Sulfite cooking

Uses Manufacture of acrylonitrile, hydrazine hydrate, hydrogen cyanide, nitric acid, sodium carbonate, urethane, explosives, synthetic fibers, fertilizers refrigerant condensation catalyst dyeing neutralizing agent synthetic fibers latex preservative fuel cells, rocket fuel nitrocellulose nitroparaffins ethylenediamine, melamine sulfite cooking liquors developing diazo films yeast nutrient. 

Semichemical pulp of bagasse prepared by the acid sulfite cooking was obtained from Edfuo Company of Egypt. 

A good impregnation is a prerequisite for a satisfactory cook. If the transport of chemicals into the chips is still incomplete after the cooking temperature has been reached, undesirable reactions catalyzed by hydrogen ions will occur. For instance, if the base concentration in an acid sulfite cook is... 

Fig. 7-5. Influence of cooking acid composition on lignin condensation in acid sulfite cooking of spruce (130°C) (Kaufmann, 1951).

During sulfite pulping the fatty acid esters are saponified to an extent determined by the conditions. Some of the resin components can also become sulfonated, resulting in increased hydrophilicity and better solubility. However, the partial removal of resin that always occurs during sulfite cooking and subsequent mechanical treatment is mainly associated with the formation of finely dispersed resin particles in stable emulsions. The dissolved lignosulfonic acids act as detergents with respect to the lipophilic resin components. 

Fig. 7-19. Recovery and conversion cycles for sulfite cooking chemicals.

Goliath, M., and Lindgren, B. O. (1961). Reactions of thiosulphate during sulfite cooking. Part 2. Mechanism of thiosulphate sulphidation of vanillyl alcohol. Sven. Papperstidn. 64, 469-471. 

Hardwood cooking liquors as well as the resulting evaporation condensates from acid liquors contain appreciable quantities of acetic acid. Because the solutions are very dilute, an economic recovery of the acetic acid is difficult but highly desirable to avoid pollution from discharges. Acetic acid can be recovered from neutral sulfite cooking liquors by extraction of the acidified liquor with organic solvents followed by distillation. Formic acid present in small quantities must be removed by azeotropic distillation if a pure product is required. 

Ammonia is found in the environment as the result of natural and industrial processes. It is released into the environment by the breakdown of organic wastes, and it is a constituent of the soil, the atmosphere, and bodies of water. Ammonia is also a key intermediate in the nitrogen cycle and is a product of amino acid metabolism (WHO 1986). Anhydrous ammonia is used in the production of nitric acid, explosives, synthetic fibers, and fertilizers (Budavari 1989). It is used as a refrigerant as a corrosion inhibitor in the purification of water supplies in steel production as a catalyst for polymers as a preservative for latex and in the production of nitrocellulose, urea formaldehyde, sulfite cooking liquors, and nitroparaffins (ACGIH 1991 Lewis 1993). Ammonium hydroxide (10-35% ammonia) is a major constituent of many cleaning solutions. Ammonia... 

Kleinert TN, Joyce CS (1957b) Short wavelength absorption of various lignins and related substances III The flow-micro cuvette for continuous measurement of lignin concentration in sulfite cooking liquors Pulp Pap Mag Can 58(7) 215-219 Kolboe S, Ellefsen O (1962) Infrared investigations of lignin A discussion of some recent results Tappi 45 163-166... 

The acetyl groups in hardwood xylans have been found to exhibit a remarkable stability under the relatively drastic conditions of acid sulfite cooking [258]. In steam treatments of birch wood, the acetyl group was more stable than the 4-0-methyl glucuronosyl unit [259]. 

Similarly, the a-D-( 1-6)-galactosidic linkage present in galactoglucoman-nans is very labile under acidic conditions [262]. Its high reactivity, however, cannot be satisfactorily explained in terms of the behavior of simple glycosides (Table 2). Alkali-induced deacetylation of glucomannan increased its resistance toward acid hydrolysis as evidenced in acid sulfite cooking [263,264]. 

On the other hand, certain types of wood pulp, prepared by se((uences involving both acidic and alkaline treatments, show a linear relationship between gamma-cellulose and non-cellulosic polyoses. This may be illus-strated from the studies of White, Steinman and Work on acetylation pulps. Acetylation-grade pulps are usually prepared from softwoods by sulfite cooking followed by hot-caustic refining. When the total polyose content of a number of such pulps was compared with their gamma-cellulose content, a linear relationship was obtained (see Fig. 3). In spite of this excellent correlation, it cannot be assumed that all of the non-cellulosic polyoses are contained in the gamma fraction of these pulps (see below). 

The ease with which cellulose and glucomannan tend to associate is also evident from investigations on the acid sulfite cooking of wood. If such a... 

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