Showing papers in "Asia-Pacific Journal of Chemical Engineering in 2013"

Graphene and its application in fuel cell catalysis: a review

Abstract: Graphene is considered a promising material for fuel cell vehicles because of its excellent chemical, mechanical, and electrical properties. Recent studies have revealed that using graphene or modified graphene as the catalyst support or as a metal-free catalyst results in significant improvement in the electrocatalytic activity, long term durability, and CO tolerance. This article summarizes both the recent progress of graphene-based fuel cell research and current developments in graphene fabrication processes such as mechanical exfoliation, chemical vapor deposition, and chemical exfoliation. The roles of graphene are also discussed by introducing mechanisms on the basis of theoretical calculations as well as experimental analysis. © 2012 Curtin University of Technology and John Wiley & Sons, Ltd.

Comparison of the effects of wettability alteration and IFT reduction on oil recovery in carbonate reservoirs

Abstract: Injection of chemicals in a carbonate reservoir may change wettability and reduce interfacial tension (IFT). The question is how much each mechanism contributes to the increase in oil recovery. There is lack of such information in the literature. The information is very important because it will guide us to select which chemicals to use, as some chemicals can effectively reduce IFT, whereas others can change wettability. This paper aims to compare the effects of different mechanisms in oil recovery related to chemical enhanced oil recovery (EOR) . Particularly, we compare the effects of wettability alteration and IFT reduction. Numerical simulation models are used. Our results show that wettability alteration plays important roles when IFT is high, and it is effective in the early time. IFT plays very important roles with or without wettability alteration and is effective during the entire process. Note that the matrix permeability is reasonably high so that the fluids can be redistributed. The implication is that anionic surfactants are preferred to cationic surfactants in chemical EOR, as the former are generally used to reduce IFT, whereas the latter are used to change wettability. Other observations are that in surfactant-induced wettability alteration with low IFT, gravity drive is a very important mechanism. Molecular diffusion of chemicals affects oil recovery rate in the early time, but not ultimate oil recovery. © 2012 Curtin University of Technology and John Wiley & Sons, Ltd.

Adsorption of palladium and platinum from aqueous solutions by chitosan and activated carbon coated with chitosan

Abstract: In this work, the potential of chitosan and activated carbon coated with chitosan for palladium and platinum adsorption from aqueous solutions was investigated. The observed results showed that the optimum operating conditions for palladium and platinum adsorption on chitosan were initial pH 2, particle size of adsorbent = 0.21 mm and adsorbent dose = 10 g/L. Equilibrium studies showed that palladium and platinum adsorption on chitosan was of spontaneous and exothermic nature. Equilibrium results fitted with Langmuir, Freundlich, Temkin and Dubinin-Radushkevich models for two adsorbents. The maximum adsorption capacities for palladium and platinum adsorption were 62.50 and 66.66 mg/g of chitosan and 43.48 and 52.63 mg/g of activated carbon coated with chitosan, respectively. Kinetic data were found to confirm pseudo-second-order kinetic model. © 2012 Curtin University of Technology and John Wiley & Sons, Ltd.

Development of eggshell derived catalyst for transesterification of used cooking oil for biodiesel production

Abstract: The major drawback that prevents commercialization of biodiesel is the high cost of vegetable oil feedstock. In this work, used cooking oil, which is much less expensive than fresh vegetable oil, is used as an alternative raw material. Prior to transesterification reaction, esterification was conducted and catalyzed homogeneously to eliminate free fatty acid. Heterogeneous catalyst derived from cheap and easily obtained egg-shell (industrial waste) was used for transesterification reaction. A 100% ester yield was obtained at the optimized reaction conditions, which is 5 h of reaction duration, 24:1 methanol to oil molar ratio and 4 wt% catalyst loading. © 2013 Curtin University of Technology and John Wiley & Sons, Ltd.

