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Highlights: [•] A modified trickle bed reactor (MTBR) was developed for biodiesel production. [•] The heterogeneous Ca/Al composite oxide-based alkaline catalyst was applied. [•] The MTBR performed well with biodiesel yield >94%. [•] The MTBR had high efficient and well operational stability. [•] The process based on the new reactor simplified the flow-up production separation. [Copyright &y& Elsevier]

Abstract: Modeling the dynamics of fines/bacterial cells accumulation in gas–liquid–solid reactors/bioreactors is a difficult task which demands an improved understanding and quantification of the complex fluid dynamics, surface physical and microbiological phenomena coupled with (bio)chemistry and thermodynamic backgrounds. This contribution is offered as a step in that direction and presents two case studies with reference to modeling the complex physical and biological plugging/clogging phenomena in trickle-bed reactors/bioreactors, induced, respectively, by the retention of fine particles and by the formation of an excessive amount of biomass. The complex gas–liquid flow and space–time evolution of fines/bacterial cells capture, aggregation, detachment and migration in trickle-bed reactors/bioreactors were analyzed after a mathematical description was cast in terms of Euler–Euler two-fluid dynamic models based on the volume-average mass and momentum equations developed for multiphase systems coupled with species balance equations, solid deposit/biomass dynamics equations, filtration equations for the fines/bacterial cells and the aggregates, population balance equations for the fines/bacterial cells agglomeration. [Copyright &y& Elsevier]

Abstract: Clean liquid oil was obtained from low temperature coal tar (LCT) via hydrotreating in trickle-bed reactor (TBR) system filled with commercial catalysts. The effects of hydrogen pressure (10–16MPa), reactor temperature (350–410°C) and liquid hourly space velocity (LHSV) (0.25–1h−1) on hydrotreating performance were investigated while hydrogen to oil volume ratio was maintained constant at 1600LN/L in all cases. The degree of sulfur removal was greater than nitrogen removal with increasing temperature, pressure and contact time over the commercial catalyst. The TBR system was capable of removing nitrogen and sulfur from 1.14 and 0.34wt % in the feed to 63μgg−1 and 8μgg−1, respectively in the products. Gasoline (<180°C) and diesel (180–360°C) fraction were separated from the oil products and analyzed. The gasoline fraction produced from LCT by hydrotreating comply with gasoline specifications for distillation range, sulfur content, induction period and gum presence. But it did not meet the specifications for RON (Research Octane Number) specifications. Diesel fraction produced from LCT meet all quality tests as fuels which could be directly used as motor fuels without upgrading. The results indicated that the raw LCT could be considerably upgraded through catalytic hydrotreating and high-quality fuels were obtained. [Copyright &y& Elsevier]

Abstract: Active nickel catalysts (7wt%) supported over Mg–Al mixed oxides have been recently developed and it has also been demonstrated that they are also highly selective in Catalytic Wet air Oxidation (CWAO) of dyes. CWAO of Chromotrope 2R (C2R) has been studied using a trickle bed reactor employing temperatures from 100 to 180°C, liquid flow rates from 0.1 to 0.7mLmin−1 and initial dye concentration from 10 to 50ppm. Total pressure and air flow were 25bar and 300mLmin−1, respectively. The catalyst showed a very stable activity up to 24h on stream with an average TOC conversion of 82% at 150°C and T r =0.098gNi minmL−1. After the reaction, a 1.1wt% C of carbonaceous deposit is formed onto the catalyst and a diminution of 30% of the surface area with respect of the fresh catalyst was observed. An increase in the space time gave higher TOC conversions up to T r =0.098gNi minmL−1, attaining values of 80% at 180°C. The performance of TOC and dye removal does not decrease after two regeneration cycles. In total, a 57h effective reaction has been carried out with no loss of catalytic activity. [Copyright &y& Elsevier]

An inverted microscopy technique was implemented to scrutinizethe wall-region hydrodynamics of gas–liquid cocurrent flowsin micropacked beds. Digital image analysis enabled characterizationof two contiguous flow regimes, hysteresis, and transition thereof.Low- and high-interaction regimes featuring, respectively, slow andrapid displacements of gas–liquid boundary were identified.The onset of regime changeover was delineated by distinguishing thefluctuating behavior in time of characteristic lengths extracted fromthe areas occupied by gas and liquid in the field of view. A Charpentierand Favier flow regime map demarcating low and high interaction regimesin conventional macroscale trickle beds was elaborated for the sakeof comparison of micropacked bed transitions for three different gas–liquidsystems (air–water, argon–water, and argon–sucrosesolution). The flow regime map suggests that micropacked bed transitionoccurs at considerably lower L/Gvalues. Manifestation of hysteresis in micropacked beds was apprehended viapressure drop measurements and wetting fraction determinationboth in imbibition and drainage modes. In agreement with macroscalepacked bed observations, the drainage branch revealed a larger pressuredrop and wetting fraction compared with the imbibition branch forthe same set of bed and fluid flow rates. [ABSTRACT FROM AUTHOR]

Computational fluid dynamics (CFD) simulations are becoming increasingly widespread with the advent of more powerful computers and more sophisticated software. The aim of these developments is to facilitate more accurate reactor design and optimization methods compared to traditional lumped-parameter models. However, in order for CFD to be a trusted method, it must be validated using experimental data acquired at sufficiently high spatial resolution. This article validates an in-house CFD code by comparison with flow-field data obtained using magnetic resonance imaging (MRI) for a packed bed with a particle-to-column diameter ratio of 2. Flows characterized by inlet Reynolds numbers, based on particle diameter, of 27, 55, 111, and 216 are considered. The code used employs preconditioning to directly solve for pressure in low-velocity flow regimes. Excellent agreement was found between the MRI and CFD data with relative error between the experimentally determined and numerically predicted flow-fields being in the range of 3-9%. © 2012 American Institute of Chemical Engineers AIChE J, 2012 [ABSTRACT FROM AUTHOR]

