The Effect of Process Variables in Chlorine Dioxide Prebleaching of Birch Kraft Pulp. Part 1. Inorganic Chlorine Compounds, Kappa Number, Lignin, and Hexenuronic Acid Content

2010 ◽  
Vol 30 (1) ◽  
pp. 1-18 ◽  
Author(s):  
Tuula Lehtimaa ◽  
Ville Tarvo ◽  
Susanna Kuitunen ◽  
Anna-Stiina Jääskeläinen ◽  
Tapani Vuorinen
Keyword(s):  
Chlorine Dioxide ◽  
Acid Content ◽  
Kraft Pulp ◽  
Kappa Number ◽  
Process Variables ◽  
Birch Kraft Pulp ◽  
Hexenuronic Acid

Voltammetric analysis of the bleachability of softwood kraft pulps

Holzforschung ◽  
2004 ◽  
Vol 58 (6) ◽  
pp. 581-587 ◽  
Author(s):  
Robert Bourbonnais ◽  
Loredana Valeanu ◽  
Michael G. Paice
Keyword(s):  
Chlorine Dioxide ◽  
Acid Content ◽  
Black Spruce ◽  
Kappa Number ◽  
Western Hemlock ◽  
Kraft Pulps ◽  
Residual Lignin ◽  
Redox Mediators ◽  
Voltammetric Analysis ◽  
Hexenuronic Acid

Abstract Kraft and oxygen delignified pulps with various kappa numbers were prepared from black spruce and western hemlock chips. The bleachability (ratio of kappa number decrease to chlorine dioxide applied) of the different pulps at the same kappa number varied with both wood furnish and delignification process. Thus, unbleached kappa number alone is not a reliable indicator of bleachability for these pulps. This may be due in part to the variable hexenuronic acid content of the pulps; those with higher ratio of hexenuronic acid content to kappa number (HexA/kappa) are harder to bleach. Voltammetric analysis of the same kraft pulps in the presence of redox mediators was found to measure both the content and reactivity of residual lignin. Peak current ratios of redox mediators correlated with pulp bleachability for all pulps. These ratios may therefore provide a more accurate prediction of bleachability than unbleached kappa number.

The Effect of Process Variables in Chlorine Dioxide Prebleaching of Birch Kraft Pulp. Part 2. AOX and OX Formation

2010 ◽  
Vol 30 (1) ◽  
pp. 19-30 ◽  
Author(s):  
Tuula Lehtimaa ◽  
Ville Tarvo ◽  
Susanna Kuitunen ◽  
Anna-Stiina Jääskeläinen ◽  
Tapani Vuorinen
Keyword(s):  
Chlorine Dioxide ◽  
Kraft Pulp ◽  
Process Variables ◽  
Birch Kraft Pulp

Enhancement of eucalypt pulp yield through extended impregnation cooking

2018 ◽  
Vol 33 (2) ◽  
pp. 175-185 ◽  
Author(s):  
Gustavo B. de Souza ◽  
Jorge Luiz Colodette ◽  
Fernando José Borges Gomes ◽  
Danila Morais de Carvalho
Keyword(s):  
Chlorine Dioxide ◽  
Kraft Pulp ◽  
Strength Properties ◽  
Kraft Pulping ◽  
Kappa Number ◽  
Pulp Yield

AbstractThe improvement caused by eucalypt chip impregnation on kraft pulping performance was assessed for terminating the cook at kappa in the range of 15–27 and at controlled residual effective alkali (REA) of 6–8 g/L NaOH. Extended impregnation cooking of eucalypt chips (EIC) increased about 1 %lignin- and HexA-freescreen yield gains in relation to conventional cooking (CC), regardless of kappa number in the range of 15–27. The EIC technology allows for cooking eucalypt wood to kappa number up to 27, without rejects production, but without significant improvement inlignin- and HexA-freescreen yield and with larger chlorine dioxide (ClO2) consume during bleaching. The optimum kappa number for both CC and EIC cooking was about 19 with similar refinability and strength properties for both technologies, CC and EIC. It was concluded that extended impregnation cooking is an attractive technique for enhancing bleached eucalypt Kraft pulp yield.