Nanotoxicology of common metal oxide based nanomaterials: their ROS‐y and non‐ROS‐y consequences

Abstract: Inorganic nanomaterials form the bulk of the nanomaterials (NMs) found in consumer products that can easily enter into the food chain, biosystems and environment Because of their sizes and associated material characteristics, many studies have shown a fair degree of toxicity associated with these NMs This review consolidates and discusses the nanotoxicity of three commonly found inorganic oxide NMs, namely titanium dioxide, zinc oxide and silicon dioxide Because oxidative stress in the form of reactive oxygen species (ROS) is a major mediator of nanotoxicity, we have centered much of our discussion on mechanisms before and after ROS production due to these common NMs These NMs do exhibit non-ROS effects, not as well characterized but still biologically important The physiological transport of NMs and how they intersect with biological mechanisms that finally brought about cell death gave some insights of how these NMs might behave in biological systems and thus illustrate the impact of this new class of materials on human health © 2012 Curtin University of Technology and John Wiley & Sons, Ltd

Investigation of ultrasonic effect on synthesis of nano zero valent iron particles and comparison with conventional method

Abstract: In this work, a new method of the synthesis of nano zero valent iron (nZVI) is presented. Ultrasonic wave as a novel method is used to synthesize nanoparticles and the physico-chemical properties of particles compared with conventional synthesis method. Among the various synthesis methods, chemical reduction is widely used because of its simplicity. The effect of ultrasonic power (500 W, 1000 W), FeSO4.7H2O concentration (0.02, 0.05 and 0.08 M), NaBH4 concentrations (0.1, 0.25 and 0.4 M) and delivery rate of reducing agent on nZVI characteristics were investigated. Particle size distribution, morphology and surface composition were characterized by transmission electron microscopy, field emission scanning electron microscopy, X-ray diffraction (XRD), Brunauer, Emmett and Teller (BET) surface area and particle size analyzer. It was found that the morphology of nanoparticles changed from spherical type to plate and needle type under high ultrasonic power. The size of 50% of nanoparticles was decreased from 90.3 to 29.9 nm under high precursor/reductant concentration and high ultrasonic power. Also, BET surface area was increased from 10 to 42 m2/g while using ultrasonic waves. The XRD patterns showed that the crystallinity of the nZVI prepared using ultrasonic conditions was poor because of the inadequate time for nuclei growth and crystallization. Therefore, the ultrasonic power could impose dramatic effect on the characteristics of the nanoparticles. © 2013 Curtin University of Technology and John Wiley & Sons, Ltd.

Experimental investigations on the potential of SDS as low‐dosage promoter for carbon dioxide hydrate formation

Abstract: A laboratory-scale batch reactor is built and operated to study the kinetic of formation of carbon dioxide hydrate in deionized water and sodium dodecyl sulfate (SDS) solutions. In this experimental work, the formation of carbon dioxide hydrate in deionized water (18 Ω) is investigated at fixed temperature of 273.65 K and different pressures of 20, 25, 30, and 35 bar, respectively. The formation of carbon dioxide hydrate in SDS solutions is investigated by using various concentrations of SDS up to 3000 ppm at temperature of 273.65 K and 35 bar. For carbon dioxide hydrate, the induction time decreases with the increase of initial carbon dioxide pressure because of the increase of subcooling and driving force in the system. Moreover, experimental results show that the addition of SDS reduces the induction time required for hydrate formation and significantly increases the carbon dioxide uptake, and these effects are concentration dependent. Furthermore, the addition of SDS in the hydrate-forming systems has been shown to improve the apparent rate constant of the system. These results show that SDS shows a good promise to be used as low-dosage hydrate promoter to improve the efficiency of gas hydrate-based processes. © 2013 Curtin University of Technology and John Wiley & Sons, Ltd.

