The Effects of the Order of Chemical Addition on the Peroxide Bleaching of an Oxygen-Delignified Softwood Kraft Pulp

Holzforschung ◽  
2000 ◽  
Vol 54 (3) ◽  
pp. 279-286 ◽  
Author(s):  
Luc Lapierre ◽  
Richard Berry ◽  
Jean Bouchard
Keyword(s):  
Sodium Hydroxide ◽  
Kraft Pulp ◽  
Complex Form ◽  
Optimum Concentration ◽  
Operating Conditions ◽  
Pulp Bleaching ◽  
Peroxide Bleaching ◽  
Softwood Kraft Pulp ◽  
Marginal Improvement

Summary In pulp bleaching, while the peroxide-stage chemical charges and the physical operating conditions have been optimized, little attention has been given to the order in which these chemicals are added. We assessed the effects of chemicals, individually and combined, and the effects of the order of addition of these chemicals on peroxide bleaching performance in an acid-treated pulp and in a chelated pulp. We found that adding magnesium to an acid-treated pulp is essential for good peroxide bleaching, while adding magnesium to a chelated pulp provides only a marginal improvement in most additions. But adding magnesium and sodium hydroxide, or sodium hydroxide and magnesium sequentially into a bleaching solution before adding the solution into pulp, causes inefficient peroxide bleaching. This is particularly the case with a chelated pulp. This inefficiency can be avoided if a chelant is added between the additions of magnesium and sodium hydroxide. Magnesium is substantially more effective when in a complex form with either the pulp or a chelant, and the optimum concentration of magnesium for use in peroxide bleaching can be determined by following the peroxide residual.

Application of a Catalyst in Peroxide Bleaching of Eucalyptus Kraft Pulp

Holzforschung ◽  
2000 ◽  
Vol 54 (4) ◽  
pp. 407-412 ◽  
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.

Kraft pulp bleaching with a P-stage catalyzed by both bicarbonate and TAED

TAPPI Journal ◽  
2019 ◽  
Vol 18 (7) ◽  
pp. 409-414
Author(s):  
N. DAS ◽  
S.K. BOSE ◽  
R.C. FRANCIS
Keyword(s):  
Hydrogen Peroxide ◽  
Sodium Bicarbonate ◽  
Sodium Hydroxide ◽  
Sodium Carbonate ◽  
Kraft Pulp ◽  
Kraft Pulps ◽  
Pulp Bleaching ◽  
Peroxide Bleaching ◽  
Kraft Pulp Bleaching ◽  
Peroxide Activation

Peroxide bleaching of softwood and hardwood (eucalypt) kraft pulps was performed in solutions of sodium bicarbonate (NaHCO3), sodium carbonate (Na2CO3), and sodium hydroxide (NaOH). The conventional P stage (hydrogen peroxide + sodium hydroxide; H2O2 + NaOH) was the most effective brightening system without an additional activator. However, peroxide activation by bicarbonate anion (HCO3–) was obvious in all cases where NaHCO3 or Na2CO3 was used. When N,N,N’,N’-tetraacetylethylenediamine (TAED) was added to the bleaching system, Na2CO3 as the alkali source afforded equal or slightly higher bleached brightness compared to NaOH usage for both the softwood and hardwood pulps. This outcome is attributed to simultaneous peroxide activation by HCO3 and TAED. When applied to the eucalypt pulp, the H2O2/Na2CO3/TAED bleaching system also decreased the brightness loss due to thermal reversion.

Optimization of elemental chlorine-free bleaching for a softwood kraft pulp – part 1: impact of oxidative extraction on chlorine dioxide stoichiometry

TAPPI Journal ◽  
2010 ◽  
Vol 9 (8) ◽  
pp. 27-35 ◽  
Author(s):  
BRIAN N. BROGDON
Keyword(s):  
Decision Making ◽  
Chlorine Dioxide ◽  
Kraft Pulp ◽  
Alkaline Extraction ◽  
Pulp Bleaching ◽  
Elemental Chlorine ◽  
Kraft Pulp Bleaching ◽  
Softwood Kraft Pulp ◽  
Chemical Usage ◽  
Minimize Costs

