Scale-up Of Reactors Research Articles

Gas-Liquid Phase Recirculation in Bubble Column Reactors: Development of a Hybrid Model Based on Local CFD – Adaptive Neuro-Fuzzy Inference System (ANFIS)

Abstract The Euler–Euler method and soft computing methods are recently utilized for the purpose of bubbly flow simulation and evolution of the dispersed and continuous phase in a two-phase reactor. Joining computational fluid dynamics (CFD) to the adaptive neuro-fuzzy inference system (ANFIS) method can enable the researchers to avoid several runs for heavy numerical methods (multidimensional Euler–Euler) to optimize fluid conditions. This overview can also help the researchers to carefully analyze fluid conditions and categorize their huge number of data in their artificial neural network nodes and avoid a complex non-structure CFD mesh. In addition, it can provide a neural geometry without limitation of an increasing mesh number in the fluid domain. In this study, gas and liquid circulation were considered as one of the main CFD factors in the scale-up of reactors used as an output parameter for prediction tool (ANFIS method) in different dimensions. This study shows that a combination of ANFIS and CFD methods provides the non-discrete domain in various dimensions and makes a smart tool to locally predict multiphase flow. The integration of numerical calculation and smart methods also shows that there is a great agreement between CFD results and ANFIS output depending on different dimensions.

Numerical Simulation of Biomass Growth in OKTOP®9000 Reactor at Industrial Scale.

Computational fluid dynamics is a powerful method for scale-up of reactors although it is still challenging to fully embrace hydrodynamics and biological complexities. In this article, an aerobic fermentation of Pichia pastoris cells is modeled in a batch OKTOP®9000 reactor. The 800 m3 industrial scale reactor is equipped with a radial impeller, designed by Outotec Oy for gas dispersion in the draft tube reactor. Measured Np of the impeller is used in hydrodynamics validation. The resolved energy dissipation rate is compensated, and its influence on mass transfer is analyzed and discussed. Gas–liquid drag force is modified to simulate effects of liquid turbulence and bubble swarms. Resolved steady state multiphase hydrodynamics is used to simulate the fermentation process. Temporal evolution of species concentrations is compared to experimental data measured in a small copy of the reactor at lab scale (14 L). The effect of oxygenation on the P. pastoris cells cultivation is considered.

Scale-Up of Innovative Honeycomb Reactors forPower-to-Gas Applications - The Project Store&Go.

The German “Energiewende” is heavily based on electric power and, therefore, requests solutions to serve non‐electric energy uses and to store electric energy in large scale. Synthetic natural gas (SNG) produced with hydrogen from water electrolysis and with CO2 from mainly renewable sources is one approach. For the catalytic SNG production efficient removal and utilization of the reaction heat is the main issue. A metallic honeycomb‐like carrier‐based reactor proved in laboratory scale to match this challenge. This type of reactor shows good heat conductivity and enables optimized operation. In the EU‐funded project Store&Go the honeycomb methanation is scaled up to MW‐scale. For this, heat transfer and kinetic data were determined experimentally and used in CFD calculations for the reactor design. Finally a SNG plant with 1 MW feed‐in will be built and fully integrated operation will be shown.

Tertiary treatment of landfill leachate by an integrated Electro-Oxidation/Electro-Coagulation/Electro-Reduction process: Performance and mechanism

This study presents an integrated Electro-Oxidation/Electro-Coagulation/Electro-Reduction (EO/EC/ER) process for tertiary landfill leachate treatment. The influence of variables including leachate characteristics and operation conditions on the performance of EO/EC/ER process was evaluated. The removal mechanisms were explored by comparing results of anode, cathode, and bipolar electrode substitution experiments. The performance of the process in a scaled-up reactor was investigated to assure the feasibility of the process. Results showed that simultaneous removal of carbonaceous and nitrogenous pollutants was achieved under optimal conditions. Ammonia removal was due to the free chlorine generation of EO while organic matter degradation was achieved by both EO and EC processes. Nitrate removal was attributed to both ER and EC processes, with the higher removal achieved by ER process. In a scaled-up reactor, the EO/EC/ER process was able to remove 50–60% organic matter and 100% ammonia at charge of 1.5 Ah/L with energy consumption of 15 kW h/m3. Considering energy cost, the process is more efficient to meet the requirement of organic removal efficiency less than 70%. These results show the feasibility and potential of the EO/EC/ER process as an alternative tertiary treatment to achieve the simultaneous removal of organic matter, ammonia, nitrate, and color of leachate.

