Particle emissions from ships at berth using heavy fuel oil

235
Particle emissions from ships at berth using heavy fuel oil
Thuy Van Chu1, 2, 3, a, Thomas Rainey1, 2, b, Zoran Ristovski1, 2, c, Ali Mohammad Pourkhesalian1,
2, d
, Vikram Garaniya4, e, Rouzbeh Abbassi4, f, Liping Yang1, 2, 5, g, Richard J. Brown1, 2, h
1Biofuel Engine Research Facility, Queensland University of Technology (QUT), QLD, Australia
2ILAQH, Queensland University of Technology (QUT), QLD, Australia
3Vietnam Maritime University (VMU), Haiphong, Vietnam
4Australian Maritime College (AMC), TAS, Australia
5Institute of Power and Energy Engineering, Harbin Engineering University, Harbin, China
athuy.chuvan@hdr.qut.edu.au
bt.rainey@qut.edu.au
cz.ristovski@qut.edu.au
dalimohammad.pourkhesalian@qut.edu.au
ev.garaniya@utas.edu.au
frouzbeh.abbassi@utas.edu.au
gyangliping302@hrbeu.edu.cn
hrichard.brown@qut.edu.au
Abstract In this study, the composition of exhaust from a marine diesel auxiliary engine running on
Heavy Fuel Oil (HFO) on-board a large cargo vessel was investigated. Measurements of particle
number and size distributions in the range 5-1000 nm and gaseous emissions of O2, CO, CO2, SO2 and
NOx were undertaken. The measurements were performed on two large cargo ships at berth and during
travel. Measurements were also carried out on auxiliary engines of two ships when they were at berth.
Data on engine power, engine revolution, fuel oil consumption, intercooled air temperature, scavenging
air pressure, cooling fresh water and exhaust gas temperature were measured using instrumentation of
the ship. Results showed that emission factors (g/kWh) are higher than that of previous studies for SO2.
This may be due to the high sulphur content of fuel. Particle number size distribution was observed to
be the highest around 35 – 45 nm in diameter, and the particle number remarkably decreased during
higher engine load conditions.
Key words: On-board ship emission measurement, heavy fuel oil, fuel sulphur content, particle number
emission factor, particulate matter emission factor, HFO composition.
1. Introduction
Exhaust emissions from ships have negative effects on both the environment and public health [1-6].
Based on sufficient evidence in 2012, the International Agency for Research on Cancer (IARC), which
is part of the World Health Organization (WHO), classified diesel engine exhaust as carcinogenic to
human health (Group 1, same as asbestos). According to Viana et al. [7], shipping-related emissions are
one of the major contributors to global air pollution, especially in coastal areas. This is obvious because
over 70% of ship emissions may spread up to 400 km inland and significantly contribute to air pollution
in the vicinity of harbors [8]. They may cause an increase in the levels and composition of both
particulate and gaseous pollutants and the formation of new particles in densely-populated regions [7,
9]. Corbett et al. [6] estimated that shipping-related PM2.5 emissions are the causes of approximately
60,000 deaths globally associated with cardiopulmonary and lung problems yearly. Continued
implementation of the amendments to the Maritime Pollution Convention (MARPOL) Annex VI
regulations is a good way to reduce ship emissions, however, further regulation should be implemented
because a fuel shift to low sulphur alone seems to be not enough to reduce fine and nano-particle
emissions [10]. Quantitative and qualitative estimation of pollutant emissions from ships and their
dispersion thus are becoming more important [4]. However, a very limited number of on-board
measurement studies are found in the literature [4, 11].
Heavy Fuel Oil (HFO), which contains many impurities including sulphur, ash, vanadium, and nickel,
is the main fuel for up to 95% of 2-stroke low-speed main engines and around 70% of 4-stroke medium-
speed auxiliary engines [12] owing to its economic benefit [2]. Different compounds like sulphate,
organic carbon (OC), black carbon (BC), ash and heavy metals in emitted particles are associated with
236
HFO combustion [13, 14]. In practice, while gaseous emissions have been extensively studied over
several decades, diesel engine fine and nano-particles have recently emerged as a major health concern
and received more attention from researchers and port managers.
