Slurry Bubble Column Reactor Research Articles

Discrete bubble modeling for a micro-structured bubble column

Gas–liquid flows with solid catalyst particles are encountered in many applications in the chemical, petrochemical, pharmaceutical industries, etc. Most commonly, two reactor types are applied for large scale in the industry. They are slurry bubble column and trickle bed reactors. Both of these types of reactors have some disadvantages limiting their efficiencies. To overcome these disadvantages, a novel reactor type, micro-structured bubble column (MSBC), is proposed. In the MSBC, the micro-structuring of catalytic material is realized by introducing a static mesh of thin wires coated with catalyst inside the column. Wires also serve the purpose of cutting the bubbles, which in turn results in high interfacial area and enhanced interface dynamics. The static catalytic mesh also ensures lower cost by avoiding filtration of catalyst particles. Numerical formulation of the described reactor is based on the 3-D discrete bubble model (DBM) presented in the previous works of Darmana et al. (2005, 2007). The extended version of DBM presented here introduces wires in the existing model and studies their effect on liquid and bubble dynamics. Bubbles and wires are represented by spherical and cylindrical markers, respectively; and the liquid flow-field is solved in the Eulerian gird cells. An improved drag correlation for bubbles in dense (up to 50%) swarm flow is also incorporated in the model. The model implementation and results are verified for a wide spectrum of parameters from the data available from the previous studies, analytical results and experimental findings. Our results show that the model is able to predict the hydrodynamic behavior and bubble dynamics, including the cutting of bubbles through wire mesh, very well.

Hydrodynamic effect of oxygenated byproduct during Fischer–Tropsch synthesis in slurry bubble column

The Fischer–Tropsch reaction was performed using a pilot-scale slurry bubble column reactor (SBCR) and a lab-scale continuous stirred tank reactor (CSTR). In contrast to the CSTR, a transitory induction period was observed in the SBCR. In this study, we investigated the catalyst performance during the induction period focusing on the hydrodynamic parameter changes inside the reactor. We measured the hydraulic pressure for the constant slurry thickness during FTS reaction. The FT wax product was regularly withdrawn using a metal filter and analyzed for density, oxygen concentration, and compositional analysis. The liquid density was affected by the dilution of the initial liquid media by fresh FT product for the whole reaction time of 180h. On the other hand, the oxygen concentration increased sharply for the initial 85h and then reached the steady state. Accordingly, the gas hold-up and CO conversion were enhanced for the same period. The increase in the gas hold-up could be explained by the coalescence inhibition effect of oxygenated compounds, which were the main byproducts when iron-based catalysts were used. The dynamic gas disengagement technique was employed to identify the coalescence inhibition effect of alcohol in the hydrocarbon system using a cylindrical acrylic bubble column.

Numerical Simulation of Hydrodynamics in Slurry Bubble Column Reactor

Gas dispersion and solid suspension in industrial size slurry bubble column reactors for producing sodium dichromate are simulated numerically by using of computational fluid dynamics (CFD). The Eulerian multi-fluid model and standard k-ε turbulence model are used to describe the flow behavior in bubble columns. The simulated results show that gas is easy to flow toward the centre of the bubble column and in relatively high local gas holdup there. Installing gas-re-distributors in the bubble column is favorable for gas dispersion. Solid suspension in the bubble columns under the operating condition we investigated is relatively uniform.

Efficient filtration system for paraffin-catalyst slurry separation

The filtration efficiency for separating liquid paraffin (or water) from a slurry consisting of 25 weight% spherical alumina in a Slurry Bubble Column Reactor (SBCR) comprised of a cylindrical tube of 10 cm diameter and 150 cm length was studied. Various differential pressures (?P) were applied to two separate tubular sintered metal stainless steel filter elements with nominal pore size of 4 and 16?m. The experimental results disclosed that the rate of filtrations increased on applying higher differential pressure to the filter element. Albeit this phenomenon is limited to moderate ?Ps and for ?P more than 1 bar is neither harmful nor helpful. The highest filtration rates at ?Ps higher than 1 bar were 170 and 248 ml/minute for 4 and 16?m respectively. Using water as the liquid in slurry the rate of filtration enhanced to 4 folds, and this issue reveals impact of viscosity on filtration efficiency clearly. In all situations, the total amount of particles present in the filtrate part never exceeded a few parts per million (ppm). The statistical analysis of the SEM image of the filtrate indicated that by applying higher pressure difference to the filter element the frequency percent of larger particle size increases. The operation of filter cake removing was performed with back flashing of 300 ml of clean liquid with pressures of 3-5 bar of N2 gas.

