Column Systems

This ammonia is recycled to the reactor via a compressor and a heater. Liquid ammonia is used as reflux on the top of the absorber. The net amount of carbon dioxide formed in the reactor is removed as bottom product from the absorber in the form of a weak ammonium carbamate solution, which is concentrated in a desorber-washing column system. The bottom product of this washing column is a concentrated ammonium carbamate solution which is reprocessed in a urea plant. The top product, pure ammonia, is Hquefted and used as reflux together with Hquid makeup ammonia. The desorber bottom product, practically pure water, is used in the quench system in addition to the recycled mother Hquor. 

The impurity problem noted in the previous paragraph was solved by the introduc tion of the Linde double-column system shown in Fig. 11-118. Two rectification columns are placed one on top of the other (hence the name double-column system). 

FIG. 15-38 Extraction rates for sieve-plate and modified biihhle-plate columns. System benzoic acid-water-toliiene, except where noted. To convert feet to meters, multiply by 0.3048 to convert inches to centimeters, multiply by 2.54. [Alletion, Strom, and Treyhal, Trans. Am. Inst. Cbem. Eng., 39, 361 (1943) Row, Kojfolt, and Withrow, ihid., 37, 559 (1941) Treyhal and Dumoulin, Ind. Eng. Cbem., 34, 709(1942).]... 

A single-column system for liquid-phase carhon adsorption is used in situations where the following conditions prevail laboratory testing has indieated that the breakthrough curve will be steep the extended lifetime of the earbon at normal operating conditions results in minor replacement or regeneration eosts the eapital... 

NOTE To develop reasonably good data for scale-up to full plant design, it is important to have the operation of the pilot column system as near as possible to the anticipated plant conditions. The most critical factors, flow rate and feed impurity concentration, must be constant for the entire test run. 

As the flow rate and quantity of liquor are the most important controllable variables in developing design data, a feed pump suitable for accurate and continuous flow is required. Depending on the size of the pilot column system, the use of peristaltic, diaphragm, piston-type or centrifugal pumps are recommended. The feed pump should be used in combination with a volumetric or gravimetric flow control... 

Tsutsumi, A., Nieh, J.Y. and Fan, L.S., 1991. Role of the bubble wake in fine particle production of calcium carbonate in bubble column systems. Industrial and Engineering Chemistry Research, 30, 2328-2333. 

Four column systems are available from Amersham Pharmacia Biotech that can be used to pack SEC media for various applications at the laboratory scale. These include C, XK, SR, and HR column systems. All of the laboratory-scale columns are constructed with borosilicate glass tubes. Columns for larger scale process applications include INdEX, BPG, EineLINE, BPSS, and Stack columns. The larger scale columns are constructed to meet stringent validation requirements for the production of biopharmaceuticals. Each of the column types are described. 

The XK column system is a medium-pressure jacketed glass column system designed for operating pressures up to 5 bar (0.5 MPa). Column dead volumes are less than 0.1% of the total column volume. Wetted materials include EPDM, TEFZEL, superpolyoxymethylene, and flurorubber. Columns use nylon nets of 10-)Lim mesh size and may be used with most SEC media with particle diameters >20 /xm. Columns are intended for use with aqueous solutions and... 

Stack columns are a modular process system that allows several column units to be stacked in series. This column system is well suited for packing soft compressible gels in short segments that can then be hooked in series. The... 

For the separation of large DNA fragments greater than 1000 bp, a four-column system is typically required. The baseline resolution of DNA fragments... 

The large pore structure of the TSK-GEL G6000PW allows it to separate large molecules such as pBR322 plasmid from contaminating RNAs and proteins in a much shorter time frame than other methods (23). A two column system of G6000PW (7.5 mm i.d. X 60 cm) was used to separate the cleared lysate and phenol extract of the plasmid as shown in Fig. 4.34 (page 130). The plasmid... 

The elution behavior of various polymers near their critical adsorption point with silica gel packings and various eluents has been studied (12). It was of interest to apply hybrid column systems composed of active ( critical ) packings (silica gels) in combination with nonactive (nonadsorptive) PS/DVB and DVB-based gels. Some PS/DVB and DVB gels exhibited rather strong... 

Figure 1.5 Representation of a coupled column system consisting of a primary column and two secondary columns (reproduced with permission from reference (30)).

