HETP Values Research Articles

Kajian Meta-Analisis: Efektivitas Penggunaan Bahan Ajar terhadap Keterampilan Berpikir Kritis Berdasarkan Jenjang Pendidikan

Meta-analysis is a statistical method for combining quantitative results from several studies to produce an overall summary or empirical knowledge on a particular topic. This research aims to analyze the effectiveness of the use of teaching materials on students' critical thinking skills based on educational level. Research results that can be used in meta-analysis have certain characteristics/criteria. The analysis used is quantitative descriptive statistical analysis with the help of the OpenMEE application. Data analysis by calculating the Effect Size (ES) value from the mean value, Standard Deviation (SD), and number of samples (N) from each article analyzed. The overall average effect size is 3.801 in the high category (ES ≥ 0.8), and the P-Value value is <0.001, which means that the use of teaching materials provides significant effectiveness in critical thinking skills because the P-Value value is higher. smaller than 0.05. Meanwhile, the results of the heterogeneity test show that the Tauˆ2 value is 4.091, and the Het P-Value value is <0.001, which means it is significant. So it can be said that the Q statistic from the 17 studies has a variety of variances with diversity that is classified as very high with an Iˆ2 value reaching 97.1%, so there is potential for moderator variable analysis to be carried out. Furthermore, the effect size value based on level of education obtained an average effect size at the high school education level of 9.196, higher than other levels of education, which means that the use of teaching materials is more effective when used at the high school level compared to elementary, middle school and other educational levels. University, with P-Value < 0.001, which means that the use of teaching materials in high school provides significant effectiveness.

Improving design and scale-up of columns with structured packings by means of CFD

Structured packings in distillation columns present an opportunity for process optimization. Therefore, current design processes for columns with structured packings are evaluated with respect to their industrial applicability, and a power law equation is proposed for transferring HETP values of a reference system to a test system. A design process that includes CFD simulations is presented, and the CFD simulation setup is introduced. The validity of the simulation setup is examined with regard to the following mixtures: nitrogen/oxygen, chlorobenzene/ethylbenzene, and cyclohexane/n-heptane. Diffusion coefficients are varied in the simulation, and their influence on the HETP value is evaluated. The simulated HETP values are then compared with established mass transfer models and demonstrate a high level of agreement.

Design of frontal chromatography separation of 1-phenylethanol and acetophenone using a hydrophobic resin

Adsorption and chromatographic processes havegood potential in the purification of natural aromas produced via biocatalytic routes. This work deals with the recovery of 1-phenylethanol (PE) from mixtures containing different amounts of acetophenone (AP). Amberlite FPX68, an industrial adsorbent with high selectivity with respect to acetophenone, was chosen for the separation of PE and AP by frontal chromatography. Small-scale experiments were performed for two different feed compositions and various flow rates and bed lengths. Using the target purity of 99 %, promising yields close to 90 % were obtained. The breakthrough curves were fitted with the equilibrium dispersive model, which provided HETP values under the different conditions. The obtained dependences of HETP on flow velocity complied with the Van Deemter equation. The contributions of individual phenomena responsible for adsorption zone broadening were analyzed. The experimental and modelling results obtained for the small-scale column became the basis for the scale-up of frontal chromatography separation of PE with an annual capacity up to 500 kg.

Dynamic behavior of CO2 adsorption from CH4 mixture in a packed bed of SAPO-34 by CFD-based modeling

