1. Introduction
Upgrading the purification processes to deal with extra-heavy waste crude oil poses a major challenge in the petroleum industry to produce high-quality liquid fuel from environmental pollutant materials [1,2,3]. Huge quantities of extra-heavy waste crude oil have been produced from the petroleum activates at petroleum sites. All of these wastes have been collected in large emergency pits near the petroleum site and regarded as a high source of pollution for the soil and groundwater [4,5,6,7]. Usually, heavy crude oil is a complex mixture that includes normal paraffins, aromatics, and naphthenes. Moreover, this waste causes extended economical loss and environmental and human health problems [8,9,10,11]. Therefore, the recovery of these materials and upgrading their structure using the thermal cracking process provides a key solution to this problem [12,13,14,15,16].
The thermal cracking process is a very effective technology for providing fractions of low boiling points for different industrial applications. This process is usually operated at a range of high temperatures and pressures to convert high-molecular-weight hydrocarbons into smaller ones [2,13,17]. Typically, heavy crude oil contains significant quantities of asphaltic compounds that can lead to serious technical problems in unit operations [14]. Most asphaltenes consist of high-molecular-weight polyaromatic compounds carrying long aliphatic hydrocarbons and alicyclic substituents. Ghashghaee and Shirvani [3], Wang et al. [7], and Corma et al. [18] indicated that the main benefit of the thermal cracking process is to produce light and middle distillates from heavy petroleum crude and products such as reduced crude, fuel oil, vacuum residue, and asphaltic and waxy oil. Salehzadeh et al. [13] showed that the major parameter controlling the thermal cracking process of heavy crude oil is temperature, with the optimal range between 350–500 °C [7]. Additionally, the thermal cracking process is highly affected by the operating pressure: as the pressure increases, so do the thermal cracking reactions [1,3].
According to the literature, cracking reactions are complex and undergo more interactions due to the large number of chemical reactions that occur inside the reactor [10,17]. Therefore, the composition of waste crude oil, reaction temperature, pressure, and gas flow rate are the chief variables that determine the quality of the produced liquid fuel [18]. Usually, such waste oil contains high quantities of heavy hydrocarbon materials, including asphaltene [19,20,21,22] and resins [23]. Therefore, the thermal cracking process must be properly controlled to successfully manage the process of liquid fuel production with low amounts of undesired by-products (i.e., gases and coke) [24,25,26,27,28]. Evaluating the changes in the product specifications during the cracking reactions is necessary due the complexity of upgrading these reactions [29,30,31,32,33,34].
Furthermore, many authors have identified the influence of operating conditions on the distribution of thermal cracking products. Several publications have shown that product quality is mainly dependent on the chemical composition, specifications, and asphaltene content [35,36,37,38,39,40]. AlHumaidan et al. [41] investigated the thermal cracking reactions of vacuum residues of heavy crude oil in a semi-batch reactor. They noted the formation of cracked oil, gaseous products, and pitch from the reaction and observed a clear increase in the produced saturate fraction due to the cracking process. Rueda and Gray [42] indicated that thermal cracking technology is a valuable process that reduces the viscosity of heavy crude oil. They pointed out that the produced liquid fuel from thermal cracking can be transported via pipeline with high flexibility without the need for added solvents. Al-Absi and Al-Khattaf [43] compared the results of the thermal and catalytic cracking processes that were carried out for a crude oil of API = 34. They found that for both processes, the production of light olefins, gaseous products, and coke formation increased with increasing operating temperatures. The authors noted that the catalytic cracking process was preferable to the thermal one because the first process relies on the free radical mechanism, but the later uses the carbenium ion mechanism. Wang et al. [44] studied the influence of saturates, aromatics, resins, and asphaltene compounds on the activity of heavy crude oil cracking reactions. The authors observed that resins and asphaltenes produced high yields of residues of about 22 and 45%, respectively. Voronetskaya and Pevneva [45] tested the thermal cracking of heavy oil resins and asphaltenes in a batch reactor at an operating temperature of 450 °C. They found significant structural variations in these materials, with a high production rate of solid condensation compounds.
