新型壳聚糖/锆复合球的制备及硼吸附性能

通过氧氯化锆与壳聚糖的配位反应以及Zr （OH）4在壳聚糖内的原位沉淀,制备了一种新型壳聚糖-锆复合球（CTS-Zr）并用于硼的吸附分离。采用扫描电子显微镜（SEM）和傅里叶红外光谱（FTIR）对CTS-Zr进行了表征,系统考察了溶液pH、硼初始浓度、接触时间、温度及共存阴离子Cl^-、NO₃^-和SO₄^2-对CTS-Zr吸附性能的影响。结果表明：pH=2～7时,CTS-Zr对硼的吸附效率较高;吸附平衡行为符合Langmuir等温吸附模型;pH=7时,最大吸附量计算值为21.1 mg·g^-1;吸附动力学符合准二级动力学模型;常见的共存阴离子对硼的吸附影响很小;吸附热力学研究表明,CTS-Zr对硼的吸附过程为放热的非自发过程;使用pH=12的NaOH水溶液,对吸附剂CTS-Zr进行了洗脱,洗脱效率为96.3%,且经过3次吸附-解吸循环后,CTS-Zr的吸附效率没有明显降低。     

Fixed bed column adsorption of ACID Yellow 17 dye onto Tamarind Seed Powder

The intention of this study was to explore the efficacy and feasibility for Acid Yellow 17 adsorption onto fixed bed column of Tamarind Seed Powder. The effect of various parameters like flow rate, initial concentration of dye, bed height, and pH were exploited in this study. The Thomas, Yoon–Nelson, Bed Depth Service Time (BDST), and Adams and Bohart model were analysed to evaluate the column adsorption performance. The adsorption capacity, rate constant and correlation coefficient associated to each model for column adsorption was calculated and mentioned. The adsorption capacity increases with increasing initial dye concentration and bed height and decreasing flow rate. The maximum adsorption capacity related to Adams and Bohart model was found to be 978.5 mg/g at initial concentration of 50 ppm at constant flow rate of 15 mL/min, bed height of 15 cm, and pH 7. Le but de cette étude était d'explorer l'efficacité et la faisabilité de l'Acid Yellow 17 adsorption sur colonne à lit fixe de Tamarind Seed Powder. L'effet de différents paramètres comme le débit, la concentration initiale de colorant, la hauteur du lit et le pH ont été exploitées dans cette étude. Le Thomas, Yoon‐Nelson, BDST et Adams et le modèle Bohart ont été analysées pour évaluer les performances d'adsorption colonne. La capacité d'adsorption, constante de vitesse et coefficient de corrélation associé à chaque modèle de la colonne d'adsorption a été calculé et mentionné. Les augmentations de capacité d'adsorption avec une concentration croissante de colorant initial et un lit en hauteur et le débit diminue. La capacité maximale d'adsorption liées au modèle Adams et Bohart a été trouvé à 978,5 mg/g à la concentration initiale de 50 ppm à débit constant de 15 ml/min, la hauteur du lit de 15 cm et un pH de 7.     

Removal characteristics of some priority organic pollutants from water in a fixed bed fly ash column

The efficiency of a coal fly ash (generated from a thermal power plant) adsorption column for the removal of some priority organic pollutants, viz phenol, o‐hydroxyphenol, m‐hydroxyphenol and 4‐nitrophenol from aqueous solution has been studied. The column performance was evaluated from the concept of the formation of a primary adsorption zone and the breakthrough curve. The extent of solute removal obtained from breakthrough curve during column operation was compared with that obtained from the isotherm parameters for batch operation. The loaded solutes in the column were successfully eluted with acetone, achieving 98% recovery. In order to determine the practical applicability of the column operation the process was repeated a number of times and the variation of column capacity with number of operation cycles was evaluated. Even after six successive cycles, the column was found to retain almost 80% capacity. Copyright © 2005 Society of Chemical Industry     

Kinetics and equilibrium studies of removal of an azo dye from aqueous solution by adsorption onto scallop

In the present work removal of an azo dye (Reactive Black 5) was investigated from aqueous solution by adsorption onto scallop as a low-cost and widely available adsorbent. The effect of various operational parameters, such as contact time, pH, initial dye concentration and adsorbent dosage on the removal efficiency of dye was studied. Removal efficiency declined with the increase in solution pH and initial dye concentration but with the decrease in adsorbent dosage. Experimental equilibrium and kinetics data were fitted by Langmuir and Freundlich isotherms and pseudo-first-order and pseudo-second-order kinetic models, respectively.     

