Showing papers in "Canadian Journal of Chemical Engineering in 2017"

CO2 reverse water-gas shift reaction on mesoporous M-CeO2 catalysts

Abstract: Mesoporous M-CeO2 (M = Ni, Co, Fe, Mn, and Cu) catalysts were prepared using the hard-template method and applied to investigate CO2 reverse water-gas shift (RWGS) reaction. The physicochemical properties were studied using H2-TPR, XRD, BET, CO2-TPD, and H2-TPD. Results show that the specific surface areas of the prepared Ni-CeO2, Co-CeO2, Fe-CeO2, Mn-CeO2, and Cu-CeO2 catalysts exceed 120 m2/g. CO2 RWGS reaction performances are affected by the d-orbital holes of transition metals. CO2 RWGS reaction catalytic activities are ranked as follows: Ni-CeO2 > Cu-CeO2 > Co-CeO2 > Fe-CeO2 ≈ Mn-CeO2. The Cu-CeO2, Fe-CeO2, and Mn-CeO2 catalysts maintain 100% CO selectivity at the studied temperature. This article is protected by copyright. All rights reserved

Modelling and experimental validation of a CO2 methanation annular cooled fixed‐bed reactor exchanger

Abstract: A simulation model of a fixed-bed reactor exchanger dedicated to CO2 methanation on an industrial Ni/γ-Al2O3 catalyst has been built on the basis of experimental characterization of heat transfer and kinetic parameters. An effective thermal conductivity of the bed and a wall heat transfer coefficient are determined from cooling experiments of different Ar-H2 mixture (thermal conductivity 0.02–0.25 W.m−1.K−1) at different Reynolds number (particle Reynolds number 1–50). The flow dependent component of the Nusselt number correlates to the gas Prandtl number as Pr0.72. These heat transfer parameters and a kinetic model adapted to the Ni/γ-Al2O3 catalyst are integrated in mass, heat, and momentum balance equations in the bed and at the particle scale to build a 2D heterogeneous model of the fixed-bed reactor. CO2 methanation experiments in an annular fixed-bed reactor-exchanger filled with 400 g of Ni/γ-Al2O3 catalyst at pressures from 0.4 to 0.8 MPa and coolant temperatures from 473 to 548 K (200 to 275 °C) are described in this paper and simulated by the model. CO2 conversion rate and CH4 selectivity at the reactor outlet and temperature elevations in the reactor are simulated by the model with a discrepancy lower than 10%. For pressures above 0.4 MPa, a strong mass diffusion limitation inside the catalyst particles is shown and the efficiency decrease of the three reactions is explained. This article is protected by copyright. All rights reserved

Amine-Functionalized CuBTC/poly(ether-b-amide-6) (Pebax® MH 1657) Mixed Matrix Membranes for CO2/CH4 Separation†

Abstract: CuBTC and NH2-CuBTC metal organic frameworks (MOF) were used to produce mixed matrix membranes (MMM) with a block copolymer of poly(ether-b-amide-6) (Pebax® MH 1657) as the polymer matrix to investigate the effect of amine functionalized group (-NH2) on the CO2/CH4 gas separation performance of the MMM. The MOF were fully characterized by XRD, FTIR-ATR, TGA, N2, CO2 and CH4 adsorption, while the MMM were characterized using FTIR-ATR, TGA, DSC and SEM. Permeability and selectivity of the MMM were studied at different MOF mass contents (5 to 20 g/g) and feed pressures (0.3 to 1.5 MPa) for pure and mixed gases. The CO2 permeability for 20 g/g of both Pebax/CuBTC and Pebax/NH2-CuBTC MMMs was nearly twice of the neat polymeric membrane, while the presence of amine functionalized group in NH2-CuBTC produced an increasing trend of CO2/CH4 ideal selectivity at high NH2-CuBTC loading and about 60% increase was observed at 20 g/g of NH2-CuBTC. This article is protected by copyright. All rights reserved

