Condenser elevation

Air-cooled surface condensers. Figure 8.11 shows a surface condenser elevated above the steam turbine. This creates an additional problem, in that moisture from the turbine exhaust steam will accumulate in the bottom of the turbine case. A special drain line from the turbine s case is needed to prevent condensate backup from damaging the spinning wheels. 

Constructive criticism, in teams, 915 Contact barometric condensers, elevating, 40-41 Containment approach, 876... 

Reactions with Ammonia and Amines. Acetaldehyde readily adds ammonia to form acetaldehyde—ammonia. Diethyl amine [109-87-7] is obtained when acetaldehyde is added to a saturated aqueous or alcohoHc solution of ammonia and the mixture is heated to 50—75°C in the presence of a nickel catalyst and hydrogen at 1.2 MPa (12 atm). Pyridine [110-86-1] and pyridine derivatives are made from paraldehyde and aqueous ammonia in the presence of a catalyst at elevated temperatures (62) acetaldehyde may also be used but the yields of pyridine are generally lower than when paraldehyde is the starting material. The vapor-phase reaction of formaldehyde, acetaldehyde, and ammonia at 360°C over oxide catalyst was studied a 49% yield of pyridine and picolines was obtained using an activated siHca—alumina catalyst (63). Brown polymers result when acetaldehyde reacts with ammonia or amines at a pH of 6—7 and temperature of 3—25°C (64). Primary amines and acetaldehyde condense to give Schiff bases CH2CH=NR. The Schiff base reverts to the starting materials in the presence of acids. 

Michael condensations are catalyzed by alkaU alkoxides, tertiary amines, and quaternary bases and salts. Active methylene compounds and aUphatic nitro compounds add to form P-substituted propionates. These addition reactions are frequendy reversible at high temperatures. Exceptions are the tertiary nitro adducts which are converted to olefins at elevated temperatures (24). 

Vacuum Outgassing and Permeability. Under vacuum, modified ethylene—tetrafluoroethylene copolymers give off Htde gas at elevated temperatures. The loss rate is about one-tenth of the acceptable maximum rates for spacecraft uses. Exposing 750-pm specimens for 24 h at 149°C to a high vacuum results ia a maximum weight loss of 0.12% volatile condensible material is less than 0.02%. 

A proposed method which avoids cyanide consists of treating gold ore with gaseous chlorine at elevated (<250° C) temperatures to volatilise gold as chloride Au2Clg [12446-79-6] or AuMCl, (M = Fe [12523-43-2] A1 [73334-09-5], or Ga [73334-08-4]) and recovering it by condensation (23). 

Polymerization. Thermal polymerization or curing of an ink film at elevated temperatures can foUow many different chemical paths. Condensation and cross-linking reactions may be accompHshed with or without the use of catalysts. However, this method of drying generally has not been widely used for printing inks, except those used for metal and glass decoration, and some clear coatings. 

Fig. 3. Rough layout sketch (/) the two fined heaters F-1 and F-2 are located together but are separated from the other equipment with a subpipeway connecting the process area to the heater area (2) the reboiler E-2 is located adjacent to its column, T-1. The preheat exchanger E-4 is located adjacent to tower T-3 (J) the elevated overhead condenser E-3 is located next to the overhead accumulator V-1. Also, the ain condenser EE-3 is located adjacent to its overhead accumulator V-2 (4) the rest of the ain coolers (EE-1—3, -5) are grouped together ia a common fan stmcture (5) all equipment and related piping is routed to and from the existing piperack saving the addition of a new piperack (6) all pumps (P-1—P-6) are located ia a row under the piperack, and each...

When alloy piping or large bore piping is required, the associated equipment is located together as much as possible to keep the pipe mns short, preferably nozzle-to-nozzle by avoiding the piperack. Items such as elevated overhead condensers are located near the source and destination. Similarly, thermosyphon reboHers need to be placed adjacent to the column they reboH. Where gravity flow is required, these lines must be kept short and sloped. Space allocation for future additions must also be considered. 

Overhead condensers sometimes need to be located in the stmcture. Usually, partial condensers need to be elevated above the reflux accumulator. Considerable stmcture cost reduction can be achieved if the process can use grade-mounted condensers. Mounting the exchangers at grade may require them to be designed with subcooling so that the reflux accumulator can be located above the condenser. This should be considered as part of the process design. 

Phenolic Resins. At elevated temperatures, phenoHc resins are cured with polysulfide resins through a condensation reaction. The product may be considered a block copolymer of the rigid phenoHc resin and the flexible polysulfide. Thus, the polysulfide acts to flexibiHze the resulting polymer. 