A Comparison between Heterogeneous and Homogeneous Gas Flow Model in Slurry Bubble Column Reactor for Direct Synthesis of DME

In the present study, a heterogeneous and homogeneous gas flow dispersion model for simulation and optimisation of a large-scale catalytic slurry reac tor for the direct synthesis of dimethyl ether (DME) from syngas and CO2, using a churn-turbulent regime was developed. In the hetero geneous gas flow model the gas phase was distributed into two bubble phases: small and large, however in the homogeneous one, the gas phase was distributed into only one large bubble phase. The r esults indicated that the heterogeneous gas flow model was in more a greement with experimental pilot plant data than the homogeneous one. Keywords—Modelling, Slurry bubble column, Dimethyl ether synthesis, Homogeneous gas flow, Heterogeneous gas flow

Modeling of a slurry bubble column reactor for Fischer-Tropsch synthesis

On the basis of the global CO consumption rate model, the lumped product distribution model and the sedimentation-dispersion model of a catalyst, a steady-state, one-dimensional mathematical model of the slurry bubble column reactor for Fischer-Tropsch synthesis were established. The mathematical simulation of the slurry bubble column reactor for Fischer-Tropsch synthesis was carried out under the following typical industrial operating conditions: temperature 230 °C, pressure 3.0 MPa, gas flow 5×105 m3/h, catalyst content in slurry phase 30%, reactor diameter 5.0 m and the composition of feed gas: y(H2)=0.60, y(CO)=0.30, y(N2)=0.10. The influences of operating pressure, temperature and m(H2)/m(CO) in feed gas on the reactor’s reaction performance were simulated.

Mathematical modeling of a slurry reactor for DME direct synthesis from syngas

In this paper, an axial dispersion mathematical model is developed to simulate a three-phase slurry bubble column reactor for direct synthesis of dimethyl ether (DME) from syngas. This large-scale reactor is modeled using mass and energy balances, catalyst sedimentation and single-bubble as well as two-bubbles class flow hydrodynamics. A comparison between the two hydrodynamic models through pilot plant experimental data from the literature shows that heterogeneous two-bubbles flow model is in better agreement with the experimental data than homogeneous single-bubble gas flow model. Also, by investigating the heterogeneous gas flow and axial dispersion model for small bubbles as well as the large bubbles and slurry (i.e. including paraffins and the catalyst) phase, the temperature profile along the reactor is obtained. A comparison between isothermal and non-isothermal reactors reveals no obvious performance difference between them. The optimum values of reactor diameter and height were obtained at 7 m and 50 m, respectively. The effects of operating variables on the axial catalyst distribution, DME productivity and CO conversion are also investigated in this research.

Oxygen mass transfer coefficient in bubble column slurry reactor with ultrafine suspended particles and neural network prediction

AbstractThe gas–liquid volumetric mass transfer coefficient was determined by the dynamic oxygen absorption technique using a polarographic dissolved oxygen probe and the gas–liquid interfacial area was measured using dual‐tip conductivity probes in a bubble column slurry reactor at ambient temperature and normal pressure. The solid particles used were ultrafine hollow glass microspheres with a mean diameter of 8.624 µm. The effects of various axial locations (height–diameter ratio = 1–12), superficial gas velocity (uG = 0.011–0.085 m/s) and solid concentration (εS = 0–30 wt.%) on the gas–liquid volumetric mass transfer coefficient kLaL and liquid‐side mass transfer coefficient kL were discussed in detail in the range of operating variables investigated. Empirical correlations by dimensional analysis were obtained and feed‐forward back propagation neural network models were employed to predict the gas–liquid volumetric mass transfer coefficient and liquid‐side mass transfer coefficient for an air–water–hollow glass microspheres system in a commercial‐scale bubble column slurry reactor. © 2012 Canadian Society for Chemical Engineering