The aim of this study is to investigate the particle emissions with respect to number concentration and
size distribution, from an auxiliary marine engine using HFO (3.13 wt% S) when the ship is at berth.
The auxiliary engine operates at a constant speed, with different engine load conditions.
2. Ship Emission On-board Measurement Campaign
The measurements were performed in October and November 2015 on two large cargo ships of CSL
shipping company at Ports of Brisbane, Gladstone, and Sydney. The work was a collaboration of the
Australian Maritime College (AMC), Queensland University of Technology (QUT), and Maine
Maritime Academy (MMA). The first on-board measurement was performed on Vessel I from 26th to
31st of October, 2015 when she was running from Port of Brisbane to Port of Gladstone. The second
measurement was conducted on Vessel II from 03th to 06th of November, 2015 in her voyage from
Gladstone to Newcastle. All measurements have been carried out on both main and auxiliary engines
of two ships for different operating ship conditions, such as at berth, manoeuvring, and at sea.
The on-board measurement presented in this paper was performed on the auxiliary engine of Vessel II.
Instruments were arranged on a deck high up in the machinery room and the exhaust gas was sampled,
and measured continuously from a hole cut in the exhaust pipe after turbocharger of auxiliary engine
No.1. The details of the measured engine can be seen in Table 1. At the sample point, one hole was
created for the present measurements using a Testo 350XL and a DMS 500. The Testo 350XL was
calibrated on 10th, August 2015 by the Techrentals Company and was ... 501 0
Carbon residue % mass ISO 10370 14.65 Nickel mg/kg IP 501 34
Total sediment % mass ISO 10307 0.03 Calcium mg/kg IP 501 10
Calorific value MJ/kg IP 501 40.22 Zinc mg/kg IP 501 1
Asphaltenes % mass IP 143 7.42 Potassium mg/kg ASTM
D5185
0.8
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Figure 2 Auxiliary engine at berth: (a) Gas concentrations measured NOx, CO, SO2, O2 and
CO2; (b) Particle number and mass concentrations; (c) The relationship between engine speed,
engine power with period of measurement time.
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Emission factors for emitted gas-phase species and number/mass of particles were calculated following
ISO 8178 [15, 16], using specific fuel consumption and formed CO2 to obtain the exhasut gas flow rate
(equation (1)). These calculations assume that all carbon in the fuel is converted completely into CO2.ℎ = × (%) × ( )× ( , , ) [ ] (1)= × [ ] (2)
= × [ # ] (3)
where CCO2, exh and CCO2, air are the CO2 concentration in v/v % in the exhaust gas and in the air,
respectively. Data on fuel consumption and engine power were obtained from the ship’s instrument.
The emission factors of both gases and particulate matter are presented as mass or number per kWh of
engine work (g/kWh, #/kWh), and normalised to standard conditions regarding temperature of 273.15
K and pressure of 101.325 kPa.
20 40 60 80 100
0
5
10
15
20
Em
iss
io
n
 F
a
ct
o
rs
 (g
/k
W
h)
Power (%)
 O2/100 CO CO2/100 SO2 NOx PM1.0
Figure 3 Specific emissions against engine load. (A 95% CI for each mean value is shown as the
mean ± X)
3. Results and Discussion
The major gaseous emissions of interest in the engine exhaust were NOx, CO, SO2, O2, and CO2. The
real-time on-board measurement of these gases can be seen in Figure 2a. Figure 2 demonstates the
relationship between the changes of emisions with time and engine power output while engine speed is
kept at a constant value. The results of gas-phase emision factors for O2, CO, CO2, SO2, and NOx in
terms of g/kWh are presented in Figure 3. There was an initial peak in CO concentration at start-up in
cold start period - this can be seen in Figure 2a and 3. This is due to the cold start of the engine and the
low engine load condition, which leads to incomplete combustion and aids carbon monoxide to gain
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the highest level. The CO concentration then significantly decreased and remained at a stable value at
high engine load condition.
Table 3 Comparison of gaseous emissions between this study and previous studies.
