Large-diameter Column Research Articles

A foam OTEC system

Experiments are described which attempt to incorporate the main features of a foam OTEC System. These features include foam generation, foam rise, foam breaking, and finally separation of liquid and vapor. Our foam generator formed foam at rates as high as would be desired in a commercial plant, ~1 g/cm 2 sec. The rise of the foam, accompanied by a drop in temperature, was as expected by theory. The foam breaking, and the subsequent separation of liquid and vapor, presented no problem. Totally unexpected was the dominant role played by the wall drag in our 4 in diameter, 30 ft high column. Experiments were consistent, however, with a very simple expression for the variation of the drag coefficient with the foam parameters of mass flow rate and density. For the large diameter columns envisioned for commercial plants, wall drag will play only a minor role. Likewise unexpected was the large surfactant concentration (~1000 ppm) required to maintain complete foam stability to the top of the column. The periodic appearance of large bubbles at lower concentrations may be generated by our high rates of shear strain, greater than 20 sec. Another problem which must be solved is common to all open cycle systems. This is deaeration.

On the analysis of phenylthiohydantoin amino acids by high performance liquid chromatography

The key experimental variables and the corresponding separations of synthetic mixtures of phenylthiohydantoin amino acids achieved by high performance liquid chromatography have been abstracted from the literature and are listed in tabular form. From this table it is seen that the large majority of separations reported since 1977 have been performed utilizing stainless steel tubing of large internal diameter (i.d.≥3.9 mm). The reason for the widespread adoption of this particular practice is that a number of earlier studies have indicated that use of small diameter columns leads to significant loss of chromatographic resolution. An experimental study, employing two commercial chomatographic systems and tubings of differing internal diameter (i.d. 4.5 to 1.5 mm), leads to the conclusion that columns of reverse phase support material packed in stainless steel micro-bore tubing (i.d.≤2 mm) can effect separation of phenylthiohydantoin amino acids with similar efficiency as larger diameter columns. The practical advantages of employing micro-bore columns in general are discussed and adoption of micro-bore columns for the routine separation of this particularly important group of amino acid derivatives is recommended.

A low-cost medium-pressure liquid chromatography system for preparative separations

On the basis of theoretical and economic considerations a medium-pressure liquid chromatography system for preparative separations was developed. The choice of stationary phases with an average particle size of about 50 μm allows a dry column packing technique and makes possible short separation times with low pressure drop. The columns can therefore be constructed of glass. Their design is very simple, the end fitting is uniform for all column sizes. A special column head ensures optimum solvent distribution which enables the use of large diameter columns without loss in performance. Measurements under analytical conditions confirmed HETP's less than 300 μm for all column sizes.

Separation of polymyxins and octapeptins by high-performance liquid chromatography

Seventeen decapeptide antibiotics of the polymyxin group and nine octapeptide antibiotics of the octapeptin group have been successfully separated on a commercial reversed-phase material with tartrate buffer-acetonitrile containing sodium 1-butanesulphonate and sodium sulphate as the mobile phase. All of the components of EM49 (a complex of octapeptins A and B) were preparatively separated by use of a large-diameter column, and the structures of two new components, named octapeptins A 4 and B 4, were deduced from the results of the fatty acid and amino acid analyses.

Preparative reversed-phase chromatography of polar and non-polar metabolites on columns packed with micronized xad-2 resin

Coarse-grade XAD-2 resin has been micronized (medium particle size 12 μm) and used as a support for preparative high-resolution liquid chromatography. By equilibration with single-phase mixtures of water, a lower aliphatic alcohol and a hydrophobic solvent a reversed-phase partition system is formed in situ. This chromatographic technique is characterized by a large capacity, a high power of resolution and a high degree of selectivity and reproducibility, and versatile application in the isolation of polar and non-polar drug metabolites or naturally occurring compounds from complex mixtures is possible. The examples given relate particularly to the separation of water-soluble, non-extractable compounds, such as glucuronides or other conjugates, and amino acids on large-diameter columns (up to 2.5 cm).

Investigation of the fluid dynamics of gas flow in large-diameter columns

The velocity field of a gas flow immediately above the packing surface of a chromatographic column loaded and compacted by various methods has been investigated using a laser anemometer.