Towards a unified approach for modelling uniform and non-uniform bubbly flows

Abstract: An important ingredient of closure relations for the Euler-Euler two-fluid model is the description of turbulent fluctuations. Models proposed in the literature disagree concerning the treatment of such on all scales. The large scale fluctuation structures as well as the bubble induced turbulence might be neglected or resolved and/or modeled respectively in different ways. Each treatment has been demonstrated to work for a certain application but a unifying perspective is lacking so far. To this end a set of closure relations for the fluid dynamics of bubbly flow has been collected that represents the best available knowledge and may serve as a baseline for further improvements and extensions. This model comprises a set of bubble forces as well as a turbulence model including turbulence modification due to the bubbles and has been successfully validated for bubbly flows in pipes and bubble columns. Here it is applied to two sets of data representing non-uniform and uniform flows in bubble columns which are dominated by large scale fluctuations and bubble induced turbulence respectively. This article is protected by copyright. All rights reserved

Pressurized liquid extraction of oil from soybean seeds

Abstract: The aim of this study was to investigate the extraction of soybean oil using ethanol under pressurized conditions. The effects of pressure (10 and 20 MPa), temperature (30 to 90 °C) and solvent flow (1 and 3 mL/min) were evaluated applying different extraction times. In addition, the thermodynamics parameters of the process were determined. It was observed that the pressure exerted no influence on the extraction kinetics, while an increase in temperature promoted better yields. The use of the highest solvent flow increased the initial extraction rate, but did not influence the yield under equilibrium conditions. Based on the thermodynamic parameters, the extraction was classified as endothermic (44.11 kJ/mol), irreversible (143.52 J/mol K) and partially spontaneous (0.60 to −8.01 kJ/mol), and an increase in the temperature favoured this spontaneity. Extraction using the classical Soxhlet method was evaluated for comparison purposes using ethanol and n-hexane as solvents and ethanol showed a better extraction efficiency. The maximum yield obtained with pressurized liquid extraction (PLE) was 24.42%, which represents ∼94% of the yield obtained by classical extraction. Linoleic and oleic acids were the main fatty acids identified in the soybean oil, representing ∼76% of the fatty acids composition, which was not influenced by the extraction method or the temperature used in the PLE. This article is protected by copyright. All rights reserved

Advanced treatment of actual textile dye wastewater by Fenton‐flocculation process

Abstract: To improve the performance of actual textile dye wastewater treatment, an advanced treatment combining the Fenton and flocculation processes was developed. The parameters affecting decolorization in the Fenton-flocculation process, including initial pH, H2O2 dosage, Fe2+dosage, reaction temperature, reaction time, and flocculant dosage, were examined. With the optimal Fenton-flocculation condition parameters, more than 95 % COD removal, 99 % colour removal, and 99 % turbidity removal were obtained. UV-visible spectra of raw water and supernatant were further obtained after the Fenton-flocculation process, and results demonstrated that the chromophoric groups and the conjugated system in the dye molecular structure were destroyed. All these results confirmed that the Fenton-flocculation process was a favourable and effective post-treatment method for actual textile dye wastewater.

Microencapsulation of astaxanthin in alginate using modified emulsion technology: Preparation, characterization and cytostatic activity

Abstract: In the present study, astaxanthin was microencapsulated in a biodegradable material, calcium alginate, using a modified emulsion technology developed at our laboratory. The modified emulsion method involves the reaction between a sodium alginate emulsion and a calcium chloride emulsion. After mixing these emulsions, Ca2+ penetrates two oil-water layers to combine −COO-, and microparticles are formed with narrow size distribution and good dispersion due to the mild reaction speed. The microencapsulated astaxanthin showed much higher storage stability and antioxidant activity than the non-encapsulated astaxanthin. Cytostatic activity was preliminarily evaluated on adipose-derived stem cells, the microencapsulated astaxanthin showed significant cytostatic activity due to the improved solubility of astaxanthin caused by the good biocompatibility of calcium alginate. Characterization confirmed the existence of microparticles with high encapsulation efficiency (more than 85 %), uniform size distribution (1.61 µm), and sustained astaxanthin release, suggesting the prepared microparticles by the modified emulsion method have great potential in pharmaceutical, food, and cosmetic industries.

