Trickle Bed Research Articles

Hydrodynamics of gas-liquid co-current flow through a thin sheet of highly porous open cell solid foam

An experimental study of the hydrodynamics of a gas-liquid co-current flow inside a thin sheet of Open Cell Solid Foam (OCSF) confined in a plate reactor is proposed. Image processing is used to quantify the flow patterns when varying the gas and liquid flow rates and buoyancy (horizontal and vertical upflow). The fraction of joint flow and interface motion areas, respectively εm and εi, are defined as relevant quantities to characterize the different flow regimes and phases interaction. Two distinct regimes are observed for the vertical flow: the low (LA) and high (HA) activity regimes characterized by a low or high phases interaction. In the horizontal configuration, an additional regime is observed and is called pseudo-trickling (PT) regime due to its similarity with the trickling regime observed in vertical downflow packed beds. The transition between LA and HA regimes is compared to the regime transition in trickle beds.

Continuous Conversion of Glucose into Methyl Lactate over the Sn-Beta Zeolite: Catalytic Performance and Activity Insight

In this study, we developed an efficient technology for the continuous conversion of glucose into methyl lactate over the Sn-Beta zeolite with a trickle bed reactor. The catalyst exhibited a high yield of 59.7% for lactic acid in water, and the total yield of methyl lactate and xylitol reached 59.8% (37.3% for methyl lactate) in methanol. The continuous evaluation of Sn-Beta demonstrated a maximum yield of 45.0% for methyl lactate along with 99% conversion of glucose in methanol, and the catalyst was continuously operated for over 434 h at 165 °C. The changes in Sn coordination and fouling stand as the dominant reason for the activity loss of Sn-Beta. Compared with the rapid decline of activity in water, reaction in methanol exhibited much less carbon deposition, structural changes, and Sn leaching after a long-term operation. The promising result indicated the potential application of Sn-Beta as an industrial catalyst for biomass utilization.

Biohydrogen from dilute side streams - Influence of reaction conditions on the conversion and selectivity in aqueous phase reforming of xylitol

Aqueous phase reforming (APR) can be used as an efficient method to purify and obtain added value from rather dilute side/waste streams of process waters containing e.g. alcohols or sugar alcohols. Such side streams often have none or even negative value due to purification costs, which contributes to the economy of the process. Xylitol was here used as a model compound. The desired product in the current study was hydrogen, which can be used for valorizing by-products via hydroprocessing or as a bioenergy source. In addition to hydrogen, some alkanes were also obtained, which are prime sources of bio-energy for power production. The current work focused especially on the influence of the reaction conditions (temperature, pressure and inert gas flow) on the xylitol conversion and hydrogen selectivity, which has not been reported previously. The influence of reaction conditions on the aqueous phase reforming of xylitol on Pt/Al2O3 catalyst was studied in a trickle-bed reactor. Selectivity to hydrogen was dependent on gas flow through the reactor, especially the absence of any gas resulted in a low selectivity. A higher reaction temperature and a higher inert gas flow gave a better xylitol conversion, while an increase of the overall pressure had an opposite effect on conversion. The activation energy for xylitol conversion was determined for the first time being 79.3 kJ/mol. The results demonstrate that aqueous phase reforming is a viable method for energy efficient value added processing of sugar alcohol containing dilute side streams in modern bio-refinery applications.

Design and Evaluation of a Co-Mo-Supported Nano Alumina Ultradeep Hydrodesulfurization Catalyst for Production of Environmentally Friendly Diesel Fuel in a Trickle Bed Reactor.

In the present work, a nanocatalyst, γ-Al2O3 nanoparticle-supported CoMo, was prepared experimentally and evaluated through a hydrodesulfurization (HDS) process for removing dibenzothiophene (DBT) from diesel fuel systematically in a trickle bed reactor (TBR). The results of the prepared catalyst characterization tests (scanning electron microscopy, X-ray diffraction (XRD), XRD phase quantification, and Brunner–Emmett–Teller) showed good distribution of active metals (CoMo), difference in surface morphology, and high dispersion of active metals. The catalyst exhibited good metal–support interactions without impacting the surface area significantly. A fully automated TBR reactor was used to evaluate the activity of the prepared catalyst in the HDS process at ranges of operating conditions: temperatures (250–350 °C), pressures (6–10 bar), liquid hourly space velocities (LHSV) (1–3 h–1), and the activity of the prepared catalyst were compared to a commercial catalyst based on Co–Mo/γ-alumina. The results showed an obvious enhancement in the HDS process using the homemade nanocatalyst compared to the commercial catalyst. It has also been found that an increase in temperature led to an increase in the conversion from 68.77 to 91.57%, a little positive effect on conversion when pressure was increased, and a significant decrease in conversion (from 91.57 to 75.58%) as LHSV was increased. A kinetic model was developed for the HDS process to estimate kinetic parameters and apply the parameters in reactor design. The developed model showed that the DBT concentration in diesel fuel can be reduced significantly, 3000–240 ppm, at the optimum experimental conditions.

