pollutant concentrations over the coastal area against fuel type

Acknowledgements

We are very grateful to the Port Authority of Naples for the information provided about the maritime traffic and

to MAN Diesel for data related to engine emissions at part load and for different fuels

References

[1] Fuglestvedt JS, Shine KP, Berntsen T, Cook J, Lee DS, Stenke A, Skeie RB, Velders GJM, Waitz I.A Transport impacts on atmosphere and climate: Metrics Atmospheric Environment 2010;44:4648–4677

[2] Bailey D, Solomon G Pollution prevention at ports: clearing the air Environmental Impact Assessment Review 2004;24:749–774

[3] Iodice P, Senatore A Appraisal of pollutant emissions and air quality state in a critical Italian region: Methods and results Environmental Progress and Sustainable Energy 2015;34:1497-1505

[4] Iodice P, Senatore A Exhaust emissions of new high-performance motorcycles in hot and cold conditions International Journal of Environmental Science and Technology 2015;12:3133-3144

[5] Iodice P, Senatore A Influence of ethanol-gasoline blended fuels on cold start emissions of a four-stroke motorcycle Methodology and results SAE Technical Paper 2013;2013-24-0117

[6] Corbett JJ, Koehle HW Updated emissions from ocean shipping Journal of Geophysical Research 2003;108 (D20),4650

[7] Vutukuru S, Dabdub D Modeling the effects of ship emissions on coastal air quality: A case study of southern California Atmospheric Environment 2008;42(16):3751–3764

[8] Dore AJ, Vieno M, Tang YS, Dragosits U, Dosio A, Weston KJ, Sutton MA Modelling the atmospheric transport and deposition of sulphur and nitrogen over the United Kingdom and assessment of the influence of SO 2 emissions from international shipping Atmospheric Environment 2007;41(11):2355–2367

[9] Derwent RG, Stevenson DS, Doherty RM, Collins WJ, Sanderson MG, Johnson CE, Cofala J, Mechler R, Amann M, Dentener FJ The contribution from shipping emissions to air quality and acid deposition in Europe AMBIO 2005;34(1):54–59

[10] Endresen O, Sorgard E, Sundet JK, Dalsoren SB, Isaksen ISA, Berglen TF, Gravir G Emission from international sea transportation and environmental impact Journal of Geophysical Research 2003;108 (D17),4560

[11] Lu G, Brook JR, Alfarra MR, Anlauf K, Leaitch WR, Sharma S, Wang D, Worsnop DR, Phinney L Identification and characterization of inland ship plumes over Vancouver Atmospheric Environment 2006;40(15):2767–2782

[12] Streets DG, Guttikunda SK, Carmichael GR The growing contribution of sulfur emissions from ships in Asian Waters, 1998–2005

Atmospheric Environment 2000;34,4425–4439

[13] Eyring V, Kohler HW, Lauer A, Lemper B Emissions from international shipping: 2 Impact of future technologies on scenarios until 2050 Journal of Geophysical Research 2005;10(D17),D17306

[14] Iodice P, Senatore A Environmental assessment of a wide area under surveillance with different air pollution sources Engineering Letters 2015;23(3):156-162

[15] Operation on Low Sulphur Fuels, MAN Diesel & Turbo.5510-0075-01ppr , Denmark, Sep 2014

[16] Preparing for Low Sulphur Operation, Technical update, DNV GL Maritime, 11/2014

[17] US EPA, United States Environmental Protection Agency User’s guide for the ISC3 DISPERSION MODELS Epa-454/B-95-003b, US EPA OAQPS, Research Triangle Park, NC, 1995

[18] Iodice P, Dentice d'Accadia M, Abagnale C, Cardone M Energy, economic and environmental performance appraisal of a trigeneration power plant for a new district: Advantages of using a renewable fuel Applied Thermal Engineering 2016;95:330–338