Operations condensation

There is a Second Law thermodynamic advantage in operating an expander at as low a temperamre as possible. In most applications it has been aiTanged to discharge just above tlie dew point of tlie expanded gas. If the cold compressed gas could enter tlie expander at or near its dew point, the expander would then operate condensing and at the lowest possible temperamre. Such condensate has traditionally been troublesome in turbines, but tliis has been solved in modern turboexpanders. 

Often in plant operations condensate at high pressures are let down to lower pressures. In such situations some low-pressure flash steam is produced, and the low-pressure condensate is either sent to a power plant or is cascaded to a lower pressure level. The following analysis solves the mass and heat balances that describe such a system, and can be used as an approximate calculation procedure. Refer to Figure 2 for a simplified view of the system and the basis for developing the mass and energy balances. We consider the condensate to be at pressure Pj and temperature tj, from whence it is let down to pressure 2. The saturation temperature at pressure Pj is tj. The vapor flow is defined as V Ibs/hr, and the condensate quality is defined as L Ibs/hr. The mass balance derived from Figure 2 is ... 

In 1974 the Atlantic City Electric Co. placed Unit 3 of its B L England Station into commercial operation. Condenser cooling for the unit is provided by circulating sea water in a closed-cycle, natural-draft system. The cooling tower selected for the site was a hyperbolic, counterflow unit. The thermal test instrumentation procedures and test data as well as drift measurement results are given. The paper indicates that the tower operates within design specifications for thermal performance and that it meets the environmental criteria regarding the drift. 

Low-presstire Turbines.—The capacity of an existing reciprocating engine plant (even though operated condensing) may be increased from 60 to 100 per cent by the appropriate installation of a turbine receiving steam exhausted by... 

Alkynyltrichlorotin reactions. The reagents are generated from 1-alkynes by treatment with SnCU-BujN in CH2CI2. Thus alkynylation of aldehydes, acetals, and enones (1,4-mode) is achieved under mild conditions using a one-pot operation. Condensation of silyl enol ethers and ketones with 1-alkynes. Both alkylide-... 

To facilitate removal of water vapor, a small amount of inert gas (e.g., nitrogen, argon, or helium) heated electrically to 20 C-30°C is injected into the bed of dried granules. The gas stream is fed to the lower chamber through a porous metal-ceramic ring embedded in the chamber wall just above the screw conveyor. The evaporated moisture is removed from the inert gas in two alternately operated condensers [88]. Although the basic model of the dryer is designed for liquid feeds, semisolid materials such as... 

Sublimed moisture vapor desublimes to ice on a cooling agent operated condenser. 

The vacuum applied to all stages should be the highest level to be used in operation. Condensers, circulating pumps, and condensate removal systems can be used to handle the water evaporated during the test. Under no circumstances should the absolute pressure go below 0.6 kPa, where evaporative cooling of the water will take the temperature to the freezing point. 

Under normal circumstances, compressed air is used to "fluff spent resins, which are then transferred in demineralized water through a transfer line between the tanks. But a resin block developed in the transfer line driving water back through the isolation valve between the demineralizer and the condensate pumps. As a result, water entered an instrument air line through a check valve that had frozen open. This apparently caused the polisher inlet and/or outlet isolation valves to drift toward the closed position. The accident began when all the isolation valves on the condensate polishers closed. This in turn caused one of the two operating condensate pumps and both of the condensate booster pumps to trip initiating the TMI-2 accident at 4 00 36 a.m. on Wednesday, March 28, 1979. 

The question whether also the liquid-like fluid may exist in micropores has been solved theoretically. Using mean field and density gradient methods, Evans and his co-workers "(ref.21" have shown that adsorbed fluid "condensation" should disappear, when the diameter R of the cylindrical micropores approaches to d the molecular diameter. According to the simplest form of their theory the critical temperature T Cml of the fluid confined in cylindrical micropores is determined by the approximate relationship (T -T (m))/T d/R, where T is the bulk critical temperature. From this relation it follows that e.g. benzene (d O.4-0.68 nm, cf. "(ref.3)") adsorbed at room and higher temperatures on zeolites and microporous active carbons behaves as a supercritical fluid. But the co-operative condensation of benzene at room temperatures is not excluded in large supermicropores of radii R>1.2 nm, ... 

CO-workers, the co-operative condensation of benzene confined in the supermicropores of a.c. prepared from CgFg, seems to be presented. This follows from the low value imO.A2 of the Amagate equation. But this equation is not the most appropriate for the description of properties of fluids condensable in supermicropores. In the future the energetical heterogeneity of supermicro-porous active carbons should be accounted in the attempts to found the real state properties of fluids confined in supermicropores. 

Separation of mixtures of condensable and non-condensable components. If a fluid mixture contains both condensable and noncondensable components, then a partial condensation followed by a simple phase separator often can give a food separation. This is essentially a single-stage distillation operation. It is a special case that deserves attention in some detail later. 

In the first class, azeotropic distillation, the extraneous mass-separating agent is relatively volatile and is known as an entrainer. This entrainer forms either a low-boiling binary azeotrope with one of the keys or, more often, a ternary azeotrope containing both keys. The latter kind of operation is feasible only if condensation of the overhead vapor results in two liquid phases, one of which contains the bulk of one of the key components and the other contains the bulk of the entrainer. A t3q)ical scheme is shown in Fig. 3.10. The mixture (A -I- B) is fed to the column, and relatively pure A is taken from the column bottoms. A ternary azeotrope distilled overhead is condensed and separated into two liquid layers in the decanter. One layer contains a mixture of A -I- entrainer which is returned as reflux. The other layer contains relatively pure B. If the B layer contains a significant amount of entrainer, then this layer may need to be fed to an additional column to separate and recycle the entrainer and produce pure B. 

Consider again the simple process shown in Fig. 4.4d in which FEED is reacted to PRODUCT. If the process usbs a distillation column as separator, there is a tradeofi" between refiux ratio and the number of plates if the feed and products to the distillation column are fixed, as discussed in Chap. 3 (Fig. 3.7). This, of course, assumes that the reboiler and/or condenser are not heat integrated. If the reboiler and/or condenser are heat integrated, the, tradeoff is quite different from that shown in Fig. 3.7, but we shall return to this point later in Chap. 14. The important thing to note for now is that if the reboiler and condenser are using external utilities, then the tradeoff between reflux ratio and the number of plates does not affect other operations in the flowsheet. It is a local tradeoff. 

Z. Evaporation. If the wastewater is in low volume and the waste material involatile, then evaporation can be used to concentrate the waste. The relatively pure evaporated water might still require biological treatment after condensation. The concentrated waste can then be recycled or sent for further treatment or disposal. The cost of such operations can be prohibitively expensive unless the heat available in the evaporated water can be recovered. 

Multi-necked flasks. Fig. II, 1, 8, a, illustrates a typical threenecked flask. This has numerous applications in organic chemistry for many operations, the central aperture carries a mechanical stirrer, and the two side apertures a dropping funnel and a reflux condenser respectively. 

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