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The aim of this experiment was to analyze an alternative energy supply, biodiesel, as a substitute for traditional diesel fuel. Biodiesel offers an eco-friendly alternative to conventional diesel, making it crucial for both present and future energy needs. In this study, biodiesel was prepared using canola oil, a vegetable-based oil, and its energy content was compared to that of regular diesel fuel using an oxygen bomb calorimeter to measure temperature changes resulting from combustion reactions.
The experiment involved the combustion of benzoic acid as a reference, followed by three separate runs for biodiesel samples and three runs for regular diesel samples.
The heat of combustion values were calculated and compared between biodiesel and diesel. According to the literature, the heat of combustion value for canola oil biodiesel is 43.96 MJ/kg [5], whereas diesel has a value of 44.8 MJ/kg [15]. The experimental results yielded values of 40.71 ± 9.5 MJ/kg for biodiesel and 50.82 ± 9.9 MJ/kg for regular diesel.
These results indicate that biodiesel is a viable energy source, although its energy content is lower than that of regular diesel fuel.
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This underscores the importance of exploring additional biodiesel sources when higher energy output is required. Furthermore, the p-values obtained from the t-test were 0.58 for biodiesel and 0.35 for regular diesel, respectively. Diesel's p-value is smaller than the chosen significance level (α), indicating repeatability, whereas biodiesel's p-value is larger than α, suggesting that the experiment is not easily repeatable for biodiesel.
Energy supply stands as one of the most critical global issues today, with petroleum being the most prevalent and in-demand energy source.
As of November 2018, the production volume of petroleum reached 159 million gallons [12]. Biodiesel, on the other hand, is derived from oils through transesterification, a process that converts oils into biodiesel and glycerin [10]. The feedstock volume presents a challenge, with a total of 1,218 million pounds of feedstocks used for biodiesel production in November 2018. Soybean oil remained the primary biodiesel feedstock during that period, with 704 million pounds being consumed [12]. Other raw materials for biodiesel include corn and canola oil.
However, biodiesel offers several advantages over petroleum-based diesel, particularly in terms of environmental impact. Biodiesel emits fewer greenhouse gases, produces biodegradable byproducts, and releases fewer air pollutants [9]. This experiment aims to compare the heating values of biodiesel and regular diesel, demonstrating which fuel has a more effective heating value. In the literature, the heating value of biodiesel produced from canola oil is reported as 43.96 MJ/kg [5], while diesel has a value of 44.8 MJ/kg [15]. Diesel's heating value surpasses that of biodiesel, with a negligible 10% energy loss.
The primary objective of this experiment was to determine the heating values of biodiesel produced from canola oil and regular petroleum diesel using bomb calorimetry. To collect data, calorific values of three different biodiesel samples from canola oil and three different samples of regular diesel were measured using the bomb calorimeter. Subsequently, an equal variance t-test was employed to assess whether the experimental values significantly differed from the theoretical values.
There are several feedstock options for producing biodiesel, including vegetable oil, animal fat, cooking oil, and yellow grease [1]. Various techniques are available for biodiesel production, such as base-catalyzed transesterification of oils, direct acid-catalyzed transesterification, or conversion of oils to fatty acids and then to biodiesel. In this experiment, biodiesel was produced from canola oil using the base-catalyzed transesterification process. Canola oil is a vegetable oil containing triglycerides, which undergo a reaction with alcohol to produce esters and glycerol through the transesterification process [2]. This reaction occurs in the presence of methanol () and sodium hydroxide (NaOH) as the alcohol and catalyst, respectively.
The reactants in this process are triglycerides (canola oil) and methanol. Upon their reaction, glycerol and methyl esters, which constitute biodiesel, are formed. To separate biodiesel from glycerol, their density difference is utilized. Glycerol has a density of 1.26 g/cm³ [4], while biodiesel has a density of 0.84 g/cm³ [5]. When the product solution, which includes petrodiesel, is allowed to stand for 24-48 hours, glycerol with higher density precipitates, and biodiesel can be collected from the top of the heterogeneous mixture.
The heat of combustion is calculated to compare biodiesel and regular diesel. However, prior to conducting experiments with biofuels, the bomb calorimeter is standardized using 1 g of benzoic acid. Benzoic acid is chosen for standardization as it completely dissolves in oxygen and is therefore ideal for this purpose [9]. The energy equivalent or heat capacity of the calorimeter is determined through this standardization test, using Equation 1. In this experiment, the correction factor e1 is neglected, as titration to obtain nitric acid data is not the goal.
