Improved steady-state models for chlorine dioxide delignification sequences that include washer carryover effects

TAPPI Journal ◽  
2015 ◽  
Vol 14 (2) ◽  
pp. 93-103 ◽  
Author(s):  
BRIAN N. BROGDON
Keyword(s):  
Steady State ◽  
Chlorine Dioxide ◽  
Control Strategies ◽  
Kappa Number ◽  
Carryover Effects ◽  
Advanced Process Control ◽  
Elemental Chlorine ◽  
Plant Data ◽  
State Models ◽  
Ecf Bleaching

In previous studies, generalized steady-state models were proposed to approximate the chlorine dioxide demand needed for the delignification of softwood and hardwood pulps, where the kappa number entering the bleach plant can fluctuate. However, these expressions neglect the effect of dissolved solids with the stock that originate from incomplete pulp washing. In this study, the original elemental chlorine-free (ECF) models are modified to include the effects of carryover from brownstock or post-oxygen washing. The stoichiometric bleach consumption from carryover, based on its composition, was calculated from various literature sources. The majority of the bleach demand (about 70%) results from the dissolved lignin contained in the brownstock carryover, with the remainder resulting from the inorganic sulfur constituents (e.g., sulfide and thiosulfate). When the effect of brownstock carryover was taken into account, the modified models accurately predicted the amount of chlorine dioxide consumed for a given delignification level (about ±0.1% chlorine dioxide) vs. actual bleach plant data. The improved models can be used to gauge the level of washer carryover entering the bleach plant if this parameter is not regularly monitored by the mill. Additionally, these modified expressions could be integrated into advanced process control strategies for ECF bleaching where the washer carryover or dissolved lignin entrainment is measured with online sensors.

Extension of a steady-state chlorine dioxide brightening model for Z-ECF bleaching of softwood kraft pulps

TAPPI Journal ◽  
2021 ◽  
Vol 20 (3) ◽  
pp. 186-197
Author(s):  
BRIAN N. BROGDON ◽  
LUCIAN A. LUCIAN
Keyword(s):  
Steady State ◽  
Linear Relationship ◽  
Chlorine Dioxide ◽  
Current Model ◽  
Kappa Number ◽  
Kraft Pulps ◽  
Current Investigation ◽  
Elemental Chlorine ◽  
Steady State Model ◽  
Ecf Bleaching

Earlier studies developed a steady-state model to predict the brightness and/or bleach consumption during the chlorine dioxide brightening (D1) of softwood pulps produced by conventional elemental-chlorine-free (ECF) sequences. This model relates the chlorine dioxide consumed to the brightness gains predicated upon an asymptotic D1 brightness limit, an incoming D1 pulp brightness, and an equation parameter (β11). The current investigation examines the application of this model to ECF sequences that use ozone delignification (Z-ECF). Literature D1 data from various Z-ECF bleaching studies, which investigated OZ, OD0/Z, and OZ/D0 delignification, were fitted to the model. The β11 parameter was found to be linearly correlated to the entering kappa number. Interestingly, this linear relationship was found to be identical to the relationships observed when modeling the D1 stage for conventional ECF and chlorine-based bleach sequences. Subtle differences in D1 brightening response in the model among the various bleach sequences are reflected by incoming pulp brightness (at the same kappa number). The current model is used to illustrate how alterations to Z-ECF delignification affect D1 brightening and chlorine dioxide consumption.

Using multistage models to evaluate how pulp washing after the first extraction stage impacts elemental chlorine-free bleach demand

TAPPI Journal ◽  
2018 ◽  
Vol 17 (11) ◽  
pp. 621-630
Author(s):  
Brian Brogdon ◽  
Lucian Lucia
Keyword(s):  
Steady State ◽  
Chlorine Dioxide ◽  
Water Sources ◽  
Elemental Chlorine ◽  
Split Flow ◽  
Extraction Stage ◽  
State Models ◽  
Insight Into ◽  
Ecf Bleaching ◽  
Multistage Models

Steady-state models were constructed to predict the response of a southern U.S. softwood brown¬stock to three- and five-stage elemental chlorine-free (ECF) bleach sequences. The models provided insight into how typical (EO) washing efficiencies from a vacuum drum unit affected pulp brightening and total chlorine dioxide con¬sumption. When (EO) carryover was between 15% and 30%, the chlorine dioxide needed to reach target brightness increased by 8% to 15% for the D0(EO)D1(EP)D2 sequence (89% ISO) and by 15% to 23% for the D0(EO)D1 sequence (86% ISO) versus perfect washing. Use of (EO) filtrate as D0 shower water, such as in split-flow countercurrent wash¬ing, caused the bleach uptake to increase by 1.5 to 3.0 kg chlorine dioxide (ClO2)/ton pulp when compared to using cleaner D0 shower water sources. The ClO2 consumed by 15% to 30% (EO) washer carryover is comparable to that consumed by typical carryover levels from brownstock washing (~10 kg Na2SO4/ton pulp). High (EO) carryover made ECF bleaching to higher brightness targets more difficult.