Abstract In this work, a dynamic non-isothermal adsorption process of CH4 and CO2 in a fixed bed of SAPO-34 particles was modeled by coupled DEM-CFD. This Euler–Lagrange method gives access to specification of each adsorbent pellet including location, temperature and concentrations, and facilitates study of phenomena like adsorption. Transport phenomena including heat and mass transfer in fluid and between solid and gas were taken into account. Eventually the model was validated by experimental results of breakthrough curve. Especially near wall channeling effect and the role of inlet feed velocity on the bed efficiency were addressed in this work. Local and bulk porosity values calculated using DEM model showed an acceptable agreement with previous empirical equations. Results indicated that this coupled method can be applied as a promising tool to study the mass transfer zone and efficiency of the adsorption process. The results revealed that as the feed continues to flow into the column, the lower layers of the adsorbent particles become practically saturated and then the mass transfer zone starts moving upward to a region of fresher adsorbent in the column. Also, the results showed that, at a low inlet velocity with a low Peclet number (Pe = 0.195), channeling effect is reduced and the diffusion mechanism controls the mass transfer. However, HETP enhances with increase in the feed gas velocity (Pe = 2.25) as well as increase in deviation from plug flow regime, and consequently the adsorption efficiency decreases. HETP decreases drastically at the beginning with increase in interstitial velocity. Increase in the interstitial velocity beyond a particular value of 0.5 cm s−1 leads to increase in the HETP value. This trend and presence of a minimum in this graph were explained based on Van Deemter concept.

A Simplified Method for Predicting the Effect of Temperature on the Separation Performance by Chromatography

A simplified method for predicting the effect of temperature on the separation performance by chromatography was developed. As a model separation system, two polyphenol component separation by polymer-resin chromatography with ethanol-water mobile phase was chosen. HETP values as a function of mobile phase velocity for a wide range of temperatures 15-45°C were well correlated by a single universal curve in the dimensionless HETP and the dimensionless velocity plots. A simplified equation that can predict the resolution was derived. The equation includes the temperature dependence of the distribution coefficients and the molecular diffusion coefficients. The relative separation performance (resolution) calculated by this equation showed that the existence of the maximum resolution depends on the temperature dependence of the distribution coefficients. Even when the resolution decreases with temperature, higher temperature operations may be advantageous as both the separation time and the separation volume decrease.

Basic separation efficiency and hydraulic data of MellapakPlus 452.Y structured packing under distillation conditions

We present pressure drop and HETP data for Sulzer MellapakPlus™ 452.Y packing measured using the C6/C7 system under total reflux at three pressures: 33 kPa, atmospheric pressure and 180 kPa. The data were obtained in a column with an inner diameter of 0.3 m with the bed consisting of 12 elements of packing (total height 2.52 m).The pressure drop data under the loading point were in good agreement with the data predicted by Sulcol software (v3.4.4, vendor provided); in the loading region, the Sulcol data were on the safe side. The maximum stable FG factor for the three pressures were 2.79, 2.41 and 2.17 Pa0.5, respectively. The HETP values for the expected industrial operating load range were almost constant, with mean values of 0.29, 0.28, 0.27 m obtained, respectively. Because the measurements were performed with different compositions of the C6/C7 mixture, recalculation utilizing known HETP dependence on the slope of the equilibrium curve was used to suppress the dependence of the separation efficiency on the composition.

Model Discrimination for Multicomponent Distillation – A Geometrical Approach for Total Reflux

AbstractWhile rate‐based models are available in commercial flowsheet simulation tools, packed distillation columns are still mostly designed based on the equilibrium stage model in combination with HETP values. In order to discriminate between both types of models in a simple way, this article proposes an algorithmic test, based on a geometric criterion for total reflux operation. Substantial differences are illustrated especially for wide‐boiling mixtures, while component‐specific mass transfer rates either increase or reduce the deviation. The derived results are validated by dedicated experiments.

Effect of the angle of rotation of structured packing layers on separation efficiency in distillation column

It is well known that a good quality of liquid distribution over the surface of structured packings is crucial for high performance of large diameter columns. The angle of rotation of the packing layers and their number are among the main parameters characterizing the distribution of liquid in a structured packing over the column cross-section and height. This paper presents investigation results on the influence of the rotation angle of structured packing layers on separation efficiency, pressure drop, distribution of local composition of mixture and local liquid flow rate under the packing. The experiments were carried out in distillation column with the internal diameter of 0.9 m on a structured packing with a specific area of 500 m2/m3, and the corrugation angle of packing equal to 45°. The mixture of refrigerants R114 and R21 at the pressure of 3 bar and total reflux was used as the working fluid. The column was packed with 11 packing layers with rotation angles of 20, 45, 70, and 90 degrees. According to experimental results, a decrease in the angle of packing layer rotation from 90 to 20 degrees leads to a decrease in separation efficiency, while the HETP value increases by 10–12%.