Heat Transfer in a Slurry Bubble Column Reactor: A Critical Overview

Studies of heat transfer in slurry bubble column reactors have been reviewed and observed differences analyzed based on available data. Heat transfer in these reactors is a strong function of some parameters and a weak function of others. The parameters significantly influencing heat transfer in these reactors are the superficial gas velocity, thermophysical properties of liquid and solid particles, and size and concentration of the particles. Moreover, the rate of change with a parameter is dependent on the operating flow regime, particle properties, and presence of internals. Of all of the parameters, the effect of the particles is more complex and inadequately understood because particles influence the flow regime transition and thermophysical and rheological properties of the suspension, which, in turn, affect the hydrodynamic behavior and associated heat-transfer characteristics. The effects of the column diameter and internals have been investigated by a limited number of studies. A comparison of available data shows that the effect of the column diameter on heat transfer diminishes above 0.3 m. This, however, requires confirmation from larger-diameter studies together with associated hydrodynamic studies and appropriate modeling. Literature correlations for the heat-transfer coefficient have been reviewed and their limitations and applicability discussed. Axial and radial variations of heat-transfer coefficients reported in literature studies require appropriate design considerations.

Development of a computational multiphase flow model for Fischer Tropsch synthesis in a slurry bubble column reactor

The Hybrid Energy Systems Testing (HYTEST) Laboratory at the Idaho National Laboratory was established to develop and test hybrid energy systems with the principal objective of reducing dependence on imported fossil fuels. A central component of the HYTEST is the slurry bubble column reactor (SBCR) in which the gas-to-liquid reactions are performed to synthesize transportation fuels using the Fischer Tropsch (FT) process. These SBCRs operate in the churn-turbulent flow regime, which is characterized by complex hydrodynamics, coupled with reacting flow chemistry and heat transfer. Results, our team is developing a research tool to aid in understanding the physicochemical processes occurring in the SBCR. A robust methodology to couple reaction kinetics and mass transfer into a four-field model (consisting of the bulk liquid, small bubbles, large bubbles and solid catalyst particles) consisting of thirteen species, which are CO reactant, H 2 reactant, hydrocarbon product, and H 2O product in small bubbles, large bubbles, and the bulk fluid plus catalyst is outlined. Mechanistic submodels for interfacial momentum transfer in the churn-turbulent flow regime are incorporated, along with bubble breakup/coalescence and two-phase turbulence submodels. The absorption and kinetic models, specifically changes in species concentrations, have been incorporated into the mass continuity equation. The reaction rate is based on the macrokinetic model for a cobalt catalyst developed by Yates and Satterfield. The model includes heat generation produced by the exothermic chemical reaction, as well as heat removal from a constant temperature heat exchanger. A property method approach is employed to incorporate vapor–liquid equilibrium (VLE) in a robust manner. Physical and thermodynamic properties as functions of changes in both pressure and temperature are obtained from VLE calculations performed external to the computational multiphase fluid dynamics (CMFD) solver. The novelty of this approach is in its simplicity, as well as its accuracy over a specified temperature and pressure range.

Kinetic modeling of the Fischer–Tropsch synthesis in a slurry phase bubble column reactor using Langmuir–Freundlich isotherm

We employed the Langmuir–Freundlich isotherm for Fischer–Tropsch synthesis as a modification of the commonly used Langmuir isotherm, because the Langmuir–Freundlich isotherm can predict the adsorption of gases at solid absorbent more accurately than Langmuir isotherm. Several mechanisms for kinetic modeling of the Fischer–Tropsch synthesis have been developed in which the Langmuir isotherm is the basis of kinetic modeling of the catalytic reactions. Using Langmuir–Freundlich–Hinshelwood (LFH) model, the results of CO conversion in a slurry bubble column reactor show a very good agreement with the experiment. Moreover, we used fugacity instead of the pressure that leads to improve the accuracy of the new kinetic model. The fugacity term has been considered here by using Peng–Robinson Equation of State, modified by Gasem et al. The new kinetic model with fugacity is applied for modeling of a slurry bubble column reactor over the wide range of the reactor conditions of 523–563K, 0.95–2.55MPa and H2/CO ratio: 0.65–1.51. The results of the new kinetic LFH‐fugacity model shows the Average Absolute Deviation percentage (AAD%) of 4.25% for the CO conversion while this value is about 10.89% using the original equation based on Langmuir isotherm.