Abstract: The selective removal of ammonia from industrial waste streams and the conversion of the organic matter to biodegradable compounds, without excessive mineralization of the carbon has been investigated over powder and pelletized titania- and zirconia-supported Pt catalysts in the wet air oxidation (WAO) of aqueous solutions at 200°C under 36bar of air, in batch and trickle-bed reactors. Ammonium acetate was chosen as a model compound (58mmolL−1, Total Organic Carbon, TOC=1392mgL−1, Total Nitrogen, TN=812mgL−1). In the absence of any catalyst, very little ammonium was removed. With addition of a Pt catalyst supported, NH4 + was completely eliminated from the reaction mixture and converted to dinitrogen with a selectivity higher than 97.5%. The treated effluent contained very low concentration of nitrates as a by-product. Interestingly, the platinum catalysts were very little active in the mineralization of the organic carbon, so that the effluent could be post-treated in a conventional biological plant. The catalysts showed the same performances over recycling experiments in a batch reactor. Moreover, the pelletized catalysts were shown to be stable upon preliminary continuous experiments in a trickle-bed reactor over a period of 350h. The 3%Pt/TiO2 catalysts were significantly more active than the 3%Pt/ZrO2 catalysts in batch and continuous experiments. [Copyright &y& Elsevier]

Abstract: Aiming to accomplish stringent regulations for the secure disposal of hazardous compounds, trickle beds have been envisaged from a process intensification point of view to adhere to environmental guidelines. In this work, several experimental and computational runs were performed under reacting flow conditions and cyclic (flow rate) modulations for the mineralization of liquid pollutants through electrical capacitance tomography (ECT) and computational fluid dynamics (CFD) techniques, respectively. First, we have investigated the hydrodynamics of propagating liquid pulsations generated via ON–OFF liquid, ON–OFF gas, and gas/liquid alternating cyclic operations. Here, the liquid pulsation intensity generated in ON–OFF gas mode indicated a negligible dependence with respect to cycle frequency apart from being qualitatively analogous with respect to ON–OFF liquid mode. Second, the effect of oxidation temperature and the gas and liquid flow rates unveiled the gas/liquid alternating mode as being able to generate sizable liquid payloads interrupted by gas and liquid streams. Correspondingly, we found higher detoxification rates due to the periodic pulsations sustained down to the reactor outlet by conferring improved catalyst wetting efficiencies. Finally, two-dimensional mappings of different cross-sections allowed inferring by means of ECT and CFD how the liquid payloads were morphologically in disposition to preserve or dissipate their original structure. [Copyright &y& Elsevier]

Abstract: One dimensional homogeneous and heterogeneous reactor models and nth-order and two-parallel reactions following first order kinetics were explored in order to compare their capabilities to predict the sulfur content in the liquid product coming from a trickle-bed bench-scale reactor, where hydrodesulfurization of vacuum gas oil took place. Experimental data of sulfur concentration obtained at T =340–380°C, P =5.3MPa, LHSV =1.0–3.0h−1 and hydrogen-to-oil ratio of 356m3/m3 were used to derive kinetic and related parameters. All proposed models showed accurate predictions being the pseudohomogeneous reactor model with two-parallel reactions kinetics the best one to simulate the bench-scale reactor in terms of minimal differences between the experimental and calculated sulfur concentration. Implications of using the different models are briefly discussed in order to evaluate their pertinence depending on the required level of detail and data available to describe the HDS process. [Copyright &y& Elsevier]

Abstract: Transport phenomena in multiphase reactors are poorly understood and first-principles modeling approaches have hitherto met with limited success. Industry continues thus far to depend heavily on engineering correlations for variables like pressure drop, transport coefficients and wetting efficiencies. While immensely useful, engineering correlations typically have wide variations in their predictive capability when venturing outside their instructed domain, and hence universally applicable correlations are rare. In this contribution, we present a machine learning approach for modeling such multiphase systems, specifically using the Support Vector Regression (SVR) algorithm. An application of trickle bed reactors is considered wherein key design variables for which numerous correlations exist in the literature (with a large variation in their predictions), are all correlated using the SVR approach with remarkable accuracy of prediction for all the different literature data sets with wide-ranging databanks. [Copyright &y& Elsevier]

Abstract: A new discrete model was developed for the design and analysis of catalytic trickle bed reactors operating in the low interaction regime based on the local structure of packed beds. By detailed comparisons of model predictions to experimental data the performance of the new model is demonstrated. By means of this model the steady-state behavior of trickle bed reactors can be studied in terms of operating conditions, physical properties of all three phases, transport parameters and isothermal reaction kinetics on a particle as well as on a reactor scale. [Copyright &y& Elsevier]

Abstract: This paper reports a study of steady-state heat transfer of gas and liquid flowing through a packed bed with spherical particles of 2.06mm and constant wall temperature with Computational Fluid Dynamics (CFDs). The effect of gas and liquid flow rates on heat transfer in packed beds are discussed. The effective radial bed conductivity (λ er ) is calculated based on the steady-state two dimensional model. The results of the CFD simulations have been validated with experiments and they are in a good agreement. For most of the cases the results of the CFD simulations deviate from the experimental results not more than 10%. The results show that the effective radial bed conductivity increases with increase of the velocity of gas and liquid. In trickle flow regime the effective radial bed conductivity is much bigger than in a dry gas flow regime. [Copyright &y& Elsevier]

A radiotracer study was carried out in a trickle bed reactor (TBR) independently filled with two different types of packing i.e., hydrophobic and hydrophilic. The study was aimed at to estimate liquid holdup and investigate the dispersion characteristics of liquid phase with both types of packing at different operating conditions. Water and H gas were used as aqueous and gas phase, respectively. The liquid and gas flow rates used ranged from 0.83 × 10-16.67 × 10 m/s and 0-3.33 × 10 m (std)/s, respectively. Residence time distribution (RTD) of liquid phase was measured using Br as radiotracer and about 10 MBq activity was used in each run. Mean residence time (MRT) and holdup of liquid phase were estimated from the measured RTD data. An axial dispersion with exchange model was used to simulate the measured RTD curves and model parameters (Peclet number and MRT) were obtained. At higher liquid flow rates, the TBR behaves as a plug flow reactor, whereas at lower liquid flow rates, the flow was found to be highly dispersed. The results of investigation indicated that the dispersion of liquid phase is higher in case of hydrophobic packing, whereas holdup is higher in case of hydrophilic packing. [ABSTRACT FROM AUTHOR]

Abstract: In this work, we propose a diffusion–convection–reaction methodology to gain further insights into the heterogeneous multiphase flow of trickle beds. Our case-study encompasses a multi-fluid model embedded within an interstitial framework on the numerical simulation of continuous catalytic wet oxidation of hazardous compounds. First, with the proviso that phase holdup, pressure drop, and liquid distribution are fundamental criteria for the efficient design of trickle beds, the multiphase flow constitutive equations have been developed and solved by the conservative unstructured finite volume method. Second, several numerical variables were parametrically optimized based on the application of different under-relaxation parameters, mesh densities, and time stepping strategies. The segregated solver has been found to reveal good properties in terms of convergence and stability criteria, which endorsed the further corroboration. Finally, this theoretical probing-sensing scheme enabled the characterization of liquid flow texture accomplished by three-dimensional flow patterns exposing their deviation from ideal plug flow. The diffusion–convection–reaction framework coupled within a CFD model can then be further exploited on the simulation of complex multiphase reactive flows with adjustable parameters. [Copyright &y& Elsevier]

