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Comparison of particulate matter and polycyclic aromatic hydrocarbons in emissions from IDI-turbo diesel engine fueled by palm oil–diesel blends during long-term usage
Atmospheric Pollution Research xxx (2016) 1e7
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Original Article
Comparison of particulate matter and polycyclic aromatic hydrocarbons in emissions from IDI-turbo diesel engine fueled by palm oilediesel blends during long-term usage Khamphe Phoungthong a, *, Surajit Tekasakul a, **, Perapong Tekasakul b, Masami Furuuchi c a
Department of Chemistry, Faculty of Science, Prince of Songkla University, Songkhla 90112, Thailand Energy Technology Research Center (ETRC) and Department of Mechanical Engineering, Faculty of Engineering, Prince of Songkla University, Songkhla 90112, Thailand c Graduate School of Natural Science and Technology, Kanazawa University, Kanazawa 920-1192, Japan b
a r t i c l e i n f o
a b s t r a c t
Article history: Received 24 June 2016 Accepted 10 October 2016 Available online xxx
We examined particulate matter (PM), polycyclic aromatic hydrocarbons (PAHs), and carcinogenic potencies of benzo[a]pyrene equivalent (BaPeq) emissions from an indirect injection (IDI-turbo) diesel engine fueled by commercial diesel (PB0) and palm oil blends with portions of 40 and 50 vol.% (PB40 and PB50). The engine was in operation over long-term test cycles. A four-stage cascade impactor air sampler was used to collect particles emitted from the engine. The PM and PAHs were predominantly fine particles (<1 mm) and show an accumulation mode. The total emissions of the IDI-turbo diesel engine increased when the operation times were increased. The mass fractions of 2e3 rings PAHs using PB0, PB40, and PB50 contributed 35.5%e40.6%, 44.7%e50.2%, and 45.9%e51.4%, respectively; for PB0 2e3 ring PAHs contributed less than palm oil blends. Using PB40 and PB50 caused a higher emission of lower molecular weight PAHs than PB0. However, the mass fractions showed that the concentration of 4e6 ring PAHs increased when the running time of the engine was increased for all three fuels. The results in this study showed that significant emissions of PM, PAHs, and BaPeq were reduced as the fraction ratio of palm oil was increased because palm oil blends have a high amount of oxygen, which enhances combustion compared to PB0. Although PM, PAHs, and BaPeq emissions of PB50 were less than those of PB0 and PB40, PB50 is not an appropriate fuel for the long-term running of this engine. Copyright © 2016 Turkish National Committee for Air Pollution Research and Control. Production and hosting by Elsevier B.V. All rights reserved.
Keywords: Diesel engine Diesel emissions Mixed crude palm oil Particulate matter Polycyclic aromatic hydrocarbons
1. Introduction Rapid urbanisation has brought with it two major problems: environmental pollution related to petroleum fuel consumption and the management of petroleum as a major source of energy. The price of oil on the world market is unstable, making imported petroleum a critical element in the supply of energy. Consequently, alternative sources of energy to petroleum have become of increasing interest. With the rapid growth of agricultural resources
* Corresponding author. Fax: þ66 74 558 841. ** Corresponding author. Fax: þ66 74 558 841. E-mail addresses: [email protected] (K. Phoungthong), [email protected] (S. Tekasakul). Peer review under responsibility of Turkish National Committee for Air Pollution Research and Control.
for biodiesel production, the search for a diesel substitute has gained momentum. In general, the physicochemical properties of palm oil meet the requirements of diesel engine combustion (Leevijit and Prateepchaikul, 2011; Phoungthong et al., 2013). Recently, several publications (Kalam and Masjuki, 2004; Lin et al., 2006a; Leevijit and Prateepchaikul, 2011; Phoungthong et al., 2013) have considered the use of palm oil blends for use in diesel engines as an appropriate solution for reducing both imports of petroleum and environmental problems. Diesel engines are in widespread use in Thailand and many other countries, and their numbers are predicted to increase in the future due to their availability and durability (Mwangi et al., 2015a). But, automotive diesel engine emissions are regarded as a major source of anthropogenic air pollution, even though compression ignited engines produce fewer total engine exhaust emissions than ^a et al., 2016). spark ignited engines (Gogoi et al., 2015; Corre
http://dx.doi.org/10.1016/j.apr.2016.10.006 1309-1042/Copyright © 2016 Turkish National Committee for Air Pollution Research and Control. Production and hosting by Elsevier B.V. All rights reserved.
Please cite this article in press as: Phoungthong, K., et al., Comparison of particulate matter and polycyclic aromatic hydrocarbons in emissions from IDI-turbo diesel engine fueled by palm oilediesel blends during long-term usage, Atmospheric Pollution Research (2016), http:// dx.doi.org/10.1016/j.apr.2016.10.006
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Crucially, diesel emissions vary according to fuel and vehicle type, engine technology, and tuning, maintenance and driving behav^a and Arbilla, 2006; Corre ^a et al., 2016; Mwangi et al., iours (Corre 2015a; Topinka et al., 2012). Diesel engines emit a large amount of fine-particles containing a lot of chemical compounds. Some of them are carcinogenic and mutagenic components, for example, aldehydes, ketones, benzene, and polycyclic aromatic hydrocarbons (PAHs) (Tsai et al., 2014; Jedynska et al., 2015; Mwangi et al., 2015a). These pollutants can react with sunlight to produce secondary pollutants, especially peroxy-acetyl nitrate (PAN), and others ndez et al., 2013; Corre ^a et al., 2016). (Valle-Herna PAHs are a pollutant from vehicles, home cooking, pyrolysis of fossil fuel, industrial processes and biomass burning (Hess et al., 2007; Chien et al., 2009; Phoungthong et al., 2009; Sadiktsis et al., 2014; Gogoi et al., 2015; Jedynska et al., 2015). Due to their toxicity, carcinogenicity and mutagenicity, diesel emissions were classified by IARC (2013) as “a human carcinogen”, group 1 (Sadiktsis et al., 2014; Tsai et al., 2014). Particulate matter (PM), including that of PAHs, affects human health when the particles are fine (Phoungthong et al., 2013). These fine particles can evade the mucociliary defence system and deposit themselves deep in the respiratory tract, where they may induce toxic effects (Sadiktsis et al., 2014). In addition, they can float over a long range (Chien et al., 2009; Health Effects Institute, 2002). Therefore, particles from diesel emissions may distribute PAHs to the atmosphere and become an important source of urban air contamination in sur^a et al., 2016). rounding areas (Corre Many studies describe a quantifiable association that exists between the characteristics of petroleum diesel and biodiesel and the ^a and Arbilla, 2006; Kooter composition of their emissions (Corre et al., 2011; Phoungthong et al., 2013; Verbeek et al., 2008; Vojtisek-Lom et al., 2012). It might be commonly accepted that the main sources of PAHs in diesel emissions are the incomplete combustion of PAHs in the fuel, the pyrosynthesis during combustion, and the