. The manufacture of pulp and paper : a textbook of modern pulp and paper mill practice. ter D. Instead, the steam is led to a heater A outside ofthe digester; and the circulating liquor from the pump passes THE COOKING PROCESS IN A SODA MILL 33 through this heater, which is so designed that the steam is onone side of and the liquor is on the other side of a series of tubesC. The condensed steam is fed back to the boilers or wash-water tanks by the condensatepump G, instead of going intothe digester; thus the liquorthat returns to the digesteris not weakened by the addi-tion of condensed steam
. The manufacture of pulp and paper : a textbook of modern pulp and paper mill practice. ter D. Instead, the steam is led to a heater A outside ofthe digester; and the circulating liquor from the pump passes THE COOKING PROCESS IN A SODA MILL 33 through this heater, which is so designed that the steam is onone side of and the liquor is on the other side of a series of tubesC. The condensed steam is fed back to the boilers or wash-water tanks by the condensatepump G, instead of going intothe digester; thus the liquorthat returns to the digesteris not weakened by the addi-tion of condensed steam. 45. Preventing Waste ofHeat from the Digester.—Welded digesters can easily becovered with material thatwill reduce the loss of heat byradiation; asbestos felt, mag-nesia coverings, or a combina-tion of these may be many cases, this heat-sav-ing substance is put on witha trowel, and is held in placeby coarse-mesh wire fabric,hung from a metal ring aroundthe top of the digester. Muchheat is saved in this way andless condensation is found inthe digester, to dilute DIGESTER-HOUSEDETAILS 46. Blow Pits.—The blowpit, or blow tank, is a vessellarge enough to hold easilythe contents of a digester, anda line of blow-piping connectsone or more digesters to pits are generally placed at a considerable elevation abovethe washing tanks, in order that the pulp, or stock, may betaken down into the tanks by gravity. The blow pit separates the steam, which is set free when the Fia. 10. 34 MANUFACTURE OF SODA PULP §5 digester is blown, from the stock and liquor. This is a very important function, sincemore than 2000 cu. ft.(about 85 lb.) of steamescapes into the air foreach cord of wood in thedigester charge. The roofs of some millbuildings in the vicinity ofthe digester house oftenpresent a very unsightly ap-pearance, due to the blackpulp that was thrown outof the vomit pipe abovethe blow pit with the steam,and which rained down onthem. The clothes of pas-sers-b
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