Computational Fluid Dynamics simulation of hydrothermal liquefaction of microalgae in a continuous plug-flow reactor

Computational Fluid Dynamics (CFD) technique is used in this work to simulate the hydrothermal liquefaction of Nannochloropsis sp. microalgae in a lab-scale continuous plug-flow reactor to understand the fluid dynamics, heat transfer, and reaction kinetics in a HTL reactor under hydrothermal condition. The temperature profile in the reactor and the yield of HTL products from the present simulation are obtained and they are validated with the experimental data available in the literature. Furthermore, the parametric study is carried out to study the effect of slurry flow rate, reactor temperature, and external heat transfer coefficient on the yield of products. Though the model predictions are satisfactory in comparison with the experimental results, it still needs to be improved for better prediction of the product yields. This improved model will be considered as a baseline for design and scale-up of large-scale HTL reactor.

Carbon nanotubes by continuous growth, pulling and harvesting into big spools

Longer carbon nanotubes (CNT) are synthesized in a scaled-up reactor with harvesting into big spools. The synthesis rig is capable of producing CNT cotton in spools or piles in kilogram amounts. The product was studied by electron microscopy, Raman spectroscopy and thermal analysis. It was shown that depending on the synthesis conditions the resulting cotton maybe dominated either by longer double-wall CNT or by short CNT combined with non-CNT carbon. In conclusion this successful scale-up development paves the way for the development of CNT-based fibers and composites.

Modeling Pore-Scale Two-Phase Flow: How to Avoid Gas-Channeling Phenomena in Micropacked-Bed Reactors via Catalyst Wettability Modification

A model capable of providing a reliable estimation of two-phase flow dynamics and mass-transfer coefficients, is lacking for the design of micropacked-bed reactors via correlations, especially when the particle size of the bed is around 100 μm. In this work, we present a validation of the use of the phase field method for reproducing two-phase flow experiments found in the literature. This numerical simulation strategy sheds light on the impact of the micropacked-bed geometry and wettability on the formation of preferential gas channels. Counterintuitively, to homogenize the two-phase flow hydrodynamics and reduce radial mass-transfer limitations, solvent wettability of the support needs to be restricted, showing best performance when the contact angle ranges to 60° and capillary forces are still dominant. The tuning of gas–liquid–solid interactions by surface wettability modification opens a new window of opportunity for the design and scale-up of micropacked-bed reactors.

Modeling and validation of a pilot-scale aqueous mineral carbonation reactor for carbon capture using computational fluid dynamics

In anticipation of the successful establishment of carbon capture, utilization, and storage (CCUS) technology, a pilot-scale aqueous mineral carbonation plant, that removes CO2 through a reaction with a Ca(OH)2 solution, was built in Incheon, South Korea. Using computational fluid dynamics (CFD), two reactors with a diameter of 2.2 m and a height of 6.0 m were modeled and validated for reactor scale-up and optimization. Because a direct simulation of bubble breakage, coalescence, and interphase mass transfer results in enormous computational costs for modeling the pilot-scale multiphase reactor, a CFD-lumped correlation model was introduced to simulate a large reactor; this resulted in acceptable computational costs and maintained the simulation accuracy. In order to ensure the acceptability of the CFD model, two-step verification was conducted. The CFD model results were compared with the experimental data and published empirical correlations with regard to the gas holdup, interfacial area, and mass transfer coefficient. Subsequently, the CO2 removal efficiencies of the CFD model were compared with the pilot-plant data. The errors of the CFD model for three hydrodynamic parameters and the CO2 removal efficiencies were in the range of 1–8%. The validated CFD model will be used for designing a four times larger mineral carbonation reactor, that will be built in 2017.

