Differential evolution (DE) strategy for optimization of hydrogen production,cyclohexane dehydrogenation and methanol synthesis in a hydrogen-permselective membrane thermally coupled reactor

In this work a novel reactor configuration has been proposed for simultaneous methanol synthesis, cyclohexane dehydrogenation and hydrogen production. This reactor configuration is a membrane thermally coupled reactor which is composed of three sides for methanol synthesis, cyclohexane dehydrogenation and hydrogen production. Methanol synthesis takes place in the exothermic side that supplies the necessary heat for the endothermic dehydrogenation of cyclohexane reaction. Selective permeation of hydrogen through the Pd/Ag membrane is achieved by co-current flow of sweep gas through the permeation side. A steady-state heterogeneous model of the two fixed beds predicts the performance of this configuration. A theoretical investigation has been performed in order to evaluate the optimal operating conditions and enhancement of methanol, benzene and hydrogen production in a membrane thermally coupled reactor. The co-current mode is investigated and the optimization results are compared with corresponding predictions for a conventional (industrial) methanol fixed bed reactor operated at the same feed conditions. The differential evolution (DE), an exceptionally simple evolution strategy, is applied to optimize this reactor considering the mole fractions of methanol, benzene and hydrogen in permeation side as the main objectives. The simulation results have been shown that there are optimum values of initial molar flow rate of exothermic and endothermic stream, inlet temperature of exothermic, endothermic and permeation sides, and inlet pressure of exothermic side to maximize the objective function. The simulation results show that the methanol mole fraction in output of reactor is increased by 16.3% and hydrogen recovery in permeation side is 2.71 yields. The results suggest that optimal coupling of these reactions could be feasible and beneficial. Experimental proof-of-concept is needed to establish the validity and safe operation of the novel reactor.     

Optimal conditions for hydrogen production from coupling of dimethyl ether and benzene synthesis

Coupling energy intensive endothermic reaction systems with suitable exothermic reactions followed by hydrogen permeation through the Pd/Ag membrane improves the thermal efficiency of processes, achieving the autothermality within the reactor, reduces the size of reactors, produces the pure hydrogen, and achieving a multiple reactants multiple products configuration. This paper focuses on optimization of hydrogen, dimethyl ether (DME) and benzene production in a membrane thermally coupled reactor. A steady-state heterogeneous mathematical model that is composed of three sides is developed to predict the performance of this novel configuration reactor. The catalytic methanol dehydration to DME takes place in the exothermic side that supplies the necessary heat for the catalytic dehydrogenation of cyclohexane to benzene reaction in the endothermic side. Selective permeation of hydrogen through the Pd/Ag membrane is achieved by co-current flow of sweep gas through the permeation side. This novel configuration can decrease the temperature of methanol dehydration reaction in the second half of the reactor and shift the thermodynamic equilibrium. The differential evolution (DE), an exceptionally simple evolution strategy, is applied to optimize membrane thermally recuperative coupled reactor considering the summation of methanol and cyclohexane conversions and dimensionless hydrogen recovery yield as the main objectives. The simulation results have been shown that there are optimum values of initial molar flow rate of exothermic and endothermic sides and inlet temperature of exothermic, endothermic and permeation sides to maximize the objective function. The optimization method has enhanced the methanol conversion by 2.76%. The optimization results are compared with corresponding predictions for a conventional (industrial) methanol dehydration adiabatic reactor operated at the same feed conditions. The results suggest that coupling of these reactions could be feasible and beneficial. An experimental proof-of-concept is needed to establish the validity and safe operation of the novel reactor.     

Mathematical simulation and optimization of methanol dehydration and cyclohexane dehydrogenation in a thermally coupled dual-membrane reactor

Thermally coupling of endothermic and exothermic reactions in a membrane reactor improves thermal efficiency and production rate in the processes, reduces the size of reactors and decreases purification cost. This paper focuses on modeling and optimization of a thermally coupled dual-membrane reactor for simultaneous production of hydrogen, dimethyl ether (DME) and benzene. A steady state heterogeneous mathematical model is developed to predict the performance of this novel configuration. The catalytic methanol dehydration reaction takes place in the exothermic side that supplies the necessary heat for the catalytic dehydrogenation of cyclohexane to benzene in the endothermic side. Selective permeation of hydrogen and water vapor through the Pd/Ag and composite membranes are achieved by co-current flow of sweep gas through the membrane wall. The differential evolution method is applied to optimize the thermally coupled dual-membrane reactor considering the summation of DME and benzene mole fractions from reaction sides and hydrogen mole fraction in the permeation side as the main objectives. The optimization results are compared with corresponding predictions for an industrial methanol dehydration adiabatic reactor operated at the same feed conditions. Methanol conversion enhances about 5.5% in the optimized thermally coupled dual-membrane reactor relative to the conventional DME reactor. The results suggest that coupling of these reactions in the proposed configuration could be feasible and beneficial.     