modification of one PAH into another form (Borr as et al., 2009; Tsai et al., 2014). It was reported that about 80% of benzo[a] pyrene (BaP) in the exhaust emissions come from the same molecules originally present in the fuel (Tancell et al., 1995). Recently, some researchers have shown that the exhaust of PAHs from diesel engines depends on the content of aromatic rings in the diesel fuel (Lin et al., 2006a, 2006b; Mwangi et al., 2015a). The benefits of using alternative fuels to reduce air pollution from diesel emissions have s et al., 2009; been widely investigated around the world (Borra Karavalakis et al., 2009; Sadiktsis et al., 2014). Compared with commercial diesel, oxygenated alternative fuels have several advantages: they are virtually free from aromatic compounds and sulphur content, are produced from natural and renewable rendez sources and are non-toxic and biodegradable (Valle-Herna et al., 2013; Zhang and Balasubramanian, 2016). Both palm oil and biodiesel have a higher amount of oxygen than commercial petroleum diesel. This oxygen can reduce emitted air pollutants, such as, total hydrocarbon compounds (THCs), CO, SOx and PAHs (Chien et al., 2009; Durbin and Norbeck, 2002; Hess et al., 2007; Kalam and Masjuki, 2004; Lin et al., 2006c; Phoungthong et al., 2013). Although alternative fuels for diesel engines have been frequently investigated, most of the studies have focused on emissions from biodiesel (transesterification with methanol or ethanol) combustion. Crude palm oil, however, has not been studied to the same extent, particularly with regard to its emissions of PM, PAHs, carcinogens and the effects of engine operating times on emissions. Our previous study (Phoungthong et al., 2013) has proven that degummed-deacidified crude palm oil blended up to 40% with diesel can be used with an agricultural diesel engine. The aim of this research was to examine and compare the emissions from three different fuels powering an IDI-turbo diesel engine. The
fuels tested were a commercial petroleum diesel and two blended fuels of commercial petroleum diesel and degummed-deacidified palm oil at 40% and 50% by volume. The effects of the blending fraction on exhausts of PM, total PAHs and carcinogenic potencies were investigated by tests which ran the engine in long-term operation. It is vital to assess the environmental impacts and risks of alternative fuel before their utilisation, especially air pollutants. Effective environmental monitoring and protection must be carried out to ensure that the palm oil blend used in this study does not itself constitute an environmental hazard. Overall, this knowledge will give information crucial for the commercial use of palm oil blends instead of diesel and for the promotion of alternative fuel at policy level.
2. Materials and methods 2.1. Reagents, chemicals and fuels The EPA standard solution of PAHs was purchased from Supelco (U.S.A.). All reagents for the extraction of PAHs were purchased from Lab-scan (Thailand), and were of high performance liquid chromatography (HPLC) grade. Ultrapure water used throughout in this work was de-ionised using a reverse osmosis system with an ultra pure water instrument (Maxima, ELGA, England). This study used commercial petro-diesel (PB0) and two different palm oilediesel blends, PB40 and PB50, with 40% and 50% by volume of mixed crude palm oil, respectively. Before blending with diesel, crude palm oil was reacted with an H3PO4 solution at 80 C for 30 min, and deacidified using NaOH for 2 h. This phase was purified by water and gravity settling, and then heated to remove water. The properties of PB0 and mixed crude palm oil, were determined according to the ASTM standard (Leevijit and Prateepchaikul, 2011) and are shown in Table 1. The preparation methods of the fuels tested in this study are presented in previous works (Leevijit and Prateepchaikul, 2011; Phoungthong et al., 2013). PB0 and the mixed crude palm oil had cetane numbers of 48.5% and 42%, respectively but, in Thailand, regulation requires a cetane number for high-speed diesel of 47% (Leevijit and Prateepchaikul, 2011), as shown in Table 1. Although the cetane number of the mixed crude palm oil was lower than the regulatory limit and not actually measured, the PB40 and PB50 blends used in this study, can reliably be expected to fall within the applicable range for these engines. In comparison, the viscosity of the mixed crude palm oil was up to 90 times higher than the viscosity of PB0 and did not meet the regulatory requirement (Leevijit and Prateepchaikul, 2011). Furthermore, the flash point of the mixed crude palm oil was higher than that of PB0, indicating a tendency for the blends to be less of a flammable hazard, and it is possible Table 1 Properties of PB0 and mixed crude palm oil were used, according to the ASTM standards. Fuel properties
PB0
Mixed crude palm oil
Test method
Cetane number Viscosity at 40 C (c St) Flash point ( C) Specific gravity (at 15.6 C) Specific gravity (at 40 C) Lower heating value (MJ kg1) Acid value (mg KOH g1) Water (%) Copper Strip Corrosion Carbon residue (%) Distillation temp ( C)
45e52 3.10 69 0.840 0.828 41.6 NA 0.078 1b <0.001 NA
~42 46.70 >240 0.930 0.916 39.3 5.2 0.218 1b 0.217 319
ASTM ASTM ASTM ASTM e ASTM ASTM ASTM ASTM ASTM ASTM
D613 D445 D93 D4052 D240 D664 D721 D130 D4530 D86
NA: Not available, 1b: satisfaction.
Please cite this article in press as: Phoungthong, K., et al., Comparison of particulate matter and polycyclic aromatic hydrocarbons in emissions from IDI-turbo diesel engine fueled by palm oilediesel blends during long-term usage, Atmospheric Pollution Research (2016), http:// dx.doi.org/10.1016/j.apr.2016.10.006
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that PB40 and PB50 may limit the volatility characteristics of the commercial diesel fuel fraction (Leevijit and Prateepchaikul, 2011). 2.2. Engine, dynamometer and driving cycle The experiments were carried out with overhauled and repaired conventional indirect injection turbo (IDI-turbo) diesel engines (Toyota, 2LT). Table 2 shows the engine specifications. A long-term test was done to consider the effect of palm oil blends on engine durability in comparison to diesel oil. During testing, the engine was run at a constant 2400 rpm under loads of 5.0e37.5 kW controlled by an ESSOM dynamometer model MT504 with a computer interface. The engine was operated on the dynamometer for 20 min after 10 min' warm-up to eliminate false readings due to the residue from fuel used in the previous run. The engine was tested in ambient temperature and relative humidity. Also, it was evaluated fully-loaded in the range of 2000e2800 rpm. All information was collected using the data acquisition system of the dynamometer following a previous procedure (Leevijit and Prateepchaikul, 2011). After the experiment, the engine was dismantled to be visually checked for weight loss and wear of the engine parts. In this study, during the engine operation, the lubricating oils were changed every 100 h prior to each sampling of 1000 h, to avoid effects of the lubricating oils from the previous run. The emissions from the IDIturbo diesel engine were diluted in a dilutor (VKL 10, Palas, Germany), which lowers the concentration of a given aerosol while leaving the particle size distribution unchanged. This is necessary because the original concentration of the exhaust aerosol from engine combustion is very high. Also, the exhaust gas contains a high degree of moisture which can materially affect the sampled aerosol characteristics. A dilution ratio of 10 was used to homogeneously mix a definite amount of clean air with a definite amount of aerosol. The external clean air flowed in through an ejector-nozzle system. This causes an under-pressure which sucks in the aerosol. Consequently, the dilution stage is a self-aspirated system. The samples were collected isokinetically. The dilution air exited an air compressor, and was then passed through a regulator, a laboratory gas drying unit (Drierite, USA) and a high efficiency particulate absorbing (HEPA) filter for moisture, oil and particle removal from the air stream (Phoungthong et al., 2013). 