Membrane treatment of oily wastewater from refinery processes

Abstract: Oily wastewater is produced in oil refining processes. This waste is usually treated by a number of physical, chemical, and biological techniques in water treatment units of oil refinery before being disposed in environment or reused as agricultural water. One of the treatment techniques for oil separation from wastewater is membrane filtration. This paper presents the performances of hydrophilic microfiltration (MF GRM) and ultrafiltration (UF GRM) polymeric membranes challenged with synthetic feed (gas oil dispersed in water) and oily wastewater effluent of American Petroleum Institute unit in refinery. A comparison was carried out under optimum conditions and in cross-flow mode in laboratory scale. The effects of operating parameters (i.e. pressure and cross-flow velocity) on flux and rejection were elucidated. The flux of MF GRM membrane for real feed within the first 2 h of filtration was low compared with synthetic feed because of the presence of solid and colloidal particles in the real feed. The oil rejection (around 99%) for synthetic feed was higher compared with real feed. Similar trend was found for both UF GRM and MF GRM membranes. © 2012 Curtin University of Technology and John Wiley & Sons, Ltd.

Investigation of natural CaO–MgO sorbent for CO2 capture

Abstract: The cyclic CO2 capture activity of natural CaO-MgO sorbents derived from dolomite or limestone with different MgO contents has been investigated on a TGA, with the consideration of the influence of H2O during the carbonation and calcination. The scanning electron microscopy (SEM) and the brunauer emmett teller (BET) were used to characterize the fresh and used CaO-MgO sorbents. The results have indicated that the natural CaO-MgO sorbent with MgO content of 31.5%-38.7% should be good to improve the cyclic capture activity of CaO. The CaO-MgO sorbent has the best cyclic activity when H2O is present during both carbonation and calcination. H2O changes the sorbent morphology producing bigger particles and pores for the sintering during calcination but makes the sorbent have more stable surface area for the taking palace of the fast kinetic carbonation reaction. Besides, H2O decreases the product layer diffusion resistance and increases the reaction rate during the transition and the product layer diffusion control stage. After sorbent sinters during the reaction cycles, the H2O-improving effect becomes more obvious as the MgO content increases. The results indicate the potential of the natural CaO-MgO sorbent with proper MgO content for cyclic CO2 capture in the presence H2O. Copyright (c) 2013 Curtin University of Technology and John Wiley & Sons, Ltd.

A critical study on the removal of copper by an electrochemically assisted coagulation: equilibrium, kinetics, and thermodynamics

Abstract: The present paper provides an electrocoagulation process for the removal of copper from water through electrochemically generated Zn2+ using zinc as the anode and galvanized iron as the cathode. The different operating parameters on the removal efficiency of copper were investigated, such as initial copper ion concentration, initial pH, current density, and temperature. The results showed that the optimum removal efficiency of 96.6% was achieved at a current density of 0.05 A dm−2, at pH of 7.0. The effect of co-existing anions such as arsenate, phosphate, boron, and fluoride were studied on the removal efficiency of copper. The results of pilot scale study show that the process was technologically feasible. The adsorption of copper, preferably fitting the Langmuir adsorption isotherm, suggests monolayer coverage of adsorbed molecules. First and second-order rate equations, Elovich, and intraparticle diffusion models were applied to study adsorption kinetics. The adsorption process follows second-order kinetics model with good correlation. Temperature studies showed that adsorption was endothermic and spontaneous in nature. © 2012 Curtin University of Technology and John Wiley & Sons, Ltd.

