Commercial-scale Reactor Research Articles

Plant-wide modeling and techno-economic analysis of a direct non-oxidative methane dehydroaromatization process via conventional and microwave-assisted catalysis

Direct non-oxidative methane dehydroaromatization (DHA) process via conventional and microwave (MW)-assisted thermo-catalytic catalysis is studied. Rate models for methane DHA reactions, including the effect of catalyst deactivation, are developed by using the in-house experimental data. Model results for gas concentration profile and catalyst deactivation are in good agreement with the experimental data. This rate model is then used for the development of dynamic multi-scale, multi-physics commercial-scale reactor models. Total number of fixed bed reactors desired for a cyclic steady state process is estimated. Plant-wide models are then developed for conventional and MW-assisted processes for producing products of desired specifications. Techno-economic analysis of the methane DHA process is undertaken. Economics of these methane DHA processes are compared with the typical multi-step natural gas to aromatics production process via methanol synthesis. Sensitivity of internal rate of return (IRR) and net present value (NPV) to various economic and process parameters such as plant scale, desired rate of return, reactor cost, feedstock and utility cost, catalyst variable cost, and MW reactor cost is studied. Electric equivalent efficiency of the conventional methane DHA process is found to be 69.2 % and 67.3 % at 750 °C and 800 °C, respectively, while the MW-assisted methane DHA process has the electric equivalent efficiency of 48.9 % at 800 °C. IRRs of the conventional methane DHA process at 750 °C and 800 °C, and MW-assisted process are 15.2 %, 17.5 %, and 18.8 %, respectively for a methane feed flowrate of 19,782 kg/h, while the IRR of the multi-step natural gas to aromatics production process is estimated to be 0 % for the same plant scale. Impact of change in the methane price, electricity price, and catalyst cost is found to be considerable on the process economics, while the cost of the MW reactor is found to have negligible impact.

Structured ZoneFlow™-Bayonet steam reforming reactor for reduced firing and steam export: Pressure drop and heat transfer modelling and evaluation of the reactor performance

The ZoneFlow™ reactor is an annular structured reactor that offers lower pressure drop and significantly better heat transfer than standard pellets used in Steam Methane Reforming. The annular ZoneFlow™ reactor is particularly suited for use in a bayonet configuration. The produced syngas then returns via the central tube, the so-called bayonet, allowing counter-current heat exchange between the return gas and the gas reacting in the ZoneFlow™ reactor. As such, the heat supplied by the furnace can be maximally used for the reactions and steam export can be reduced. To intensify the heat transfer between the gas in the bayonet and in the annulus, an insert is installed inside the bayonet, forming a second annulus that forces the gas to flow close to the bayonet wall at high velocity. In the present work, the pressure drop and heat transfer resulting from various bayonet configurations are experimentally measured at commercial scale reactor dimensions and air flow rates equivalent to commercial conditions. Correlations for the friction factors and the heat transfer coefficients are derived from the data. The correlations are then used to simulate a commercial scale ZoneFlow™-bayonet reactor and optimize the design.

Modeling and simulation of a multi-bed industrial reactor for renewable diesel hydroprocessing

The complexity of designing and optimizing vegetable oil hydrotreating reactors lies in describing multiple phenomena, including heat and mass transfer, hydrogen consumption, pressure drop, and a complicated network of highly exothermic reactions. This study intends to analyze the behavior of a vegetable oil hydroprocessing unit in a commercial environment via modeling and simulation techniques. In order to describe the three-phase (gas-liquid-solid) system in a detailed manner, a commercial-scale reactor model having multiple catalyst beds and inter-bed quench gas injections was constructed accounting for the heat and mass transfer between phases, the dynamic response of the system, the variation in gas phase velocity, and intraparticle effects. Based on dynamic reactor simulations, quench gas injection strategies were proposed to control the reactor temperature profile and yield of the desired products. Simulation results showed that the selection of a feed inlet temperature plays a major role in reactor overheating and quench injections must start as soon as the reactant stream reaches the inter-bed quench zone to stabilize reactor temperature more rapidly during start-up. In addition, the lengths of the catalyst beds need to be adjusted such that the heat released by chemical reactions is properly distributed along the reactor. The results overall provide useful information for the design and optimization of commercial-scale catalyst bed configurations for hydrotreating renewable feedstock. In particular, it is highlighted that by means of an appropriate gas quenching configuration, reactor temperature can be adequately controlled, allowing higher yields of green diesel.

