Sharif Digital Repository

An industrial scale propylene production via oxidative dehydrogenation of propane (ODHP) in multi-tubular reactors was modeled. Multi-tubular fixed-bed reactor used for ODHP process, employing 10000 of small diameter tubes immersed in a shell through a proper coolant flows. Herein, a theory-based pseudo-homogeneous model to describe the operation of a fixed bed reactor for the ODHP to correspondence olefin over V2O5/γ-Al2O3 catalyst was presented. Steady state one dimensional model has been developed to identify the operation parameters and to describe the propane and oxygen conversions, gas process and coolant temperatures, as well as other parameters affecting the reactor performance such... 

In this article, a standard 2D Two-Fluid Model (TFM) closed by the kinetic theory of granular flow (KTGF) has been applied to simulate the behavior of tapered-in and tapered-out fluidized bed reactors. In this regard, two types of chemical reactions with gas volume reduction and increase were considered to investigate the effects of initial static bed height on the fractional conversion and bed pressure drop. To validate the CFD model predictions, the results of hydrodynamic simulations concerning bed pressure drop and bed expansion ratio were compared against experimental data reported in the literature and excellent agreement was observed. The obtained simulation results clearly indicate... 

The viscoelasticity effects on the reaction-diffusion rates in a Y-shaped microreactor are studied utilizing the PTT rheological model. The flow is assumed to be fully developed and considered to be created under a combined action of electroosmotic and pressure forces. In general, finite-volume-based numerical simulations are conducted to handle the problem; however, analytical solutions based on the depthwise averaging approach are also obtained for the case for which there is no reaction between the inlet components. The analytical solutions are found to predict accurate results when the width to height ratio is at least 10 and acceptable results for lower aspect ratios. An investigation... 

Auto-thermal reforming (ATR), a combination of exothermic partial oxidation and endothermic steam reforming of methane, is an important process to produce syngas for petrochemical industries. In a commercial ATR unit, tubular fixed bed reactors are typically used. Pressure drop across the tube, high manufacturing costs, and low production capacity are some disadvantages of these reactors. The main propose of this study is to offer an optimized radial flow, spherical packed bed reactor as a promising alternative for overcoming the drawbacks of conventional tubular reactors. In the current research, a one dimensional pseudo-homogeneous model based on mass, energy, and momentum balances is... 

In this research, the activity and selectivity of a platinum-based catalyst for H2 production through aqueous phase reforming (APR) in a fixed-bed reactor (FBR) as well as, a structured catalyst microreactor (MR) were investigated. In this venue, first, an in-house designed MR was fabricated and the catalytic material was deposited on the channel walls of this steel made reactor. After verification of the stability of the coated layer, the prepared reactor was employed to investigate the APR reaction. In this regard, APR of the ethylene glycol and glycerol over Pt/Al2O3 and Pt/CeO2–Al2O3 catalyst were conducted in an MR and FBR. Obtained results demonstrated that employing Pt/CeO2–Al2O3 as a... 

This article presents a simulation study of tapered-in and tapered-out fluidized bed reactors to investigate the influences of apex angle on the fractional conversion and the pressure drop of the fluidized beds in the presence of two types of chemical reaction with gas volume increase and reduction. The 2D behavior of tapered-in and -out fluidized beds was also compared with a columnar one from fractional conversion and bed pressure drop point of views. To validate the simulation results, the numerical predictions for the expansion ratio and the pressure drop of a tapered fluidized bed were compared with experimental data and good agreement was observed. The obtained simulation results... 

This article presents a simulation study of tapered-in and tapered-out fluidized bed reactors to investigate the influences of apex angle on the fractional conversion and the pressure drop of the fluidized beds in the presence of two types of chemical reaction with gas volume increase and reduction. The 2D behavior of tapered-in and -out fluidized beds was also compared with a columnar one from fractional conversion and bed pressure drop point of views. To validate the simulation results, the numerical predictions for the expansion ratio and the pressure drop of a tapered fluidized bed were compared with experimental data and good agreement was observed. The obtained simulation results... 

This article presents a simulation study of tapered-in and tapered-out fluidized bed reactors to investigate the influences of apex angle on the fractional conversion and the pressure drop of the fluidized beds in the presence of two types of chemical reaction with gas volume increase and reduction. The 2D behavior of tapered-in and -out fluidized beds was also compared with a columnar one from fractional conversion and bed pressure drop point of views. To validate the simulation results, the numerical predictions for the expansion ratio and the pressure drop of a tapered fluidized bed were compared with experimental data and good agreement was observed. The obtained simulation results... 

Thanks to a wide range of pore sizes by nano/macro composites of SiOC/Al2O3, such composites can serve as different layers of the structure of Packed Bed Reactor Membranes (PBRM). In the present study, the Polymer-Derived Ceramics method (PDC) has been used to synthesize nano/macro structures. Firstly, the effect of toluene as an extra carbon source on structure and microstructure of SiOC glass-ceramics was evaluated, such that, 4% (Vol) toluene was recognized as the proper amount to facilitate the synthesis of β-SiC at 1300 °C proved by XRD, Raman spectroscopy, and HR-TEM. Moreover, the presence of micro/meso-porosities was assessed by BET and TEM, indicating the capability of SiOC to serve... 