The Production of the Isotope 15N by Isotopic Exchange in Nitrox System at Pressure

The operation of 15N production plant at pressure of 0.7 +/- 0.05 bar in stable conditions at total reflux and in production is demonstrated. The 10M HNO3 flows used in the primary column were 6.6 L/h and 6.0 L/h, 47, respectively 33% higher than that of atmospheric pressure (4.5 L/h) and corresponding flow rates of the same column were 3.12 mL/cm2. min, respectively 2.83 mL/cm2.min for operation at pressure, compared to 2.12 mL/cm2�.min at atmospheric pressure. The 10M HNO3 flows used in the final column were 324 mL/h and 264 mL/h, 62, respectively 32 % higher than that of the atmospheric pressure (200 mL/h) and flow rates of that column were: 3.05 mL/cm2.min, respectively 2.49 mL/cm2.min, compared to 1.86 mL/cm2�.min for atmospheric pressure operation. The HETP values are lower for both separation columns operated at pressure and higher 10M HNO3 flow rates, that being an argument in the favour of operation the 15N production plant by isotopic exchange in Nitrox system at pressure. The nitrogen enriched in 15N losses in the waste sulphuric acid, evacuated at the bottom of product refluxer stage II, were : 5.18 -10.58 ppm of feeding with 10M HNO3 of the plant. Any losses of nitrogen enriched in 15N represent an additional uncontrolled production, which diminishes the production of 15N plant. In the case of operation at pressure the flows of H15NO3 extracted as plant product are higher than those corresponding to atmospheric pressure because the nitric acid solution is chemically equilibrated with nitrogen oxides at the operation pressure and temperature. At a pressure of 1 atm. in the 15N production plant the nitrogen content of nitric acid solution would be 10.919M instead of 10M.

Experimental and numerical study of mass transfer efficiency in new wire gauze with high capacity structured packing

ABSTRACTExperimental and numerical studies were conducted on the mass transfer efficiency of new wire gauze structured packing. For serving this purpose, various operational conditions were studied to assess the optimal parameters such as HETP of PACK-2100 in the distillation column. The results indicate that the HETP values are enhanced in comparison to conventional ones. In addition, the HETP slowly increases from 4 to 6 cm as mass flow rates of air and liquid flow are increased. The numerical simulations were also performed to describe the performance of the PACK-2100. The Eulerian-Eulerian multiphase approach is applied to calculate the value of HETP and pressure drop. The computational results confirmed that our experimental results. The average relative error between CFD predictions and the experimental data for the prediction of mass transfer efficiency is 20.45%.

Choosing the Right Model for Distillation Processes in Packed Columns: Theory and Experiments

Packed distillation columns are usually designed on the basis of a sequential approach, in which first the Equilibrium Stage (EQ) model is used to quantify the separation effort before the required packing height is determined by HETP values. This approach is often sufficient for process design and proper sizing of the column. However, in certain cases the combination of the EQ model and HETP values results in an inappropriate column design. The design accuracy can be improved using a rate-based (RB) approach. Unfortunately, there is no reliable heuristic available to decide which modeling approach should be chosen. Therefore, the current study investigates the need for rate-based modeling in distillation processes by systematically evaluating the differences between EQ and RB composition trajectories. A criterion based on the Euclidean distance is proposed to evaluate the differences between the EQ and RB trajectories. Then, by means of a selectivity analysis basic criteria for model discrimination are derived and validated experimentally. Generally, for wide boiling mixtures the differences between the EQ and RB trajectories are the most distinct. The differences in the trajectories can be further increased or decreased by component specific mass transfer.

