Height Equivalent To A Theoretical Plate Research Articles

Zinc Isotope Effects in Benzo Crown Resin by Displacement Chromatography

The isotope effects of zinc were studied by displacement chromatography with a polymer-supported benzo crown resin packed in glass columns. The influence of migration distance on the zinc isotope effect was investigated. Migration distances from one to thirty meters were performed by feeding zinc chloride in dehydrated acetone solvent into the columns. The migration distance was proved to have no effect on the separation coefficient (ε); however, the migration distance clearly affected the slope coefficient (ks ). The height equivalent to a theoretical plate (HETP) was variable for each migration distance in the present work. The slope coefficient ks and HETP were 0.035 and 0.29 cm, respectively, at the 30m chromatographic operation under 298 ± 1K in the present work.

High enrichment of 15N by chromatographic chemical process

Nitrogen isotope enrichment experiments were conducted to obtain highly enriched 15N by ion-exchange process. 15NH 4Cl ( 15N = 80%) as feeding materials were used to perform the chromatographic operation with two different flow rates and column diameters. Both separation coefficient ( ɛ) and height equivalent to a theoretical plate (HETP) have same values in two run experiments. The value of HETP was more enlarged when high enrichment of 15N was obtained in comparison with that of low enrichment. 99.756% 15N and 13.63 g 15N whose percentage was over 99.0% were successfully achieved by 25 m chromatographic migration with the flow rate and column diameter at 50 cm 3/mL, 3.0 cm, respectively. High flow rate and large column diameter have advantages to the enrichment of 15N by ion exchange process.

High enrichment of 15N isotope by ion exchange for nitride fuel development

Two kinds of nitrogen-isotope enrichment experiments were conducted for the purpose of developing a process to obtain highly enriched 15N by ion-exchange chromatography. As the first stage experiments, high enrichment of 14N was carried out by displacement chromatography using columns packed with cation-exchange resin and feed ammonium ion of which 15N abundance is natural namely 0.36%. In the second stage, high enrichment of 15N was studied starting from ca. 80% enriched 15N feed material; after 30 m migration 99.67% 15N was obtained. The height equivalent to a theoretical plate (HETP) of ion-exchange separation is usually very small, but the results clearly indicate that the HETP is enlarged when the high enrichment zone of 14N or 15N is developed at the front or the rear band boundary, respectively. The information obtained is very important and should be useful for designing when the plant for the high enrichment isotope separation is designed.

Zinc Isotope Effects in Benzo Crown Resin by Displacement Chromatography

The isotope effects of zinc were studied by displacement chromatography with a polymer-supported benzo crown resin packed in glass columns. The influence of migration distance on the zinc isotope effect was investigated. Migration distances from one to thirty meters were performed by feeding zinc chloride in dehydrated acetone solvent into the columns. The migration distance was proved to have no effect on the separation coefficient (e); however, the migration distance clearly affected the slope coefficient (ks ). The height equivalent to a theoretical plate (HETP) was variable for each migration distance in the present work. The slope coefficient ks and HETP were 0.035 and 0.29 cm, respectively, at the 30m chromatographic operation under 298 ± 1K in the present work.

Suitability of Using Brass Ferrules as Packing in a Glass Distillation Column and Presenting a New Relationship between HETP and Pressure Drop

Brass Ferrules have been used as packing in a laboratory- scale glass distillation column approaching pilot plant size because of their availability in all sizes and low cost. The available size range is such that these ferrules could also be used in industry and the results of this study could be scaled up. The performance of the new packing has been compared with the performance of glass packing, and has proven to be more satisfactory with lower HETPs (Height Equivalent to a Theoretical Plate). Three systems were studied in this work, namely, ethanol/water, 1-propanol/water, and 1-butanol/water and the HETP of the brass packing in these systems was experimentally measured. Pressure drop and flooding have been studied together in this work and a new relationship has been presented that relates efficiency in terms of HETP to pressure drop, a parameter that can be measured readily in any column or predicted.

Thermodynamic and Kinetic Study of Adsorption of R,S‐α‐Tetralol Enantiomers on the Chiral Adsorbent CHIRALPAK AD

Experimental results for the separation of S,R‐α‐Tetralol enantiomers obtained on preparative columns packed with particle size 20 µm of chiral adsorbent CHIRALPAK AD are presented. The total porosity was measured by using the non‐retained compound 1,3,5‐Tri‐tert‐butylbenzene and was 0.61. The permeability of the bed packed with CHIRALPAK AD was calculated as 4.4×10−13 m2. The efficiency of columns was characterized by the height equivalent to a theoretical plate (HETP) and a linear dependency has been found over tested flow rates. The HETP of S‐α‐Tetralol and R‐α‐Tetralol calculated at the flow rate 5.0 cm3/min were 320 µm and 340 µm, respectively. Thermodynamic adsorption parameters enthalpy, ΔH and entropy, ΔS, have been calculated from van't Hoff plot. Equilibrium and kinetics of adsorption of single enantiomers and racemic mixture of α‐Tetralol on CHIRALPAK AD were evaluated as well. The parameters for multicomponent isotherm linear‐Langmuir model are presented. The breakthrough curves of α‐Tetralol enantiomers are simulated with a mathematical model that accounts for axial dispersion and linear driving force for the intraparticle mass transfer.