Heavy crude oil is characterized by its high content of asphaltic compounds, which form about 5–15 wt% depending on the nature of the crude oil [39,46]. This material consists of complex hydrocarbon frameworks, with the main constituents of asphalt being bitumens [23,47]. Moreover, the term “asphaltic bodies” is widely used to describe the amount of precipitated asphalt in hydrocarbon fuel or lubricating oil. Thus, the mass of the asphalt can be determined by subjecting the fuel to a centrifugal process to remove the asphaltic bodies as precipitated compounds [48,49,50,51,52]. Additionally, the thermal cracking reaction usually occurs by the free radical mechanism. This mechanism consists of a series of reaction stages involving the initiation of the hydrocarbon chain, the H2 abstraction process, radical decomposition, radical addition, and finally, a termination stage [26,43].
Previous studies have rarely dealt with the treatment of waste crude in an emergency pit [7,8]. These pits usually cause high environmental and human health risks. Additionally, most studies have identified the performance of the thermal cracking process according to the change in product distribution [8,34,51]. However, these studies do not explain the influence of transport processes and reaction mechanisms on the chemical quality of the products [5,42,52]. Therefore, the main aim of the present study was to investigate the removal of extra-heavy crude oil from an emergency pit and then evaluate the production ability of high-quality liquid fuel from low-value waste via an efficient, controlled thermal cracking process.
2. Materials and Methods
2.1. Materials
In the present work, extra-heavy waste crude oil was used as a raw material in a cracking reaction. This type of oil was collected from an emergency pit in one of the petroleum sites outside the boundaries of Baghdad (East Baghdad Oil Field). Figure 1 presents some photographs of this emergency pit, whereas Figure 2 shows the fluid nature of the collected extra-heavy waste crude oil. Using ASTM D445, the kinematic viscosity of the extra-heavy waste crude oil was measured to be 172.3 cSt at 25 °C.
2.2. Thermal Cracking Apparatus
The thermal cracking reaction was carried out in a semi-batch reactor. Figure 3 illustrates the thermal cracking apparatus, whereas Figure 4 shows a photograph of the semi-batch reactor. The reactor was constructed from stainless steel and was 500 mL in size. The reactor was heated uniformly by an electrical heater that surrounded the reactor. In addition, the reaction temperature inside the reactor was controlled with the aid of a highly sensitive temperature control system using a K-type thermocouple sensor with a digital temperature controller. The operating pressure was measured and controlled via a sensitive pressure gauge with an accurate needle. Moreover, the apparatus was supplied with a chiller system to cool the products in the reactor. The apparatus also had a nitrogen gas cylinder with a calibrated flow meter. Moreover, the reactor and all connected sections were insulated with a layer of fiberglass material to prevent heat loss from the apparatus.
2.3. Cracking Reaction Procedure
The thermal cracking reaction for the extra-heavy waste crude oil was conducted in a semi-batch reactor. For each reaction run, 100 mL of feedstock was charged inside the reactor and cracked thermally under different operating temperatures and pressures. The cracking process was evaluated at various reaction temperatures (i.e., 400, 425, and 450 °C). To evaluate the influence of the operating pressure on the cracking process, each reaction was achieved at a selected set of operating pressures (i.e., 1, 3, 5, and 7 bar). Moreover, before starting the reaction process, the apparatus was supplied with nitrogen gas at a flow rate of 20 mL/min for 10 min to remove any traces of oxygen in the system. The reaction time continued for 3 h under continuous stirring using an electrical stirring motor and shaft system inserted inside the reactor with a constant mixing velocity of 120 rpm under sealing conditions. Then, the products were cooled using a chilling system, after which they were accumulated in a cylindrical collection system designed for this purpose. Next, the amount of produced liquid fuel was determined. Additionally, after completing the thermal cracking reaction, the reactor was opened and the amount of the precipitated coke was determined. Then, the amount of produced gases was estimated by subtracting the amount of liquid fuel and solid coke from the parent amount of feed to the reactor.