Most developments in the past two decades, however, have involved coupled column systems which are much more amenable to automation and more readily permit quantitative measurements, and such systems form the subject of this present book. A review on two-dimensional GC was published (43) in 1978 (and recently updated (29)), and the development by Liu and Phillips in 1991 of comprehensive 2D GC marked a particular advance (33). The fundamentals of HPLC-GC coupling have been set out (37) with great thoroughness by Grob. Other work on a number of other aspects of multidimensional chromatography have also been extensively reviewed (44,45). 

V. Karl, H-G. Schmair and A. Mosandl, Simultaneous stereoanalysis of 2-alkyl-branched acids, esters and alcohols using a selectivity-adjusted column system in multidimensional gas cliromatography , 7. Chromatogr. 587 347-350(1991). 

Figure 4.1 Schematic diagram of a coupled column system. The first column (ID) is connected to the second column (2D) tlirough the interface or valve system. The interface can be a diiect coupling, a live T-union, a complex multiport valve, or a thermal or cryogenic modulation system. The stimulus can be the switching of the valve, abalancing pressure to divert flow towards 2D, an added flow that is used in pressure tuning, or the drive mechanism for the modulator. The line to detector 1 will normally be a non-retaining section of column. In a two-oven system, ID and 2D will be in different ovens the dotted line indicates separately heated zones.

Figure 11.4 Chromatograms of plasma samples on a silica-chiralcel OJ coupled column system (a) plasma spiked with oxprenolol (internal standard) (b) plasma spiked with 040 p-g/ml metyrapone and 0.39 p-g/ml metyrapol (racemate) (c) plasma sample obtained after oral administration of 750 mg metaiypone. Peaks are as follows 1, metyrapone 2, metyrapol enantiomers 3, oxprenolol. Reprinted from Journal of Chromatography, 665, J. A. Chiarotto and I. W. Wainer, Determination of metyrapone and the enantiomers of its chfral metabolite metyrapol in human plasma and urine using coupled achfral-chfral liquid cltro-matography, pp. 147-154, copyright 1995, with permission from Elsevier Science.

Recently, multidimensional GC has been employed in enantioselective analysis by placing a chiral stationary phase such as a cyclodextrin in the second column. Typically, switching valves are used to heart-cut the appropriate portion of the separation from a non-chiral column into a chiral column. Heil et al. used a dual column system consisting of a non-chiral pre-column (30 m X 0.25 mm X 0.38 p.m, PS-268) and a chiral (30 m X 0.32 mm X 0.64 p.m, heptakis(2,3-di-(9-methyl-6-(9-tert-butyldimethylsilyl)-(3-cyclodextrin) (TBDM-CD) analytical column to separate derivatized urinary organic acids that are indicative of metabolic diseases such as short bowel syndrome, phenylketonuria, tyrosinaemia, and others. They used a FID following the pre-column and an ion trap mass-selective detector following the... 

Paper strip chromatography showed approximately equal amounts of substrate and a more polar product (A -pregnadiene-9a-fluoro-11/3,l6a,17a,21-tetrol-3,20-dione 16,21-diacetate) together with very small amounts of two less polar products. Partition chromatography of 0.25 gram of the residue (diatomaceous earth column system 2 parts ethyl acetate,... 

Applications of structured packing into ethylene plant s various column systems [119] have been successfully achieved, but the individual manufacturers must be consulted to use their most directly applicable pilot and commercial data, which are generally not published. The use of published general correlations should only be used for a first or approximation design, while the delicate or important final design must be performed in cooperation with the manufacturer. 

The pump consists of two cylinders and a single common piston. The expression of the solvent to the column is depicted in the upper part of figure 9. As the piston progresses to the right, solvent is pumped to the column system but at the same time fresh solvent is being withdrawn into the right hand chamber from the solvent supply system. At the point where the piston arrives at the extent of its travel, a step in the driving cam is reached and the piston is rapidly reversed. 

Most laboratories now employ C30 columns for separation of carotenoids from complex matrices. There are several examples for separation of carotenoids from foods such as orange, watermelon, mango, camu-camu, carrot, spinach, tomato, " sweet com, and potato. The C30 column systems shown in Table... 

Catechin-immobilizing polymer particles were prepared by laccase-catalyzed oxidation of catechin in the presence of amine-containing porous polymer particles. The resulting particles showed good scavenging activity toward stable free l,l-diphenyl-2-picryl-hydrazyl radical and 2,2 -azinobis(3-ethylbenzothiazoline-6-sulfonate) radical cation. These particles may be applied for packed column systems to remove radical species such as reactive oxygen closely related to various diseases. 

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