Comparison of Various Hardwood Kraft Pulp Pre-Bleaching Techniques

TAPPI Journal ◽  
2009 ◽  
Vol 8 (4) ◽  
pp. 10-14 ◽  
Author(s):  
KELLEY SPENCE ◽  
JARROD TUCKER ◽  
PETER W. HART
Keyword(s):  
Chlorine Dioxide ◽  
Kraft Pulp ◽  
Cost Savings ◽  
Acid Pretreatment ◽  
Enzyme Pretreatment ◽  
Xylanase Enzyme ◽  
Pulp Sample ◽  
Mild Acid ◽  
Brightness Curve

We examined five pre-bleaching methods with the same starting hardwood kraft brownstock pulp to determine their effects on reducing bleaching costs. Each pretreated pulp was subjected to a D(EP)D bleaching sequence. A D1 brightness curve as a function of the percent applied chlorine dioxide (ClO2) was obtained for each of these pre-bleaching methods and for a baseline pulp sample. For each of the pre-bleaching methods, we calculated the amount of ClO2 required to obtain D1 stage 79.1% ISO brightness and determined the net cost savings for each sequence. Pre-bleaching methods that produced a net savings in the D1 stage were also subjected to a four-stage bleaching sequence of D(EP)DD to 89%ISO brightness. We also determined net cost savings resulting from pretreat-ment of the fully bleached pulps. The methods examined were mild acid pretreatment, xylanase enzyme pre-bleach-ing, brownstock peroxide pretreatment, acidic brownstock peroxide treatment, and xylanase enzyme followed by acidic peroxide pretreatment. Enzyme pretreatment and small applications of acidic peroxide pretreatment resulted in net D1 stage cost savings at 79.1% ISO brightness. Only enzyme pretreatment resulted in a net savings at 89% ISO.

Prebleaching of eucalypt kraft pulp with OP stages: Effect of an acid pretreatment or chelation step

TAPPI Journal ◽  
2012 ◽  
Vol 11 (6) ◽  
pp. 31-38
Author(s):  
TATIANA M. PÓVOAS ◽  
DINA A.G. ANGÉLICO ◽  
ANA P.V. EGAS ◽  
PEDRO E.G. LOUREIRO ◽  
LICÍNIO M. GANDO-FERREIRA ◽  
...  
Keyword(s):  
Eucalyptus Globulus ◽  
Comparative Evaluation ◽  
Kraft Pulp ◽  
Kraft Pulps ◽  
Acid Pretreatment ◽  
High Brightness ◽  
Pulp Viscosity ◽  
Brightness Reversion

We conducted a comparative evaluation of different treatments for the bleaching of eucalypt kraft pulps beginning with OP stages. The treatments tested were (1) an acid chelation stage with DTPA (OQP sequence); (2) a hot acid stage (AOP sequence); and (3) a chelant addition into the alkaline oxygen stage ((OQ)P and A(OQ)P sequences). The latter strategy was also studied for environmental reasons, as it contributes to the closure of the filtrate cycle. The OQP sequence leads to the highest brightness gain and pulp viscosity and the lowest peroxide consumption caused by an efficient metals control. Considering that the low biodegradability of the chelant is a problem, the A(OQ)P sequence is an interesting option because it leads to reduced peroxide consumption (excluding OQP) while still reaching high brightness values and similar brightness reversion to OQP prebleaching, with only a viscosity loss of 160 dm3/kg. Therefore, a hot acid stage could be considered when a separate acid Q stage is absent in a prebleaching sequence of Eucalyptus globulus kraft pulps involving OP stages.

Application of pure, thermostable, alkali-tolerant xylanase in bleaching of oxygen-delignified pine kraft pulp

TAPPI Journal ◽  
2015 ◽  
Vol 14 (11) ◽  
pp. 689-694
Author(s):  
QINGZHI MA ◽  
QI WANG ◽  
CHU WANG ◽  
NIANJIE FENG ◽  
HUAMIN ZHAI
Keyword(s):  
Intrinsic Viscosity ◽  
Chlorine Dioxide ◽  
High Purity ◽  
Kraft Pulp ◽  
Alkaline Media ◽  
Industrial Scale ◽  
Elemental Chlorine ◽  
Effect Of Oxygen ◽  
Alkaline Tolerant ◽  
Ecf Bleaching

The effect of oxygen (O2)-delignified pine kraft pulp pretreatment by high-purity, thermostable, and alkaline-tolerant xylanases on elemental chlorine free (ECF) bleaching of O2-delignification kraft pulp was studied. The study found that xylanase pretreatment preserved the intrinsic viscosity and yield of O2-delignified pulp while causing about 7% of delignification with high delignification selectivity. The xylanases with high purity, higher thermostability (75°C~80°C) in highly alkaline media (pH 8.0~9.5) could be applied on an industrial scale. Pulp pretreatment by the high-purity, thermostable, and alkaline tolerant xylanases could improve pulp brightness or reduce the chlorine dioxide (ClO2) consumption. In a D0ED1D2 bleaching sequence using the same amount of ClO2, the xylanase-pretreated pulp obtained a higher brightness (88.2% vs. 89.7% ISO) at the enzyme dose of 2 U/g pulp; or for the same brightness as control (88.2% ISO), the ClO2 dosage in the D0 stage was reduced by 27%, which represents a 16% savings in total ClO2 used for bleaching.