Upgrading Siberian (Russia) crude oil by hydrodesulfurization in a slurry reactor: A kinetic study

Hydrodesulfurization (HDS) of sour crude oil is an effective way to address the corrosion problems in refineries, and is an economic way to process sour crude oil in an existing refinery built for sweet oil. In the current study, the HDS of Siberian crude oil was carried out in a slurry reactor. The Co–Mo, Ni–Mo, and Ni–W catalysts supported on γ-Al 2 O 3 were compared at the temperature of 340 °C and the pressure of 4.5 MPa. The HDS activity follows the order of Co–Mo > Ni–Mo > Ni–W at a high concentration of H 2 S, and the difference between Co–Mo and Ni–Mo becomes insignificant at a low concentration of H 2 S. The influence of reaction temperature 320–360 °C and reaction pressure 3–5.5 MPa was investigated, and both play a positive role in the HDS reaction. A kinetic model over Ni–Mo/Al 2 O 3 in the slurry reactor was established. The activation energy is estimated as 60.34 kJ·mol −1 ; the orders of sulfur components and hydrogen partial pressure are 1.43 and 1.30, respectively. The kinetic parameters are compared with those in a trickle-bed reactor, implying that the mass transfer is greatly enhanced in the slurry reactor. The back mixing effect is present in the slurry reactor and can be reduced by a multi-stage design, which would lead to higher reactor efficiency in industrial application. • Sweetening Siberian crude oil (HDS) meets the requirement of local refinery in Daqing. • A kinetic model over Ni–Mo/Al 2 O 3 in the slurry reactor is established. • The orders of sulfur component and hydrogen are 1.43 and 1.30, respectively. • The activation energy is 60.34 kJ ∙ mol −1 . • Mass and heat transfers are enhanced in the slurry reactor.

Continuous production of fatty acid methyl esters and high-purity glycerol over a dolomite-derived extrudate catalyst in a countercurrent-flow trickle-bed reactor

In this work, fatty acid methyl esters (FAME), as biodiesel components, were continuously produced via the heterogeneously catalyzed transesterification of palm oil with methanol vapor in a countercurrent-flow trickle-bed reactor. Dolomitic rock was used as natural calcium source in the preparation of the calcium oxide-based extrudate catalyst via a physical mixing method. Effects of operating parameters on the FAME yield and the two-phase flow behavior were investigated. The reaction system was characterized by a high mass diffusion resistance at gas-liquid-solid interfaces due to the low solubility of methanol in triglycerides and the high viscosity of oil. Mixing palm oil with commercial grade methyl decanoate, a C10 methyl ester (C10 CME), at a 1:1 mass ratio during the start-up period promoted FAME production. The FAME yield was enhanced by increasing the operating temperature and the methanol flow rate, while operation at a high oil flow rate severely decreased the FAME yield. The concentration of C10 CME, which acted as an emulsifier, in the catalyst bed was crucial to maintain the FAME production stability. In addition to a high FAME yield (ca. 92.3 wt%), the system provided glycerol, obtained without any washing, at a high purity of 93.6 wt%.

Simulation of bench-scale hydrotreating of vegetable oil reactor under non-isothermal conditions

A dynamic non-isothermal trickle-bed reactor model was developed to predict the temperature and concentration profiles of vegetable oil catalytic hydrotreating for the production of renewable fuel. A 5-lump kinetic model was implemented to predict the partial pressure and concentration profiles of products in the liquid phase. The simulated results with the proposed reactor model were compared with experimental information reported in the literature presenting good agreement.

Growth Dynamics of Bacterial Populations in a Two-Compartment Biofilm Bioreactor Designed for Continuous Surfactin Biosynthesis.

