Showing papers in "Chemical Engineering Research & Design in 2016"

A review of the kinetics adsorption models and their application to the adsorption of lead by an activated carbon

Abstract: 10 kinetic models are studied in detail and used after to model the adsorption kinetics of lead on an activated carbon. All the kinetics parameters are determined: coefficients of diffusion, rate constants and maximum lead adsorption, then, compared to the literature data. The data are better simulated by the nonlinear models in the order: simplified Elovich > Elovich > Bangham > pseudo order n > Boyd, Crank long times > pseudo order 2 > Crank > Weber and Morris > Langmuir, pseudo order 1 > pore volume and surface diffusion model by Leyva Ramos > simplified Crank short times. It is one of the first times that the kinetics of adsorption are fitted by the entire true Crank model. The kinetics of lead adsorption by the activated carbon are best described by the Elovich equation: Q = 1 / β Ln α β t with α equal to 0.035 mg g −1 s −1 and β to 0.134 g mg −1 .

Computer-aided molecular design: An introduction and review of tools, applications, and solution techniques

Abstract: This article provides an introduction to and review of the field of computer-aided molecular design (CAMD). It is intended to be approachable for the absolute beginner as well as useful to the seasoned CAMD practitioner. We begin by discussing various quantitative structure–property relationships (QSPRs) which have been demonstrated to work well with CAMD problems. The methods discussed in this article are (1) group contribution methods, (2) topological indices, and (3) signature descriptors. Next, we present general optimization formulations for various forms of the CAMD problem. Common design constraints are discussed and structural feasibility constraints are provided for the three types of QSPRs addressed. We then detail useful techniques for approaching CAMD optimization problems, including decomposition methods, heuristic approaches, and mathematical programming strategies. Finally, we discuss many applications that have been addressed using CAMD.

Life cycle assessment of future electric and hybrid vehicles: A cradle-to-grave systems engineering approach

Abstract: Electric mobility is playing an important and growing role in the context of sustainable transport sector development. This study presents the life cycle assessment of an electric car based on the technology of Lithium-ion battery (BEV) for Europe and compares it to an internal combustion engine vehicle (ICEV). According to a cradle-to-grave approach, manufacturing, use and disposal phases of both vehicles have been included in the assessment in order to identify the hot spots of the entire life cycles. For electric vehicles two manufacturing inventories have been analysed and different vehicle disposal pathways have also been considered. Furthermore, the environmental performances of hybrid vehicles have been analysed based on the life cycle models of the BEV and ICEV. The results of the hot spot analysis showed that the BEV manufacturing phase determined the highest environmental burdens mainly in the toxicity categories as a result of the use of metals in the battery pack. However, the greenhouse gas emissions associated with the BEV use phase were shown to be half than those recorded for the ICEV use phase. The trend of the results has also been investigated for future energy mixes: the electricity and diesel mixes for the year 2050 have been considered for the modelling of the use phase of BEV and ICEV.

A review on removal of elemental mercury from flue gas using advanced oxidation process: Chemistry and process

Abstract: Mercury emission from combustion sources has become a great public concern due to its hazards for human health and ecosystem. Although a large number of Hg 0 removal technologies already have been developed, none of them can obtain large-scale applications due to various technical and economic issues. Therefore, more efforts are needed to develop cost-effective Hg 0 removal technologies. Advanced oxidation technologies (AOTs) are defined as those technologies that can generate mainly the hydroxyl radical (OH) with high oxidation potential and other reactive oxygen species including superoxide anion radical (O 2 − ), hydrogen peroxide (H 2 O 2 ) and singlet oxygen, by various environmentally benign physical or chemical processes. In the past two decades, AOTs have gained an extensive attention research and successful applications in water treatment and soil remediation, as well as in flue gas purification for multipollutant treatment. In recent years, an increasing attention has been paid to the removal of Hg 0 in flue gas using AOTs due to the excellent prospects of this technology. To date, the four main AOTs for removing Hg 0 in flue gas include plasma AOTs, TiO 2 photocatalytic AOTs, photochemical AOTs and activated oxidant AOTs. While these AOTs have shown excellent prospects for removing Hg 0 in flue gas, a number of technical issues need to be resolved before they are amenable to industrial applications. This article provides the first comprehensive review of the progress and recent developments of these four AOTs for removing Hg 0 in flue gas, with emphasis on the chemistry and processes involved. The effects of the main flue gas components and process parameters on Hg 0 removal using these AOTs are summarized. The reaction products, mechanism, kinetics, reactor types and process flow systems, and impacts on of Hg 0 removal are also comprehensively reviewed, with insights into the challenges for large-scale applications. This review is intended to advance our understanding and outline directions for future developments of this research field.