2.3. Measurement of size distribution of PM In this study, particles emitted from the engine were collected and size-fractionated by the four-stage cascade impactor air sampler (Kanomax, Japan). Engine emissions were collected on quartz fibre filters (Type 2500QAT-UP, Pallflex, USA). Donut-shaped filters (65 30 mm diameter) were used through the impaction stages and a 47 mm diameter filter in the backup stage of the cascade air sampler (Phoungthong et al., 2013). Additionally, an 8 mm stainless steel fibre mat was used at the inertial filter stage above the backup filter (Phoungthong et al., 2013). A representation
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of the layout of the IDI-turbo diesel engine and instrumentation with PM cascade air sampler is shown in Fig. 1. A constant air flow rate of 40 L min1 was drawn by a vacuum pump, and controlled by a needle valve and a rotameter. All filter samples from the quartz fibre filters and stainless steel fibre mat were pre-treated at a constant temperature of 25 C and constant relative humidity of 50% for 72 h. Then the mass of PMs collected was weighed on an analytical balance readable to five digits (0.01 mg precision, CP225D, Sartorius, Germany). After sampling, the filters were treated under the same conditions as before sampling and weighed using the identical analytical balance. After being weighed, all filter samples were stored under refrigeration at 20 C (up to 1 week) for the subsequent analysis. 2.4. Analysis of PAHs The mass fractions were monitored for the following particlebound PAH compounds: 2 rings, naphthalene (Nap); 3 rings, acenaphthylene (Act), acenaphthene (Ace), phenanthrene (Phe), anthracene (Ant) and fluorene (Fle); 4 rings, fluoranthene (Flu), pyrene (Pyr), benzo[a]anthracene (BaA) and chrysene (Chr); 5 rings, benzo[a]pyrene (BaP), benzo[b]fluoranthene (BbF), benzo[k] fluoranthene (BkF) and dibenz[a,h]anthracene (DBA); and 6 rings, indeno[1,2,3-cd]pyrene (IDP) and benzo[g,h,i]perylene (BghiPe). Filter samples were extracted with dichloromethane by ultrasonic technique and water in the ultrasonic bath was controlled between 4 and 10 C. Insoluble particles were removed from the extracts, which were then added to dimethylsulfoxide for PAH preservation, and the extracted solution was concentrated using an evaporator. The extracts were analysed using HPLC (1100, Agilent, USA) with a diode array detector (DAD), following a previous method (Phoungthong et al., 2013) with appropriate modifications. The HPLC system consisted of a VertiSep UPS C 18 reversed phase column (4.6 250 mm, 5 mm) with a guard column and an injection volume of 25 mL. The solvent gradient elution of acetonitrile and ultrapure water was used for 40 min at the flow rate of 1.0e1.2 mL min1. A good linear correlation between the concentrations and peak areas was found with R2 for all PAH compounds. Field blank filters as well as solvent blanks were analysed by the same procedure and integrated areas that were confirmed to be small enough were subtracted from analysed values. The HPLC conditions, standard preparation, limit of detection and individual PAH recovery percentages used in this work are summarised in Tables S1eS5 and Figs. S1eS2 in the supplementary material. 3. Results and discussion 3.1. General engine operation Although some fuel properties of palm oil blends do not exactly meet the requirements of Thailand's high-speed diesel regulations (Leevijit and Prateepchaikul, 2011), especially the viscosity, which
Table 2 Engine specifications. Parameters
Specifications
Brand Model Engine type Injection Displacement Bore stroke Volumetric compression ratio Maximum power Maximum torque Fuel system
Toyota 2L-T Water cooling serial 4 cylinder SOHC turbo diesel engine Indirect injection (IDI) 2446 c.c. 92 92 mm 21.0:1 69.14 kW at 4000 rpm (94 HP @ 4000 rpm) 22.0 kg m at 2400 rpm (215.75 N m @ 2400 rpm) Bosch type distribution type (jet pump)
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Fig. 1. Schematics of experimental set up.
is higher than that of PB0, all of the palm oil blends can be used in the same way as diesel for running a diesel engine. During this work, no critical problems were found in fuel pumping or injection, nor in cold starting, harmful knocking or piston ring sticking. The emission test cycle for the IDI-turbo diesel engines using PB0 and PB40 was 1000 h. Using palm oil blends in diesel at 50% was found to be unsatisfactory for the engine long-term. Therefore, the test cycle for PB50 was only 400 h long. 3.2. Effect of long-term engine usage on PMs Fig. 2 (a) shows the particle size distributions of PM collected from the engines using PB0, PB40 and PB50 fuels at initial conditions and final conditions. The results indicate an accumulation mode with predominantly small particle sizes (<1 mm), similar to the findings of earlier studies (Chien et al., 2009; Lim et al., 2015). Concentrations of PM emissions at initial conditions were 24.6, 19.5, and 16.6 mg m3 for PB0, PB40, and PB50, respectively. PM emissions decrease as the blending percentages of palm oil increase, since the palm oil blends contain more oxygen than unblended diesel. The increased oxygen content of higher palm oil blend ratios provides a more complete combustion, which is seen in earlier studies (Chien et al., 2009; Haas et al., 2001; Phoungthong et al., 2013). PM emissions at final conditions were at concentrations of 30.2, 27.8, and 20.0 mg m3 for PB0, PB40, and PB50, respectively. Concentrations of PM increased as the operating time of the engine increased. After test cycles of up to 1000 h for PB0 and PB40, and 400 h for PB50, this could be a result of engine wear, which can cause a greater degree of incomplete combustion and generate a larger portion of PM, compared with a new engine at initial state (0 h). We evaluated engine wear by weighing the parts of the engine at the beginning (0 h) of the test cycles, and again after 1000 h (PB0 and PB40) and 400 h (PB50) of running. We found that the compression rings showed the most significant weight loss and that this increased with engine operating times. 3.3. Effect of long-term engine usage on PAHs Variations of concentration and size distribution of PAHs over the various size classes of the particles are shown in Fig. 2 (b). Size
Fig. 2. Size distribution of (a) PM and (b) particle-bound PAHs, from IDI-turbo engine using PB0, PB40 and PB50 with initially and finally conditions.
