Sulfite mills

Reducing smelting furnaces that produce a high-sulfidity, kraft-like green liquor are now employed at sodium-based sulfite mills. U.S. EPA anticipates that it would be necessary to replace the existing recovery boilers at ammonia-based mills if chemical substitution to a sodium base were employed. Additionally, it is likely that, because the heat value of sodium spent liquor is lower than ammonia spent liquor, evaporator modification may he required if excess capacity does not already exist. 

NONBIOLOGICAL MATERIALS Kraft and sulfite mills United States 1988 104 mills Pulps ... 

Table 12 Characteristics of the Untreated and Biologically Treated Sulfite Mill Effluent...

The EPA passed its "Cluster Rule that requires kraft and soda pulp mills to utilize elemental chlorine-free (ECF) bleaching and all sulfite mills to use ECF or totally chlorine-free (TCF) bleaching. 

Hardwood Kraft Softwood Kraft Sulfite Effluents Kraft mills Sulfite mills Sludge Kraft mills Sulfite mills... 

Parrott, J.L., Wood, C.S., Boutot, P. and Dunn, S. (2003) Changes in growth and secondary sex characteristics of fathead minnows exposed to bleached sulfite mill effluent, Environmental Toxicology and Chemistry 22 (12), 2908-2915. 

Waste water sludges contained mean 2,3,7,8-TCDD concentrations of 101 ppt for kraft mills (maximum 1,390 ppt) and 13 ppt (maximum 58 ppt) for sulfite mills. Furthermore, for all kraft mills, about 38% of the 2,3,7,8-TCDD was partitioned to pulps, 33% to waste water sludges, and 29% to waste water effluents. 

Since the prices of petroleum products have soared, valorization of natural resources has intensively attracted the attention of researchers in different fields. To fully utilize wood, which is a renewable raw material, one must make better use of its 25-30% lignin content which forms the principal dissolved material in the spent liquor of chemical pulping processes. The annual production of sulfite pulp in Canada is approximately 2.6 million tons (data based on 1979), thus, at least one million tons of lignosulfonate is produced, representing a potential resource of raw material for other uses. However, among 35 sulfite mills in Canada, only two or three of them possess a recovery system for spent liquor, that means a very small portion of lignosulfonate has been recovered. The recovered lignin has been... 

Figure 6. HF installation at Toten Sulfite Mill in Norway...

The paper pulping industry is reportedly not, in total, a very large emitter of sulfur oxides, although individual plants may present local problems. Kraft mills emit more malodorous reduced sulfur compounds, whereas sulfite mills are more important as emitters of sulfur dioxide. The pulping processes (particularly sulfite) are most interesting because the chemical recovery cycles use basic chemistry that could well be applied to recovery of sulfur dioxide and sulfur from the flue and process waste gases of other types of sources. 

Lai LX, Bura R.The sulfite mill as a sugar-flexible future biorefinery. Tappi J 2012 11(8) 27—35. 

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