Experimental investigation of CO2 huff-n-puff process for enhancing oil recovery in tight reservoirs

Abstract: Due to the feature of tight formation, the primary oil recovery is usually very low and leaves substantial oil still in place. This fact results in a strong motivation of applying an enhancing oil recovery (EOR) method to further increase the oil recovery. In the present work, CO 2 huff-n-puff process as a potential EOR method for tight oils was experimentally investigated in 0.3 md cores. The visual tests proved that the oil swelling factor and CO 2 solubility increased with pressure. The core tests indicated that CO 2 huff-puff process is a viable technique to promote tight oil recovery. The magnitude of oil recovery is strongly dependent on CO 2 pressure, the oil recovery can reach 30.9% at 16 MPa in our experiment. Compared multi- to single-cyclic operation, the oil recovery is further increased by 10% by a four-cycle operation. However, after two cycles, the oil recovery significantly dropped. Differential production pressure (ΔP) is the dominant parameter for tight oil recovery in CO 2 huff-puff process. This work is supposed to provide some necessary clues for pilot design.

Experimental study of nanoparticle-surfactant-stabilized CO2 foam: Stability and mobility control

Abstract: CO 2 injection has proved to be the most common and efficient enhanced oil recovery techniques which leads to more residual oil recovery. Unfavorable sweep efficiency which results in fingering propagation and causes early gas breakthrough is the most challenging issue of gas flooding process. The aim of this work is to study foam stability and analyze the mobility of CO 2 foam stabilized by mixture of raw silica nanoparticles and ethyl hexadecyl dimethyl ammonium bromide (cationic surfactant). The result is obtained through both dynamic and static techniques using a new adsorption index. NPS-stabilized foams are generated using Ross-Miles method. A novel index for the adsorption of surfactant molecules on the nanoparticles is proposed using electrical conductivity measurement. Analyzing the foam decay behavior based on this adsorption index, it is found that the foam life can be divided into two general regions. First, low adsorption region that the foam stability is initially dominated by surfactant concentration and after a while it is controlled by nanoparticles. Second, high adsorption region, that the foam stability, is mostly affected by both nanoparticles and surfactant concentrations as well. The pressure behavior and morphology of the foam are investigated using dynamic characterization apparatus. By using a capillary viscometer in this apparatus, foam apparent viscosity is measured for different phase ratios, and nanoparticle and surfactant concentrations. It is observed that NPS solutions produce uniformly smaller foams with higher apparent viscosity compared to those with surfactant solutions. The results reveal that in different surfactant concentrations, the apparent viscosity of NPS-stabilized foam experiences a maximum value of 6.03 cp which is about 9 times larger than that of CO 2 /water dispersion flood. This maximum is coincided with the maximum adsorption index and the maximum hydrophobicity.

Review on hydrodynamics and mass transfer in minichannel wall reactors with gas-liquid Taylor flow

Abstract: Over the past decades, Taylor flow has got an increasing interest due to its potential to intensify reaction processes with fast kinetics which are usually controlled by mass transfer processes. Besides high mass transfer rates, the segmented flow regime offers a sharp residence time distribution of the liquid phase and a low pressure drop. Taylor flow appears in micro and minichannels whereas the terms have not always been used with a clear distinction. Minichannels are channels with characteristic diameters between 400 μm and about 1 mm, which will be in the centre of this work. These channel dimensions appear in monolithic reactors also known as reactors with honeycomb catalyst packings, in concepts using bundles of capillary tubes, as well as in microchannel plate reactors. This article presents a comprehensive overview of hydrodynamics and mass transfer in the minichannels of an open flow structure, i.e. in channels without internals, operated in the Taylor flow regime. The review summarises available correlations to predict Taylor flow characteristics, as well as mass transfer coefficients between all involved phases (gas–liquid, liquid–solid, gas–solid). Within this scope, the impact of operational and design parameters is critically discussed and limits of application for the individual correlations are defined. Special attention is given to the interaction of these mass transfer steps in heterogeneously catalysed chemical reactions.