Dual polymer flocculants for mature fine tailings dewatering

Abstract: A cationic polymer, polydiallyldimethylammonium chloride (polyDADMAC), and an anionic (hydrolyzed) polyacrylamide (PAM), were used in sequence to treat the mature fine tailings (MFT) from the oil sands operations in Alberta, Canada. Capillary suction time (CST), specific resistance to filtration (SRF), and filter cake solid content were measured, and cryogenic scanning electron microscopic (cryo-SEM) images of the MFT were taken, before and after the dual polymer treatment to evaluate the dewaterability of the MFT. The results were compared with treatment by a single polymer, which demonstrated that the dual polymer treatment resulted in improved dewaterability of the MFT due to the larger pore sizes.

Numerical investigation of two phase flow in micromodel porous media: Effects of wettability, heterogeneity, and viscosity

Abstract: The aim of the present work is to assess the effects of wettability, heterogeneity, and viscosity differences on water-oil displacement process in micromodel porous media through numerical modelling. The two-phase flow was simulated by Cahn-Hilliard phase field method (PFM) using a finite element package. The micromodel was initially saturated with oil (wetting phase) and oil was produced through invasion of the displacing phase into the matrix. The computed oil and water saturations were in good agreement with those obtained by the visual flooding experiment. Using the validated model, sensitivity analysis was performed to investigate the effects of different wettability states, heterogeneity, and viscosity on the displacement process. The obtained results showed that the final oil saturation of the homogeneous pattern is 0.37 which is 13 % less than that of the heterogeneous one. For the highly oil-wet medium (θc=2π/3), the capillary forces prevented water to invade more pore bodies and resulted in 0.62 ultimate oil saturation; however, the final oil saturation in the neutral wet (θc=π/2) was ∼0.5. Increasing the viscosity of displacing agent formed lower channelling and fingering which led to higher oil recovery due to the favourable mobility ratio. The present study demonstrates that PFM can be a reliable approach to capture micro- and macro-scale mechanisms in the simulation of immiscible two-phase flow in micromodel porous media with a reasonable computational time.

Semiparametric PCA and bayesian network based process fault diagnosis technique

Abstract: Semiparametric Principal Component Analysis has advantages over Principal Component Analysis (PCA), as it can deal with nonlinear and non-monotonic correlation and non-Gaussian distribution process data. In Semiparametric PCA the distance correlation coefficient matrix is used to replace the covariance matrix, and a semi-parametric Gaussian transformation is used to allow variables to follow multivariate Gaussian distribution. To reduce the cost of monitoring and alarm flooding, a fault diagnosis technique, which combines Semiparametric PCA and Bayesian Network (BN), is proposed here. In the first stage, Semiparametric PCA is used to find the fault in monitored variables. Considering the interaction of process variables and historical process data, a Bayesian network is developed in the second stage. Considering Semiparametric PCA outcome as evidence, the Bayesian network applies deductive and abductive reasoning to update and analysis, which assist in determining the true root cause(s) and fault propagation pathway. The implementation and applicability of the proposed methodology are demonstrated using three process systems.

Removal of nickel ions on residue of alginate extraction from Sargassum filipendula seaweed in packed bed

Abstract: The residue of the alginate extraction, which has been shown as a good alternative material in the removal of toxic metals from industrial wastewater, is little explored as a biosorbent material. This study evaluated the removal of nickel ion in a fixed bed onto the residue of alginate extraction from Sargassum filipendula seaweed. The biosorption process in a dynamic fixed-bed system evaluated the influence of flow rate and feed concentration, by mass transfer zone (MTZ) and the total removal percentage (%Remt). In order to assess the metal recovery potential and the lifetime of the column, two cycles of adsorption/desorption were performed. The continuous adsorption process was simulated using different dynamic models such as Bohart and Adams, Clark, Thomas, Yan et al., and Yoon and Nelson models. The best predictive model was Yan et al. Techniques, such as Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy coupled with energy dispersive X-ray (SEM-EDX), helium gas picnometry, mercury porosimetry, and N2 physisorption (BET) were performed in order to compare the residue before adsorption with the material after the process. The results showed that the residue can be used to treat toxic metal contaminated effluents by biosorption processes efficiently.

