Column Operation Procedure

Starting at the column base and working upward, find  

Repeat until the number of times equation (19.4) has been used equals 

Use the y thus calculated for the feed tray. Then switch operating lines and find  

Repeat equations (19.6) and (19.7) until they have been used Nt — 

ODmpare last y = yr with specified Xd. If does not match within a preselected tolerance, go back to step 1, assume a new value of R, and repeat steps 2-6. 

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Regardless of the procedure used, certain initial steps must be taken for the determination or specification of certain product properties and yields based on the TBP distillation curve of the column feed, method of providing column reflux, column-operating pressure, type of condenser, and type of side-cut strippers ana stripping requirements. These steps are developed and ilhistrated with several detailed examples by Watkins (op. cit.). Only one example, modified from one given by Watkins, is considered briefly here to indicate the approach taken during the initial steps. 

Other control methods. A cychng procedure can be used to set the pattern for column operation. The unit operates at total reflux until equilibrium is established. Distillate is then taken as total draw-... 

In this chapter, the elution curve equation and the plate theory will be used to explain some specific features of a chromatogram, certain chromatographic operating procedures, and some specific column properties. Some of the subjects treated will be second-order effects and, therefore, the mathematics will be more complex and some of the physical systems more involved. Firstly, it will be necessary to express certain mathematical concepts, such as the elution curve equation, in an alternative form. For example, the Poisson equation for the elution curve will be put into the simpler Gaussian or Error function form. 

It is seen that, for GC packed columns operated under the conditions assumed, the two factors contributing to dispersion by resistance to mass transfer are of the same order of magnitude. Consequently, equations (20) and (21) cannot be simplified and must be used in their existing form for all optimization procedures using packed GC columns. If the conditions differ significantly from those assumed, then by using the same procedure the possibility of modifying expressions (20) and (21) can be reexamined. 

The unit operating philosophy and its apparent operating limits often dictate unit constraints. For example, limitations on the main column bottoms temperature, the flue gas excess oxygen, and the slide valve delta P often constrain the unit feed rate and/or conversion. Unfortunately, some of these limits may no longer be applicable and should be reexamined. Some of them may have resulted from one bad experience and should not have become part of the operating procedure. 

During the synthesis of operating procedures, the operating state may be required to satisfy certain quantitative constraints. For example, during the operation of a reactor, the temperature may not be allowed to exceed a certain maximum, or the distillate from a distillation column may be required to have a minimum purity. Two chemicals may not be allowed to mix if the temperature is below a minimum. These constraints involve numerical values and may be stated as follows ... 

A standard operating procedure states that a column must have an efficiency > 30 000 theoretical plates/m. Which of these 15 cm columns meets the specification ... 

For all other types of column configurations, the operation procedures in startup, production and shutdown period will be slightly different. 

According to the recommended operating procedure for the analysis of CWC-related chemicals by GC (24) using SE-54 and OV-1701 columns (25 m x 0.32 or 0.25 mm ID (internal diameter), 0.25. im film thickness), the following conditions are recommended Injector temperature 250 °C, detector temperature 280 °C, temperature program initial temperature 40 °C for 1 min, heating rate 10 °C min-1 to 280 °C for 10 min. However, the GC conditions depend on the injection techniques used, the columns, the sample types, and the analytical demands if GC is used for rapid sample screening or if maximum resolution is needed, the selected GC conditions are different. 

According to the recommended operating procedure for the analysis of CWC-related chemicals by GC (24), the solvent blank, sensitivity, and column performance tests should be carried out to check... 

The analysis in Secs. 3.1.2 and 3.1.3 is important whenever product specs are not well defined, or whenever there may be an incentive to generate a product better than the specs. The analysis applies both to new and existing columns. In existing columns, this optimization is often incorporated in a computer control strategy and performed online. When computer control is unavailable, the optimization can be performed off-line and translated into operating procedures. 

Previous work with Oldershaw columns (209-211), however, spells a note of caution to Fair et al. s conclusion. For a fixed system, higher Oldershaw column efficiencies were measured under cellular foam conditions than under froth conditions. For this reason, Gerster (212) warned that when cellular foam can form, scaleup from an Oldershaw column may be dangerous. The conclusions presented by Fair et al. (208) do not extend to Oldershaw columns operating in the Cellular foam regime. Other considerations for scaleup from pilot columns (above) may also be important. The scaleup procedure recommended by Fair et al. (208) is... 

An investigation was therefore made on the effects of ionic strength and column washing procedures. The results were analyzed and specific recommendations were made for operational changes results and recommendations are given in this report. 

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