Effect of the reduction degree of graphene oxide on the adsorption of Bisphenol A

Abstract: Graphite oxide (GO) was reduced to different reduction degrees by using hydrazine hydrate and finally to graphene using NH4OH. The obtained materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), nitrogen adsorption (BET), Fourier transform infrared spectroscopy (FTIR) and potentiometric titration measurements. Their adsorption performance for Bisphenol A (BPA) was evaluated taking into account pH, ionic strength, kinetics initial ion concentration and thermodynamics of adsorption. The adsorption capacities were increased with increasing the reduction degree of GO with the maximum adsorption capacity (Qmax = 94.06 mg/g) to be presented by Graphene that was the result of the optimum reduction degree. The adsorption followed pseudo-second order kinetics and the thermodynamic analysis indicated that it was spontaneous and endothermic. The increase in the degree of GO reduction reduced the amount of oxygen-containing functional groups on the surface of reduced samples, resulting to the increase of the π–π interaction between sorbent–adsorbate and to linear increase of adsorption capacity.

A review of integrated supply chain network design models: Key issues for vaccine supply chains

Abstract: In general, vaccines are recognized as an important means to protect populations against infectious diseases. We show that vaccines do not behave like commodity goods and elaborate on the key issues for vaccine supply chain design. This paper reviews the literature on model-based supply chain network design in order to identify the applicability of these models to the key issues of the design of a vaccine supply chain. We study whether the decisions at strategic, tactical and operational levels of the reviewed literature are able to address vaccine supply chain key issues as limited shelf life, cold chain distribution and accessing remote areas. Furthermore, we provide an overview of how uncertainty is incorporated in the reviewed literature and is able to incorporate disease epidemics, tender procurement, lead time variability and demand variability. Our future vaccine supply chain network needs to be sustainable, hereby taking the preferences of different stakeholders into account for obtaining a set of economical, technological and value key performance indicators that need to be satisfied by the design. Finally, we discuss the real-life applicability of the research up to now and discuss similarities and dissimilarities of vaccine supply chains with other pharmaceutical supply chains.

Algae derived biodiesel using nanocatalytic transesterification process

Abstract: This work investigates the nanocatalytic biodiesel production from algae ( Nannochloropsis sp.). The hydrothermal synthesis route was used in this study to produce nano Ca(OCH 3 ) 2 (calcium methoxide) as a model catalyst. The effect of the main reaction parameters i.e. catalyst dosage, temperatures under constant pressure, methanol molar ratio and reaction time on the yield of FAME (fatty acid methyl ester) were examined. Kinetic study of biodiesel synthesis from crude microalgae oil using nanocatalytic transesterification reaction was appraised. The results indicate that CH 3 O − species (a cluster of tiny plate-like architectures) in Ca(OCH 3 ) 2 catalyst, and acted as main active sites for transesterification process. In additional, Ca(OCH 3 ) 2 catalyst has excellent catalytic performance in production of biodiesel. The highest FAME yield of 99.0% was obtained over 3 wt.% of Ca(OCH 3 ) 2 catalyst loading at methanol to oil molar ratio of 30:1 and reaction time of 3 h at 80 °C. Moreover, the catalyst displays a good stability and reutilization. A satisfactory FAME yield of 96% was achieved after use for five consecutive cycles without significant deactivation. The activation energy ( E a ) of the transesterification reaction of crude Nannochloropsis oculata oil with methanol over Ca(OCH 3 ) 2 nanocatalyst was obtained as 58.62 kJ mol −1 . The results revealed that the yield of methyl esters obtained from algae-based triglycerides was follows a pseudo first order mechanism for the forward reaction. These results suggest that the nanocatalyst is a promising for a green biodiesel production process from algae.

