Papers by davood iranshahi
Chemical Engineering and Processing, 2011
In the current research, an exothermic reaction is proposed to be coupled with naphtha reforming ... more In the current research, an exothermic reaction is proposed to be coupled with naphtha reforming reactions. Hydrodealkylation (HDA) of toluene, which is a well-known petrochemical reaction, is discussed and is suggested as a potential exothermic reaction to be coupled with the endothermic naphtha reforming reactions. The first, the second, and the third reactor of the conventional naphtha reforming process have been substituted in three different cases by thermally coupled reactors and optimized parameters of the final case have been investigated. Considering lower operational costs due to the elimination of inter stage heaters, investigation of thermally coupled reactors has been the first priority of this research. The investigation shows that substitution of the first two reactors and, in the final case, all conventional reactors by the new configuration can improve the production yield of the aromatics by 14% and 21%, respectively compared with conventional naphtha reforming process. The final case has been optimized as well, and 45% and 11% improvement in aromatics and hydrogen production has been observed.
Chemical Engineering Research & Design, 2011
Since in the foreseeable future liquid hydrocarbon fuels will play a significant role in the tran... more Since in the foreseeable future liquid hydrocarbon fuels will play a significant role in the transportation sector, methanol might be used potentially as a cleaner and more reliable fuel than the petrochemical-based fuels in the future. Consequently, enhancement of methanol production technology attracts increasing attention and, therefore, several studies for developing new methanol synthesis reactors have been conducted worldwide. The purpose of this research is to reduce the pressure drop and recompression costs through the conventional single-stage methanol reactor. To reach this goal, a novel axial-flow spherical packed bed reactor (AF-SPBR) for methanol synthesis in the presence of catalyst deactivation is developed. In this configuration, the reactor is loaded with the same amount of catalyst in the conventional single-stage methanol reactor. The reactants are flowing axially through the reactor. The dynamic simulation of the spherical reactors has been studied in the presence of long-term catalyst deactivation for four reactor configurations and the results are compared with the achieved results of the conventional tubular packed bed reactor (CR). The results show that the three and four stages reactor setups can improve the methanol production rate by 4.4% and 7.7% for steady state condition. By utilizing the spherical reactors, some drawbacks of the conventional methanol synthesis reactors such as high pressure drop, would be solved. This research shows how this new configuration can be useful and beneficial in the methanol synthesis process.
International Journal of Hydrogen Energy, 2010
In this study, a novel thermally coupled reactor containing the naphtha reforming process in the ... more In this study, a novel thermally coupled reactor containing the naphtha reforming process in the endothermic side and the hydrogenation of nitrobenzene to aniline in the exothermic side has been investigated. Considering the higher thermal efficiency as well as the smaller size of the reactor, utilizing the recuperative coupled reactor is given priority. In this novel configuration, the first and the second reactor of the conventional naphtha reforming process have been substituted by the recuperative coupled reactors which contain the naphtha reforming reactions in the shell side, and the hydrogenation reaction in the tube side. The achieved results of this simulation have been compared with the results of the conventional fixed-bed naphtha reforming reactors. Acceptable enhancement can be noticed in the performance of the reactors. The production rate of the high octane aromatics and the consumption rate of the paraffins have improved 17% and 72%, respectively. The conversion of the nitrobenzene is acceptable and the effect of the number of the tubes also has been taken into account. However, the performance of the new configuration needs to be tested experimentally over a range of parameters under practical operating conditions. (M.R. Rahimpour).
Chemical Engineering Journal
Hydrogen will become an essential energy source in the near future. In this regard, refineries ca... more Hydrogen will become an essential energy source in the near future. In this regard, refineries can be considered as alternative sources of hydrogen production. In the present study, a tubular membrane reactor with radial-flow patterns of the sweeping gas and the naphtha feed named RF-TMR is proposed as a novel configuration for radial-flow naphtha reformers. Radial-flow reactors are used in refineries as a remedy for high pressure drop through the catalytic packed-bed reactors which disturbs the reactor operation. The cross section area of the tubular membrane reactor is divided into some subsections. The walls of the gaps are coated by a Pd-Ag membrane layer to separate hydrogen from reaction side and enhance the hydrogen and aromatic production rates by 0.33 ton/day and 5.5 ton/day, respectively (compared with the AF-TR). The performance of this novel configuration is investigated and compared with the axial-flow conventional tubular reactor (AF-TR) and axial-flow tubular membrane reactor (AF-TMR). Set of coupled partial differential-algebraic equations are solved by the orthogonal collocation method. Owing to a slight pressure drop in the tube side of RF-TMR, smaller catalysts' particles with a negligible internal mass transfer resistance can be used to increase aromatics and hydrogen yields. This novel approach has the feasibility to be applied in the radial-flow moving bed reformers which are widely installed in refineries by licensors.