Preparation, characterization and application of polymethacrylate-based monolithic columns for fast and efficient separation of alkanes, alcohols, alkylbenzenes and isomeric mixtures by gas chromatography

Application of monolithic columns in gas chromatography is still considered very limited. In this work, several polymethacrylate-based monolithic capillary columns were fabricated, characterized and used in gas chromatography. The five monomers used were: methyl methacrylate, (MMA), hexyl methacrylate (HMA), glycidyl methacrylate (GMA), 2-butoxyethyl methacrylate (BEMA) and isobornyl methacrylate (IBMA), while ethylene dimethacrylate was the crosslinker. The monoliths were synthesized in 30 cm length capillaries possessing inner diameters (i.d.) of 0.25 mm. The prepared monolithic columns were applied for separation of 3 series of homologous alkanes, alcohols and alkylbenzenes, as well as some isomeric mixtures. Van Deemter plots were used to optimize and compare the columns performance. The smaller methacrylates (MMA and GMA) exhibited higher porosity and permeability with low column backpressure values and poorer efficiency than the larger methacrylate monomers (HMA and BEMA). The columns prepared from IBMA monomer showed the highest pressure and the least separation efficiency. The fastest full separation of alkanes was achieved on HMA-co-EDMA column in about 3.0 min with resolution better than 2.73, while the fastest full separation of alcohols and alkylbenzenes was carried out using BEMA-co-EDMA column in less than 0.8 and 1.75 min with chromatographic resolution better than 1.27 and 1.85, respectively. Again, BEMA-co-EDMA column gave the best performance with the fastest and complete separation of all studied isomeric mixtures. For all tested series of solutes, the better separation efficiency was reached with tridecane, which gave 25,200 plates/m on the HMA-co-EDMA column. Another application was carried out using HMA-co-EDMA column for determination of myrcene and limonene, two monoterpenic isomers, in some fruit peels. Under the optimum GC conditions, a rapid separation of myrcene and limonene was achieved in less than 1.0 min with chromatographic resolution of 2.56. The highest contents of myrcene (0.131 mg/g) and limonene (1.225 mg/g) were measured in the hexane extracts of grapefruit and Egyptian orange, respectively. Finally, a comparison between the prepared columns and a commercial capillary column was performed. Based on the measured run time and HETP values, HMA-co-EDMA and BEMA-co-EDMA monolithic columns exhibited faster separation and higher efficiency for n-alkanes and alkylbenzenes than the TR-5 open tubular column, although they are 100 times shorter.

Preparation of Benzo-15-Crown-5 Adsorbents for the Separation of Lithium Isotopes by Displacement Chromatography

For decreasing the HETP value of a column packed with a crown ether adsorbent for the separation of lithium isotopes by displacement chromatography, adsorbents were prepared using porous silica beads having diameters of 60, 100, and 250 μm and benzo-15-crown-5 ether. The HETP values of the packed column were estimated by chromatographic experiments by data obtained from breakthrough curves. The HETP values decreased with the particle diameter of the adsorbent, and an HETP value of 0.16 mm was obtained for a particle diameter of 60 μm. Numerical simulation results suggested that the HETP value can be possibly reduced to the order of 10 μm by using an adsorbent with a particle diameter of 5 μm.

Development of an affinity cryogel for one step purification of lysozyme from chicken egg white.

In this study, a supermacroporous polyacrylamide cryogel was produced by cryo-polymerization and activated with Tris(hydroxymethyl)aminomethane (Tris-cryogel) to be applied as an affinity ligand for a one step purification of lysozyme (LYZ), directly from chicken egg white (EW). The Tris-cryogel presented interconnected pores with size varying in the range of 20-80μm and swelling capacity of 19.6±0.9g/g. The axial dispersion of the Tris-cryogel was analyzed at different flow velocities and mobile phase viscosities. It was verified that higher viscosity resulted in a higher degree of dispersion, causing the HETP values to increase from 0.04cm to 0.8cm. Adsorption isotherms were measured at 15°C and 35°C at pH 7.5. A Langmuir model was fitted to the equilibrium data, with a maximum adsorptive capacity of 285mg/g at 15°C and 363mg/g at 35°C. Thermodynamic analysis based on the Van't Hoff relationship showed that the process was spontaneous and enthalpically driven. Lysozyme was purified directly from egg white in a one step purification process at different pH values (7.5, 8.5 and 9.5). Independent of the pH, the specificity of Tris-cryogel for lysozyme adsorption was confirmed. At pH 7.5, yield and purification fold were higher (30% and 45). In addition, the effect of the dilution rate on egg white and flow velocity were also analyzed and it was shown that flow velocity did not affected purification and column efficiency, and that diluting the egg white increased yield to 70% with a purification fold of 23. Results show Tris-cryogel is a promising matrix for use in high throughput purification of lysozyme from egg white.