The present investigation meticulously analyzes how oxidative alkaline extraction can be augmented through process changes, and how these augmentations can be leveraged to optimize chlorine dioxide usage with elemental chlorine-free (ECF) sequences for a conventional softwood kraft pulp. Bleaching data from Basta and co-workers (1992 TAPPI Pulping Conference) are re-examined and re-interpreted in this study. We determined that ~60% to 65% of the overall ClO2 charge should be applied in the D0-stage. Peroxide addition to an (EOP) can replace 0.6 to 2.5 Kg. ClO2 per Kg H2O2. Boosting the (EO) temperature to 80°C is equivalent to a 70°C (EOP) with 0.25% to 0.30% H2O2,whereas a 90°C (EO) is equivalent to 0.50% – 0.75% H2O2 in a 70°C (EOP). The stoichiometric bleaching data from this study can guide decision-making for lowering chemical usage and minimize costs to reach target brightness levels with three- and five-stage sequences.

Size-exclusion chromatographic study of ECF and TCF softwood kraft pulp bleaching liquors

2011 ◽  
Vol 18 (7) ◽  
pp. 1049-1056 ◽  
Author(s):  
Jukka Kukkola ◽  
Juha Knuutinen ◽  
Jaakko Paasivirta ◽  
Sirpa Herve ◽  
Piia Pessala ◽  
...  
Keyword(s):  
Kraft Pulp ◽  
Size Exclusion ◽  
Chromatographic Study ◽  
Pulp Bleaching ◽  
Kraft Pulp Bleaching ◽  
Size Exclusion Chromatographic ◽  
Softwood Kraft Pulp

Oxidized Derivatives of Lipophilic Extractives Formed during Hardwood Kraft Pulp Bleaching

Holzforschung ◽  
2003 ◽  
Vol 57 (5) ◽  
pp. 503-512 ◽  
Author(s):  
C. S. R. Freire ◽  
A. J. D. Silvestre ◽  
C. Pascoal Neto
Keyword(s):  
Hydrogen Peroxide ◽  
Chlorine Dioxide ◽  
Kraft Pulp ◽  
Structural Changes ◽  
Oxidation Products ◽  
Pulp Bleaching ◽  
Peroxide Bleaching ◽  
Kraft Pulp Bleaching ◽  
First Time ◽  
Derivatives Of

Summary The structural changes of E. globulus wood extractives during bleaching with chlorine dioxide (D), oxygen (O), ozone (Z) and hydrogen peroxide (P) were studied. The detailed characterisation of the extractive derivatives detected in the partially bleached D, O, P and Z pulps was achieved by performing reactions of pure reference compounds with the different bleaching agents. The results show that the unsaturated sterols and fatty acids are extensively degraded during chlorine dioxide and ozone bleaching and only partially degraded during oxygen and hydrogen peroxide bleaching. The corresponding saturated extractives as well as the long chain aliphatic alcohols and ω-hydroxyfatty acids were stable during bleaching. The main oxidation products of β-sitosterol and oleic and linoleic acids, including one chlorinated derivative of linoleic acid, were identified here for the first time in E. globulus bleached pulps and bleaching filtrates.

Ozone-enhanced bleaching of softwood kraft pulp

TAPPI Journal ◽  
2010 ◽  
Vol 9 (8) ◽  
pp. 16-23 ◽  
Author(s):  
JEAN-CHRISTOPHE HOSTACHY
Keyword(s):  
Capital Investment ◽  
Kraft Pulp ◽  
Operating Cost ◽  
Pulp Mill ◽  
Economic Benefits ◽  
Variable Cost ◽  
Pulp Mills ◽  
Pulp Bleaching ◽  
Softwood Kraft Pulp ◽  
Hardwood Pulp

By using ozone in their bleaching processes, many hardwood pulp mills in various parts of the world have improved product quality and their environmental and process performance, and reduced operating costs to increase competitiveness. The challenge for softwood pulp is to rethink the use of ozone according to their specific requirements. This paper summarizes results obtained using ozone bleaching on softwood (Pinus radiata) kraft pulp, for which the brightening ability of limited ozone dosages can enhance the economic benefits without impairing pulp quality. This work evaluated the chemical justification to use ozone at the end of the bleaching sequence and the effect on pulp quality, and considered the practical consequences of this new option. Special attention was given to the economic and technical aspects, including investment cost, variable cost, and process implementation. Ozone was shown to be the ideal complement of chlorine dioxide for final pulp bleaching. Both chemicals can easily be combined at the end of the bleaching sequence. Taking into account pulp mill capacity, capital investment, and total operating cost, the financial savings were calculated to be in the range of EUR 5 million (USD 6 million) per year, with a payback period of about 1.5 years.

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