Bookbinding and the Conservation of Books
A Dictionary of Descriptive Terminology

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digester

A vessel in which pulpwood, straw, esparto, rags, or other cellulosic materials are treated with chemicals and heat to produce the pulp used in the manufacture of paper. A digester is usually constructed to withstand elevated pressures and is made of materials designed to resist the chemicals used in pulp preparation. Digesters may be cylindrical, spherical, horizontal, vertical, stationary, rotating or designed to tumble. Most are stationary. A digester may be designed for batch operation, in which it discharges its pu lp at the conclusion of a fixed cycle, or it may be designed for continuous operation, in which case it moves the raw material and chemicals at a fixed rate from the charging end to the discharging end. (17 )




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