scholarly journals Displacement washing of softwood pulp cooked to various levels of residual lignin content

TAPPI Journal ◽  
2021 ◽  
Vol 20 (9) ◽  
pp. 553-563
Author(s):  
MD. MOSTAFIZUR RAHMAN ◽  
FRANTISEK POTUCEK
Keyword(s):  
Residence Time ◽  
Peclet Number ◽  
Lignin Content ◽  
Kappa Number ◽  
Residual Lignin ◽  
Pulp Fibers ◽  
Péclet Number ◽  
Softwood Pulp ◽  
Washing Efficiency ◽  
Displacement Washing

This study investigates the influence of the degree of delignification of kraft spruce pulp cooked at seven different kappa numbers, ranging from 18.1 to 50.1, on the efficiency of displacement washing under laboratory conditions. Although the pulp bed is a polydispersive and heterogeneous system, the correlation dependence of the wash yield and bed efficiency on the Péclet number and the kappa number of the pulp showed that washing efficiency increased not only with an increasing Péclet number, but also with an increasing kappa number. The linear dependence between the mean residence time of the solute lignin in the bed and the space time, which reflects the residence time of the wash liquid in the pulp bed, was found for all levels of the kappa number. Washing also reduced the kappa number and the residual lignin content in the pulp fibers.

Lignin modification in the initial phase of softwood kraft pulp delignification with polyoxometalates (POMs)

Holzforschung ◽  
2007 ◽  
Vol 61 (5) ◽  
pp. 492-498 ◽  
Author(s):  
Biljana Bujanovic ◽  
Sally A. Ralph ◽  
Richard S. Reiner ◽  
Rajai H. Atalla
Keyword(s):  
Kraft Pulp ◽  
Lignin Content ◽  
Kappa Number ◽  
Ring Cleavage ◽  
Residual Lignin ◽  
Glucose Content ◽  
Lower Glucose ◽  
Softwood Kraft Pulp ◽  
Alkaline Conditions ◽  
Extraneous Material

Abstract Commercial softwood kraft pulp with kappa number 30.5 (KP30.5) was delignified with polyoxometalates (POM, Na5(+2)[SiV1(-0.1)MoW10(+0.1)O40]), and POM-treated kraft pulp of kappa number 23.6 was obtained (KPPOM,23.6). Residual lignin from pulps was isolated by mild acid hydrolysis and characterized by analytical and spectral methods to gain insight into lignin reactions taking place during the initial delignification phase. Lignin from POM-delignified pulp was isolated in lower yield. Comparative analysis of residual lignins (RL-KP30.5, RL-KPPOM,23.6) showed that POM leads to products enriched in carbonyl/carboxyl groups and carbohydrates. POM lignins have a lower molecular mass and a lower content of phenolic hydroxyl and methoxyl groups. Based on these results and FTIR spectra, we suggest that aromatic ring cleavage and quinone formation occur during POM delignification. The degree of lignin-cellulose association increases after POM delignification. Lignin-cellulose association was found to be partially unstable under mild alkaline conditions, as residual lignin isolated after alkaline extraction of KPPOM,23.6 pulp (RL-KPPOM/NaOH) exhibited lower glucose content, higher Klason lignin content, and less extraneous material.

Sodium sulphite pulping of Scots pine under neutral and mildly alkaline conditions (NS pulping)

Holzforschung ◽  
2016 ◽  
Vol 70 (7) ◽  
pp. 603-609 ◽  
Author(s):  
Saara Hanhikoski ◽  
Elina Warsta ◽  
Antero Varhimo ◽  
Klaus Niemelä ◽  
Tapani Vuorinen
Keyword(s):  
Scots Pine ◽  
Lignin Content ◽  
Kappa Number ◽  
Sulphonic Acid ◽  
Sodium Sulphite ◽  
Residual Lignin ◽  
Initial Ph ◽  
Alkaline Conditions ◽  
Ph Range