Modeling of cobalt and lead adsorption by Ficus benghalenesis L. in a fixed bed column

Heavy metals presence in waste water is detrimental to human and animal health. Treatment of such contaminated waters emanating from various process industries is needed to make the reuse of water possible. Adsorption is a useful technique available for treatment of such waste waters. Several studies with different adsorbents have been reported in the literature but their relevance is limited to small quantities of waste waters as those studies were conducted in batch mode. Continuous contacting is the only viable option to augment the treatment capacity and this calls for further study to understand the impact of relevant parameters on continuous adsorption. In the present article, treatment of cobalt and lead laden waste water with Ficus benghalenesis leaf powder as the adsorbent is studied in a laboratory scale fixed bed column. Effect of operating parameters such as inlet flow rate (1–2?mL/min), bed height (2–4?cm), and feed metal ion concentration (20–100?mg/L) on the breakthrough curve is reported. The highest uptake capacities realized are 11.09?mg/g for cobalt and 12.27?mg/g for lead, when a 20-mg/L metal solution is admitted at 1.0?mL/min in to a 2-cm long bed of the adsorbent. Experimental data collected are tested to three empirical models: Thomas, Adams–Bohart, and Yoon–Nelson models and parametric values of the three models evaluated. Experimental results confirmed the suitability of the sorbent for Co(II) and Pb(II) ion adsorption with adsorptive nature being favorable, efficient, and environment friendly.     

A comparison of triglyceride oil hydrogenation in a downflow bubble column using slurry and fixed bed catalysts

The hydrogenation of the triglyceride oil, soya bean oil, has been studied in the temperature range 130–160 °C and in the pressure range 100–600 kPa using (i) a 5% w/w Pd/C slurry catalyst and (ii) a 3% w/w Pd/Al₂O₃ Raschig ring catalyst in a cocurrent downflow contactor (CDC) reactor. Separate studies of residence time distribution (RTD) were carried out in a modified CDC device in order to determine dispersion numbers and dispersion coefficients. The RTD measurements indicated that the overall flow was a mixture of well‐mixed and plug flow for the unpacked CDC, so that the entry section (0–30 cm from entrance) was perfectly mixed and the remainder of the column (30–130 cm) gave predominantly plug flow behaviour. The introduction of random packing in the form of 13 mm Raschig rings gave rise to increased back mixing in the lower part of the CDC and the overall dispersion number increased due to liquid and gas circulation around the packing elements. Kinetic studies revealed an initial rate reaction order of 1.24–1.26 with respect to hydrogen concentration both in slurry and fixed bed CDC reactors and is interpreted as a combination of a parallel pair of first and second order reactions during the initial stages of reaction. Mass transfer coefficients for gas absorption (k_La) and liquid–solid mass transport (k_s) were determined for both types of reactor. The k_La values lay in the range 1.0–3.33 s⁻¹ and the liquid–solid transport resistances (X_LS) were all <1%, so that the reaction was almost totally surface reaction rate controlled. Apparent energy of activation measurements gave values of E_A = 49 ± 6 kJ mol⁻¹, which is strongly indicative of surface reaction rate control involving the hydrogenation of an olefinic double bond. The selectivity in respect of linolenate (three double bonds) removal and linoleate (two double bonds) retention was high with, for palladium, relatively low trans‐isomer production (<30%). The overall selectivity was slightly, but significantly, better for the fixed bed CDC reactor and this is attributed to the greater degree of plug flow behaviour in the latter, despite the bed causing an increase in dispersion number. However, there is no reaction in the well‐mixed section of the fixed bed CDC reactor as there is in the slurry CDC reactor and this is likely to improve selectivity in a consecutive reaction sequence. © 2000 Society of Chemical Industry     

Fluidization of micronic particles in a conical fluidized bed: Experimental and numerical study of static bed height effect

