High Gas Flow Rates Research Articles

Novel oxygen partial pressure relaxation technique for study of oxygen exchange in nonstoichiometric oxides. The model of relaxation kinetics

The development of the theoretical background of a new relaxation technique based on pO2 monitoring at the outlet of the continuous-flow fixed-bed reactor is presented. The model describes the relaxation kinetics of oxygen exchange between the nonstoichiometric oxide and the gas phase in a case when surface reaction is the rate-limiting step. The model takes into account the feedback between the oxygen exchange rate and the oxygen partial pressure in the reactor: the rate is affected by oxygen released or uptaken by the sample. In the frame of material-gas feedback approach the influence of the sweep gas flow rate on the relaxation rate constant is shown. An analytical expression which allows determining correct value of the key material kinetic characteristic (surface exchange rate constant) from experimentally measured relaxation rate constant is derived. The proposed feedback approach has the versatility: the correction of the relaxation rate constant is necessary not only for the novel oxygen partial pressure relaxation method, but also for the other traditional relaxation techniques when oxides possess high oxygen exchange rate that does not allow to maintain constant oxygen partial pressure in the reactor even with high sweep gas flow rate.

Experimental study of horizontal air-water plug-to-slug transition flow in different pipe sizes

The current work investigates the plug-to-slug transition in horizontal air–water two-phase flow in small (38.1 mm) and large (101.6 mm) diameter pipes. An extensive database is established to study the local interfacial structure in plug-to-slug transition flow. Detailed measurements across the flow area are performed for nine and six test conditions in small and large pipes, respectively, at three different axial locations downstream of the inlet using the local four-sensor conductivity probe. The effects of jg, jf, development length and pipe size are investigated. It is found that the number of small bubbles in the liquid plug/slug increases significantly in plug-to-slug transition with increasing jg, which are generated by the strong shear between the gas slug and liquid film. Due to the relative motion, these small bubbles either coalesce with the nose of the following plug/slug bubble, or slide between the plug/slug bubble and the wall, and then travel around the pipe circumference to reside beneath the large bubbles. This explains the large number of small bubbles observed at the top of the liquid film for the conditions at high gas flow rates. In the process of traveling downwards, some of the small bubbles coalesce with the slug bubbles. It is also found that increasing jg or jf decreases the size of the small bubbles. While shearing-off is believed to dominate as jg increases, turbulent-impact is enhanced as jf increases due to the increasing turbulence level in the liquid phase. Increasing jg, development length, or decreasing jf slightly increases the depths of the plug/slug bubbles; however, significant growth of plug/slug bubbles is observed in the axial direction. For the same condition, the contribution from large bubbles to total void fraction increases as pipe size increases, while the distribution of total void fraction is similar. The size of both small and large bubbles is found to be larger in the large diameter pipe. Due to the current bubble injection mechanism, small bubbles are generated at the inlet; they coalesce into large bubbles as the flow develops. The large bubble is found to accelerate as it grows along the axial direction, which can lead to a decreasing void fraction although pressure keeps decreasing.

CFD Investigation of the effects of bubble aerator layouts on hydrodynamics of an activated sludge channel reactor

ABSTRACTIn this paper, computational fluid dynamics (CFD) simulations are employed to characterize the effects of bubble aerator layouts (i.e. spatial arrangement) on the hydrodynamics in activated sludge (AS) reactors. The first configuration considered is a channel reactor with aerators placed alongside one lateral wall, for which velocity measurements are available in literature. CFD results were in good agreement with experimental data, which proves that the model is sufficiently accurate and predictive. Accordingly, simulations and numerical residence time distribution tests were conducted for different aerator layouts to determine their effects on the reactor hydrodynamics. The results revealed that the flow characteristics are extremely sensitive to the aerators arrangement given the high gas flow rates used in AS processes. Among the layouts investigated, the one where diffusers are placed all over the reactor floor has led to the least dispersive flow, i.e. which characteristics best tend toward that of an ideal plug flow reactor. Indeed, this flow field presented the lowest average turbulent diffusion and the most uniform axial velocity and turbulence fields. Such a flow behaviour is expected to be highly beneficial for biological treatment since it reduces pollutant dilution by axial diffusion and limits raw wastewater channelling to the outlet.

