Chemical pulping applications

McDonough, T. J., Recent Advances in Bleached Chemical Pulp Manufacturing Technology, Part 1 Extended Delignification, Oxygen Delignification, Enzyme Applications, and ECF and TCF Bleaching, Tappi J., 78(3) 55 (1995)... 

Kraft chemical pulp process, 13 94 Kraft lignins, 15 19-20 applications of, 15 19-20 Kraft paper process... 

The pulps obtained from chemical pulping are brown in colour and, whilst suitable for many applications, are unsuitable for printing and writing papers which require a bright white pulp. Both chemical and mechanical pulps often require bleaching for many end uses. The colour of these pulps is mainly due to residual lignin ( 3—6%, see Table 2.2 in Chapter 2) although products derived from carbohydrate may also make a contribution. The approach to removal of colour is different in each case. 

Combustion of Sulfur. For most chemical process applications requiring sulfur dioxide gas or sulfurous acid, sulfur dioxide is prepared by the burning of sulfur or pyrite [1309-36-0], FeS2. A variety of sulfur and pyrite burners have been developed for sulfuric acid and for the pulp (qv) and paper (qv) industries, which produce and immediately consume about 90% of the captive sulfur dioxide produced in the United States. Information on the European sulfur-to-sulfuric acid technology (with emphasis on Lurgi) is available (255). 

The areas of application differ from the industries which apply them the most important ones are the pharmaceuticals, food, fine chemicals, basic chemicals, pulp and paper, agriculture, medicine, energy production, and mining industries (Figure 1.1). 

The crude sodium hydroxide solution is about 12% by weight, commercially acceptable if used nearby. This could be for the chemical pulping of wood, or for soap-making applications. The crude product will contain 2-3% impurities, mainly sodium carbonate with traces of sodium chloride. 

The quality of eucalypt woods for producing chemical pulps was evaluated using NIR spectra and chemometric methods [124]. NIR spectroscopy was used to predict pulp yield and cellulose content from spectra of powdered wood samples [137]. In another application, in addition to estimating lignin content, NIR spectra were used to quantify hardwood-softwood ratios in paperboard [138]. NIR spectra taken from solid European larch samples subjected to axial bending and compression tests revealed an excellent ability to model the variability of mechanical properties [139]. The study demonstrated that the model is based not only on the measurement of density, but also on surface geometry, composition, and, possibly, lignin content. The authors concluded that NIR spectroscopy shows considerable potential to become a tool for nondestructive evaluation of small clear wood specimens, e.g., increment cores. 

Debottlenecking and Retrofitting of Chemical Pulp Refining Process for Paper Manufacturing - Application from Industrial Perspective... 

Numerous applications of electrodeless conductivity sensors have been published for the chemical, pulp and paper, aluminum, mining, and food industries. Similar instrumentation has been used for in situ measurements of the salinity of seawater. An instrument for continuous analysis of oleum in the range of 100-102% equivalent sulfuric acid, with an accuracy of 0.01%, is illustrated in Figure 11. A historical review has been published by Light (see Further Reading). 

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