Previous to Delay Cooking Conversion Course of
There has been continued interest in the exploitation of the world’s petroleum residues for reasons related to each economic and market forecasts as well as causes of national interest to these countries in which the residues are generated and accumulated. The petroleum residue is a possible supply of artificial fuels and treasured chemicals. To be able to effectively use these petroleum residues, it is necessary that they be upgraded. A number of alternatives can be found to perform this upgrading. Catalytic upgrading of the residue is necessarily more expensive due to the higher catalyst and hydrogen consumptions. Normally, some hydro-processing will likely be required to eventually produce completed products however the high funding and operating prices of hydro-processing may be mitigated by the introduction of non-catalytic processes to improve residues [Bello, et. al. 2001]. Among the many upgrading processes, delayed coking is natural gas 3x bull more necessary due to its low investing and working costs, broad feed inventory applicability and excessive conversion [Elliot, et. al. 1981]. Delayed coking is a severe type of thermal cracking during which the viscosity and pour point of the liquid hydrocarbon base material is completely decreased after it has been subjected to extreme temperature for a period of time at comparatively low strain under inert condition.
A number of investigators Jiazhi, et. al. 2002a; Zacheria, et. al. 1982; Bonila, 1982; Jiazhi, et. al. 2002b] have reported the outcomes of deasphalting and thermal conversion of Athabasca oil sands, Arabian heavy crude, Orinoco heavy crude, Lloydminster heavy oil, Loda (Nigeria) tar sand and Marguerite lake bitumen as feedstock under number of operating situations. For the reason that petroleum residue characteristics fluctuate drastically from one area to another, delayed coking application issues and solutions additionally differ. Process circumstances which might be efficient in one system will not be all the time successful in others because most purposes are these developed for tar and oil sand bitumen and never from petroleum derived fluids or petroleum based mostly fractions.
While the problem of delayed coking upgrading has been addressed by numerous research [Bello, et. al. 2001; Ukwuoma, 1993; Elliot, et. al. 1981; Schucker, 1983; Zacheria, et. al. 1982; Bonila, 1982; Jiazhi, et. al. 2002b], data relating delayed coking product spectrum to Nigerian petroleum residue traits is not accessible. Such data could foster design concepts and optimization strategies for using a vast accumulation of petroleum residues in all of the nation’s refineries. The current work tries to offer a better description of the conversion of Nigerian petroleum refinery residue to synthetic fuels and chemicals using delayed coking reactor system at numerous working conditions. The impact of process variables similar to temperatures, response time and chemical additives on the natural liquid product (OLP) yield and kinetics was studied.
Materials AND Methods
The vacuum residue of Nigerian medium gravity crude was used in this examine. The physical properties of the residue are given in Table 1. Detailed procedures for characterizing the residue has been reported elsewhere [Bello, et. al. 2001].
The experimental aspects of the present research consist basically of (a) thermal conversion of the residue with methanol-potassium hydroxide and methanol followed by (b) chromatographic analysis of the samples of the products obtained from the thermal upgrading experiments.
Equipment and Experimental Procedure
The thermal conversion of the petroleum residue was studied in a delayed coking reactor system with additive concentration and additive-to-residue ratio been diverse. The system is comprised of the following parts; reactor and transport, a trapping and analyzing. This reactor was used to thermally crack the petroleum residue, which was adopted by upgrading with the additive techniques. The reactor was fabricated from 316 stainless steel tubing, 50mm in inner diameter enclosed in a much bigger cylindrical pipe of about 80mm in outside diameter. The tubular vessel and its greater enclosure were each held in place by a flange of 80mm exterior diameter with 19.1mm thickness. The annulus consists of an electric heater able to heating the feed pattern to the desired temperature. Here, below precise temperature management, the desired pattern cracking may be achieved. The service fuel, which is nitrogen gasoline, transports the cracked pattern to the shell and tube condenser. It has been demonstrated that the residence within the reactor does not range by greater than ±10% [Jiazhi, et. al. 2002a]. The reactor is capable of being operated at temperatures of up to 600ºC and at residence time of zero to one hundred twenty minutes. The products of thermal conversion are cooled in a shell and tube condenser, collected, characterized and analyzed using analytical equipment. The schematic diagram of the experimental setup is proven in Figure 1.