Optimization of elemental chlorine-free bleaching for a softwood kraft pulp • part 2: economic analysis of chemical and steam consumption

TAPPI Journal ◽  
2010 ◽  
Vol 9 (9) ◽  
pp. 47-53 ◽  
Author(s):  
BRIAN N. BROGDON
Keyword(s):  
Chlorine Dioxide ◽  
Previous Investigation ◽  
Kraft Pulp ◽  
Energy Costs ◽  
Alkaline Extraction ◽  
Stage Versus ◽  
Kraft Pulps ◽  
Steam Consumption ◽  
Elemental Chlorine ◽  
Softwood Kraft Pulp

Our previous investigation [1] re-analyzed the data from Basta and co-workers (1992 TAPPI Pulping Conference) to demonstrate how oxidative alkaline extraction can be augmented and how these changes affect chlorine dioxide consumption with elemental chlorine-free (ECF) sequences. The current study manipulates extraction delignification variables to curtail bleaching costs with a conventional U.S. Southern softwood kraft pulp. The economic advantages of ~0.35% to 0.65% H2O2 peroxide reinforcement in a 70°C (EOP)-stage versus 90°C (EO)-stage are predisposed to the brightness targets, to short or long bleach sequences, and to mill energy costs. Minimized bleaching costs are generally realized when a 90°C (EO) is employed in D0(EO)D1 bleaching, whereas a 70°C (EOP) is economically advantageous for D0(EOP)D1E2D2 bleaching. The findings we disclose here help to clarify previous ECF optimization studies of conventional softwood kraft pulps.

Action Mechanism of the Improvement of Printability for Eucalypt Bleached Kraft Pulp Pretreated by Cellulase

2013 ◽  
Vol 779-780 ◽  
pp. 294-301
Author(s):  
Wan You Tang ◽  
Li Chen ◽  
Zheng Jian Zhang
Keyword(s):  
Tensile Strength ◽  
Fiber Length ◽  
Kraft Pulp ◽  
Pulp Fiber ◽  
Fiber Morphology ◽  
Strength Index ◽  
Bleached Kraft Pulp ◽  
Tear Index ◽  
Pulp Sample ◽  
The Mean

Enzymatic refining of eucalypt bleached kraft pulp with the cellulase NOV476 was studied. The effects of this cellulase on the physical properties of pulp, fiber morphology and fiber appearance of the eucalypt bleached kraft pulp in different application conditions were discussed. The results show that, with the increase in the amount of enzyme, tensile strength index, burst index and TEA index of paper are increased and then decreased; elongation and tear index of paper have been declining, Zeeil tensile strength index has been an upward trend. Without beating the pulp sample, gradually increases as the amount of enzyme, the average fiber length and the average fiber width are gradually reduced, while mean kink index substantially constant. Number of vessels in fiber overall reduced tendency reaches a minimum in the amount of enzyme 0.5μ/g, the phenomenon is most obvious. In the same conditions of beating time, gradually increases as the amount of enzyme, the average fiber length is gradually reduced, an average fiber width is gradually increased, the mean kink index reaches a maximum in the amount of enzyme is 0.5μ/g. Number of vessels in fiber overall reduced trend.

scholarly journals Method for analysis of ClO2 and Cl2 air emissions from pulp mill

2019 ◽  
Vol 34 (1) ◽  
pp. 19-27
Author(s):  
Kimona Häggström ◽  
Magnus Gunnarsson ◽  
Katarina Bremert-Jirholm ◽  
Nina Simic
Keyword(s):  
Chlorine Dioxide ◽  
Analytical Method ◽  
Kraft Pulp ◽  
Pulp Mill ◽  
Air Emissions ◽  
Pulp Mills ◽  
Limit Of Quantification ◽  
Regulatory Standards ◽  
Low Concentrations ◽  
Kraft Pulp Mills

Abstract Chlorine dioxide is commonly used as a bleaching agent in kraft pulp mills. Scrubbers are required to remove any remaining ClO2 from the plant tail gases. To control the air emissions of chlorine compounds, chlorine dioxide and chlorine contents must be monitored to ensure that the strict regulatory standards are met. However, the currently used analytical method is not suitable for detection of low concentrations of chlorine and chlorine dioxide. A new method for measuring chlorine dioxide and chlorine emissions was developed, which ensures compliance with the stringent requirements imposed by the authorities. The two species could be measured separately with a limit of quantification of 3 ppm. The method was robust and easy to use in the pulp mill environment and it was validated both in the laboratory and the field. The specificity of the method was demonstrated, Cl2 analysis was not sensitive to the presence of ClO2 and vice versa. The uncertainty (±2×RSD) of the analytical method in the field was estimated from duplicate measurements performed in the range of 3–500 ppm for ClO2 and 3–300 ppm for Cl2, and was found to be ±20 % and ±10 %, respectively. Possible interferences in the analytical method are also discussed.

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

scholarly journals Understanding mild acid pretreatment of sugarcane bagasse through particle scale modeling

2013 ◽  
Vol 110 (12) ◽  
pp. 3114-3125 ◽  
Author(s):  
Ava A. Greenwood ◽  
Troy W. Farrell ◽  
Ian M. O'Hara
Keyword(s):  
Sugarcane Bagasse ◽  
Acid Pretreatment ◽  
Scale Modeling ◽  
Mild Acid

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.

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