Ionic Liquid as a Selective Capture Method of CO2 from Different Sources: Comparison with MEA

Ionic liquids (ILs) have received growing consideration as a prospective decarbonization solvent. Nevertheless, most studies have focused on flue gases with specific compositions and flow rates, which makes it a challenging task to use ILs with divergent CO2 emission scenarios for the comprehensive carbon management. In this work, complete conceptual designs for absorption processes 1-butyl-3-methylimidazolium acetate ([bmim][Ac]) are developed for separating at least 90% of CO2 from the feed before pressurizing it to 150 bar to the sequestration sites over a broad range of CO2 flue gas compositions and flow rates. Each scenario is rigorously modeled, simulated, optimized, heat integrated, and compared with the conventional process by MEA. The simulation results show that compared to conventional processes, IL-based processes are only quite economical at high flue gas flow rates and CO2 contents. Also, a quantitative method toward technology comparison and scaling up is presented, which helps in selecting...

Gas–liquid mixing in dual agitated vessels in the heterogeneous regime

Gas–liquid multi-phase processes are widely used for reactions such as oxidation and hydrogenation. There is a trend for such processes to increase the productivity of the reactions, one method of which is to increase the gas flow rate into the vessel. This means that it is important to understand how these reactors perform as high gas flow rates occurs well into the heterogeneous regime. This paper investigates the mixing performance for the dual axial radial agitated vessel of 0.61m in diameter. 6 blade disk turbine (Rushton turbine) below a 6 Mixed flow Up-pumping and down-pumping have been studied at very high superficial gas velocities to understand the flow regimes operating at industrial conditions. Electrical resistance tomography have been used to produce the 3D images using Matlab, along with analysing the mixing parameters such as Power characteristics, gas hold-up and dynamic gas disengagement. Minimal difference between the two configurations have been reported in terms of gas hold-up, however with the choice of upward and downward pumping impeller power characteristics show significant difference at very high gas flow rates. Also at these high superficial gas velocities, this report introduces a 3rd bubble class, as seen in dynamic gas disengagement experiments, which corresponds to very large slugs of gas.

Energy analysis and optimization of hollow fiber membrane contactors for recovery of dissolve methane from anaerobic membrane bioreactor effluent

This work presents an energy analysis and optimization of the hollow fiber membrane contactors for the recovery of dissolved methane (CH4) in effluents of anaerobic membrane bioreactor wastewater treatment processes. The obtained CH4 could be merged with biogas for further purification or used with a micro-turbine for electricity generation to achieve an energy self-sufficient wastewater treatment process. A mathematical model considering simultaneous CH4 and carbon dioxide (CO2) desorption was used to estimate the membrane area required to remove the dissolved CH4, as well as quality of the outlet gas from the membrane contactor. Energy balance between electrical energy obtained from the recovered CH4 and energies consumed by vacuum and liquid pumps for the operation of membrane contactor were investigated and reported as a Net Electricity obtained per m3 of effluent or simply Net E. Results revealed that a combination of a high strip gas flow rate and slightly low vacuum condition closed to the atmospheric pressure can provide the highest Net E at 0.178 MJ/m3. This value is 85.37% of the total electrical energy that can generated from a 90% recovery of dissolved CH4 using an effluent saturated with a 60 vol% CH4 biogas and flow rate at 2 m3/day. The calculation was made based on the assumptions that 1) the membrane contactor is operated in a non-wetting mode where membrane properties remain constant, 2) flux decline due to the membrane fouling is not considered and 3) the energy required for membrane cleaning and other relevant activities are not factored into the energy analysis. Based on our results, to obtain a high CH4 mole fraction at the gas outlet, a low strip gas flow rate is recommended, however, the operating gas pressure needs to be lowered by applying a vacuum condition to improve the Net E. In addition, it was found that the Net E could be improved by increasing the number of membrane fibers, and lowering the liquid flow rate. The CH4 recovery efficiency could also be optimized to obtain an optimal Net E.