Application of kinetics and computational fluid dynamics in pinene isomerization

A reliable kinetic model to describe the effects of various factors on the reaction rate and selectivity of pinene isomerization is developed. Furthermore, computational fluid dynamics (CFD) is applied to simulate the solid–liquid dispersion in reactor. The catalyst TiM is obtained by improving the composition and structure of hydrated titanium dioxide. The kinetic equation of pinene isomerization is deduced based on reaction mechanism and catalyst deactivation model. The kinetic equation of pinene isomerization reaction is fitted, and the results show that the fitted equation is correlated with the experimental data. The rate and selectivity of pinene isomerization reaction are affected by the amount of catalyst, deactivation of catalyst, structure of catalyst, reaction temperature and water content of catalyst. The solid–liquid distribution of the reactor is calculated by computational fluid dynamics numerical simulation, and the solid–liquid dispersion in commercial scale reactor is more uniform than that in lab-scale reactor. • Establish a more complete kinetic model by introducing deactivation model • The kinetic model correlates well with experimental data. • The lab-scale reactor and commercial scale reactor are investigated by CFD numerical simulation. • The factors affecting the rate and selectivity of the pinene isomerization reaction are systematically studied.

Assembly design of a fluoride salt-cooled high temperature commercial-scale reactor: Neutronics evaluation and parametric analysis

In this study, a novel assembly design is proposed for a fluoride salt-cooled high-temperature commercial-scale (FHCR) reactor. It employs tristructural isotropic (TRISO) fuel particles nestled within removable cylindrical beryllium carbide (Be2C) moderator blocks, which are further contained within prismatic graphite blocks. As the name implies, the FHCR is a preconception of a 3400 MW(t) commercial power reactor that uses FLiBe (LiF-BeF2) as the primary coolant of choice. This paper uses the SERPENT 2 code to conduct a parametric neutronics study on the two-dimensional lattice assembly design of the FHCR. The calculations examine the effects of various fuel enrichment levels, TRISO particle packing fractions, fuel compacts’ pitch sizes, and moderating materials on the cycle length, while also determining the neutron spectrum and various nuclide inventories. Finally, a preliminary core is modeled based on the study conducted on the assembly design. Based on the negative values of the fuel temperature coefficients (FTC), moderator temperature coefficients (MTC), and coolant temperature coefficients (CTC) obtained, the design is determined to be safe. This new assembly design is also able to achieve keff>1 for approximately 3.55 years, translating to a burn-up of 160.6 MWd/KgU.

Effect of Non-Ideal Mixing on Heat Transfer of non-Newtonian Liquids in a Mechanically Agitated Vessel

Abstract Effect of non-ideal mixing on heat transfer phenomena is studied in an anchor agitated vessel processed with viscous Newtonian and non-Newtonian fluids. Influence of critical variables such as rotational speed and properties of the fluid on heat transfer coefficient and heat transfer area has been investigated. Based on the flow pattern generated by an anchor agitator, a multi parameter model for quantifying the extent of non-ideality is developed and the parameters of the model, fraction of well mixed zone and the exchange flow rate are evaluated on the basis of tracer response data. Heat transfer experiments are also conducted under unsteady state conditions using same agitated vessel under similar operating conditions using Castor oil, Castor oil methyl esters (CME) and carboxy methyl cellulose (CMC 0.5 %, 1 %), soap solution as process fluids. Based on the results obtained from this analysis, a commercial scale reactor of a capacity of 20 Kl for saponification of hydrogenated castor oil has been designed using different scaleup rules. Power per unit volume found to give desirable results as it gives acceptable values for heat transfer coefficient and power consumption. Equal power per unit volume gives good mixing and high heat transfer coefficient with slightly higher power consumption and the error involved in heat transfer area calculation is small giving optimum cost of the experimental unit.

