Trickle Bed Research Articles

High Purity Hydrogen with Sorption-Enhanced Steam Methane Reforming in a Gas–Solid Trickle Bed Reactor

A sorption enhanced-steam methane reforming (SE-SMR) process was investigated in a countercurrent gas–solid trickle flow reactor packed with regularly stacked catalyst. The stacked catalyst was made of corrugated Pt/Ni/Al2O3 plates in the form of static mixers. Experiments were carried out in a temperature range of 550–600 °C, total pressure of 4.0 bar, and water to methane ratio of 4.0 in the reactor feed. Within the investigated conditions, experimental results offered a solid proof of concept for new continuous SE-SMR operation for production of hydrogen where sorbent can be regenerated separately from the catalyst. Experimental data were reasonably well described by a plug flow model for both the gas and solid phases. The mathematical model was further used to optimize the continuous SE-SMR operation: it could be demonstrated that the level of the hydrogen purity in the reactor exit stream could be controlled by a multistage reactor consisting of alternating catalytic active and stainless-steel inert ...

Prevention of melanin formation during aryl alcohol oxidase production under growth-limited conditions using an Aspergillus nidulans cell factory

An Aspergillus nidulans cell factory was genetically engineered to produce an aryl alcohol oxidase (AAO). The cell factory initiated production of melanin when growth-limited conditions were established using stationary plates and shaken flasks. This phenomenon was more pronounced when the strain was cultured in a trickle bed reactor (TBR). This study investigated different approaches to reduce melanin formation in fungal mycelia and liquid medium in order to increase the enzyme production yield. Removal of copper from the medium recipe reduced melanin formation in agar cultures and increased enzyme activities by 48% in agitated liquid cultures. Copper has been reported as a key element for tyrosinase, an enzyme responsible for melanin production. Ascorbic acid (0.44g/L) stopped melanin accumulation, did not affect growth parameters and resulted in AAO activity that was more than two-fold greater than a control treatment with no ascorbic acid.

Performance evaluation of process tomography system for cold flow catalytic column

In a typical catalytic trickle bed type of process reactor, capturing representations of steady-state flow features as well as situations like channelling or bypassing is a challenging task. Transmission-type industrial process tomography (PT) based on gamma radiation can be employed in many chemical and process industries as a tool for localizing the problem area for quick and economical troubleshooting. Industrial PT technology often makes use of either penetrating radiation like radioisotope based gamma rays, X-rays, microwaves or ultrasonic waves. We have developed a new gamma-ray transmission tomography system in collaboration with the Indian Oil Corporation Ltd. (IOCL R&D Unit, Faridabad, India). The system makes use of thirty two scintillator based gamma-ray detectors in addition to a host of other sub-systems. This paper evaluates the performance of the system considering systematic and automated data acquisition, capabilities of the reconstruction software as well as experimental verification using actual flow dynamics in the process column to map the steady state three phase liquid gas flow distribution across a plane in the presence of catalyst.

Quantifying the dominant factors in Cu catalyst deactivation during glycerol hydrogenolysis

Abstract Long term stability of a commercial Cu-based glycerol hydrogenolysis catalyst has been studied in an isothermal trickle-bed reactor at 473–503 K in the presence of impurities, such as S, Cl and glycerides. While glycerides have the least effect on the catalytic activity, the increase in the extent of deactivation with temperature as a consequence of thiophene indicates a kinetic rather than a thermodynamic adsorption effect. The threshold driven, ‘sudden’ manner in which deactivation manifests itself in case of Cl is indicative of sintering. A deactivation model accounting for the activity loss with changing concentration of impurities and temperature, was constructed.

Prediction of the Effects of the Inlet Velocity and the Reactor Length on the Performance of a Trickle-Bed Reactor for Renewable Diesel Production

Prediction of the Effects of the Inlet Velocity and the Reactor Length on the Performance of a Trickle-Bed Reactor for Renewable Diesel Production

Fluid dynamics and reaction assessment of diesel oil hydrotreating reactors via CFD

In this work, computational fluid dynamics (CFD) has been used to investigate diesel hydrotreating (Hydrodesulfurization (HDS) and Hydrodearomatization (HDA)) in a laboratory scale trickle bed reactor (TBR). In order to investigate these reactions, the 3D model was developed using a multi-phase Eulerian-Eulerian approach, an inter-phase interaction model, a porosity distribution model for the trilobe particles, mass transfer and chemical reactions model. Due to the small dimensions of the reactor, the simulations are carried out at isothermal and transient conditions and the catalyst bed is considered to be fully wetted. In this first phase of the work, a reaction model was used, which was later validated. Then, a counter-current reactor is simulated and the results are compared with a co-current reactor. The analyzed parameters are conversion, pressure drop and liquid holdup and a special attention was given in order to verify how operational changes on pressure, temperature, velocity and gas and liquid flows influence the reactor performance. The influence of porosity on fluid velocity and volume fraction of liquid is also investigated. Finally, the influence of the liquid hourly space velocity (LHSV), temperature, gas-liquid ratio and partial pressure of H2S are also discussed. The results for the two types of reactors are similar despite the fact that the counter-current arrangement has achieved lower conversions.