Adsorption of mercury (II) ion from aqueous solution using low-cost activated carbon prepared from mango kernel

Abstract: A low-cost activated carbon (AC) was prepared from mango kernel through chemical activation with ZnCl2. The adsorption capacity of AC was investigated for the removal of Hg(II) from aqueous solution as batch experiments using varying initial adsorbent dosage, pH, equilibrium time and temperature. The prepared AC had a Brunauer-Emmett-Teller surface area of 920 m2 g−1 and total pore volume of 0.341 cm3 g−1, respectively. A maximum removal of 92% was achieved with an initial Hg(II) concentration of 10 mg L−1, pH 6.5 and adsorbent dose of 3 g L−1. The obtained kinetic experimental data were fitted to pseudo-first-order, pseudo-second-order and intraparticle diffusion models, respectively. Among the models, the pseudo-second-order adsorption model was found to fit better, with a coefficient of regression (R2) > 0.95. The equilibrium data were also fitted to the Langmuir and Freundlich equilibrium isotherm models. Both the models were found to provide a better fitting with coefficient of regression (R2) > 0.98. The enthalpy of adsorption was found to be 7.2 kJ mol−1. © 2012 Curtin University of Technology and John Wiley & Sons, Ltd.

Experimental and ANFIS modeling for fouling analysis of oily wastewater treatment using ultrafiltration

Abstract: This work presents an experimental investigation and modeling of fouling mechanisms involved in ultrafiltration of oily wastewater streams. Hermia's models were used to investigate the fouling mechanisms. The experimental results performed at different cross flow velocity (CFV) (0.5, 1, and 1.5 m/s) and transemembrane pressure (TMP) (1.5, 3, and 4.5 bar) showed that the best fit to the experimental data corresponds to the cake layer formation model followed by the intermediate blocking model for all the experimental conditions tested. Furthermore, this work explores the application of the ANFIS as a model to predict permeation in ultrafiltration (UF) system. The selected experimental data were trained by a hybrid learning algorithm combining the forward pass and the backward pass. The good agreement of the model with experimental data underscores the ease and accuracy of the ANFIS in modeling such a complex systems. © 2012 Curtin University of Technology and John Wiley & Sons, Ltd.

Rapid removal of cobalt (II) from aqueous solution using cuttlefish bones; equilibrium, kinetics, and thermodynamic study

Abstract: The objective of this study is to assess the adsorption potential of cobalt (II) using cuttlefish bones. The bones were treated with 0.01 N HCl to enhance the heavy metal uptake. The adsorbent was characterized using scanning electron microscope and energy dispersive X-ray spectrometer. An adsorption study was conducted in a batch system to optimize process variables such as initial concentration of cobalt (II), pH, sorbent loading, particle size, process temperature, and contact time. The optimal pH was found to be 9. The kinetic data followed the pseudosecond-order kinetic model, and the equilibrium time was found to be 20 min. In the first minute of the adsorption process, 50% of the cobalt (II) was adsorbed by the cuttle bones. Adsorption isotherms were expressed by the Langmuir and Freundlich adsorption models. The Langmuir adsorption model fits the experimental data reasonably well compared with the Freundlich model. The maximum adsorption capacity of this new sorbent was found to be 76.6 mg g−1 at 40 °C. Thermodynamic parameters, including the Gibbs free energy (ΔGo), enthalpy (ΔHo), and entropy (ΔSo), indicated that the adsorption of cobalt (II) by cuttlefish bones was feasible and endothermic at a temperature range of 20–40 °C. © 2012 Curtin University of Technology and John Wiley & Sons, Ltd.

Thermogravimetric study and modeling for the drying of a Chinese lignite

Abstract: Study of drying characteristics and kinetics of coal is necessary in order to optimize drying operation and design a dryer in industrial scale. Drying characteristics of Chinese lignite was investigated experimentally using thermogravimetric method, and the effect of drying variables on drying rate was systematically studied. For CFD modeling and scale-up purposes, it is useful to have an algebraic equation that describes the drying process of lignite. Therefore, different thin layer drying models given in the literature were employed to analyze coal drying kinetics under different conditions. During studying the consistency of all the models, statistical tests such as χ2, residual sum of squares (RSS), F-value, and the coefficient of determination R2 were employed. It was found that the Midilli–Kucuk model best describes the drying process within 99.9% accuracy. The effects of drying temperature and coal sample weight on the constants and coefficients of the selected model were also studied by multiple regression analysis. Apparent diffusion coefficient of moisture from sample was calculated using the experimental kinetics data. Higher drying temperatures and smaller sample weights resulted in higher diffusion coefficient, which was consistent with experimental data. Activation energy of moisture evaporation calculated from Arrhenius equation for drying process was 21.17 kJ/mol. The selected algebraic drying model can be used for CFD modeling during scale-up of drying facility for industrial applications. © 2013 Curtin University of Technology and John Wiley & Sons, Ltd.