Development of Hydrodynamic and Heat Transfer Profiles for Fischer–Tropsch Synthesis in a Fixed Bed Reactor of Different Scales

Comprehensive hydrodynamic and heat transfer study of Fischer–Tropsch synthesis (FTS) on a home-based cobalt catalyst, with the presence of water–gas shift (WGS), is conducted with a fixed bed reactor. Two different diameters have been used for the reactor, 4 and 7 inches. To meet the requirements of industrial applications, simulation has been used to scale up the effect on the commercial scale reactor. Synthetic gas was used as a feed stream and its conversion to H2 was considered. Temperature and velocity profiles were obtained for the different scales.

Three-Phase Model of a Fluidized-Bed Catalytic Reactor for Polyethylene Synthesis

Abstract A mathematical model of a bubbling fluidized-bed reactor for the production of polyolefins is presented. The model is employed to simulate a typical, commercial-scale reactor where the synthesis of polyethylene using supported catalysts is carried out. Results are used to follow the evolution of temperature within the reactor bed to avoid conditions producing polymer degradation. The fluidized bed is modeled as a heterogeneous system with a bubble gas phase and a solid-particle emulsion. The catalyst active sites are considered located within a growing, solid, ever changing particle composed of the support, the catalyst and the polymer being produced. The model sees the reactor as a three phase complex: (a) the bubble phase, transporting most of the gas entering the reactor; (b) the solid-particle phase, where polymerization takes place; and (c) the interstitial-gas phase among solid particles. Both gaseous phases move continuously upward, with different velocities, and are modeled as plug flows. For the solid-particle phase, modeling alternatives are explored, ranging from a descending plug-flow limiting case to the opposite extreme of a perfectly mixed tank related to the particle drag-effect the rising bubble produces in the bed. In the scouting process between these limits instabilities are predicted by the model. The most realistic representation of the bed is that of the two gas phases moving upward in two plug-flow patterns and the solids moving with ascending and descending trajectories due to back-mixing.

A laboratory scale fixed-bed coal conversion reactor part 1: Operation, reaction zone identification and industrial representativeness

Fixed bed coal gasification and combustion operations form an important part in the global energy supply, and these processes are characterized by complex interactions which are difficult to study on an industrial scale. A laboratory scale fixed-bed coal conversion reactor (LSR) was therefore constructed and used to mimic pilot and industrial scale fixed bed combustion and gasification. The initial design aims were to establish operating conditions comparable to that of previous pilot and commercial scale work. Secondary design aims were to keep operations less expensive, more flexible, while using smaller samples and particle sizes and maintaining representativeness. The laboratory scale reactor is 1200mm in length and has an internal diameter of 104mm. A 500mm coal bed is initially loaded into the reactor and converted to produce an ash bed of 100mm. The coal loading for this reactor was on average 3.6kg in comparison to the 240kg of the pilot scale reactor (PSR). A maximum temperature of 1250°C was maintained to assure similarities to pilot and industrial operations. Seven thermocouples measured the axial temperature profile in the reactor. Measurement capabilities inside the reactor and post experiment bed dissection have shown that bed temperature profiles and reaction zones were representative of both a pilot scale reactor (PSR) and a commercial scale reactor (ISR).