Production of ultrapure hydrogen via utilizing fluidization concept from coupling of methanol and benzene synthesis in a hydrogen-permselective membrane reactor

In this work, a novel fluidized-bed thermally coupled membrane reactor has been proposed for simultaneous hydrogen, methanol and benzene production. Methanol synthesis is carried out in exothermic side which is a fluidized-bed reactor and supplies the necessary heat for the endothermic side. Dehydrogenation of cyclohexane is carried out in endothermic side with hydrogen-permselective Pd/Ag membrane wall. Selective permeation of hydrogen through the membrane in endothermic side is achieved by co-current flow of sweep gas through the permeation side. A steady-state fixed-bed heterogeneous model for dehydrogenation reactor and two-phase theory in bubbling regime of fluidization for methanol synthesis reactor is used to model and simulate the integrated proposed system. This reactor configuration solves some observed drawbacks of new thermally coupled membrane reactor such as internal mass transfer limitations, pressure drop, radial gradient of concentration and temperature in both sides. The proposed model has been used to compare the performance of a fluidized-bed thermally coupled membrane reactor (FTCMR) with thermally coupled membrane reactor (TCMR) and conventional methanol reactor (CR) at identical process conditions. This comparison demonstrates that fluidizing the catalytic bed in the exothermic side of reactor caused a favorable temperature profile along the FTCMR. Furthermore, the simulation results represent 5.6% enhancement in the yield of hydrogen recovery in comparison with TCMR.     

Enhancement of simultaneous hydrogen production and methanol synthesis in thermally coupled double-membrane reactor

Coupling the methanol synthesis with the dehydrogenation of cyclohexane to benzene in a co-current flow, catalytic fixed-bed double-membrane reactor configuration in order to simultaneous pure hydrogen and methanol production was considered theoretically. The thermally coupled double-membrane reactor (TCDMR) consists of two Pd/Ag membranes, one for separation of pure hydrogen from endothermic side and another one for permeation of hydrogen from feed synthesis gas side (inner tube) into exothermic side. A steady-state heterogeneous model is developed to analyze the operation of the coupled methanol synthesis. The proposed model has been used to compare the performance of a TCDMR with conventional reactor (CR) and thermally coupled membrane reactor (TCMR) at identical process conditions. This comparison shows that TCDMR in addition to possessing advantages of a TCMR has a more favorable profile of temperature and increased productivity compared with other reactors. The influence of some operating variables is investigated on hydrogen and methanol yields. The results suggest that utilizing of this reactor could be feasible and beneficial. Experimental proof of concept is needed to establish the validity and safe operation of the recuperative reactor.     

Optimization of methanol synthesis and cyclohexane dehydrogenation in a thermally coupled reactor using differential evolution (DE) method

This paper presents a study on optimization of a methanol synthesis and cyclohexane dehydrogenation in a thermally coupled reactor. A theoretical investigation has been performed in order to evaluate the optimal operating conditions and enhancement of methanol and benzene production in a thermally coupled reactor. Coupling energy intensive endothermic reaction systems with suitable exothermic reactions improves the thermal efficiency of processes and reduces the size of the reactors. In this work, the catalytic methanol synthesis is coupled with the catalytic dehydrogenation of cyclohexane to benzene in a heat exchanger reactor formed of two fixed beds separated by a wall, where heat is transferred across the surface of tube. A steady-state heterogeneous model of the two fixed beds predicts the performance of this novel configuration. The co-current mode is investigated and the optimization results are compared with corresponding predictions for a conventional (industrial) methanol fixed bed reactor operated at the same feed conditions. The differential evolution (DE), an exceptionally simple evolution strategy, is applied to optimize methanol and benzene synthesis coupled reactor considering methanol and benzene mole fractions as the main objectives. The simulation results have been shown that there are optimum values of initial molar flow rate of endothermic stream and inlet temperature of exothermic and endothermic sides to maximize the objective function. The optimization method has enhanced the methanol mole fraction by 3.67%. The results suggest that optimal coupling of these reactions could be feasible and beneficial. Experimental proof-of-concept is needed to establish the validity and safe operation of the novel reactor.     