The numerical simulations and experimental data of bed hydrodynamics in a conical fluidized bed unit are compared. Experimental studies have been carried out in a bed containing TiO₂ particles belonging to A/C boundary of Geldart's classification with a wide particle‐size distribution. Thus, pressure measurements and an optical fiber technique allowed determining the effect of static bed height on the fluidization characteristics of micronic particles. Numerical simulations have then been performed to evaluate the sensitivity of gas‐solids drag models. The Eulerian multiphase model has been used with different drag models and three boundary conditions (BC) consisting of no‐slip, partial‐slip, and free‐slip. The numerical predictions using the Gidaspow drag model and partial‐slip BC agreed reasonably well with the experimental bed pressure drop measurements. The simulation results obtained for bed expansion ratio show that the Gidaspow model with the free‐slip BC best fit with the experimental data. © 2011 American Institute of Chemical Engineers AIChE J, 2012     

Batch and fixed‐bed column adsorption of Cu(II), Pb(II) and Cd(II) from aqueous solution onto functionalised SBA‐15 mesoporous silica

Functionalised SBA‐15 mesoporous silica with polyamidoamine groups (PAMAM‐SBA‐15) was successfully prepared with the structure characterised by X‐ray diffraction, nitrogen adsorption–desorption, Fourier transform infrared spectra and thermogravimetric analysis. PAMAM‐SBA‐15 was applied as adsorbent for Cu(II), Pb(II) and Cd(II) ions removal from aqueous solution. The effects of the solution pH, adsorbent dosage and metal ion concentration were studied under the batch mode. The Langmuir model was fitted favourably to the experimental data. The maximum sorptive capacities were determined to be 1.74 mmol g^?1 for Cu(II), 1.16 mmol g^?1 for Pb(II) and 0.97 mmol g^?1 for Cd(II). The overall sorption process was fast and its kinetics was fitted well to a pseudo‐first‐order kinetic model. The mean free energy of sorption, calculated from the Dubinin–Radushkevich isotherm, indicated that the sorption of lead and copper, with E > 16 kJ mol^?1, followed the sorption mechanism by particle diffusion. The adsorbent could be regenerated three times without significant varying its sorption capacity. A series of column tests were performed to determine the breakthrough curves with varying bed heights and flow rates. The breakthrough data gave a good fit to the Thomas model. Maximum sorption capacity of 1.6, 1.3 and 1.0 mmol g^?1 were found for Cu(II), Pb(II) and Cd(II), respectively, at flow rate of 0.4 mL min^?1 and bed height of 8 cm, which corresponds to 83%, 75% and 73% of metallic ion removal, respectively, which very close to the value determined in the batch process. Bed depth service time model could describe the breakthrough data from the column experiments properly. © 2012 Canadian Society for Chemical Engineering     

Experimental study of a cocurrent upflow packed bed bubble column reactor: pressure drop, holdup and interfacial area

Gas–liquid interfacial areas have been determined by means of chemically enhanced absorption of CO₂ into DEA in a packed bed bubble column reactor with an inner diameter of 156 mm. The influence of the gas velocity and particle diameter on the interfacial areas, pressure drops and liquid holdups has been investigated. For both packings the limiting values of the gas velocities have been determined above which the interfacial areas and liquid holdups stabilize. In particular gas channelling has been found, which is less pronounced in the bed of larger particles.     

Experimental investigation and modelling study of long stick wood gasification in a top lit updraft fixed bed gasifier

We present results of an experimental study on long stick wood gasification, in an attempt to reduce wood gathering for gasification. This paper presents the results from experiments and the analyses of gasification using sticks with length 68 cm and diameter 6 cm. The moisture content of the wood was 25%. This top lit updraft gasifier operates with 180 W of blower power air supply to produce 9–10 kW of thermal energy, an energy yield of 50/1. Results were obtained for various flow conditions with airflow rates ranging from 25 to 45 m³/h. For modelling, the flaming pyrolysis time for long stick wood in the gasifier is calculated to be 2.1 min. The length of the flaming pyrolysis zone and char gasification zone is found to be 37 cm and 36 cm respectively. The turn down ratio for the gasification is around 2. The rate of feed was between 9 and 10 kg/h and the gasifier operated continuously for 5 h in two runs to study the gasifier reliability. The performance studies in specific gasification rate, equivalence ratio, turn down ratio, superficial velocity, airflow, and gas flow are analyzed. The temperature ranged from 1185 K in the combustion zone to 400 K in the drying zone. The gas and airflows can be converted to the Air/Fuel equivalence ratio, the most important aspect of gasifier operation. The equivalence ratio shows operation in a combustion mode (6.3) at start up; in a flaming pyrolysis mode (1.2) for the middle part of the run; and in the charcoal gasification mode (5.7) at the end of the run. Measurement of the equivalence ratio is a simple way of analyzing the behaviour of the gasifier. From the results of present investigation, it is revealed that the top lit updraft gasifier is more suitable for long stick wood as feed when compared to conventional updraft gasifier.     

