Condensation systems

It should be noted that, whatever the fonu of Henry s law (i.e. in whatever composition units), Raoult s law must necessarily be expressed in mole fraction. This says nothing about the appropriateness of mole fractions in condensed systems, e.g. in equilibrium expressions it arises simply from the fact that it is a statement about... 

Rabinowitch E 1937 Collision, coordination, diffusion and reaction velocity in condensed systems Trans. Faraday See. 33 1225-33... 

Mark E. Tuckerman, Glenn J. Martyna, and Bruce J. Berne. Molecular dynamics algorithm for condensed systems with multiple time scales. J. Chem. Phys., 93(2) 1287-1291, Jul. 1990. 

Tuckerman, M., Martyna, G. J., Berne, J. Molecular Dynamics Algorithm for Condensed Systems with Multiple Time Scales. J. Chem. Phys. 93 (1990) 1287-1291... 

The heterocycioammonium salts can be made of 5- or 6-membered rings or even be (5-1-6) or (6-t-6 l condensed systems,. kmong the cyanines... 

The reaction of methoxy-substituted 1,4-dihydroatomatic systems is a general one. Other condensed systems react ia a similar manner, for example, 3,6-dimethoxy-1,4,S,8-tetrahydronaphtha1ene and derivatives of anthracene (35) and xanthene (36) (74). The proposed method enables synthesis of the tri-and tetracarbocyanines where the whole chromophore is iategrated iato a rigidizing skeleton. Asymmetrical polymethines can also be obtained similarly. 

The commercial production equipment consists of a furnace, heat-exchanger tubes, a fractionating column packed with Rachig rings, a KCl feed, a waste removal system, and a vapor condensing system (Fig. 1). 

Fossil Fuel-Fired Plants. In modem, fossil fuel-fired power plants, the Rankine cycle typically operates as a closed loop. In describing the steam—water cycle of a modem Rankine cycle plant, it is easiest to start with the condensate system (see Fig. 1). Condensate is the water that remains after the steam employed by the plant s steam turbines exhausts into the plant s condenser, where it is collected for reuse in the cycle. Many modem power plants employ a series of heat exchangers to boost efficiency. As a first step, the condensate is heated in a series of heat exchangers, usually sheU-and-tube heat exchangers, by steam extracted from strategic locations on the plant s steam turbines (see HeaT-EXCHANGETECHNOLOGy). 

Intermediate Condenser. As shown in Figure 3, an intermediate condenser forces the operating line closer to the equiUbrium line, thus reducing the inherent inefficiencies in the tower. Using intermediate condensers and reboilers, it is possible to raise the efficiency above that for a simple reboder—condenser system, particularly when the feed composition is far from 50 50 in a binary mixture. 

Alkalinity Reduction. Treatment by lime precipitation reduces alkalinity. However, if the raw water alkalinity exceeds the total hardness, sodium bicarbonate alkalinity is present. In such cases, it is usually necessary to reduce treated water alkalinity in order to reduce condensate system corrosion or permit increased cycles of concentration. 

Condensate Polishing. Ion exchange can be used to purify or poHsh returned condensate, removing corrosion products that could cause harmful deposits in boilers. Typically, the contaminants in the condensate system are particulate iron and copper. Low levels of other contaminants may enter the system through condenser and pump seal leaks or carryover of boiler water into the steam. Condensate poHshers filter out the particulates and remove soluble contaminants by ion exchange. 

Condensate systems can be chemically treated to reduce metal corrosion. Treatment chemicals include neutralising amines, filming amines, and oxygen scavenger-metal passivators. 

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). 

The use of neutralising amines in conjunction with an oxygen scavenger—metal passivator improves corrosion control in two ways. First, because any acidic species present is neutralized and pH is increased, the condensate becomes less corrosive. Second, most oxygen scavenger—passivators react more rapidly at the mildly alkaline conditions maintained by the amine than at lower pH levels. For these reasons, this combination treatment is gaining wide acceptance, particularly for the treatment of condensate systems that are contaminated by oxygen. 

J. Kleia, Molecular Conformation and Dynamics of Macromolecules in Condensed Systems, Elsevier, Amsterdam, 1988, p. 333. 

For partial condenser systems, the pressure can be controlled by manipulating vapor product or a noncondensible vent stream. This gives excellent pressure control. To have a constant top vapor product composition, the condenser outlet temperature also needs to be controlled. For a total condenser system, a butterfly valve in the column overhead vapor line to the condenser has been used. Varying the condenser cooling by various means such as manipulation of coolant flow is also common. 

The required orifice continuous flow capacity is determined at steam chest pressure to condensate system pressure at a flow 6 to 8 times design. If designed for normal flow the trap would have to be open 100% of the time. Then, as stated above, a body size is selected that can contain the required orifice (not be above the stated... 

How to Design Overhead Condensing Systems, Chem. Eng., Series beginning August 15, 1977. Lieberman, N. P, Troubleshooting Refinery Processes, Pennwell, 1981. 

A typical condensation system involves the reaction of a silanol-terminated polydimethylsiloxane with a multi-functional organosilicon cross-linking agent such as Si(RO)4 Figure 29.8). Pot life will vary from a few minutes to several hours, depending on the catalysts used and the ambient conditions. Typical catalysts include tin octoate and dibutyl tin dilaurate. 

Although waterborne systems were developed in the 1960s, the form of this chemistry that dominates the industry utilizes end-functional, high molecular weight base polymers dissolved in organic solvents. Work on solventless condensation systems continues, but has not yet become commonplace [45,47]. Solvent-borne condensation cure systems are convenient for their ease of pro-... 

A WBL can also be formed within the silicone phase but near the surface and caused by insufficiently crosslinked adhesive. This may result from an interference of the cure chemistry by species on the surface of substrate. An example where incompatibility between the substrate and the cure system can exist is the moisture cure condensation system. Acetic acid is released during the cure, and for substrates like concrete, the acid may form water-soluble salts at the interface. These salts create a weak boundary layer that will induce failure on exposure to rain. The CDT of polyolefins illustrates the direct effect of surface pretreatment and subsequent formation of a WBL by degradation of the polymer surface [72,73]. 

Short regeneration tune requires a higher steaming rate, thus increasing the heat duty of the condenser system. 

In some cases where condensing loads are high, or where it is required to recover condensed liquid blowdown material for pollution, toxicity or economic reasons, an unsteady state condensing system may be appropriate. Examples or such applications are as rollows ... 

Given a VOC-laden gaseous stream whose flowrate is G, supply compositimi of the VOC is y and supply temperature is T , it is desired to design a cost-effective condensation system which can recover a certain fraction, a, of the amount of the VOC contained in the stream. 

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