Columns similarity

An explosive decomposition in an ethylene oxide (EO) distillation column, similar in its results to that described in Section 7.3.2, may have been set off by polymerization of EO in a dead-end spot in the column base where rust, a polymerization catalyst, had accumulated. Such deadends should be avoided. However, it is more likely that a flange leaked the leaking gas ignited and heated an area of the column above the temperature at which spontaneous decomposition occurs. The source of ignition of the leak may have been reaction with the insulation, as described... 

SFC has been performed with either open capillary columns similar to those used in GC or packed columns transferred from LC, and the instrumentation requirements differ for these two approaches [12]. This chapter will focus on the use of packed column technology because of its dominance in the area of pharmaceutical compound separations. Current commercial instrumentation for packed column SFC utilizes many of the same components as traditional LC instruments, including pumps, injection valves, and detectors. In fact, most modem packed column SFC instm-ments can also be used to perform LC separations, and many of the same stationary phases can be used in both LC and SFC [9]. 

A new generalised correlation for pressure drop in packed columns, similar to Figure 11.44, has been published by Leva (1992), (1995). The new correlations gives a better prediction for systems where the density of the irrigating fluid is appreciably greater than that of water. It can also be used to predict the pressure drop over dry packing. 

Equation 12.22 relates the compositions of vapor and liquid streams passing each other in the stripping section of a column. Equation 12.22 can be used together with vapor-liquid equilibrium calculations to calculate a composition profile in the stripping section of the column, similar to that of the rectifying section of the column as described above. The calculation is started with an assumed bottoms composition and Equation 12.22 applied repeatedly with vapor-liquid equilibrium calculations working up the column. 

In many early studies, the rate of vaporisation of liquids into an air stream was measured in a wetted-wall column, similar to that shown in Figure 12.3. Fogarithmic plots of d/zG and Re = dup/fi gave a series of approximately straight lines and d/zc was proportional... 

From the analysis given already of the diffusional nature of absorption, one of the outstanding requirements is to provide as large an interfacial area of contact as possible between the phases. For this purpose, columns similar to those used for distillation are suitable. However, whereas distillation columns are usually tall and thin absorption columns are more likely to be short and fat. In addition, equipment may be used in which gas is passed into a liquid which is agitated by a stirrer. A few special forms of units have also been used, although it is the packed column which is most frequently used for gas absorption applications. 

A procedure for the preparation of finely divided MnO is to alternate layers of vermiculite and manganous oxalate in a column similar to that shown in Fig. 3.4. Initial activation is performed by heating the evacuated column to 330°C for 6 h. The resulting green MnO is pyrophoric and must not be exposed to a sudden inrush of air. The predominant reaction with oxygen, Eq. (2), results in a brown-black product so visual inspection of the column readily indicates its degree of... 

Samples are injected onto the turbulent-flow column similar to single-column methods. The analytes of interest are retained in the turbulent-flow column while the large macromolecules are eluted to waste. Once the analytes are separated from the matrix, the samples are then eluted into the analytical column. The characteristics of the analytical column determine the peak shape and separation seen at the MS detector. Flow rates which are compatible with the mass spectrometer can then be used and the chromatograms are based on conventional HPLC parameters. The key to dual-column methods is that the retentive properties of the analytical column must be sufficiently stronger than that of the turbulent-flow column the dual-column approach is performed in such a manner so that the mobile-phase composition needed to elute the analyte from the turbulent-flow column does not elute the analyte from the analytical column. The sample is then focused at the head of the analytical column until the mobile-phase conditions are changed to elute the analyte. The choice of columns is critical to the success of dual-column methods. Table 10.2 lists some of the applications of dual-column methods found in the literature. 

Alkenes and alkynes obviously don t fit easily into these categories as they have no bonds to heteroatoms. Aikenes can be made from alcohols by dehydration without any oxidation or reduction so it seems sensible to put them in the alcohol column. Similarly, alkynes and aldehydes are related by hydration/dehydration without oxidation or reduction. 

Figure 6.12 illustrates this effect. As more LLK component comes in with the feed stream, more depression occurs in the rectifying section temperature profile. If we control a tray temperature near the top and the amount of LLK in the feed increases, the temperature on this tray will start to go down. We will increase heat input to drive it back to its setpoint value, and this will push more HK component out the top. Therefore holding a constant temperature on a tray near the top of the column w ould result in significant variations in the amount of heavy key component in the distillate product. All of the LLK components must go out the top of the column, and there is nothing we can do about it once these components enter the column. Action must be taken in the upstream column to keep LLK components out of this column. Similar effects occur in the stripping section and near the base when variations occur in the amount of HHK components in the feed. Now temperatures rise as more heavy components enter the column, and we drop more LK component into the bottoms product if we hold a constant temperature on a tray near the base of the column. 

Running the extract on a GC-MS system. The extract will be injected in a GC-MS system in scan mode using a column similar to the main column for the GC-O experiment. The n-alkane mixture will also be injected under the same conditions, and a screening will be carried out to obtain the MS spectrum and potential identification of those peaks eluting at approximately the Retention Index of the target odor zones. 

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