Ammonium-based spent sulfite liquor

Shen, K. C. Calve, L. Ammonium-Based Spent Sulfite Liquor for Waferboard Binder. Reprinted Adhesive Age, August 1980. 

Ammonia and ammonium persulfate can also be used as reagents (21). However, as pointed out by Nimz (48) and other authors, owing to the non-uniformity of the product, only 15% of urea-formaldehyde and 25% phenol-formaldehyde resin binder may be replaced by calcium base spent sulfite liquors. 

Substitution of potassium ferricyanide for 1% of sulfur dioxide dissolved in calcium-base spent sulfite liquor was possible at a pH of about 2.0. An increase in pH stabilized the cross-linking mixture unless 4% of ammonium chloride (dry wood basis) was added. In this case particle board could be produced at a pH of 4.5, with properties equivalent to those produced at a pH of 2.0, i.e., with IB values of up to 82.0 psi and acceptable water resistance (JOS, 109). 

Ammonium-based sulfite spent liquors can be burned in the same type of furnace as the calcium-based liquors. However, during combustion the base is decomposed to form nitrogen and water and the problems with fly ash are thus eliminated. All sulfur escapes to the combustion gases as sulfur dioxide which can be partly absorbed in an ammonia solution. 

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