Design and construction of bored large-diameter pile columns

Design and construction of bored large-diameter pile columns

Comparison of broadening patterns in regular and radially compressed large-diameter columns

Summary The differential broadening pattern of an inert solute injected centrally into a regular (A) and a radially compressed (B) column has been studied. The two columns exhibit identical properties when operated in the infinite diameter mode. A marked difference, to the advantage of column B, develops as the solute becomes appreciably exposed to the wall region. At its fullest extent, the wall effect accounts for a nearly 2.5-fold increase in plate height for column A compared with a 1.5-fold increase for column B. This behavious is rationalized in terms of a semi-theoretical model that takes the radial diffusivity, the radial dependence of the lateral plate height and the peak local velocity into account. It is further shown that the solute radial concentration profile departs significantly from a truncated gaussian shape. The actual profile can be expressed as a Bessel function series.

Geometry Factors for TE0mn Resonance Cavities for Diagnostics of Large-diameter Plasmas

Mode-suppressing resonators oscillating in TEomn modes only are suggested here for the diagnostics of large-diameter plasma columns. Circular cylindrical cavities composed of electrically insulated parallel rings have been found to give the best Q values. Geometry factors are presented for TEomn resonance mode cavities (m = 1, ... , 7; arbitrary n) for different density profiles and filling ratios, allowing absolute electron density determinations.

Large diameter columns for preparative scale high speed liquid chromatography

Large diameter columns for preparative scale high speed liquid chromatography

A study of the shape of chromatographic bands in preparative gas chromatographic columns

In preparative gas chromatography it has been observed that the maximum flow-rate and concentration of a component occur in the centre of the column. The reasons for such phenomena are discussed. Some procedures for decreasing the HETP of large diameter columns are described.

Residence time distribution of the dispersed phase in a spray column

AbstractA dye tracer technique was utilized to measure the residence time distribution of the drops in a spray column, operating with a dispersed or a dense packing of drops, for a wide range of flow rates, in a 15 cm.in diameter, 150 to 160 cm. long column proper.For dispersed packing of drops and for flow rates below the onset of coalescence, the flow of the drops was approximately plug flow, with a variance of the residence time distribution of 0.095. For flow rates above the onset of coalescence within the column, the variance increased sharply to 0.55 and decreased at higher flow rates.For dense packing of drops the variance of the residence time distribution was in the range of 0.1 to 0.5. This variance is attributed to the effect of bypassing water and kerosene near the wall of the column. A mathematical model based on this effect showed reasonable fit with the experimental results. This model predicts an approach to plug flow of the drops for large diameter columns.

Modification of preparative gas chromatographic trap.

Micropreparation with an analytical column and macropreparation with a large-diameter column in preparative gaschromatography were examined. By connecting a heating tube for obtaining an optimum temperature gradient between the column and the trap, and by selecting its length and diameter together with the most favorable gradient of temperature, the recovery was raised to 92%.

Studies on Removal of Radioactive Mist by Plate Column

The authors have made a study on entrainment, in which the probability of mist passing through a plate is considered. A mathematical analysis was performed for large diameter column, that is, one in which consideration is given to backmixing in a plate column. The analysis and subsequent examination have revealed that the decontamination factor D.F. increases as the state of the liquid changes from a condition of complete mixing to that of plug flow.

Large Diameter Columns in Preparative Chromatography

Large Diameter Columns in Preparative Chromatography

Performance of an internally baffled multistage extraction column

AbstractInternally agitated extraction columns generally require increasing heights for a theoretical state for the larger column diameters. The present work describes a design developed to minimize this objection and presents the performance data on a system considered easy to extract and on systems considered difficult to extract. H.E.T.S. values as low as 3 in. on the first system and 4 in. on the second type of system were obtained in an 11½ in I.D. glass column. The stage efficiencies were correlated as a function of power input per unit volume of solvent throughput and the ratio of the flow rate of the dispersed phase to that of the continous phases. The supplementary effect of packing was studied and found to be most beneficial in the system which has a low interfacial tension and is considered easy to extract. By the use of this particular arrangement of internal baffles, it is believed possible, in the larger diameter columns, to reduce the height to a ratio of H.E.T.S. to diameter below the value of ¼ obtained in the present column.