. The manufacture of pulp and paper : a textbook of modern pulp and paper mill practice. he general efficiency of the condenser andthe cost of maintaining a good vacuum will ordinarily limit thetemperature in the last effect to about 125°F. If a triple-effectevaporator is used, the vapor temperatures for effects 1, 2, and 3will therefore be about 225°, 175°, and 125°, respectively. Sincesteam is used only in No. 1 and condenser water only in No. 3,the increase in efficiency over using three single-effect evaporatorsis obvious. This subject is discussed more fully in the Sectionon Sulphate Pulp
. The manufacture of pulp and paper : a textbook of modern pulp and paper mill practice. he general efficiency of the condenser andthe cost of maintaining a good vacuum will ordinarily limit thetemperature in the last effect to about 125°F. If a triple-effectevaporator is used, the vapor temperatures for effects 1, 2, and 3will therefore be about 225°, 175°, and 125°, respectively. Sincesteam is used only in No. 1 and condenser water only in No. 3,the increase in efficiency over using three single-effect evaporatorsis obvious. This subject is discussed more fully in the Sectionon Sulphate Pulp. §5 WASHING PULP AND RECLAIMING CHEMICALS 55 There are several makes of evaporators that have horizontaltubes, which are submerged in the liquid, and in which the steamcondenses. 96. Film Evaporators.—The evaporator shown in Fig. 17 iscommonly built in either three or four effects. Each effect hasa feed head B and a discharge head C at the ends of a series oftubes. These heads are divided into a number of sections insuch a manner that the tubes D form a series of manifolds or. Fig. 17. coils. The black liquor is fed into the first tube of a coil througha hole in the feed head B, and it escapes from the last tube of thecoil through the discharge head C. The heating steam is confinedin the shell E; it is introduced at F, and the condensate is with-drawn at G. Live steam is used in the first effect, the secondeffect is heated by vapors from the first, and so on. The con-densation of the vapor here reduces the pressure on the liquidin the preceding effect, causing it to boil at a lower temperature,and therefore requiring less heat to evaporate it. The boilingof the liquor causes a great increase in volume, and this causes arush of foamy liquor, which spreads a film of liquid on the sidesof the tubes. For low pressures of steam (vapor), the temperature variesgreatly for slight changes in pressure. Thus, the boiling pointof water (temperature of steam) at 20 lb. per sq. in. p
Size: 2136px × 1170px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1920, booksubjectpaperma, bookyear1921