Furthermore, the product specifications and characterization were evaluated using many measuring techniques, such as Fourier-transform infrared (FTIR) spectroscopy (8400S/Shimadzu, Kyoto, Japan). Additionally, a thermogravimetric analysis (TGA) (TG-760 thermobalance, Stanton Redcroft, London, UK) was used to evaluate the thermal behavior of the parent extra-heavy waste crude oil. Then, to perform the TGA analyses, 8 mg of parent crude oil was distributed in alumina crucibles with a capacity of 100 μL. The oxygen was fed to the device at a volumetric flow rate of 50 mL/min and a heating rate of 20 °C/min. Additionally, the parent crude oil viscosity was measured using a Brookfield-DV3TLVKJ viscometer (USA). Finally, the crude oil density (specific gravity) was measured using a special hydrometer (L50SP, Stevenson Reeves Ltd., Edinburgh, Scotland). Then, the API gravity value was determined according to the general equation of API gravity [20,49].
3. Results and Discussion
3.1. Thermogravimetric Analysis (TGA)
Table 1 illustrates the measured values of the physical properties of the parent waste of the extra-heavy crude oil. From the API value (6.83), it is clear that this crude oil was extra heavy and highly viscous. Moreover, the thermal characteristics of this extra-heavy crude oil were analyzed using thermogravimetric measurements to determine the best operating temperature for the cracking reaction. Figure 5 shows the TGA thermogram of the parent extra-heavy waste crude oil at different operating temperatures. The TGA results pointed to the presence of two reaction zones. The first reaction zone was related to a distillation process combined with a low-temperature oxidation (LTO) process of the compounds of the crude oil. This zone was achieved in a temperature range between 25 and 400 °C. However, the second reaction zone took place at an operating temperature higher than 400 °C due to the high-temperature oxidation (HTO) process employed for the remainder of the crude oil. The same trend was noted by Avendaño et al. [29]. Additionally, the results indicated that the operating temperature played a key role in the quality of the extra-heavy oil. It was noted that up to 95 °C, no coke formation precipitated. The weight of the coke precipitated at 180 °C was about five times higher than that at 140 °C.
To understand the thermal cracking process of crude oil, its mass-loss behavior provided a clear picture of the distribution of the produced gases included in the thermal cracking reactions. Corma et al. [18] and Hao et al. [20] indicated that the thermal cracking conditions (e.g., operating temperature, pressure, and heating rate value) play a significant role in controlling the reaction performance and product distribution. Heavy crude oil is composed of various kinds of fractions, such as saturates compounds, volatile aromatics, asphaltenes, and resins. The effective solubility and polar activity of hydrocarbons usually determines the main features of the fractions. Then, from a thermal point of view, asphaltene hydrocarbons possess high thermal resistance caused by various operational problems in the petroleum processing units. The asphaltic compounds consist of a complex hydrocarbon matrix. Therefore, the asphaltic bodies look like colloids dispersed in petroleum. Accordingly, asphaltene is usually precipitated in storage tanks and pipelines due to its ability to precipitate according to this mechanism [6,29,30,40].
3.2. Influence of the Temperature on the Cracking Reaction
The cracking reaction of extra-heavy waste crude oil using a semi-batch reactor was investigated at temperatures of 400, 425, and 450 °C and operating pressures of 1, 3, 5, and 7 bar. Figure 6, Figure 7 and Figure 8 illustrate the influence of the thermal cracking temperature and operating pressure on the quantity of produced gases, liquid hydrocarbon, and solid residue, respectively. Figure 6 demonstrates that the amount of gaseous products (C1–C3) was highly influenced by the operating temperature and pressure. The highest gas production was observed at an operating temperature of 450 °C and a pressure of 7 bar, whereas the lowest gas production rate was noted at 425 °C. These results are attributed to the ability of C5–C12 hydrocarbons in the crude oil structure to crack, which forms more gaseous products. Additionally, the results indicated that at the lower thermal cracking temperature of 400 °C, slight levels of waste crude oil cracking were noted at a reaction time of 2 h. Feedstock cracking was enhanced by increasing the operating temperature, as gaseous products increased to 28 and 52% at 425 and 450 °C, respectively. In addition, the feedstock molecules underwent major changes as the cracking temperature was raised, causing a clear breakdown of long-chain molecules into smaller hydrocarbons (gases). Moreover, the breaking down of the paraffinic compounds present in asphaltenes and also the cracking of smaller compounds will contribute to the formation of more cracking gases. The observed results were similar to the results reported by Ghashghaee and Shirvani [3], Yu et al. [12], Cheshkova et al. [25], and Wang et al. [44].