Hydrogen peroxide and supercritical carbon dioxide: a new bleaching stage for Eucalyptus kraft-O2 pulps

Holzforschung ◽  
2011 ◽  
Vol 65 (3) ◽  
Author(s):  
Roberta Pacheco Francisco ◽  
Jorge Luiz Colodette ◽  
Antonio Aprigio da Silva Curvelo
Keyword(s):  
Carbon Dioxide ◽  
Hydrogen Peroxide ◽  
Supercritical Carbon Dioxide ◽  
Kraft Pulp ◽  
Poor Performance ◽  
Kappa Number ◽  
Elemental Chlorine ◽  
Chlorine Gas ◽  
Hexenuronic Acid ◽  
Supercritical Carbon

Abstract Kraft pulp is currently bleached largely by the elemental chlorine free (ECF) technology with oxygen, chlorine dioxide, and hydrogen as active agents. This technology brought about significant environmental improvements in relation to standard processes based on chlorine gas and hypochlorite, but there is still need for further improvements. This study presents a novel environmentally friendly bleaching stage – the so-called ‘hydrogen peroxide in supercritical carbon dioxide’, P(SC-CO2) – that can be adapted to current ECF bleaching processes, with preference in cases where hydrogen peroxide is already used. In this study, the P(SC-CO2) stage was evaluated as a replacement to the last peroxide stage of the D(EP)DP bleaching sequence and to the first peroxide stage of the D(EP)DP sequence, for an oxygen delignified eucalypt kraft-O2 pulp. The P(SC-CO2) stage was run with 0.5% hydrogen peroxide, at 15% consistency, 70°C, and 73 bar. The reaction time was 30 min. The performances of regular P stages and the new P(SC-CO2) stage were compared. Promising results were observed with the DEP(SC-CO2)DP sequence; the P(SC-CO2) decreased kappa number from 2.7 to 2.1, and the hexenuronic acid groups from 17.0 to 12.4 mmol kg-1. The P(SC-CO2) stage showed poor performance when applied in the D(EP)DP(SC-CO2) sequence. It is concluded that the process presents potential but requires further optimization to improve selectivity and efficiency.

ECF Bleaching of Pre-Hydrolyzed Larix Kraft Pulp for Production of Dissolving Pulp

2013 ◽  
Vol 634-638 ◽  
pp. 386-390
Author(s):  
Zhi Li ◽  
Jun Li ◽  
Jun Xu
Keyword(s):  
Hydrogen Peroxide ◽  
Chlorine Dioxide ◽  
Kraft Pulp ◽  
Kappa Number ◽  
Alkaline Extraction ◽  
Polymerization Degree ◽  
Oxygen Delignification ◽  
Elemental Chlorine ◽  
Pulp Properties ◽  
Ecf Bleaching

Elemental Chlorine Free (ECF) bleaching sequence of O1/O2D0EOPD1D2 was adopted to bleach the pro-hydrolyzed Larix kraft pulp, where O1/O2 was two-stage oxygen delignification without interstage treatment, D was chlorine dioxide bleaching, EOP was pressurized alkaline extraction strengthened by hydrogen peroxide. Keeping bleaching temperature and time unchanged, sodium hydroxide charge(NaOH) in O1 stage, chlorine dioxide(ClO2) charge in D0 stage and D2 stage were studied, pulp properties such as brightness, kappa number, alpha-cellulose, pentosan and polymerization degree were measured and compared to establish optimal bleaching conditions. Results show that the optimal charge of NaOH in O1 stage is 2.5%, ClO2 in D0 and D2 stage are 2.5%, 0.6%, and the pulp gained at the optimal bleaching conditions has the properties of 93.9% of alpha-cellulose, 2.60% of pentosan, 375.5 ml/g of viscosity and 86.6%ISO of brightness.