Fault detection method for non-Gaussian processes based on non-negative matrix factorization

Abstract: In this work, a new fault detection method based on non-negative matrix factorization (NMF) is presented for non-Gaussian processes. NMF is a new dimension reduction technique that can preserve spatial relationships corresponding and retain the intrinsic structure of original data. The basic idea of our approach is to use NMF to extract the latent variables that drive a process and to combine them with process monitoring techniques. A modified alternating least squares algorithm with an order constraint and a fixed initialization is proposed for solving the NMF problem. In addition, kernel density estimation is adopted to calculate the confidence limits of defined statistical metrics for NMF-based monitoring method. Afterwards, the proposed method is applied to the Tennessee Eastman process to evaluate the monitoring performance, comparing with principal component analysis and independent component analysis. The experiment results clearly illustrate the feasibility of the proposed method. © 2012 Curtin University of Technology and John Wiley & Sons, Ltd.

Hybrid gradient particle swarm optimization for dynamic optimization problems of chemical processes

Abstract: Dynamic optimization problems (DOP) in chemical processes are very challenging because of their highly nonlinear, multidimensional, multipeak and constrained nature. In this paper, we propose a novel algorithm named hybrid gradient particle swarm optimization (HGPSO) by hybridizing particle swarm optimization (PSO) with gradient-based algorithms (GBA). HGSPO can improve the convergence rate and solution precision of pure PSO, and avoid getting trapped to local optimums with pure GBA search. We further incorporate HGPSO into control vector parameterization (CVP), a method converting DOP into nonlinear programming, to solve five complex DOPs. These DOPs include multimodal, multidimensional and constrained problems. The experiments demonstrate that HGPSO performs much better in terms of solution precision and computational cost when compared with other PSO variants. © 2013 Curtin University of Technology and John Wiley & Sons, Ltd.

Numerical and experimental study of steam‐water two‐phase flow through steam jet pump

Abstract: The Steam Jet Pump (SJP) is the most suitable pump for pumping radioactive and hazardous liquids because of its mechanical simplicity, no maintenance, low cost, easy construction, no leakage, simple control, and so on. The only problem with the SJP is the complexity in the transport phenomena involved in it. In this study, the void fraction in the mixing section has been measured experimentally through gamma-ray densitometry technique, and the flow through the SJP was simulated numerically. The reported numerical study of the SJP is very limited because of the complexity of the problem. In this work, three-dimensional steady state numerical simulations of the SJP were carried out using the Shah Direct-Contact Condensation (DCC) model developed previously. The experimental and Computational Fluid Dynamics (CFD) results of void fraction have been compared at different steam inlet pressure, and it was found that they match closely with each other. The transport phenomena in the SJP were explained using the CFD results of condensation heat transfer coefficient, steam plume shape, radial temperature distributions, and contours of static pressure and steam density. This study helps in validating the Shah direct-contact condensation model and providing valuable information about the transport phenomena occurring within the mixing section of the SJP. © 2013 Curtin University of Technology and John Wiley & Sons, Ltd.

