This study determines using B20 on the main and twin filters after 3 months of use. Furthermore, filter analysis with B0 fuel was conducted on these two types of filters as references, and strainers for B20 and B0 were not analyzed because they only captured large-size material (such as rocks or gravel). Therefore, deposits of B20 fuel were not captured.
3.1 Photo of Fuel Filter
The visual inspection result of the used main filters with B20 and B0 fuel after 3 months using a 3D digital microscope at a magnification of 500 times is shown in Figure 2. While the deposit's thickness was assessed at 100 times magnification, as shown in Figure 3.
In the used main filter for B20, it can be seen that the fibers have been tightly covered with a material deposit, while for the B0, the fiber and porosity were still clearly visible. The result of deposit thickness measurement showed that B20 was higher with an average of 822 µm compared to B0 with an average of 699 µm. Meanwhile, the type of deposit on the main filter with B20 fuel was soft, and hence, even though it appeared to cover the surface, fuel still flowed with less resistance, and the delta pressure filter test did not change significantly. Likewise, the performance test results showed that the decrease of power was not significant after using B20 for 3 months .
Figures 4 and 5 show the deposit's morphology on the twin filter for B20 and B0 with a 200 and 500 times magnification, respectively. It can be seen that after 3 months of usage, the fibers were still visible, both for the used filters of B0 and B20. However, the granule deposit which covers the filter surface had a different size. Petrodiesel (B0) tent formed a smaller size of granule deposit compared with B20.
The cross-section of the deposit thickness show that B20 has an average of 601 µm and B0 has 621 µm as shown in Figure 6. This can be considered because the contaminants for B20 have been filtered on the main filter, hence, the filtration process at twin filter is lighter.
3.2 Identification of trapped materials or chemicals on the filter
Analysis with GCMS was conducted to determine which deposit components were filtered on the main and twin filters with B20 or B0 fuels. Furthermore, the identification of trapped materials or chemicals on the used filter was analyzed by FTIR, elemental analyzer, and TGA. The used filters were soaked in four organic solvents before GC-MS analysis, namely acetone, chloroform, dichloromethane (DCM), and n-hexane. The identified chemicals on this filter using B0 fuel for each solvent are shown in Table 2.
According to Table 2, among the four organic solvents used to dissolve chemicals in the used filter, chloroform appears to be better than acetone, dichloromethane, and n-hexane due to many chemicals identified. There were two compounds not identified with the chloroform solvent but identified with the n-hexane solvent. The results of the identified compounds were a combination of compounds dissolved in chloroform and n-hexane. Therefore, the chemical compounds contained in the filters were obtained. Based on the combination identified compounds with chloroform and n-hexane (Table 2), the chemicals trapped on the used filter were hydrocarbons with the number of atoms of C12 - C27, and the dominant one was pentadecane, 2,6,10,14-tetramethyl- (C19H40). Alkane hydrocarbon compounds over C16 are solid at 20 °C. Therefore, C17 and above were naturally trapped and caused a blockage on the filter. C12 - C16 compounds were identified because there was no pretreatment to the filter before soaking in the organic solvent, meaning that it was still left on the filter, although the hydrocarbons C12 - C16 at 20 °C in the liquid phase.
Furthermore, naphthalene compounds caused blockage because of a high melting point and solid at room temperature. As the main diesel component, the alkane group dominated the precursor deposits. The deposit contained tetradecane, pentadecane, and hexadecane.
The identified chemicals on the used filter with B20 fuels for each solvent can be seen in Table 3. Based on Table 3, chloroform was a better solvent than others in dissolving chemicals trapped on the used filter with B20 fuel. However, some compounds could not be dissolved by chloroform but dissolve in acetone, DCM, and n-hexane. The chemicals identified in the four organic solvents were combined as shown in Table 3, with the percentage of peak areas mainly dissolved in chloroform. The chemicals were alkane hydrocarbons and fatty acid methyl ester, mainly Hexadecanoic acid, methyl ester (C15H30O2), and 9-Octadecenoic acid, methyl ester, (E) - (C19H36O2).