A simple and efficient approach for calculating permeability coefficients and HETP for rectangular columns

There had been little progress in development of the theoretical basis of rectangular chromatography columns until Spangler made great progress by using a more exact model than Golay's. Unfortunately, there was a deficiency in his calculations, which led to a conclusion inconsistent with the previous theories. In this paper, a simpler formula with defined variables was first established to calculate the mean permeability coefficient for a rectangular GC column. A formula was also established to calculate the height equivalent to a theoretical plate (HETP) for a rectangular column based on this work and the correction of Spangler's theory. By comparing both our predictions and Spangler's predictions with Golay's, respectively, we could demonstrate that our theory is more exact. Further, one parameter (A) was found to be not monotonous. This finding leads to the conclusion that the square column has the highest performance among all the rectangular-shaped columns used for chromatography, and that a width/depth ratio of around three is desirable if the column is used for mixing reactants in lab-on-a-chip systems, instead of for chromatography. The conclusions are applicable not only for gas but also for liquid chromatography columns.

Experimental characterization and modelling of analytical monolithic column

Hydrodynamics, equilibrium and kinetics of adsorption in a silica-based monolithic column Chromolith Performance RP-18e (Merck KgaA, Germany) have been studied. The column permeability was calculated according to the Darcy law for laminar flow. The efficiency of the monolithic column was characterized through the height equivalent to a theoretical plate (HETP) for myoglobin, phenol and progesterone. The 2-D single channel mathematical model has been applied to describe the adsorption dynamics. Parabolic velocity profile, axial and radial diffusion in the monolith channel, linear driving force model for the mass transfer in the monolith channel skeleton wall and linear adsorption equilibrium were assumed. The mathematical model gives good prediction of the experimental elution peaks.

Mass transfer characteristics of a structured packing for ammonia rectification in ammonia–water absorption refrigeration systems

In ammonia–water absorption refrigeration systems a purification process of the vapours produced in the generator is required. One type of equipment to carry out the purification process is a packed column. However, detailed experimental studies at the normal operating conditions found in ammonia–water absorption refrigeration systems have not been found. An experimental facility has been designed and built to study the ammonia–water rectification in packed columns. Experimental tests have been performed at the normal operating conditions found in the high-pressure stage of a small power ammonia–water absorption refrigeration system. In this paper, the experimental set-up is described and experimental results of the height equivalent to a theoretical plate (HETP) and the volumetric mass transfer coefficient of a rectifying section with the Sulzer BX packing are presented. The HETP values and the experimental mass transfer coefficients are compared with different data and correlations proposed in the literature; it has been found that the differences are appreciable.

Effect of the nature of the carrier gas on the chromatographic characteristics of monolithic silica capillary columns

Chromatographing a model mixture of hydrocarbons with various carrier gases (helium, hydrogen, nitrogen, carbon dioxide, and nitrous oxide) was used to study the separation ability of monolithic silica capillary columns. It was revealed that the nature of the carrier gas strongly affects the retention time of the sorbates and the height equivalent to a theoretical plate (HETP) of the column, with the values of both these parameters decreasing in the series He > H2 > N2 > CO2 ∼ N2O. This effect was found to be more pronounced for normal hydrocarbons than for their isomers. For chromatographing with CO2 or N2O under optimum conditions, the HETP was 25–30 μm, a value indicative of a higher specific efficiency of monolithic capillary columns. Theoretical correlations between the HETP and the properties of the mobile phase were considered. As a result, it was concluded that elevated pressures of the carrier gas, which are required to ensure the optimum operation of monolithic capillary columns, may affect the properties of the chromatographic system.

Theoretical Approximation for the Linear Flow of Carrier Gas through a Rectangular Gas Chromatogaphic Column

A simple relationship for the average linear velocity of carrier gas flowing through a rectangular gas chromatographic column is derived. Since the relationship agrees remarkably well with published experimental data taken from a variety of sources, it should be very useful in practical application. This is particularly true for micro-fabricated etched silicon columns that often have a rectangular cross-section. Knowledge of the average linear velocity facilitates calculation of the height equivalent to a theoretical plate (HETP), a measure of resolution for the column.