Flow and heat transfer over a trapezoidal cylinder: steady and unsteady regimes

Abstract: Two-dimensional unconfined flow and heat transfer across a long tapered trapezoidal bluff body are investigated for the range Re = 1 to 150 (thereby covering both steady and unsteady periodic regimes) and Pr = 0.7 (air). A number of engineering parameters, e.g. drag and lift coefficients, Strouhal and Nusselt numbers, and others, is calculated for the above range of conditions. No flow separation occurs from the surface of the trapezoidal cylinder for the range Re ≤ 5; however, flow starts to separate from the rear surface of the cylinder at Re = 6. Therefore, the onset of flow separation exits between Re = 5 and 6. The critical value of the Reynolds number (i.e. transition from steady to unsteady) exists between Re = 46 and 47. The drag coefficient decreases with increasing Reynolds number in the steady regime; however, the drag increases with Reynolds number in the unsteady regime. The Strouhal number and the average Nusselt number increase with increasing value of the Reynolds number. Finally, the simple correlation for the average Nusselt number is obtained in the steady flow regime. © 2012 Curtin University of Technology and John Wiley & Sons, Ltd.

High capacity adsorption of malachite green in a mesoporous tyre‐derived activated carbon

Abstract: A mesoporous activated carbon derived from waste tyres was used to remove a toxic basic dye (malachite green oxalate, or MG) from aqueous solutions. The carbon contains a large volume fraction of mesopores and presents an excellent adsorption capacity of ~424 mg/g towards MG, which is much higher than a commercial carbon with similar surface area. The adsorption equilibrium and kinetics were found to follow Langmuir equation and second-order kinetics, respectively. The structure of the carbon was characterised and based on which the dye adsorption mechanism was discussed. © 2012 Curtin University of Technology and John Wiley & Sons, Ltd.

Adsorption isotherm, kinetic and thermodynamic studies of activated carbon prepared from Garcinia mangostana shell

Abstract: In this study, Garcinia mangostana shell was used to prepare phosphoric acid activated carbon (GMAC). The adsorption studies of the GMAC were carried out using methylene blue as a model dye adsorbate and textile industry effluent. Adsorption studies were conducted in batch mode. Multiple variables affecting adsorption such as contact time, temperature and pH were studied. The optimum conditions for adsorption were found to be contact time of 60 min, temperature 323 K and pH 12. The resultant data were fitted into the Langmuir, Freundlich and Temkin isotherm. The data best fitted the Freundlich model indicating multilayer adsorption onto heterogeneous surface with irregular distribution of adsorption energy and affinity. The rate of adsorption has good correlation with pseudo-second-order kinetics, and diffusion models demonstrate that both film and intraparticle diffusion mechanisms are not the sole rate-limiting step in this particular adsorption. An evaluation of thermodynamic parameters, namely ΔH°, ΔS° and ΔG°, indicates that the adsorption was feasible, spontaneous and endothermic in nature. The low values of ΔH° and ΔG° correspond to physical adsorption. The results reveal that GMAC can be successfully used to remove various types of dye from aqueous solution. © 2013 Curtin University of Technology and John Wiley & Sons, Ltd.

Batch and column removal of copper by modified brown algae sargassum bevanom from aqueous solution

Abstract: The aim of this research work is to investigate sorption characteristics of brown algae Sargassum bevanom (S. bevanom) for the removal of Cu(II) ions from aqueous solutions. The sorption of Cu(II) ions by batch method is carried out. The optimum conditions of biosorption were found to be: a biomass dose of 0.4 g in 100 ml of Cu(II), contact time of 100 min and pH 6, respectively. In optimum condition, removal efficiency was 88.45%. Meanwhile, the maximum adsorption capacity was 73.26 mg g-1. Four equations, i.e. Morris–Weber, Lagergren, Elovich and pseudo second order have been tested to track the kinetics of removal process. The data are well described by pseudo-second-order model. The Langmuir, Freundlich, Temkin and Dubinin–Radushkevic (D–R) are subjected to sorption data to estimate sorption capacity, and the Langmuir shows the high performance in the fitting of equilibrium data. It can be concluded that S. bevanom has potential to remove Cu(II) ions from aqueous solutions at different concentrations. Also, it achieved 75% desorption efficiency using 0.1 M HCl, and reusing of adsorbent shows high ability in the Cu(II) removal from aqueous solution. The removal of Cu(II) by S. bevanom was also investigated in a fixed bed column. Experiments were conducted to study the effect of important parameters such as bed depth (10–20 cm), initial concentration and flow rate (5–15 ml min−1). Meanwhile, the regeneration and reusability of this adsorbent for five cycles was studied. © 2013 Curtin University of Technology and John Wiley & Sons, Ltd.