Hochberg et al. [19], Jin et al. [33], and Wang et al. [44] showed that the general products of cracking reactions are usually paraffins, olefins, and aromatic compounds. Additionally, light gases (e.g., methane, ethane, and propane) are the main gases generated from thermal cracking reactions, although other gases including CO, CO2, and H2 have formed [18,26,40]. The composition of these gases highly depends on the operating pressure and temperature [39,45]. Thus, the suggested thermal cracking process in the present work can be regarded as an efficient solution for the reuse of extra-heavy waste crude oil from emergency pits. Additionally, light hydrocarbons can be produced without any environmental and economic problems. The controlled thermal degradation of crude oil in this process will enhance the physical specifications of the product. The amount of produced light liquid fuel in the present work was about >61% at a temperature of 400 °C and pressure of 3 bar. The comparison of the results of the present work with that of other previous work indicated that the amount of light fuel is less than this value. Alsobaai [19] found the produced fuel from thermal cracking of heavy crude oil was in the range of 27–44%. Additionally, Guerra [26] and Afanasjeva et al. [28] observed that thermal cracking generates light crude oil of about 30 and 36%, respectively. According to the investigation of Wang et al. [44], the thermal cracking process of crude oil can produce more than 30 wt% of coke. However, in the present work, the coke formation is in the range of 10–18 wt%. Accordingly, it can be said that the amount of coke formation from the cracking process does not only depend on operating temperature, but also on crude oil specification. Crude oil with a higher mass of asphaltene formed more coke and residue.
Waste crude oil has been produced everywhere in petroleum production processes and petroleum refineries [30,46]. The collection of these wastes in an emergency pit has caused environmental problems that are fatal to humans and has also polluted groundwater [6,8]. However, the present work provides efficient solutions to this problem using thermal cracking technology, where high-quality crude oil was produced using waste crude oil. The environmental problems in petroleum sites can be resolved significantly, and emergency pits can then be removed from such sites.
3.3. Effect of the Pressure and Temperature on the Quality of the Liquid Product
This study measured the effect of the operating pressure on the produced liquid hydrocarbons during the thermal cracking of waste crude oil. Table 2 shows the influence of the operating pressure of the produced liquid hydrocarbons at different operating temperatures. As the operating pressure increased, the API gravity of the produced liquid hydrocarbons increased up to 5 bar for all samples at various operating temperatures. At 400 °C, the highest value of the API gravity was 30.5 for the produced liquid fuel at a pressure of 3 bar. Moreover, as the operating pressure increased, the API gravity decreased slightly. Additionally, at a thermal cracking temperature of 425 °C, the API gravity reached its highest value of 28.65 at a pressure of 5 bar. On the other hand, Table 2 shows that there was no significant effect of pressure on the API value at a temperature of 450 °C. This behavior is attributed to the nature of the thermal cracking reaction mechanism, in which at a high thermal cracking temperature (450 °C), the cracking reaction produced more gases than liquid fuel [1,25,42]. This mechanism is related to the bond breaking of most high-molecular-weight hydrocarbons and the formation of C1, C2, and C3 gaseous products. The same observation was noted by Kok [4], Al Darouich et al. [27], Jiao et al. [37], and Kaminski and Husein [40].
