A Study on Particulate Emission Characteristics of Diesel Engine Using a Mixture of Commercial Diesel and Biodiesel Based PalmOil

Currently, oil and gas accounts for about 60 80% of the world's energy. According to scientists, with the current consumption rate, this source of energy will be exhausted in the next 40-50 years; Therefore, finding alternative energy sources has become the goal of many countries. In particular, the sources of energy friendly to the environment and renewable such as wind energy, solar energy, bioenergy ... are given top priority. Biodiesel is a liquid biofuel with similar properties and can be used as a substitute for conventional diesel oil. Testing and proceeding to apply B5 and B10 fuels to vehicles will reduce the amount of toxic emissions and replace exhausted petroleum and gas sources. This paper focuses on the KDE3500T engine test bed at 50% loading to analyze and assess the emission of particulate matter and oxidized organic compounds. With different mixing ratios between commercial gasoline of 0.05 S and palm oil biodiesel from 10% to 75%. Experimental results show that the particle emission concentration decreased by about 30% from B0 to B20 and increased by about 15% from B30 to B100. While carbonyl compounds such as formaldehyde, acetaldehyde and acetone increased about 2.5 times from B0 to B30 and dropped abruptly at B50, however carbonyl concentration increased by about 28% when using B75 to B100.


I. INTRODUCTION
Biodiesel is a liquid biofuel with similar properties and can be used as a substitute for conventional diesel oil. In the past time, with the goal of economical and efficient use of energy, minimizing the harmful emissions released into the environment, implementing the roadmap of applying the mixing ratio in biofuel according to Decision 53/2012QD-TTg of the government. There have been many ministerial and state research projects on the application and deployment of pilot application of mixing materials B5 (5% biodiesel + 95% normal diesel) and B10 (10% biodiesel + 90% conventional diesel) into transportation [1]. On average, from 2015 to 2018, harmful emissions released into the environment when using conventional diesel fuel are quite large, of which: CO is 1960.9 tons; NO2 is 1018.19 tons; CO2 is 262582.4 tons ... Testing and progressing the application of B5 and B10 fuels to HSR will reduce the amount of toxic emissions and replace exhausted petroleum and gas sources [2]. Moreover, many domestic and foreign scientific studies have shown that biodiesel is truly a clean green energy source because their use helps reduce emissions of serious pollutants such as CO, SO2, NOx, and CxHy compounds [3], [4]. However, the emissions from the combustion of biodiesel fuel in diesel engines of organic compounds are small but very toxic and affect the ambient air environment [5]. Around as carbonyl has not been fully studied in Vietnam and in the world.
Biofuels are produced from animal or plant-derived compounds such as animal fat, coconut oil, palm oil, grains (wheat, corn, soybean), agricultural residues (straw, corn stalks, beans), industrial waste (sawdust, waste wood), ... [6]. Compared to traditional fuels, biofuels have many outstanding advantages such as: no increase in branding greenhouse, reduce environmental pollution [7]. Moreover, biofuel sources are capable of regenerating from agricultural production activities, thus reducing dependence on traditional fuel sources that are unable to regenerate [8] [9]. Depending on the mode of production and the intended use, biofuels can be classified into the main categories: original vegetable oil and biofuel after processing [10]. The extracted original vegetable oil is very simple, just go through the process of pressing oilseed nuts (palm, mustard seeds, sunflower seeds, sesame, peanuts …), then filter out all the residue and the water is can be used as a fuel. The first diesel engine first built by Rudolf Diesel in 1893 also runs on this fuel. Processed biofuels include biodiesel, biodiesel (ethanol) and natural gas (biogas). In these groups, bio-gasoline is commonly used for gasoline engines, biodiesel suitable for diesel engines [11].
In terms of structure, biodiesel has lower carbon content (C), sulfur (S) and water than diesel, but has more oxygen content in the component. Low carbon content will reduce CO, CO2 and soot emissions on the discharge road [12]. The sulfur content is low and almost nonexistent, so it does not produce SO2, a gas that affects the respiratory tract, heart failure, pneumonia and causes acid rain. Oxygen components facilitate biodiesel to burn completely over diesel, reduce CO emissions and unburnt fuel (hydrocarbon-HC) [13].
Carbonyl compounds (CBCs -Carbonyl compounds) are organic compounds with a carbonyl functional group consisting of a carbon atom that is coupled to an oxygen atom. The simplest compounds of carbonyl groups are aldehydes and ketones. CBCs are considered toxic because they are capable of causing allergies or cancer in humans [14]. Among them, formaldehyde, acetaldehyde, acrolein, propional dehyde and butanol have been listed by the US Environmental Protection Agency (USEPA) as toxic gases for human health [4]. Moreover, CBCs are also precursors A Study on Particulate Emission Characteristics of Diesel Engine Using a Mixture of Commercial Diesel and Biodiesel Based Palm-Oil Van Viet Pham that form ozone in the atmosphere [5], [15]. Therefore, it is derived from the above reasons: "Evaluation of carbonyl compounds emission from biodiesel diesel generator" was conducted by the authors to provide a view more comprehensive emission of diesel engines using biodiesel to better manage air quality and promote research on carbonyl emissions. The objective of this study is to assess dust emissions and emissions of CBCs in the emissions of diesel generators using palm oil as biodiesel fuel.