The hydrocarbons were almost the same as Table 2, which was derived from petrodiesel. Meanwhile, fatty acid methyl ester compounds derived from palm biodiesel. Chemical compounds such as Methyl tetradecanoate and Tridecanoic acid 12-methyl-, methyl ester were derived from Fatty acid C14 (myristic acid) that solid phase at room temperature. Likewise, Hexadecanoic acid, methyl ester, and Methyl stearate derived from C16:0 (palmitic acid) and C18:0 (stearic acid) fatty acids, respectively, can cause filter blockage. Next, 8,11-Octadecadienoic acid, methyl ester, and 9-Octadecenoic acid, methyl ester, (E)- were derived from C18:1 fatty acid (oleic acid) that liquid phase at room temperature. Therefore, it can be concluded that the large peak areas (corresponded to high concentrations) of Hexadecanoic acid, methyl ester (C15H30O2) and 9-Octadecenoic acid, methyl ester, (E) - (C19H36O2) were caused by a high concentration of palmitic and oleic acid in the palm oil and no pretreatment on the used filter before soaking. Nevertheless, methyl esters derived from oleic acid do not cause filter blocking. Therefore, the precursor deposit component for the B20 filter was dominated by fatty acid methyl esters, although based on the measurement results, the deposit was also caused by alkane hydrocarbons.
Moreover, the used filter with B20 fuel was analyzed by FTIR to support chemical identification of the GC-MS results and compared with the new one. The FTIR analysis results and prediction of functional groups for each peak are shown in Figure 7 and Table 6, respectively.
Based on FTIR analysis, the peaks that appeared on a new filter generally also appeared on the used filter. However, several new peaks appeared on the used filter, such as wave numbers 1259 and 1232 cm-1 which were predicted to be the C-O-C group from ester, which was probably derived from biodiesel. Furthermore, the predicted wavenumbers 626 and 468 cm-1 were the naphthalene groups. The peak at wave number 609 cm-1 was predicted as -SO2- group derived from petrodiesel fuel.
The used filter is also analyzed with an elemental analyzer to determine the percentage of carbon, hydrogen, and oxygen in the filter compared to the new one, as seen in Table 7. Elemental analysis results showed that the contents of carbon [C] and hydrogen [H] in the used filter increased compared to the new one by 20.4 % and 3 %, respectively, caused by fuel or engine crust passed through the filter. The nitrogen [N] content was very small and can be neglected as a trace element. Meanwhile, the oxygen content [O] in the new filter was the oxygen from the filter material. The oxygen content in the used filter was lesser than the new one because of high added carbon from trapped fuel, while the O value was calculated based on the difference between the percentages of C, H, and N. As the percentage of C and H increased, the O percentage decreased. The value of detected O in the used filter was predicted derived from the filter component, fuel, or sulfur. Also, sulfur estimation was known from FTIR analysis at peak 609 cm-1 (Table 6) because the elemental analyzer could only detect C, H, and N.
Moreover, the used filter was analyzed by Thermogravimetric (TG) and Differential Thermogravimetric (DTG) analysis to understand its thermal properties compared with the new filter. Figure 8 shows the TG and DTG analysis results of the used and the new filters at N2 conditions with a heating rate of 10 ⁰C min-1 from room temperature to 600 ⁰C. Comparing the TG and DTG curves between the used (Figure 8a), and the new filters (Figure 8b) showed thermal degradation of the used filter consisted of three decomposition areas, namely 35 - 150 °C; 150 - 320 °C; and 320 - 400 °C, while the new one only consisted of two areas of 35 - 150 °C and 250 - 400 °C. In 35 - 150 °C, it was predicted as water evaporation and volatile compounds decomposed from the filter material. Furthermore, in the new filter, the next decomposition occurred at 250 - 400 °C, which was predicted the larger molecular weight material, such as polymer or composite, be decomposed. Next, in the used filter at 150 - 320 °C decomposition or evaporation of fuel with the number of carbon atoms [C] ranging from C13 - C18 such as Tridecane, Tetradecane, Pentadecane, Hexadecane, Tridecane, and Octadecane (Table 2 and 3). Meanwhile, in 320 - 400 °C, there was decomposition or evaporation of a larger number of carbon atoms [C] ranging from C19 - C27, such as Nonadecane, Eicosane, Heneicosane, Docosane, Tricosane, Heptacosane, Tetracosane, Pentacosane, and Eicosane.