Bisulfite pulping

Wood Pulping. The system Mg(OH)2 S02 H20 is also used in acid bisulfite pulping. Compared to a calcium-based system which is not as amenable to regeneration of the pulping bisulfite (87), fewer technical problems are encountered in the digesters, evaporators, or recovery boiler of the Mg-based process. In the presence of excess SO2, bisulfite forms in a 43% MgSO solution, at 25°C and 101.3 kPa (1 atm) SO2 pressure, to increase MgSO solubihty. 

It is claimed that magnesium bisulfite pulping would provide more efficient operation with the possibility of higher yields. 

Lignosite Lignosulfonate products are derived from the lignin in softwood trees by the calcium bisulfite pulping process at GeorgiarPacific s mill in Bellingham, Washington. 

Catechol B displays weak discolouration under our experimental conditions (Figure 2) as already observed for this compound when it was adsorbed on bleached chemical bisulfite pulp [4]. The low absorption above 300 nm is presumably the cause of this low reactivity. 

The same authors (5) showed also in another work that the presence of larger amounts of lignin in bisulfite pulps may have a favourable effect on grafting polyacrylonitrile using the cellulose xanthate-hydrogen peroxide redox system to initiate the copolymerization reaction. The plots of the total conversion as well as of polymer loading show a minimum centered around approximately 15% of lignin. 

Pulp the high yield bisulfite pulp of aspen, yield 93%, brightness 46.6%, C.S.F. 325, lignin 14.8%. 

The pulps prepared by this procedure as well as the non bleached high yield bisulfite pulp have been characterized by the standard methods of the Canadian Pulp and Paper Association (CPPA Technical Section) as shown in Table I,... 

It has been shown that the xanthate method could be successfully applied in order to graft hardwood high yield bisulfite pulp made of aspen. The optimum grafting condition, which would give almost 100% grafting efficiency (i.e.,100% formation of true graft and no homopolymer) and rather high monomer conversion of 80% are as follows ... 

Acid Sulfite (and Bisulfite) Pulping During acid sulfite pulping the a-hydroxyl and the a-ether groups are cleaved readily under simultaneous formation of benzylium ions (Fig. 7-6). This reaction takes place regardless... 

The so-called soluble bases now are used, with each having certain advantages. Because solutions of sodium, magnesium, and ammonium bisulfite are all soluble at pH 4.5, the current practice is to pulp at the higher pH, which is usually called bisulfite pulping. Extremely long cooking times (7-10 hr) are necessary with acid sulfite, whereas 4-5 hr is sufficient with bisulfite. 

Plants in Europe sometimes use the mineral pyrites (the desired compound in the pyrites is FeS2) as a source of SO2 for the production of sulfite pulping liquor. Pyrite rock containing 48.0 % sulfur is burned completely by flash combustion. All of the iron forms F C>4 in the cinder (the solid product), and a negligible amount of SO3 occurs in either the cinder or the product gas. The gas from such a furnace is passed through milk of lime (CaO in water) absorbers to produce bisulfite pulping liquor. The exit gas from the absorber analyzes SQ 0.7 %, O2 2.9 % and N2 96.4 %. 

Alkali-extracted exploded pulp h Bisulfite pulp 1 Kraft pulp... 

Klason lignin = Roe chlorine number x 0 84 Sulfite and bisulfite pulps... 

Schoning AG, Johansson G (1965) Absorptiometric determination of acid-soluble lignin in semichemical bisulfite pulps and in some woods and plants Sven Papperstidn 68 607-613 Schultz TP, Templeteon MC, McGinnis GD (1985) Rapid determination of lignocellulose by diffuse reflectance Fourier transform infrared spectrometry Anal Chem 57 2867- 2869 Sjostrom E, Enstrom B (1966) Spectrophotometnc determination of the residual lignin in pulp after dissolution in cadoxene Sven Papperstidn 69 469-476... 

Fig. 5.2.9. Absorption spectra of spent liquors of a magnesium bisulfite pulping sequence for spruce. The spectra are measured against water (resolution 4cm 1, 64 scans). 1331, 1150 free S02 1200, 1064, 1022 HSO, 1037 lignosulfonates 1512 aromatic skeletal vibrations of lignin other identified bands indicate increases in the concentrations of organic constituents in the liquor...

Hillis WE, Nelson P, Zadow G (1966) The cause of discoloration of Pinus Radiata bisulfite pulp Appita 19 111-114... 

Conductometric titrimetry can be applied to a wide range of pulp types with a wide range of sulfonate contents. The method has been applied to softwood chips treated with sulfite, softwood sulfite mechanical pulps, high-yield bisulfite pulps, low-yield acid sulfite pulp (Katz et al. 1984, Gummerus 1985, Heitner and Hattula 1988) and sulfite treated aspen wood (Beatson et al. 1985) with sulfonate contents ranging from 20 to 300 mmol kg-1. In addition, the method has been adapted to measure sulfonate content of sulfonated kraft lignin (Oster et al. 1988). 

Alkali-extracted exploded pulp. Bisulfite pulp. 

The discharges from bisulfite pulping and bleaching produce the pulp mill effluents. 

K Kuroda, DR Dimmel. Electron Transfer Reactions in Pulping Systems (VI) Alcohol Bisulfite Pulping. J Wood Chem Technol 12 313, 1992. 

Gray R L, Rickey R G, Hergert H L 1983 The influence of sapwood-heartwood conversion of bordered pit tori in western hemlock on bisulfite pulping. Wood Fiber Sci 15 251-262... 

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