The Impact of Xylanase and Hot Acid Pretreatment on HexAs in Eucalyptus Kraft Pulp Bleaching

Mills have largely used chlorine dioxide (ClO2) for eucalyptus kraft pulp bleaching. Different mills have observed significant variation in ClO2 demand to reach full brightness (≥90 ISO). These large differences in ClO2 consumption derive from many factors. The most significant include differences in carryover loads and hexenuronic acid (HexA) contents and the level of chlorate formation across bleaching. Handling of pulp with high HexA content and ClO2 losses to chlorate can be minimized by proper operation of the ClO2 stages across the bleach plant. An oxygen delignified eucalyptus kraft pulp with a kappa of 10-12 units contains only 4-6 units actually derived from lignin. This scarce amount of lignin (0.6%-0.9%) is not able to consume high ClO2 doses and, as a consequence, the excess ClO2 applied can end up being converted into chlorate. Hence, proper optimization of ClO2 bleaching stages can save significant amounts of this oxidant. This study focused on optimizing ClO2 bleaching for a typical oxygen delignified eucalyptus kraft pulp of kappa number 11.7. Elemental chlorine free bleaching was carried out with the D0-(EP)-D1 sequence. The following conditions were varied in the D0 stage: temperature, end pH, and kappa factor. The results indicated that maximum ClO2 bleaching efficiency is achieved when minimum chlorate is formed, especially when ClO2 bleaching is adjusted in such a way that residual active chlorine is maintained to a minimum. The most significant variable affecting chlorate formation is pH; however, ClO2 doses (ClO2 concentration) also play a very important role. Chlorate formation is more intense in the D1 stage in relation to the D0 stage. Optimum conditions to run the D0 stage were 90°C, 3.5 pH, and 0.22 kappa factor.

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Application of a Catalyst in Peroxide Bleaching of Eucalyptus Kraft Pulp

Holzforschung ◽

10.1515/hf.2000.068 ◽

2000 ◽

Vol 54 (4) ◽

pp. 407-412 ◽

Cited By ~ 8

Author(s):

L. Kühne ◽

J. Odermatt ◽

T. Wachter

Keyword(s):

Hydrogen Peroxide ◽

Kraft Pulp ◽

Pulp Bleaching ◽

Selective Catalyst ◽

Peroxide Bleaching ◽

Softwood Pulp ◽

Kraft Pulp Bleaching ◽

Eucalyptus Kraft Pulp ◽

Softwood Kraft Pulp

Summary A binuclear [Mn(III)Mn(IV)(μ-O)2(μ-CH3COO)L](ClO4−)2 complex with L = 1,2 Bis-(4,7-dimethyl-1,4,7-triazacyclonon-1-yl)-ethane, described as a selective catalyst in hydrogen peroxide bleaching of softwood pulps, was tested in hardwood kraft pulp bleaching. The catalyst application gave rise to a higher consumption of peroxide which resulted in higher pulp brightness. The delignification improvement caused by the catalyst was shown to be much lower compared to catalysed peroxide bleaching of softwood kraft pulp. In contrast to the results of softwood pulp bleaching no selectivity improvements could be found when using the catalyst in bleaching of eucalyptus kraft pulp.

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Integrating a Xylanase Treatment into an Industrial-Type Sequence for Eucalyptus Kraft Pulp Bleaching

Industrial & Engineering Chemistry Research ◽

10.1021/ie202863d ◽

2012 ◽

Vol 51 (7) ◽

pp. 2830-2837 ◽

Cited By ~ 6

Author(s):

Ursula Fillat ◽

María Blanca Roncero ◽

Vera M. Sacón ◽

Alexandre Bassa

Keyword(s):

Kraft Pulp ◽

Pulp Bleaching ◽

Kraft Pulp Bleaching ◽

Eucalyptus Kraft Pulp ◽

Type Sequence

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Optimizing Alkaline Extraction for Eucalyptus Kraft Pulp Bleaching

TAPPI Journal ◽

10.32964/tj8.1.12 ◽

2009 ◽

Vol 8 (1) ◽

pp. 12-19

Author(s):

LEWIS D. SHACKFORD ◽

CARLOS A. SANTOS ◽

JORGE L. COLODETTE ◽

ERICKA F. ALVES

Keyword(s):

Cost Effectiveness ◽

Kraft Pulp ◽

Alkaline Extraction ◽

Cost Advantage ◽

Pulp Bleaching ◽

Eucalyptus Pulp ◽

Kraft Pulp Bleaching ◽

Eucalyptus Kraft Pulp ◽

Chlorine Demand ◽

The Cost

This paper evaluates different approaches for the (E*) stage of the DHT(E*)D sequence for eucalyp-tus kraft pulp bleaching to 90%–91% ISO brightness, considering kappa factors 0.12, 0.16, and 0.20 in the first stage. These (E*) approaches included E, (EO), (EP), (EOP), (PO), PHT, O, and (O/O) stages run at two tempera-tures. Results were compared on the basis of total active chlorine demand, chemical cost, pulp brightness stability and viscosity, and effluent load. We concluded that a DHT kappa factor of 0.12 and a (PO) stage run at 85°C–95°C appeared to be the most attractive approach for bleaching eucalyptus pulp with the DHT(E*)D sequence, consider-ing cost-effectiveness, pulp quality, and effluent load; however, when the steam cost is taken into consideration, the cost advantage was lost.

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