Towards Biochar and Hydrochar Engineering—Influence of Process Conditions on Surface Physical and Chemical Properties, Thermal Stability, Nutrient Availability, Toxicity and Wettability

The impact of conversion process parameters in pyrolysis (maximum temperature, inert gas flow rate) and hydrothermal carbonization (maximum temperature, residence time and post-washing) on biochar and hydrochar properties is investigated. Pine wood (PW) and corn digestate (CD), with low and high inorganic species content respectively, are used as feedstock. CD biochars show lower H/C ratios, thermal recalcitrance and total specific surface area than PW biochars, but higher mesoporosity. CD and PW biochars present higher naphthalene and phenanthrene contents, respectively, which may indicate different reaction pathways. High temperatures (>500 °C) lead to lower PAH (polycyclic aromatic hydrocarbons) content (<12 mg/kg) and higher specific surface area. With increasing process severity the biochars carbon content is also enhanced, as well as the thermal stability. High inert gas flow rates increase the microporosity and wettability of biochars. In hydrochars the high inorganic content favor decarboxylation over dehydration reactions. Hydrochars show mainly mesoporosity, with a higher pore volume but generally lower specific surface area than biochars. Biochars present negligible availability of NO 3 − and NH 4 + , irrespective of the nitrogen content of the feedstock. For hydrochars, a potential increase in availability of NO 3 − , NH 4 + , PO 4 3 − , and K + with respect to the feedstock is possible. The results from this work can be applied to “engineer” appropriate biochars with respect to soil demands and certification requirements.

Process simulation and thermodynamic evaluation for chemical looping air separation using fluidized bed reactors

Chemical looping air separation (CLAS) is considered as a promising method for providing an efficient and economic oxygen supply for integration into oxy-fuel combustion power plants. This study is the first to develop a process model, identify the process characteristics, and optimize the thermodynamic behavior for CLAS processes using fluidized bed reactors. In the process developed model, a fast fluidized bed model and a bubbling fluidized bed model are used to respectively represent the oxidation reactor and the reduction reactor, while fluidized bed hydrodynamics and oxygen carrier redox reaction kinetics are considered to grasp the unique characteristics of CLAS process. The effects of operating parameters on CLAS operation are identified and observed that high reduction temperature and high fluidizing gas flow rate can enhance oxygen carrier conversion and reduce energy penalty in the reduction reactor. Multi-variable optimization to minimize specified energy consumption illustrates that, 38.1% energy savings can be achieved and the optimal oxidation operating temperature, reduction operating temperature, air flow rate, and fluidizing gas flow rate are determined as 830 °C, 950 °C, 1133.7 L/h, and 58.4 L/h, respectively. These results are valuable for use by engineers to optimize the process design and achieve energy-efficient operation for CLAS processes.

Effects of nano-pore wall confinements on rarefied gas dynamics in organic rich shale reservoirs

The advancements in horizontal well drilling and multistage hydraulic fracturing technology enabled us to unfold major sources of hydrocarbon trapped in ultra-tight formations such as organic rich shales. Tremendous gas production from these reservoirs has transformed today’s energy landscape [1]. Even though multi-stage hydraulic fracturing stimulation provides high permeability paths to transfer gas to the wellbore, however, most of the gas is stored in nano-organic pores of the ultra-low permeability shale matrix that needs to be transferred to the hydraulic fractures to be able to be produced. Studies using advanced imaging technologies such as FIB/SEM and low temperature adsorption measurements show that in the organic rich shale gas reservoirs, Kerogen, the finely dispersed organic nano-porous material with an average pore size of less than 10 nm holds bulk of the total gas in place (GIP). The molecular level interactions between fluid–fluid and fluid–solid organic pore walls govern the transport and storage in these organic nano-pores.To understand the high gas production rates from these ultra-tight formations, the objective of this study is to advance our understanding of non-ideal gas dynamics in multiscale pore structure of organic rich shale matrix (i.e., gas storage and transport influenced by adsorption and adsorbed gas transport) and develop a model to quantify these effects under wide range of reservoir conditions. Among different methods used to model gas dynamics in organic nano-pores such as the multi-continuum, molecular dynamics and Monte Carlo, the lattice Boltzmann method (LBM) is more effective method with much less computational cost relative to other techniques. In this study we focus on rarefied gas dynamics in Kerogen organic nano-tubes under wide range of reservoir pressure and temperature conditions using a two dimensional LBM model.In this model the Langmuir-slip boundary condition at capillary walls, convection or darcy flow and diffusive transport (slippage of free gas molecules and surface transport of adsorbed molecules combined) are considered to model gas transport. Different transport mechanisms and their contribution in gas transport is investigated in a large range of Knudsen numbers from continuum flow to transition flow regime under different reservoir conditions. The deviation from classical theory of fluid flow in micro channels such as Knudsen’s minimum in the mass flow rate is investigated and the effect of gas slippage and double slippage on Knudsen minimum is discussed in details. Finally the results are compared with analytical, and semi analytical solutions available in the literature.The LBM model results displays a clear indication that the gas transport in the capillary tube is highly depends on the pore width size, pressure and temperature. The relative impact of pore size, pressure and temperature on maximum gas velocity and gas wall velocity differs at different flow regime conditions. A critical Knudsen number exists at different reservoir conditions, where the anticipated parabolic fluid velocity profile in organic nano-pores alters and shows higher flow rate as capillary widths reduces due to the underlying effect of molecular phenomena of double slippage and the wall confinement. The comparison with traditional continuum Hagen-Poiseuille law, Klinkenberg slip theory, and recent modified versions of Klinkenberg slip flow equations show that the previous models are valid only in the continuum flow regime, however, they fail to capture high gas flow rates at high Knudsen number and transition flow regimes which is the case in most of the shale organic nano-pore conditions [2].This work is not only important for the advancement of shale gas flow simulators, but also for organic rich shale characterization.