An optimized simulation model for iron-based Fischer–Tropsch catalyst design: Transfer limitations as functions of operating and design conditions

Transfer limitations were successfully modeled and optimized for iron-based catalysts for Fischer–Tropsch synthesis. The simulation model predicts the effect of changing reaction temperatures, reaction pressures, catalyst pellet size, and the feed CO composition on pore diffusion, film heat transfer, internal heat transfer, and pressure drop. The comprehensive contour maps obtained from the model quantitatively display the effects of these various design variables to both optimize catalyst design and provide guidance for kinetic experiments. The optimization results favor higher reaction temperatures and pressures, smaller pellet sizes, and lower feed CO compositions to maintain high activity of kinetically-controlled reaction rates. The optimal temperature (255.8°C) was constrained by the rate of catalytic deactivation. The model was validated by experimental data acquired from a fixed-bed reactor and shows excellent agreement. The model predicts the observed rate to be 79% of the intrinsic rate at 250°C, 20bar, equimolar H2:CO, and 425μm pellet size, while experimental results showed this percentage was 74±7% for 250–600μm pellets. The model predicts no pore-diffusion limitations at pellet sizes smaller than 250μm, indicating that the reaction rate is kinetically-controlled. Furthermore, the resistance due to film temperature gradients is more limiting than that due to intraparticle temperature gradients. Finally, pressure drop was well below 10% of the inlet reactor pressure under laboratory-scale conditions. The model was used to predict the effect of using smaller catalyst pellets on pressure drop for a commercial-scale reactor, which showed that acceptable operation could be expected with a pressure drop of 20% of the inlet reactor pressure.

A Scaling-up Synthesis from Laboratory Scale to Pilot Scale and to near Commercial Scale for Paste-Glue Production

This paper concerns on developing a synthesis meth od of paste-glue production for gummed tape using a corn-based starc h as an alternative feedstock from laboratory-scale to pilot-scale and to near commercial scale. Basically, two methods of synthesis were developed to produce paste-glue in laboratory scale. Based on the two methods, we then scale-up the earlier laboratory scale data to pilot-scale and near comme rcial-scale for developing a large scale process production of paste-glue. Scali ng up production from 1,000 ml reactor to 500 L pilot-scale reactor and 1,500 L near commercial scale reactor, we monitored pathway of temperature increase during reaction as well as adjustment of operating condition conducted for lab oratory experimental data in order to produce a good quality of paste-glue. Some scaling up parameters have been found as well as critical parameters for a goo d product quality such as viscosity and ceiling temperature of the reaction w hich are very crucial in order to give optimum operating condition. We have selected synthesis method of paste-glue production and found the range of the pa rameters in order to produce a very good quality of paste-glue in pilot scale an d near commercial scale.

Heat transfer model and scale-up of an entrained-flow solar reactor for the thermal decomposition of methane

The solar thermochemical decomposition of CH 4 is carried out in a solar reactor consisting of a cavity-receiver containing an array of tubular absorbers, through which CH 4 flows and thermally decomposes to H 2 and carbon particles. A reactor model is formulated by coupling radiation/convection/conduction heat transfer and chemical kinetics for a two-phase solid-gas reacting flow. Experimental validation is accomplished by comparing measured and simulated absorber temperatures and H 2 concentrations for a 10 kW prototype reactor tested in a solar furnace. The model is applied to optimize the design and simulate the performance of a 10 MW commercial-scale reactor mounted on a solar tower system configuration. Complete conversion is predicted for a maximum CH 4 mass flow rate of 0.70 kg s −1 and a desired outlet temperature of 1870 K, yielding a solar-to-chemical energy conversion efficiency of 42% and a solar-to-thermal energy conversion efficiency of 75%.

Reductive amination of monoethanolamine in the presence of the NiCo/BPO4 · γ-Al2O3 catalyst: Process optimization based on a mathematical model and calculation of the basic design parameters of the reactor

Based on experimental kinetic data for the reductive amination of monoethanolamine in the presence of the NiCo/BPO4 · γ-Al2O3 catalyst, a mechanism of this process is suggested and the corresponding kinetic model is constructed. A mathematical model of the reactor process is developed, and this model is used to solve three process optimization problems. Optimal values of operating parameters are found, and these values are used in the calculation of basic dimensions of a commercial-scale reactor. The flexible process design suggested allows all of the three process variants corresponding to the three optimization problems to be carried out.