Preparation and characterization of TiO2 embedded PVC ultrafiltration membranes

Abstract: In this study, polyvinyl chloride membranes embedded with TiO 2 nanoparticles were prepared via non-solvent induced phase separation method. The results of FESEM showed that all the membranes had sponge-like and asymmetric structure and the size of sponge-like as well as surface pores increased as the content of TiO 2 increased. Backscattered FESEM results showed that nanoparticles were dispersed uniformly throughout the membranes even though agglomeration was observed for 2.0 wt. % TiO 2 embedded PVC membranes. Contact angle results revealed that hydrophilicity of membranes increased with increasing TiO 2 content. Moreover, water flux of membranes increased with increasing TiO 2 content as a result of increase in hydrophilicity. The results of abrasion test with silicon carbide slurry showed that weight loss of composite membranes were higher than that of neat PVC membrane meaning that incorporation of TiO 2 had a negative effect on the abrasion resistance of PVC/TiO 2 membranes. Fouling properties of membranes were investigated by filtration of BSA solution and the results showed that flux recovery of composite membranes improved due to the presence of hydrophilic TiO 2 even though irreversible portion of fouling increased with increasing TiO 2 content. However, rejection of BSA decreased as the content of TiO 2 increased.

Adsorptive removal of multi-azo dye from aqueous phase using a semi-IPN superabsorbent chitosan-starch hydrogel

Abstract: This article reports the efficient removal of Direct Red 80 (DR80) dye from aqueous phase using a semi-interpenetrating network (IPN) superabsorbent chitosan-starch (ChS) hydrogel. In the present investigation, the influence of initial pH, ChS dose, initial dye concentration, temperature and effect of salts on the sorption of DR80 dye was evaluated. A maximum swelling capacity of 15 g/g was determined for ChS hydrogel. The sorption equilibrium data demonstrated good agreement with Freundlich isotherm. The sorption process best fitted the pseudo-second order kinetic model. Maximum uptake capacity of the hydrogel was determined as 312.77 mg/g. The mean sorption energy (E = 11.34–14.9 kJ/mol) demonstrated that DR80 sorption was mainly chemisorption. The temperature dependence data revealed the sorption process was spontaneous, endothermic and favourable at higher temperature based on the enthalpy (ΔH° = +83.68 kJ/mol) value obtained. Boyd model confirmed intraparticle diffusion was the limiting step for DR80 uptake. In addition, sorption/desorption studies were performed to investigate the reusability of ChS hydrogel which demonstrated significant sorption for four consecutive cycles.

Economic and life cycle environmental optimization of forest-based biorefinery supply chains for bioenergy and biofuel production

Abstract: The increased use of forest and wood residues for the production of bioenergy, biofuels, and other bioproducts is essential to enhance the economic performance of forest products industries and reduce environmental impacts. Bi-objective optimization models have been developed recently to support the optimum design of either bioenergy or biofuels supply chains considering economic as well as environmental impacts. In an integrated bioenergy and biofuels supply chain where biofuel producers are also users of the generated energy, the energy flows among co-located supply chain entities affect the environmental and economic objective functions and consequently the optimal design of the supply chain, therefore, the energy flows have to be considered in the optimization model. This type of bi-objective problem has not been modeled in previous studies. In this paper, a bi-objective biorefinery supply chain optimization model for the production of bioenergy and biofuels using forest and wood residues is developed. The model considers energy flows among co-located technologies and is formulated as a multi-period mixed integer program (MIP) that calculates the net present value (NPV) and the life cycle greenhouse gas (GHG) emission savings associated with the biorefinery supply chain. The applicability of the proposed model is illustrated through a case study in British Columbia, Canada.

Quality-related fault detection approach based on dynamic kernel partial least squares

Abstract: In this paper, a new dynamic kernel partial least squares (D-KPLS) modeling approach and corresponding process monitoring method are proposed. The contributions are as follows: (1) Different from standard kernel partial least squares, which performs an oblique decomposition on measurement space. D-KPLS performs an orthogonal decomposition on measurement space, which separates measurement space into quality-related part and quality-unrelated part. (2) Compared with the standard KPLS algorithm, the new KPLS algorithm, D-KPLS, builds a dynamic relationship between measurements and quality indices. (3) By introducing the forgetting factor to the model, i.e., the samples gathered at the different history time are assigned to different weights, so the D-KPLS model builds a more robust relationship between input and output variables than standard KPLS model. On the basis of proposed D-KPLS algorithm, corresponding process monitoring and quality prediction methods are proposed. The D-KPLS monitoring method is used to monitor the numerical example and Tennessee Eastman (TE) process, and faults are detected accurately by the proposed D-KPLS model. The case studies show the effeteness of the proposed approach.