Production of hydrogen and methanol enhancement via a novel optimized thermally coupled two‐membrane reactor

This study focuses on optimum operating conditions for thermally coupled two‐membrane reactor (TCTMR) to maximize ultrapure hydrogen and methanol production as alternative environmentally friendly fuels. Hydrogen is used in chemical and petrochemical industries especially applicable in fuel cell technologies, with zero CO₂ emission. In the proposed configuration, methanol synthesis is carried out in the exothermic side by hydroxy sodalite membrane and supplies the necessary heat for the endothermic side. Dehydrogenation of cyclohexane is carried out in the endothermic side with hydrogen‐permselective Pd/Ag membrane wall. A one‐dimensional, steady‐state heterogeneous model and the differential evolution method, as a strong and powerful optimization method, are applied to simulate and optimize the proposed reactor configuration. The simulation results have been shown that there are optimal values of the initial molar flow rate of endothermic, outer and the inner permeation stream, inlet temperature of exothermic, endothermic, outer and inner permeation sides and inlet pressure of inner permeation side to maximize the objective function. The optimization results show 5.87 and 10.51% increase in the methanol production in optimized TCTMR compared with TCTMR and a conventional reactor, respectively. Moreover, this novel configuration with optimal conditions raises the hydrogen production rate about 1.1847 ton/day. Copyright © 2012 John Wiley & Sons, Ltd.     

The effect of flow type patterns in a novel thermally coupled reactor for simultaneous direct dimethyl ether (DME) and hydrogen production

Dimethyl ether (DME) has gained wide interest in chemical industry regarding its use as a multi-source, multi-purpose fuel either for diesel engines or as a clean alternative for liquefied petroleum gas (LPG). The direct synthesis of DME from syngas would be more economical and beneficial in comparison to the indirect process via methanol dehydration. In this study, one type of the multifunctional auto-thermal reactors (the recuperative one) is selected in which the direct synthesis of dimethyl ether (DME) is coupled with the catalytic dehydrogenation of cyclohexane to benzene in a two fixed bed reactor separated by a solid wall, where heat is transferred across the surface of tube. Steady-state, heterogeneous, one-dimensional model has been used to describe the performance of this novel configuration. Both co-current and counter-current operating modes are investigated and the simulation results are compared with the available data of a pipe-shell fixed bed reactor for direct DME synthesis which operates at the same feed conditions. In addition, the influence of the molar flow rate of exothermic and endothermic stream on the reactor performance is also investigated. The results suggest that coupling of these reactions could be feasible and beneficial and the co-current mode has got better performance in DME and hydrogen production. In order to establish the validity and safety handling of the new concept, an experimental proof is required.     

Hydrogen/methanol production in a novel multifunctional reactor with in situ adsorption: modeling and optimization

This work proposes a novel multifunctional reactor for simultaneous production of hydrogen and methanol in which zeolite 4A is considered as water adsorbent. For this purpose, in the exothermic side of the proposed configuration, a gas‐flowing solid‐fixed bed reactor (GFSFBR) is used. The remarkable advantage of GFSFBR over the conventional sorption‐enhanced reaction process is the continuous adsorbent regeneration in this novel reactor. MR takes the advantages of adsorption and couple technique simultaneously. The new configuration is designed as a double pipe reactor where highly exothermic methanol synthesis reactions in the exothermic side are coupled with dehydrogenation of cyclohexane. A one‐dimensional, steady‐state heterogeneous model is used to simulate the proposed reactor configuration. Simulation result demonstrates that selective adsorption of water in the exothermic side leads to 22.5%, 9.85% and 7.1% enhancement in methanol, benzene and hydrogen production, respectively, compared with the zero solid mass flux condition. Subsequently, the aforementioned reactor is optimized using differential evolution algorithm to maximize the hydrogen mole fraction in the endothermic side as well as the methanol yield in the exothermic side. Copyright © 2013 John Wiley & Sons, Ltd.     