3.4. FTIR Analysis
The functional groups of the parent extra-heavy waste crude oil were evaluated using Fourier-transform infrared (FTIR) analysis. This analysis is the most applied method to obtain accurate information about the nature of the crude oil and the composition of the affected functional groups. Figure 9, Figure 10, Figure 11 and Figure 12 present the spectra results of the parent and the produced liquid fuel. Figure 9 illustrates the functional groups attached to the parent extra-heavy waste crude oil. The two notable peaks at 2922.77 and 2853.95 cm−1 represent the aliphatic C−H group and were produced from the symmetric and asymmetric vibration activity. Additionally, a clear aromatic vibration band was noted at 1641.96 cm−1, related to the aromatic compounds. Moreover, the resulting band at 722.28 cm−1 corresponds to the crystallinity of the wax that appeared in the crude oil structures [20]. Additionally, the bands that lie between 900.05 and 810.38 cm−1 usually appear in asphaltenic compounds and resins in heavy types of crude oil [20,29,39].
Figure 10, Figure 11 and Figure 12 show the functional groups attached to the structure of the produced liquid fuel from the thermal cracking process at 3 bar and at 400, 425, and 450 °C, respectively. These samples underwent clear shifting in their general bands in comparison with the parent extra-heavy crude oil. This shifting is attributed to the thermal cracking reaction processes. To evaluate the effect of the operating temperature on the TGA results, a comparison between different bands was achieved, as shown in Table 3. This table clearly illustrates that the main characteristic bands of crude oil appeared at 2923.27 cm−1 and 2853.88 cm−1. Moreover, the aromatic ring compounds disappeared in products at the three operating temperatures due to the removal of the asphaltic material, which was converted into coke by the thermal cracking process. Additionally, the O−H stretching disappeared from the light crude structure because of the high operating temperature. Furthermore, the −CH2 bending that was noted at 722 cm−1 varied slightly in all samples. These figures unambiguously indicate the presence of a general band of light crude oil. This band is related to the carboxylic acids and aromatic hydrocarbons at 1743 cm−1 and 1698 cm−1, respectively. Additionally, Figure 10, Figure 11 and Figure 12 show the disappearance of the OH− group (3406.37 cm−1 in the parent feed in Figure 9) in the produced liquid fuel samples at different operating temperatures due to the liberation of physical and chemical water from the crude oil structures [7,39].
Additionally, a precipitated coke formed in the reactor after the reaction time was complete. Then, the FTIR spectroscopy showed a significant disappearance of all the produced fuels at the later bands between 900.05 and 810.38 cm−1 (Figure 10, Figure 11 and Figure 12). These results are attributed to the precipitation of most of the asphaltenic and resin compounds in the reactor in the form of coke. According to the results of Salehzadeh et al. [13], Li et al. [15], and Cheshkova et al. [25], the asphaltene compounds represent the general body of coke formed by the thermal cracking reactions. Additionally, the gaseous products from the thermal cracking reaction were C1–C3, CO, CO2, and H2 gas. The quality and quantity of the produced gases are highly dependent on the type of crude oil and its composition [28,34,41].
3.5. Transport Processes and Reaction Mechanism
The transport processes that occur in the thermal cracking reactions of crude oil are complex and require a deep understanding. A high rate of heat transfer will be achieved inside the reactor due to the thermodynamic performance of the cracking reactions (endothermic reactions). Usually, the activation energy of this type of reaction is dependent on the nature of the bond to be broken during the reaction path. Accordingly, the heat will be transferred from the reactor wall into the crude oil mixture depending on the required operating temperature. Nargessi and Karimzadeh [5], Ishiyama et al. [16], and AlHumaidan et al. [41] have stated that the transferred energy is mainly distributed between the reactor wall and crude oil mixture. In addition, the amount of energy transfer in the reactor plays a major role in determining the quality of the product distribution. Evaluating the mass transfer variation in the system will contribute to a clear understanding of the real reaction mechanism and performance in the thermal cracking process. The thermal cracking process normally undergoes faster mass changes due to the higher rate of hydrocarbon cracking occurring in the reactor. Therefore, three main parts of the products were achieved in the present semi-batch reactor: liquid hydrocarbon, a gaseous product, and precipitated coke.