Nanosize effects of NiO nanosorbcats on adsorption and catalytic thermo‐oxidative decomposition of vacuum residue asphaltenes

Abstract: The nanosize effects of NiO nanosorbcats on adsorption and post-adsorption catalytic thermo-oxidative decomposition of vacuum residue (VR) n-C5 asphaltenes was investigated using a UV-vis spectrophotometer and thermogravimetric analyzer coupled with a mass spectrometer and presented in this study. Sizes between 5 and 80 nm of different-sized NiO nanosorbcats were employed. Batch adsorption experiments were carried out for the considered asphaltenes in toluene solutions, monitored via UV-vis spectrophotometry. The macroscopic adsorption isotherms were described by implementing the solid-liquid equilibrium (SLE) model. The findings showed that thermally cracked vacuum residue (VR) n-C5 asphaltenes interact to different extents with different-sized NiO nanosorbcats. A normalized surface area basis was used for the amount of VR n-C5 asphaltene adsorbed per nm2 of NiO surface, which was the highest for NiO nanoparticles of size 80 nm, with 5 nm size being the lowest. Thermogravimetric analysis of VR n-C5 asphaltenes was also achieved and the reaction products were explored by a mass spectrometer. The Kissinger-Akahira-Sunose (KAS) isoconversional model was used to describe the reaction mechanism and to confirm the validity of the catalytic role of the different particle sizes of NiO nanosorbcats. The highest catalytic activity was for smallest NiO when compared to the highest NiO nanosorbcats. Furthermore, the results of thermodynamic transition state parameters of activation; changes in Gibbs free energy (ΔG‡), entropy (ΔS‡), and enthalpy (ΔH‡) highlighted the catalytic activity of NiO nanosorbcats towards VR n-C5 asphaltenes oxidation. These findings exhibit the significance of textural properties and nanosize of nanoparticles during adsorption and thermal catalytic processing of asphaltenes. This article is protected by copyright. All rights reserved

Enhanced polymer flooding using a novel nano‐scale smart polymer: Experimental investigation

Abstract: Polymer flooding is a well-known commercial method among enhanced oil recovery (EOR) methods. Despite its successful development, this method could still be improved considerably by utilizing new polymeric materials and systems. The main objective of this study is the implementation of smart-covered polymer particles (SCPP) prepared by multistep inverse emulsion polymerization, to improve polymer flooding efficiency. Successive to the average molecular weight determination of the core polymer using the dilute solution method, the dissolution behaviour of SCPPs is examined at reservoir temperature in a specific setup. In addition to investigating the efficiency of SCPP flooding, polymer flooding experiments in a micromodel setup are examined. The flooding efficiency of conventional polyacrylamide and the newly developed SCPP solutions are compared with the water flooding process. Our results provide new insight in the ability of coated polymers to enhance the recovery efficiency of polymer flooding processes. This article is protected by copyright. All rights reserved

Flow characteristics and wear prediction of Herschel-Bulkley non-Newtonian paste backfill in pipe elbows