Extension of the pore diffusion approach for modelling binary adsorption of lead and arsenic ions in a fixed‐bed column packed with atlantic cod fish scales

The removal of lead and arsenic ions using Atlantic Cod (Gadus morhua) fish scale involves ion exchange, chemisorption, and precipitation of its constituents and is competitive with respect to adsorption onto the negatively charged heterogeneous substrates. The nonlinear sorption equilibrium concept is preceded by pore diffusion of the solute and is utilised for numerical modelling of this binary adsorption. Numerical simulation data demonstrate reasonable agreements with experimental results of dynamic column tests. Sensitivity analyses confirm that parameters such as porosity, adsorption coefficient, mobility of ions, and number of sorption sites contribute significantly to breakthrough interval of contaminant in dynamic columns. At lower pH values (7–8.04), the adsorption coefficients of cations such as lead are significantly lower than at pH value of 11.0.     

管式固定床反应器柱状颗粒床层流体流动模拟与实验研究

针对管式固定床反应器内管束数量多、规模大等特点,选取单个管束作为特征结构。对装填不同直径柱状颗粒的管束,采用程序坐标定位的方法,建立柱状颗粒床层的物理模型。采用DEM与CFD联合数值仿真方法,探究反应管内径与柱状颗粒的等比表面积球当量直径之比(管径比Di/dp)对柱状颗粒床层流体流动的影响,并建立单管固定床反应器试验台,采用差压测试方法进行实验研究。结果表明,当Di/dp由5.37增至12.75时,床层空隙率和流体分布均匀性均得到改善,壁面效应的影响由床层中心减弱到管壁。基于数值模拟及实验结果对Di/dp=12.75的柱状颗粒床层进行床层压降Ergun公式常系数修正,CFD模拟计算的结果与拟合公式吻合较好。研究结果能为固定床反应器压降预测提供参考。     

Experimental study and CFD numerical simulation of an innovative vapor splitter in dividing wall column

The vapor split ratio (R_V) adjustment plays an important role on energy efficiency during dividing wall column (DWC) operation. In order to achieve active control of R_V, this aticle presents an innovative vapor splitter driven by hydraulics. The vapor flows into main tower from prefractionation section through the rectangle hole located at the end of the partition. Vapor splitting is implemented by the change of flow resistance at the rectangular hole caused by adjusting the liquid level on the bottom plate. This design makes full use of the hydraulic properties in DWC, employing simpler construction with single tunable parameter. Numerical simulations and laboratory tests were both carried out to validate its performance in the DWC with a diameter of 600 mm. The results demonstrate that the desired R_V can be handled effectively in the approximate range from 0.5 to 2, basically satisfying the industrial demand for the gas distribution.     

Hydrodynamics in an expanded bed of large size ion‐exchange resin,and natural product adsorption

Successful applications of expanded bed adsorption (EBA) technology have been widely reported in the literature for protein purification. Little has been reported on the recovery of natural products and active components of Chinese herbal preparations using EBA technology. In this study, the hydrodynamic behavior in an expanded bed of cation resin, 001 × 7 Styrene‐DVB, was investigated. Ephedrine hydrochloride (EH) was used as a model natural product to test the dynamic binding capacity (DBC) in the expanded bed. EBA of EH directly from a feedstock containing powdered herbs has also been investigated. These particles are different from commercially available expanded bed adsorbents by virtue of their large size (205 to 1030 µm). When the adsorbent bed is expanded to approximately 1.3 to 1.5 times its settled bed height, the axial liquid‐phase dispersion coefficient was found to be of the order 10^?5 m² s^?1, which falls into the range 1.0 × 10^?6 to 1.0 × 10^?5 m² s^?1 observed previously in protein purification. Because of the favorable column efficiency (low axial dispersion coefficient), the recovery yield and purification factor values of EH directly from a feedstock reached 86.5% and 18, respectively. The results suggest that EBA technology holds promise for the recovery of natural products and active components of Chinese herbal preparations. Copyright © 2007 Society of Chemical Industry     