The experimental runs were carried out at low pressure in a batch reaction system operated natural gas 3x bull throughout the temperature range of 200-6000C and residence time of 30 to 120 minutes. In a typical run, the petroleum residue was fed into delayed coking reactor. Previous to delay cooking conversion course of, the Nigerian refinery gasoline oil was purged with nitrogen within the reactor for 10 minutes to take away residual oxygen. The Nigeria refinery fuel oil was heated at 8000C/s to reaction temperatures between 100 and 6000C and maintained at that temperature for 30 to a hundred and twenty minutes. Utilizing a shell and tube condenser, the ensuing gaseous product stream was condensed and colleted in a vessel. On the conclusion of each run, the yields were measured. For some experiments, the Nigerian residue samples charged into the reactor was dosed with varied amounts of methanol and alcoholic potassium hydroxide loading and additive-to-residue ratio. A T-shaped agitator was used to achieve correct mixing during response to ensure uniformity of reaction. The process was repeated for every half-hour, until the overall residence time for each isothermal operation was 120 minutes. The gaseous product steam was passed by means of a condenser and the liquid product collected.
The liquid product had a single homogeneous phase, and a few of those product samples have been distilled at 2000C and 172 Pa using a Buchi GKR-fifty six distillation unit. No residue was noticed after this distillation. This reveals that substantial cracking of the non-volatile fraction of the petroleum residue had occurred in the course of the upgrading course of. Due to this fact, all different liquid products have been directly analyzed by a fuel chromatography (Carle GC-500) with a banded non-polar (methyl silicone) 50m x zero.2mm i.d. capillary column and a flame ionization detector (FID). The compounds present within the liquid product had been recognized by utilizing commonplace compounds and by GC-MS (Finningan/MAT-4500). The entire weight of every component class of the distillate was determined from the share of every component class in the total merchandise collected.
Thermal Upgrading of the Petroleum Refinery Gas Oil in the Delayed Coking Reactor
The petroleum residue samples have been examined on the apparatus natural gas 3x bull and delayed coking checks had been performed for every petroleum residues at eight response temperatures (250, 300, 350, 450, 500, 550, and 600ºC). The results reported listed below are averages of a minimal of four exams performed per petroleum residues at every response temperature. The product yields are listed in Table 2. The product yields from assessments performed at 4000C temperature were repeatable as illustrated by the standard deviation of the measured gentle oil given in Desk 2. The standard deviation was between 0.2 and 4.Zero% and was usually lower than 2.0%. Approximately zero.5% of this variation could also be due to the accuracy of the stability used to determine the yields.
Experiments had been carried out also to review the characteristics of strong and liquid merchandise obtained from eleven samples of petroleum residues with different properties (particular gravity, apparent viscosity, pour point, sulfur content material, and many others) had been used as feed. Various bodily characteristics of the liquid product obtained in the course of the thermal remedy of petroleum residues are additionally presented in Tables 2 and 3. A comparability of the physical properties of whole petroleum residues and liquid product derived from thermal upgrading of petroleum residues reveals that the viscosity and density of liquid product had been decrease than those of the original petroleum refinery fuel oil. Chemical composition of the liquid product obtained throughout thermal remedy of petroleum residues is introduced in Table four. The liquid product consisted of forty nine.1 wt% aliphatic hydrocarbons, 23.5 wt% aromatic hydrocarbons, and 12.Four wt% naphthenic hydrocarbons, aside from minor fraction of phenols, ketones, alcohols, acids and esters. For a given remedy time, the two merchandise yields increased with therapy temperature, the outcomes are shown in Figures 2 and three. The noticed pattern of the yield confirmed that growing the treatment temperature and time might improve the yield of the 2 products.
Effects of Additive System and Additive-to-Residue Ratio on Product Traits and Response Kinetics
The relative proportions of the products spectrum obtained from with the use of methanol and methanolic potassium hydroxide mixture at various solvent-to-residue ratios used are as proven in Desk 4. For the two additive systems, the share of the aromatic compounds increase with rising ARR. Nevertheless, the proportion is higher at every stage obtained with methanolic potassium hydroxide mixture than within the methanol system. This could also be as a result of the truth that these chemicals had undergone cracking response involving rupture of carbon-carbon bonds yielding lighter hydrocarbons Nevertheless, since an aliphatic content material of lower than 40.0wt% was reported for the petroleum residue used [Bello, et. al. 2001], the trend needs to be attributable to methanol enhancing effect involving the capture of carbon species by free radical created throughout the delayed coking response. The high yield of aliphatic hydrocarbons in the presence of methanol and potassium hydroxide strongly point out these additives to be promoters of the cracking response. This might be as a result of the truth that there was elevated response resulting from addition of methanolic potassium hydroxide aiding decomposition of petroleum residue sample.