Characteristic Time Constants Derived From the Low-Frequency Arc of Impedance Spectra of Fuel Cell Stacks

Electrochemical impedance spectroscopy is used during operation of different polymer electrolyte membrane fuel cell (PEMFC) stack assemblies at various conditions with special interest given to the characteristic time constant τlow-f derived from the low-frequency arc of the spectra which is typically in the range of approximately 15–0.5 Hz. This was done by fitting an equivalent electrical circuit (EEC) consisting of one resistor and two RC-elements to the data. Parameter variation performed on a 90-cell stack assembly suggests that conditions leading to different air flow velocities in the flow channels affect τlow-f while other parameters like humidity influence the impedance spectrum, but not τlow-f. Comparison of the stoichiometry variation between short stack and locally resolved single cell shows similar results with the stack's time constant matching that of the cell's segments which are located off-center toward the outlet. However, a nonlinear dependency between gas flow velocity and τlow-f especially at low stoichiometric values is obvious. Results from stoichiometry variations at different pressure levels suggest that this could be attributed to the different steady-state oxygen partial pressures during the experiments. Comparison of the stoichiometry variation between different stack platforms result in similar dependencies of τlow-f on air flow rate with respect to a reference oxygen partial pressure regardless of size, flow field, geometry, or cell count of the stack. The time constant caused by oxygen diffusion through the gas diffusion layer (GDL), τGDL, was approximated and compared to τlow-f. While it was found that τlow-f ≫ τGDL at low stoichiometric values, τlow-f decreases toward τGDL at very high gas flow rates, suggesting that τGDL offsets τlow-f and becomes dominating if no oxygen concentration variation along the flow channel was present.

A model for the thin film friction factor in near-horizontal stratified-annular transition two-phase low liquid loading flow

For relatively large diameter pipes and at high gas flow rates, low-liquid loading near-horizontal two-phase flows presents a thin liquid film flowing at the upper part of the pipe wall while a stratified liquid film is observed at the bottom. This paper presents a new model that takes the thin film into account for pressure gradient calculations. The model evaluates the thin film thickness based on the Nusselt falling film theory coupled with a liquid mass balance in the cross sectional area of the pipe. This coupling relates the rate of deposited droplets at the thin film with the atomization and deposition at the bottom liquid film. The thin film thickness is used in an equation that corrects the gas-wall friction factor. The model is evaluated against existing data acquired at larger diameters and higher pressures improving the pressure gradient prediction at higher gas flow rates.

Hydrogen production from coal-derived syngas undergoing high-temperature water gas shift reaction in a membrane reactor

In this study, a numerical model to predict the hydrogen production from water-gas shift reaction using coal-derived syngas as a feedstock was presented. The reaction was carried out in a palladium (Pd)-based membrane reactor operated at 900°C for yielding carbon monoxide (CO) conversion higher than the thermodynamic equilibrium limit. The sweep gas flow, membrane permeance, and steam-to-carbon ratio effects on the reactor performance were examined. Based on the obtained results, it was found that high CO conversion and hydrogen (H2) recovery were obtained when the reactor was operated in counter-flow mode and with high sweep gas flow rate, steam-to-carbon ratio, and membrane permeance. However, the H2S-to-H2 ratio in the reactor was found to increase with the CO conversion and can be higher than the thermodynamic limit for Pd sulfidization. Optimum operation parameters should be sought for obtaining high CO conversion and H2 recovery while preventing membrane failure due to Pd sulfidization.