Abstract: Backfill process has become standard practice in mining industry where the backfill slurry is transported from surface to underground via pipeline system. Paste backfill is one of the types of backfill slurries which in recent years has gained popularity due to its reduced water content, fast solidification time and it's environmentally friendly reputation. However, wear and erosion of the pipe have been a major issue in some paste backfill pipeline operations. Paste backfill behaves as a non-Newtonian fluid and can be modelled as a Herschel-Bulkley fluid. To better understand the flow behaviour and wear rate of paste backfill in underground pipeline system, experimental and numerical studies were carried out. The former focuses on the slump test and L-pipe flow test to characterize paste backfill properties, while the latter aims to develop three dimensional mathematical model to evaluate flow and wear characteristics in pipe elbows. To ensure robust and accurate solutions, the model was verified with analytical solutions and validated against experimental data. The numerical results suggest that elbow design and paste backfill property significantly affect secondary flow generation which is further reflected in the pipe wear rate. Thicker paste backfill slurry flowing in 5D elbow yields the lowest wear rate which is beneficial for practical application, albeit it comes at higher pressure drop. This article is protected by copyright. All rights reserved

Hydrophilic zeolite sorbents for In‐situ water removal in high temperature processes

Abstract: An attractive approach to reduce anthropogenic emission of carbon dioxide (CO2) would be to valorize it into added-value products (e.g. alcohols or dimethylether) by chemical recycling. However, in most of these important reactions, water is produced as a by-product that limits CO2 conversion thermodynamically and can lead to the deactivation of catalysts. Water removal in sorption-enhanced reaction process (SERP) would allow the overcoming of these drawbacks and several zeolites (SOD, LTA, and FAU) have been selected to assess their potential to adsorb water in-situ at high temperature. This work aims to study the water adsorption capacity and kinetics in a large temperature range of 25–250 °C and evaluate the potential of the selected adsorbents for in-situ water removal in the reverse water gas shift (RWGS) reaction. For all zeolites, the water uptake showed an important decrease at higher temperatures but the capacity at 250 °C was still significant. While the poor adsorption kinetics of SOD limit its use, FAU-13X powder gave better results than LTA-4A, which were confirmed by a more important increase of CO concentration at the exit of the reactor for the RWGS reaction. Transient adsorption data obtained in this study were fitted by a double stretched equation and the kinetic constants were determined. These results are essential to model and design an efficient SERP process and determine the optimal reaction conditions. This article is protected by copyright. All rights reserved

Effective treatment of high phosphorus pharmaceutical wastewater by chemical precipitation

Abstract: The conditions for the treatment of high phosphorus pharmaceutical wastewater using chemical precipitation were determined to achieve high efficiency on the removal of total phosphorus (TP). The key factors affecting the TP removal efficiencies of four metal salts (FeCl3, AlCl3, MgCl2, and CaCl2), such as molar ratio, initial wastewater pH, and reaction time, were investigated. The optimal metal mole ratios of FeCl3, AlCl3P, MgCl2, and CaCl2 for the TP removal were 1.8:1, 1.8:1, 1.6:1, and 1.6:1 in the initial pH range, respectively. The TP removal efficiencies obtained by FeCl3, AlCl3, MgCl2, and CaCl2 were 99.8%, 98.3%, 96.9%, and 99.2% at the optimal mole ratio and pH conditions with 30 min reaction time, respectively. FeCl3 and AlCl3 had better removal performance on COD, wherein the removal rates of COD by FeCl3 and AlCl3 were 38.6% and 27.6%, respectively. FeCl3 and CaCl2 were selected for the combined process of removing TP and overcoming the aforementioned problem. The final effluent quality was better than the one only used on one of the four metal salts, in which the removal rates of TP and COD were as high as 99.8% and 46.9%, respectively. The combined process with FeCl3 and CaCl2 was an effective method for the pretreatment of high phosphorus pharmaceutical wastewater to reduce the processing cost and to decrease the chemical oxygen demand (COD) and TP. This article is protected by copyright. All rights reserved

An effective fault diagnosis approach based on optimal weighted least squares support vector machine

