Column Design Parameters Research Articles

Optimizing experimental binary adsorption of aniline–nitrobenzene onto granular activated carbon packed bed by Taguchi’s methodology

Herein a new statistical approach based on Taguchi’s methodology was developed for optimizing continuous simultaneous adsorption of aniline (AN) and nitrobenzene (NB) from their binary aqueous solution in a column packed with granular activated carbon (GAC). Effects of column design parameters such as feed flow rate (Q), bed height (Z) and bed diameter (D) were studied for the breakthrough curve performance using Taguchi’s L9 orthogonal array design. The parameters were optimized at three levels with the higher-is-better type response characteristics. Further, the Thomas model was used to predict column breakthrough curve and breakthrough time. Higher sorption affinity of NB over AN towards GAC surface implied favorable attachment of NB molecules. Quicker breakthrough attainment was observed at higher Q, lower Z and lower D owing to faster saturation of sorption sites. Maximum individual equilibrium adsorption uptake for AN and NB was found to be 0.29 mg/g and 3.91 mg/g, respectively, at Q = 0.02 L/min, Z = 60 cm and D = 2.54 cm. The average total equilibrium adsorption uptake (qtot) from the experimental runs was found to be 4.2 mg/g which is closer to the predicted qtot value of 4.17 mg/g.

Fixed - bed Column Adsorption Studies Using Synthetic Hydroxyapatite for Pb(II) Removal from Aqueous Solutions

In the present paper, the adsorptive Pb(II) removal from synthetic aqueous solutions using a 2 cm diameter hydroxyapatite column has been studied through column adsorption experiments by varying column depths (1, 2, 3, 4 cm) and flow rate (10, 15, 22.5 mL/min). Different types of synthetic hydroxiapatites have been involved in experiments. Column design parameters such as critical bed depth and adsorption capacity have been determined from experimental studies. The results revealed the effectiveness of synthetic hydroxyapatite porous beads in Pb(II) removal from aqueous synthetic solutions.

Axial compression performance of composite short columns composed of RAC-filled square steel tube and profile steel

An axial compression test was conducted for 11 composite short columns composed of recycled aggregate concrete (RAC)-filled square steel tube and profile steel, to explore their axial compression behaviour. The following main design parameters of columns were considered: recycled coarse aggregate (RCA) replacement percentage, width-thickness ratio of square steel tube, profile steel ratio and RAC strength. The failure process and modes, load-displacement and load-strain curves and axial stiffness of specimens were obtained and analysed in detail. Results showed the similar failure process and modes of each specimen. Specifically, the profile steel yielded before the square steel tube, and the internal RAC was crushed subsequently. Bulging deformation was evident on square steel tube, thus indicating that the column lost its bearing capacity. With the increase in RCA replacement percentage and width-thickness ratio of the square steel tube, the axial bearing capacity of specimens decreased remarkably. However, the axial bearing capacity of columns increased with the increase in profile steel ratio and RAC strength. These design parameters remarkably influenced the initial stiffness of the short columns, but exerted minimal effect on stiffness degradation at the latter stage of loading. Overall, the composite short columns exhibited high bearing capacity and good deformability in the tests. On this basis, a calculation formula for the axial bearing capacity of the columns was established through theoretical analysis and by considering the adverse effects of RCA replacement percentage. The calculated results showed good agreement with the experimental findings, thus verifying the validity of the established formula. The research conclusions can provide references for engineering applications on this type of columns.

Numerical investigation of stone columns as a method for improving the performance of rocking foundation systems

Allowing a shallow foundation to rock during an earthquake offers many benefits and importantly has demonstrated potential for improving a system’s overall performance and increased likelihood of rapid post-event recovery. However, when the soil is soft, excessive foundation rotations could induce significant residual or differential settlement, both of which could have a negative impact on the post-event functionality of the structure. This paper aims to study the rocking response of a shallow foundation that is founded in a soft clayey environment and reinforced by stone columns via numerical simulations. The implementation of stone columns is intended to reduce the likelihood of post-earthquake residual deformations. The investigation includes a sensitivity study considering the impact of various stone column material properties and design variables on the performance. Numerical analyses results show that inclusion of stone columns increases the moment capacity, improves the re-centering capability, and reduces residual settlement for a rocking foundation particularly when footings supporting large axial loads are of concern. Parametric study results indicate that the shear modulus and friction angle of the stone column material have a slight influence on the footing’s moment capacity; however, they could substantially affect the residual settlement. Key stone column design parameters, namely; length (both edge columns and central columns) and area replacement ratio, also have a pronounced impact for the seismic response of the reinforced foundation. These results also suggest that shortening the installation length and/or placing a reduced length stone column in the footing central region can optimize the footings performance.

