Liquor white

Kraft pulping is a common process in the paper industry. Figure 8.4 shows a simplifled flowsheet of the process. In this process, wood chips are reacted (cooked) with white liquor in a digester. White liquor (which contains primarily NaOH, NaiS, Na2C03 and water) is employed to dissolve lignin from the wood chips. The cooked pulp and liquor are passed to a blow tank where the pulp is separated from the spent liquor weak black liquor which is fed to a recovery system for... 

A process lean stream and an external MSA are considered for removing H2S. The process lean stream, S1, is a caustic soda solution which can be used as a solvent for the reactive separation of H2S. An added bonus for using the process MSA is the conversion of a portion of the absorbed H2S into Na2S, which is needed for white-liquor makeup. In other words, H2S pollutant is converted into a valuable chemical which is needed in the process. The external MSA, S2, is a polym ic adsorbent. The data for the candidate MSAs are given in Table 8.2. The equilibrium... 

Consid - the Kraft pulping process shown in Fig. 8.8 (Dunn and El-Halwa, 1993). The first step in the process is digestion in which wood chips, containing primarily lignin, cellulose, and hemicellulose, are cooked" in white liquor (NaOH, Na2S, Na2C03 and... 

Ume. -atze, -atztmg /. Calico) white discharge. -bad, n. whitening bath, (in Turkey-red dyeing) white Liquor bath, -baumdi, n, cajuput oil. -bier, n, pale beer specif., weiss beer,... 

The drink, attributed to a bartender named Robert C. Butt at the Oak Beach Inn in Hampton Bays in tire 1970s, has in it every white liquor you can think of—vodka, gin, rum and tequila. It s a frat party in a glass. College students love it. It s right up there with Jell-O shots and Sex on the Beach—a solid B plus (hey, tills is an easy school), says www.student.com, aWebsite devoted to college life. 

Water spray flow to white liquor filter Ib/TADP [1000 2000]... 

The learning process was initiated at the top-digester infimal decision unit, leading to a solution, Xjj, that involves local decision variables and a range of white liquor sulfidity (fraction of active reactants in the white... 

Calcining. In the calcining process, the lime mud removed from the white liquor is burned to regenerate lime for use in the lime mixing step. The vast majority of mills use lime kilns for this process, although a few mills now use newer fluidized bed systems in which the reactants are suspended by upward-blowing air. 

Wood chips are processed in mild chemical liquor and subjected to mechanical refining using disc refiners. Semichemical pulping liquors have variable composition ranging from sodium hydroxide alone, alkaline sulfite (sodium sulfite - - sodium carbonate), mixtures of sodium hydroxide and sodium carbonate, to Kraft green or white liquors [3]. Sodium sulfite/ sodium carbonate liquor is most commonly used and the pulp product obtained thereafter is referred to as neutral sulfite semichemical (NSSC) pulp. 

One of the critical units in the production of paper is a reactor called a digester. In the kraft process this reactor is a two-phase tubular reactor in which the lignin that binds the wood chips together is broken down through a combination of chemical and thermal effects. The white liquor (aqueous solution of sodium hydroxide and hydrosulfide) and solid wood chips flow countercurrently in some zones and co-currently in others. The residence time of the pulp is about 10 h. 

Sulfate or kraft pulping is performed with a solution composed of sodium hydroxide and sodium sulfide, named "white liquor." According to the... 

Fig. 7-20. Equilibrium diagram showing the composition of the kraft white liquor at different pH values. Concentration, 0.2 mole/liter temp., 25°C. Based on equilibrium constants corresponding to = 10 and K> = 10 7.

Of the stabilization methods, the polysulfide pulping process is of practical importance. The influence of polysulfides is based on a specific oxidation of the end groups to carboxyl groups via glucosone intermediates (cf. Section 8.1.3). Polysulfides can be prepared by catalytic oxidation of sulfide in the white liquor or by adding elemental sulfur into the kraft cooking liquor ... 

The Na2S does not react with the lime, so the resultant mixture of NaOH and Na2S (called white liquor ) can be reused to pulp more wood. The CaC03 sludge is filtered off, burned in a lime kiln, and reused. Thus, the chemical... 

In the Kraft recovery process the green liquor, which is an aqueous solution of sodium carbonate, is heated with lime to produce white liquor or caustic soda, which is then returned to the pulp digestion operations. In the production of alumina, lime and soda are fed to bauxite digesters. The CaCO 3 produced during the course of the reaction is rebumed to lime and is recycled. The main difficulties associated with these processes include the extensive mechanical handling through the use of causticizers, settlers, and repulpers in order to produce caustic that is low in carbonate and the high fuel consumption needed to reconvert CaCO to lime. 

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