Abstract Sodium sulphite pulping of Scots pine chips in the initial pH range of 7.5–9 was investigated at 180°C and 165°C (for 120–240 min), using chemical charges between 25 and 50% and anthraquinone (AQ) charges 0–0.2%. As a result, pulps with yields of 52–73% and kappa numbers of 35–106 were produced. Delignification was accelerated by higher Na2SO3 charges and temperatures, and by AQ addition, whereas the effect of initial pH was negligible. The high pulp yields at a given kappa number were attributable to high retention of hemicelluloses, especially that of galactoglucomannan. The relatively low viscosities of pulps were apparently caused by depolymerisation of cellulose by sulphite. The sulphonic acid groups in the pulps correlated well with the residual lignin content, although some sulphonation of polysaccharides may also be possible. The results indicate that pulping of softwood in buffer-free (without Na2CO3 and/or NaOH) sodium sulphite liquor may result in pulps with tailored characteristics.

Chlorinated Phenolic Compounds in Bleaching Filtrates from a Mixed Eucalyptus and Acacia Pulp Using Different Sequences

Holzforschung ◽  
2000 ◽  
Vol 54 (2) ◽  
pp. 159-164 ◽  
Author(s):  
João L. F. Furtado ◽  
Maria do Carmo R. Peralba ◽  
Cláudia A. Zini ◽  
Elina B. Caramão
Keyword(s):  
Phenolic Compounds ◽  
Lignin Content ◽  
Kappa Number ◽  
Acacia Mearnsii ◽  
Eucalyptus Saligna ◽  
Cellulose Pulp ◽  
Softwood Pulp ◽  
Stage D ◽  
Chlorinated Phenolic Compounds

Summary Bench filtrates from three-stage conventional bleaching sequences (CEoD) with substitution degrees of chlorine by chlorine dioxide in the first stage equals to zero, 25%, 75% and 100% have been analysed for their content of chlorinated phenolic compounds (CPCs). Alternatively, CPCs filtrates content of an AZEoPD sequence were also determined. A cellulose pulp obtained from a mixture of 85% Eucalyptus saligna (young trees) and 15% Acacia mearnsii delignified with oxygen (kappa number 10.0) was employed in all bleaching tests. Levels of CPCs were determined by using an in situ acetylation method followed by GC/ECD technique. GC/MS of bleaching filtrates was employed in qualitative analyses. CPCs content in filtrates and the Kovacs' equivalent toxicity for the total filtrates of the studied bleaching sequences are presented. The lowest content of CPCs was found in AZEoPD filtrates, as expected due to the utilised bleaching agents. CPCs were not detected in the filtrates of stage D from the AZEoPD sequence probably due to the low lignin content of the pulp. Mixed filtrates of the sequence DEoD, showed the lowest CPCs content among conventional bleachings. Results are in accordance with those found in the literature for hardwood and softwood pulp. The equivalent toxicity in the sequences Dc(75/25), DEoD and AZEoPD was found to be lower than the limit given by Kovacs to characterise chronical toxicity.

scholarly journals A parsimonious approach for large-scale tracer test interpretation

2021 ◽  
Author(s):  
Vincent Bailly-Comte ◽  
Séverin Pistre
Keyword(s):  
Linear Relationship ◽  
Residence Time ◽  
Peclet Number ◽  
Time Distribution ◽  
Residence Time Distribution ◽  
Large Scale ◽  
Tracer Test ◽  
Transport Processes ◽  
Peak Time ◽  
Péclet Number

AbstractDye tracing is an efficient method for spring watershed delineation, but is also used in surface waters to assess pollution migration over several kilometers. The aim of this study is to develop a simple and parsimonious approach that accounts for a linear relationship between dispersivity and scale that could be used for the simulation of large-scale transport processes in aquifers. The analysis of 583 tracer recoveries is used to validate an inverse relationship between arrival time and peak concentration, which is shown to be a consequence of the linear relationship between dispersivity and scale. These results show that the tracer displacement through a given tracing system can be characterized at a large scale by a constant Peclet number. This interpretation is used to propose a new approach for tracer test design based on the analytical expression of the peak/time factor. It is also used for Peclet number assessment and simulation of the whole tracer residence-time distribution using a new method based on the ratio between the mode of the residence time distribution (hmod) and the corresponding time from injection (tmod), which is called the hmod/tmod method. This methodology is applied to two tracer tests carried out in a karst aquifer over 13 km between the same injection and detection points under distinct hydrological conditions. These results found practical applications in generalizing tracer test results to various flow conditions, or guiding the parameterization of physically-based vulnerability mapping methods.