Heat Transfer Coefficients in Mimicked Fischer-Tropsch Slurry Bubble Columns

To provide more support for Fischer–Tropsch (FT) slurry bubble column reactor design, scale-up, and performance, the effects of operating conditions on the heat transfer coefficients were investigated in a mimicked FT cold flow system (compressed air:C9–C11:FT catalyst carrier). The studied operating conditions varied in superficial gas velocity (up to 0.3 m/s), pressure (up to 10 bar), and solids concentration (up to 25 vol %). The effects of these variables on heat transfer coefficients are discussed and analyzed. The increase in pressure tended to reduce the heat transfer coefficient, while the increase in solids loading enhanced the heat transfer coefficient, especially at high solids loading (25 vol %).

A novel slurry bubble column membrane reactor concept for Fischer–Tropsch synthesis in GTL technology

Fischer–Tropsch synthesis (FTS) plays an important role in the production of ultra-clean transportation fuels, chemicals, and other hydrocarbon products. In this work, a novel combination of fixed-bed and slurry bubble column membrane reactor for Fischer–Tropsch synthesis has been proposed. In the first catalyst bed, the synthesis gas is partially converted to hydrocarbons in a water-cooled reactor which is fixed bed. In the second bed which is a membrane assisted slurry bubble column reactor, the heat of reaction is used to preheat the feed synthesis gas to the first reactor. Due to the decrease of H2/CO to values far from optimum reactants ratio, the membrane concept is suggested to control hydrogen addition. A one-dimensional packed-bed model has been used for modeling of fixed-bed reactor. Also a one-dimensional model with plug flow pattern for gas phase and an axial dispersion pattern for liquid-solid suspension have been developed for modeling of slurry bubble column reactor. Proficiency of a membrane FTS reactor (MR) and a conventional FTS reactor (CR) at identical process conditions has been used as a basis for comparison in terms of temperature, gasoline yield, H2 and CO conversion as well as selectivity. Results show a favorable temperature profile along the proposed concept, an enhancement in the gasoline yield and, thus a main decrease in undesirable product formation. The results suggest that utilizing this type of reactor could be feasible and beneficial. Experimental proof of concept is needed to establish the validity and safe operation of the proposed reactor.

Genetic algorithm strategy (GA) for optimization of a novel dual-stage slurry bubble column membrane configuration for Fischer–Tropsch synthesis in gas to liquid (GTL) technology

In this work, a novel configuration of a cascade double membrane assisted slurry bubble column reactor and hydrogen-permselective membrane reactor is proposed (SDMR) for Fischer–Tropsch synthesis (FTS). A one-dimensional heterogeneous model in first reactor and axial dispersion model (AMD) for both gas and liquid–solid suspension as a homogeneous phase for slurry bubble column reactor has been developed. Subsequently, this novel configuration was optimized. Here, genetic algorithm (GA) method was applied as powerful method for optimization of procedure. The proposed model has been used to compare the performance of an SDMR with a Fluidized-bed membrane dual-type reactor (FMDR) and a conventional reactor (CR). The simulation results show an enhancement in the gasoline production, a main decrease in undesirable product formation and a favorable temperature profile along the proposed concept rather than conventional reactor and even FMDR.

Estimation of mid‐distillates production rate in a low temperature Fischer–Tropsch process

AbstractBACKGROUND: The Fischer–Tropsch process is the most important path for converting natural gas to high quality liquid hydrocarbons. Low temperature Fischer–Tropsch synthesis in slurry bubble column reactors with cobalt‐based catalysts is used for mid‐distillates production.RESULTS: In this work the slurry bubble column reactor was simulated by applying the two‐bubble class mathematical model. In addition, the effect of operating parameters on synthesis gas conversion was studied. The distribution of products was also predicted from the simulation framework.CONCLUSIONS: The effect of synthesis gas inlet velocity on mid‐distillates production rate was studied in the present work. A maximum production rate for mid‐distillates of about 23 kg s−1 was predicted from the simulation program. Copyright © 2011 Society of Chemical Industry