The selective hydrogenation of butyne-1,4-diol by supported palladiums: a comparative study on slurry, fixed bed, and monolith downflow bubble column reactors

The present study was carried out to asses performance of a Pd-monolith downflow bubble column (DBC) reactor, and compare it with that of the slurry and the fixed bed DBC. The selective hydrogenation of butyne-1,4-diol to cis-2-butene-1,4-diol over palladium catalyst was chosen as a model reaction. In principle, the monolith DBC allowed the reaction to take place under kinetic control regime. Comparison with DBC employing 5% Pd/C powder and 1% Pd-on-Raschig ring catalysts revealed a better performance of the monolith DBC (1% Pd loading) with advantage of smaller reaction volume and intensified reaction rate. In the monolith DBC, improved hydrogen transport was possible, as the interface between bubbles and the channel wall was very thin, thus, the length of the diffusion path was very short. In addition, the interfacial surface area at both gas–liquid and liquid–solid interface in the monolith was also very high. The reaction kinetics was well represented by the Langmuir–Hinshelwood mechanism. As an alternative to conventional three-phase reactors, the monolith DBC was simple due to its inherent characteristic operation and no specially designed device.     

Experimental study on the simultaneous adsorption of carbon dioxide and moisture from nitrogen in linde 5 a molecular sieves

Experimental data for the simultaneous adsorption of CO₂ and moisture with variations of some process variables, such as inlet adsorbate concentration, particle Reynolds number, and bed diameter to bed length ratio, have been generated to see their effects on the efficiency of adsorption of CO₂ and moisture. Presence of moisture strongly affects the CO₂ adsorption behaviour leading to roll up of CO₂ concentration breakthrough curves, whereas the presence of CO₂ has an insignificant effect on the moisture adsorption behaviour.     

Experimental and CFD analysis of two-phase cross/countercurrent flow in the packed column with a novel internal

The pressure drop and liquid hold-up for the G-L cross/counter-current flow in a packed column with a novel internal was simulated using a Eulerian/Eulerian two-fluid model solved by a commercial CFD software CFX4.4. Simulation results are in good agreement with the experimental data of pressure drop. The internal significantly increases the gas radial velocity and lower the gas axial velocity, which lowers the pressure drop and improves operational flexibility. To minimize bypass flow caused by the internal, optimum baffle thickness and width of the internal's passage are proposed.     

Experimental and numerical study of fluid dynamic parameters in a jetting fluidized bed of a binary mixture

The solid circulation pattern, the voidage profile, and the jet penetration height have been investigated experimentally and computationally in a cold-flow model of jetting fluidized beds (JFBs) of a binary mixture in this paper. This rectangular two-dimensional bed is 0.30 m wide and 2.05 m high with a central jet and a conical distributor, which roughly stands for the ash-agglomerating fluidized-bed coal gasifier. A video camera and coloured particle tracer method were employed to explore the fluid dynamics in the bed. In terms of the average physical properties of binary mixtures, a hydrodynamic model describing the gas-solid flow characteristics in a jetting bed is resolved by using a modified Semi-Implicit Method for Pressure-Linked Equation (SIMPLE) algorithm. This paper focuses on three features of the fluid dynamics—solid circulation pattern, voidage profile, and jet penetration height. The solid circulation pattern is composed of three regions: the jetting region, the bubble street, and the annular region. Above the central nozzle the time-averaged isoporosity contours are almost elliptic, while near the walls of the bed, the voidage in high solid concentration region is approximately equal to that at the minimum fluidization state. The jet penetration height increases with increasing jet gas velocity and with decreasing average particle diameter. The increase in weight percentage of the lighter component in the binary system reveals that reduction of average density causes the enlargement of jet penetration height. The simulated results show good agreement with the experimental data.