Pt-promoted tungsten-hafnia catalysts containing different amounts of tungsten (15 and 20 wt% WO) were prepared and tested for hydroisomerization of n-hexadecane in a trickle-bed reactor. All catalysts were calcined under dry air flow at 723 K for 3 h. Pt-promoted sulfated hafnia was also prepared for the purpose of comparison. The catalysts were characterized using BET surface area, X-ray diffraction, and DRIFTS for the adsorption of pyridine. Tungsten-based hafnia catalysts exhibit moderate activity (<80 %) for hydroisomerization of n-hexadecane at a higher operating temperature of 673 K compared to sulfated hafnia (>95 %), which had an operating temperature of 493 K. However, tungsten-based hafnia catalysts were more selective towards iso-C even at higher n-hexadecane conversions. More cracking products were obtained with sulfated hafnia in which the selectivity to iso-C decreases exponentially with n-hexadecane conversion. The less acidic tungsten-hafnia catalysts may be suitable for producing more isomerized products compared to the sulfated analog. Graphical Abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

We extend the macroscopic nonequilibrium thermomechanical multiphase flow theory proposed by Hassanizadeh and Gray for porous media to analyze a set of drainage and imbibition experiments in trickle beds. The nonequilibrium model rests on inclusion of mass and momentum conservations for the gas-liquid interface, nonequilibrium capillary pressure, Helmholtz free energy gradients in the body supply of momentum for fluid bulk phases and gas-liquid interface, and mass exchange rates between interface and fluid bulks accounting for production and destruction of gas-liquid interfacial area. To solve the nonequilibrium model, entropy-consistent constitutive relationships are derived and calibrated using liquid holdup and bed pressure drop measurements in drainage and imbibition. The model captures very well the decay (drainage), and breakthrough (imbibition) curvatures of liquid holdup and pressure drop kinetics, while model closer inspection allows assessing the role of nonequilibrium capillary pressure and of dynamic interfacial mass exchanges for the production/destruction of interfacial area. © 2011 American Institute of Chemical Engineers AIChE J, 58: 3123-3134, 2012 [ABSTRACT FROM AUTHOR]

Abstract: The continuous catalytic oxidation of aqueous Crystal Violet (CV) solutions has been investigated using a nickel catalysts (7wt%) supported over Mg–Al mixed oxides in a trickle-bed reactor. The influence of the temperature, pressure, gas flow and dye initial concentration were studied in the catalytic wet air oxidation of CV. The catalyst showed a very stable activity up to 350h on stream with an average total organic carbon (TOC) conversion of 64%. CV and TOC removal were very sensitive to the temperature. Dye conversion augmented from 44.7% at 120°C to 86.1% at 180°C. Dye conversion varied from 62.6 to 18.4%, TOC from 59.5 to 18.7% and TN from 66.6 to 14.0% within 10 to 50ppm of initial dye concentration. The leaching of Ni was 6wt% of the initial metal present in the catalyst and a 0.59% of carbonaceous deposit was formed onto the catalyst surface. [Copyright &y& Elsevier]

Abstract: Catalytic wet air oxidation (CWAO) of a Basic Yellow 11 (BY11) aqueous solution, chosen as a model of a hardly biodegradable non-azo dye was carried out in a continuous-flow trickle-bed reactor, using nickel supported over hydrotalcite precursor calcined at 550°C. An increase in the reaction temperature (120–180°C), and a decrease in dye concentration (1000–3000ppm) or liquid flow rate (0.1–0.7mLmin−1) enhanced the CWAO performance in a 30 and 19% for the variation of the temperature and concentration respectively. After a small leaching observed within the first hours, the catalyst proved to be very stable during the 65-day reaction. The CWAO process was found to be very efficient, achieving BY11 conversion up to 95% and TOC conversion up to 85% at 0.1mLmin−1 and 180°C under 5MPa air. [Copyright &y& Elsevier]

Abstract: A major concern of hydroprocessing operations is that the substantial heat release produces a sharp temperature rise along the reactor, especially under start-of-run (SOR) conditions with fresh catalyst, which may induce local overheating if reaction temperature is not properly controlled by a quenching system. In this context, it is of extreme relevance to understand reactor dynamics in order to establish an optimal start-up strategy. This work presents an analysis of the transient behavior of a front-end fixed-bed hydrodemetallization (HDM) process based on a three-phase dynamic reactor model. The mathematical model was constructed and fitted on the basis of bench-scale experiments. The model accounts for major hydroprocessing reactions, mass-transfer and catalyst deactivation. The model was applied to analyze industrial reactor performance subjected to process parameter variations. The simulations revealed that quenching must start before or as soon as the hydrocarbon front reaches the quench box in order to avoid overheating and that under SOR conditions special care must be taken into account to select the lowest possible feed temperature. It was determined that the safest start-up strategy was to stabilize the catalyst at low temperature followed by a soft temperature increase in order to meet product specifications in a short period of time. [Copyright &y& Elsevier]

Abstract: Numerical simulations of the two-phase flow distribution in a trickle-bed reactor used for fuel hydrodesulfurization are reported. As a first step, the heat and mass transfer, as well as the chemical reactions, are not considered. The reactor has four packed-beds and a distribution tray above the catalytic beds equipped with cylindrical chimneys. The flow distribution at the outlet of the circular chimney predicted by the simulations is not axisymmetric because of the spatial distributions of the liquid and gas inlets in the chimney. This causes that the liquid entering the packed beds is distributed in three main streams. For the simulation of the two-phase flow in the packed beds, an Eulerian three-phase model that considers the particles of catalyst as a granular static phase has been used following the Holub single slit model for particle–fluid interaction to compute the liquid–solid and gas–solid drag coefficients. Numerical simulations of the dispersion of water–air flow in a column of glass beads using this model were initially carried out and results were found to be in reasonable agreement with numerical and experimental data available in the literature. The simulations consider the flow dispersion in the central region of the reactor bed as well as in the region close to the cylindrical lateral wall of the reactor. In both cases most of the liquid spreading takes place in the top part of the bed. The distributions of the liquid volume fraction do not change significatively as the depth of the bed is increased except in the third bed and at the interface of two beds with different porosity. [Copyright &y& Elsevier]