Chromatographic zinc isotope separation by phenol formaldehyde benzo crown resin

New types of phenol formaldehyde resin having benzo crown as a functional group were synthesized and applied to zinc isotope chromatographic operation. Zinc adsorption and isotope separation capacities were dramatically improved by using phenol formaldehyde benzo-15-crown-5 resin. Zinc batch adsorption tests were performed by various dehydrated organic solvents. Separation coefficient, ɛ 8.1 × 10 −4 and height equivalent to a theoretical plate (HETP) 0.105 cm for the isotopic pair of 68Zn/ 64Zn in phenol formaldehyde benzo-15-crown-5 resin were obtained in the case of acetone as the solvent at 298 ± 1 K.

Experimental and modeling study of adsorption in preparative monolithic silica column

The hydrodynamic, equilibrium and kinetics of adsorption in a silica-based monolithic preparative column Chromolith Prep. Si (Merck KgaA, Germany) have been studied. The inverse size-exclusion chromatography with polystyrene standards of narrow molecular size distribution and small tracer molecule has been used to measure the external and total porosity of the monolithic column. The column permeability was calculated according to the Darcy law for laminar flow. The efficiency of the monolithic column was characterized through the height equivalent to a theoretical plate (HETP) of phenol, ethyl vanillin and dimethyl phthalate. The separation efficiency does not decrease in the region of high flow rates. The adsorption isotherms of phenol, ethyl vanillin and dimethyl phthalate measured by frontal analysis were linear in the investigated concentration range. The 2D single channel mathematical model has been applied to describe the adsorption dynamics. The model assumes parabolic velocity profile, axial and radial diffusion in the monolith channel, linear driving force model for the mass transfer in the monolith channel skeleton wall and linear adsorption equilibrium. The model gives good prediction of the experimental breakthrough curves.

Hydrogen Isotope Separation by Combined Electrolysis Catalytic Exchange Under Reduced Pressure

At the National Institute for Fusion Science experimental studies on hydrogen isotope separation by a Combined Electrolysis Catalytic Exchange (CECE) process have been carried out in order to apply it to the system of water detritiation for D-D burning experiments of the Large Helical Device. As an improvement of the CECE process, we have developed a reduced-pressure method as a means of enhancing the separation factor. The feasibility of this method is examined through application to a CECE process using a prototype separation column. Hydrogen-deuterium isotope separation experiments are performed in the two cases where column pressures are 12 and 101 kPa, and the separation factors for hydrogen and deuterium are obtained as 6.8 and 5.6, respectively. It is confirmed that the present method is applicable and useful to the CECE process. The values of Height Equivalent to a Theoretical Plate (HETP) are estimated by analyses with the equilibrium stage model. The HETP values are 15 cm at 12 kPa and 13 cm at 101 kPa. The increase of superficial velocity with decreasing pressure may spoil the efficiency of the mass transfer.

Analysis of breakthrough dynamics in rectangular channels of arbitrary aspect ratio

AbstractAdsorption in rectangular and square channels is attracting great interest from various fields of research. In particular, in large scale applications the main interest is in the prediction of the performance of monoliths composed of several individual channels, while, in the field of microengineering, particular interest is in the separation performance of individual channels for the development of small‐scale analytical devices, that is, the lab on a chip. The design of all these units is based on the accurate representation of the breakthrough dynamics and the performance of the unit can be represented conveniently by the height equivalent to a theoretical plate (HETP). General simplified equations for the calculation of the HETP are derived for rectangular channels of arbitrary aspect ratio. The dispersion in the solid phase is corrected to take into account the effect of the adsorptive capacity in the four corners of the solid phase. A corrected thickness of the walls of the channels is predicted and shown to yield the exact HETP by comparing the analytical solution to the full 3‐D numerical solution. Numerical simulations are presented for representative gas and liquid systems. © 2005 American Institute of Chemical Engineers AIChE J, 2005

Investigations of a new field in gas chromatography: Capillary columns with a super-thick layer of stationary liquid phase

Basic characteristics (efficiency, selectivity, non-equilibrium) of capillary columns with a super-thick layer of stationary liquid phase are investigated. In contrast to traditionally used capillary columns with standard stationary phase thickness of 0.1–0.5 um, some new variables are now established. Firstly, the values of relative retention depend on carrier gas linear velocity. Secondly, the asymmetry of chromatographic peaks increased in accordance with the increase in carrier gas velocity. Thirdly, it was theoretically and experimentally shown that dependence of the height equivalent to a theoretical plate (HETP) on carrier gas velocity is linear. The above noted variables are evidences that the new type of GC is realized under these conditions. The use of capillary columns with super-thick layer of stationary liquid phase is practical when the following problems have to be solved: (1) Separation of highly volatile substances; (2) Preliminary concentration of trace compounds from strong diluted samples; (3) Improvements in measurement and accuracy due to the advantages of splitless injection into wide bore columns with super-thick films. Solutions to some analytical tasks while using super-thick stationary liquid phase are shown: (1) Large volume injection into capillary column with sample transfer speed up to 100 μL min −1; (2) Isothermal splitless injection; (3) Separation of low boiling compounds; (4) Separation of polar substances (alcohols).