Continuous Ethanol Production from Synthesis Gas by Clostridium ragsdalei in a Trickle-Bed Reactor

A trickle-bed reactor (TBR) when operated in a trickle flow regime reduces liquid resistance to mass transfer because a very thin liquid film is in contact with the gas phase and results in improved gas–liquid mass transfer compared to continuous stirred tank reactors (CSTRs). In the present study, continuous syngas fermentation was performed in a 1-L TBR for ethanol production by Clostridium ragsdalei. The effects of dilution and gas flow rates on product formation, productivity, gas uptakes and conversion efficiencies were examined. Results showed that CO and H2 conversion efficiencies reached over 90% when the gas flow rate was maintained between 1.5 and 2.8 standard cubic centimeters per minute (sccm) at a dilution rate of 0.009 h−1. A 4:1 molar ratio of ethanol to acetic acid was achieved in co-current continuous mode with both gas and liquid entered the TBR at the top and exited from the bottom at dilution rates of 0.009 and 0.012 h−1, and gas flow rates from 10.1 to 12.2 sccm and 15.9 to 18.9 sccm, respectively.

Simulation of the catalyzed isotopic exchange between hydrogen and water in a trickle bed reactor

The catalytic exchange column of countercurrent trickle bed for deuterium removal from hydrogen is simulated based on experimental results along with established reaction and mass transfer models, accounting for the humidification of hydrogen in a catalyst bed filled with platinum/styrene-divinylbenzene copolymer pellets and Dixon rings. Relative deviations of less than 30% are achieved between the experimental and the simulated HD molar fractions at the column outlet. Simulation results indicate that hydrogen humidification exerts a noticeable influence on gas and liquid phase flow rates, leading to an overestimated removal percentage of deuterium when such flow rate variances are neglected. Rate limiting step for the overall gas-liquid isotopic exchange is discussed. Finally, the operation conditions are optimized using the developed model.

Biodegradation of endocrine disruptors in urban wastewater using Pleurotus ostreatus bioreactor

The white rot fungus Pleurotus ostreatus HK 35, which is also an edible industrial mushroom commonly cultivated in farms, was tested in the degradation of typical representatives of endocrine disrupters (EDCs; bisphenol A, estrone, 17β-estradiol, estriol, 17α-ethinylestradiol, triclosan and 4-n-nonylphenol); its degradation efficiency under model laboratory conditions was greater than 90% within 12 days and better than that of another published strain P. ostreatus 3004. A spent mushroom substrate from a local farm was tested for its applicability in various batch and trickle-bed reactors in degrading EDCs in model fortified and real communal wastewater. The reactors were tested under various regimes including a pilot-scale trickle-bed reactor, which was finally tested at a wastewater treatment plant. The result revealed that the spent substrate is an efficient biodegradation agent, where the fungus was usually able to remove about 95% of EDCs together with suppression of the estrogenic activity of the sample. The results showed the fungus was able to operate in the presence of bacterial microflora in wastewater without any substantial negative effects on the degradation abilities. Finally, a pilot-scale trickle-bed reactor was installed in a wastewater treatment plant and successfully operated for 10days, where the bioreactor was able to remove more than 76% of EDCs present in the wastewater.

Hydrodynamics of descending gas-liquid flows in solid foams: Liquid holdup, multiphase pressure drop and radial dispersion

In this contribution we report on spatially resolved analysis of multiphase hydrodynamics in solid foam packed trickle bed reactors. For the investigation we used ultrafast X-ray computed tomography and fast response pressure transducers. The SiSiC foams’ pore density, the liquid distribution system as well as gas and liquid flow rates were varied. The transient behavior of the liquid holdup at trickle and pulse flow as well as after drainage were examined and correlations for static and dynamic holdups were derived. The correlations are based on Eötvös, Reynolds and Galileo number, using porosity and specific area for the definition of the hydraulic diameter. The correlations are applicable to a wide range of foam morphologies, pore densities and operating conditions reported in the literature. The axial pressure gradients in the solid foams showed significantly lower pressure drop compared to particle packings of similar specific surface area. The evolution of liquid spreading was analyzed qualitatively and quantitatively with various irrigation patterns. In addition, an approach for the determination of radial liquid dispersion coefficients in solid foams is presented.