Enterprise-wide optimization for industrial demand side management: Fundamentals, advances, and perspectives

Abstract: The active management of electricity demand, also referred to as demand side management (DSM), has been recognized as an effective approach to improving power grid performance and consumer benefits. Being large electricity consumers, the power-intensive process industries play a key role in DSM. In particular, enterprise-wide optimization (EWO) for industrial DSM has emerged as a major area of interest for both researchers and practitioners. In this work, we introduce the reader to the fundamentals of power system economics, provide a definition of DSM that reflects more strongly the consumer's perspective, and present a comprehensive review of existing works on EWO for industrial DSM. The review is organized into four parts, which correspond to the four main challenges that we identify as: (1) accurate modeling of operational flexibility, (2) integration of production and energy management, (3) decision-making across multiple time and space scales, and (4) optimization under uncertainty. Finally, we highlight research gaps and future opportunities in this area.

Heat-Integrated Pressure-Swing Distillation Process for Separation of a Maximum-Boiling Azeotrope Ethylenediamine/Water

Abstract: A partially heat-integrated pressure-swing distillation process is designed for the separation of a maximum-boiling azeotrope of ethylenediamine/water. Aspen Plus and Aspen Dynamics are used to study rigorous steady state and dynamic simulations for this neat operation. An optimized configuration of this process is developed based on the proposed partial optimization and global economical optimization. From the results, it is found that the process with partial heat integration is more competitive than the non-heat-integrated one from the economic point view. The partially heat-integrated process helps save energy consumption of 19.79% and TAC of 15.30%, respectively. Basic and improved control structures are explored in this system, so that the better control solutions are discussed from the comparison. Purity fluctuations of products can be decreased by adding a ratio control block in the process. And the dynamic control is kept within acceptable limits.

IMC PID controller tuning for stable and unstable processes with time delay

Abstract: In this paper, a new internal model control (IMC) PID tuning method is proposed for stable and unstable processes with time delay. In order to implement pole zero conversion and guarantee the stability of the process, an imaginary first-order filter based on pole zero conversion is considered for the stable and unstable first order processes with time delay and a first-order lead-lag compensator is serried to PID controller for first order plus integrating and second order unstable processes with time delay. Set-point weighting is used to reduce the undesirable overshoot. The adjusting parameter can be calculated by the time constant and time delay of the processes directly, and the guidelines to calculate the coefficients have high oneness in form. Simulation works have been performed and compared with recently reported method, and the proposed tuning method gives consistently better performance and robustness for a class of processes with time delay.

From rescheduling to online scheduling

Abstract: We first review advances in rescheduling, traditionally viewed as an approach to tackle uncertainty, including methods that rely on recourse through feedback as well as methods that account for uncertainty a priori. Then, we show that traditional event-triggered rescheduling has some shortcomings which can be addressed if rescheduling is approached as an online problem. We review methods that consider aspects of this online problem and define notation and some key features of this problem. Furthermore, we propose a broad framework for the classification of online scheduling methods. Finally, we discuss a number of open research questions, including the generation of high quality of closed-loop (implemented) schedules through the selection of appropriate model, horizon length, time-step, objective function modifications, and constraint addition.

On multi-parametric programming and its applications in process systems engineering

Abstract: In multi-parametric programming, an optimization problem is solved for a range and as a function of multiple parameters In this review, we discuss the main developments of multi-parametric programming over the last two decades from a theoretical, algorithmic and application perspective In addition, we provide an opinionated view of the future research directions in multi-parametric programming

Technical and economical evaluation of bioethanol production from lignocellulosic residues in Mexico: Case of sugarcane and blue agave bagasses

