Modeling of a pilot-scale trickle bed reactor for the catalytic oxidation of phenol
ARC Centre for Functional Nanomaterials, University of Queensland, Brisbane QLD 4072, Australia Separation and Purification Technology
(Impact Factor: 3.09).
06/2009; 67(2):158-165. DOI: 10.1016/j.seppur.2009.03.021
A mathematical model was developed to simulate the catalytic wet air oxidation (CWAO) of aqueous phenol in a trickle bed reactor (TBR). Both ‘axial dispersion’ and ‘plug flow’ models were proposed. ‘Steady-state’ mass transfers across different phases inside the reactor have all been considered in parallel with oxidation reactions catalyzed by heterogeneous copper catalyst supported on activated carbon. The changes in the concentrations of oxygen and phenol in various phases were thus depicted as a function of bed length. In order to validate the accuracy of the established TBR model, a series of experiments on phenol oxidation were performed on a pilot-scale TBR containing 5.6 l of catalysts. The model was found able to give satisfactory predictions for nearly half of all the runs. The discrepancies between the experimental and modeling results were investigated for the less promising runs. It was also noticed that similar simulation results could be attained from ‘axial dispersion’ model against ‘plug flow’ model. Following the discussion on the changes of phenol and oxygen concentrations in the various phases, it is finally concluded that the performance of the TBR of this study depends largely on gas-to-liquid mass transfer process. Further suggestions with regards to reactor optimization are also proposed on the basis of experimental outcome.
Available from: Jean-Henry Ferrasse
- "They present different interesting approaches, but any comparison with experimental data is done. Recently, Wu et al. (2009) proposed a modelling of a trickle bed reactor for WAO of phenol. The model is based on dimensionless numbers and parameters in order to facilitate the scale-up of the reactor. "
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ABSTRACT: This study develops a coupling of energetic and experimental design approaches on a given configuration of wet air oxidation process (WAO), applied for wastewater containing a hard chemical oxygen demand (phenol for instance). Taking into account thermodynamic principles and process simulation, the calculation of minimum heat required by the process, exergetic efficiency and work balance is presented. Five parameters are considered: pressure (20–30MPa); temperature (200–300°C); chemical oxygen demand (23–143gl−1); air ratio (1.2–2) and temperature of exiting steam utilities (160–200°C). Using the surface response method, it appears that initial chemical oxygen demand and temperature are the two parameters that mainly influence the result. With the modelling, good conditions for the functioning of the presented process are the following: pressure of 19.4MPa, temperature of 283°C, chemical oxygen demand of 54.9gl−1, air ratio of 1.7 and vapour temperature of 183°C.
Chemical Engineering Research and Design 07/2011; 89(7):1045-1055. DOI:10.1016/j.cherd.2010.12.009 · 2.28 Impact Factor
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ABSTRACT: 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 ReG and ReL was given by, PeG = AGReGbG exp(−dReL). The gas phase hold-up, H0G also 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 ReG and thus, PeL,Raschig = AL ReLbL for 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 PeL to increasing PeL with an increased liquid flow rate at ReL of about 750 and accordingly, PeL,Bale = A0 + A1ReLA2ReL2. 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.
Industrial & Engineering Chemistry Research 08/2011; 51(4):1647–1662. DOI:10.1021/ie200708y · 2.59 Impact Factor
Available from: Hamidreza Pirayesh
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ABSTRACT: In this research, the suitability of almond shell as a bio-waste resource in wood based composite manufacturing was investigated. Particleboards containing different almond shell particle rations were made using urea–formaldehyde (UF) resin. Some chemical properties of almond shell (holocellulose, α cellulose, lignin and ash contents, alcohol–benzene solubility, 1% NaOH solubility, hot and cold water solubility), mechanical (modulus of rupture, modulus of elasticity and internal bond strength) and physical properties (thickness swelling and water absorption) of the particleboards were determined. The addition of almond shell particles greatly improved the water resistance of the panels. However, flexural properties and internal bond strength decreased with increasing almond shell particle content. The amount of almond shell particles at most should be 30% in the mixture to meet the standard required for mechanical properties. Conclusively, almond shell, an annual agricultural residue, could be utilized with mixture of wood particles in the particleboard manufacturing.
Composites Part B Engineering 04/2012; 43(3). DOI:10.1016/j.compositesb.2011.06.008 · 2.98 Impact Factor
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