Foaming of industrial lean methyldiethanolamine solution in the presence of hydrocarbon and fatty acid based corrosion inhibitors

In natural gas sweetening alkanolamine processes one of the regularly used chemical is the corrosion inhibitor. For better operation of the plant it is essential to understand the effect of their presence on foaming of industrial lean Methyldiethanolamine (MDEA) used as solvents at different temperatures. This study aimed at investigating the effect of HydroCarbon Based (HCB) and fatty acid based corrosion inhibitor having chemical name Bis(2-Hydroxyethyl)Cocoalkylamine (BHCL) on the foaming tendency of industrial real lean MDEA solutions. Experiments were conducted with different operating parameters, including liquid volume of the solution, foaming time, flow rate of nitrogen gas, concentration of the corrosion inhibitors, temperature of the solution, and gas diffuser pore size using the Foam Scan instrument. With the increase in solution volume and foaming time foaming happens to be more. The foaming tendency of lean MDEA solutions decreased with increasing temperature in absence of corrosion inhibitors but showed different behavior in their presence. At small diffuser pore size and high gas flow rate, the final foam volume increased in the presence of HCB but decreased with the BHCL inhibitor. Optimizing the operating parameters to minimize foaming was verified to be a function of the type of inhibitor used.

Flue gas carbon capture using hollow fiber membrane diffuser-separator

In this work, CO2 removal from flue gas using membrane diffuser–separator was investigated. Hollow fiber polypropylene membrane was used as the diffuser while pure water was used as the absorbent. Separation performance of the membrane diffuser–separator as a function of CO2 concentration (6-28%-vol.) and flow rate (gas: 0.8-1.55 L.min-1 and liquid: 0.2-0.7 L.min-1) was investigated and optimized. It was found that CO2 removal was significantly affected by CO2 concentration in the feed gas. On the other hand, CO2 flux was more influenced by flow rates of liquid and gas rather than concentration. The optimized CO2 removal (64%) and flux (1 x 10-4 mol.m-2.s-1) were obtained at the highest gas flow rate (1.55 L.min-1), the lowest liquid flow rate (0.2 L.min-1), and 6.2%-vol. of CO2 concentration. Outlet gas of the membrane diffuser system tends to carry some water vapor, which is affected by gas and liquid flow rate. Meanwhile, in the steady-state operation of the separator, the gas bubbles generated by the membrane diffuser take a long time to be completely degassed from the liquid phase, thus a portion of gas stream was exiting separator through liquid outlet.

Cross-flow structured packing for the process intensification of post-combustion carbon dioxide capture

We introduce novel insights into a cross-flow arrangement of structured packings specifically for post-combustion carbon dioxide capture. Gas-liquid dynamics are investigated numerically, with the liquid flowing under the action of the gravity and the gas driven by a horizontal pressure gradient crossing the liquid phase. An elementary packing cell consists of two connected channels: one depicting a co-current gas-liquid flow and the other depicting a counter-current two-phase flow. While flow reversal of the liquid phase can occur in the counter-flow channel at high gas flow rates, the overall flooding point is significantly delayed in comparison to a counter-current flow arrangement traditionally used for structured packings. Varying the gas flow rate and the tilting angle of the elementary cell, a detailed numerical analysis of the flow repartition between channels, the pressure drop, the gas and liquid velocities, and the onset of flooding is presented. The pressure drop is found to be smaller when tilting the cell with respect to the initial scenario at 45°. Flow reversal instead is delayed when lowering the tilting angle, that is when the cell is tilted anti-clockwise. We also reveal the presence of long waves at the edge of the cell at low tilting angles. Finally, data of the wet pressure drop in the cross-flow cell are compared with different commercially available types of packing arranged in a conventional vertical counter-flow configuration, such as several versions of the Sulzer Mellapak™.