Erratum To the article “Simulation of Catalyst On-Line Replacement for Fischer-Tropsch Synthesis in Slurry Bubble Column Reactor” by Wei Fan, Xu Hao, Yuanyuan Xu, and Yongwang Li, Vol. 47, No. 2, pp. 116–133, May, 2011

Erratum To the article “Simulation of Catalyst On-Line Replacement for Fischer-Tropsch Synthesis in Slurry Bubble Column Reactor” by Wei Fan, Xu Hao, Yuanyuan Xu, and Yongwang Li, Vol. 47, No. 2, pp. 116–133, May, 2011

Simulation of catalyst on-line replacement for Fischer-Tropsch synthesis in slurry bubble column reactor

A multi-phase dynamic model has been developed for Fischer-Tropsch synthesis in a slurry bubble column reactor operating in a heterogeneous flow regime. The catalyst particles concentration distribution, deactivation, and on-line replacement were considered in this model. The population balance equation model has been utilized to calculate the catalyst age distribution. Based on the dynamic model, the process of catalyst replacement has been investigated, and the effect of catalyst replacement on the design and operation of the reactor has been studied. A correlation between the catalyst replacement rate and the catalyst activity has been developed in this research $ \left[ {{A_C} = \left( {1 - {\alpha_\infty }} \right){e^{ - {k_d}t}} + {\alpha_\infty }} \right] $ .

Hydrokinetic optimization of commercial scale slurry bubble column reactor

AbstractAn in‐depth numerical study has been carried out to investigate a high‐pressure commercial scale (2–8 m diameter, 30–40 m in height) slurry bubble column reactor. Typical superficial gas velocities are in the range of 0.5–3 m/s, and overall vapor holdups are in the range of 0.45–0.85. The study revealed that steady compartmental reaction models do not match plant data when reaction time constants are fast. Also, off‐the‐shelf commercial computational fluid dynamics codes do not produce useful information about a reactive column of this scale without first validating the model using data “anchors” from full‐scale operational columns. Important measures include both transient and time‐averaged profiles, integrals, and extrema of vapor holdup and reactants. Reactor designs based on this study show both improved productivity and product quality, allowing record production from existing plants along with substantial capital scope reduction for new plants. © 2011 American Institute of Chemical Engineers AIChE J, 2012

Kinetic study on carbonation of crude Li2CO3 with CO2-water solutions in a slurry bubble column reactor

Investigations were conducted to purify crude Li2CO3 via direct carbonation with CO2-water solutions at atmospheric pressure. The experiments were carried out in a slurry bubble column reactor with 0.05 m inner diameter and 1.0 m height. Parameters that may affect the dissolution of Li2CO3 in the CO2-water solutions such as CO2-bubble perforation diameter, CO2 partial pressure, CO2 gas flow rate, Li2CO3 particle size, solid concentration in the slurry, reaction temperature, slurry height in the column and so on were investigated. It was found that the increases of CO2 partial pressure, and CO2 flow rate were favorable to the dissolution of Li2CO3, which had the opposite effects with Li2CO3 particle size, solid concentration, slurry height in the column and temperature. On the other hand, in order to get insight into the mechanism of the refining process, reaction kinetics was studied. The results showed that the kinetics of the carbonation process can be properly represented by 1−3(1−X)2/3+2(1–X)=kt+b, and the rate-determining step of this process under the conditions studied was product layer diffusion. Finally, the apparent activation energy of the carbonation reaction was obtained by calculation. This study will provide theoretical basis for the reactor design and the optimization of the process operation.

10.2478/s11814-009-0260-1

Fischer-Tropsch synthesis for the production of C5+ hydrocarbons from syngas was carried out in a tubular fixed bed reactor (TFBR) and in a slurry bubble column reactor (SBCR). The Co-based catalysts for FTS were prepared by the conventional wet-impregnation of γ-Al2O3. Effects of operating conditions such as GHSV (1,000–4,000 ml/g·hr), reaction temperature (220–250°C) and pressure (0.5–3.0MPa) on the CO conversion and product selectivity of Co/γ-Al2O3 catalyst were examined in the TFBR and SBCR. The C5+ selectivity and olefin selectivity in an SBCR were found to be higher than that in a TFBR, whereas C2–C4 selectivity showed a reverse trend. The CO conversion and product distribution in an SBCR were less sensitive than that in a TFBR with variations of reaction conditions.