Optimization of monoclonal antibody purification by ion-exchange chromatography: Application of simple methods with linear gradient elution experimental data

Simple methods for the optimization of ion-exchange chromatography of proteins in our previous papers were applied to cation-exchange chromatography purification of monoclonal antibodies (Mab). We carried out linear gradient elution experiments, and obtained the data for the peak salt concentration and the peak width. From these data, the distribution coefficient as a function of salt concentration, and the height equivalent to a theoretical plate (HETP) as a function of mobile phase velocity were calculated. The optimized linear gradient elution conditions were determined based on the relationship between buffer consumption and separation time. The optimal stepwise elution conditions were determined based on the relationship between the distribution coefficient and the salt concentration.

Preliminary Experiments on Hydrogen Isotope Separation by Water-Hydrogen Chemical Exchange under Reduced Pressure

A pressure-reducing method is used effectively in a water distillation process to enhance the equilibrium separation factor. The feasibility of the technique is established through application to a water-hydrogen chemical exchange process using a prototype separation column. Isotope separation experiments examining the water-hydrogen chemical exchange reaction are performed for column pressures of 12–101 kPa, and the separation factors for hydrogen and deuterium are obtained. The HETP (Height Equivalent to a Theoretical Plate) values were distributed in the range of 6 to 15 cm. By reducing the pressure in the column, the process temperature can be lowered without reducing the molar fraction of water vapor in the gas stream. It confirmed that the separation factors under reduced pressure are larger than under atmospheric pressure. This fact demonstrates the effectiveness of reduced pressure in water-hydrogen chemical exchange processes.

Prediction of HETP for randomly packed towers operation: integration of aqueous and non-aqueous mass transfer characteristics into one consistent correlation

Abstract Height equivalent to a theoretical plate (HETP) calculations, essential for the design of randomly packed distillation columns were extracted from the open literature to generate a working database including over 2350 measurements (only total molar reflux data). The merging of mass transfer characteristics from non-aqueous and aqueous separation experiments has instigated the generation of a consistent correlation predicting HETP. Based on results presented elsewhere for absorption and stripping conditions (Ind. Eng. Chem. Res. 41 (2002) 4911), a set of artificial neural network (ANN) correlations for the gas–liquid interfacial area ( a w ) and the pure local mass transfer coefficients ( k γ , γ=G or L) was proposed with the following dimensionless structures: a w / a T = f ( Re L , Fr L , Eo L , I , χ , K ) and Sh γ = f ( Re γ , Fr γ , Sc γ , χ ). The gas–liquid interfacial area and the pure local mass transfer coefficients were extracted using a reconciliation procedure which combined actually measured interfacial areas with pseudo-interfacial areas inferred from the actually measured volumetric mass transfer coefficients ( k L a w , K L a w , k G a w , K G a w —absorption and stripping) and HETP (distillation). The neural network weights of the two a w and k γ correlations were adjusted using a least-squared composite criterion simultaneously over the six mass transfer parameters’ databases. The optimized set of ANN correlations yielded an average absolute relative error (AARE) of 21.3% for the 2357 HETP measurements available. Likewise, the measured interfacial area and volumetric mass transfer coefficients (3770 data) were correlated with an AARE of approximately 26.5%, which undeniably proves the intimate correspondence of absorption and distillation mass transfer characteristics in randomly packed towers. HETP predictions remain as well in accordance with the physical evidence reported in the literature.

Modeling of the Catalytic Distillation Process for the Synthesis of Ethyl Cellosolve Using A Three-Phase Nonequilibrium Model

The catalytic distillation (CD) process for the synthesis of ethyl cellosolve from ethanol and ethylene oxide on molecular sieve catalyst NKC-01 in a 200 mm CD pilot column was simulated using the three-phase nonequilibrium model which was developed in our laboratory. The main feature of this model is that the actual rates for transport and reaction are used and the stage efficiency or HETP (height equivalent to a theoretical plate) is not required. The effect of multicomponent mass and heat transfer between vapor and liquid phases as well as between liquid and solid (catalyst) phases was taken into account according to the Maxwell-Stefan equations. The Newton-Raphson method was used to solve the model equations. The simulation profiles of the temperature and composition along the column are in good agreement with the pilot CD plant data obtained for the synthesis of ethyl cellosolve. Good agreement between model predictions and experimental data is also obtained for the yield and selectivity of the ethyl cellosolve. This model could be extended to simulate other CD processes and commercial scale CD plants.