A. Test Engine and Fuels
Seven types of fuel were used in this study. Diesel fuel (DO oil) 0.05 S distributed by Saigonpetro oil and gas company on the market (symbolized as B0). The second type of fuel is biodiesel palm oil synthesized by the team of the Department of Chemistry, University of Natural Sciences, Hanoi, in a scientific and technical cooperation project with Osaka Prefecture University (Japan) (B100) (The chemical and physical properties of diesel and palm oil are shown in Table 2). Two types of oils B0, B100, in addition to being considered as the two fuels used for research, are also two types of base fuels for mixing 5 remaining fuels, B10 (90% B0 + 10% B100), B20 (80% B0 + 20% B100), B30 (70% B0 + 30% B100), B50 (50% B0 + 50% B100) and B75 (25% B0 + 75% B100).
All experiments are performed on the KDE3500T diesel generator running in average load mode (1.5 kW). The specifications of the generator are shown in Table 1. The sampling equipment and generators are illustrated in Fig.1.

B. The Process of Sampling Emission Particles
Prepare filter paper: GF/C 47 mm glass fiber filter paper (47 mm filter paper diameter) Whatman -Japan, heated at 450 o C for 8 hours to remove organic matter. Then, the filter paper is wrapped in aluminum foil and placed in a desiccator for 48 hours. After dehumidifying, weigh the filter paper to determine the weight. Preparing the cartridge: Using SiO2 cartridge -C18 has already prepared 2,4-DNPH of Waters, USA. Sampling: Add fuel and run the generator for 15 minutes to stabilize the engine.
The exhaust gas entering the sampling pipeline (the end of the pipe) is diluted 10 times with clean gas (the surrounding air has been removed impurities and moisture by silica gel column -activated carbon) in Teflon tubes. by Mass Flow Controller (MFC) as follows: first, use MFC control system to adjust the flow of clean gas to dilute (MFC 1) to 0.36 L / min and final flow Pipeline (MFC 2) is 0.4 L / min. The head pipe exhaust flow is the difference between MFC 2 and MFC 1 flow of 0.04 L / min, respectively. The dilution factor is the numerical quotient between the end pipe flow and the first pipe gas flow of 10. The exhaust gas temperature after dilution is 50 0 C (to avoid the melting of DNPH). After 10 minutes, start turning on the suction pump to take the sample, first the exhaust gas after being diluted by clean air will then pass through a 47 mm diameter fiberglass filter paper to retain the total amount of dust present in the exhaust gas, after going through the exhaust air filter paper will go through ozone scrubber to remove ozone (to avoid the influence of ozone on compound 2,4 -DNPH and DNPH hydrazine derivatives), followed by carbonyl compounds in the waste gas will be retained in 2,4-DNPH impregnated cartridge, eventually exhaust after cartridge will go into the suction pump and exit. Sampling speed is 0.4 L/min, the sampling time is 10 minutes, the experiment is repeated 3 times.

C. Determination of Mass of Particle Emissions and Carbonyl Analysis
After sampling, the filter paper sample is doubled, wrapped in aluminum foil to avoid photochemical and placed in a desiccator at room temperature for 48 h. Then, the filter paper is placed on the electronic scale to determine the amount of dust on the filter paper.
For the cartridge after sampling, it will be wrapped in aluminum foil, put in ziplock bag and stored at -4°C in a cooler, until analyzed. Carbonyl compounds adsorbed in SiO2 -C18 cartridge will react with 2,4 -DNPH in the cartridge to form stable derivatives of 2,4dinitrophenylhydrazone. These derivatives will be eluted from the cartridge with 5 mL of acetonitrile and analyzed by high-pressure liquid chromatography of UV probes of Shimadzu (Japan) [16].