Th(IV)/U(VI) Sorption on Modified SBA–15 Mesoporous Materials in Fixed–Bed Column

The sorption of thorium and uranium ions by functionalized SBA–15 mesoporous silica materials with Schiff base ligating groups N–propylsalicylaldimine (SBA/SA) and ethylenediaminepropylesalicylaldimine (SBA/EnSA) from aqueous solution was investigated in fixed-bed column method. The TEMPeffect of pH, sample solution volume, and the column design parameters such as sample and eluent flow rates, and column bed height were studied. These investigations allowed to obtain the experimental breakthrough curves. Regardless to the adsorbent used, application of the columns with 2.5 cm bed height and sample flow rate 0.4 mL/min, resulted in the quantitative removal of 0.5 mg of Th(IV) and U(VI) ions from 200 and 250 mL aqueous solutions, adjusted at pH 4. The quantitative desorption of the loaded ions provided a preconcentration factor of 40 and 50 for Th(IV) and U(VI), respectively. Breakthrough studies showed the higher capacity of the column packed with SBA/EnSA in comparison to that packed with SBA/SA. The breakthrough curves indicated that both of the sorbents presents higher capacity towards uranium than thorium ions. The columns could be used for at least 3 sorption-desorption cycles. The investigated columns were examined for the recovery of Th(IV) and U(VI) from tap water and seawater samples.

Novel gas holdup and regime transition correlation for two-phase bubble columns

The gas holdup is dimensionless parameter of fundamental and practical importance in the operation, design and scale-up of bubble columns. Unfortunately, the many relationships between the bubble column fluid dynamic parameters and the various variables characterizing the system make it difficult to find general correlations for the precise estimation of the gas holdup. Wilkinson et al. (1992), in their pioneering paper, proposed a correlation to predict the gas holdup in industrial-scale bubble columns, based on the physical properties of the phases and the operating conditions. However, this correlation lacks in generality, as it does not take in account the bubble column design. In this paper, we propose a generalization of the Wilkinson et al. (1992) gas holdup correlation to take into also the bubble column design parameters. Starting from considerations concerning the flow regime transition, corrective parameters are included to account for the effects introduced by the gas sparger openings, the bubble column aspect ratio and the bubble column diameter. The proposed correlation has been found to predict fairly well previously published gas holdup and flow regime transition data.

Breakthrough curve modeling of graphene oxide aerogel packed fixed bed column for the removal of Cr(VI) from water

The extensive investigation was conducted on the performance of the laboratory-scale fixed-bed column containing graphene/polylysine aerogel as an adsorbent for the removal of Cr(VI). The effect of important column design parameters on the performance of the column bed was investigated. High bed height, low influent flow rate, and high influent Cr(VI) concentration were found to be the better condition for the adsorption of Cr(VI). The effect of column bed height on the breakthrough was analyzed using bed depth service time (BDST) model and predicted the critical bed height 0.37 and 1.0cm at flow rates 1.66 and 3.32mL/min respectively for the Cr(VI). The Thomas and Yoon-Nelson model were found suitable for describing the breakthrough behavior of the column. The regeneration of exhausted column bed was studied for three cycles of adsorption-desorption. The calculation of life factor suggested that the column bed can avoid the breakthrough time at t=0 for 7.5 cycles whereas, the uptake capacity would be zero after 9.12 cycles of adsorption-desorption.