Catalytic wet-air oxidation (CWAO) of aqueous solutions of bisphenol A (BPA) was investigated in a trickle-bed reactor at temperatures up to 230 °C and oxygen partial pressure of 10.0 bar over TiO2and Ru/TiO2solids. It was observed that in the given range of operating conditions BPA undergoes both noncatalyzed and catalyzed oxidation routes. The employed Ru/TiO2catalyst containing 3.0 wt % of metallic phase enabled complete removal of BPA and more than 96% of TOC removal at temperatures of 200 °C and above. No catalyst deactivation occurred that could be attributed to the dissolution of active ingredient material. At these conditions, no carbonaceous deposits were accumulated on the catalyst surface. The acute toxicity of end-product solutions to organisms from different taxonomic groups and estrogenicity determined by the genetically modified yeast, compared with those of the feed solutions, was significantly reduced by CWAO treatment over the Ru/TiO2catalyst. For comparison, oxidative destruction of BPA was also investigated in this study by means of either photolytic or heterogeneous photocatalytic oxidation. A commercial TiO2photocatalyst illuminated by UV light enabled complete removal of BPA; however, lower decrease of toxicity and estrogenicity in the treated solution was observed. [ABSTRACT FROM AUTHOR]

The selective hydrogenation of 1-heptyne over a 2 wt % Pd/Al2O3catalyst was studied in a trickle bed reactor operating in both batch recycle and continuous modes. The reaction was studied in a range of different solvents, including isopropanol, hexane, mixtures of these two solvents, and also isopropanol with small quantities of water and base (NaOH) added. It was found that the rate of reaction was fastest in hexane, owing to the higher hydrogen solubility in this solvent. However, the selectivity toward 1-heptene was higher in isopropanol, with over 95% selectivity being maintained for 120 min of the total 240 min reaction time. The addition of water or base led to an increase in reaction rate, possibly through modification of the adsorption equilibria at the catalyst surface or direct involvement in the reaction. The hydrodynamics of trickle flow upon the reaction were investigated, showing that increasing liquid flow rate led to enhancement of reaction rate, although a plateau was eventually reached at the higher flows. The higher flows led to improved catalyst wetting, liquid hold up, and mass transfer rates, thus explaining the enhanced reaction rate. The concentration profiles were fitted according to a Langmuir–Hinshelwood kinetic expression. Operation in continuous flow was demonstrated, although a long residence time was required for high conversion, leading to lower 1-heptene selectivity compared with batch recycle operation. [ABSTRACT FROM AUTHOR]

Palladium catalysts based on different supports, silica(SiO2), zirconia (Z), sulfated ceria (CeS), and sulfatedzirconia(ZS), previously tested in a semibatch reactor, were chosen to demonstratehow the direct synthesis process can be improved by continuous operationin a three-phase fixed bed. The gas and liquid flow rates were systematicallyvaried to find suitable combinations for a maximum hydrogen peroxideproduction rate and selectivity. Different catalysts gave the sameresults in terms of selectivity and production rate with differentoperating conditions. A selectivity of 60% and 70% was found withtwo different catalysts (namely, Pd-ZS and Pd-CeS). Very interestinglythose selectivities were found with different gas and liquid flowrates (i.e., 70% of selectivity for Pd-ZS with liquid 1 mL/min andgas 2.7 mL/min, liquid 0.5 mL/min MeOH and gas 4 mL/min, and finallyliquid 2 mL/min MeOH and gas 1 mL/min 65% of selectivity for Pd-CeSwith liquid 1 mL/min and gas 4 mL/min). Moreover, the same maximumproduction rate of H2O2around 3 μmol/minfor Pd-CeS, Pd-ZS, and Pd-Z was achieved with different liquid andgas flow rates. Continuous operation and reactor technology play importantroles in this green synthesis: optimization of gas and liquid flowrates and contact time between the liquid and the solid (catalysts)phase lead to a dramatic selectivity improvement in a continuous reactor,raising the value obtained in the semibatch reactor from 30% to 70%. [ABSTRACT FROM AUTHOR]

Most existing studies in foaming trickle bed reactors aim at the improvement of efficiency and operational parameters leading to high economic advantages. Conventionally, most of the industries rely on frequently used gas continuous flow (GCF) where operational output is satisfactory but yields are not as efficient as in pulsing flow (PF) and foaming pulsing flow (FPF). Hydrodynamic characteristics like regime transitions are significantly influenced by the foaming nature of liquid as well as gas and liquid flow rates. The aim of this study was to experimentally demonstrate the effects of liquid flow rate, gas flow rates and liquid surface tension on regime transition. These parameters were analyzed for the air-aqueous sodium lauryl sulphate and air-water systems. More than 240 experiments were done to obtain the transition boundary for trickle flow (GCF) to foaming pulsing flow (PF/FPF) by use of excessive foaming 15-60 ppm surfactant compositions. The trickle to pulse flow transition appeared at lower gas and liquid flow rates with decrease in liquid surface tension. All experimental data were collected and drawn in the form of four different transitional plots which are compared and presented by using flow coordinates proposed by different researchers. A prominent decrease in dynamic liquid saturation was observed, especially during the regime transitional change. The reactor two phase pressure had an evident sharp rise, verifying the regime transition shift from GCF to PF/FPF. The study revealed that the regime transition boundary is significantly influenced by any change in hydrodynamic as well as physiochemical properties including surface tension. [ABSTRACT FROM AUTHOR]

Abstract: Fossil fuel is still a predominant source of the global energy requirement. Hydrotreating of whole crude oil has the ability to increase the productivity of middle distillate fractions and improve the fuel quality by simultaneously reducing contaminants such as sulfur, nitrogen, vanadium, nickel and asphaltene to the levels required by the regulatory bodies. Hydrotreating is usually carried out in a trickle bed reactor (TBR) where hydrodesulfurization (HDS), hydrodenitrogenation (HDN), hydrodemetallization (HDM) and hydrodeasphaltenization (HDAs) reactions take place simultaneously. To develop a detailed and a validated TBR process model which can be used for design and optimization of the hydrotreating process, it is essential to develop kinetic models for each of these reactions. Most recently, the authors have developed kinetic models for all of these chemical reactions except that of HDAs. In this work, a kinetic model (in terms of kinetic parameters) for the HDAs reaction in the TBR is developed. A three phase TBR process model incorporating the HDAs reactions with unknown kinetic parameters is developed. Also, a series of experiments has been conducted in an isothermal TBR under different operating conditions affecting the removal of asphaltene. The unknown kinetic parameters are then obtained by applying a parameter estimation technique based on minimization of the sum of square errors (SSEs) between the experimental and predicted concentrations of asphaltene compound in the crude oil. The full model with the estimated kinetic parameters is then applied to evaluate the removal of asphaltene (thus affecting fuel quality) under different operating conditions (than those used in experiments). [Copyright &y& Elsevier]

