In the current Malaysian market, B5 biodiesel fuel, which consists of 5% palm methyl ester (PME) blended with 95% diesel fuel, is used to replace diesel fuel consumption. However, research shows that emulsified diesel fuel with a higher bio-oil percentage will lead to few disadvantages, such as corrosion problems and lack of engine performance. As explained above, there are few disadvantages to consider before launching this emulsified diesel fuel into the market.
They claim that biodiesel emulsified fuel has higher corrosion rates and higher gas emission rates compared to pure diesel fuel. Research claims that even stable emulsions of pyrrole bio-oil and diesel fuel form stratification after a certain induction time. Comparative study between pure bio-oil, pure diesel fuel, 10% and 20% bio-oil mass fraction of emulsified diesel fuel.
In this study, the properties of diesel fuel will be benchmarked against emulsified biodiesel fuels B10 and B20.
Palm Methyl Ester (PME)
Both are because PME has fewer unsaturated molecules susceptible to oxidation through carbon double bonds. Simple alcohols are used for transesterification and this process is usually carried out with a basic catalyst (NaOH, KOH) in the complete absence of water. In the transesterification process, the alcohol combines with the triglyceride molecule from the acid to form glycerol and an ester.
The density and viscosity of palm oil methyl ester, formed after transesterification, was found to be very close to petroleum oil. Brake thermal efficiency is higher compared to diesel at partial and full load.
Metals in Car Engine
Alloys 321 (S32100) are stabilized stainless steels whose main advantage is excellent resistance to intergranular corrosion after exposure to temperatures in the chromium carbide precipitation range of 800 to 1500°F (427 to 816°C). Due to their good mechanical properties, stainless steels 321 and 347 are also suitable for use at high temperatures. Alloys 321 and 347 stainless steels offer higher creep and stress fracture properties than Alloy 304 and especially Alloy 304L, which can also be considered for exposures where sensitization and intergranular corrosion are a concern.
The corrosion tests were carried out by immersing four different metals in the bio-oil and emulsion samples. All the metal strips were machined to 2 cm in length and 1 cm in width, 1.5 mm in thickness for stainless steel strips and 2 mm in thickness for the other metal strips. The metal strips were cleaned and polished with silicon carbide paper and weighed, then immersed in 50 ml glass bottles containing 30 ml oil samples.
After drying with tissue paper, the strips were weighed and then returned to the bottles until the next weighing time. This source claims that using emulsified fuels compared to pure bio-oil reduced the corrosion rate. This result is discussed to have such effects because diesel is the continuous phase in the emulsions and the contact area between the metal surface and bio-oil is limited.
Comparing the two emulsions, the bio-oil concentration of emulsion B is three times higher than that of emulsion A, but the corrosion rate of emulsion B to three metals is less than twice that of emulsion A. Nadeem, C .Rangkuti, K.Anuar, M.R.U Haq, I.B.Tan and S.S Shah, University Teknologi Petronas (2009), they have done research on diesel engine performance and emission assessment using emulsified fuels. The diesel engine test bed (FORD, XLD 418) was used to study performance (engine torque, power, brake mean effective pressure, BMEP and specific fuel consumption, SFC) and emissions (PM, oxides of nitrogen NOx, carbon monoxide CO and sulfur oxides SOx) characteristics using neat diesel and emulsified fuels respectively.
This study shows that nitrogen oxides (NOx), carbon monoxide (CO) and particulate matter (PM) were reduced using the emulsified fuels instead of pure diesel. While emulsion fuels have higher specific fuel consumption (SFC) and produced less torque, power and brake mean effective pressure (BMEP) compared to pure diesel, but the difference is negligible.
Project Flow Chart
- Corrosion Testing
- Engine Performance Testing
Research is very important in the project to give a strong background or good basic knowledge about this project. As biodiesel fractions become emulsified over time, water comes into contact with the engine surface, causing corrosion. Remove the metal strips at 24 and 48 hour intervals and wash them with ethanol for two minutes.
The result will be the weight change of the metal strips. more weight loss indicates higher corrosion). Results will be displayed in the form of line graphs and compared between the fuel types. This test will be done on SFC (specific fuel consumption), torque and power of engine running on these test fuels.