Continuous Selective Hydrogenation of Refametinib Iodo-nitroaniline Key Intermediate DIM-NA over Raney Cobalt Catalyst at kg/day Scale with Online UV–Visible Conversion Control

The continuous selective hydrogenation of the iodo-nitroaromatic refametinib active pharmaceutical ingredient (API) intermediate (2,3-difluoro-5-methoxy-6-nitro-phenyl)-(2-fluoro-4-iodo-phenyl)-amine (DIM-NA) to the corresponding iodo-aniline 3,4-difluoro-N2-(2-fluoro-4-iodo-phenyl)-6-methoxy-benzene-1,2-diamine (DIM-DAB) was investigated using a conventional Raney cobalt catalyst in a cocurrent trickle-bed reactor. Suitable reaction conditions targeting full conversion and high selectivity, that is, low degrees of hydro-dehalogenation of the labile iodine substituent, were evaluated in investigations employing a short 4 mL screening reactor. The process was then transferred to a longer 40 mL reactor. Raney cobalt was found to be a highly selective catalyst, yielding only very small amounts of the desiodinated aniline desiodo-DIM-DAB or other side products. Productivities up to 144 g/h crude DIM-DAB were achieved operating the 40 mL reactor with a 0.2 M reactant solution in the presence of 3.4 equiv of H2 at 60 °C. Inlet pressure resulting from the flow rate increase was identified as a key parameter for successful throughput maximization. One kilogram of starting material was eventually converted to DIM-DAB in high yield and excellent quality within 8 h runtime. Online monitoring of the UV–vis absorption of the product stream allowed for conversion control and fast detection of process variations. Compared to the available DIM-NA batch reduction procedures, processing in continuous flow proves convincing by the safe implementation and reusability of the Raney type catalyst within a strongly intensified and highly selective process.

Numerical Modelling and Simulation of Gas-Liquid Trickle Flow in Trickle Bed Reactor Using an Improved Phenomenological Model

For the past many decades, fossil fuels remain the major sources to fulfil energy requirements worldwide. Crude oil is processed in oil-refineries where it is subjected to hydrotreating. The process of hydrotreating involves the passage of the gas-liquid mixture through catalyst-filled Trickle Bed Reactors (TBRs) which involves simultaneous reactions of hydrodesulphurization and hydrodenitrogenation. In order to determine the actual energy requirements and thereby increasing energy efficiency and reducing associated cost, it is essential to have good understanding of dynamics of three-phase flow in trickle bed reactors. Correct estimation of pressure drop across the reactor height and contact efficiency of the system at different gas/liquids at different flow rates play a major role in the design of energy efficient trickle bed reactors. In this work a new phenomenological pore scale hydrodynamic model is proposed to predict pressure drop and liquid holdup in uniform and steady gas-liquid flow in a trickle bed reactor. Numerical analysis of already existing hydrodynamic models was performed and by inclusion of liquid film tortuosity in the flow, pressure drop and liquid holdup were estimated using the newly proposed numerical model. The flow simulations were performed in commercial software FLUENT using a three-phase Eulerian model. The numerical model was based on a robust 1D geometry which resulted in reduction of computation time. The model was validated against experiments reported in the literature. The obtained computational were also compared with other available models and showed good prediction for pressure drop and liquid holdup.

Catalytic Nitrate Removal in a Trickle Bed Reactor: Direct Drinking Water Treatment

Palladium (Pd)‐based catalysts hold promise as an alternative water treatment technology for nitrate (NO3), but practical application requires a flow‐through reactor that efficiently delivers hydrogen (H2) from gas to water. A trickle bed reactor (TBR) packed with a 0.1 percent by weight (wt%) Pd–0.01 wt% In/γ‐Al2O3 (indium and porous aluminum oxide) catalyst was evaluated to address this challenge. Catalytic activity generally increased with H2 superficial velocity (0.65–29.6 m/h) and liquid (deionized water) superficial velocities from 14.8 to 26.6 m/h before decreasing at 38.5 m/h. This decrease corresponded to a change in flow regime and suggests that optimal TBR performance occurs at the transition from pulse to bubble flow. An optimal TBR activity of 19.5 ± 1.3 mg NO3/min‐g Pd was obtained; this is only ~18% of the batch reactor activity as a result of H2 mass transfer limitations, but three to 15 times greater than activities obtained with previous flow‐through reactors. Catalyst deactivation occurred in the TBR after 41 days of operation, motivating the need for improved fouling mitigation strategies.