Hydraulic and mass-transfer characteristics of Raschig Super-Pak 250Y

Our paper presents hydraulic, hydrodynamic and mass-transfer characteristics of the Raschig Super-Pak 250Y high-capacity structured packing measured under absorption conditions. The measurements were performed in the absorption column of inner diameter of 0.29m using proven aqueous test systems. Measured data reveal excellent gas-phase mass-transfer performance and improved hydraulic behavior which is in agreement with the data provided by the vendor. There was found significant degree of the liquid-phase axial mixing on the packing. All six packing constants of the model proposed by Billet and Schultes (1999) were evaluated. The HETP values for distillation of C6/C7 and methanol/n-propanol mixtures were predicted using the BS-model with the evaluated constants and plug flow assumption. Predicted HETPs were found to be in a poor agreement with those measured under distillation conditions. However, we do not address this disagreement to fundamental impropriety of the test systems or the inability of the BS model to transfer the data from absorption conditions to distillation ones. We demonstrate that rather accurate values of HETP can be obtained when the influence of the liquid phase axial mixing is involved into the HETP prediction. The need for incorporation of the more sophisticated hydrodynamic models into simulation software becomes evident.

Separative Analyses of a Chromatographic Column Packed with a Core-Shell Adsorbent for Lithium Isotope Separation

A core-shell type adsorbent was proposed for lithium isotope separation by chromatography. Concentration profiles and its time variation in the column were numerically simulated. It became clear that core-shell type adsorbents with thin porous shell were saturated rapidly relative to fully porous one and established a sharp edge of adsorption band. This is very important feature because lithium isotope separation requires long-distance development of adsorption band. The values of HETP for core-shell adsorbent packed column were estimated by statistical moments of the step response curve. The value of HETP decreased with the thickness of the porous shell. A core-shell type adsorbent is, then, useful for lithium isotope separation.

Influence of porogen nature on the kinetic and potential efficiencies of divinylbenzene-based monolithic sorbents in gas chromatography

It has been shown that using Poppe curves for characterization of monolithic sorbents makes it possible to optimize conditions for both the synthesis of monoliths intended for high-speed analysis and achievement of the best separation efficiency. The influence of the nature of a porogen on the kinetic efficiency of monolithic sorbents in high-pressure gas chromatography has been considered. It has been found that the nature of the porogen alcohol determines to a considerable extent the structure of the monolith and its kinetic efficiency. The sorbents prepared with the use of octanol-1 and dodecanol-1 have shown the best kinetic characteristics; however, minimal HETP values have been observed for the columns prepared using hexanol-1 as a porogen.

Accurate measurements of the true column efficiency and of the instrument band broadening contributions in the presence of a chromatographic column

A rapid and simple validated experimental protocol is proposed for the accurate determination of the true intrinsic column efficiency and for that of the variance of the extra-column volume of the instrument used, the latter being obtained without requiring the removal of the chromatographic column from the HPLC system. This protocol was applied to 2.1mm×100mm columns packed with sub-3 (2.7μm Halo Peptide ES-C18) and sub-2μm (1.6μm prototype) core–shell particles. It was validated by observing the linear behavior of the plot of the apparent column plate height versus the reciprocal of (1+k′)2 for at least three homologous compounds, with a linear regression coefficient R2 larger than 0.999. Irrespective of the contribution of the several, different instruments used to the total band broadening, the same column HETP value was obtained within 5%. This new protocol outperform the classical one in which the chromatographic column is replaced with a zero dead volume (ZDV) union connector to measure the extra-column volume variance, which is subtracted from the variance measured with the column to measure the intrinsic HETP. This protocol fails because it significantly underestimates the system volume variance.