Multiphysics simulation of algal growth in an airlift photobioreactor: Effects of fluid mixing and shear stress

A multiphysics model has been developed to predict the effects of fluid mixing and shear stress on microalgal growth in an airlift photobioreactor. The model integrates multiphase flow dynamics, radiation transport, shear stress, and algal growth kinetics using an Eulerian approach. The model is first validated by comparing its predictions with experimental data, and then the radiation transport and algal growth kinetics submodels are added to predict biomass accumulation under different flow conditions. The simulations correctly predict biomass growth curves for a wide range of superficial gas flow rates and demonstrate that biomass productivity increases with increased gas flow rate due to better light delivery to microorganisms. However, at the higher gas flow rates considered, shear stress on microorganisms inhibits biomass growth. Lastly, it is shown that the Eulerian approach used here provides a less cumbersome computational approach and provides better predictions than the circulation time and Lagrangian approaches.

Experimental Investigations of a Pilot Scale Coal Impinging Stream Dryer

ABSTRACT A method for drying hard coals using an impinging stream dryer has been proposed in the article. A series of screening tests were conducted, seeking optimum process parameters of an innovative coal impinging stream dryer using flue gas as the drying medium. The article addresses measurement results obtained for the flue gas and feedstock flow rate, feedstock sort, and initial moisture content on the specific energy consumption, volumetric water evaporation rate, and moisture reduction. The maximum volumetric water evaporation rate was found to be around 230 kgwater/m3·h and the maximum volumetric heat transfer coefficient came to ca. 2.5 kW/m3·°C. In terms of specific energy consumption, the lowest specific energy consumption was found to be around 1.79 kWh/kgwater. It was established that the relation between specific energy consumption and a product of the flue gas flow rate and the initial water (in the feedstock) flow rate is a power function. The best performance of the impinging stream dryer was achieved for high-moisture coal and high flue gas flow rates. The impinging stream dryer proved to be suitable for surface moisture removal from particulate materials that contain very high moisture. The initial tests conducted at the pilot plant successfully demonstrated reliable operation and promising results.

Multiscale Modeling of a Packed Bed Chemical Looping Reforming (PBCLR) Reactor

Packed bed reactors are broadly used in industry and are under consideration for novel reactor concepts such as packed bed chemical looping reforming (PBCLR). Mass and heat transfer limitations in and around the particles in packed bed reactors strongly affect the behavior of these units. This study employs a multiscale modeling methodology to simulate a PBCLR reactor. Specifically, small-scale particle-resolved direct numerical simulation is utilized to improve large-scale mass transfer models for use in an industrial scale 1D model. Existing intra-particle mass transfer models perform well for simple first order reactions, but several model enhancements were required to model the more complex steam methane reforming reaction system. Three specific aspects required enhanced modeling: the generation of additional gas volume by the reforming reactions, the lack of clear reaction orders in the equilibrium reactions, and the diffusion of multiple reactant species into the particle. Large-scale simulations of the PBCLR reactor with the enhanced 1D model showed that the highly reactive Ni-based catalyst/oxygen carrier employed allows for the use of large particle sizes and high gas flowrates, offering potential for process intensification.

Trickle bed applied to the post‐treatment of blast furnace dust

AbstractThis study aims to develop an original filtration device based on a trickle bed technology which permits to treat high gas flow rates while maintaining a constant pressure drop by re‐entraining continuously the particles trapped on collectors, thanks to a water film flow. Good results have been obtained for an air flow rate of 20 m3/hr, a liquid flow rate of 12 L/min and using glass beads of 5‐mm diameter as collectors. Experimental results showed a good mass efficiency (89%) and a pressure drop which stabilizes under clogging unlike that of a granular bed which increases during the clogging. The experiments certifying a stable pressure drop during a few tens of hours let us suppose that these tendencies should be extrapolated to much larger times.

Large-Scale Exploitation of Bimodal Reaction Sequences Including Degradation: Comparison of Jet Loop and Trickle Bed Reactors

Product yield optimization in bimodal reaction sequences including degradation has been performed considering three-phase reactors such as the jet loop and trickle bed reactors. The considered reaction network comprises two consecutive homogeneous reaction steps toward intermediates which are converted to the corresponding final products by heterogeneously catalyzed reactions, while the reactant and these intermediates are susceptible to irreversible degradation. In the jet loop reactor, the so-called “homogeneous product” is the main product; hence, the remaining challenge is the reduction of degradation. For the trickle bed reactor, gas–liquid mass phase transfer plays a very pronounced role in its ultimate performance. Higher gas flow rates may be employed in the trickle bed reactor to overcome potential mass-transfer limitations and selectively form the “heterogeneous product”. Lower gas flow rates result in a less effective gas dissolution, and product selectivities change toward the homogeneous prod...