Some researchers have found that increasing the contact between the reaction mixture highly influences the heat and mass transfer processes inside the reactor [17,41,45]. However, the enhancement in the heat transfer rate is related to there being more contact surface area due to the agitation process. Figure 13 summarizes the main reaction sequences that occurred in the semi-batch reactor for the waste crude oil thermal cracking process. The general reaction mechanism of thermal cracking is dependent on the free radical mechanism [26]. This mechanism is supported by three basic operations: initiation, propagation, and termination, as shown in Table 4. Experimental work related to this mechanism by Guerra [26], as well as by Al-Absi and Al-Khattaf [43], has shown that all of these processes together form the total picture of thermal cracking products. When compared with the catalytic cracking process, thermal cracking does not occur by ionic intermediates [27,42]. Instead, in this case, the C−C bonds were broken, leaving each C atom to be finished by a single electron [12,40]. This produces free radicals, which allows different products to be synthesized from the results of thermal cracking reactions.
Finally, extra-heavy waste crude oil is an undesirable material formed during petroleum production activities. The high viscosity of this material is attributed to the existence of long-chain hydrocarbons. In this study, the specifications of the thermal cracking product were improved in comparison with those of the parent waste crude oil. Thus, the proper management of transport processes in the reaction vessel during thermal cracking will enhance the conversion of extra-heavy waste crude oil into light oil with a higher value. It was found that the heat and mass transfer determines the quality of product, with reaction kinetics and thermodynamics playing a primary role in the yield of light crude oil. Therefore, the results showed the ability of the thermal cracking reaction of crude oil to maximize both the economic and environmental benefits of this process.
4. Conclusions
The pollution problem of accumulated extra-heavy waste crude oil in an emergency pit was solved successfully using thermal cracking technology. This work assessed the applicability of converting extra-heavy waste crude oil of API = 6.83 into a light liquid fuel of API = 30.5 via controlled thermal cracking reactions in a semi-batch reactor. This produced a high yield of high-quality synthesized crude oil with low coke deposition. The results indicated that the cracking temperature and operating pressure are the major parameters that determine the quality of the produced fuel. High liquid products (>61%) were achieved under the optimal operating conditions of 400 °C and 3 bar. Moreover, it was found that there was no significant effect of the pressure on the API value at a temperature of 450 °C. This behavior is attributed to the nature of the thermal cracking reaction mechanism, in which at a high thermal cracking temperature (450 °C), the cracking reaction produced more gases than liquid fuel. Furthermore, comparisons of the produced liquid fuels with the parent extra-heavy crude oil at different operating temperatures indicated that these fuels underwent clear shifting in their general FTIR bands due to the thermal cracking reaction processes. Additionally, the standard functional groups of light crude oil were achieved in the produced fuels. A mass transfer and reaction mechanism of thermal cracking was suggested to explain the increased efficiency of producing liquid hydrocarbons by this process. The improvement in liquid fuel quality was related to the chemical reactions of converting high-molecular-weight compounds into those with low-molecular weights with limited mass transfer resistance. Thus, by this mechanism, free radicals were produced, and different products can be synthesized from the results of such thermal cracking reactions. Furthermore, utilizing extra-heavy waste crude oil provides a new source of petroleum fractions from low-value material that is both economical and has a flexible production rate.
Conceptualization, R.A. and K.A.S.; methodology, S.I.H.; formal analysis, R.A. and S.I.H.; investigation, K.A.S.; data curation, S.I.H.; writing—original draft preparation, R.A.; writing (review and editing), K.A.S.; visualization, R.A.; supervision, H.S.M.; project administration, H.S.M. and K.A.S. All authors have read and agreed to the published version of the manuscript.
Not applicable.
Not applicable.
Not applicable.
The authors are thankful to the Design & Production Research Unit/Department of Chemical Engineering, University of Technology-Iraq and Al-Mustaqbal University College, Babylon, Iraq for their scientific support of this project.
The authors declare no conflict of interest.