Evaporation and Distillation. Steam is used to supply heat to most evaporation (qv) and distillation (qv) processes, such as ia sugar-juice processiag and alcohol distillation. In evaporation, pure solvent is removed and a low volatiUty solute is concentrated. Distillation transfers lower boiling components from the Hquid to the vapor phase. The vapors are then condensed to recover the desired components. In steam distillation, the steam is admitted iato direct coatact with the solutioa to be evaporated and the flow of steam to the condenser is used to transport distillates of low volatiHty. In evaporation of concentrated solutions, there may be substantial boiling poiat elevation. For example, the boiling poiat of an 80% NaOH solution at atmospheric pressure is 226°C. 

Initially, the source of environmental risk from cooling water was assumed to be the pollutant discharged, ie, heat, in the form of the elevated temperature of the water released from the condensers. Heat is now recognized as being only one of several potential risks of power station cooling (Fig. 2). 

By regulating the neutralizing amine feed rate, the condensate pH can be elevated to within a desired range (eg, 8.8—9.2 for a mixed copper—iron condensate system). 

Zinc does not react with nitrogen, even at elevated temperatures but zinc nitride, Zn N2, forms with ammonia at red heat. Zinc sulfide, the most common form of zinc in nature, is not reduced direcdy in commercial practice because of reactions of the zinc vapor during condensation. Rather, the sulfide is burned (roasted) to the oxide plus sulfur dioxide before reduction. However, zinc can be reduced to the metal at ca 1300°C with carbon or iron. 

Catalysts in this service can deactivate by several different mechanisms, but deactivation is ordinarily and primarily the result of deposition of carbonaceous materials onto the catalyst surface during hydrocarbon charge-stock processing at elevated temperature. This deposit of highly dehydrogenated polymers or polynuclear-condensed ring aromatics is called coke. The deposition of coke on the catalyst results in substantial deterioration in catalyst performance. The catalyst activity, or its abiUty to convert reactants, is adversely affected by this coke deposition, and the catalyst is referred to as spent. The coke deposits on spent reforming catalyst may exceed 20 wt %. 

Evaporative crystalli rs generate supersaturation by removing solvent, thereby increasing solute concentration. These crystallizers may be operated under vacuum, and, ia such circumstances, it is necessary to have a vacuum pump or ejector as a part of the unit. If the boiling poiat elevation of the system is low (that is, the difference between the boiling poiat of a solution ia the crystallizer and the condensation temperature of pure solvent at the system pressure), mechanical recompression of the vapor obtained from solvent evaporation can be used to produce a heat source to drive the operation. 

Because of their ordered stmcture, molecular sieves have high capacity at low water concentrations and do not exhibit a capiHary condensation pore-filling mechanism at high water concentrations. The desiccating properties of the material are stiU good at elevated temperatures (Fig. 10). A dew point of —75° C can be obtained in a gas dried at 90°C with a molecular sieve that adsorbs water to the level of 1 wt %. In normal operations at ambient temperature, dew points of < — 100° C have been measured. 

Other methods of generating a-aminoketones in situ are common, if somewhat less general than the methods already described. 2-Nitrovinylpyrrolidine, which is readily available, yields 2,3-bis(3-aminopropyl)pyrazine on reduction and this almost certainly involves ring opening of the intermediate enamine to an a-aminoketone which then dimerizes under the reaction conditions (Scheme 59) (78TL2217). Nitroethylene derivatives have also served as a-aminoketone precursors via ammonolysis of the derived epoxides at elevated temperatures (Scheme 60) (76S53). Condensation of 1,1-disubstituted hydrazine derivatives with a-nitro-/3-ethoxyethylene derivatives has been used in the synthesis of l,4-dialkylamino-l,4-dihydropyrazines (Scheme 61) (77S136). 

Under normal operating conditions, the concentration of the trioxide is unlikely to exceed 10 ppmv, but this is sufficient to elevate the acid dew point to around 422 K (300°F). This places a limit on the lowest acceptable back-end temperature if acid condensation and resulting corrosion problems are to be avoided. 

Modern analytical pyrolysis has conventionally been canied out only by thermal energy to break some covalent bonds in the sample molecules at elevated temperatures to produce smaller and/or volatile fragments (pyrolyzates). On the other hand, the reactive pyrolysis in the presence of organic alkaline, such as tetramethylammonium hydroxide [(CH / NOH] (TMAH) has recently received much attention especially in the field of chai acterizing condensation polymers. 

Thin films of metals, alloys and compounds of a few micrometres diickness, which play an important part in microelectronics, can be prepared by die condensation of atomic species on an inert substrate from a gaseous phase. The source of die atoms is, in die simplest circumstances, a sample of die collision-free evaporated beam originating from an elemental substance, or a number of elementary substances, which is formed in vacuum. The condensing surface is selected and held at a pre-determined temperature, so as to affect die crystallographic form of die condensate. If diis surface is at room teiiiperamre, a polycrystalline film is usually formed. As die temperature of die surface is increased die deposit crystal size increases, and can be made practically monocrystalline at elevated temperatures. The degree of crystallinity which has been achieved can be determined by electron diffraction, while odier properties such as surface morphology and dislocation sttiicmre can be established by electron microscopy. 

---