Study Engine Type Fuel
(% S)
Engine
Load
(%)
O2
(g/kWh)
CO
(g/kWh)
CO2
(g/kWh)
SO2
(g/kWh)
NOx
(g/kWh)
Moldanová
et al. [17]
4-stroke,
medium speed,
main engine,
4440 kW
HFO
(1.0)
30
80
1127
1054
1.82
1.17
617
678
3.24
3.65
9.6
9.6
Khan et al.
[18]
2-stroke, low
speed, main
engine, 36740
kW
HFO
(3.14)
29
52
73
81
-
-
-
-
0.57
0.41
0.36
0.35
577
555
561
576
11.4
10.9
11.0
11.3
19.5
18.5
19.5
19.1
Winnes
and Fridell
[10]
4-stroke,
medium speed,
main engine,
4500 kW
HFO
(1.6)
50
70
90
-
-
-
1.05
0.74
0.3
620
603
607
4.62
4.62
4.57
7.49
8.49
10.71
Agrawal et
al. [19]
2-stroke, low
speed, main
engine, 15750
kW
HFO
(2.85)
13
25
50
75
85
-
-
-
-
-
2.5
1.5
1.0
0.8
0.5
~1200
640
620
670
680
13
12
10.5
10
10
22
17
18
21
20.5
Cooper
[20]
4-stroke,
medium speed,
auxiliary
engine, 1270
kW
HFO
(0.53)
47-58 - 1.06 -
1.71
763-803 2.5-2.7 13.3 -
17.5
4-stroke,
medium speed,
auxiliary
engine, 2675
kW
HFO
(2.2)
41 - 0.90 691 9.5 15.2
4-stroke,
medium speed,
auxiliary
engine, 2005
kW
HFO
(2.2)
39 - 0.77 697 9.6 12.9
This study 4-stroke,
medium speed,
auxiliary
engine, 425 kW
HFO
(3.13)
24
35
55
70
83
95
1338
1208
1150
1104
969
992
2.81
1.66
1.14
1.16
0.88
0.87
850
850
849
849
849
849
22.20
22.49
22.30
21.24
21.17
21.11
4.40
5.17
6.40
6.30
6.91
7.14
A significantly decreasing trend of O2 emissions with power was observed as shown in Figure 2a and
3. This may be due to the engine revolution being constant, which makes the amount of air stable while
the engine load is increased. Thus, more fuel is required and a rich fuel-air mixture combustion
condition is reached. The fuel-dependent specific emissions of SO2 and CO2 is given in Figure 2a are
generally proportional to the fuel carbon and sulphur content, and therefore these emission factors of
SO2 and CO2 seem to be constant as was expected. Of most interest in this study is that the emission
factor of SO2 was much higher than that of compared studies (Table 3), which is the result of higher
sulphur content fuel used in this research. The theoretical value of SO2 emission factor calculated in
this study was around 16.6 g/kWh, which was significantly less than measured cases. The emission of
NOx depends on the engine temperature, and thus the emission of NOx presented in Figure 2a and 3
shows a dependence on engine load in which high engine load produces the highest emission. Shown
241
in Table 3, the value of NOx emission in the present research was much lower than that of previous
studies, this may be due to difference engine types and working conditions.
For particle emissions presented in Figure 2b, a general pattern in the emitted nanoparticles is that there
was an initial peak both in mass and number concentration at engine start-up in cold start period before
reaching the constant value or significantly decreasing to low level at higher engine load working
condition. This can be seen clearly in PN case, a significant difference in particle number concentrations
observed between low and medium engine load of 0, 24, 35 and 55% with 70, 83 and 95% of engine
load working conditions, which illustrated in Figure 2b and 4. This may be due to low temperature
inside engine combustion chamber at low loads, which caused more particles can be created [3]. Figure
4 indicated that the number size distributions were dominant by nano-particles and only one modal with
the peak at around 35 – 45 nm for all engine load working conditions. Particle mass emission factor
(PM) was calculated from the number concentrations measured with the DMS 500 (5.0 – 1000 nm)
assuming spherical particles with unit densities for nucleation and accommodation mode. A 95%
confidence interval (CI) to each mean value in Table 4 was calculated.