Optimization of hydrogen production via coupling of the Fischer–Tropsch synthesis reaction and dehydrogenation of cyclohexane in GTL technology

In this study, a thermally-coupled reactor containing the Fischer–Tropsch synthesis reaction in the exothermic side and dehydrogenation of cyclohexane in the endothermic side has been modified using a hydrogen perm-selective membrane as the shell of the reactor to separate the produced hydrogen from the dehydrogenation process. Permeated hydrogen enters another section called permeation side to be collected by Argon, known as the sweep gas. This three-sided reactor has been optimized using differential evolution (DE) method to predict the conditions at which the reactants’ conversion and also the hydrogen recovery yield would be maximized. Minimizing the CO₂ and CH₄ yield in the reactor’s outlet as undesired products is also considered in the optimization process. To reach this goal, optimal initial molar flow rate and inlet temperature of three sides as well as pressure of the exothermic side have been calculated. The obtained results have been compared with the conventional reactor data of the Research Institute of Petroleum Industry (RIPI), the membrane dual – type reactor suggested for Fischer–Tropsch synthesis, and the membrane coupled reactor presented for methanol synthesis. The comparison shows acceptable enhancement in the reactor’s performance and that the production of hydrogen as a valuable byproduct should also be considered.     

Simultaneous hydrogen production and utilization via coupling of Fischer-Tropsch synthesis and decalin dehydrogenation reactions in GTL technology

A thermally coupled membrane dual-type reactor (TCMDR) has been proposed for simultaneous hydrogen production and utilization in gas-to-liquid technology (GTL). Decalin dehydrogenation reaction is coupled with Fischer-Tropsch synthesis (FTS) reaction to improve the heat transfer between endothermic and exothermic sides. Furthermore, Pd-Ag and Hydroxy Sodalite membrane layers are assisted in TCMDR to improve the mass transfer between exothermic/endothermic side and permeation side. Some of the produced hydrogen via decalin dehydrogenation reaction is utilized in FTS reaction and the other is extracted and stored. The modeling results show 95% hydrogen production and 5% hydrogen utilization in FTS reactions in the exothermic reaction side of TCMDR configuration. The performance of TCMDR is compared with the one of conventional reactor (CR) and fluidized-bed membrane dual-type reactor (FMDR). Moreover, the gasoline yield in TCMDR increases about 17% and 29% in comparison with the one in FMDR and CR, respectively. The enhancement in gasoline and hydrogen yields demonstrates the superiority of TCMDR to the previous reactors.     

Simultaneous utilization of two different membranes for intensification of ultrapure hydrogen production from recuperative coupling autothermal multitubular reactor

The potential of simultaneous hydrogen production and in situ water removal in a thermally coupled multitubular two-membrane reactor (TCTMR) were studied numerically. Methanol synthesis is carried out in exothermic side with H-SOD membrane and supplies the necessary heat for the endothermic side. Dehydrogenation of cyclohexane is carried out in endothermic side with hydrogen-permselective Pd/Ag membrane wall. Therefore, the proposed reactor consists of two membranes, one for separation of pure hydrogen from endothermic side and another one for separation of water from exothermic side. The motivation for in situ H₂O removal during methanol synthesis by using H-SOD membranes is to displace the water-gas shift equilibrium to enhance conversion of CO₂ to improve methanol productivity. A steady-state heterogeneous model is developed to analyze the operation of the coupled methanol synthesis. The proposed model has been used to compare the performance of a TCTMR with conventional reactor (CR) and thermally coupled membrane reactor (TCMR) at identical process conditions. This comparison shows that TCTMR in addition to possessing advantages of a TCMR has a more favorable profile of temperature and increased productivity compared with other reactors. Furthermore, lower water production rate in TCTMR reduces catalyst re-crystallization.     

Hydrogen looping approach in optimized methanol thermally coupled membrane reactor

