Soda pulping

S oda—Anthraquinone. A few mills worldwide use soda pulping of hardwoods. In such cases, the addition of anthraquinone is immediately justifiable in terms of increased yield and upgraded pulp quaHty. The conversion of existing kraft mills is not as simple because AQ contributes no alkalinity to the process as sulfide does, and most kraft causticizing systems would have to be expanded by about 33%. This conversion is probably not justifiable in terms of the yield gain. The greatest benefit from AQ is for new mills in which expenditures for air pollution abatement devices can be reduced. 

EPA, 1996b. U.S. EPA, Office of Air Quality Planning and Standards, "Chemical Recovery Combustion Sources at Kraft and Soda Pulp Mills," EPA-453/R-96-012, Research Triangle Park, NC, October, 1996. 

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. 

Miksche, G. E. Lignin reactions in alkaline pulping processes (rate processes in soda pulping). In Chemistry of Delignification with Oxygen, Ozone, and Peroxides Nakano, J. Singh, R. P.,Eds. Uni Publishers Co Tokyo, Japan, 1980 pp. 107-120. 

Sallack (1955) was the first to publish a study of dissolver-tank explosions. He was motivated by incidents which occurred in a soda pulp operation with a dissolver tank 4.3 m in diameter and 3.7 m tall. Molten smelt entered the tank at the top and was to be broken up with a jet of recirculating green liquor. Agitation of the bulk liquid was also accomplished by air jets. Operation was normally smooth, but if a boiler upset led to a sharp increase in smelt flow, then the smelt-green liquor breakup operation was inefficient and unbroken slugs of smelt could enter the bulk green liquor in the tank. Explosions could then occur. 

Lignin contains phenolic and a few carboxylic acid groups it therefore dissolves in sodium hydroxide. Soda pulping is based on this fact. Here, at the high temperatures used, ester bonds arc hydrolyzed, and some of the carbohydrate-lignin ether bonds are split. Cold caustic soda is used for semichemical processes. 

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. 

Salt-cake is used in the soda pulp and in the glass industries, and the demand has at times been greater than can be supplied by the salt-cake as a by-product in the manufacture of hydrochloric acid. As a result, the deposits of Glauber s salts or mirabilite near the Downey Lakes (Laramie, Wyoming), Carrizo Plains (San Louis, Obispo County, Cal.), etc., have been exploited. 

Black liquor Recovery furnaces for krali and soda-pulping processes 5-7... 

SODA PULP PROCESS. SeePulp(YVood)ProductionandProcessing. 

It is useful to compare Kraft pulping to sulfite pulping as a means for understanding differences among these systems. Such a comparison is shown in Table III. Conditions and results for soda pulping are also shown in Table III. Kraft pulping is presented to facilitate comparison. 

Fig. 7-24. Cleavage of /3-aryl ether bonds in nonphenolic phenylpropane units during soda pulping (Gierer, 1970).

Free Phenolic Structures Containing /3-Ary I Ether Bonds The first step of the reaction involves the formation of a quinone methide from the phenolate anion by the elimination of a hydroxide, alkoxide, or phenoxide ion from the a-carbon (Fig. 7-25). The subsequent course of reactions depends on whether hydrosulfide ions are present or not. In the latter case (soda pulping), the dominant reaction is the elimination of the hydroxymethyl group from the quinone methide with formation of formaldehyde and a styryl aryl ether structure without cleavage of the /8-ether bond (Fig. 7-26). When hydrosulfide ions are present (strong nucleophiles) they react with the... 

The culmination of Barrow s important investigations was the production in 1959 of an alkaline engine-sized paper loaded with calcium carbonate (19). The sizing was accomplished using new materials from Hercules, Inc., Kymene and Aquapel. This paper, made from 50% Swedish sulfate and 50% soda pulp, met Barrow s stringent requirement... 

Bland DE (1956) Spectrophotometric determination of lignin in eucalypt soda pulp Appita 10 287-295... 

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