Abstract: Fault diagnosis is always a vital technology in the chemical industry and is influenced by a large number of process variables in the practical manufacturing process. Thus, an effective diagnosis method is crucial in practical chemical process. A novel fault diagnosis method is proposed based on the weighted least squares support vector machine (WLSVM) to deal with the small sample and non-linear partition data. It provides the strong potential in predicting faults, especially by further employing a suitable particle swarm optimization (PSO) algorithm to determine the most important parameters of the punishment factor and the Gaussian RBF kernel, which has the advantages of high accuracy and low false alarm rate. PSO-WLSSVM is further accomplished with the data from a classic benchmark test set TE process. Also, the models SVM, PSO-SVM, and PSO-LSSVM are employed on the TE process to compare the performance of PSO-WLSSVM. The results show the validity of the proposed approach on the TE process. This article is protected by copyright. All rights reserved

Ethylene production from diluted bioethanol solutions

Abstract: Ethylene production by ethanol dehydration has been investigated over a set of zeolites with BEA structure in acidic form (HAlBEA). The effect on Ni addition (up to 0.03 g/g (3 mass%)) is explored as a means to improve ethylene selectivity limiting the formation of heavier byproducts. The reaction temperature has been varied between 300 and 500 °C and the effect of cofeeding water has been also explored. Both an increase of the operating temperature and of the water/ethanol ratio can improve stability of coking and thus catalyst life. The use of diluted bioethanol solutions was shown to be beneficial for catalyst stability. The effect of possible impurities present in less purified raw materials was also checked by testing two diluted second generation bioethanol solutions (0.5 and 0.9 g/g (50 and 90 mass%)). A first reactor layout and the integration with the bioethanol purification strategy are also proposed, including two purification options which are much less energy demanding than traditional rectification.

Explicit Frost-Kalkwarf type equations for calculation of vapour pressure of liquids from triple to critical point by the Adomian decomposition method†

Abstract: The general form of explicit, analytical solution of the Frost-Kalkwarf equation was developed for the first time by means of the Adomian decomposition method as a reliable mathematical tool. The accuracy of the obtained formulas was further improved by applying the diagonal Pade approximants. We have demonstrated that our developed formulas are at least 30 times faster than the original Frost-Kalkwarf equation in computation of vapour pressures and are highly accurate with an overall absolute relative deviation of 2.25% for 88 different substances over 26 400 experimental data points from triple to critical point temperatures. As another unique advantage, our formulas avoid any divergent behaviour in using iterative methods unlike the implicit Frost-Kalkwarf equation. Based on the conducted statistical analyses, our formulas have excellent predictability of vapour pressure values with a probability of 90.33% for absolute relative errors of less than 5%. This article is protected by copyright. All rights reserved

Gas holdup, bubble behaviour, and mass transfer characteristics in a two‐stage internal loop airlift reactor with different screens

Abstract: Screen internals were used in a two-dimensional two-stage internal loop airlift reactor (ILALR). The influence of screens on the hydrodynamics and mass transfer characteristics in the two-stage ILALR, including gas holdup, mean bubble diameter, bubble rise velocity, and volumetric mass transfer coefficient (KLa), have been experimentally investigated. It is found that screens can efficiently break bubbles up. Radial bubble velocity distribution is more uniform when screens are installed. Mean bubble diameter with smaller screen pores seems smaller and slightly increases with the increasing of superficial gas velocity Ug. A larger gas holdup and KLa can be obtained when a suitable screen is mounted. The variation trend of overall gas holdup and interfacial area a with Ug is similar. A nearly constant liquid-side mass transfer coefficient (KL) is found. The empirical correlations for the overall gas holdup and KLa have been proposed, which fit the experimental data well.

