Chemistry of pulp and paper making . ause the rags arenot in motion and hence there is no rubbing off of the weakerfibres. On the other hand, they require more steam, are notsuitable for use with lime cooks and take longer to discharge,since the cooked rags must all be removed by hand throughmanholes. Stationary boilers are largely used in Great Britainbut seldom on the Continent or in this country. Of the rotary boilers the cylindrical is more generally em-ployed than the spherical, though the shape of the latter greatlyassists in discharging its contents. The boilers are charged GriflSn and
Chemistry of pulp and paper making . ause the rags arenot in motion and hence there is no rubbing off of the weakerfibres. On the other hand, they require more steam, are notsuitable for use with lime cooks and take longer to discharge,since the cooked rags must all be removed by hand throughmanholes. Stationary boilers are largely used in Great Britainbut seldom on the Continent or in this country. Of the rotary boilers the cylindrical is more generally em-ployed than the spherical, though the shape of the latter greatlyassists in discharging its contents. The boilers are charged GriflSn and Little: Chemistry of Paper Making, p. 152. 74 RAGS, ESPARTO, STRAW, BAMBOO through manholes and with large boilers the men frequentlyenter them in order to pack the rags properly. The steamenters the boiler through the trunions and passes through grat-ings on the inside into the stock. The rotaries are also fittedwith strainers through which much dirt passes in blowing offpressure. The rotaries usually turn at a speed of one revolu-. Fig. 5. Spherical Rag Boiler tion in two to five minutes. The consequent agitation andfriction of the rags cause the detachment of the lime compoundsformed and allow the action to continue on the remaining fattymaterials. When the cook is completed the liquor and steamare blown off through the strainers and blow-off cocks, themanhole covers are removed and the contents are dischargedby allowing the boiler to revolve. Even a large cylindricalboiler will empty itself clean in this way. With competentlabor the operations on a cylindrical boiler holding a charge of5000 to 5200 lbs. of rags occupy the following times: Hours Charging rags i J Blowing off liquor 2 Discharging rags 3 During the cooking of rags a small amount of ammonia isgiven off. Tests on a large scale showed that the followingamounts were discharged. TREATMENT OF RAGS 75 o. 22 per cent ammonia (NH3) from Japanese blues,o. OS per cent ammonia (NH3) from second white stocko. 14 per cent a
Size: 1878px × 1331px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1920, booksubjectpaperma, bookyear1920