In this study, cyclohexane and hydrogen loop approach is proposed in optimized thermally coupled dual reactors in methanol production via Differential Evolution (DE) method. This new generation of thermally coupled membrane reactors uses simultaneously the advantages of hydrogen carrier characteristic and multifunctional reactors. This configuration is named thermally coupled dual methanol reactor (TCDMR). In the first reactor, cyclohexane dehydrogenation reaction is coupled with methanol production reactions. Cyclohexane is produced in the second reactor due to carrying all produced hydrogen from the first reactor to the second reactor for benzene hydrogenation reaction. The operating conditions of TCDMR are optimized via DE method and six decision variables are considered to investigate its performance. Since cyclohexane is produced continuously in the second reactor and enters the first reactor as the endothermic feed, the external cyclohexane injection rate is minimized, too. A comparison is made between the optimized TCDMR (OTCDMR), TCDMR and Thermally coupled methanol reactor (TCMR) and conventional methanol reactor (CMR). The modeling results demonstrate the superiority of OTCDMR to all previously proposed configurations. A continuous system is achieved and slight amount of exterior cyclohexane injection rate (3.6 mol h⁻¹) is required in this configuration. Furthermore, the hydrogen storage problem is solved by this configuration owing to simultaneous hydrogen production and utilization. In addition, produced benzene in OTCDMR is about 10% of the one in TCMR which can be appealing from the environmental viewpoint.     

A novel integrated thermally coupled configuration for methane-steam reforming and hydrogenation of nitrobenzene to aniline

In this work, a novel thermally coupled reactor containing the steam reforming process in the endothermic side and the hydrogenation of nitrobenzene to aniline in the exothermic side has been investigated. In this novel configuration, the conventional steam reforming process has been substituted by the recuperative coupled reactors which contain the steam reforming reactions in the tube side, and the hydrogenation reaction in the shell side. The co-current mode is investigated and the simulation results are compared with corresponding predictions for an industrial fixed-bed steam reformer reactor operated at the same feed conditions. The results show that although synthesis gas productivity is the same as conventional steam reformer reactor, but aniline is also produced as an additional valuable product. Also it does not need to burn at the furnace of steam reformer. The performance of the reactor is numerically investigated for different inlet temperature and molar flow rate of exothermic side. The reactor performance is analyzed based on methane conversion, hydrogen yield and nitrobenzene conversion. The results show that exothermic feed temperature of 1270 K can produce synthesis gas with 26% methane conversion (the same as conventional) and nitrobenzene conversion in the outlet of the reactor is improved to 100%. This new configuration eliminates huge fired furnace with high energy consumption in steam reforming process.     

Simultaneous production of ultrapure hydrogen and gasoline in a novel thermally coupled double‐membrane reactor

In this study, simultaneous production of ultrapure hydrogen and gasoline via a novel catalytic fixed‐bed double‐membrane reactor with co‐current flow was investigated, mathematically. The thermally coupled double‐membrane reactor (TCDMR) consists of two Pd/Ag membranes, one for separation of pure hydrogen from endothermic side and another one for permeation of hydrogen from endothermic into exothermic side. Ammonia decomposition reaction is coupled with the Fischer–Tropsch Synthesis (FTS) reaction to improve the heat transfer between endothermic and exothermic sides. Some of the produced hydrogen via ammonia decomposition reaction is utilized in FTS reaction, and the other is extracted and stored. A steady‐state heterogeneous model of the two fixed beds predicts the performance of this novel configuration. The achieved results of this simulation have been compared with the results of the conventional fixed‐bed reactor (CR) at identical process conditions. The simulation results show 67.34% hydrogen production in the permeation side and 32.66% hydrogen utilization in the exothermic side for compensates of hydrogen lack in the FTS reaction through the TCDMR configuration. Moreover, the gasoline yield in TCDMR increases about 18.42% because of a favorable profile of temperature along the TCDMR in comparison with the one in CR. Therefore, this approach utilizes and produces large amounts of pure hydrogen and decreases environmental impacts owing to ammonia emission. Copyright © 2011 John Wiley & Sons, Ltd.     

Direct dimethyl ether (DME) synthesis through a thermally coupled heat exchanger reactor

Compared to some of the alternative fuel candidates such as methane, methanol and Fischer–Tropsch fuels, dimethyl ether (DME) seems to be a superior candidate for high-quality diesel fuel in near future. The direct synthesis of DME from syngas would be more economical and beneficial in comparison with the indirect process via methanol synthesis. Multifunctional auto-thermal reactors are novel concepts in process intensification. A promising field of applications for these concepts could be the coupling of endothermic and exothermic reactions in heat exchanger reactors. Consequently, in this study, a double integrated reactor for DME synthesis (by direct synthesis from syngas) and hydrogen production (by the cyclohexane dehydrogenation) is modelled based on the heat exchanger reactors concept and a steady-state heterogeneous one-dimensional mathematical model is developed. The corresponding results are compared with the available data for a pipe-shell fixed bed reactor for direct DME synthesis which is operating at the same feed conditions. In this novel configuration, DME production increases about 600 Ton/year. Also, the effects of some operational parameters such as feed flow rates and the inlet temperatures of exothermic and endothermic sections on reactor behaviour are investigated. The performance of the reactor needs to be proven experimentally and tested over a range of parameters under practical operating conditions.     