Abstract: Bioethanol is the main biofuel used in Brazil and USA, produced from sugarcane and corn. Nevertheless, the use of food to produce ethanol has to be replaced by agroindustrial waste or energy crops. The alternative raw material for bioethanol production in Mexico could be sugarcane and blue agave bagasses. In this work, we built a complete simulation process using Superpro Designer ® software considering only the upstream units of fermentation for the technical and economical evaluation of lignocellulosic ethanol. Such consideration is based on a state-of-the-art analysis of the technology, indicating that technical and economical bottlenecks include pretreatment, saccharification and hexoses and pentoses fermentation. The simulation was carried out at different efficiency levels through a statistical analysis of surface responses and, three different saccharification processes to analyze ethanol production in terms of complete substitution of oxygenates in gasoline distributed in Mexico. The results indicate that ethanol production cost is 1.34 and 1.46 USD/gallon and potential production is 40.13 and 1380 MM gallon/year using blue agave bagasse and sugar cane bagasse, respectively.

Adsorption of a new nonionic surfactant on carbonate minerals in enhanced oil recovery: Experimental and modeling study

Abstract: Surfactants have ability to mobilize the residual oil trapped in porous medium and resulting higher oil recovery by altering interfacial tension between residual oil and water. However, adsorption of surfactant onto the solid surface reduces the concentration of surfactant and makes it less effective in interfacial tension reduction in enhanced oil recovery (EOR) applications. This study highlights equilibrium adsorption and kinetics of Trigoonella foenum-graceum as a newly introduced nonionic surfactant on carbonate minerals. Conductivity technique was used to measure the amount of surfactant adsorbed on crushed rock. Batch experiments were used to investigate the adsorption of surfactant on solid rock surface. The results demonstrated that increasing surfactant concentration increases the adsorption. Four adsorption isotherms (Langmuir, Freundlich, Temkin, and Linear) were introduced to resulted data and their adsorption parameters were calculated. It can be concluded that the Langmuir isotherm is the best model for describing the data. The experimental adsorption kinetic data were evaluated by three well-known models (pseudo-first-order, pseudo-second-order and intra particle diffusion models). According to correlation coefficients it was found that the pseudo-second-order model was fitted to the data very well. The results of this study can be useful in surfactant selection in EOR processes especially for chemical flooding schemes.

Integration of scheduling and control under uncertainties: Review and challenges

Abstract: In order to achieve optimal operational conditions, the integration of decision-making across different layers of a company and the consideration of uncertain parameters in view of dynamic market conditions are essential. In this article, we review some of the efforts done by the process system engineering and process control communities aiming to optimize performance in a process industry, specifically in the areas of control, scheduling and their integration under process uncertainties. First, uncertainties in process scheduling and control are analyzed, and the different mathematical approaches to describe and optimize problems under uncertainty are described. Recent advances and relevant frameworks for scheduling and control under uncertainties are presented, and efforts for the integration of scheduling and control are reviewed.

The Influence of magnetic field on heat transfer of magnetic nanofluid in a sinusoidal double pipe heat exchanger

Abstract: In this article, the effect of magnetic field on the Nanofluid flow inside a sinusoidal two-tube heat exchanger is investigated numerically. This study focuses on the influence of variable magnetic field in the heat transfer of heat exchanger while mixture is single phase. In this heat exchanger, the inner tube is sinusoidal and the outer tube is considered smooth. The magnetic field is established orthogonal to sinusoidal tube. The basis fluid is water with 4 vol.% Nano particles (Fe 3 O 4 ). In our study, Ferrofluid flows in the internal tube (sinusoidal tube) as hot fluid and air flows counter currently as cold fluid in external tube. The finite volume method with the SIMPLEC algorithm is used for handling the pressure⿿velocity coupling. The numerical results present validated data with experimentally measured data and show good agreement with measurement. The influence of the variation of different parameters like geometric shape, intensity of magnetic field non-dimensional number and Reynolds number, on heat transfer is investigated. According to obtained results, sinusoidal formation of the internal tube significantly increases the Nusselt number inside a two-tube heat exchanger. Also, magnetic field enhances diffusion of the cold boundary layer to the central parts of the inner tube for various geometric shape coefficients. Our findings show that the diffusion also elevates as the intensity of the magnetic field is increased. So, Nusselt number and heat transfer increase and this augmentation intensifies in high Reynolds number.