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distributions of total PAHs show a similar trend to the size distribution of PM, indicating that the particulates are primarily inhalable particulates. There is no significant difference in the PAH size distribution between PB0, PB40, and PB50. PAH emissions at 0 h were 43.7, 33.5, and 27.7 mg m3 for PB0, PB40, and PB50, respectively. The result of particulate associated PAH emissions of PB0 agree with many previous investigations (Lin et al., 2006a; Sadiktsis et al., 2014; Jedynska et al., 2015), for total PAH concentrations and individual PAH compounds. The reduction rate of total PAH concentrations is similar to that of the PM concentrations. In addition, total PAH concentrations increased when increasing the engine operating times for all blend ratios and almost all particle sizes. PAH emissions at 1000 h were 58.9 and 51.1 mg m3 for PB0 and PB40, respectively. For PB50, PAH emission at 400 h was 35.0 mg m3. The reduction of PAH emission from the palm oil blends can be attributed to the fact that palm oil, unlike diesel, contains no aromatic constituent (Vallendez et al., 2013; Zhang and Balasubramanian, 2016). Herna 3.4. Profile of PAHs The mass fractions of individual PAH compounds under initial and final conditions are presented in Fig. 3. The difference between diesel and palm oil blends were the patterns of PAH compounds associated with 2e3 and 4e6 aromatic rings. Due to the different characteristics of diesel oil and palm oil, there were more 2e3 ring PAHs from the mass fraction of the palm oil blends than from that of PB0. These results indicated that the PAHs in the palm oil blend diesel fuel (PB40 and PB50) were primarily dominated by low molecular weight PAH compounds (Lin et al., 2006a; Phoungthong et al., 2013). At initial conditions of the test cycle for PB40 and PB50, fractions of 2e3 ring PAHs (Nap, Act, Ace, Fle, Phe and Ant) contributed 50.2% and 51.4%, respectively, of the total PAHs for all particle size ranges. For PB0, 2e3 ring PAHs contributed less, at 40.6%. Under final conditions, the mass fraction of PAH showed different patterns. The results demonstrate that the concentration of 4e6 ring PAHs increased when the running time of the engine was increased. For PB0, mostly 4e6 ring PAHs were generated compared with PB40 and PB50. Higher engine times resulted in a higher amount of generated 4e6 ring PAHs for every blend ratio due to erosion of the engine.
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comparing the effects of the different palm oil ratios with PB0. The reduction percentages of PM, total PAHs and total BaPeq emissions at the engine times of initial and final conditions, are shown in Fig. 4. When using PB40 and PB50, PM at initial conditions was reduced by 20.7% and 32.5%, respectively, and the PM contained less PAHs than emissions of PB0 by 23.4%e36.7%. At final conditions, PM was reduced by 8.2%e33.9% and PAHs were reduced by 13.3%e40.6% when using PB40 and PB50, respectively. These results show that the PM and total PAH emissions from engines using palm oil blends for all size ranges of particles, were reduced compared to PB0 exhaust. The reduction percentages of PM and PAH emissions increased with the higher blending percentages of palm oil. To assess the carcinogenic potencies of emissions from long-term usage of the engine fueled by PB0, PB40, and PB50, BaPeq was applied as an indicator for the 16 analysed PAHs. The carcinogenic potency of individual PAHs can be assessed by comparison with the carcinogenicity of BaP (Nisbet and LaGoy, 1992). The amount of BaP toxic equivalent of particles measured from the engines is shown in Table 3. The largest BaPeq was observed from PB0 at 1000 h with 9.32 mg m3 against 5.15 and 3.04 mg m3 for PB40 and PB50 at 1000 h and 400 h, respectively. As the blending ratio was increased, the BaPeq emission decreased gradually. The total emission of BaPeq was also found to increase with engine times, indicating that the higher molecular weight PAHs are more carcinogenic than the lower molecular weight PAHs. As shown in Fig. 4, the PM reduction data for palm oil blends in this study are similar to the PM reduction data for palm biodiesel blended (10%e 30%) with commercial diesel in a Taiwanese study (Chen et al., 2010). In another study (Lin et al., 2008; Mwangi et al., 2015b), the PM emission was reduced by about 22%e57% using microalgae biodiesel and soy biodiesel (10%e30%) with advanced 4-cylinders injection diesel engines. There are no apparent differences between the results of previous studies (Lin et al., 2008; Chen et al., 2010; Mwangi et al., 2015b) and those of this study, when considering reductions in PAHs and BaPeq emissions.
3.5. Effect of palm oil blends on PM, PAH and BaPeq emissions We investigated the reduction of PM, total PAHs and total benzo [a]pyrene equivalent (BaPeq) emissions of PB40 and PB50 by
Fig. 3. Mass fraction of each PAH from IDI-turbo engine using PB0, PB40 and PB50 in particulate phase.
Fig. 4. Reduction percentages of PM, total PAH and total BaPeq emissions by PB40 and PB50 compared with PB0 with initially and finally conditions.
Please cite this article in press as: Phoungthong, K., et al., Comparison of particulate matter and polycyclic aromatic hydrocarbons in emissions from IDI-turbo diesel engine fueled by palm oilediesel blends during long-term usage, Atmospheric Pollution Research (2016), http:// dx.doi.org/10.1016/j.apr.2016.10.006
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Table 3 Concentration of each BaPeq measured from IDI-turbo diesel engine different conditions. Engine hour (hr)
0 400 1000
S BaPeq (mg m3) PB0
PB40
PB50
4.09 NA 9.32
2.64 NA 5.15
1.98 3.04 NA
NA: Not available.
4. Conclusions The characteristics of PM, PAHs, and BaPeq emission from IDIturbo diesel engines using PB40 and PB50, operating from 0 to 1000 h, were investigated and compared with PB0. The size distribution of PM fueled with PB0, PB40, and PB50 showed an accumulation mode. Increasing the blending ratio caused a reduction of PM, while increasing the operating time caused an increase of PM. Size distributions and concentrations of PAHs showed similar trends to PM. Using palm oil blends instead of commercial diesel reduced the emissions of PM (8.2%e33.9%), total PAHs (13.3%e 40.6%), and total BaPeq (35.4%e67.4%) significantly. It is because the PAH content of palm oil is smaller than that of commercial diesel. So, the high fraction of palm oil in the PB40 and PB50 blends results in a lower PAH emission. Also, the carcinogenic potency equivalency factors were reduced when palm oil blends were used. Palm oil has a high amount of oxygen that can enable more complete combustion than commercial diesel. However, adding too much palm oil to blends with commercial diesel would cause incomplete combustion and inhibit the release of energy from the fuel in IDIturbo diesel engines. In particular, PB50 has been shown to be unsatisfactory for long-term test usage in IDI-turbo diesel engines. As a result of engine wear to piston rods, piston rings, compression rings, and other parts, it cannot be used anymore. The test cycle for PB50 was shorter than for PB0 and PB40 at final conditions of 400 h. Therefore, it is necessary to further evaluate the environmental impacts and risks of palm oil blends before their utilisation. Physical and chemical modifications of palm oil blends for commercial diesel engines are also needed in the future, with higher fractions of palm oil blending, and mechanical adaptations to modern diesel engines or a new version.
Conflict of interest The authors have declared no conflict of interest.
Acknowledgments The financial support from Prince of Songkla University (annual research grant for fiscal years 2008e2010, No. ENG5200595) is gratefully acknowledged. The authors heartily thank Associate Professor Gumpon Prateepchaikul and the technical staff for their excellent work and assistance with relevant experimental analysis and sample collection, and Mr. Thomas Duncan Coyne for improving English of this manuscript.
Appendix A. Supplementary data Supplementary data related to this article can be found at http:// dx.doi.org/10.1016/j.apr.2016.10.006.
