Middle product

If the feed is dominated by the middle product (typically more than 50 percent) and the lightest product is present in small quantities (typically less than 5 percent), then the arrangement shown in Fig. 5.106 can be an attractive option. This time the light product must find its way up the column past the sidestream. Again, unless the light product is a small flow and the middle product a high flow, a... 

Figure 5.12 Composition profiles for the middle product in the columns of the direct sequence show remixing effects. (From Triantafyllou and Smith, Trans. IChemE, part A, 70 118, 1992 reproduced by permission of the Institution of Chemical Engineers.)...

Both the side-rectifier and side-stripper arrangements have been shown to reduce the energy consumption compared with simple two-column arrangements. This results from reduced mixing losses in the first (main) column. As with the first column of the simple sequence, a peak in composition occurs with the middle product. Now, however, advantage of the peak is taken by transferring material to the side-rectifier or side-stripper. 

In some areas, mn-of-mine coal is separated into three products a low gravity, premium-priced coal for metakurgical or other special use, a middlings product for possible boiler firing, and a high ash refuse. The complete preparation of coal usuaky requires several processes. 

Mittel-ol, n. middle oil medium-heavy oil. -ost, m. Middle East, -produkt, n. middle product intermediate middlings, -punkt, m. center, central point, mittels, prep, by means of,... 

In summary, single-column sidestream arrangements can be attractive when the middle product is in excess and one of the other components is present in only minor quantities. Thus, the sidestream column only applies to special circumstances for the feed composition. More generally applicable arrangements are possible by relaxing the restriction that separations must be between adjacent key components. 

If the second and third columns in Figure 11,7a are operated at the same pressure, then the second and third columns could simply be connected and the middle product taken as a sidestream as shown in Figure 11.7b. The arrangement in Figure 11.7b is known as a prefractionator arrangement. Note that the first column in Figure 11,7b, the prefractionator, has a partial condenser to reduce the overall energy consumption. 

Fig.i General biosynthetic pathways for the production of alcohol, aldehyde, and acetate ester pheromone components in female moths. Top production of saturated fatty acids. Middle production of monounsaturated fatty acids and limited chain shortening produces intermediate compounds that can be reduced to an alcohol. Aldehyde and acetate ester pheromones are produced by an oxidase and acetyl-transferase, respectively. Bottom biosynthetic pathway for the production of the acetate ester pheromone components in the cabbage looper moth, Trichoplusia ni. The CoA derivatives are reduced and acetylated to form the acetate esters. Additional pheromone components include 12 OAc and ll-12 OAc... 

The carbocation produced in this El elimination i s 2° and can either eliminate to give the first alkene, or can rearrange by a methyl shift to a 3° carbocation which would produce the last two products. The middle product is major as it is tetrasubstituted versus disubstituted for the last structure and monosubstituted for the first structure. 

Thermally coupled design 1 and 2 should be considered as alternatives to two-column design, if less than half of the feed is middle product. 

Some polymers can crystallize, and the change in the structure can be found by comparing the difference of X-ray before and after polymerization. The X-ray spectrum of chitosan (1) middle product (2) and final product (3) is shown in Fig. 5.14. 

Chitosan had strong diffraction absorption peaks at 10° and 20°. In the spectrum of middle product N-(3-chloro-2-hydroxyl)-propylchitosan, the 10° characteristics absorption peaks had disappeared, and the 20° peak had weakened. This was because the amino in the chitosan molecules reacted with EPI and formed an intermediate which contained chlorinated hydroxypropyl, resulting in weakened crystallinity. The 20° peak of immobilized chitosan (3) was further weakened compared with (2) because it was the grafted product of N-(3-chloro-2-hydroxyl)-propylchitosan with CD and had a further lower crystallinity [40]. 

Anion structure Early product Middle products Late products ... 

If the middle product dominates in the feed (that is, >50%) and the heaviest product is in small quantity (that is, <5%), then favor the side stream below the feed... 

In summary, in the ideal case, SSCs can be attractive either when the middle product dominates in the feed and one of the other components is in only minor quantities, or when the middle-boiling components are trace components, or when they are used as prefractionators. Thus, SSCs can only be applied under special circumstances of feed composition and product specification (Smith, 2005). 

Fig. 60. New vials with viscoelastic substances The top product contains no air bubbles at all. The middle product houses one air bubble, while the bottom product displays two air bubbles (at both ends of the syringe)...

Destruction of the middle Production of drinkable lamella crude fibre mono-cell suspensions... 

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