Pulp stock preparation

The first operation in the paper mill involves stock preparation the slushing of baled pulp, the refining or beating of chemical pulps, the blending of pulp stocks and additives prior to forming paper. 

Yang L, et al (2004) Revised Kubelka-Munk Theory. II. Unified framework for homogeneous and inhomogeneous optical media. Journal Opt. Soc. Am. A 21(10) 1942 McLain L, Wygant R (2005) Fundamental Filler Characteristics for Maximum Sheet Performance, Paper presented at AEL Metsko s Stock Preparation and Uses of Various Pulps Workshop, Munich, Germany, November 2005... 

The paper-making process consists of various steps from pulp production, pulp processing and chemical recovery, pulp bleaching, and stock preparation to paper manufacturing. 

Pulping (mechanical, chemical, semi-chemical, and deinking) Pulp Washing and Screening Stock Preparation Papermaking... 

All these components have to be adequately prepared for optimum use in the papermaking process steps. The additives may be delivered ready for use or may have to be finally prepared according to the requirements in the mill. Fiber stock preparation includes several unit operations depending on the furnish and the purpose. Stock preparation of virgin fiber pulp needs less machinery and energy than the preparation of recovered paper which, however, is the cheaper raw material. Fiber stock preparation ends at the paper machine chest. Here stock of high consistency is preferred to minimize carry-over of chemicals and contaminants. 

The objective of fiber stock preparation systems is to modify the different ingoing raw materials in such a way that the finished stock finally supplied to the paper machine suits the requirements of the paper machine and of the quality demands put on the produced paper or board. The raw stocks used are the various types of virgin pulps as well as recovered paper grades. They are available in the form of bales, loose material or, in the case of integrated mills, as suspensions. The finished stock is a suspension of defined quality as far as the mixture and characteristics of the fibers, additives, and impurities are concerned. This quality essentially determines paper machine runnability and is the basis for the final paper and board quality. 

The purpose of repulping or slushing is to break down the dried primary fiber pulp or recovered paper into individual fibers or, at least, to form a suspension which can be pumped. In the latter case the remaining flakes have to be broken down in subsequent deflaking machinery. Repulping is needed not only at the beginning of the stock preparation system but also for the wet or dry broke from the paper machine. 

Refining is very important in the stock preparation process for virgin chemical pulp. For mechanical and recycled fibers refining has lower importance. The refining of recycled fibers usually aims for strength increase and shive elimination or reduction. 

J. Toland, Around the world of stock preparation, Pulp Paper Int. 2003, 45 (4) www.paperloop.com/db-area/archive/ ppi-mag/2003/0304/ppi3.html... 

One or two (in special cases, such as market DIP (deinked pulp) production, sometimes even three) water loops in the stock preparation. 

The agitation of pulp stock for homogenization and blending is the most common mixing operation in pulp and paper manufacture. The blend chest (a well-mixed stirred vessel) illustrates the importance of macroscale mixing in pulp and paper processes. It is the heart of the stock preparation system and is used to mix two or more pulp streams, often with wet-end chemicals, dyes, fillers or additives, as well as providing a uniform feed of stock to the paper machine. Mixing chests... 

Stock preparation in a paper mill includes all intermediate operations between preparation of the pulp and the final papermaking process. It can be subdivided into (1) preparation of the furnish and (2) beating or refining. Furnish is the name for the water slurry of... 

Pulp and Paper Chemical and coatings preparation Stock dilution and consistency control Addition of bleaching chemicals... 

Wood, and the fiber obtained from it, is a complex arrangements of polymers and macromolecules that are exceedingly difficult to analyze chemically. But it is shown in Figure 1 that wet processes produce two streams, pulp from cooked fiber for board production and a liquor containing water solubles extracted from the stock. The liquor is easier to analyze and its composition may afford insight into the chemical changes effected by furnish preparation. 

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