Shear‐induced aggregation of colloidal particles: A comparison between two different approaches to the modelling of colloidal interactions

Abstract: Several methods have been proposed to investigate the dynamics of processes including aggregation and breakup of colloidal particles. Most approaches resort to Population Balance Equations, frequently solved in a stochastic way (Monte Carlo simulations). These methods have a relatively low computational cost, but they are not completely predictive, since they need proper models for the description of the rates of aggregation and breakup. On the contrary, highly accurate and fully predictive description of single aggregation or breakup events can be obtained by Discrete Element Methods (DEMs), in which the motion of each primary particle of an aggregate is tracked by solving its equation of motion. However, so far, the high computational cost of DEMs has restricted their use to the simulation of short sequences of events, thus hindering their application to representative samples of a population of aggregates. The present work aims to investigate the shear-induced aggregation of a large population of aggregates suspended in an aqueous medium. We developed a method which combines a Monte Carlo approach to determine the sequence of aggregation and breakup events and a Discrete Element Method, built in the framework of Stokesian Dynamics, to accurately reproduce them. The DEM is able, in fact, to rigorously evaluate the fluid-dynamic stresses acting on each monomer and to model properly the colloidal interactions. Two different models were used to describe the colloidal interaction between primary particles and their effect on the aggregation behavior was analysed. Results highlighted that aggregation kinetics, size distributions and typical morphology are significantly influenced by the approach used to model colloidal interactions. This study demonstrates that the combination of a Monte Carlo approach with a DEM model represents a powerful tool for the study of the dynamics of a large population of colloidal aggregates

Effect of distributor on fluidized bed hydrodynamics

Abstract: In this work, the effect of distributor type on fluidized bed hydrodynamics was studied by taking into account time, frequency, and state space domains. For this purpose, pressure fluctuations were measured in a fluidized bed with 0.15 m diameter and the experiments were carried out for three different types of distributors (perforated plate, bubble cap, and porous plate) at different sizes and various superficial gas velocities and particle sizes. Time domain analysis demonstrated that while the initial bubble size on the bubble cap distributor is greater than that on the perforated plate, the standard deviation of pressure fluctuations is greatest in a bed equipped with the porous plate, followed by the perforated plate and then the bubble cap distributor. Based on the current analysis and in view of the frequency domain analysis, it was found that the contribution of finer structures (small bubbles and clusters) is highest for a porous plate, followed by a bubble cap and then a perforated plate distributor. Also, according to the S-statistic method, it was concluded that the S-test is a reliable method for detection of differences between hydrodynamic situations of fluidized beds, while different types of distributors were used.

Hydrodynamic difference between inline and batch operation of a rotor-stator mixer head - A CFD approach

Abstract: Rotor-stator mixers (RSMs) can be operated in either batch or inline mode. When operating a rotor-stator geometry in batch mode, it typically experiences an order of magnitude higher volumetric flow through the stator than in inline mode. This is expected to cause differences in the flow and turbulence in the rotor-stator region. This study uses computational fluid dynamics (CFD) to study the hydrodynamic differences in and near the stator hole as a function of volumetric flow rates between those experienced in inline and batch modes of operation. It is concluded that both radial flow profiles and turbulent kinetic energy across a range of rotor speeds and flow rates can be described by a velocity ratio: average tangential fluid velocity in the stator hole divided by the rotor tip speed. Moreover, the position where dissipation of turbulent kinetic energy takes place—and hence the effective region of dispersion or mixing—differs between the two modes of operation. The relative importance of the two regions can be described in terms of the velocity ratio and the transition can be predicted based on the relative power input due to rotational and pumping power of the mixer. This study provides a starting point for understanding differences between emulsification efficiency between inline and batch modes of operation with relevance for both equipment design and process scale-up. (Less)

Multimode non‐Gaussian process monitoring based on local entropy independent component analysis

Abstract: Traditionally, independent component analysis (ICA) as a multivariate statistical process monitoring (MSPM) method has attracted considerable attention due to its excellent ability in analysis of non-Gaussian data sets. However, it may degrade fault detection performance for multimode operating process because of its assumption of one single steady mode. In order to supervise the non-Gaussian process with multiple steady modes more effectively, this paper proposes a process monitoring method based on local entropy independent component analysis (LEICA). This method applies local probability density estimation to remove the effects of multimode characteristics. Furthermore, information entropy theory is used to extract the feature information of process data by calculating their local information entropies. Based on these local entropy data, ICA is applied to establish the local entropy component model for fault detection. Lastly, a numerical example and the Tennessee Eastman (TE) process are used to verify the proposed method and the results demonstrate the superiority of LEICA method. This article is protected by copyright. All rights reserved