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Impact of using fishing boat fuel with high poly aromatic content on the emission of polycyclic aromatic hydrocarbons from the diesel engine. Atmos. Environ. 40, 1601e1609. Lin, Y.C., Lee, W.J., Wu, T.S., Wang, C.T., 2006c. Comparison of PAH and regulated harmful matter emissions from biodiesel blends and paraffinic fuel blends on engine accumulated mileage test. Fuel 85, 2516e2523. Mwangi, J.K., Lee, W.J., Chang, Y.C., Chen, C.Y., Wang, L.C., 2015a. An overview: energy saving and pollution reduction by using green fuel blends in diesel engines. Appl. Energy 159, 214e236. Mwangi, J.K., Lee, W.J., Whang, L.M., Wu, T.S., Chen, W.H., Chang, J.S., Chen, C.Y., Chen, C.L., 2015b. Microalgae oil: algae cultivation and harvest, algae residue torrefaction and diesel engine emissions tests. Aerosol Air Qual. Res. 15, 81e98. Nisbet, C., LaGoy, P., 1992. Toxic equivalency factors (TEFs) for polycyclic aromatic hydrocarbons (PAHs). Regul. Toxicol. Pharmacol. 16, 290e300. 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Original Article
Comparison of particulate matter and polycyclic aromatic hydrocarbons in emissions from IDI-turbo diesel engine fueled by palm oilediesel blends during long-term usage Khamphe Phoungthong a, *, Surajit Tekasakul a, **, Perapong Tekasakul b, Masami Furuuchi c a
Department of Chemistry, Faculty of Science, Prince of Songkla University, Songkhla 90112, Thailand Energy Technology Research Center (ETRC) and Department of Mechanical Engineering, Faculty of Engineering, Prince of Songkla University, Songkhla 90112, Thailand c Graduate School of Natural Science and Technology, Kanazawa University, Kanazawa 920-1192, Japan b
a r t i c l e i n f o
a b s t r a c t
Article history: Received 24 June 2016 Accepted 10 October 2016 Available online xxx
We examined particulate matter (PM), polycyclic aromatic hydrocarbons (PAHs), and carcinogenic potencies of benzo[a]pyrene equivalent (BaPeq) emissions from an indirect injection (IDI-turbo) diesel engine fueled by commercial diesel (PB0) and palm oil blends with portions of 40 and 50 vol.% (PB40 and PB50). The engine was in operation over long-term test cycles. A four-stage cascade impactor air sampler was used to collect particles emitted from the engine. The PM and PAHs were predominantly fine particles (<1 mm) and show an accumulation mode. The total emissions of the IDI-turbo diesel engine increased when the operation times were increased. The mass fractions of 2e3 rings PAHs using PB0, PB40, and PB50 contributed 35.5%e40.6%, 44.7%e50.2%, and 45.9%e51.4%, respectively; for PB0 2e3 ring PAHs contributed less than palm oil blends. Using PB40 and PB50 caused a higher emission of lower molecular weight PAHs than PB0. However, the mass fractions showed that the concentration of 4e6 ring PAHs increased when the running time of the engine was increased for all three fuels. The results in this study showed that significant emissions of PM, PAHs, and BaPeq were reduced as the fraction ratio of palm oil was increased because palm oil blends have a high amount of oxygen, which enhances combustion compared to PB0. Although PM, PAHs, and BaPeq emissions of PB50 were less than those of PB0 and PB40, PB50 is not an appropriate fuel for the long-term running of this engine. Copyright © 2016 Turkish National Committee for Air Pollution Research and Control. Production and hosting by Elsevier B.V. All rights reserved.
Keywords: Diesel engine Diesel emissions Mixed crude palm oil Particulate matter Polycyclic aromatic hydrocarbons
1. Introduction Rapid urbanisation has brought with it two major problems: environmental pollution related to petroleum fuel consumption and the management of petroleum as a major source of energy. The price of oil on the world market is unstable, making imported petroleum a critical element in the supply of energy. Consequently, alternative sources of energy to petroleum have become of increasing interest. With the rapid growth of agricultural resources
* Corresponding author. Fax: þ66 74 558 841. ** Corresponding author. Fax: þ66 74 558 841. E-mail addresses: [email protected] (K. Phoungthong), [email protected] (S. Tekasakul). Peer review under responsibility of Turkish National Committee for Air Pollution Research and Control.
for biodiesel production, the search for a diesel substitute has gained momentum. In general, the physicochemical properties of palm oil meet the requirements of diesel engine combustion (Leevijit and Prateepchaikul, 2011; Phoungthong et al., 2013). Recently, several publications (Kalam and Masjuki, 2004; Lin et al., 2006a; Leevijit and Prateepchaikul, 2011; Phoungthong et al., 2013) have considered the use of palm oil blends for use in diesel engines as an appropriate solution for reducing both imports of petroleum and environmental problems. Diesel engines are in widespread use in Thailand and many other countries, and their numbers are predicted to increase in the future due to their availability and durability (Mwangi et al., 2015a). But, automotive diesel engine emissions are regarded as a major source of anthropogenic air pollution, even though compression ignited engines produce fewer total engine exhaust emissions than ^a et al., 2016). spark ignited engines (Gogoi et al., 2015; Corre
http://dx.doi.org/10.1016/j.apr.2016.10.006 1309-1042/Copyright © 2016 Turkish National Committee for Air Pollution Research and Control. Production and hosting by Elsevier B.V. All rights reserved.