Catalytic Denitrification in a Trickle Bed Reactor: Ion Exchange Waste Brine Treatment

Catalytic reduction of nitrate in ion exchange (IX) waste brine for reuse is a promising option for reducing IX costs and environmental impacts. A recycling trickle bed reactor (TBR) was designed and optimized using 0.5 percent by weight (wt%) palladium–0.05 wt% indium catalysts supported on US mesh size 12 × 14 or 12 × 30 activated carbon particles. Various liquid superficial velocities (Ur) and hydrogen gas superficial velocities (Ug‐H2) were evaluated to assess performance in different flow regimes; catalyst activity increased with Ug‐H2 at all Ur for both catalysts and was greatest for the 12 × 30 catalyst at the lowest Ur (8.9 m/h). The 12 × 30 catalyst demonstrated up to 100% higher catalytic activity and 280% higher mass transfer rate compared with the 12 × 14 catalyst. Optimal TBR performance was achieved with both catalysts in the trickle flow regime. The results indicate that the TBR is a promising step forward, and continued improvements are possible to overcome remaining mass transfer limitations.

Investigation on Asphaltenes Structures during Low Temperature Coal Tar Hydrotreatment under Various Reaction Temperatures

In order to convert low temperature coal tar (LCT) into clean transportation fuels by hydrotreating (HDT), the changes of asphaltenes properties during HDT of LCT should be paid more attention. The HDT experiments were carried out in a trickle-bed reactor unit under various reaction temperatures, and asphaltenes were extracted from the liquid products. The properties and structure of asphaltenes were performed by X-ray diffraction, elemental analysis, size-exclusion chromatography, X-ray photoelectron spectroscopy, and nuclear magnetic resonance. Structural units analysis of average molecules and the variation trend of change in the structural parameters were revealed. The results showed that, with the temperature increase, the diameter of the aromatic sheet (La), interaromatic layer distance (dm), total carbon number (CT), and average alkyl chain length (n) decrease, while the aromaticity factor (fA) and aromatic carbon number (CA) increase. Moreover, the mechanism of HDT was studied to make the molecula...

Prediction of thermal behavior of trickle bed reactors: The effect of the pellet shape and size

Heat transfer plays an important role in several applications of packed bed reactors with cocurrent downflow of liquid and gas (widely known as trickle-bed reactor – TBR).A literature survey shows that the amount of articles dealing with the prediction of heat transfer rates between a TBR and an external heating or cooling source is limited for spherical catalyst pellets and definitively scarce for other pellet shapes as cylinders and multilobes.Results from an experimental program devoted to study heat transfer between a TBR and an external jacket, employing spherical and cylindrical particles and a commercial trilobe pellet, are presented. A wide range of gas (air) and liquid (water) flow rates were covered corresponding to low and high interaction regime. A two dimensional pseudohomogeneous model was employed to represent the thermal behavior of the packed bed. Values of the effective radial thermal conductivity and the wall heat transfer coefficient were obtained by regression of radial temperature profiles for three different bed lengths. Finally, expressions to estimate both parameters for the different particle shapes were developed, thus providing a useful predictive tool, not available in the literature up to the best of our knowledge.

Characteristics of adapted hydrogenotrophic community during biomethanation

The results presented in this study were carried out as concomitant experiments during the start-up and operation of a biomethanation unit to evaluate the effect of process parameters on carbon conversion, product formation (methane and acetate) and community composition. For that, two different samples were withdrawn from a trickle-bed reactor with immobilized enrichment culture of hydrogenotrophic methanogens adapted from sewage sludge. One sample was taken from the recirculation liquid during start-up phase while the other was withdrawn directly from the carrier material in the reactor. Elevated acid levels especially during start-up were shown to affect the overall carbon conversion. This effect was also seen during the acid tolerance testing reported here. Final acid concentrations of 1.6±0.3g/L resulted in a reduced conversion ratio of only 46%. Without acid addition complete conversion of CO2 in the headspace was achieved. However, maximum methane production of 0.55±0.02mmol after 4days of incubation was monitored at moderate initial acetate concentration of 0.4g/L. In both analyzed inoculation materials Methanobacterium species were by far the most dominant Archaea with 21.8% in the recirculation liquid during start-up and 84.8% in the enrichment culture immobilized on the carrier material. The microbial composition of the two analyzed samples is in accordance with the results obtained for the carbon conversion and product formation. With approximately 50% of Bacteroidetes and Firmicutes present during reactor start-up the acetic acid production significantly contributed to the overall carbon conversion. In contrast, methane was produced almost exclusively in trials representing continuous operation where acetogenic bacteria accounted only up to 17.5%. In summary, the acid accumulation monitored during reactor start-up of a biomethanation unit is most likely to result from the microbial composition present. Nevertheless, complete adaptation to hydrogenotrophic conditions was proven to alter the consortium and yield methane as main product alongside high carbon conversion of up to 70.5±1.8%.

