. The manufacture of pulp and paper : a textbook of modern pulp and paper mill practice. affle wallby the holes W, and leaveby outlet F. K and L arecleanouts. 27. Effect of Tempera-ture.—The temperature of thegas as it leaves the combus-tion chamber and enters thecast-iron pipe that connectsit with the coolers is usuallyfrom 700° to 900°C. It is im-portant to keep the tempera-ture at this point, in order toavoid the formation of anylarge amount of sulphur triox-ide gas S03, which is alwaysformed to some extent in thesulphur burning process. Itis important to keep the S03content of the gas as l
. The manufacture of pulp and paper : a textbook of modern pulp and paper mill practice. affle wallby the holes W, and leaveby outlet F. K and L arecleanouts. 27. Effect of Tempera-ture.—The temperature of thegas as it leaves the combus-tion chamber and enters thecast-iron pipe that connectsit with the coolers is usuallyfrom 700° to 900°C. It is im-portant to keep the tempera-ture at this point, in order toavoid the formation of anylarge amount of sulphur triox-ide gas S03, which is alwaysformed to some extent in thesulphur burning process. Itis important to keep the S03content of the gas as low aspossible, since it combineswith the calcium in the ab-sorption system, forming cal-cium sulphate CaS04, whichis an insoluble salt, and whichrepresents a direct loss ofsulphur. The presence of sul-phuric acid in the digester isalso detrimental to the fiberin the cooking process. The formation of sulphurtrioxide S03 according to theequation S« >, + 0 = S03 ads in the first place upon the temperature. It is foundthat between 400° and 600°C, the maximum of S03 is produced;. Fig. §4 PREPARATION OF THE COOKING ACID 17 while at temperatures below 200°C. and around 900 to 1000°C,practically no S03 is formed. It is therefore important to avoidthe critical temperatures as much as possible; or, in other words,to keep the temperature in the combustion chamber high, and tocool the gases after leaving this chamber as quickly as 28. Importance of Regulating Air Supply.—The rapidity withwhich the sulphur dioxide is oxidized to trioxide is also increasedin the presence of much oxygen, and a large excess of air shouldtherefore be carefully avoided. The correct amount of air required per pound of sulphur inorder to produce a gas of a certain strength can easily be calcu-lated. In the following example, a strength of the burner gasof 16% is assumed, and it is assumed that there is nosublimation and no S03 formation. According to the formula, s+o2 = so2 32 32 64One mo
Size: 983px × 2543px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1920, booksubjectpaperma, bookyear1921