Control comparison of conventional and thermally coupled ternary extractive distillation processes

Abstract: Extractive distillation is widely used to separate binary mixtures with azeotropes that prevent separation in a single distillation column. The conventional binary extractive distillation configuration uses two columns with one key component going overhead in the extractive column and the other key component going either overhead or out the bottom of the solvent recovery column, depending on the effect of the solvent on the volatilities of the key components. Extractive distillation can also be applied to separate ternary mixtures with azeotropes. The conventional ternary extractive process requires three columns. Unconventional processes can also be used, such as thermally coupled sidestream/rectifier columns. Economic advantages of the thermally coupled process have been reported for some separations. The controllability of extractive distillation system for binary mixtures has been explored in many papers. The novel contribution of this paper is the exploration of the dynamic controllability of extractive distillation systems for a ternary mixture. The dynamics of a conventional three-column process are compared with a thermally coupled column/rectifier process.

Anionic and cationic dyes adsorption on porous poly-melamine-formaldehyde polymer

Abstract: Liquid phase adsorption is one of the most effective approaches for dye removal from colorant effulent. In this study, we investigated the adsorption behaviors of cationc and anionic dyes on a highly porous adsorbent of poly-melamine-formaldehyde (PMF). Both micropores and mesopores were found in PMF, which supported high specific surface area and pore volume. The maxmium adsorption capaities for methylene blue (MB), methyl violet 2B (MV), methyl orange (MO), orange II sodium salt (OS) and congo red (CR) were 80.8, 113.9, 81.2, 89.3 and 87.5 mg g −1 , respectively. Isotherm study showed that the experimental data can be well fitted by Langmuir adsorption model. Kinetic study indicated that the adsorption process followed pseudo-second order kinetic model and both external and intra-particle diffusion were rate-determining steps. Furthermore, dye-exhausted PMF can be regenerated by sulfate radical based advanced oxidation process. After 6 runs, the dye removal percentages for MV and OS were 87.6% and 99.4%, respectively, indicating good stability and reusability of PMF. The main factor contributed to the high adsorption capacity of PMF should be ascribed to its high specific surface area and large pore volume. The advantages of high adsorption capacity and stability made PMF a promising adsorbent for colorant effluent treatment.

The potential of direct contact membrane distillation for industrial textile wastewater treatment using PVDF-Cloisite 15A nanocomposite membrane

Abstract: This work demonstrates the feasibility of employing direct contact membrane distillation (DCMD) for treating industrial textile wastewater for clean water production. Experimental results showed that the in-house fabricated polyvinylidene fluoride-Cloisite 15A polymer–inorganic nanocomposite membrane is robust and able to treat the industrial effluent by reducing at least 89% of the initial values of the water quality parameters measured. However, the membrane permeate flux was reported to decline almost 50% in the first few hours of the 40-h treatment process before reaching water flux of 13–22 kg/m2 h. It is believed that the initial flux decline is mainly caused by the foulants accumulated on the membrane outer surface that increases mass transfer resistance of water molecules and reduces water productivity. With respect to separation characteristics, the DCMD process has shown better performance for COD and color removal in comparison to the other commonly used pressure-driven membrane processes. Further improvement on the membrane surface properties is necessary to reduce fouling propensity and pore wetting caused by the surfactants and other foulants in the textile wastewater. This is of particular importance for long-term operation of DCMD process.

CFD-PBM approach with modified drag model for the gas–liquid flow in a bubble column

Abstract: In this work, numerical simulations of cylindrical bubble column are performed using the Euler–Euler approach incorporated with a population balance model (PBM). First, three drag models and their corresponding modified models with the wake acceleration are incorporated into the coupled approach in order to evaluate the effectiveness of these drag models. The simulated time-averaged local gas holdups and normalized axial liquid velocities using different drag equations are compared with the experimental data, showing that only the PBM-customized drag model with the wake acceleration (cf., the application of a correction factor) can reproduce the measured flow field data. Subsequently, the applicability of the coupled approach with the effective drag model is further evaluated at various superficial gas velocities and gas distributors. The simulated results accord well with the experimental data at high gas velocities. However, the model greatly underestimates the radial local gas holdup and the total gas holdup at low gas flow rates. Additionally, the simulated results demonstrate that the opening area and orifice geometry play a significant role in total aeration and the triple-ring gas distributor produces more uniform radial profiles of local gas holdup and normalized liquid velocity than the multi-orifice one, thus leading to poor mixing efficiency in the bubble column.