A Reaction Database for Small Molecule Pharmaceutical Processes Integrated with Process Information

This article describes the development of a reaction database with the objective to collect data for multiphase reactions involved in small molecule pharmaceutical processes with a search engine to retrieve necessary data in investigations of reaction-separation schemes, such as the role of organic solvents in reaction performance improvement. The focus of this reaction database is to provide a data rich environment with process information available to assist during the early stage synthesis of pharmaceutical products. The database is structured in terms of reaction classification of reaction types; compounds participating in the reaction; use of organic solvents and their function; information for single step and multistep reactions; target products; reaction conditions and reaction data. Information for reactor scale-up together with information for the separation and other relevant information for each reaction and reference are also available in the database. Additionally, the retrieved information obtained from the database can be evaluated in terms of sustainability using well-known “green” metrics published in the scientific literature. The application of the database is illustrated through the synthesis of ibuprofen, for which data on different reaction pathways have been retrieved from the database and compared using “green” chemistry metrics.

Development and Validation of a Process Model To Describe Pyrolysis of Forestry Residues in an Auger Reactor

In this study, a process model for an auger-style biomass pyrolysis reactor is developed to use as a tool in process optimization and scaleup. The plug-flow model for both solid and gas phases is assumed. A comparison between the kinetic models widely used in the literature to the experimental data was performed to determine the “best” kinetic model for our system. The transport equations for each phase are combined with the kinetic model to predict bio-oil, char, and non-condensable gas yields. The applied model was validated with experimental data from a 2–4 kg/h pilot-scale auger reactor. This reactor uses steel shot as a heat carrier and without carrier gas. The results show good agreement between experimental data and model prediction. The model was used to predict the yield of bio-oil as a function of the temperature, feed flow rate, and reactor pressure. These simulations indicate that the model is a useful tool in design and scaleup of auger-type pyrolysis reactors using a heat carrier.

Experimental study and numerical simulation of barium sulfate precipitation process in a continuous multi-orifice-impinging transverse jet reactor

Fast jet mixing plays an important role in the intensification of precipitation process. In this work, the precipitation of barium sulfate in a multi-orifice-impinging transverse (MOIT) jet reactor was studied experimentally and numerically. RANS approach coupled with population balance equation (PBE) model was used to predict the process. Large scale variance and small scale variance were solved to evaluate the effect of macromixing and micromixing on the precipitation process, respectively. The influence of Reynolds number (ReM), initial feeding concentration of reactants (C0), and the scale-up of the jet reactor, on the distribution of supersaturation ratio, nucleation rate and crystal growth rate was discussed. The precipitation process can be intensified (here referring to producing smaller nanoparticles with narrower particle size distribution) by increasing ReM at lower ReM region or when the jet reactor is scaled up, or by increasing C0 when C0 is less than 0.4kmol/m3.

Predicting hydrodynamic parameters and volumetric gas–liquid mass transfer coefficient in an external-loop airlift reactor by support vector regression

For modeling, design and scale-up of the airlift reactors, it is crucial to estimate hydrodynamic parameters and volumetric gas–liquid mass transfer coefficient for different flow regimes. Prediction of these variables had begun by applying empirical power low correlations and later evolved in use of the artificial neural networks (ANN) as the best option available in the literature. The objective of this study was to present the support vector regression (SVR) model that predicts the gas holdup, downcomer liquid velocity and volumetric gas–liquid mass transfer coefficient values in the external-loop airlift reactor better than ANN. Furthermore, to demonstrate the applicability of the SVR model, it was used on the different literature data sets with wide-ranging databanks. The statistical error analysis revealed that the proposed generalized SVR model had more precisely prediction than ANN with an average absolute relative error (AARE) of 2.17%, 1.32% and 9.64% for gas holdup, downcomer liquid velocity and volumetric gas-liquid mass transfer coefficient values, respectively.