Performance of packed bed column using Chara aculeolata biomass for removal of Pb and Cd ions from wastewater

ABSTRACTBiosorption of Pb and Cd from aqueous solution by biomass of Chara aculeolata was studied in a continuous packed bed column. C. aculeolata in the fixed bed column is capable of decreasing Pb and Cd concentrations from 10 mg/L to a value below the detection limit of 0.02 mg/L. Selective uptake of Pb and Cd in a binary solution resulted in Pb having much higher relative affinity than Cd. The experiments were conducted to study the effects of column design parameters, bed depth, and flow rate on the metal biosorption. Pb uptake capacity of C. aculeolata increased with increased bed depth and decreased flow rate, while Cd uptake capacity increased with increased bed depth but remained constant at any flow rate. The Thomas model was found in a suitable fitness with the experiment data for Pb and Cd (R2 > 0.90). The efficiency of biosorbent regeneration achieved by 0.1 M HCl was very high, that was, 98% for Pb and 100% for Cd in the third reused cycle. It can be concluded that C. aculeolata is a good biosorbent for treating wastewater having low concentrations of Pb and Cd contamination.

Mathematical Modeling of the Anthocyanins Adsorption/Desorption from Blueberries on Amberlite FPX-66 Resin in A Fixed Bed Column

The objective of the present study was to predict column design parameters using mathematical models such as bed depth service time (BDST) and the empty bed residence time (EBRT). The dynamic adsorption/desorption of anthocyanins from blueberry water extracts was conducted on Amberlite FPX-66 resin in a fixed bed column system. Blueberry anthocyanins were extracted with acidified hot water (90 °C) utilizing high power ultrasound. Breakthrough curves were obtained at different bed depths (5, 7.5, 10, 12.5 and 15 cm) and constant flow rate of 4.0 mL/min. Increase in bed height increased both the breakpoint and exhaustion point of the FPX-66 resin. The experimental data fitted well to BDST model at 5% of the breakthrough curve (R2 = 0.9864). The EBRT was in the range of 3.75–10.25 min at different bed depths. In addition, desorption of anthocyanins was studied at different ethanol concentrations and sigmoid equation was applied to obtain maximum recovery rates. Practical Applications Anthocyanins are antioxidant flavonoids in blueberries. They are responsible for the blue color of the berries and are known to promote better health by preventing chronic diseases. A concentrated anthocyanin extract from blueberries has the potential to be used as dietary supplement, natural colorant and functional food ingredient. This present study optimized resin adsorption method to concentrate polyphenols and remove sugars using mathematical models. Optimization of the column design parameters can be used in designing a pilot/industrial scale column for the separation and concentration of anthocyanins from blueberries.

Start-up dynamic behaviors of a HI–I2–H2O distillation column for the sulfur-iodine hydrogen production cycle

The sulfur-iodine (SI) cycle to produce hydrogen from water requires a HIx multistage distillation column to obtain hyperazeotropic hydriodic acid vapor as a top product that can be afterward decomposed into hydrogen and iodine. To design a HIx multistage distillation column that can be applied to the cycle, its static and dynamic simulation is essentially demanded. A 50NL-H2/h scale SI test facility to be operated under a pressurized environment has been constructed in Korea. This study focuses on the HIx multistage distillation column (HIxMDC-50L) for the 50NL-H2/h SI test facility. The HIxMDC-50L was designed and installed in 2013. Based on the design specifications and operation method, the start-up behavior of the HIxMDC-50L has been analyzed using the simulation code “KAERI-DySCo”. As a result of the start-up dynamic simulation, it is confirmed that the HIxMDC-50L will advance to the steady state value within 1050 s to fulfill a hydrogen production rate of 50NL-H2/h. On the other hand, not only the effects of the column design parameters on the progress to a steady state but also the effects of several operation variables on the top product have been evaluated for safely operating the HIxMDC-50L.

Novel Procedure for Assessment of Feasible Design Parameters of Dividing-Wall Columns: Application to Non-azeotropic Mixtures

Dividing wall columns (DWCs), as a subset of fully thermally coupled distillation systems (FTCDS), is considered as one of most appealing distillation technologies to the chemical industry, because it can bring about substantial reduction in the capital investment, as well as savings in the operating costs. This study targets on how to improve the energy efficiency of DWCs by achieving their well-designed feasible parameters. Two methods are applied to study the effect of liquid and vapor split ratios including a shortcut method and a method of systematic calculations by using differential equation profiles. In the latter approach, differential composition profiles in each column section are obtained by considering feasible key design parameters. The finding of pinch points for each section profiles allowed determining the limiting values of the operating parameters. The intersections of these profiles are used to get well-designed feasible parameters of the liquid and vapor split ratios in an attempt to obtain the desired purities of the top, bottom, and side-stream products. The obtained parameters are validated by rigorous simulations. Three types of case studies involve the separation of hydrocarbons (n-pentane, n-hexane, n-heptane), aromatics (benzene, toluene, p-xylene), and alcohols (ethanol, propanol, butanol).