Rotating zigzag bed as trayed HIGEE and its power consumption

Abstract: High gravity (HIGEE) technology, which uses centrifugal force to intensify mass transfer, has been applied to chemical processing industries. A rotating packed bed is a conventional HIGEE with a rotor filled with packings. A rotating zigzag bed (RZB) is a novel HIGEE with a rotor containing coupled rotational–stationary baffles as discrete steps, which are called HIGEE trays, to provide gas–liquid contact. RZB power consumption is mainly the power requirement for liquid flow. With the ideal liquid flow in an RZB rotor, this study develops a model that can predict the power requirement for ideal liquid flow at zero gas flow. The power requirement for liquid flow is equal to the model-predicted power requirement multiplied by two departure coefficients of real liquid and gas. Experiments were performed in two RZBs by using air–water system, and the consumption with gas rate, liquid rate, and rotational speed was measured. The departure coefficient of real liquid increased with increasing liquid rate and rotational speed, and its value at the greatest liquid rate ranged from 1.14 to 1.28 at various rotational speeds. The departure coefficient of gas increased with increasing gas rate and decreased with increasing liquid rate and rotational speed. The value of the departure coefficient of gas at the greater gas rate ranged from 1.36 to 2.80 at various liquid rates and rotational speeds. The power requirement for liquid flow in RZB was approximately 2.5 times as that of rotating packed bed, so the RZB power consumption should be given more attention. © 2012 Curtin University of Technology and John Wiley & Sons, Ltd.

Experimental study of direct contact steam condensation in structured packing

Abstract: An experimental study of direct contact steam condensation has been conducted at both atmospheric and vacuum pressure, in a pilot scale column filled with Tupac 125Y structured packing. The local volumetric heat transfer coefficient of condensation determined by thermal balance has been given. The influences of the vapor and liquid flow rate, liquid temperature and operation pressure have been investigated. An empirical correlation based on dimensionless numbers has been put forward and verified by various experimental measurements, and the dimensionless numbers were calculated from the Delft hydrodynamic model of structured packing. The results will give some helpful guidance in the design and operation of direct contact condensers with structured packings. © 2013 Curtin University of Technology and John Wiley & Sons, Ltd.

Steady state modeling and simulation of the Oleflex process for isobutane dehydrogenation considering reaction network

Abstract: In this study, the performance of moving bed radial flow reactors in Olefex technology to produce isobutene from isobutane dehydrogenation is studied at steady state condition. The dehydrogenation reactors have been modeled heterogeneously on the basis of the mass and energy governing laws considering a two-dimensional model. In this system, isobutane dehydrogenation, hydrogenolysis, propane dehydrogenation, and coke formation reactions occur on the catalyst surface. The coke deposition on the catalyst surface and the catalyst velocity along the axial direction result to an activity profile along reactors that has been calculated from proper correlation. To prove the accuracy of the considered mathematical model and assumptions, simulation results are compared with the plant data at the same process condition. The isobutane conversion and isobutene selectivity have been obtained at about 38.53% and 90.76%, respectively, which have good agreement with the plant data. © 2013 Curtin University of Technology and John Wiley & Sons, Ltd.