Equation 1: \( W = \frac{H \cdot m}{t - e1 - e3} \)
Where:
After standardization, Equation 2 is employed for calculating the net corrected temperature rise:
Equation 2: \( t = \frac{(a - b) + (c - b)}{2} \)
Where:
Once \( t \) and \( W \) values are determined, the gross heat of combustion (\( Q \)) can be calculated using Equation 3, utilizing data obtained from the bomb calorimeter. For this experiment, the corrections for \( e1 \) and \( e3 \) are neglected, as titration is not the focus.
Equation 3: \( Q = \frac{W}{t} \)
Where:
The correction factor for the fuse wire can be calculated using Equation 4. The factor for the fuse wire is typically provided on its packaging. Additionally, the weight of the wire is measured after it is removed from the bomb calorimeter.
Equation 4: \( Cwire = \frac{Winit - Wfinal}{mwire} \)
Where:
Finally, the gross heat of combustion value includes the heat of vaporization. To determine the net combustion value, the hydrogen content involved in vaporization needs to be subtracted, as shown in Equation 5. However, in this experiment, \( \text{H} \) was not calculated because the hydrogen content was not known.
Equation 5: \( Qnet = Qgross - \left(\frac{\text{H}}{100}\right) \cdot Qgross \)
Where:
This experiment was conducted in two parts. In the first part, biodiesel was synthesized from canola oil, and in the second part, bomb calorimetry was performed to determine the calorific values of the samples.
For the biodiesel synthesis:
For bomb calorimetry:
The oxygen combustion bomb is a crucial component of the oxygen bomb calorimeter. It is a robust, thick-walled metal vessel that can be opened for various actions, such as inserting samples and removing combusted products. In this experiment, fuel samples weighing 1 g were measured and placed inside the oxygen combustion bomb [13].
The digital thermometer is another essential part of the oxygen bomb calorimeter equipment. It was utilized to measure the temperature change during the experiment runs.
The oxygen bomb calorimeter is a constant-volume calorimeter, which serves as a standard instrument for estimating the calorific value of liquid and solid combustible samples. In this calorimeter, electrical energy is employed to ignite the fuel. As the fuel burns in pressurized oxygen, heat is generated. This heat causes the air inside the calorimeter to expand, and the expanded air escapes through tubes. As the air escapes, it heats the water surrounding the tubes. The temperature difference in the water is then used to calculate the calorific value of the fuel. The oxygen bomb calorimeter essentially comprises three main components: the oxygen combustion bomb, digital thermometer, and insulating jacket.
For the production of biodiesel from canola oil, the following steps were followed:
For bomb calorimetry:
Prior to conducting the experiment, safety considerations are paramount. This experiment involves the use of chemicals such as methanol, sodium hydroxide, and benzoic acid, which present specific safety concerns:
Additionally, it is essential to wear safety glasses and gloves throughout the experiment, considering the volatility of methanol and the irritability of other chemicals.
The equipment used in this experiment also requires careful handling:
Furthermore, it is crucial to clean the laboratory thoroughly after the experiment, as methanol is volatile, and other chemicals can be irritating. Ensure that all equipment is turned off upon completing the experiment.
Measurements were conducted on three biodiesel samples prepared using canola oil and three regular diesel samples during the experiment. Prior to these measurements, the oxygen bomb calorimeter was standardized using a benzoic acid sample.
The firing moment temperatures for the samples and their respective temperature changes were as follows:
The combustion reactions inside the oxygen calorimeter bomb caused temperature increases over time, resulting in different firing temperatures for each sample. The consistent temperature change difference across all samples suggests a stable experimental setup.
For the regular diesel samples, the firing moment temperatures and temperature changes were:
After recording all data, the net corrected temperature rise (t) was calculated using Equation 2, and the values were determined from the slopes of the graphs (as shown in 9.2 Sample Calculations and Graphs section). Subsequently, the heat of combustion value for each sample was calculated using Equation 3.
| Sample Type | Heat of Combustion (MJ/kg) |
|---|---|
| Biodiesel Sample 1 | 47.02 |
| Diesel Sample 1 | 46.65 |
| Biodiesel Sample 2 | 45.33 |
| Diesel Sample 2 | 43.65 |
| Biodiesel Sample 3 | 29.79 |
| Diesel Sample 3 | 62.18 |
| Average | 40.71 ± 9.5 |
| Average | 50.82 ± 9.9 |
Table 6.1 displays the calculated heat of combustion values for each sample. Comparing sample 1 and 2, we observe slight variations in values, while sample 3 values for both biodiesel and diesel samples significantly differ. This suggests the possibility of temperature change observation or diesel weight errors during the third trial.