Dynamic column adsorption of As on iron-oxide-coated natural rock (IOCNR) and sludge management

An extended column adsorption study on arsenic (As(III)/As(V)) was conducted using the developed adsorbent iron-oxide-coated natural rock. We considered a column with a diameter of 2 cm and varying bed depths, including 10 , 15 , and 20 . The breakthrough (C/C0 = 0.016) times were 31.0, 49.0, and 63.0 h and the exhaust (C/C0 = 0.90) times were 60.0, 90.0, and 110.0 h, respectively for As(III). For As(V), those were found to be (breakthrough times corresponding to C/C0 = 0.0033) 5.0, 11.0, and 18.0 h and 20.0, 27.0, and 36.0 h, respectively. The up-flow rate was maintained at 8 mL min−1. The As(III) and As(V) concentrations were 0.6 and 3 mg L−1. Bohart and Adams sorption model was employed to determine the important column design parameters. The column was designed by the bed-depth-service-time model. The adsorption capacity (N0) and the adsorption rate constant (K) calculated were 295.30 mg L−1 and 20.41 L mg−1 h−1, respectively, for As(III) and 599.82 mg L−1 and 0.233 L mg−1 h−1, respectively, for As(V). The effects on the variation of initial concentrations and flow rates were also investigated. The 10-cm exhaust bed (As(III)) was regenerated with 1M NaOH, and its performance was evaluated. An attempt has been made to minimize the As adsorbed exhausted sludge mixing with Portland cement and the prepared blocks were used for leaching tests in different inorganic mediums for 90 d; immobility was accounted from De values.

Fixed Bed Column Adsorption Studies Using Fly Ash for Removal of Cadmium from Aqueous Solution

In the present paper, adsorptive removal of cadmium from synthetic wastewater using a 2 cm diameter fly ash column was studied through three column adsorption experiments by varying column depths (10, 15 and 20 cm). Study results showed fly ash to be an effective adsorbent for cadmium removal. Column design parameters such as depth of adsorption zone (6 cm), critical bed depth (1.3 cm), adsorption capacity (480.82 mg/l) and adsorption rate constant (0.0111 l/mg min) are calculated using bed depth service time approach. Using the same method effect of varying flow rate (5, 8 and 10 ml/min) and initial cadmium concentration (15 and 20 mg/l) was studied and the corresponding model predicted service times conformed well with the experimentally obtained results from three more column studies. Negligible leaching of adsorbed cadmium from exposed fly ash column was observed during two desorption studies.

Оптимизация параметров конструкции вертикальных стоек металлорежущих станков по критерию достаточной жесткости при минимальном весе

Оптимизация параметров конструкции вертикальных стоек металлорежущих станков по критерию достаточной жесткости при минимальном весе

Fixed-Bed Column Study for the Removal of Strontium (II) Ions from Aqueous Solutions Using Expanding Rice Husk

This paper deals with removal of strontium ions from solution by expanding rice husk (ERH) in a fixed-bed column. The absorption characteristics of expanding rice husk for strontium ions were studied systematically. The effects of different column design parameters like bed depth, flow rate and initial strontium concentration on the equilibrium uptake of ERH for strontium ions were investigated. It was found that the equilibrium uptake (qeq(exp)) of the ERH increased with the increase in initial strontium concentration but decreased with the increase in flow rate and bed depth respectively. Strontium cumulative removals of 2.32 mg/g were obtained under the optimum operational conditions at a flow rate of 10 ml/min and bed depth of 6 cm. XPS analysis indicated that the Sr (II) ion was absorbed on ERH. The adsorption data fitted well with the bed depth service time (BDST) model.