Aqueous-phase reforming (APR) of oxygenated hydrocarbons for hydrogen production presents several advantages as feed molecules might be easily found in a wide range of biomass; there is no need for its vaporization and the process allows thorough exploitation of the environmental benefits of using hydrogen as an energy carrier. In this contribution, catalysts with active phase Ni supported on Al2O3-MgO were synthesized at different loadings (1, 3, 5, 7, and 10 wt%) through the co-precipitation technique and tested for the Glycerol APR reaction. Effects of the Ni loading on physicochemical characteristics of Ni/Al2O3-MgO catalysts were examined. Moreover, catalytic performance was... 

In this study the effects of initial concentration of Fe(II) and Fe(III) ions as well as initial pH on the bioleaching of a low-grade sphalerite ore in a leaching column over a period of 120 days with and without bacteria were investigated. Four different modifications of medium were used as column feed solutions to investigate the effects of initial concentration of Fe(II) and Fe(III) ions on zinc extraction. The experiments were carried out using a bench-scale, column leaching reactor, which was inoculated with mesophilic iron oxidizing bacteria, Acidithiobacillus ferrooxidans, initially isolated from the Sarcheshmeh chalcopyrite concentrate (Kerman, Iran). The effluent solutions were... 

In the present study, due to various advantages of process miniaturization, the integrated design and operation of a mobile power generation system consisting of a microreactor reformer and a proton exchange membrane fuel cell (PEMFC) are investigated. The hydrogen fuel is supplied through autothermal steam-reforming of methanol in a microreactor leading to a safer, as well as more efficient, and economical operation. A high-temperature polymer membrane fuel cell with external accessories is applied for power generation. Then, simulation-optimization programming is applied for simultaneously optimizing the process design and operation at the same level. The result shows that the implemented... 

The aim of this study is to assess the influence of oxygen-to-steam ratio, wall boundary conditions, coal feeding rate, and static bed height on the concentrations, heating values, and efficiencies of the product gas in a tapered fluidized bed reactor. Results show that lower and higher heating values slightly vary with increasing the oxygen-to-steam ratio in the range of 0.25–0.35. It is found that cold gas efficiency and carbon conversion efficiency goes up with increased ratio of oxygen to steam; however, both efficiencies decline as a result of increasing the coal feeding rate. As static bed height rises, lower and higher heating values diminish for tapered angle of 5°. For tapered angle... 

A mathematical model has been developed to simulate heterogeneous reactions with a complex set of physicochemical and thermal phenomena in a packed bed. These include the chemical reaction itself, the transport of gaseous species in the pores, the generation or consumption of heat by the reactions, and the transport of heat in the porous domain. Solution of complicated sets of governing equations is based upon the concept of a finite volume fully implicit approach. The model has then been applied to analyze the reduction of a hematite pellet in a moving packed bed reactor. © 2005 Elsevier Ltd  

In this study, mathematical modelling of oxidative coupling of methane (OCM) to C 2 hydrocarbons (C 2H 6 and C 2H 4) over La 2O 3/CaO catalyst in a fixed-bed reactor operated under isothermal and non-isothermal conditions was investigated using the MATLAB program. In this process, methane and acetylene were the inputted feed and ethane, ethylene, propylene, propane, i-butane and n-butane were the output products. The amount of methane conversion obtained was 12.7% for the former feed however; if pure methane was inputted this conversion rose to 13.8%. Furthermore, the plasma process would enhance the conversion, selectivity towards desired product and process yield. A comparison between the... 

In this investigation, a reactor model for prediction of the deactivation behavior of MTO's porous catalyst in a fixed bed reactor is developed. Effect of coking on molecular transport in the porous structure of SAPO-34 has been simulated using the percolation theory. Thermal effects of the reaction were considered in the model and the temperature profile of the gas stream in the reactor was predicted. The predicted loss in catalyst activity with time-on-stream was in very good agreement with the experimental data. The resulting coke deposition and gas temperature profiles along the length of reactor suggested a reaction front moving toward the outlet of the fixed bed reactor at the... 

In the present study, a procedure was developed to determine the optimum reaction rate constants in generalized Arrhenius form and optimized through the Nelder-Mead method. For this purpose, a comprehensive mathematical model of a fixed bed reactor for dehydrogenation of heavy paraffins over Pt-Sn/Al 2O 3 catalyst was developed. Utilizing appropriate kinetic rate expressions for the main dehydrogenation reaction as well as side reactions and catalyst deactivation, a detailed model for the radial flow reactor was obtained. The reactor model composed of a set of partial differential equations (PDE), ordinary differential equations (ODE) as well as algebraic equations all of which were solved... 

Two-dimensional mesoporous carbon nitride and its highly efficient nanorod framework were prepared via hard-templating method. The obtained materials were fully characterized. The results showed that the samples structural ordering and morphology were similar to those of the parent silica templates; they had large pore volumes as well as high surface area structures. Carbon nitride carbocatalysts were used for H2S selective oxidation. The catalytic tests were carried out at 190, 210 and 230 °C in a fixed bed reactor. The obtained selectivity values for mesoporous carbon nitride rod and mesoporous carbon nitride toward elemental sulfur at 190 °C were 88.8% and 83%, respectively. Both samples...