Biofilm bioreactors are promising systems for continuous biosurfactant production since they provide process stability through cell immobilization and avoid foam formation. In this work, a two-compartment biofilm bioreactor was designed consisting of a stirred tank reactor and a trickle-bed reactor containing a structured metal packing for biofilm formation. A strong and poor biofilm forming B. subtilis 168 strain due to restored exopolysaccharides (EPS) production or not were cultivated in the system to study the growth behavior of the planktonic and biofilm population for the establishment of a growth model. A high dilution rate was used in order to promote biofilm formation on the packing and wash out unwanted planktonic cells. Biofilm development kinetics on the packing were assessed through a total organic carbon mass balance. The EPS+ strain showed a significantly improved performance in terms of adhesion capacity and surfactin production. The mean surfactin productivity of the EPS+ strain was about 37% higher during the continuous cultivation compared to the EPS- strain. The substrate consumption together with the planktonic cell and biofilm development were properly predicted by the model (α = 0.05). The results show the efficiency of the biofilm bioreactor for continuous surfactin production using an EPS producing strain.

OPERATIONAL ASSESSMENTS TO IMPROVE THE MONITORING OF PETROLEUM CATALYTIC HYDRODESULFURIZATION PROCESSING

The present research evaluates the operational status of hydrodesulphurization oil processing based on the monitoring of the feed oil filtration system. The system is identified as a prognostic module, designed to predict the remaining catalyst activity in the trickle bed reactor. The influence of the oil feeding flow rate of the process was evaluated with focus on the level of activity of the catalyst bed of the reactor affected by content of soluble and fine contaminants of fed oil. During an operation campaign (45 days) of the HDS unity (filter, reactor) variations of LHSV (0.5 – 1.5 h-1) and pressure differential in the filter (110 – 200 Mpa) reflected in the reactor, where the activity of the catalyst diminished from 60 % to 54.0 %. The predictions, extrapolated to 700 campaign days, indicated a catalyst deactivation of about 50%, allowing a conversion of sulfur compounds around 43% to be maintained.

Process Design For Removal of Heavy Metals By A Bio-sorbent Trickle Bed System: A Proof of Concept

Most heavy metals are well-known toxic and carcinogenic agents and when discharged into the wastewater represent a serious threat to the human population and the fauna and flora of the receiving water bodies. The development of a novel biofilter was aimed in this project. The various parameters of the biofiltration processes, their mechanism for heavy metals removal along with the efficiency of the biofilters and its scale up aspects have been studied. The work was targeted towards removal of Iron (Fe) and Chromium (Cr), two very common contaminant in urban as well as rural ground water. These are also found in industrial spent waters. The efficiency of the biofiltration process for heavy metals removal have been critically analysed. In a proof-of-concept study, a laboratory-scale closed biofilter system employing the trickle bed process was operated to remove Iron (Fe) and Chromium (Cr) from a synthetic waste water sample at a load of 1000mg/L of the heavy metal. Gravel, citrus peels and spent tea leaves after proper pre-treatment was used as filter media. Depth profile analysis of the filter bed showed the reduction of a steep gradient of Iron and Chromium from the top layer to the bottom layer of filter media in the biofilter. Iron and Chromium level at the bottom of the biofilter decreased over 85% over a period of 6-8 hours of experiment. With these observations we have scaled up the process from a 0.050 L to 15.0 L operating volume. The results were consistent.

Heterogeneous Catalytic Ozonation of Phenol over Iron-based Catalysts in a Trickle Bed Reactor

The use of continuous reactors for heterogeneous catalytic ozonation is yet to be investigated in order to develop a viable technology for industrial applications. This paper presents hydrodynamic and degradation studies on the use of a co-current down flow trickle bed reactor for heterogeneous catalytic ozonation of phenol (as model pollutant) over Fe-Diatomite pellets and Fe-coated glass beads. It was found that the reactor can operate under trickle or pulsing flow regimes, promoting mass transfer augmentation. Residence time distribution data, fitted with n-CSTR and axial dispersion (ADM) models, showed low axial dispersion and high flow distribution. Just the Fe-diatomite pellets showed important phenol adsorption (16 %). Degradation experiments demonstrated that phenol conversion was substantial when using both catalysts, up to 19,7 % pollutant conversion with liquid-phase space times of just 6 s. Compared to direct ozonation, the use of the Fe-diatomite pellets and Fe-coated glass beads enhanced the reactor performance by 48 % and 23 %, respectively. It was confirmed that mass transfer is an important factor that restricts this reaction system performance; consequently, further improvement in mass transport rate is necessary for system optimization.

Maldistribution Effects in an Industrial-Scale Trickle Bed Reactor

Phasic maldistribution triggers hot spots within the catalyst bed in a trickle bed reactor. We investigate hot spot formation during hydrodesulphurization of diesel to understand the role of physic...