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Crucially, diesel emissions vary according to fuel and vehicle type, engine technology, and tuning, maintenance and driving behav^a and Arbilla, 2006; Corre ^a et al., 2016; Mwangi et al., iours (Corre 2015a; Topinka et al., 2012). Diesel engines emit a large amount of fine-particles containing a lot of chemical compounds. Some of them are carcinogenic and mutagenic components, for example, aldehydes, ketones, benzene, and polycyclic aromatic hydrocarbons (PAHs) (Tsai et al., 2014; Jedynska et al., 2015; Mwangi et al., 2015a). These pollutants can react with sunlight to produce secondary pollutants, especially peroxy-acetyl nitrate (PAN), and others ndez et al., 2013; Corre ^a et al., 2016). (Valle-Herna PAHs are a pollutant from vehicles, home cooking, pyrolysis of fossil fuel, industrial processes and biomass burning (Hess et al., 2007; Chien et al., 2009; Phoungthong et al., 2009; Sadiktsis et al., 2014; Gogoi et al., 2015; Jedynska et al., 2015). Due to their toxicity, carcinogenicity and mutagenicity, diesel emissions were classified by IARC (2013) as “a human carcinogen”, group 1 (Sadiktsis et al., 2014; Tsai et al., 2014). Particulate matter (PM), including that of PAHs, affects human health when the particles are fine (Phoungthong et al., 2013). These fine particles can evade the mucociliary defence system and deposit themselves deep in the respiratory tract, where they may induce toxic effects (Sadiktsis et al., 2014). In addition, they can float over a long range (Chien et al., 2009; Health Effects Institute, 2002). Therefore, particles from diesel emissions may distribute PAHs to the atmosphere and become an important source of urban air contamination in sur^a et al., 2016). rounding areas (Corre Many studies describe a quantifiable association that exists between the characteristics of petroleum diesel and biodiesel and the ^a and Arbilla, 2006; Kooter composition of their emissions (Corre et al., 2011; Phoungthong et al., 2013; Verbeek et al., 2008; Vojtisek-Lom et al., 2012). It might be commonly accepted that the main sources of PAHs in diesel emissions are the incomplete combustion of PAHs in the fuel, the pyrosynthesis during combustion, and the modification of one PAH into another form (Borr as et al., 2009; Tsai et al., 2014). It was reported that about 80% of benzo[a] pyrene (BaP) in the exhaust emissions come from the same molecules originally present in the fuel (Tancell et al., 1995). Recently, some researchers have shown that the exhaust of PAHs from diesel engines depends on the content of aromatic rings in the diesel fuel (Lin et al., 2006a, 2006b; Mwangi et al., 2015a). The benefits of using alternative fuels to reduce air pollution from diesel emissions have s et al., 2009; been widely investigated around the world (Borra Karavalakis et al., 2009; Sadiktsis et al., 2014). Compared with commercial diesel, oxygenated alternative fuels have several advantages: they are virtually free from aromatic compounds and sulphur content, are produced from natural and renewable rendez sources and are non-toxic and biodegradable (Valle-Herna et al., 2013; Zhang and Balasubramanian, 2016). Both palm oil and biodiesel have a higher amount of oxygen than commercial petroleum diesel. This oxygen can reduce emitted air pollutants, such as, total hydrocarbon compounds (THCs), CO, SOx and PAHs (Chien et al., 2009; Durbin and Norbeck, 2002; Hess et al., 2007; Kalam and Masjuki, 2004; Lin et al., 2006c; Phoungthong et al., 2013). Although alternative fuels for diesel engines have been frequently investigated, most of the studies have focused on emissions from biodiesel (transesterification with methanol or ethanol) combustion. Crude palm oil, however, has not been studied to the same extent, particularly with regard to its emissions of PM, PAHs, carcinogens and the effects of engine operating times on emissions. Our previous study (Phoungthong et al., 2013) has proven that degummed-deacidified crude palm oil blended up to 40% with diesel can be used with an agricultural diesel engine. The aim of this research was to examine and compare the emissions from three different fuels powering an IDI-turbo diesel engine. The
fuels tested were a commercial petroleum diesel and two blended fuels of commercial petroleum diesel and degummed-deacidified palm oil at 40% and 50% by volume. The effects of the blending fraction on exhausts of PM, total PAHs and carcinogenic potencies were investigated by tests which ran the engine in long-term operation. It is vital to assess the environmental impacts and risks of alternative fuel before their utilisation, especially air pollutants. Effective environmental monitoring and protection must be carried out to ensure that the palm oil blend used in this study does not itself constitute an environmental hazard. Overall, this knowledge will give information crucial for the commercial use of palm oil blends instead of diesel and for the promotion of alternative fuel at policy level.
2. Materials and methods 2.1. Reagents, chemicals and fuels The EPA standard solution of PAHs was purchased from Supelco (U.S.A.). All reagents for the extraction of PAHs were purchased from Lab-scan (Thailand), and were of high performance liquid chromatography (HPLC) grade. Ultrapure water used throughout in this work was de-ionised using a reverse osmosis system with an ultra pure water instrument (Maxima, ELGA, England). This study used commercial petro-diesel (PB0) and two different palm oilediesel blends, PB40 and PB50, with 40% and 50% by volume of mixed crude palm oil, respectively. Before blending with diesel, crude palm oil was reacted with an H3PO4 solution at 80 C for 30 min, and deacidified using NaOH for 2 h. This phase was purified by water and gravity settling, and then heated to remove water. The properties of PB0 and mixed crude palm oil, were determined according to the ASTM standard (Leevijit and Prateepchaikul, 2011) and are shown in Table 1. The preparation methods of the fuels tested in this study are presented in previous works (Leevijit and Prateepchaikul, 2011; Phoungthong et al., 2013). PB0 and the mixed crude palm oil had cetane numbers of 48.5% and 42%, respectively but, in Thailand, regulation requires a cetane number for high-speed diesel of 47% (Leevijit and Prateepchaikul, 2011), as shown in Table 1. Although the cetane number of the mixed crude palm oil was lower than the regulatory limit and not actually measured, the PB40 and PB50 blends used in this study, can reliably be expected to fall within the applicable range for these engines. In comparison, the viscosity of the mixed crude palm oil was up to 90 times higher than the viscosity of PB0 and did not meet the regulatory requirement (Leevijit and Prateepchaikul, 2011). Furthermore, the flash point of the mixed crude palm oil was higher than that of PB0, indicating a tendency for the blends to be less of a flammable hazard, and it is possible Table 1 Properties of PB0 and mixed crude palm oil were used, according to the ASTM standards. Fuel properties
PB0
Mixed crude palm oil
Test method
Cetane number Viscosity at 40 C (c St) Flash point ( C) Specific gravity (at 15.6 C) Specific gravity (at 40 C) Lower heating value (MJ kg1) Acid value (mg KOH g1) Water (%) Copper Strip Corrosion Carbon residue (%) Distillation temp ( C)
45e52 3.10 69 0.840 0.828 41.6 NA 0.078 1b <0.001 NA
~42 46.70 >240 0.930 0.916 39.3 5.2 0.218 1b 0.217 319
ASTM ASTM ASTM ASTM e ASTM ASTM ASTM ASTM ASTM ASTM
D613 D445 D93 D4052 D240 D664 D721 D130 D4530 D86
NA: Not available, 1b: satisfaction.