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Enlarge this image.Figure 1. Photographs of the emergency pit at East Baghdad Oil Field, showing the extra-heavy waste crude oil.
Enlarge this image.Figure 4. Photograph of the semi-batch reactor used for the thermal cracking process.
Enlarge this image.Figure 6. Influence of the thermal cracking temperature and operating pressure on the quantity of the produced gases.
Enlarge this image.Figure 7. Influence of the thermal cracking temperature and operating pressure on the quantity of the produced liquid hydrocarbons.
Enlarge this image.Figure 8. Influence of the thermal cracking temperature and operating pressure on the quantity of the precipitated residue.
Enlarge this image.Figure 10. FTIR spectroscopy of the produced liquid fuel at T = 400 °C and 3 bar.
Enlarge this image.Figure 11. FTIR spectroscopy of the produced liquid fuel at T = 425 °C and 3 bar.
Enlarge this image.Figure 12. FTIR spectroscopy of the produced liquid fuel at T = 450 °C and 3 bar.
Specifications of the extra-heavy waste crude oil.
| Property | Standard | Value |
|---|---|---|
| API Gravity at 15 °C | ASTM D5002 | 6.83 |
| Specific Gravity at 15 °C (g/cm3) | ASTM D-1298 | 0.98 |
| Water Content (Vol%) | ASTM D1744 | 8.00 |
| Sediment (Vol%) | ASTM D4807 | 0.50 |
| Sulfur Content (wt%) | ASTM D4294 | 3.60 |
| Salt Content (ppm) | ASTM-D3230 | 400 |
Effect of the pressure and temperature on the API gravity of liquid products.
| Temperature (°C) | Pressure (Bar) | API |
|---|---|---|
| 400 | 1 | 28.29 |
| 3 | 30.50 | |
| 5 | 29.29 | |
| 7 | 27.2 | |
| 425 | 1 | 26.91 |
| 3 | 27.34 | |
| 5 | 28.65 | |
| 7 | 27.15 | |
| 450 | 1 | 27.88 |
| 3 | 26.00 | |
| 5 | 26.93 | |
| 7 | 26.88 |
Comparison between the main TGA results of the produced liquid fuels at different thermal cracking temperatures.
| Functional Group | Parent Waste Crude Oil | Produced Fuel at 400 °C | Produced Fuel at 425 °C | Produced Fuel at 450 °C |
|---|---|---|---|---|
| Aliphatic C−H | 2922.77 cm−1 2853.95 cm−1 | 2923.27 cm−1 2853.88 cm−1 | 2922.96 cm−1 2853.97 cm−1 | 2923.13 cm−1 2853.90 cm−1 |
| C−H Deformation of −CH2 and −CH3 | 1459.74 cm−1 | 1458.64 cm−1 | 1458.15 cm−1 | 1458.57 cm−1 |
| C−H Symmetric Deformation of −CH2 | 1377.07 cm−1 | 1376.89 cm−1 | 1377.09 cm−1 | 1377.06 cm−1 |
| Aromatic Ring | 1641.96 cm−1 | - | - | - |
| O−H Stretching | 3406.37 cm−1 | - | - | - |
| −C−H Bending | 722.28 cm−1 | 724.16 cm−1 | 724.26 cm−1 | 723.68 cm−1 |
Radical mechanism that occurs during thermal cracking reactions [
| Reaction Type | Description |
|---|---|
| Initiation Stage | Alkane + Heat [Image omitted. Please see PDF.] 2 Radicals |
| Propagation Stage | Alkane + Radical [Image omitted. Please see PDF.] (Radical + H) + Radical |
| Termination Stage | Radical + Radical [Image omitted. Please see PDF.] Hydrocarbons Products |
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1 Department of Chemical Engineering, University of Technology-Iraq, Al-Sanna St., P.O. Box 19006, Baghdad 10066, Iraq
2 Midland Oil Company, Ministry of Oil, P.O. Box 19244, Baghdad 10081, Iraq
3 Chemical and Petroleum Industries Engineering Department, Al-Mustaqbal University College, Hilla 51015, Iraq