Fuel and Energy Abstracts, 2011
Methylcyclohexane dehydrogenation a b s t r a c t
Fuel and Energy Abstracts, 2011
In this novel theoretical study, the dimensionless length of the conventional naphtha reforming r... more In this novel theoretical study, the dimensionless length of the conventional naphtha reforming reactor has been discretized into differential segments and three different cases have been investigated in this regard. In the first case, inlet temperature of each segment has been optimized via differential evolution (DE) method to obtain the optimized temperature profile along the reactors by joining the achieved inlet temperatures for each segment on the figure. Same approach has been applied in the second case in order to achieve optimum hydrogen permeation rate. In the third case, the optimum profiles of temperature and hydrogen removal have been obtained using DE optimization technique using the same approach. The objective of each optimization case is to maximize the hydrogen and aromatics production rate. As it is discussed further, unlike previous studies, application of optimum temperature and hydrogen permeation profiles simultaneously boosts hydrogen and aromatics production rate significantly. 10% and 24% enhancement in hydrogen and aromatics production rates can be achieved by applying the novel theoretical concepts in the conventional naphtha reforming process. (M.R. Rahimpour).
Chemical Engineering Journal, 2011
According to global requirements to DME as an alternative environment friendly fuel and also rega... more According to global requirements to DME as an alternative environment friendly fuel and also regarding the positive effects of employing multifunctional auto-thermal reactors as novel concept in process intensification, direct DME synthesis was coupled with dehydrogenation of cyclohexane in a thermally coupled heat exchanger reactor composed of two separated sides for exothermic and endothermic reactions in our previous study. DME is conventionally produced by a two-stage process which is called the indirect method of DME production. Recently, a new method called direct DME synthesis, have been introduced and gained much more attention due to its economical superiority compared with the indirect method. In this new process, the methanol production and dehydration one occur simultaneously on the hybrid catalysts in only one reactor and consequently the methanol purification unit can be neglected. In the present work, the aforementioned reactor is optimized applying differential evolution (DE) algorithm as an effective and robust optimization method. The objective of this research is to optimize the operating conditions contributing to maximization of the summation of DME and benzene mole fractions in the reactor outlet streams as desired products. The optimal inlet temperatures of exothermic and endothermic sides are determined within their practical range for prevention of catalyst deactivation by sintering. Utilizing the optimization results, the reactor performance would be improved by decreasing of inlet feed flow rates and rising of the production rates of the desired products. This conducted study results in enormous reduction in the operational costs as well as increase of the net profit of the plant. It should be mentioned that an investigation relevant to environmental aspects and commercial viability of the optimized reactor is necessary in order to commercialize the considered process.
Fuel and Energy Abstracts, 2011
Tubular membrane packed bed reactors Radial-flow spherical packed bed reactors Hydrogen productio... more Tubular membrane packed bed reactors Radial-flow spherical packed bed reactors Hydrogen production Aromatic production a b s t r a c t Refineries have been looking for ways of improving the performance of the reformer by enhancing the octane number of the product via increasing the aromatics content. To reach this goal, more improved configurations should be investigated. The aromatics production rate could be enhanced by shifting the reactions to the production side by using hydrogen permeselective membranes. In the present study, we have investigated theoretically the best combination of membrane tubular reactors and spherical radial-flow reactors for the conventional naphtha reforming unit consist of three fixed-bed reactors. Hydrogen permeation through the membrane shifts the reaction to the product side (aromatics and hydrogen) according to the thermodynamic equilibrium. Spherical reactors reduce the pressure drop in the catalytic naphtha reforming units and consequently increase the efficiency. The results show higher aromatics production in the new configurations compared with the membrane tubular and conventional reactors despite using lower membrane surface area. (M.R. Rahimpour).
