Middle section

Figure 12-42. Results of internal chlorine gas fire and extensive corrosion in centrifugal compressor. Middle section of shaft with extensive damage to loss of center compression wheels. Note that ferric chloride is present.

One feature common to both designs in Figures 12.21 and 12.22 is that single-feed columns were used with the entrainer being mixed with the feed. In the case of the ethanol-water-ethylene glycol, the operation leaves for the top and bottom sections of the column do not meet, and there is a gap. In some systems, it is possible to bridge the gap between the operation leaves between the top and bottom sections by creating a middle section in the... 

Figure 12.25 The difference point allows the pinch point curves for the middle section operation leaf to be constructed. 

Bottom Product B with a straight line joining the Distillate D and Entrainer Feed E, as shown in Figure 12.24. Pinch point curves for the middle section can now be constructed by drawing tangents to the residue curves from the difference point (net overhead product). This is shown in Figure 12.25 for the system ethanol-water-ethylene glycol. The area bounded by the pinch point curves defines the middle section operation leaf. 

As long as this middle section operation leaf intersects with those for the top section (above the entrainer feed) and the bottom section (below the feed point for the feed mixture), the column design will be feasible. Note that there will always be a maximum reflux ratio, above which the separation will not be feasible because the profiles in the top and bottom sections will tend to follow residue curves, which cannot intersect. Also, the separation becomes poorer at high reflux ratios as a result of the entrainer being diluted by the reflux of lower boiling components. 

The size and shape of the middle section operation leaf depends on the location of the difference point, which in turn depends on the flowrate of entrainer. There will be a minimum flowrate of entrainer for feasible design. Above the minimum flowrate, the actual flowrate of the entrainer is an important degree of freedom for optimization. 

Figure 12.26 Middle section mass balances for a two-feed column.

Either Equation 12.28 or Equation 12.32 can be used in conjunction with vapor-liquid equilibrium calculations to calculate the section profile for the middle section of the two-feed column. 

A collaboration that has a distinguished head object can serve as the implementation of a type. Like a type, such a collaboration can appear within a three-part box. The difference is that the middle section now includes actions (directed or not) along with the collaborating types and links (directed or not) between them. 

Internal actions are depicted as actions, directed or not directed, between the collaborators inside the middle section of the box. These actions also have specifications either in the body of the box, with explicit participants, or within the receiver types if they are directed actions. Alternatively, the specs can be written elsewhere, fully prefixed with the appropriate participant information. 

Invariants can be written inside the middle section of the box and apply to both internal and external actions of this collaboration. 

This equation describes the middle section (0.225 < e < 4.44) of the space-filling curve for the sphalerite type structure plotted (with log scales) in Fig. 4.22. 

The middle section of a curve may cross some important points as previously marked on the graph. Make sure that the curve does, in fact, cross these points rather than just come close to them or you lose the purpose of marking them on in the first place. Always try to think what the relationship between the two variables is. Is it a straight line, an exponential or otherwise and is your curve representing this accurately ... 

Fig. 8.5. SEM pictures of activated tungsten wire emitters (a) overview showing the thin tungsten wire close to the holders and the whisker-bearing middle section, (b) detail of the middle with the whiskers resolved. By courtesy of Carbotec, Bergisch Gladbach, Germany.

The flow structure in a tall vertical bubble column was analyzed using deterministic techniques. The characterization of the two-phase flow structure was realized in the middle section where the flow is fully developed (measuring section). Three cases under different volume fraction of liquid were shown. The results can be resumed as follows ... 

The temperature in the middle section was varied from 40°C -70 C as required to maintain a final cotton moisture content of 3-4%. The total water-to-fiber ratio was 55/1 for this experiment and represents a minimum for wetting under these conditions. 

The majority of physisorption isotherms (Fig. 1.14 Type I-VI) and hysteresis loops (Fig. 1.14 H1-H4) are classified by lUPAC [21]. Reversible Type 1 isotherms are given by microporous (see below) solids having relatively small external surface areas (e.g. activated carbon or zeolites). The sharp and steep initial rise is associated with capillary condensation in micropores which follow a different mechanism compared with mesopores. Reversible Type II isotherms are typical for non-porous or macroporous (see below) materials and represent unrestricted monolayer-multilayer adsorption. Point B indicates the stage at which multilayer adsorption starts and lies at the beginning of the almost linear middle section. Reversible Type III isotherms are not very common. They have an indistinct point B, since the adsorbent-adsorbate interactions are weak. An example for such a system is nitrogen on polyethylene. Type IV isotherms are very common and show characteristic hysteresis loops which arise from different adsorption and desorption mechanisms in mesopores (see below). Type V and Type VI isotherms are uncommon, and their interpretation is difficult. A Type VI isotherm can arise with stepwise multilayer adsorption on a uniform nonporous surface. 

The poster text is divided into the same general IMRD sections as the journal article Introduction, Methods, Results, and Discussion. Similarly, most posters include an Acknowledgments section, some have an abbreviated References section, and all have a title and author list. Most posters do not include an abstract, in part because of space limitations and in part because an abstract already appears in the conference proceedings. Like the journal article, the IMRD structure of the poster follows an hourglass shape. The top (Introduction) and bottom (Discussion) sections have a broader focus, while the middle sections (Methods and Results) have a narrower focus. Each section of the poster can be divided into individual moves or steps that guide viewers in a conventional way through the content of each section. These moves are analyzed in the next part of the chapter. 

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