1 10 100 1000
0.00E+000
3.00E+008
6.00E+008
9.00E+008
1.20E+009
1.50E+009
1.80E+009
dN
/d
lo
gD
p
(#/
cm
3 )
Particle Diameter (nm)
0%
24%
35%
55%
70%
83%
95%
Figure 4 Number size distributions of measured particles (5-1000 nm) for idle, 24%, 35%, 55%,
70%, 83%, and 95% load.
In comparison with the literature that can be seen in Table 4, there is a large variation of particle number
emission factor, which may be due to limited available data on PN and a difference in fuel used, engine
models, working conditions, and instruments used for PN measurement [21]. A decreasing trend of both
PN and PM emission factors was observed clearly as engine output power increased in this study. This
trend was also observed in the study of Anderson et al. [3], but particle number emissions at 10 and
25% load in this study (HFO, 0.12 wt% S) were much higher than that of present study (HFO, 3.13 wt%
S). This shows that a fuel shift to low sulphur content fuel may only have limited effect on small size
particle number concentrations. It can be supported by studies of Winnes and Kasper [10, 22].
Magnitude of PM emission factor in this study was rather similar to that of previous studies.
242
Table 4 Comparison of PM and PN between this study and previous studies. (A 95% CI for
each mean value is shown as the mean ± X)
Study Engine Type Fuel
(% S)
Engine
Load (%)
PN
(1016 #/kWh)
PM (g/kWh)
PM10 PM2.5 PM1.0
Moldanová
et al. [17]
4-stroke,
medium speed,
main engine,
4440 kW
HFO (1.0) 30
80
- 0.35
0.41
- 0.27
0.41
Khan et al.
[18]
2-stroke, low
speed, main
engine, 36740
kW
HFO
(3.14)
29
52
73
81
- - 1.19
1.44
2.14
2.19
-
Hallquist
et al. [21]
4-stroke,
medium speed,
SCR-equipped
main engine,
12600 kW
HFO
(0.49)
75 2.05 ± 0.27 - - 0.13 ± 0.02
Anderson
et al. [3]
Test-bed engine,
4-stroke, 5-
cylinder, high
speed, 81 kW
HFO
(0.12)
10
25
35
12 ± 0.04
17 ± 0.059
0.17 ± 0.003
- - 0.45±0.025
0.71±0.11
0.65±0.03
This study 4-stroke,
medium speed,
auxiliary engine,
425 kW
HFO
(3.13)
24
35
55
70
83
95
0.468 ± 0.013
0.450 ± 0.009
0.501 ± 0.025
0.310 ± 0.013
0.290 ± 0.011
0.281 ± 0.012
- - 1.221 ± 0.198
0.585 ± 0.064
0.423 ± 0.009
0.473 ± 0.020
0.424 ± 0.013
0.421 ± 0.011
4. Conclusion
Although in-port auxiliary engine emissions account for a relatively small proportion of the total
emissions from shipping compared to main engine emissions, they have some of the most significant
health effects on the surrounding population [20]. To improve the limited knowledge regarding marine
engine emissions [21], especially on particle number size distribution, a measurement campaign on two
commercial ships plying the east coast of Australia was conducted as described in this study. Engine
performance and emissions of an auxiliary engine while in berth, were measured on-board the ship
during actual harbour stopovers. The focus was directed toward characteristics of particle emissions.
Gaseous and particle emission factors were presented in g/kWh or #/kWh, and investigated at different
engine loads while engine speed is kept at constant value. The particle number size distribution was
peaked at around 35 – 45 nm and dominant by nano-particles, which have negative impact on human
health and climate.
5. Acknowledgement
The authors gratefully acknowledge the Port of Brisbane Corporation for their ongoing support in the
project, Maritime Safety Queensland and stevedore operators (AAT, Patricks and DP World). The
authors would like to acknowledge the outstanding support received from all employees and crew of
CSL Group Inc. in coordinating this project. In addition, the materials and data in this publication have
been obtained through the support of the International Association of Maritime Universities (IAMU)
and the Nippon Foundation in Japan.
243
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