Low‐dimensional modeling of linear heat transfer systems using incremental the proper orthogonal decomposition method

Abstract: In this work, we propose the incremental proper orthogonal decomposition (POD) method and the recursive Galerkin projection to achieve model order reduction (MOR) for high-dimensional dynamical systems arising in the processes of heat transfer for green buildings For MOR of high-dimensional dynamical systems, we use a batch of historic data to initially extract a sequence of POD modes and derive a low-dimensional system to approximate the high-dimensional heat transfer system Then, we check the prediction error at every subsequent sampling moment by using the obtained POD modes If the approximation error is larger than the pre-given threshold value, we then add the new snapshot into the collected sampling ensemble Instead of recalculating the POD-oriented eigenvalue decomposition problem at each ensemble augmentation (which is time-consuming), the incremental POD method applies the updated singular value decomposition approach to increase the number of POD modes and adjust the shape of POD modes, and also change corresponding POD eigenvalues through a matrix rotation transformation © 2012 Curtin University of Technology and John Wiley & Sons, Ltd

Spray and packed liquid–liquid extraction columns: drop size and dispersed phase mass transfer

Abstract: The effects of holdup on Sauter mean drop diameter, D32, and dispersed phase mass transfer coefficient have been studied in the spray and packed extraction columns. For both columns, two well-defined regions for the dependence of D32 on holdup were observed. D32 increased and decreased with an increase in holdup at low and high levels of holdup, respectively. Changes in dispersed phase mass transfer coefficient against holdup were shown to be similar to D32 for both columns. Moreover, empirical correlations have been derived to predict D32 and dispersed phase mass transfer coefficient for both columns. It has been shown that the derived correlations are in a good agreement with the experimental data. © 2013 Curtin University of Technology and John Wiley & Sons, Ltd.

Heat transfer analysis in thermal entrance region under turbulent flow conditions

Abstract: Turbulent heat transfer in the thermal entrance region of the pipe was studied by numerical solution of the energy equation using finite difference technique under different operating conditions. The turbulence effect was accounted for by introducing thermal eddy diffusivity term in the energy equation in both axial and radial directions. The axial and radial temperature profiles, the local heat transfer coefficient in the entrance and fully developed regions, and the entrance lengths were obtained and discussed. In addition, the role of thermal eddy diffusivity in the thermal entrance region and fully developed region was investigated. The finite difference numerical solution was also commented on. The theoretical results were compared with previous experimental works, and a reasonably good agreement was found. It was found that the temperature gradient in axial direction is very steep, close to the leading edge near the pipe's surface and becomes almost negligible after a distance equals few pipe diameters, depending on Reynolds number (Re), Prandtl number (Pr), and heat flux (q). The radial temperature profile was very steep, close to the pipe's surface near the leading edge and becomes almost constant at a very short distance from the pipe surface, depending on Re, Pr, and q. The entrance length (Lt) was found to be reached after 0.5–3.5 pipe diameters distance for the investigated ranges of Re, Pr, and q. Thermal eddy diffusivity plays an important role in axial and radial transport. Ignoring it, causes underestimation in the heat transfer coefficient and overestimation in the entrance length. © 2012 Curtin University of Technology and John Wiley & Sons, Ltd.

Separation of Cd(II) from its aqueous solution using environmentally benign vegetable oil as liquid membrane

Abstract: This work is intended for extraction and recovery of toxic heavy metal components, viz. Cadmium (Cd), from the industrial wastewater using liquid membrane (LM)-based separation technique. Exploring environmental benignity in the solvent (LM) is the main aim of this work. Vegetable oils are potential candidates toward that. Presence of carrier component in solvent often augments the solute transport mechanism. Although N,N-dimethyloctylamine (DMOA) is a very good carrier to show excellent extraction, the recovery is poor possibly because of high stability of complex between Cd(II) and DMOA in the membrane phase. The performance of LM-based separation process is affected by various physical and chemical parameters viz. pH, concentration, stirring rate, temperature, carrier concentration. An optimum operating condition has been identified that would yield the most efficient transport of solute. © 2013 Curtin University of Technology and John Wiley & Sons, Ltd.