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Unformatted text preview: Washing Lecture 9 PAPR 1000 Introduction to Pulp and Paper Manufacturer 1 Chemical vs. Mechanical Pulping Chemical Yield Cellulose Purity End uses Raw material sensitivity Low (~45%) High (Lignin removed) Dissolved pulp, high quality paper Low Mechanical High (>90%) Low (Lignin remains) Low quality, High volume paper High 2 Chemical vs. Mechanical Pulping Quality Parameters Chemical Strength Bulk Optical Drainability High (fibers intact) Low (more flexible fibers) Dark but bleachable Good (long fibers, few fines) Mechanical Low (fibers damages) High (less flexible fibers) Bright but hard to bleach Poor (short fibers, many fines) 3 Pulping Mechanical Hybrid Chemical SGW RMP & TMP Kraft or Sulfate Sulfite 4 Digester - Cooking Blow Tank Flash Steam / Foul Smelling Bleaching Knotter Screen Washing -BSW Stock Preparation 5 Blow Tank Large cylindrical vessel Hot pulp from digester is mixed with agitators with diluted black liquor Hot gases from BT are recovered by the blow heat accumulator (heat exchanger) Condensat...
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This note was uploaded on 04/02/2008 for the course PAPR 1000 taught by Professor Joyce during the Fall '08 term at Western Michigan.

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