Steady-state performances of a trickle bed reactor (TBR) and a biofilter (BF) in loading experiments with increasing inlet concentrations of polar solvents, acetone, methyl ethyl ketone, methyl isobutyl ketone and n-butyl acetate, were investigated, along with the system's dynamic responses. Throughout the entire experimentation time, a constant loading rate of aromatic components of 4 gc·m−3·h−1 was maintained to observe the interactions between the polar substrates and aromatic hydrocarbons. Under low combined substrate loadings, the BF outperformed TBR not only in the removal of aromatic hydrocarbons but also in the removal of polar substrates. However, increasing the loading rate of polar components above the threshold value of 31–36 gc·m−3·h−1 resulted in a steep and significant drop in the removal efficiencies of both polar (except for butyl acetate) and hydrophobic components, which was more pronounced in the BF; so the relative TBR/BF efficiency became reversed under such overloading conditions. A step-drop of the overall OLPOLAR (combined loading by polar air pollutants) from overloading values to 7 gc·m−3·h−1 resulted in an increase of all pollutant removal efficiencies, although in TBR the recovery was preceded by lag periods lasting between 5 min (methyl ethyl ketone) to 3.7 h (acetone). The occurrence of lag periods in the TBR recovery was, in part, due to the saturation of mineral medium with water-soluble polar solvents, particularly, acetone. The observed bioreactor behavior was consistent with the biological steps being rate-limiting. [ABSTRACT FROM PUBLISHER]

Abstract: Monolith three-phase reactors are candidate reactors for implementing the catalytic process of sulfur removal from gasoil because of the good mass transfer characteristics, low pressure drop, high geometric surface area and low axial dispersion and backmixing. An integrated approach which links momentum, mass and enthalpy transport processes in a monolith three-phase reactor under high-pressure gasoil sulfur removal conditions was proposed in this work. The two-scale, non-isothermal, unsteady-state model developed was used to analyze the effects of the catalyst loading, pressure, temperature, superficial liquid and gas velocity, reactants/products concentration on the performance of the monolith three-phase reactor. The value of the simulated behavior of the monolith reactor was discussed in the light of a sensitivity analysis of the model outputs with regard to the mass transfer parameters. The sulfur removal performance of the upflow configuration of the monolith three-phase reactor was compared with the performance of a usual trickle bed reactor operated at the same liquid space velocity based on the mass of catalyst. [Copyright &y& Elsevier]

Abstract: A numerical model for liquid mal-distribution in randomly trickle bed reactors has been investigated and the results are compared with the experimental data. A CFD model based on the three-phase Eulerian approach is developed and a two-fluid model is utilized to perform the inter-phase momentum exchanges. Furthermore, radial distribution of the bed porosity is considered adjacent to the reactor wall. Two different types of liquid inlet distributors have been used in order to study the accuracy of the CFD model. To validate the CFD model, the simulation results are compared with the experimental data and the results from the porous media concept in which the permeability model has been applied to implement the inter-phase momentum exchange. Experimental results have been obtained on an industrial trilobe catalyst under a trickling flow regime in a pilot scale reactor setup. Co-current liquid and gas streams have entered to the reactor through a mono or multi orifice distributor. Results of the developed CFD model have found more accurate than that of the porous media concept when compared with the experimental data. [Copyright &y& Elsevier]

In this study, a three-dimensional Eulerian computational fluid dynamics (CFD) reactive flow model is developed for the trickle flow regime in a packed bed. The experimental study of porosity distribution in a bed of extrudates has been performed and then used to implement the local porosity values in the CFD computational grid. The reactive flow study addressed gas and liquid reactant limited systems. For each case a closed form approach of coupling the bed and particle scale solution within the CFD framework is presented. Model predictions achieved satisfactory agreement with experimental data for liquid holdup, wetting efficiency, and reactant conversion. [ABSTRACT FROM AUTHOR]

The hydrodynamics of countercurrent gas and liquid flows through a trickle bed reactor with unstructured (8 mm Raschig rings) and structured (Bale) packing has been investigated using the residence time distribution (RTD) approach. The operation was carried out with gas and liquid Reynolds number over the range 0 < ReG< 150 and 0 < ReL< 1500, respectively. Gas phase Peclet number, PeG, was generally higher in the randomly packed Raschig rings than in the structured Bale packing but increased with ReG. However, gas phase mixing decreased with increasing liquid flow rate. Specifically, the dependency on ReGand ReLwas given by, PeG= AGReGbGexp(−dReL). The gas phase hold-up, H0Galso increased with gas flow rate but decreased with the liquid flow rate. Owing to the statistical nature of the gas flow through beds, a Snedecor F-distribution was used to describe the gas phase RTD data and hence, the dynamics of the macroscopic flow pattern within the bed was determined from the intensity function, I(t). This indicated initial gas recirculation in stagnant zones within the bed with the flow pattern subsequently evolving into predominantly a channelling and bypassing type. Interestingly, the liquid phase mixing behavior appeared to be independent of ReGand thus, PeL,Raschig= ALReLbLfor the unstructured bed, but flow through the more open Bale packing revealed two types of mixing regimes, with a crossover from the region of decreasing PeLto increasing PeLwith an increased liquid flow rate at ReLof about 750 and accordingly, PeL,Bale= A0͔帬එ碽. Liquid hold-up, H0L, could be decoupled into a static component, HSL, and dynamic contribution, HDL, with the latter being proportional to the liquid flow rate. The Bale packing has a higher static hold-up (0.225) than the randomly packed Raschig rings (0.100) due to its more open structure. On the whole, it seemed that liquid phase back-mixing was generally lower in the unstructured packed bed than in the structured Bale packing. The associated higher static hold-up and reduced sensitivity with increasing liquid flow rate makes the latter the preferred choice for catalytic distillation for operations bounded by the loading and flooding envelopes. [ABSTRACT FROM AUTHOR]

