Sulfite pulping process

Substitution Reactions on Side Chains. Because the benzyl carbon is the most reactive site on the propanoid side chain, many substitution reactions occur at this position. Typically, substitution reactions occur by attack of a nucleophilic reagent on a benzyl carbon present in the form of a carbonium ion or a methine group in a quinonemethide stmeture. In a reversal of the ether cleavage reactions described, benzyl alcohols and ethers may be transformed to alkyl or aryl ethers by acid-catalyzed etherifications or transetherifications with alcohol or phenol. The conversion of a benzyl alcohol or ether to a sulfonic acid group is among the most important side chain modification reactions because it is essential to the solubilization of lignin in the sulfite pulping process (17). 

Various permutations of the black liquor recovery boiler design are used to combust soda liquors in the soda pulping process and alkaline earth liquors and ammonium liquor (red liquor) in the sulfite pulping process. 

The use of the lignin fraction is much more cumbersome currently the best-known chemical of a real commercial importance is vanillin, which is obtained by oxidation of the black liquor. Another example is a product called spray-dried lignosulfonate (as sodium salt) obtained from the older, acidic sulfite pulping process. It is sold as a commercial product primarily as a concrete additive for enhanced strength. Since the cement industry is one of the big contributors of carbon dioxide emissions (due to the production of calcium oxide from calcium carbonate), the use of this renewable, wood-derived product not only is fossil-carbon neutral in itself but also reduces carbon dioxide emission due to the diminished need for cement in large infrastructures made of concrete. 

Tall Oil Fatty acids and some unsaponifiable material obtained as a major byproduct from the sulfite-pulping process of wood. 

It was found (3) that the black residual material on the strainer of the sulfite digester was a polymeric sulfur-containing substance. This led us to investigate the reaction between lignosulfonate and sulfur, simulating sulfite pulping process conditions. Under these conditions, a similar polymeric material was formed (3-5). 

In the sulfite pulp process, the digestion fluid is typically made by dissolving sulfur dioxide in water in the presence of limestone until the solution contains 7.0% by weight S02, three-quarters of which is in the form of bisulfite ion. Why is this done In support of your answer to this question, calculate the pH of (a) the digestion solution prepared as above, (b) a hypothetical 7% solution of S02 alone, and (c) an actual saturated solution of S02 alone (2.9% S02), if the first acid dissociation constant of sulfurous acid is 1.7 x 10-2, at ambient temperature and pressure. 

MARATHON-HOWARD PROCESS. A treatment of waste sulfite liquor from sulfite pulp manufacture In recover chemicals and reduce steam pollution. The waste sulfite is treated with line and precipitates. (I) calcium sulfite for use in preparing fresh cooking acid for the sulfite pulp process, and 121 a basic calcium salt tif ligmn sulfonic acid (lignin sullYmalesi that can be pressed and used as a fuel of used as raw- material for vanillin, lignin plasties, and other chemicals. The remaining liquor with its BOD reduced X() ( is the effluent. 

The soda, kraft, and sulfite pulping processes are used to prepare full chemical pulps. The soda process, which uses sodium hydroxide as the cooking chemical for delignification purposes, has hugely been superseded by the kraft process, which is characterized by its use of sodium hydroxide and sodium sulfide as active delignification agenls in the chip-cooking phase of the process. 

In contrast to the highly alkaline (pH 11-13) krafl processes, sulfite pulping processes are acidic in nature and are of two general types (1) the acid sulfite processes utilize caldnm, sodium, magnesium, or ammonium bisulfite in combination with tree or excess sulfur dioxide as... 

SULFITE PULP PROCESS. See Pulp (Wood) Production and Processing. 

Another important event could have been chosen on which to base a centennial—the invention of the sulfite pulping process by the Tilghman brothers in Philadelphia. Although dated as 1866 when a British patent for the process was issued, successful laboratory experiments had been made in 1865. In their attempts to adapt the new method to commercial scale, the Tilghmans tried to develop a continuous process but unfortunately could not solve the technical problems involved. A few years later, at the beginning of the 1870 s, experiments on sulfite pulping were taken up in several places in Europe, and in 1874 the first sulfite pulp was produced commercially by C. D. Ekman in a Swedish mill. 

Black, N. R, ASAM Alkaline sulfite pulping process shows potential for large-scale application. Tappi J1991, 74 (4), 87-93. 

In contrast, the lignins from the sulfite pulping processes are readily available in commercial quantities from several pulp producers in different countries. More than enough is available annually to replace the entire output of synthetic phenol. In aqueous solution, the price of these lignin sulfonates can be as low as 3 cents a pound on a dry basis. The spray-dried forms sell for about 15 cents a pound (>/). Clearly, the process of spray drying is not inexpensive. 

The basis of the sulfite pulping process is the discovery by Tilghman in 1866 that white cellulose fibers are obtained by cooking wood under pressure in an aqueous solution of calcium bisulfite Ca(HS03)2. In chemical terms, the process is founded on the fact that lignin, the solid binder of wood, reacts with sulfite to form water-soluble sulfonic acids. In this fash-... 

In the sulfite pulping process, there are several streams to be dealt with as illustrated in Figure 28. 

Feed Materials. The spent pulping liquors used were from pulp mills using various sulfite pulping processes. To facilitate data presentation, the following code is used for designating the liquors used as feed materials. 

The sulfite pulp process formerly used considerable amounts of lime. Other alkalis are now used e.g. ammonia, magnesia and soda ash, which do not create the waste disposal problems that arise with the use of lime or limestone. 

Uses Filler/extender in plastics, sealants, and coatings raw material for sulfite pulp process in papermaking water treatment chemical ... 

Figure 8.12 Furfural/acetic acid extraction plant to treat the condensate from Lenzing s sulfite pulping process (extraction efficiency -80-90%). ...

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