Pulping processes chemithermomechanical

Certain chemical treatments can be employed during the TMP process to achieve improved strength. Sodium sulfite and hydrogen peroxide have been used either for chip pre- or post-treatment of the TMP pulp such pulp is called chemithermomechanical pulp (CTMP). The strength improvements, which may be 50%, are obtained at some sacrifice to yield and opacity. The yields of mechanical pulps are 90—95% the lower yields are associated with chemical treatment. No principal commercial pulps are produced in the next lower yield range, ie, 80—90%. 

Aspen Wood Treated with Chemical-Thermomechanical Process. Aspen wood was pulverized into "chemithermomechanical pulp (CTMP) by a chemical-thermomechanical process 24), During this process, very little hemicellulose and lignin are removed. The CTMP was used without any... 

Sodium sulfite (Na2S03) is produced by reacting sulfur dioxide with a solution of sodium carbonate or sodium hydroxide. Sodium sulfite is also recovered as a byproduct of resorcinol production. About half of the sodium sulfite produced in North America is used by the pulp and paper industry (i.e., chemithermomechanical process). It is also used in photography, textile bleaching, and food preservation, and as a chemical intermediate. Some producers can switch from sodium sulfite to sodium bisulfite or metabisulfite in the same facility. In 1998, the market demand for sodium sulfite was 102,000 tons in the United States, excluding that produced and used captively by some paper mills. The demand has decreased substantially over the recent years as pulp mills have reduced sulfur discharges. 

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