A comparison of hydrogen and methanol production in a thermally coupled membrane reactor for co‐current and counter‐current flows

This work considers three concentric tube reactors to prepare pure hydrogen, especially applicable in fuel cell technologies, with zero CO₂ emission. Hydrogen and methanol production rates are compared in a thermally coupled exothermic and endothermic reactor for co‐current and counter‐current modes. Synthesis of methanol is coupled with dehydrogenation of cyclohexane as a high content hydrogen carrier (7.1 wt%). The efficient coupling of exothermic and endothermic reactions increases the profitability of operation of the reactor, reduces the size of reactor and decreases the operational and capital costs. By inserting a hydrogen‐perm selective membrane into the reactor configuration, hydrogen can permeate selectively into the membrane, and hence, the third tube receives hydrogen. The simulation results are compared with the corresponded results for an industrial methanol fixed‐bed reactor, which operates under the same feed conditions. The influence of some operating variables is investigated on methanol and hydrogen yields during the performance of reactor. The results show higher methanol conversion, as the same as conventional reactor, and hydrogen for co‐current flow. Copyright © 2010 John Wiley & Sons, Ltd.     

A comparison of two different flow types on performance of a thermally coupled recuperative reactor containing naphtha reforming process and hydrogenation of nitrobenzene

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 counter-current flow regime, compared with the CTR.     

Comparison of two different flow types on CO removal along a two-stage hydrogen permselective membrane reactor for methanol synthesis

Carbon monoxide (CO) is a gaseous pollutant with adverse effects on human health and the environment. Industrial chemical processes contribute significantly to CO accumulation in the atmosphere. One of the most important processes for controlling carbon monoxide emissions is the conversion of CO to methanol by catalytic hydrogenation. In this study, the effects of two different flow types on the rate of CO removal along a two-stage hydrogen permselective membrane reactor have been investigated. In the first configuration, fresh synthesis gas flows in the tube side of the membrane reactor co-currently with reacting material in the shell side, so that more hydrogen is provided in the first sections of the reactor. In the second configuration, fresh synthesis gas flows in the tube side of the membrane reactor counter-currently with reacting material in the shell side, so that more hydrogen is provided in the last sections of the reactor. For this membrane system, a one-dimensional dynamic plug flow model in the presence of catalyst deactivation was developed. Comparison between co-current and counter-current configurations shows that the reactor operates with higher conversion of CO and hydrogen permeation rate in the counter-current mode whereas; longer catalyst life is achieved in the co-current configuration. Enhancement of CO removal in the counter-current mode versus the co-current configuration results in an ultimate reduction in CO emissions into the atmosphere.     

Comparison of co-current and counter-current flow in a bifunctional reactor containing ammonia synthesis and 2-butanol dehydrogenation to MEK

In this study, a multi-tubular thermally coupled packed bed reactor in which simultaneous production of ammonia and methyl ethyl ketone (MEK) takes place is simulated. The simulation results are presented in two co-current and counter-current flow modes. Based on this new configuration, the released heat from the ammonia synthesis reaction as an extremely exothermic reaction in the inner tube is employed to supply the required heat for the endothermic 2-butanol dehydrogenation reaction in the outer tube. On the other hand, MEK and hydrogen are produced by the dehydrogenation reaction of 2-butanol in the endothermic side, and the produced hydrogen is used to supply a part of the ammonia synthesis feed in the exothermic side. Thus, 30.72% and 31.88% of the required hydrogen for the ammonia synthesis are provided by the dehydrogenation reaction in the co-current and counter-current configurations, respectively. Also, according to the thermal coupling, the required cooler and furnace for the ammonia synthesis and 2-butanol dehydrogenation conventional plants are eliminated, respectively. As a result, operational costs, energy consumption and furnace emissions are considerably decreased. Finally, a sensitivity analysis and optimization are applied to study the effect of the main process parameters variation on the system performance and obtain the minimum hydrogen make-up flow rate, respectively.