Set-Point Tracking Analysis of Controllers Designed for a Trickle-Bed Catalytic Reactor

Set-point tracking is one of the key performance benchmarks for a controller. In an industrial process, it is important to choose the optimal controller that offers the best performance. In this work, set-point tracking of 3 different controllers designed by different methods has been evaluated by comparing the closed-loop responses for a selected third-order delayed model.

Investigation of external mass transfer in micropacked bed reactors

Abstract In this work, the hydrogenation of α-methylstyrene to cumene over Pd catalyst is adopted to determine the external mass transfer performance under the mass transfer limited regime in micro-packed bed reactors. The operating temperature, pressure, and solvent are first confirmed for this method. Then the effects of gas and liquid superficial velocities as well as particle size on the external overall volumetric mass transfer coefficient are investigated. The external overall volumetric mass transfer coefficient in micro-packed bed reactors can reach 0.15–2.76 s−1, which is about one to two orders of magnitude larger than those of conventional large trickle bed reactors. Furthermore, a correlation of the external overall volumetric mass transfer coefficient is proposed and the external mass transfer process analysis is carried out.

Temperature effects on syngas biomethanation performed in a trickle bed reactor

Abstract Syngas, mainly consisting of CO, H2 and CO2, can be generated from the gasification of biomass and organic waste and constitutes an important energy and carbon source. However, its biological conversion is still challenging due to the low solubility and the toxic nature of its components. In this study, enriched mixed microbial consortia were inoculated in trickle bed reactors operated in continuous mode with the supply of artificial syngas (45% H2, 25% CO2, 20% CO and 10% N2) under mesophilic (37 °C) and thermophilic (60 °C) conditions. The results revealed a clear superiority of the thermophilic conditions exhibiting higher methane productivities, higher conversion efficiencies and lower yields of byproducts at all steady states tested compared to mesophilic temperature. The highest methane productivity achieved was 8.49 mmol∙lbed−1∙h−1. The microorganisms related to syngas biomethanation were investigated through metagenomic analysis of samples obtained from the inoculum, the liquid phase and the biofilm of the reactors. The continuous operation altered completely the dominant species in mesophilic conditions compared to the inoculum. Accumulation of volatile fatty acids (VFAs) under mesophilic conditions was attributed to the high relative abundance of the genus Sporomusa. A large quantity of acetogenic cell debris scavengers and potential acetogenic metabolism of the genus Thermincola could justify accumulation of VFAs under thermophilic conditions. Absence of aceticlastic methanogens in both reactors was also noticeable. The archaeal communities were enhanced in the biofilm compared to the liquid phase presenting a 6.2 fold and a 1.8 fold higher relative abundance at 37 °C and 60 °C, respectively.

Enhancement of heavy vacuum gas oil desulfurization via using developed catalyst based on Al2O3

In past few decades, a strong attention is paid to develop high-active catalysts for hydrotreating of the heavy vacuum gas oil (HVGO). In an agreement with that claim, this research work reports the synthesis of a developed catalyst for desulfurization of a petroleum HVGO fraction. Particularly, the catalytic performance of the catalyst, which was made via addition of CeO2 to ɣ alumina as supports for a trimetallic composite (CoNiMo-Al2O3), toward sulfur removal was investigated. For proper comparison, the activity of alumina individually-supported trimetallic catalyst CoNiMo-ɣAl2O3 at such application was also studied. The as-prepared catalysts were characterized by N2 physical adsorption/desorption (BET), transmission electron microscopy (TEM) and X-ray diffraction (XRD). Catalytic activity was conducted in continuous flow trickle-bed reactor at various operating condition of temperature (320-380 °C), pressure (20-60 bar) and liquid hour space velocity (1-2.5 h-1). It was found that CoNiMo/CeO2-ɣAl2O3 was of a higher catalytic efficiency to hydrotreating of HVGO than that of CoNiMo-Al2O3. Numerically, CoNiMo/CeO2-ɣAl2O3 could successfully remove 83.5 % of sulfur compounds while it was only 66.2% in case of CoNiMo-Al2O3. The increased catalytic performance of ceria containing composite may be due to its high specific surface area (∼198.4 m2·g−1) and small crystallite size (24.24 nm). Moreover, the incorporation of CeO2 to alumina could subsequently inhibit the interaction between Ni and alumina; hence the inactive NiAl2O4 phase had not been formed. Thus, an enhanced catalytic desulfurization process could be attained.

