. The manufacture of pulp and paper : a textbook of modern pulp and paper mill practice. is absorbed in this tower, which is called thestrong tower. The unabsorbed gas leaving the top of this toweris conducted through a tile pipe J to the bottom of the secondtower, now the weak-acid tower, which in construction isidentical with the first tower. Water is sprayed from the top ofthe weak-acid tower, absorbing on its way the weak SO2 gas,forming sulphurous acid H2S03, which acts upon the limestoneand forms a weak solution of bisulphite; this is pumped fromthe bottom of this tower to the top of the
. The manufacture of pulp and paper : a textbook of modern pulp and paper mill practice. is absorbed in this tower, which is called thestrong tower. The unabsorbed gas leaving the top of this toweris conducted through a tile pipe J to the bottom of the secondtower, now the weak-acid tower, which in construction isidentical with the first tower. Water is sprayed from the top ofthe weak-acid tower, absorbing on its way the weak SO2 gas,forming sulphurous acid H2S03, which acts upon the limestoneand forms a weak solution of bisulphite; this is pumped fromthe bottom of this tower to the top of the strong-acid towerthrough pipe P, and is distributed by plate Q. The operationof the towers is made reversible by means of cocks and gas seals/; in which case, the weak-acid tower becomes the strong-acidtower, and vice versa. On account of the good absorption of 32 MANUFACTURE OF SULPHITE PULP |4 the gas in the strong tower, the gas entering the second tower isso weak that this tower can be charged with limestone duringthe operation. The gas fan E is directly connected to a variable. tea Fig. 13. speed motor F, allowing a variation in the volume of gas and,thereby, a variation of the capacity of the system. Before thetower acid from the strong tower is pumped to the recoverytower, which will be described later, it passes through a settling §4 PREPARATION OF THE COOKING ACID 33 tank L, in which any sand and other impurities are settled are provided at S and T. 52. The total SO2 of the acid leaving the strong tower may beregulated to any desired strength by adjusting the gas and thewater. The combined S02, by which is meant the S02 combinedwith the calcium (and magnesium), may be regulated by chang-ing the temperature of the water, since the reaction on the stoneis more rapid at higher temperature. The temperature of thewater used in acid making is a very important factor in theproduction of uniform acid. Due to the high temperature ofthe water in some localities i
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectpaperma, bookyear1921