A. Fuel Consumption and Discharge of Smoke
The discharge of flue gas from diesel generators is measured in Testo 512-2 (Germany), and the fuel consumption rate is measured by determining the volume of fuel consumed by the generator for a certain period of time. From Figure 2, it can be seen that: for the fuel consumption rate of diesel generator (F) when increasing the blended biodiesel content, the fuel consumption rate of the machine at 1.5 kW load mode does not change much (range from 10.72 mL/min to 13.40 mL/min). Besides, the discharge of flue gas from diesel generators (Q) has not changed significantly (ranging from 1.75 m 3 /min to 1.81 m 3 /min). From this, it can be concluded that when increasing the amount of biodiesel in fuel used to run diesel generators, the amount of emissions and fuel. The consumption of diesel engines has not changed much.

B. Total Amount of Particulate Emissions of Fuel
The emission of particulate matter (PM) consists of three main forms: soot, sulfate particles formed during combustion and high-volume hydrocarbons derived from fuel or shaped finished during combustion adsorption on soot [18]. Emission dust of fuels B0 (diesel), B10, B20, B30, B50, B75, B100 from diesel generator engines running at medium load conditions (1.5 Kw) is held by GF/C fiberglass filter paper 47 mm Whatman. The dust content of the emission is determined based on the weight of the filter paper before and after sampling. In total dust emission of diesel generators, dust concentration varies with each type of fuel, ranging from 168.59 mg/m 3 to 522.98 mg/m 3 .  Figure 3 it can be seen that the particulate emission concentration of B10, B20, B30, B50, and B75 is less than that of B0, but the dust emission concentration at B100 is larger than that of B0. In summary, PM emissions decrease when the rate of biodiesel increases from 0 to 20% in the fuel mixture and gradually increase when biodiesel rate increases from 20-100%. The cause of the change in dust emissions can be explained as follows: Biodiesel Fuel (BDF) is of biological origin so it does not contain aromatic hydrocarbons and sulfur compounds in its burning composition in the combustion chamber of diesel engines, biodiesel does not form sulfate and hydrocarbon particular [19]. Therefore, in fuel mixes containing BDF (B10, B20, B30, B50, B75) dust emissions decrease compared to diesel fuel (B0). However, the viscosity of the fuel mixture increases in proportion to the percentage of BDF in the diesel and biodiesel mix. This has affected the fuel injection in the engine, thereby hindering fuel combustion in diesel combustion chambers and increasing dissolved organic compounds (solube organic fraction -SOF). adsorption on dust particles emitted by generators increases dust mass [20]. That is why the concentration of dust begins to increase gradually from B30 onwards until it exceeds the dust concentration of B0 at B100. The results achieved in this study are similar to those of Yuan-Chung Lin and Charles Peterson. Lin and collaborators conducted a study to assess dust emissions from biodiesel oil palm oil on generators at a load of 75%, the results showed that compared to conventional diesel fuel, dust emissions decreased from fuel B10, B20, B30 respectively 51.0%; 21.4%; 4.6%, whereas dust emissions increased at B50, B75 and B100 at 10.9%; 26.9% and 29.3% [14]. Similarly, the research results led by Charles Peterson showed that dust emissions of palm oil from rapeseed decreased by 6.08% at B20 and increased by 4.1% at B50, 16.8% at B100 compared to B0 [21]. Figure 4 shows that the total carbonyl concentration emitted in diesel emissions gradually increases as the proportion of biodiesel palm oil increases at 1.5 kW except for the fuel use regime at B50. Compared with B0, the increase is 28.61%; 45.75%; 48.49%; -3.24%; 50.49% and 50.58% correspond to B10, B20, B30, B50, B75 and B100 in 1.5 kW load mode. This result can be explained by considering the carbonyl concentration from B0 to B30. For pure diesel fuel (B0), the formation of carbonyl compounds in engine exhaust is the result of incomplete combustion of hydrocarbon compounds in the fuel. Normally, when burning straight-chain alkane compounds (commonly found in fossil fuels) under oxidation conditions, these alkanes are in turn transformed into alcohols, carbonyl compounds, and then carbides. acid, then ester types and finally CO2 [22]. However, no engine with a combustion efficiency of 100% and therefore incomplete combustion of diesel fuel will produce a multitude of toxic compounds such as carbonyl compounds [12]. As for the fuel mixes between diesel into biodiesel (B10, B20, B30) although in the city. The part of biodiesel does not contain carbonyl compounds [23] and therefore in theory when BDF is burned, it will not produce carbonyl compounds, but as mentioned above the concentration of carbonyl increases gradually from B0. to B30. Therefore, the gradual increase of carbonyl compounds in engine exhaust at B10, B20 and B30 fuels compared to B0 is due to the combustion of ester compounds in biodiesel fuel [24]because biodiesel fuel combustion is the process of cutting carbon vessels of ester molecules with long carbon chains into hydrocarbon compounds with shorter circuits and during the circuit breaker of the ester molecule (R1 -CO -O -R2 ). The C -O bond is the most frequently disconnected link during the circuit cut and forms carbonyl compounds (R1 -CHO) [25]. So burning ester molecules in biodiesel is the main cause of carbonyl emissions from biodiesel fuels [26].