Liquid-solid mass transfer in a rotating trickle-bed reactor: Mathematical modeling and experimental verification

Liquid-solid mass transfer model is significant but deficient for the design of a rotating trickle-bed reactor (RTBR), which has great potential for process intensification of heterogeneous catalytic reactions. In this work, a mathematical model considering the wetting efficiency was first established to describe the liquid-solid mass transfer process in the RTBR. External static liquid holdup was referred to give a reasonable initial value for calculation. The profile of concentration boundary layer was obtained by mass balance analysis of an Eulerian element on a single sphere. The above model was then extended to predict the liquid-solid mass transfer coefficient (kLS) in the RTBR. A copper dissolution method was employed to measure the kLS, considering the effects of particle diameter, rotational speed, and liquid superficial mass velocity. The comprehensive comparison between predicted and experimental values of kLS was conducted and deviations were within ±25%.

Modelling and simulation of industrial trickle bed reactor hydrotreating for whole fraction low-temperature coal tar simultaneous hydrodesulfurisation and hydrodenitrification

Whole fraction low-temperature coal tar (LTCT) has a high content of heavy compounds, direct entry into an industrial reactor for hydrotreating (HDT) conversion into fuel oil is a new technology that has not been widely reported. Furthermore, a copious amount of heat is generated, resulting in hot spots and temperature flying on the catalyst bed.This study uses the gPROMS software, based on the kinetic parameters which are determined from several HDT reactions using experimental data in small-scale TBR, combined with energy balance and mass transfer equations among three phases to construct industrial TBR model with a treatment capacity of 250,000 tons/year. This model was used for simultaneous HDS and HDN process simulation.The Simulation results show that the sharp temperature rise along the catalyst bed length can arrive at 70 K without quenching, which is obviously higher than that of petroleum distillate hydrogenation. So, a optimal bed configuration of equal bed lengths and unequal bed inlet temperature was established by simulating and optimizing the reactor. with each bed 350 cm in length and inlet temperatures of 633 K, 643 K, 653 K, and 653 K, respectively, it has a reasonable temperature rise distribution, lower added hydrogen quench amount of 47360.65 Nm3/h, while sulfur and nitrogen removal rates can reach 87.55% and 86.46%, showing better performance than that of a small scale reactor. Hydrogen quenching not only lowers the temperature of the mixture and replenishes the chemical hydrogen consumption but also facilitates the removal of S, N heteroatom compounds. The results can provide a guidance for bed configuration for whole fraction LTCT industrial hydrogenation devices.

Optimization of γ-Alumina porosity via Response Surface Methodology: The influence of engineering support on the performance of a residual oil hydrotreating catalyst

As is evident in the literature, co-precipitation process has been narrowly studied from the "process" point of view thus far, and consequently majority of this complex phenomenon remains unknown scientifically. This work firstly tries to screen in depth the synthesis procedure of γ-Alumina in terms of precipitation, whereas such key parameters governing this process as temperature, reactant concentrations, mixing rate, and aging time are thoroughly analyzed by using Response surface methodology (RSM) for the very first time. Considering some significant novel interactions between these variables, the porosity of the final materials in terms of Specific Surface Area (SSA), Total Pore Volume (TPV), and Mean Pore Diameter (MPD) could be adjusted without using any surfactant or other additional organic compounds. For instance, simultaneous enhancement in SSA, TPV, and MPD, respectively, up to 334.5 m2. g−1, 1.93 cm3.g−1, and 23.01 nm with a narrow pore size distribution were achieved only by adjusting the process variables which have not been reported ever before. Two optimized materials suggested by Central Composite Design (CCD) were reproduced, analyzed by using such techniques as XRD, FT-IR, BET, SEM, and TG analyses and then used to prepare final Hydrotreating (HDT) catalyst for application in a trickle bed continuous hydrotreater.

Coupling non-isothermal trickle-bed reactor with catalyst pellet models to understand the reaction and diffusion in gas oil hydrodesulfurization

Abstract In this work, a trickle-bed reactor coupled with catalyst pellet model is employed to understand the effects of the temperature and catalyst pellet structures on the reaction–diffusion behaviors in gas oil hydrodesulfurization (HDS). The non-isothermal reactor model is determined to be reasonable due to non-negligible temperature variation caused by the reaction heat. The reaction rate along the reactor is mainly dominated by the temperature, and the sulfur concentration gradient in the catalyst pellet decreases gradually along the reactor, leading to the increased internal effectiveness factor. For the fixed catalyst bed volume, there exists a compromise between the catalyst reaction rate and effectiveness factor. Under commonly studied catalyst pellet size of 0.8–3 mm and porosity of 0.4–0.8, an optimization of the temperature and catalyst pellet structures is carried out, and the optimized outlet sulfur content decreases to 7.6 wppm better than the commercial level at 0.96 mm of the catalyst pellet size and 0.40 of the catalyst porosity.