How bio-oil properties such as high density, viscosity and high water content will affect the performance of emulsified diesel fuel. Is there significant improvisation of performance for emulsified biodiesel compared to diesel and bio-oil. The results will be the data produced by the equipment and software connected to the test bed engine.
This engine is connected to TEC equipment (Figure 3.3) which provides readings of engine speed (RPM), power, torque, exhaust temperature, air consumption and 8 ml fuel consumption gauge.
- Engine Performance Test
- Corrosion Test
For the weight change method, the results obtained are as in Table 4.4 and Table 4.5 below. For this method, the initial weights of the samples are measured using the microgram calibrator before they are immersed in the specified fuels. Negative value of weight change indicates weight loss of the metal sample while positive value of weight change indicates increase in weight of the metal sample.
- Engine Performance
The results show that stainless steel experiences weight gain in all three types of fuel immersion and the amount of weight gain is almost the same amount. In addition, compared to Figure 4.5, the analysis shows that mild steel experiences more weight loss at 70oc. Stainless steel is a metal that does not corrode with difficulty and is less responsive to any chemical reaction.
But in this case, the stainless steel strip shows some weight loss, possibly caused by errors during the execution period of the experiment. However, stainless steel experiences weight gain under most conditions because sedimentation occurs on the metal surface during the immersion process. This SEM image shows that mild steel has an uneven and uneven surface even before testing.
This may be because the high magnification factor (500X) is very precise where every detail on the metal surface is visible. Referring to Figure 4.10 (a), (b) and (c) above, all three final SEM images of metal surfaces illustrate more damage and uneven surface compared to the original image in Figure 4.9. This is due to the corrosion that developed on the metals during the immersion test and led to weight loss of the metals.
Comparing between the images of Figure 4.10 and Figure 4.11, the surface conditions of the images of Figure 4.11 show more damage and more corroded surfaces. In Figure 4.12 below, the image of the stainless steel surface shows a smooth and uniform surface condition before the immersion test. All three images show almost similar surface conditions to the initial surface condition as in Figure 4.12.
However, these stainless steel metals still show smooth and undamaged surface as the initial condition in Figure 4.12. The chemical components that are traced to the mild steel metal surface after the immersion test are mostly oxygen (O) and ferrum (Fe). These results support the weight gain shown in the immersion test above, which sedimentation of these components is one of the main causes of the weight change for stainless steel.
The obtained results show that Ferrum (Fe) is the most traceable component on the metal surface, followed by chromium (Cr), nickel (Ni), etc.
The analysis of engine performance test results showed that B10 and B20 biodiesel fuel have almost the same engine performance as diesel fuel. The results also show that the fuel consumption of B10 and B20 fuel increases slightly compared to diesel fuel. While the torque and engine power produced by these emulsified fuels are almost equal to the performance of diesel fuel.
From the results obtained and the analyzes performed, it has been proven that the corrosiveness of B10 and B20 fuel is higher than commercialized diesel fuel. Although diesel fuel shows some signs of corrosion on mild steel specimens, they are negligible as the amount of weight loss is very small. From the weight loss results, it also shows that B20 fuel is more corrosive than B10 fuel as mild steel experiences more weight loss in B20 fuel.
This is because; at a temperature of 70°C, the amount of weight loss for mild steel is higher compared to a temperature of 25°C. At the same time, longer immersion period also leads to more weight loss as more corrosion takes place. Stainless steel also does not experience weight loss in most conditions, proving that stainless steel is less corrosive or almost does not corrode compared to mild steel.
In general, biodiesel B10 and B20 have great potential to replace diesel fuel in the market as it has almost similar properties and performance. For the methodology of the project, I would like to suggest improvisation and checking the quality of test fuels, because in this project, the quality of emulsified fuels is not tested before conducting corrosion and engine performance testing. This is because; the corrosion process in a hydrocarbon environment is a very slow process that requires a longer period of time to investigate the actual behavior of the corrosion properties of the tested fuels.
Referring to the results obtained, the weight change of the metal strips is only at microgram level, which is very minimal and negligible. Thus, testing with longer time interval and higher temperature can lead to a larger amount of weight change, which can give a better trend of the corrosion behavior.