Gasification behaviors and kinetic study on biomass chars in CO2 condition

Abstract: Non-isothermal thermogravimetry method was used in the paper to investigate the gasification properties of four biomass chars. The chemical composition and microstructures of biomass chars were analyzed by chemical analysis, scanning electron microscope (SEM) and BET method. The results show that the initial gasification temperature ( T 0.1 ) and total gasification temperature ( T 0.9 ) of peanut shell char (PS-char), corncob char (CC-char) and bamboo char (BB-char) are close, and rice shell char (RS-char) has relatively higher T 0.1 and T 0.9 . Gasification reactivity of biomass char is in the order of BB-char > CC-char > PS-char > RS-char. It has been confirmed by chemical analysis and microscopic structure analysis that there is a good correlation between the biomass char gasification reactivity and the alkali index; that is, the greater the alkali catalytic index, the higher the catalytic effect. The random pore model (RPM), volume model (VM) and unreacted shrinking core model (URCM) were used to fit the experimental data. The results show that the experimental data agree better with the RPM than with other two models. The apparent activation energies of non-isothermal gasification of PS-char, CC-char, BB-char and RS-char calculated by RPM are 238.6 kJ/mol, 302.7 kJ/mol, 284.9 kJ/mol and 242.2 kJ/mol.

Supercritical water gasification of glycerol and methanol mixtures as model waste residues from biodiesel refinery

Abstract: The eco-friendly processing in biodiesel refineries is feasible with effective utilization of the byproducts and waste residues. The motive of this research is to convert the model byproducts of biodiesel refineries to H 2 . In this study, different glycerol⿿methanol mixtures were gasified in supercritical water at variable temperatures (450⿿600 °C) and pressures (23⿿25 MPa) for 45 s in a continuous-flow tubular reactor. Glycerol and methanol concentrations were varied from 5 to 20 wt% individually in the mixtures, and their impacts on gas yields were investigated both experimentally and thermodynamically. The thermodynamic simulations were performed using Aspen Plus based on Gibbs free energy minimization method. The thermodynamic yield (25.3 mmol/g) of H 2 was higher compared to experimental yields (19 mmol/g) at 600 °C, 25 MPa and 1:1 glycerol-to-methanol feed solution. To enhance the gas yields, the effects of four alkali catalysts such as KOH, NaOH, K 2 CO 3 and Na 2 CO 3 at 0.5 wt% concentration were examined. Among all the catalyst, 0.5 wt% K 2 CO 3 resulted in highest H 2 yields (24.8 mmol/g), total gas yields (1.24 g/L) and carbon gasification efficiency (96.7%) at 600 °C and 25 MPa with 1:1 glycerol-to-methanol feed solution. The results suggest that effluents from biodiesel refineries can be used as potential feedstock for waste-to-energy conversion.

Preparation of ternary combined ZnO-Ag2O/porous g-C3N4 composite photocatalyst and enhanced visible-light photocatalytic activity for degradation of ciprofloxacin

Abstract: In current work, a ternary combined ZnO-Ag 2 O/porous g-C 3 N 4 (ZnO-Ag 2 O/pg-C 3 N 4 ) composite photocatalyst was prepared and used for the degradation of ciprofloxacin (CIP) under visible light irradiation The structure, surface morphology and chemical composition of as-prepared composite photocatalyst are investigated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflectance spectroscopy (DRS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), photoluminescence (PL) and Brunauer–Emmett–Teller (BET) methods From the DRS and PL optical property test, the result indicated that ZnO-Ag 2 O/pg-C 3 N 4 presented relative narrow band gap and higher separation rate of photoinduced charge carriers in the ternary combined system, which was favorable for the photocatalytic activity enhancement under visible light irradiation Compared with ZnO, porous g-C 3 N 4 , Ag 2 O and ZnO-Ag 2 O, the prepared ZnO-Ag 2 O/pg-C 3 N 4 presents the highest degradation efficiency (974%) within 48 min The degradation intermediates of CIP were detected by HPLC/MS during photocatalytic degradation Furthermore, porous g-C 3 N 4 as a visible-light-driven photocatalyst used as supporter in the combined system not only improves the degradation efficiency, but also speeds up the reaction rate