Efficiency of supercritical fluid chromatography columns in different thermal environments

The efficiency of a packed column eluted with supercritical carbon dioxide at 323K and outlet pressures from 90 to 150bar was studied with the column in two different thermal environments. The 150mm×2.0mm ID stainless steel column was packed with spherical 5-μm porous silica particles with a covalently bonded nonpolar stationary phase, and the test solutes were normal alkanes. When operated in a convective air bath the column exhibited severe efficiency losses when its outlet pressure was below 120bar. The efficiency of the same column enclosed in a shell made of foam insulation was restored at low outlet pressures down to 100bar. The van Deemter plots showed an abnormal dependence of the plate height (HETP) on the flow rate at low outlet pressures, exhibiting a maximum in the HETP at flow rates around 1mL/min and a 20-bar pressure drop. The large efficiency losses at low outlet pressures are due to radial temperature gradients associated with enthalpic expansion and cooling of the mobile phase. The separations were simulated by a numerical model that accounts for axial and radial gradients in the temperature and density along the column. The abnormal van Deemter plots arise from competing processes affecting the radial distribution of the solute migration velocity along the column. The negative impact on efficiency is greatest when the density profile of the mobile phase along the column is close to the critical isopycnic line. The efficiency improves at increased flow rates because of increased cooling at larger pressure drops and increased density along the entire length of the column. The model predicts the unusual trends in the van Deemter plots, but the calculated results at low outlet pressures are strongly influenced by small variations in the porosity distribution in the column, limiting the accuracy of the predicted HETP values. In spite of these difficulties, the model has enabled a detailed analysis of the effects of temperature, pressure and flow rate on the thermal properties of the mobile phase, and their impact on the radial distribution of the solute velocities along the column. This work provides a better appreciation of the factors that cause excess efficiency loss at low outlet pressures, a phenomenon that lacked a convincing explanation for over 40 years. Finally, a simplified form of the model, which ignores the radial gradients, provided accurate results only at the highest outlet pressure. Calculations done by the simplified model are much faster, and it can be recommended for simulation of SFC processes at sufficiently high outlet pressures.

Advantages of core–shell particle columns in Sequential Injection Chromatography for determination of phenolic acids

Currently, for Sequential Injection Chromatography (SIC), only reversed phase C18 columns have been used for chromatographic separations. This article presents the first use of three different stationary phases: three core–shell particle-packed reversed phase columns in flow systems. The aim of this work was to extend the chromatographic capabilities of the SIC system. Despite the particle-packed columns reaching system pressures of ≤610PSI, their conditions matched those of a commercially produced and optimised SIC system (SIChrom™ (FIAlab®, USA)) with a 8-port high-pressure selection valve and medium-pressure Sapphire™ syringe pump with a 4mL reservoir and maximum system pressure of ≤1000PSI. The selectivity of each of the tested columns, Ascentis® Express RP-Amide, Ascentis® Express Phenyl-Hexyl and Ascentis® Express C18 (30mm×4.6mm, core–shell particle size 2.7μm), was compared by their ability to separate seven phenolic acids that are secondary metabolite substances widely distributed in plants. The separations of all of the components were performed by isocratic elution using binary mobile phases composed of acetonitrile and 0.065% phosphoric acid at pH 2.4 (a specific ratio was used for each column) at a flow-rate of 0.60mL/min. The volume of the mobile phase was 3.8mL for each separation. The injection volume of the sample was 10μL for each separation. The UV detection wavelengths were set to 250, 280 and 325nm. The RP-Amide column provided the highest chromatographic resolution and allowed for complete baseline separation of protocatechuic, syringic, vanillic, ferulic, sinapinic, p-coumaric and o-coumaric acids. The Phenyl–Hexyl and C18 columns were unable to completely separate the tested mixture, syringic and vanillic acid and ferulic and sinapinic acids could not be separated from one another. The analytical parameters were a LOD of 0.3mgL−1, a LOQ of 1.0mgL−1, a calibration range of 1.0–50.0 (100.0)mgL−1 (r>0.997) and a system precision of 10mgL−1 with a RSD ≤1.65%. The high performance of the chromatography process with the RP-Amide column under optimised conditions was highlighted and well documented (HETP values ≤10μm, peak symmetry ≤1.33, resolution ≥1.87 and time for one analysis <8.0min). The results of these experiments confirmed the benefits of extending chromatographic selectivity using core–shell particle column technology in a SIC manifold.