Process scale-up considerations for non-thermal atmospheric-pressure plasma synthesis of nanoparticles by homogenous nucleation

Scale-up of non-thermal atmospheric-pressure plasma reactors for the synthesis of nanoparticles by homogeneous nucleation is challenging because the active volume is typically reduced to facilitate gas breakdown, enhance discharge stability, and limit particle size and agglomeration, but thus limits throughput. Here, we introduce a dielectric barrier discharge reactor consisting of a coaxial electrode geometry for nanoparticle production that enables a simple scale-up strategy whereby increasing the outer and inner electrode diameters, the plasma volume is increased approximately linearly, while maintaining a sufficiently small electrode gap to maintain the electric field strength. We show with two test reactors that for a given residence time, the nanoparticle production rate increases linearly with volume over a range of precursor concentrations, while having minimal effect on the shape of the particle size distribution. However, our study also reveals that increasing the total gas flow rate in a smaller volume reactor leads to an enhancement of precursor conversion and a comparable production rate to a larger volume reactor. These results suggest that scale-up requires better understanding of the influence of reactor geometry on particle growth dynamics and may not always be a simple function of reactor volume.

Numerical simulation of scale-up effects of methanol-to-olefins fluidized bed reactors

Scale-up of fluidized bed reactors has long been regarded as a big challenge in chemical reaction engineering. While traditional scaling theories are mostly based on hydrodynamics similarity, computational fluid dynamics (CFD) aided approach allows direct coupling between hydrodynamics and reaction factors and is expected to speed up the experiment-based scale-up process with lower cost. In this study, we aim to investigate the scale-up effects through simulations of a series of methanol-to-olefins (MTO) reactors of different sizes. The two-fluid model and energy-minimization multi-scale (EMMS)-based drag models are combined in simulations. The fluidization characteristics in terms of flow structures, velocity distribution, mass fractions of gaseous product and coke distribution are presented against available experimental data for different-sized reactors. It is found that typical hydrodynamic features can be reasonably predicted, while the prediction of reaction behavior shows growing discrepancy with increasing reactor size. Possible reasons are discussed in the last section along with future work presented for scale-up studies.

Multiscale Computational Fluid Dynamics–Population Balance Model Coupled System of Atom Transfer Radical Suspension Polymerization in Stirred Tank Reactors

Partially water-soluble monomers achieve phase equilibrium between aqueous and dispersed phases, and the interphase mass transfer plays a significant role in suspension polymerization. This work developed a computational fluid dynamics model to simulate the liquid–liquid suspension polymerization process. Complex multiphase flow behaviors and multiscale polymer properties were simultaneously simulated using the combination of an Eulerian–Eulerian two-phase flow model, an atom transfer radical polymerization kinetics model, a population balance model (PBM), and an interphase transfer model. The simulation results for monomer conversion, molecular weight (Mn), polydispersity index (PDI), and Sauter mean diameter (d32) agreed well with the experimental data, thereby validating the soundness of the multiscale model. The proposed model was then employed to predict key variables of the polymerization system. The coupled model can benefit the optimization and scale-up of suspension polymerization reactors with s...

Comprehensive Analysis of Sorption Enhanced Steam Methane Reforming in a Variable Volume Membrane Reactor

The use of combined reaction-separation processes in steam methane reforming (SMR) has recently received significant attention as an enticing route to meet the challenging requirements of distributed hydrogen production for fuel cell vehicles. While many of the investigations in recent literature focus solely on either CO2 adsorption or selective H2 membrane permeation to reduce the reactor footprint and the temperature required to drive the endothermic reaction in continuous flow reactors, the CHAMP-SORB is a new variable volume, transient batch reactor technology that utilizes both strategies simultaneously. Building upon our prior study in which we experimentally demonstrated the viability of CHAMP-SORB reactor concept on bench scale, this work focuses on understanding the heat/mass transfer and reaction/separation interactions to develop guidelines for the reactor scale-up. A combined transport-kinetic model is developed, including spatial variations of SMR reaction and CO2 adsorption rates within the...