A two-sample assuming equal variances t-test was conducted to assess the differences between biodiesel and diesel values. The results are presented in Excel tables (as shown in 9.5 Completed Excel Analysis Tables section). The significance level (α) was set at 0.05, and two-tailed p-values were obtained. The t-test results for temperature change comparison revealed that all two-tailed p-values were smaller than 0.05, leading to the rejection of the null hypothesis. Specifically, the p-values for sample 1, sample 2, and sample 3 were , , and 8.83, respectively.
Additionally, the heat of combustion values were compared using the t-test, assuming equal variances. For biodiesel, the p-value was found to be 0.58, which is higher than α=0.05, indicating that the null hypothesis cannot be rejected, and the experiment is repeatable. Conversely, for diesel, the p-value was found to be 0.35, which is smaller than α, leading to the rejection of the null hypothesis for regular diesel and indicating that the experiment is not repeatable.
Heat of combustion values were calculated for biodiesel and regular diesel samples in this experiment, with biodiesel prepared using canola oil. Three samples of each were tested, and data were recorded. The aim was to obtain more accurate results by collecting data from three separate samples. The average heat of combustion was found to be 9740.76 ± 2279.8 Cal/gr for biodiesel and 12140.16 ± 2376.6 Cal/gr for regular diesel. This experiment showed that the heat of combustion value for biodiesel was less than expected.
| Time (min) | Sample 1 Temperature (°C) | Sample 2 Temperature (°C) | Sample 3 Temperature (°C) |
|---|---|---|---|
| 0 | 31.3 | 31.3 | 35.0 |
| 1 | 31.2 | 33.2 | 35.2 |
| 2 | 31.2 | 33.1 | 35.2 |
| 3 | 31.1 | 33.0 | 35.1 |
| 4 | 31.0 | 33.0 | 35.0 |
| 5 | 31.0 | 33.0 | 35.0 |
| 5.5 | 32.2 | 34.1 | 36.0 |
| 6 | 33.0 | 35.4 | 36.4 |
| 6.5 | 33.9 | 36.2 | 36.8 |
| 7 | 34.4 | 36.6 | 37.1 |
| 7.5 | 34.8 | 36.9 | 37.2 |
| 8 | 34.9 | 37.0 | 37.3 |
| 8.5 | 35.0 | 37.1 | 37.3 |
| 9 | 35.0 | 37.1 | 37.4 |
| 9.5 | 35.1 | 37.1 | 37.4 |
| 10 | 35.1 | 37.1 | 37.4 |
| 10.5 | 35.1 | 37.1 | 37.4 |
| 11 | 35.1 | 37.1 | 37.4 |
| 11.5 | 35.1 | 37.1 | 37.4 |
| Time (min) | Sample 1 Temperature (°C) | Sample 2 Temperature (°C) | Sample 3 Temperature (°C) |
|---|---|---|---|
| 0 | 18.9 | 23.7 | 26.2 |
| 1 | 19.1 | 23.8 | 26.8 |
| 2 | 19.1 | 23.7 | 26.8 |
| 3 | 19.2 | 23.8 | 26.8 |
| 4 | 19.2 | 23.8 | 26.8 |
| 5 | 19.2 | 23.8 | 26.8 |
| 5.5 | 19.4 | 24.0 | 27.4 |
| 6 | 21.1 | 24.2 | 29.6 |
| 6.5 | 22.1 | 25.9 | 30.6 |
| 7 | 22.7 | 26.6 | 31.5 |
| 7.5 | 23.3 | 27.5 | 32.0 |
| 8 | 23.4 | 27.8 | 32.2 |
| 8.5 | 23.5 | 28.1 | 32.3 |
| 9 | 23.7 | 28.3 | 32.5 |
| 9.5 | 23.7 | 28.3 | 32.5 |
| 10 | 23.8 | 28.4 | 32.6 |
| 10.5 | 23.8 | 28.4 | 32.6 |
| 11 | 23.8 | 28.4 | 32.6 |
| 11.5 | 23.8 | 28.4 | 32.6 |
Biodiesel vs. Diesel: Combustion Analysis and Comparison. (2024, Jan 12). Retrieved from https://studymoose.com/document/biodiesel-vs-diesel-combustion-analysis-and-comparison
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