Predictive Model Extraction for Polysilicon Low-Pressure Chemical Vapor Deposition in a Commercial Scale Reactor

Theoretical optimization of a polysilicon low-pressure chemical vapor deposition process in a commercial scale reactor for wafers was achieved by extracting a predictive reaction model from wafer-radial and reactor-axial deposition rate distributions. The extraction involved the radial deposition rate profile on the wafer, axial deposition rate profile in the reactor, and wafer-spacing dependence of the deposition rate at the wafer center. The deduced reaction model contains two film precursors as well as . Based on the radial deposition rate profile, the respective sticking probabilities of these two precursors were and at . Because the two precursors could not reach the wafer center due to their high sticking probabilities, as evidenced by the low deposition rate at the wafer center, the sticking probability of was at with an activation energy of . The elementary reaction simulation done here included the mass transport and the gas-phase and surface elementary reactions in the reactor. Comparison between this simulation and the experimental analysis revealed that the two film precursors probably were and .

Modeling of laboratory and commercial scale hydro-processing reactors using CFD

Trickle bed reactors (TBRs) are commonly used in chemical industries. Scale-up of TBR is difficult and simple scaling rules often lead to poor design. Flow mal-distribution, channeling, wetting of catalyst and local temperature variation are some of the important parameters which controls the overall performance of the TBRs. Fluid dynamics of the TBRs is complex and very sensitive to the scale of the reactors. Conventional modeling techniques are unable to account these key design issues. Recent advances in computational fluid dynamics (CFD) show promising results in understanding fluid dynamics and its interactions with chemical reactions. In this study we have developed a CFD model for simulating flow and reactions in the laboratory scale and commercial scale reactors. A case of hydro-processing reactions was considered. The CFD models were first evaluated by comparing the model predictions with the published experimental data. The models were then used to understand the influence of porosity distribution, particle characteristics and reactor scale on overall performance. Validated model was used to predict the performance of the commercial scale reactor. Various critical issues of scaling of TBR and how CFD modeling can help in reducing uncertainties associated with it are discussed in details. The approach, model and results presented here will be useful for understanding the complex hydrodynamics, its interaction with chemical reactions and influence of different reactor scales on performance of the TBRs.

A comparison of a batch recycle reactor and an integral reactor with fines for scale-up of an industrial trickle bed reactor from laboratory data

Observed reaction rates in trickle bed reactors are often strongly influenced by reactor hydrodynamics and transport limitations. The reaction engineer must account for these effects when designing a commercial scale reactor. This report describes the two different experimental approaches used to generate kinetic data for acetophenone hydrogenation to 1-phenylethanol over a copper catalyst. In the first approach, the active catalyst particles were diluted with inert fines. This diluted catalyst was used in a steady-state, single-pass, continuous reactor. The second experimental system used an alternative approach that measured apparent reaction kinetics under conditions of hydrodynamic equivalence to a full-scale reactor. In this approach, a batch recycle trickle bed reactor utilized complete recycle of the liquid reactor product, which was collected in a well-mixed vessel. The results of this work indicate that, for very active heterogeneous catalysts, the batch recycle trickle bed reactor is preferred to the integral reactor with fines for generation of apparent reaction kinetic data for full-sized catalyst pellets. In addition, this work outlines a methodology for developing and validating a kinetic model of an adiabatic trickle bed reactor. One byproduct of this effort is a closed form analytical expression for the effectiveness factor for a specific Langmuir–Hinshelwood rate expression in the limiting case where pore diffusion limitations are so great that one of the reactants is completely consumed before it diffuses to the end of the modeled pore.

