Condensation edges

In moist enviromnents, water is present either at the metal interface in the fonn of a thin film (perhaps due to condensation) or as a bulk phase. Figure A3.10.1 schematically illustrates another example of anodic dissolution where a droplet of slightly acidic water (for instance, due to H2SO4) is in contact with an Fe surface in air [4]. Because Fe is a conductor, electrons are available to reduce O2 at the edges of the droplets. 

Drawdown from the die to nip is typically ca 10%. Sheet extmsion requires that the resin be of high melt viscosity to prevent excessive sag of the melt between the die and the nip. The melt should reach the nip before touching any other part of the middle roU to prevent uncontrolled cooling of the resin. The appearance of the lower surface of the sheet is deterrnined by the middle roU, ie, its poHsh, surface temperature, and freedom from condensed materials. The upper surface is cooled by air and has a more glossy appearance. Neither the top roU nor the bottom roU greatly affect the appearance of the top surface of the sheet. Edges of the sheet are trimmed. 

Thin-Film Evaporators. There are two types of thin-film evaporators commonly used in industrial appHcations. The first type introduces feed material into the center of a rotating heated conical receiver. Centrifugal force causes the feed to travel to the outer edge of the conical receiver where it is coUected and drawn off as residue. During the process, the heat causes the volatile components to be driven from the feed. These volatile components are condensed on a chilled surface of the evaporator and coUected as distUlate. 

Condensation of an aniline with a dione with loss of water provides enamine 16. Ketone protonation and cyclization forms 18 followed by loss of water provides quinoline 4. Some have suggested the formation of dication 19 as a requirement to cyclization. Cyclization of 19 to 20 and subsequent conversion to quinoline 4 requires loss of water and acid. Another rendering of the mechanism takes into account participation of an electron-donating group (EDG), which stabilizes intermediate 21. 

Condensate, Ibs/hr (Equation 2-133) or for pipe, Williams and Hazen constant for pipe roughness, (see Cameron Table 2-22 and Figure 2-24) or flow coefficient for sharp edged orifices... 

Water treatment monitoring and control is often a knife-edge operation and must be tailored to the overall operation of the boiler because waterside and gas-side problems usually are interlinked. Consequently (and as with other types of WT boiler), not only should the utility boiler FW be essentially free of dissolved oxygen to prevent waterside pitting corrosion of the economizer and other boiler components, but also the temperature must be high enough to prevent dewpoint condensation and subsequent acid attack on the gas side of the economizer tubes. 

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