Study of the countercurrent–concurrent gas–liquid flow configuration impact on ethylene hydrogenation within structured catalyst bed: Experiment and modeling

Abstract In this paper catalytic hydrogenation of ethylene was studied using liquid propane with 1.5% of ethylene content and hydrogen gas in 30 barg trickle bed reactor under two flow configurations: countercurrent and concurrent. Trickle bed experiments were then performed using an experimental package comprising high pressure pilot reactor, gas chromatograph apparatus, dosing pump and required instrumentation system to compare countercurrent and concurrent sampled data furthermore structured catalyst of alumina–nickel was used as catalytic bed. Trickle bed modeling was achieved using a package of 12 dimensionless two-dimensional homogeneous mass and momentum transfer partial differential equations, the model parameters and kinetic equations. Orthogonal collocation technique was employed to solve developed PDEs. Predicted performance of the trickle bed by mathematical modeling was compared by experimental results and there was good consistency between them. The experimental results showed zero concentration of ethylene through countercurrent flow. Finally, the experimental analysis reports emphasize on zero concentration of ethylene in output of countercurrent bed whilst increasing the Reynolds number did not conclude to nil concentration of ethylene in output of concurrent bed.

Effect of reactor configuration on performance of vacuum gas oil (VGO) hydrotreater: Modelling studies

While kinetics is independent of either scale or configuration of hydrotreating reactor, hydrodynamics of reactor depend on both. The hydrodynamics of reactor which comprise of phase mass-transfer, catalyst wetting and pressure drop affect its performance significantly and should be addressed adequately while deciding on configuration or scale up issues. This study evaluates and compares the performance of different configurations of commercial VGO hydrotreater by employing mathematical model encompassing kinetics and hydrodynamics. Two configurations have been studied:•Conventional trickle-bed reactor, subdivided into (a) beds in parallel and (b) beds in series.•Pre-saturated one liquid flow (POLF) reactor, subdivided into (a) reactor with single pre-saturator (POLF-SP) and (b) multiple reactors in series with intermittent pre-saturators (POLF-MP).The performance of conventional reactor in series/parallel is found to be superior to POLF configurations. The inferior performance of POLF configurations is attributed to mixed flow behaviour due to recycle as against plug flow behaviour in conventional trickle-bed reactors.

Metal phosphide catalysts for the hydrotreatment of non-edible vegetable oils

Silica-supported catalysts of nickel, cobalt, iron, molybdenum, and tungsten metal phosphides (NiP/SiO2, CoP/SiO2, FeP/SiO2, MoP/SiO2, and WP/SiO2) with a metal-loading of 15wt%, were synthesized by reduction of the corresponding phosphite precursors. The catalysts were characterized by N2 adsorption–desorption, X-ray diffraction (XRD), CO pulse chemisorption, NH3 temperature programmed desorption (NH3-TPD), and X-ray photoelectron spectroscopy (XPS). The activity of these catalysts was measured at 573K, a liquid flow of 0.3mLmin−1, a pressure of 2.0MPa and a H2/liquid ratio of 300 in a three-phase, trickle-bed reactor in the hydrotreatment of methyl laurate. The MoP/SiO2 catalyst was found to exhibit the best catalytic performance based on its higher active phase dispersion as measured by XRD, CO chemisorption and XPS analyses, along with its moderate acidity, which is higher with respect to the other studied catalysts. The reaction conditions using the MoP/SiO2 catalyst, the most active and selective to C12 and C11 hydrocarbons, were optimized. Optimal results can be obtained under the following conditions: 573K, 2.0MPa, and a liquid flow of 0.3mLmin−1. Moreover, long-run experiments showed that the MoP/SiO2 catalyst exhibits stable catalytic behavior for at least 96h.