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that PB40 and PB50 may limit the volatility characteristics of the commercial diesel fuel fraction (Leevijit and Prateepchaikul, 2011). 2.2. Engine, dynamometer and driving cycle The experiments were carried out with overhauled and repaired conventional indirect injection turbo (IDI-turbo) diesel engines (Toyota, 2LT). Table 2 shows the engine specifications. A long-term test was done to consider the effect of palm oil blends on engine durability in comparison to diesel oil. During testing, the engine was run at a constant 2400 rpm under loads of 5.0e37.5 kW controlled by an ESSOM dynamometer model MT504 with a computer interface. The engine was operated on the dynamometer for 20 min after 10 min' warm-up to eliminate false readings due to the residue from fuel used in the previous run. The engine was tested in ambient temperature and relative humidity. Also, it was evaluated fully-loaded in the range of 2000e2800 rpm. All information was collected using the data acquisition system of the dynamometer following a previous procedure (Leevijit and Prateepchaikul, 2011). After the experiment, the engine was dismantled to be visually checked for weight loss and wear of the engine parts. In this study, during the engine operation, the lubricating oils were changed every 100 h prior to each sampling of 1000 h, to avoid effects of the lubricating oils from the previous run. The emissions from the IDIturbo diesel engine were diluted in a dilutor (VKL 10, Palas, Germany), which lowers the concentration of a given aerosol while leaving the particle size distribution unchanged. This is necessary because the original concentration of the exhaust aerosol from engine combustion is very high. Also, the exhaust gas contains a high degree of moisture which can materially affect the sampled aerosol characteristics. A dilution ratio of 10 was used to homogeneously mix a definite amount of clean air with a definite amount of aerosol. The external clean air flowed in through an ejector-nozzle system. This causes an under-pressure which sucks in the aerosol. Consequently, the dilution stage is a self-aspirated system. The samples were collected isokinetically. The dilution air exited an air compressor, and was then passed through a regulator, a laboratory gas drying unit (Drierite, USA) and a high efficiency particulate absorbing (HEPA) filter for moisture, oil and particle removal from the air stream (Phoungthong et al., 2013). 2.3. Measurement of size distribution of PM In this study, particles emitted from the engine were collected and size-fractionated by the four-stage cascade impactor air sampler (Kanomax, Japan). Engine emissions were collected on quartz fibre filters (Type 2500QAT-UP, Pallflex, USA). Donut-shaped filters (65 30 mm diameter) were used through the impaction stages and a 47 mm diameter filter in the backup stage of the cascade air sampler (Phoungthong et al., 2013). Additionally, an 8 mm stainless steel fibre mat was used at the inertial filter stage above the backup filter (Phoungthong et al., 2013). A representation
3
of the layout of the IDI-turbo diesel engine and instrumentation with PM cascade air sampler is shown in Fig. 1. A constant air flow rate of 40 L min1 was drawn by a vacuum pump, and controlled by a needle valve and a rotameter. All filter samples from the quartz fibre filters and stainless steel fibre mat were pre-treated at a constant temperature of 25 C and constant relative humidity of 50% for 72 h. Then the mass of PMs collected was weighed on an analytical balance readable to five digits (0.01 mg precision, CP225D, Sartorius, Germany). After sampling, the filters were treated under the same conditions as before sampling and weighed using the identical analytical balance. After being weighed, all filter samples were stored under refrigeration at 20 C (up to 1 week) for the subsequent analysis. 2.4. Analysis of PAHs The mass fractions were monitored for the following particlebound PAH compounds: 2 rings, naphthalene (Nap); 3 rings, acenaphthylene (Act), acenaphthene (Ace), phenanthrene (Phe), anthracene (Ant) and fluorene (Fle); 4 rings, fluoranthene (Flu), pyrene (Pyr), benzo[a]anthracene (BaA) and chrysene (Chr); 5 rings, benzo[a]pyrene (BaP), benzo[b]fluoranthene (BbF), benzo[k] fluoranthene (BkF) and dibenz[a,h]anthracene (DBA); and 6 rings, indeno[1,2,3-cd]pyrene (IDP) and benzo[g,h,i]perylene (BghiPe). Filter samples were extracted with dichloromethane by ultrasonic technique and water in the ultrasonic bath was controlled between 4 and 10 C. Insoluble particles were removed from the extracts, which were then added to dimethylsulfoxide for PAH preservation, and the extracted solution was concentrated using an evaporator. The extracts were analysed using HPLC (1100, Agilent, USA) with a diode array detector (DAD), following a previous method (Phoungthong et al., 2013) with appropriate modifications. The HPLC system consisted of a VertiSep UPS C 18 reversed phase column (4.6 250 mm, 5 mm) with a guard column and an injection volume of 25 mL. The solvent gradient elution of acetonitrile and ultrapure water was used for 40 min at the flow rate of 1.0e1.2 mL min1. A good linear correlation between the concentrations and peak areas was found with R2 for all PAH compounds. Field blank filters as well as solvent blanks were analysed by the same procedure and integrated areas that were confirmed to be small enough were subtracted from analysed values. The HPLC conditions, standard preparation, limit of detection and individual PAH recovery percentages used in this work are summarised in Tables S1eS5 and Figs. S1eS2 in the supplementary material. 3. Results and discussion 3.1. General engine operation Although some fuel properties of palm oil blends do not exactly meet the requirements of Thailand's high-speed diesel regulations (Leevijit and Prateepchaikul, 2011), especially the viscosity, which
Table 2 Engine specifications. Parameters
Specifications
Brand Model Engine type Injection Displacement Bore stroke Volumetric compression ratio Maximum power Maximum torque Fuel system
Toyota 2L-T Water cooling serial 4 cylinder SOHC turbo diesel engine Indirect injection (IDI) 2446 c.c. 92 92 mm 21.0:1 69.14 kW at 4000 rpm (94 HP @ 4000 rpm) 22.0 kg m at 2400 rpm (215.75 N m @ 2400 rpm) Bosch type distribution type (jet pump)
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Fig. 1. Schematics of experimental set up.
is higher than that of PB0, all of the palm oil blends can be used in the same way as diesel for running a diesel engine. During this work, no critical problems were found in fuel pumping or injection, nor in cold starting, harmful knocking or piston ring sticking. The emission test cycle for the IDI-turbo diesel engines using PB0 and PB40 was 1000 h. Using palm oil blends in diesel at 50% was found to be unsatisfactory for the engine long-term. Therefore, the test cycle for PB50 was only 400 h long. 3.2. Effect of long-term engine usage on PMs Fig. 2 (a) shows the particle size distributions of PM collected from the engines using PB0, PB40 and PB50 fuels at initial conditions and final conditions. The results indicate an accumulation mode with predominantly small particle sizes (<1 mm), similar to the findings of earlier studies (Chien et al., 2009; Lim et al., 2015). Concentrations of PM emissions at initial conditions were 24.6, 19.5, and 16.6 mg m3 for PB0, PB40, and PB50, respectively. PM emissions decrease as the blending percentages of palm oil increase, since the palm oil blends contain more oxygen than unblended diesel. The increased oxygen content of higher palm oil blend ratios provides a more complete combustion, which is seen in earlier studies (Chien et al., 2009; Haas et al., 2001; Phoungthong et al., 2013). PM emissions at final conditions were at concentrations of 30.2, 27.8, and 20.0 mg m3 for PB0, PB40, and PB50, respectively. Concentrations of PM increased as the operating time of the engine increased. After test cycles of up to 1000 h for PB0 and PB40, and 400 h for PB50, this could be a result of engine wear, which can cause a greater degree of incomplete combustion and generate a larger portion of PM, compared with a new engine at initial state (0 h). We evaluated engine wear by weighing the parts of the engine at the beginning (0 h) of the test cycles, and again after 1000 h (PB0 and PB40) and 400 h (PB50) of running. We found that the compression rings showed the most significant weight loss and that this increased with engine operating times. 3.3. Effect of long-term engine usage on PAHs Variations of concentration and size distribution of PAHs over the various size classes of the particles are shown in Fig. 2 (b). Size
Fig. 2. Size distribution of (a) PM and (b) particle-bound PAHs, from IDI-turbo engine using PB0, PB40 and PB50 with initially and finally conditions.
