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chemical reactor analysis of industrial oxygen delignification

Pulp & paper Canada, 2003-12, Vol.104 (12), p.96-101

2004 INIST-CNRS ;Copyright Southam Business Communications, Inc. Dec 2003 ;ISSN: 0316-4004 ;EISSN: 1923-3515 ;CODEN: PPCADD

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  • Title:
    chemical reactor analysis of industrial oxygen delignification
  • Author: Van Heiningen, A ; Krothapalli, D ; Genco, J ; Justason, A
  • Subjects: Applied sciences ; delignification ; Exact sciences and technology ; Kinetics ; Lignin ; Oxidation ; Paper, paperboard, non wovens ; Polymer industry, paints, wood ; Pulp & paper industry ; pulp fiber ; Pulp manufacturing ; Technology ; wood pulp ; Wood. Paper. Non wovens
  • Is Part Of: Pulp & paper Canada, 2003-12, Vol.104 (12), p.96-101
  • Description: [Symbol Not Transcribed] [epsilon] k[Symbol Not Transcribed]a c[Symbol Not Transcribed] Ft;= c[Symbol Not Transcribed]/c[Symbol Not Transcribed] F[Symbol Not Transcribed] = (O[Symbol Not Transcribed] [Symbol Not Transcribed] [center dot] uptake/O[Symbol Not Transcribed] [Symbol Not Transcribed][center dot] charged) F[Symbol Not Transcribed] = (O[Symbol Not Transcribed] [Symbol Not Transcribed] [center dot] reacted/O[Symbol Not Transcribed][Symbol Not Transcribed] [center dot] dissolved) ([Symbol Not Transcribed] [delta]Kappa)[Symbol Not Transcribed] where M[Symbol Not Transcribed] is the non-dimensional Weisz Modulus and (-r[Symbol Not Transcribed] [straight double quote][Symbol Not Transcribed][Symbol Not Transcribed]) is the oxygen consumption rate per unit volume of fibre wall (moles O[Symbol Not Transcribed]/L fibre wall/s). The saturated oxygen concentration, C[Symbol Not Transcribed], at 95[Symbol Not Transcribed] [degree]C and oxygen pressure of 120 psia is 6.363 [Symbol Not Transcribed] [times] 10[Symbol Not Transcribed] moles O[Symbol Not Transcribed]/L liquid. The highest value of (-r[Symbol Not Transcribed] [straight double quote][Symbol Not Transcribed][Symbol Not Transcribed]) occurs at the start of delignification, and can be calculated as: Effect of Tower Operation on Oxygen Dissolution and Pulp Delignification: Simulation of the tower operation was performed for the base case, [Symbol Not Transcribed] [epsilon] = 1 [Symbol Not Transcribed] [times] 10[Symbol Not Transcribed] W/m[Symbol Not Transcribed], and different values of k[Symbol Not Transcribed]a of 0.002 to 0.01 s[Symbol Not Transcribed], selected based on laboratory measurements by Rewatkar and Bennington (1). The development of the kappa number in the tower at the different mass transfer rates is shown in Fig. 2. It can be seen that the kappa number of the pulp entering the tower is indistinguishable from the value of 26 entering the mixer. Furthermore the figure shows that over the range of values of k[Symbol Not Transcribed]a reasonable delignifications are obtained after almost 60 minutes retention time. Also shown in Fig. 2 is the kappa development for k[Symbol Not Transcribed]a of infinity (actually a very large value of 10 s[Symbol Not Transcribed]). This line represents the situation whereby there is no mass transfer limitation for oxygen, i.e., the delignification is purely controlled by chemical kinetics. It can be seen that this curve displays the characteristic behaviour of a continuously decreasing rate of delignification as time progresses. On the other hand, the shape of the delignification curves for the values of k[Symbol Not Transcribed]a of 0.002 to 0.01 s[Symbol Not Transcribed] display a small inflexion point at roughly 5 minutes retention time, signifying that initially in the tower the delignification rate increases up to about 5 minutes and then decreases. This can be explained by the fact that initially the delignification rate is small because the liquid is not yet oxygenated. This initial increase in dissolved oxygen concentration is clearly seen in Fig. 1A.
  • Publisher: Don Mills, ON: Southam
  • Language: English
  • Identifier: ISSN: 0316-4004
    EISSN: 1923-3515
    CODEN: PPCADD
  • Source: ProQuest Central
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