scholarly journals Assessment of Q(OP)D(PO) bleachability of softwood kraft pulp

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Sara Starrsjö ◽  
Maria Boman ◽  
Olena Sevastyanova ◽  
Mikael E. Lindström ◽  
Juha Fiskari
Keyword(s):  
Kraft Pulp ◽  
Kappa Number ◽  
Carbohydrate Content ◽  
Residual Lignin ◽  
Three Samples ◽  
Softwood Kraft Pulp ◽  
Pulp Sample ◽  
Yield Gain ◽  
Hexenuronic Acid

Abstract Bleachability is evaluated as how easily a pulp sample is bleached and it depends on the structure of residual lignin and carbohydrates. Also, the bleachability varies depending on the bleaching sequence. ECF light sequences have been improved significantly in the recent years. However, we still don’t fully understand how ECF light bleach plants are optimally run. This work studies the bleachability of softwood kraft pulp in an ECF light bleaching sequence, (OO)Q(OP)D(PO). Three pulp samples with brown stock kappa number 27, 32 and 35 were bleached and studied for residual lignin, hexenuronic acid and carbohydrate content. It was found that in the bleaching stages that are highly delignifying, it is beneficial with a higher kappa number for the delignifying bleachability. However, in the bleaching stages where the objective is brightness increase, the brightness gain bleachability is improved by a lower kappa number. We also intended to determine which of the three samples had the best suited kappa number for this particular bleaching sequence. According to our results, the bleaching was most effective with kappa number around 32. Although an even higher kappa number resulted in higher yield after cooking, it seemed that this bleaching sequence cannot preserve the yield gain.

Effects of D0-stage temperature, pH, and kappa factor on chlorine dioxide decomposition and D0-(EP)-D1 bleaching performance for eucalypt pulps

TAPPI Journal ◽  
2016 ◽  
Vol 15 (4) ◽  
pp. 285-295 ◽  
Author(s):  
UMIT SEZGI ◽  
JANAINA RESENDE ◽  
LEWIS SHACKFORD ◽  
JORGE COLODETTE ◽  
MARCELA ANDRADE
Keyword(s):  
Chlorine Dioxide ◽  
Kraft Pulp ◽  
Significant Variable ◽  
Optimum Conditions ◽  
Pulp Bleaching ◽  
Elemental Chlorine ◽  
Kraft Pulp Bleaching ◽  
Eucalyptus Kraft Pulp ◽  
Hexenuronic Acid ◽  
Proper Operation

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.

Antioxidant property of TCF pulp with a high hexenuronic acid (HexA) content

Holzforschung ◽  
2013 ◽  
Vol 67 (3) ◽  
pp. 257-263 ◽  
Author(s):  
Cristina Valls ◽  
M. Blanca Roncero
Keyword(s):  
Kraft Pulp ◽  
Antioxidant Property ◽  
Kappa Number ◽  
Raw Material ◽  
Antioxidant Power ◽  
Elemental Chlorine ◽  
Enzyme Pretreatment ◽  
Extraction Stage ◽  
Hexenuronic Acid ◽  
Oxidized Products

Abstract Totally chlorine free (TCF) pulp with a high content of hexenuronic acids (HexAs) was found to possess a high antioxidant power. The contribution of HexA to kappa number in unbleached Eucalyptus globulus kraft pulp was estimated to be 1.05 units per 10 μmol of HexA. The variation of HexA and lignin contents in enzymatic elemental chlorine free (ECF) and TCF sequences was monitored, and interesting effects were observed during the TCF XLE sequence, where X denotes an enzyme pretreatment with xylanase, L a laccase-mediator stage, and E an alkaline extraction stage. Thus, HexA removal during L stage was strongly enhanced after the X stage; also, the HexA content was decreased by the alkaline stage. None of these effects was observed in the ECF sequence with chlorine dioxide. The antioxidant power detected in HexA makes TCF pulp an excellent raw material for manufacturing packaging for easily oxidized products.

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