. Applied thermodynamics for engineers. 290 shows a^ triple-effect or three-stage evaporator; steam (preferably exhauststeam) enters the shell of the first stage. The liquor to be evaporatedenters the tubes of this stage, becomes partly vaporized, aud the separatedvapor and liquid pass off as just described. From the outlet c. Fig. 291,the vapors pass through an ordinary separator, which removes any ad-ditional entrained liquid, discharging it back to b, and then proceed tothe shell of the second stage. Meanwhile the liquid from the chamber hof the first stage has been pumped, through a hydros
. Applied thermodynamics for engineers. 290 shows a^ triple-effect or three-stage evaporator; steam (preferably exhauststeam) enters the shell of the first stage. The liquor to be evaporatedenters the tubes of this stage, becomes partly vaporized, aud the separatedvapor and liquid pass off as just described. From the outlet c. Fig. 291,the vapors pass through an ordinary separator, which removes any ad-ditional entrained liquid, discharging it back to b, and then proceed tothe shell of the second stage. Meanwhile the liquid from the chamber hof the first stage has been pumped, through a hydrostatic tube whichpermits of a difference in pressure in two successive sets of tubes, into thetubes of the second stage. As many as six successive stages may beused;* the vapors from the last being draw^n off by a condenser andvacuum pump. The hquid from the chamber 6 of the last stage is atmaximum density. 596. Condition of Operation. The vapor condensed in the variousshells is ordinarily water, which in concentrating operations may be. Fig. 291. Art. 595. — Yaryan Evaporator. * The number of effects that can be used is limited by the difference in tempera-ture of steam supplied and final condensate discharged. MULTIPLE-EFFECT EVAPORATION 443 drawn off and wasted, or, if the temperature is sufficiently high,employed in the power plant. The condenser is in communicationwith the last tubes, and, through them, with all of the shells and tubesexcepting the first shell; but between the various stages we have theheads of fiquid in the chambers b, which permit of carrying differentpressures in the different stages. A gradually decreasing pressureand temperature are employed, from first to last stage; it is this whichpermits of the further boihng of a liquid already partly evaporated in aformer effect. The pressure in the tubes of any stage is always lessthan that in the surrounding shell; the pressure in the shell of anystage is equal to that in the tubes of the previous stage. 597.
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