Modeling of fixed-bed adsorption of fluoride on bone char using a hybrid neural network approach

This study introduces a hybrid model based on the Thomas equation and artificial neural networks (ANNs) for the modeling of unsymmetrical breakthrough curves obtained from the fluoride adsorption on bone char. Experimental results of kinetics, isotherms and breakthrough curves of fluoride adsorption on two commercial bone chars have been used for analyzing the capabilities and limitations of this hybrid ANN model. Performance of this hybrid model has been studied and compared with respect to the results of traditional linear regression of the Thomas breakthrough equation at different operating conditions of packed-bed adsorption columns. Results showed that an improvement in the modeling capabilities of Thomas model can be obtained using ANNs. Specifically, the hybrid ANNs–Thomas model showed determination coefficients higher than 0.9 and its average mean square errors are lower, up to 86%, than those obtained with the linear modeling approach. In fact, the present study illustrates that the improper handling of the Thomas model using traditional regression approach may lead to imprecise values of design parameters and erroneous conclusions of adsorption performance. On the other hand, the hybrid ANNs–Thomas model is useful for determining reasonable and accurate design parameters of packed-bed adsorption columns. This modeling approach can be useful for the process system engineering of dynamic adsorption systems involved in the field of water treatment and purification.

Energy saving methods for the separation of a minimum boiling point azeotrope using an intermediate entrainer

In this work two energy saving methods are presented for the separation of a minimum boiling point azeotrope by using an intermediate entrainer. Extractive distillation column configurations with conventional, thermally integrated and dividing-wall columns are used for comparison. These configurations are designed, rigorously simulated and optimized to minimize the Total Annual Cost and to reduce the energy requirement. A novel simple method is proposed based on a Genetic Algorithm to determine the main design and operation parameters of the dividing-wall column. The optimization algorithm is written in Excel Macro interconnected with the ChemCad process flow-sheet simulator. In terms of total annual costs, the extractive dividing-wall column was found to be the most economical scheme, followed by the thermally integrated and conventional extractive distillation methods.

Shear-Critical Impact Response of Biaxially Loaded Reinforced Concrete Circular Columns

A study on the vulnerability of biaxially loaded reinforced concrete (RC) circular columns in multi-story buildings under low- to medium-velocity impacts at shear-critical locations is presented. The study is based on a previously validated nonlinear explicit dynamic finite element (FE) modeling technique developed by the authors. The impact is simulated using force pulses generated from full-scale vehicle impact tests abundantly found in the literature with a view to quantifying the sensitivity of the design parameters of the RC columns under the typical impacts that are representative of the general vehicle population. The design parameters considered include the diameter and height of the column, the vertical steel ratio, the concrete grade, and the confinement effects. From the results of the simulations, empirical equations to quantify the critical impulses for the simplified design of the short, circular RC columns under the risk of shear-critical impacts are developed.

Fixed Bed Column Study for Adsolubilization of 2,4-D Herbicide on Surfactant Modified Silica Gel Waste

The fixed bed column study was conducted for the removal of 2,4-dichlorophenoxyacetic acid (2,4-D), a widely used herbicide from synthetically prepared wastewater using surfactant modified silica gel waste (SMSGW) as an adsorbing media. The adsorbing media was prepared by treating silica gel waste (SGW) with cationic surfactant. The removal was due to adsolubilization of 2,4-D molecules within the admicelles formed on the surface of SGW. The column having 2.5 cm diameter, with different bed heights such as 20, 30 and 40 cm were used in the study. The different column design parameters like depth of exchange zone, time required for exchange zone to move its own height, adsorption rate constant, adsorption capacity constant were calculated using BDST model. The SMSGW was found to be a very efficient media for the removal of 2,4-D from wastewater. Column design parameters were modeled for different field conditions to predict the duration of column run for practical application.

Adsorption and desorption characteristics of crystal violet in bottom ash column

This study described adsorption of Crystal Violet (CV) by bottom ash in fixed-bed column mode. Equilibrium of adsorption was studied in batch mode for finding adsorption capacity of bottom ash. In fixed bed column adsorption, the effects of bed height, feed flow rate, and initial concentration were studied by assessing breakthrough curve. The slope of the breakthrough curve decreased with increasing bed height. The breakthrough time and exhaustion time were decreased with increasing influent CV concentration and flow rates. The effect of bed depth, flow rate and CV concentration on the adsorption column design parameters were analyzed. Bed depth service time (BDST) model was applied for analysis of crystal violet adsorption in the column. The adsorption capacity of bottom ash was calculated at 10% breakthrough point for different flow rates and concentrations. Desorption studies reveals that recovery of CV from bottom ash was effective by using CH3COOH than H2SO4, NaOH, HCl and NaCl solutions.