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distributions of total PAHs show a similar trend to the size distribution of PM, indicating that the particulates are primarily inhalable particulates. There is no significant difference in the PAH size distribution between PB0, PB40, and PB50. PAH emissions at 0 h were 43.7, 33.5, and 27.7 mg m3 for PB0, PB40, and PB50, respectively. The result of particulate associated PAH emissions of PB0 agree with many previous investigations (Lin et al., 2006a; Sadiktsis et al., 2014; Jedynska et al., 2015), for total PAH concentrations and individual PAH compounds. The reduction rate of total PAH concentrations is similar to that of the PM concentrations. In addition, total PAH concentrations increased when increasing the engine operating times for all blend ratios and almost all particle sizes. PAH emissions at 1000 h were 58.9 and 51.1 mg m3 for PB0 and PB40, respectively. For PB50, PAH emission at 400 h was 35.0 mg m3. The reduction of PAH emission from the palm oil blends can be attributed to the fact that palm oil, unlike diesel, contains no aromatic constituent (Vallendez et al., 2013; Zhang and Balasubramanian, 2016). Herna 3.4. Profile of PAHs The mass fractions of individual PAH compounds under initial and final conditions are presented in Fig. 3. The difference between diesel and palm oil blends were the patterns of PAH compounds associated with 2e3 and 4e6 aromatic rings. Due to the different characteristics of diesel oil and palm oil, there were more 2e3 ring PAHs from the mass fraction of the palm oil blends than from that of PB0. These results indicated that the PAHs in the palm oil blend diesel fuel (PB40 and PB50) were primarily dominated by low molecular weight PAH compounds (Lin et al., 2006a; Phoungthong et al., 2013). At initial conditions of the test cycle for PB40 and PB50, fractions of 2e3 ring PAHs (Nap, Act, Ace, Fle, Phe and Ant) contributed 50.2% and 51.4%, respectively, of the total PAHs for all particle size ranges. For PB0, 2e3 ring PAHs contributed less, at 40.6%. Under final conditions, the mass fraction of PAH showed different patterns. The results demonstrate that the concentration of 4e6 ring PAHs increased when the running time of the engine was increased. For PB0, mostly 4e6 ring PAHs were generated compared with PB40 and PB50. Higher engine times resulted in a higher amount of generated 4e6 ring PAHs for every blend ratio due to erosion of the engine.
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comparing the effects of the different palm oil ratios with PB0. The reduction percentages of PM, total PAHs and total BaPeq emissions at the engine times of initial and final conditions, are shown in Fig. 4. When using PB40 and PB50, PM at initial conditions was reduced by 20.7% and 32.5%, respectively, and the PM contained less PAHs than emissions of PB0 by 23.4%e36.7%. At final conditions, PM was reduced by 8.2%e33.9% and PAHs were reduced by 13.3%e40.6% when using PB40 and PB50, respectively. These results show that the PM and total PAH emissions from engines using palm oil blends for all size ranges of particles, were reduced compared to PB0 exhaust. The reduction percentages of PM and PAH emissions increased with the higher blending percentages of palm oil. To assess the carcinogenic potencies of emissions from long-term usage of the engine fueled by PB0, PB40, and PB50, BaPeq was applied as an indicator for the 16 analysed PAHs. The carcinogenic potency of individual PAHs can be assessed by comparison with the carcinogenicity of BaP (Nisbet and LaGoy, 1992). The amount of BaP toxic equivalent of particles measured from the engines is shown in Table 3. The largest BaPeq was observed from PB0 at 1000 h with 9.32 mg m3 against 5.15 and 3.04 mg m3 for PB40 and PB50 at 1000 h and 400 h, respectively. As the blending ratio was increased, the BaPeq emission decreased gradually. The total emission of BaPeq was also found to increase with engine times, indicating that the higher molecular weight PAHs are more carcinogenic than the lower molecular weight PAHs. As shown in Fig. 4, the PM reduction data for palm oil blends in this study are similar to the PM reduction data for palm biodiesel blended (10%e 30%) with commercial diesel in a Taiwanese study (Chen et al., 2010). In another study (Lin et al., 2008; Mwangi et al., 2015b), the PM emission was reduced by about 22%e57% using microalgae biodiesel and soy biodiesel (10%e30%) with advanced 4-cylinders injection diesel engines. There are no apparent differences between the results of previous studies (Lin et al., 2008; Chen et al., 2010; Mwangi et al., 2015b) and those of this study, when considering reductions in PAHs and BaPeq emissions.
3.5. Effect of palm oil blends on PM, PAH and BaPeq emissions We investigated the reduction of PM, total PAHs and total benzo [a]pyrene equivalent (BaPeq) emissions of PB40 and PB50 by
Fig. 3. Mass fraction of each PAH from IDI-turbo engine using PB0, PB40 and PB50 in particulate phase.
Fig. 4. Reduction percentages of PM, total PAH and total BaPeq emissions by PB40 and PB50 compared with PB0 with initially and finally conditions.
Please cite this article in press as: Phoungthong, K., et al., Comparison of particulate matter and polycyclic aromatic hydrocarbons in emissions from IDI-turbo diesel engine fueled by palm oilediesel blends during long-term usage, Atmospheric Pollution Research (2016), http:// dx.doi.org/10.1016/j.apr.2016.10.006
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K. Phoungthong et al. / Atmospheric Pollution Research xxx (2016) 1e7
Table 3 Concentration of each BaPeq measured from IDI-turbo diesel engine different conditions. Engine hour (hr)
0 400 1000
S BaPeq (mg m3) PB0
PB40
PB50
4.09 NA 9.32
2.64 NA 5.15
1.98 3.04 NA
NA: Not available.
4. Conclusions The characteristics of PM, PAHs, and BaPeq emission from IDIturbo diesel engines using PB40 and PB50, operating from 0 to 1000 h, were investigated and compared with PB0. The size distribution of PM fueled with PB0, PB40, and PB50 showed an accumulation mode. Increasing the blending ratio caused a reduction of PM, while increasing the operating time caused an increase of PM. Size distributions and concentrations of PAHs showed similar trends to PM. Using palm oil blends instead of commercial diesel reduced the emissions of PM (8.2%e33.9%), total PAHs (13.3%e 40.6%), and total BaPeq (35.4%e67.4%) significantly. It is because the PAH content of palm oil is smaller than that of commercial diesel. So, the high fraction of palm oil in the PB40 and PB50 blends results in a lower PAH emission. Also, the carcinogenic potency equivalency factors were reduced when palm oil blends were used. Palm oil has a high amount of oxygen that can enable more complete combustion than commercial diesel. However, adding too much palm oil to blends with commercial diesel would cause incomplete combustion and inhibit the release of energy from the fuel in IDIturbo diesel engines. In particular, PB50 has been shown to be unsatisfactory for long-term test usage in IDI-turbo diesel engines. As a result of engine wear to piston rods, piston rings, compression rings, and other parts, it cannot be used anymore. The test cycle for PB50 was shorter than for PB0 and PB40 at final conditions of 400 h. Therefore, it is necessary to further evaluate the environmental impacts and risks of palm oil blends before their utilisation. Physical and chemical modifications of palm oil blends for commercial diesel engines are also needed in the future, with higher fractions of palm oil blending, and mechanical adaptations to modern diesel engines or a new version.
Conflict of interest The authors have declared no conflict of interest.
Acknowledgments The financial support from Prince of Songkla University (annual research grant for fiscal years 2008e2010, No. ENG5200595) is gratefully acknowledged. The authors heartily thank Associate Professor Gumpon Prateepchaikul and the technical staff for their excellent work and assistance with relevant experimental analysis and sample collection, and Mr. Thomas Duncan Coyne for improving English of this manuscript.
Appendix A. Supplementary data Supplementary data related to this article can be found at http:// dx.doi.org/10.1016/j.apr.2016.10.006.
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