The sensitivity of catalytic reactions to concurrent filtration and fines deposition in trickle-bed reactors (TBRs) was assessed by means of the catalytic hydrogenation of α-methylstyrene from kaolin–kerosene suspension flows. A negative correlation between catalytic conversion and the specific deposit of the bed resulted from the extra mass-transfer step that built up on the collectors in the course of filtration. The severity of the evolving extra mass-transfer step was sensitive to deposit compaction resulting from higher gas superficial velocities. Furthermore, irreversible catalyst activity losses were observed after catalyst cleanup and were ascribed to irretrievable active sites by catalyst intraparticle fines trapping. Fines accumulation in the catalyst bed was notably reduced by means of high-porosity solid-foam modules used as guard filters and placed upstream of, and adjacent to, the trickle bed. Hydrodynamic studies were carried out with alumina and silicon carbide solid foams to assess their role on the distribution of suspension and the reduction of specific deposit and pressure drop in trickle beds. It was found that the foam capture efficiency critically depended on the open connectivity of foam cells and the physicochemical nature of foam materials. The numbering up of foam modules led to reduced overall specific deposits of the beds and pressure drops, foreseeing a prospect for prolonging the hydrotreatment TBR lifetime, using solid foam as guard beds. [ABSTRACT FROM AUTHOR]

Previous simulations used to predict the enhancement in performance available through the periodic operation of trickle-bed reactors have been hampered by the use of volume-averaged models and correlations, which patently fail to describe fully the observable intricacies of the flow field and their often decisive consequences for the mass transfer and reaction behavior. NMR-tomography measurements of local liquid distribution can be utilized to ascertain the true local dynamics of catalyst particle wetting, which, in conjunction with previously developed models for periodically wetted catalyst particles, can provide both a more reliable assessment of the benefits of periodic operation and indications of geometric and other design parameters that might be modified to amplify its effects. [ABSTRACT FROM AUTHOR]

Abstract: Computational fluid dynamics (CFD) modeling of trickle-bed reactors with detailed interstitial flow solvers has remained elusive mostly due to the extreme CPU and memory intensive constraints. Here, we developed a comprehensible and scalable CFD model based on the conservative unstructured finite volume methodology to bring new insights from the perspective of catalytic reactor engineering to gas–liquid–solid catalytic wet oxidation. First, the heterogeneous flow constitutive equations of the trickle bed system have been derived by means of diffusion–convection–reaction model coupled within a Volume-of-Fluid framework. The multiphase model was investigated to gain further evidence on how the effect of process variables such as liquid velocity, surface tension and wetting phenomena affect the overall performance of high-pressure trickle-bed reactor. Second, as long as the application of under-relaxation parameters, mesh density, and time stepping strategy play a major role on the final corroboration, several computational runs on the detoxification of liquid pollutants were validated accordingly and evaluated in terms of convergence and stability criteria. Finally, the analysis of spatial mappings for the reaction properties enables us to identify the existence of relevant dry zones and unveil the channeling phenomena within in the trickle-bed reactor. [Copyright &y& Elsevier]

An experimental investigation was carried out to determine the effects of gas and liquid flow velocities and surface tension on the two-phase phase pressure drop a in a downflow trickle bed reactor. Water and non- Newtonian foaming solutions were employed as liquid phase. More than 240 experimental points for the trickle flow (GCF) and foaming pulsing flow (PF/FPF) regime were obtained for present study. Hydrodynamic characteristics involving two-phase pressure drop significantly influenced by gas and liquid flow rates. For 15 and 30 ppm air-aqueous surfactant solutions, two-phase pressure drop increases with higher liquid and gas flow velocities in trickle flow and foaming/pulsing flow regimes. With decrease in surface tension i.e. for 45 and 60 ppm air-aqueous surfactant systems, two-phase pressure drop increases very sharply during change in regime transition at significantly low liquid and gas velocities. Copyright © 2011 BCREC UNDIP. All rights reserved. [ABSTRACT FROM AUTHOR]

Abstract: H2O2 direct synthesis over two bimetallic, palladium-gold catalysts based on sulfated ceria (PdAu-CeS) and on sulfated zirconia (PdAu-ZS) has been studied in a continuous, trickle-bed reactor, at −10°C and 10bar. Three different liquid flow rates and seven different gas flow rates were used. The combined effect of liquid and gas flow rates, with two different H2/O2 ratio (2/18 and 4/16) in the gas feed, has been studied, by independent variations. The highest H2/O2 ratio always increases production rate and selectivity. In the case of 4/16 ratio, PdAu-CeS catalyst shows an enhancement in selectivity only, while the increase in H2O2 production rate is not significant compared to the 2/18 ratio case. PdAu-ZS catalyst shows a remarkable gain in both selectivity and production rate when the 4/16 ratio in gas feeding is used, outperforming the PdAu-CeS catalyst. The enhancement of the catalytic activity is more pronounced in the case of PdAu-ZS, compared to PdAu-CeS, when the highest H2/O2 ratio is used. A selectivity up to 90% has been measured on PdAu-ZS with the higher H2/O2 ratio and larger liquid flow rates. The maximum production rate measured is 6μmol/min (i.e. a productivity 0.18mol H2O2 gPd −1 h−1) with 1ml/min liquid flow rate and 2.7ml/min gas flow rate again on PdAu-ZS. [Copyright &y& Elsevier]

Abstract: The potential of using sludge based activated carbons (SBACs) for catalysing the wet air oxidation (WAO) of phenol, o-cresol, o-chlorophenol and p-nitrophenol was assessed in both a batch slurry reactor and a continuous trickle-bed reactor. In the batch reactor, the activity of two powdered carbons prepared from, respectively, dewatered raw (DRAW) sludge and dewatered, mesophilic anaerobically digested (DMAD) sludge was tested at 160°C and 4.2bar of oxygen partial pressure. Continuous, trickle-bed reactor experiments of up to 72h were conducted at similar operating conditions to study the durability and catalytic wet air oxidation (CWAO) performance of three economically promising steam activated SBACs. Due to their low mechanical strength, the two DRAW derived SBACs tested were produced using two different attrition resistance enhancement techniques. A commercial activated carbon (Chemviron, AP4-X) was employed as the reference catalyst for all of the tests. In the batch runs, the SBACs and AP4-X achieved high levels of pollutant conversion in the case of phenol, o-cresol and o-chlorophenol. However, irrespective of the carbon tested, p-nitrophenol was resistant to oxidation. When employed in the trickle-bed reactor, the DRAW derived SBAC pelletised using a lignosulphonate binder was found to be the most stable carbon. With this carbon the order of compound reactivity was as observed in the batch experiments. [Copyright &y& Elsevier]