Fuel and Energy Abstracts, 2011
In this study, a combination of isothermal and adiabatic reactors is modeled for catalytic naphth... more In this study, a combination of isothermal and adiabatic reactors is modeled for catalytic naphtha reforming process. The performance of the proposed configuration has been investigated under an Isothermal-Adiabatic condition. In order to operate under an isothermal condition, reactors are fabricated in a furnace, consisting of multi parallel tubes. The furnace consists of two main parts, a non-reaction zone and a reaction zone.
Fuel and Energy Abstracts, 2011
Thermally coupled reactor Aromatics enhancement Hydrogen production Fluidized bed reactor Nitrobe... more Thermally coupled reactor Aromatics enhancement Hydrogen production Fluidized bed reactor Nitrobenzene hydrogenation a b s t r a c t
Fuel and Energy Abstracts, 2011
a b s t r a c t Refineries have been looking for proper ways of improving reformer performance by... more a b s t r a c t Refineries have been looking for proper ways of improving reformer performance by enhancing the octane number of the product via increasing the aromatics' compounds. To reach this goal, the endothermic catalytic naphtha reforming is coupled with the exothermic hydrogenation of nitrobenzene to aniline in a multifunctional heat exchanger reactor through the process intensification concept. Considering the higher thermal efficiency as well as the smaller size of the coupled reactor, utilizing this reactor is given priority. In this novel configuration, the first and the second reactor of the conventional naphtha reforming process are exchanged with the coupled reactors contain the endothermic naphtha reforming in the shell side and the hydrogenation reaction in the tube side. Both co-current and counter-current modes of flow are examined during the operation considering various studies in literature which show the superiority of co-current flow compared with the counter-current flow. The result of current study is compared with the corresponding results for conventional tubular reactor (CTR). The results show higher aromatic production as much as 18.73% and 16.48% in the co-current and counter-current mode, respectively. Hydrogen molar flow rate increases about 5 kmol/h by using countercurrent flow regime, compared with the CTR. (M.R. Rahimpour).
International Journal of Hydrogen Energy, 2010
In this work a novel radial-flow, spherical packed bed reactor (RF-SPBR) for naphtha reforming in... more In this work a novel radial-flow, spherical packed bed reactor (RF-SPBR) for naphtha reforming in the presence of catalyst deactivation, has been proposed. In this reactor configuration, the space between the two concentric spheres is filled by catalyst. The reactants are flowing through the outer surface to the inner sphere.
International Journal of Hydrogen Energy, 2010
In the present research, differential evolution (DE) method has been used to optimize the operati... more In the present research, differential evolution (DE) method has been used to optimize the operating conditions of a radial flow spherical reactor containing the naphtha reforming reactions. In this reactor configuration, the space between the two concentric spheres is filled by catalyst. The dynamic behavior of the reactor has been taken into account in the optimization process. The achieved mass and energy balance equations in the model are solved by orthogonal collocation method. The goal of this optimization is to maximize the hydrogen and aromatic production which leads to the maximum consumption of the paraffins and naphthenes. In order to reach this end, the inlet temperature of the gas at the entrance of each reactor, the total pressure of the process, as well as the catalyst distribution in each reactor have been optimized using the differential evolution (DE) method. The results of the optimization of the spherical reactor have been compared with the non-optimized spherical reactor. The comparison shows acceptable enhancement in the performance of the reactor.
Fuel and Energy Abstracts, 2010
Spherical packed-bed reactor Catalytic naphtha reforming Dynamic modeling Hydrogen production Aro... more Spherical packed-bed reactor Catalytic naphtha reforming Dynamic modeling Hydrogen production Aromatic production a b s t r a c t Improving the octane number of the aromatics' compounds has always been an important matter in refineries and lots of investigations have been made concerning this issue. In this study, an axial-flow spherical packed-bed reactor (AF-SPBR) is considered for naphtha reforming process in the presence of catalyst deactivation. Model equations are solved by the orthogonal collocation method. The AF-SPBR results are compared with the plant data of a conventional tubular packed-bed reactor (TR). The effects of some important parameters such as pressure and temperature on aromatic and hydrogen production rates and catalyst activity have been investigated. Higher production rates of aromatics can successfully be achieved in this novel reactor. Moreover, results show the capability of flow augmentation in the proposed configuration in comparison with the TR. This study shows the superiority of AF-SPBR configuration to the conventional types. (M.R. Rahimpour).
Uploads
Papers by davood iranshahi