Analysis and modeling of low pressure chemical vapor deposition of phosphorus-doped polysilicon in commercial scale reactor

In a commercial scale low pressure chemical vapor deposition (CVD) reactor, we analyzed the elementary reaction of silane based CVD with the doping gas of phosphine. The variation of conductivity in the radial direction over a monitor wafer became significant as the phosphine gas partial pressure decreased, and it reached up to about 30% at 6.5×10−4 Pa. The radial distribution of phosphorus fraction in a film, however, was smaller than 7%. On the basis of the diffusion model of chemical species into the wafer gaps, we found that the sticking probability of phosphine is 2–5×10−5, which is 1 order of magnitude larger than the one of silane. The reaction kinetics of both silane and phosphine seems almost linear, but slight nonlinearity at high phosphine concentration range was also indicated.

Simulation of the transient and steady state behaviour of a bubble column slurry reactor for Fischer–Tropsch synthesis

This paper develops a model to simulate the dynamic and steady-state behaviour of a commercial scale (diameter 7.5 m and dispersion height 30 m) Fischer–Tropsch bubble column slurry reactor operating in the churn-turbulent regime. A distinction is made between ‘large’ and ‘small’ bubble classes and the axial dispersion model is used to simulate their mixing behaviour and also of the liquid and catalyst particle phases. The results of the dynamic simulations indicate that no thermal runaways are to be expected and that steady-state is achieved within about 7 min from start-up. Analysis of the steady-state behaviour shows that the hydrogen conversion in the reactor is mainly dictated by the ‘large’ bubbles, which account for a major fraction of the gas throughput. Comparison of the commercial scale reactor performance with that of a smaller scale demonstration unit (of diameter 1 m and dispersion height 30 m) shows that due to significantly improved staging in the liquid phase, higher conversions are achieved in the demonstration unit. Furthermore, steep temperature gradients are to be expected in the demonstration unit, while these are absent in a reactor of commercial scale. The study underlines the need for accurate information on the liquid phase backmixing for scale up purposes.

The boiling slurry reactor: Axial dispersion model

We use a mathematical model that accounts for axial dispersion in both the gas and liquid phases to study the dynamics of a special configuration of a boiling slurry reactor (BSR). It is fed by a nonvolatile liquid reactant, a solvent, and a gaseous reactant and its effluent consists only of a gas. The proposed BSR configuration offers two important advantages over conventional slurry reactors, i.e., complete conversion of the liquid reactant and no need for expensive solid–liquid separation. Additionally, internal cooling devices are not needed since the reactor is cooled by evaporation of the solvent and the liquid products. The results generated by the dispersion model are compared with those of a well-mixed CSTR model. High dispersion — typical of a large diameter commercial scale reactor operating at high superficial gas velocity — leads to a reactor behavior similar to a well-mixed CSTR. Reduced backmixing does not change the qualitative reactor behavior dramatically, although temperature and concentration gradients increase, as expected. At low feed temperatures and very low axial dispersion no steady-state is reached since the reaction does not ignite at the bottom of the column. An increase of the feed temperature will stabilize the operation. A unique feature of this BSR is the possible existence of fill-up and dry-up states at which the reactor volume changes monotonically while the other state variables remain unchanged. The fill-up state will lead to spillover unless the feed and/or initial conditions are properly adjusted.

Rapid Vapor Grown Carbon Fiber Production Using the Intermittent Liquid Pulse Injection Technique

Abstract Three series of experiments were conducted to collect information for the design of a commercial scale reactor for the production of low cost vapor grown carbon fibers (VGCFs). Firstly, the effects of reaction conditions on the yield of vapor grown carbon fibers were investigated using the newly developed liquid pulse injection technique. The examined conditions were the flow rate of the carrier gas, and the amount of the catalyst source injected into the reactor as a liquid pulse. Yields up to 40% were attained under optimized conditions. Secondly, VGCFs were continuously produced by intermittently injecting the catalyst source into the reactor (intermittent liquid pulse injection technique), and the effect of the intervals of the injections on the amount of VGCFs obtained was also investigated. VGCFs were successfully obtained using this method. Finally, the growth sequences of VGCFs were investigated using benzene, toluene and xylene as the carbon source. VGCFs were obtained from each carbon source