Highlights from the Flow Chemistry Literature 2016 (Part 4)

In this Section of the journal, the literature on continuous flow synthesis (primarily organic synthesis and functional materials) from the period of October - December 2016 is presented. All the publications are listed ordered by journal name, with two Review articles appearing at the end. In this quarter the number of papers on continuous flow organic synthesis is relatively less as a few special issues are planned in the coming months. Two contributions on machine learning for optimization in flow synthesis and the scale-up of continuous flow reactors from Eli Lilly are the real highlights of this quarter!

Computational Fluid Dynamic Application in Scale-up of a Stirred-batch Reactor for Degumming Crude Palm Oil

Computational Fluid Dynamic Application in Scale-up of a Stirred-batch Reactor for Degumming Crude Palm Oil

Scaled-up electrochemical reactor with a fixed bed three-dimensional cathode for electro-Fenton process: Application to the treatment of bisphenol A

In this study, we report on the development of an open undivided electrochemical reactor with a compact fixed bed of glassy carbon pellets as three-dimensional cathode for the application of electro-Fenton process. Bisphenol A (BPA) was chosen as model molecule in order to improve its efficiency to the treatment of persistent pollutants. The study of the BPA removal efficiency in function of the applied current intensity was investigated in order to determine the limiting current of O2 reduction (optimal conditions of H2O2 production at flow rate of 0.36m3.h−1) which was 0.8A (0.5A/100g of glassy carbon pellets). Many parameters have been carried out using this electro-Fenton reactor namely degradation kinetics, influence of anodic reactions on DSA, effect of initial pollutant concentration. In the optimal current condition, the global production rate of H2O2 and OH was investigated. The yield of electro-Fenton reaction (conversion of H2O2 to OH) was very high (>90%). The absolute rate of BPA degradation was determined as 4.3×109M−1s−1. COD, TOC and BOD5 measurements indicated that only few minutes of treatment by electro-Fenton process were needed to eliminate BPA for dilute solutions (10 and 25mg.L−1). In this case, the biodegradability of the treated solutions occurred rapidly. For higher concentration levels, an efficient removal of BPA appeared for treatment time higher than 1hour and more than 90minutes were necessary to obtain the biodegradability of BPA solutions. In optimum conditions, the scale-up of the electrochemical reactor applied to electro-Fenton process was suggested and depended on the concentration level of the pollutant. The operating parameters of the scaled-up reactor might be deduced from the new section of each fixed bed exposed to the flow, from values of liquid flow velocity and from the corresponding limiting current density obtained with the reactor at laboratory scale. The compact fixed bed cathode in an open undivided electrochemical reactor appears as an appropriate solution as pre-treatment electro-Fenton process followed by the biological treatment of persistent pollutant.

Pilot-Plant Production of Gas-to-Liquid Synthetic Fuel Using Gasified Biomass over a Novel Biochar-Supported Catalyst

Gasified biomass syngas has been successfully used to produce liquid hydrocarbons at pilot scale using a novel biochar-supported catalyst. Producer gas from a downdraft gasifier was made from woodchips and contained 53% N2, 17% CO, 14% H2, 13% CO2, and 2% CH4 after undergoing a rigorous scrubbing and refining process. The producer gas was successfully scrubbed so that the catalyst contaminants contained in the gas (e.g., NH4 and O2) were lower than 1 ppm. This study involved over 2000 h of biomass syngas trials at the pilot plant and achieved objectives to better understand and overcome challenges associated with reactor scale-up. A mass balance closure of ±5% was achieved. Producer gas, which flowed through the system only once (without a recycle loop), had a CO conversion of 59% or greater after being introduced to the novel biochar-supported catalyst. The pilot-scale catalyst bed had a much greater surface area for the gas to flow through than previously tested lab-scale reactors (approximately 15 times more surface area), which allowed channels to form and flow regimes to be more inconsistent than in the smaller reactor tubes. This accounted for the lower yield, so smaller tubes are suggested to improve efficiency and overall yield.