Effect of heating process on the wettability of fine coals of various ranks

Abstract: Spontaneous coal combustion can produce a condition of heating process because the atmosphere of coal underground is usually poor in oxygen. Even though the spontaneous combustion of coal is prevented by people, the surface properties of coal are greatly changed. The changes in the wettability of coal influence the flotation of fine coals. This paper investigates the effect of the heating process on the wettability of fine coals of various ranks. Lignite, bituminous, and anthracite coals were used as experimental samples. The heating temperature and time were 500 °C and 2 h. X-ray photoelectron spectroscopy (XPS) and contact angle measurements were used to indicate the changes in wettability of fine coals before and after the heating process. The results showed that the wettability of bituminous coal was significantly increased whereas that of lignite was greatly decreased after the heating process. However, the wettability of anthracite coal was increased only a little after the heating process. This article is protected by copyright. All rights reserved

Determination of CO2 storage density in a partially water‐saturated lab reservoir containing CH4 from injection of captured flue gas by gas hydrate crystallization

Abstract: It has been demonstrated that CO2 storage in depleted natural gas reservoir at gas hydrate formation conditions is an opportunity to mitigate the emission of CO2 from fossil fuel combustion or gasification sources. More than 100 depleted natural gas reservoirs located in Alberta, Canada were investigated and recognized as potential sites for CO2 storage using hydrate technology. Treated flue gas captured from large stationary sources is generally a gas mixture of CO2 with N2, O2 and other impurities. The depleted gas reservoirs still contain natural gas that was not economically recoverable. In this work CO2 and a CO2/N2 (90/10 mol %) gas mixture were used for injection in a laboratory reservoir that contained residual CH4. The experimental results indicated that about 80% of the original water in the reservoir formed CO2 hydrate after 120 h. The total CO2 storage density (in hydrate, gaseous and dissolved state) from the injection of the CO2/N2 mixture into a 500 kPa CH4 reservoir was found to be 118.6 kg/m3. The addition of certain amount of tapioca starch in the reservoir delayed the onset of nucleation and improved the CO2 storage density (121 kg/m3). This storage density may also be achieved by compressing the gaseous CO2/N2 mixture to 5220 kPa at 285 K. This study shows that hydrate technology provides more CO2 storage density than other storage methods or same storage but at much lower compression costs. This article is protected by copyright. All rights reserved

Trimetallic Au‐Cu‐K/AC for acetylene hydrochlorination

Abstract: The metal chloride of KCl was chosen to modify Au-Cu/AC to decrease the noble metal of gold and enhance the catalytic performance. Then a mercury-free catalyst of Au-Cu-K/AC was prepared by the impregnation method. The catalytic performances of mercury-free catalyst for acetylene hydrochlorination were conducted for 1600 h in a fixed bed reactor by a single-tube pilot unit. The fresh and used catalysts were also characterized in comparison. The results showed that the acetylene conversion on mercury-free catalyst decreased slowly from 98 % to 89 %, and the vinyl chloride monomer (VCM) selectivity was kept at 99.7 % under reaction conditions of temperature 165 °C, gas hourly space velocity (GHSV) 40 h−1, and feed volume ratio of HCl to C2H2 of 1.05 during 1600 h on stream. The results showed that the additives of K with Cu can make the active species of gold dispersed well and retard the aggregation of particles. The reason for the slow decline of acetylene conversion for Au-Cu-K/AC catalyst was the whisker carbon deposition, shown in a faint yellow colour over the catalyst surface, which consisted of short-chain hydrocarbon molecules. Further study for accelerated deactivation of sole metal in the catalyst gives the clues that the non-noble metal of Cu in Au-Cu-K/AC catalyst plays a key role to form the deposition.