C. The Concentration of Carbonyl Compounds in The Emissions of Each Fuel
Next is the explanation of carbonyl concentration in B50 fuel. According to Figure 4, the carbonyl concentration at B50 is the lowest compared to other fuel levels. The results of this study are similar to the results of the study from Hoang and colleagues [24]. In which the fuel levels B0, B10, B20, B30, B50, B75, B100 are studied in turn to investigate the change of carbonyl emissions. The results show that the B50 has the lowest carbonyl emissions (lower than carbonyl emissions at fuel B0) in all the studied fuels [27]. This result can be explained by biodiesel fuel with high cetane index ( Table 2) and oxygen content that exist more than diesel [28]. Fuel with a high cetane index will reduce the delay time of the fuel in the engine and make the combustion process more radical, causing the emission content of the hydrocarbon compounds to decrease, and the high oxygen content. will help increase the efficiency of combustion and emission reduction [29]. However, Figure 4 shows that only when B50, carbonyl content declines clearly, but in previous fuels (B10, B20, B30), there is a tendency to increase the carbonyl content of emissions. This can be explained as follows: when the ratio of mixing fuel reaches B50 (with 50% diesel and 50% biodiesel), it is enough biodiesel content in the fuel mixture to promote the burning process in a way more comprehensive and reduce carbonyl emissions [30].
Finally, the explanation of carbonyl emission concentrations at B75 and B100. Although the percentage of biodiesel fuels in B75 and B100 fuels is 75% and 100% (higher than B50), Figure 4 shows the carbonyl emission concentration of B75 and B100, which still follow the higher and higher trends. compared to the remaining fuels (as opposed to the B50 trend). The cause of this phenomenon is because the viscosity of BDF palm oil is larger than DO so when the ratio of BDF palm oil is high in the fuel mixture (B75 and B100), the viscosity of the fuel mixture is also High and affect fuel injection process of engine [31], making fuel burn more slowly than normal [32]. This makes the combustion of the engine fuel incomplete and thus creates more emissions [33], especially the emission of carbonyl compounds. Research by Hoang and colleagues also showed an increase in carbonyl emissions compared to B50 when diesel engines operate in B75 and B100 fuels [34].

IV. CONCLUSION
This study is to analyze and evaluate the concentration of particulate emission and carbonyl compounds of KDE3500T engine using biodiesel blends from B10 to B100 at the external characteristics at 50% load. Research results show that: The concentration of particulate emissions ranges from 167.47 mg/m 3 to 530.26 mg/m 3 when using fuels from B10 to B100. When the biofuel content is still low (from B0 to B20), the concentration of particulate emissions tends to decrease (about 20%), meanwhile, as the participation of biofuels increases (from B20 to B100), the emission of particulates is greatly reduced due to the addition of oxygen content in the fuel, resulting in better combustion quality.
Measurements show that high concentrations of carbonyl compounds are formaldehyde, acetaldehyde and acetone. In particular, the formaldehyde, acetaldehyde and acetone compounds account for three quarters of the total carbonyl compounds emitted, the remaining 12 carbonyl compounds account for only 25% of the total carbonyl compounds emitted. Besides, the analysis results of carbonyl emission concentration showed an increase of 27.47%, 42.72%; 45.74%; -4.21%; 51.39% and 53.35%, respectively, with B10, B20, B30, B50, B75 and B100 compared to B0.
The lack of measuring and testing equipment on the prototype engine using diesel fuel without the fuel conversion system has increased the data error. Using biofuels will not only reduce the pressure on fossil fuels but also reduce particle emissions into the environment.