Abstract: A critical revision has been carried out of experimental investigations to quantify the size of the liquid stagnant region in fixed beds with co-current gas–liquid down-flow, and its ability to exchange mass with the dynamic region and with the particle surface. The revision has exposed that a high level of uncertainty arise to estimate, particularly, the mass exchange rate from the available evidence. Therefore, a second purpose is to introduce a geometric model to represent the stagnant region for spherical particles from which, assuming that diffusion is the only mass transport mechanism, it becomes possible to estimate the mass exchange rates with the dynamic region and with the particle surface. Finally, it was discussed why to expect that the geometric model is able to provide a lower bound to mass exchange rate with the dynamic region and a tight lower bound to mass exchange rate with the catalyst surface. [Copyright &y& Elsevier]

Abstract: In this paper, NMR imaging was applied to study the distribution of the liquid phase in a fixed catalyst bed of an operating multiphase reactor with a cocurrent gas–liquid flow under conditions when the heterogeneous catalytic hydrogenation of 1-octene was taking place in the reactor. The 2D maps of the spatial distribution of the external and internal liquid holdups in the various regimes of the catalyst bed operation have been obtained for the first time in the course of the reaction. It was shown by a direct in situ method that an exothermic reaction taking place in a trickle bed reactor dramatically affected the distribution of the liquid phase in the catalyst bed. In particular, in the presence of the reaction, the catalyst bed was characterized by a non-uniform distribution of the liquid phase, as revealed by evaluating the external and internal liquid holdups. In the absence of the reaction, the bed was largely filled with the liquid phase. [Copyright &y& Elsevier]

Abstract: Heat transfer was investigated in an insulated packed bed column with co-current downflow of gas and liquid under constant and periodically modulated gas–liquid feed temperature. Bed temperatures at three axial positions were assessed at steady state for different insulating systems, different gas and liquid flow rates and system pressure. The experimental profiles recorded were modeled with a dynamic pseudo-homogeneous one parameter model to analyze the effect of operating conditions and to deduce coefficients of overall (U) and bed to wall (h W ) heat transfer. It appears that the heat transfer is strongly affected by the system pressure, whereas the liquid flow rate has a smaller influence. The experimental data of h W were correlated with the operating conditions leading to a small average error of 7% in the correlation. Condensation of water vapor occurring in the column seems to contribute to the heat transfer inside the packed bed. Several dynamic experiments modulating the feed temperature were also conducted and described with the help of the dynamic model. Predictions with the fitted values of U were in good agreement with experiments and give confidence to apply this model in the investigation of the catalytic wet air oxidation of phenol over carbon conducted in a trickle bed reactor under temperature feed modulation. [Copyright &y& Elsevier]

Modulation of electrical conductivity in kaolin/kerosene suspensions was examined as a means for the attenuation of fines retention in trickle-bed reactors. The suspension stability was remarkably enhanced through ON-OFF concentration modulation of an electrolyte-based kerosene conductivity improver and resulted in an efficient bed-cleaning strategy under operating conditions. Periodic additions of the conductivity improver enabled fines and deposits to gain momentarily large and similar electrical charges undoing, or impeding, multilayer deposition. The time evolution of the two-phase pressure drop and specific deposit with/without conductivity improver was monitored, as well as the corresponding local deposition structure via electrical capacitance tomography (ECT). Electrical conductivity modulation was found to reduce the bed-specific deposit by an order of magnitude and the bed pressure drop increment by a factor 14. ECT imaging evaluated the efficacy of this modulation strategy in mitigating deposition and in preventing filtration-induced flow maldistribution. © 2010 American Institute of Chemical Engineers AIChE J, 2011 [ABSTRACT FROM AUTHOR]

Abstract: One of the more difficult tasks in the petroleum refining industries that have not been considered largely in the literature is hydrotreating (HDT) of crude oil. The accurate calculations of kinetic models of the relevant reaction scheme are required for obtaining helpful models for HDT reactions, which can be confidently used for reactor design, operating and control. In this work, an optimization technique is employed to evaluate the best kinetic models of a trickle bed reactor (TBR) process utilized for hydrodenitrogenation (HDN) and hydrodemetallization (HDM) that includes hydrodevanadization (HDV) and hydrodenickelation (HDNi) of crude oil based on pilot plant experiments. The minimization of the sum of the squared errors (SSE) between the experimental and estimated concentrations of nitrogen (N), vanadium (V) and nickel (Ni) compounds in the products is used as an objective function in the optimization problem to determine the kinetic parameters. A series of experimental work was conducted in a continuous flow isothermal trickle bed reactor, using crude oil as a feedstock and the commercial cobalt–molybdenum on alumina (Co–Mo/γ-Al2O3) as a catalyst. A three-phase heterogeneous model based on two–film theory is developed to describe the behaviour of crude oil hydroprocessing in a pilot–plant trickle bed reactor (TBR) system. The hydroprocessing reactions have been modelled by power law kinetics with respect to nitrogen, vanadium and nickel compounds, and with respect to hydrogen. In this work, the gPROMS (general PROcess Modelling System) package has been used for modelling, simulation and parameter estimation via optimization. The model simulations results were found to agree well with the experiments carried out in a wide range of the studied operating conditions. The model is employed to predict the concentration profiles of hydrogen, nitrogen, vanadium and nickel along the catalyst bed length in three phases. [Copyright &y& Elsevier]

Abstract: Centralized environmental regulations require the use of efficient detoxification technologies for the secure disposal of hazardous wastewaters. Guided by federal directives, existing plants need reengineering activities and careful analysis to improve their overall effectiveness and to become environmentally friendly. Here, we illustrate the application of an integrated methodology which encompasses the experimental investigation of catalytic wet air oxidation and CFD simulation of trickle-bed reactors. As long as trickle-bed reactors are determined by the flow environment coupled with chemical kinetics, first, on the optimization of prominent numerical solution parameters, the CFD model was validated with experimental data taken from a trickle bed pilot plant specifically designed for the catalytic wet oxidation of phenolic wastewaters. Second, several experimental and computational runs were carried out under unsteady-state operation to evaluate the dynamic performance addressing the TOC concentration and temperature profiles. CFD computations of total organic carbon conversion were found to agree better with experimental data at lower temperatures. Finally, the comparison of test data with simulation results demonstrated that this integrated framework was able to describe the mineralization of organic matter in trickle beds and the validated consequence model can be exploited to promote cleaner remediation technologies of contaminated waters. [Copyright &y& Elsevier]

