File:The manufacture of pulp and paper - a textbook of modern pulp and paper mill practice (1921) (14784880305).jpg

Identifier: manufactureofpul03join (find matches)
Title: The manufacture of pulp and paper : a textbook of modern pulp and paper mill practice
Year: 1921 (1920s)
Authors: Joint Textbook Committee of the Paper Industry Stephenson, J. Newell
Subjects: Papermaking Wood-pulp
Publisher: New York : McGraw-Hill Book Company
Contributing Library: NCSU Libraries
Digitizing Sponsor: NCSU Libraries

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nace. The ore is fed automatically to thetop chamber from a hopper K on the top of the furnace, and isdistributed on the hearth. The rabbles (teeth) of one of thearms are set at such an angle that the ore is moved toward thecenter, while the position of the rabbles on the second armcauses the ore to turn over, whereby a large surface of the oreis exposed to the air. Arriving at the center of the top chamber,the ore drops through an opening into the chamber below, inwhich the rabbles slowly work the ore towards the outer edgeof the hearth, where it drops into the chamber underneath; onthe next, it is worked to the center, and so on, until the orefinally has passed through all chambers, and is discharged ascinder to the bottom shelf or chamber. The air is admittedthrough openings around the bottom hearth, and passes through §4 PREPARATION OF THE COOKING ACID 13 all the chambers in the direction opposite to that of the ore.The quantity of air is so regulated as to secure the proper com-
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Fig. 4. bustion of the sulphur, so that the gas leaving the furnace fromthe top chamber at H carries the desired quantity of sulphurdioxide. The hollow central shaft and also the arms are cooled 14 MANUFACTURE OF SULPHITE PULP §4 with air. The small-size furnaces, of about 11 feet diameter,require 1 to 2 horsepower and will roast from 3 to 4 tons of pyritesin 24 hours. The larger size furnace, 16 feet in diameter, willroast about 9 tons in 24 hours. In the modern type of furnace,the individual rabbles can be replaced, and the cooling air to theshaft and arms can be regulated, so as to permit an effectivecontrol of the temperature within the furnace. 22. Wedge Furnace.—The Wedge furnace is very similar tothe HerreshofT furnace in construction, but possesses certaincharacteristic features. The central shaft, which makes about 1revolution in 4 minutes, has a diameter of o feet and is open attop and bottom, allowing air to circulate. It is sufficientlylarge and cool for a man to enter

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