It would also be because of the truth that alcohol and potassium hydroxide provide the chance for chemical response through the conversion because of the nucleophilicity of the alcohol hydroxyl group and the tendency of the alcohol to act as a hydrogen donor. It’s thought that such methanol enhancing effect could contain the capture of carbon species by free radial created through the delayed coking cracking response. This results in the return of extra cracked liquid reactant fraction to the vapor section. Thus, the methanol provides a better percentage of aromatic hydrocarbons than methanolic potassium hydroxide, probably due to its better selectivity in direction of aromatics. The results of feed conversion and distillate yields as features feed properties, various methanol and potassium hydroxide concentrations and ARR at reactions temperatures and time of 400ºC and a hundred and twenty minutes respectively are as presented in Desk 4. In the absence of methanol the yield of coker distillate elevated as coking temperature was elevated from 100oC to 500ºC, at 250ºC no appreciable change in the yield of coker distillate was observed for petroleum residue samples containing as much as 5 percent methanol.
Figures four shows the results of kinetic evaluation of the process response, with the conversion for given response temperatures and concentrations plotted as a features of time. The diploma of the conversion response was observed to rely on the response concentration and temperature. The higher conversion from the progress of reaction plots is that observed when 24% methanol was added. Figure four additionally shows the impact of initial focus of methanol on the rate of conversion of the petroleum residue to hydrocarbons. As will be seen, the methanol has relatively excessive effect on the general conversion course of. It is thought that such methanol enhancing effect could involve the capture of carbon species by free radical created throughout the delayed coking response. This outcomes in the return of extra cracked liquid reactant fraction to the vapor phase. The response rate information obtained in this research had been analyzed using first-order response model. This mannequin is the one which finest fits the results of earlier workers for the kinetics of heavy oil conversion course of. The present research confirms this mechanism. Arrhenius plots for the rate constants obtained from the least-sq. regression applied to the database is proven in Figure four. Activation energy of 24.5Kcal/mol was obtained. Efficiency of the petroleum residues thermal course of improve with the rise in temperature and initial potassium hydroxide concentration. A conversion process effectivity of 70% was achieved at working temperature of 500ºC, 24% methanol and 0.6M potassium hydroxide. On the premise of the kinetic research and consequence introduced the knowledge of the conversion kinetic will facilitate the design of efficiently operating delayed coking batch reactor. Also, limitation within the equipment used on this study didn’t allow finishing up the process under steady conditions. Such work should be undertaken if the method is to be totally evaluated for doable industrial utility of petroleum residues thermal conversion process.
The exploratory examine of upgrading Nigerian petroleum residue in a delayed coking reaction system has indicated that it is sensible to produce top quality liquid merchandise by delayed coking of the petroleum residue at high temperature and low stress with chemical additives. Outcomes obtained from the experimental work shows that working temperature, residence time, additive concentration loading and additive-to-residue ratio have necessary influence on the efficiency of petroleum residue to fuels and chemicals. The OLP and aromatic hydrocarbon selectivities adopted the order methanolic potassium hydroxide > methanol > no additive. High Outdated and aromatic hydrocarbon selective for methanol potassium hydroxide had been due to methanol enhancing impact involving the seize of carbon species by free radical created throughout the delayed coking response.
The OLP yield was maximum at 350ºC and a most fraction of 83 wt% of OLP consisted of aromatic hydrocarbons using two methanol-potassium hydroxide at optimum response temperature and a residence time of two hours. The OLP obtained with out methanol additive consisted of the next fraction of aliphatic hydrocarbons whereas that with methanol-potassium hydroxide mixture contained extra aromatic hydrocarbons. The OLP yield was roughly ¼ of the petroleum residue with 83wt% selectively for aromatic hydrocarbons. Larger residence time was desirable for prime OLP yield in all of the three thermal conversion circumstances. Therefore, it is recommended that an evaluation of this course of below steady mode may be carried out.
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