Representative reaction kinetics are difficult to obtain in multiphase laboratory trickle bed reactors, particularly when the gaseous reactant is rate-limiting, because of mass transport resistances and reactor hydrodynamics in the trickle bed regime. The ruthenium-catalyzed hydrogenolysis of lactic acid to propylene glycol has been examined in trickle bed and batch reactors to better understand the influence of mass transfer and partial wetting and to identify operating conditions where intrinsic kinetic rates can be obtained. At high liquid flow rates and low conversions in the trickle bed reactor, propylene glycol formation rates agree well with intrinsic rates obtained in a stirred batch reactor, with rate independent of feed flow rate or bed configuration in the trickle bed reactor. Application of a mass transport model to the trickle bed reactor at lower flow rates allows rates to be predicted outside the intrinsic kinetic regime. These results provide guidance for proper operation of laboratory trickle bed reactors and make it possible to predict performance in a trickle-bed reactor based on experiments conducted in bench-scale batch reactors. [ABSTRACT FROM AUTHOR]

Abstract: Hydrodynamics and transport phenomena inside Trickle Bed Reactors are strongly modified when superficial liquid velocity is not sufficient to insure a perfect wetting of catalyst particles. For this reason, the impact of partial wetting on catalyst effectiveness has been widely studied in past, in case of isothermal reactions. Heat transfer limitations, inside or outside catalyst particles, have also been investigated, but only in case of total wetting. In the present study, the effect of partial wetting is quantified numerically for various kinetics, mass and heat transfer limitations. When possible, an analogy is proposed between 1D and 2D models of particles. Robust rules are proposed to take into account for partial wetting in 1D-radial models of particles. The case of partial evaporation inside catalyst pores is also studied. Evaporation phenomena is approximated following a simple approach. Performed calculations show that the effect of partial wetting can affect very strongly catalyst effectiveness factors, especially in case of evaporation in the pores. The use of 1D approximations gives a good prediction of the global catalyst efficiency, as far as boundary conditions are symmetric between heat and mass transfer. Otherwise, 1D models are not relevant anymore. [Copyright &y& Elsevier]

In the present study, a computational modeling approach capable of simultaneously tracking the multiphase attributes of trickle flow is accomplished at high-pressure by means of computational fluid dynamics (CFD) codes. The morphological features of the gas−liquid structure accounted for by the CFD framework were embedded with a volume-of-fluid (VOF)-based interface capturing methodology for monitoring the gas−liquid interface dynamics supplemented with the droplets and rivulets formation triggered at unsteady-state conditions. Our research effort on transient operated trickle-bed reactors (TBRs) relied on assured benefits of their performance enhancement that ultimately investigated the application of the VOF model with the purpose to quantify the relationship between bed structure and downstream flow distribution in cocurrent packed beds. To accomplish this concept, first we evaluated the influence of model tuning parameters. Second, the effect of process liquid flow rates and operating pressures was examined thoroughly on liquid holdup and two-phase frictional pressure drop. Finally, we have performed a three-dimensional analysis of interstitial flow hydrodynamics that enabled us to identify the inhomogeneous nature of the multiphase flow environment on the catalytic packing scale. [ABSTRACT FROM AUTHOR]

Abstract: In this study single and two phase flow through the trickle bed reactor loaded with a two different loading manner, sock and dense, have been investigated numerically and experimentally. The CT-scan imaging and an image processing code have been used for investigation of radial porosity distribution of trilobe catalyst in sock and dense loading procedure in trickle bed reactors and two different correlations have been proposed. These correlations were used in a single and two phase CFD code for prediction of pressure drop of gas flow in dry and prewet trilobe catalyst packed bed and also pressure drop and dynamic liquid holdup for two phase flow. In addition, these variables were studied experimentally with a laboratory scale trickle bed reactor. The results of CFD simulations show a very good agreement with experimental data. [Copyright &y& Elsevier]

Abstract: One of the main challenges that face successful biofiltration is the erratic loading pattern and long starvation periods. However, such patterns are common in practical applications. In order to provide long-term stable operation of a biofilter under these conditions, a cyclic adsorption/desorption beds system with flow switching was installed prior to a biofilter. Different square waves of a mixture containing n-hexane and benzene at a 2:1 ratio were applied to the cyclic adsorption/desorption beds and then fed to a biofilter. The performance of this integrated system was compared to a biofilter unit receiving the same feed of both VOCs. The cyclic adsorption/desorption beds unit successfully achieved its goal of stabilizing erratic loading even with very sharp peaks at the influent concentration equalizing influent concentrations ranging from 10–470ppmv for n-hexane to 30–1410ppmv for benzene. The study included different peak concentrations with durations ranging from 6 to 20min. The cyclic beds buffered the fluctuating influent load and the followed biofilter had all the time a continuous stable flow. Another advantage achieved by the cyclic adsorption/desorption beds was the uninterrupted feed to the biofilter even during the starvation where there was no influent in the feed. The results of the integrated system with regard to removal efficiency and kinetics are comparable to published results with continuous feed studies at the same loading rates. The removal efficiency for benzene had a minimum of 85% while for n-hexane ranged from 50% to 77% according to the loading rate. The control unit showed very erratic performance highlighting the benefit of the utilization of the cyclic adsorption/desorption beds. The biofilter was more adaptable to concentration changes in benzene than n-hexane. [ABSTRACT FROM AUTHOR]

Abstract: This study applied a pilot-scale trickle-bed air biofilter (TBAB) system for treating waste gas emitted from the breather vent of a vertical fixed roof storage tank containing p-xylene (p-X) liquid. The volatile organic compound (VOC) concentration of the waste gas was related to ambient temperature as well as solar radiation, peaking at above 6300ppmv of p-X and 25000ppmv of total hydrocarbons during the hours of 8AM to 3PM. When the activated carbon adsorber was employed as a VOC buffer, the peak waste gas VOC concentration was significantly reduced resulting in a stably and efficiently performing TBAB system. The pressure drop appeared to be low, reflecting that the TBAB system could be employed in the prolonged operation with a low running penalty. These advantages suggest that the TBAB system is a cost-effective treatment technology for VOC emission from a fixed roof storage tank. [ABSTRACT FROM AUTHOR]