Residence time distribution and Peclet number correlation for continuous oscillatory flow reactors

2017 ◽  
Vol 92 (8) ◽  
pp. 2178-2188 ◽  
Author(s):  
Danijela S Slavnić ◽  
Luka V Živković ◽  
Ana V Bjelić ◽  
Branko M Bugarski ◽  
Nikola M Nikačević
Keyword(s):  
Residence Time ◽  
Peclet Number ◽  
Time Distribution ◽  
Residence Time Distribution ◽  
Oscillatory Flow ◽  
Flow Reactors ◽  
Péclet Number

Does the kappa number method accurately reflect lignin content in nonwood pulps?

TAPPI Journal ◽  
2018 ◽  
Vol 17 (11) ◽  
pp. 611-617
Author(s):  
Sabrina Burkhardt
Keyword(s):  
Lignin Content ◽  
Paper Industry ◽  
Pulp And Paper Industry ◽  
Original Data ◽  
Kappa Number ◽  
Klason Lignin ◽  
Organic Functional Groups ◽  
Pulp Properties ◽  
Wood Pulps ◽  
Hexenuronic Acid

The traditional kappa number method was developed in 1960 as a way to more quickly determine the level of lignin remaining in a completed or in-progress pulp. A significantly faster approach than the Klason lignin procedure, the kappa number method is based on the reaction of a strong oxidizing agent (KMnO4) with lignin and small amounts of other organic functional groups present in the pulp, such as hexenuronic acid. While the usefulness of the kappa number for providing information about bleaching requirements and pulp properties has arguably transformed the pulp and paper industry, it has been mostly developed for kraft, sulfite, and soda wood pulps. Nonwood species have a different chemical makeup than hardwood or softwood sources. These chemical differ-ences can influence kappa and Klason measurements on the pulp and lead to wide ranges of error. Both original data from Sustainable Fiber Technologies’ sulfur and chlorine-free pulping process and kappa and Klason data from various nonwood pulp literature sources will be presented to challenge the assumption that the kappa number accurately represents lignin content in nonwood pulps.

Approximate analysis of the containment of contaminated sites prior to remediation

2000 ◽  
Vol 42 (1-2) ◽  
pp. 319-324 ◽  
Author(s):  
H. Rubin ◽  
A. Rabideau
Keyword(s):  
Steady State ◽  
Peclet Number ◽  
Dimensionless Parameter ◽  
Contaminated Sites ◽  
Unsteady State ◽  
Péclet Number ◽  
Vertical Barrier ◽  
Time Period ◽  
Barrier Performance ◽  
Vertical Barriers

This study presents an approximate analytical model, which can be useful for the prediction and requirement of vertical barrier efficiencies. A previous study by the authors has indicated that a single dimensionless parameter determines the performance of a vertical barrier. This parameter is termed the barrier Peclet number. The evaluation of barrier performance concerns operation under steady state conditions, as well as estimates of unsteady state conditions and calculation of the time period requires arriving at steady state conditions. This study refers to high values of the barrier Peclet number. The modeling approach refers to the development of several types of boundary layers. Comparisons were made between simulation results of the present study and some analytical and numerical results. These comparisons indicate that the models developed in this study could be useful in the design and prediction of the performance of vertical barriers operating under conditions of high values of the barrier Peclet number.

Convective diffusion toward the sphere in laminar flow around the sphere

1979 ◽  
Vol 44 (4) ◽  
pp. 1218-1238
Author(s):  
Arnošt Kimla ◽  
Jiří Míčka
Keyword(s):  
Laminar Flow ◽  
Velocity Profile ◽  
Peclet Number ◽  
Convective Diffusion ◽  
Péclet Number ◽  
Stability Of The Solution

The problem of convective diffusion toward the sphere in laminar flow around the sphere is solved by combination of the analytical and net methods for the region of Peclet number λ ≥ 1. The problem was also studied for very small values λ. Stability of the solution has been proved in relation to changes of the velocity profile.

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