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 Modification of chlorine dioxide bleaching of Gmelina arborea (gamar) pulp

2017 ◽  
Vol 52 (4) ◽  
pp. 247-252 ◽  
Author(s):  
M Sarwar Jahan ◽  
MM Uddin ◽  
MA Kashem
Keyword(s):  
Chlorine Dioxide ◽  
Kraft Pulp ◽  
Kappa Number ◽  
Side Reactions ◽  
Gmelina Arborea ◽  
Pulp Bleaching ◽  
Bleaching Process ◽  
Elemental Chlorine ◽  
Extraction Stage ◽  
Ecf Bleaching

Elemental Chlorine Free (ECF) pulp bleaching is now the dominant pulp bleaching process in globally. In most bleachery, chlorine dioxide is over-consumed. About two thirds of the chlorine dioxide is wasted in useless side reactions. In the study, kraft pulp from Gmelina arborea (gamar wood) was bleached by ECF bleaching in modified sequences. Oxygen prebleaching was carried out to decrease ClO2 requirement, which reduced kappa number of kraft pulp by 47.6% and increased pulp brightness by 21.7 percent points. Several sequences were tested based on the application of limited charges of ClO2 during successive ClO2and extraction stage. Application of this concept allowed a 33% reduction of ClO2 to reach target brightness. The kraft pulp could not reach target brightness of 80% in DED sequences using even 30 kg ClO2/ton of pulp, while splitting of same amount of ClO2 charge into DEDED sequences reached the pulp brightness to 81.1%. But oxygen delignified kaft pulp reached 79.6% brightness using 25 kg ClO2/ton of pulp in DED sequences. In the splitting of ClO2 charge into DEDED sequences, Oxygen pulp reached to 85% brightness by using only 20 kg ClO2/ton pulp.Bangladesh J. Sci. Ind. Res. 52(4), 247-252, 2017

scholarly journals Revised steady-state model for chlorine dioxide brightening that considers extraction washer carryover effects

TAPPI Journal ◽  
2016 ◽  
Vol 15 (3) ◽  
pp. 178-185 ◽  
Author(s):  
Brian Brogdon
Keyword(s):  
Steady State ◽  
Chlorine Dioxide ◽  
Kappa Number ◽  
Negative Effects ◽  
Carryover Effects ◽  
Dissolved Solids ◽  
Generalized Model ◽  
Stoichiometric Model ◽  
Steady State Model ◽  
Kappa Value

In an earlier investigation, a generalized model was developed to simulate the first chlorine dioxide (ClO2) brightening stage (D1). That stoichiometric model accurately predicts pulp brightness values for given bleach charges and vice versa for laboratory softwood pulps. The equation parameters are dependent on the kappa number and brightness of the extracted pulp. In this study, the earlier model was refined to include the negative effects of extraction carryover to simulate more realistically a mill’s D1 stage. Extracted pulps that contain washer carryover were found to brighten as if the pulp had a kappa number equal to the sum of the extracted kappa and the kappa value of extraction dissolved solids. If this higher kappa (i.e., apparent or wet kappa) is used in place of the extracted kappa with the D1 model, the equations suitably predicted the bleached brightness for a given bleach charge. The modified expressions were used to quantify the amount of carryover and to calculate carryover bleach consumption for a softwood D0(EOP)D1 fiber line. The mill’s washed pulps were found to have carryover levels of 1.4 kappa units, which was consuming 48% of the total D1 bleach charge. Additional analyses revealed that extraction carryover consumes 2.5-4.6 kg ClO2/ton pulp per kappa unit of carryover when bleaching a pulp to 78% to 84% ISO.

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.

scholarly journals Lipophilic Extractives from Eucalyptus globulus Pulp during Kraft Cooking Followed by TCF and ECF Bleaching

Holzforschung ◽  
2001 ◽  
Vol 55 (3) ◽  
pp. 260-264 ◽  
Author(s):  
A. Gutiérrez ◽  
J. Romero ◽  
J.C. del Río
Keyword(s):  
Gas Chromatography ◽  
Chlorine Dioxide ◽  
Eucalyptus Globulus ◽  
Gas Chromatography Mass Spectrometry ◽  
Chemical Analyses ◽  
Wood Extractives ◽  
Elemental Chlorine ◽  
Kraft Cooking ◽  
Ecf Bleaching ◽  
Paper Pulps

SummaryThe chemical composition of lipophilic extractives in paper pulps fromEucalyptus globuluswood during kraft cooking followed by TCF (“totally chlorine free”) and ECF (“elemental chlorine free”) bleaching sequences has been determined by gas chromatography and gas chromatography-mass spectrometry. The chemical analyses revealed that the composition of the lipophilic extractives in pulp after kraft cooking and TCF bleaching with hydrogen peroxide was similar to that ofE. globuluswood extractives, sitosterol and sitosterol esters being the predominant compounds. In contrast, the presence of these compounds was almost negligible in pulp after ECF bleaching with chlorine dioxide and only the saturated sterol stigmastanol, in both free and esterified forms, survived the bleaching.

Transient-Dynamic Model of a Metal V-Belt CVT for Ratio Shift Control Applications

2008 ◽  
Author(s):  
Rohan Bhate ◽  
Nilabh Srivastava
Keyword(s):  
Steady State ◽  
Dynamic Model ◽  
Fuel Economy ◽  
Control Strategies ◽  
Inertial Effects ◽  
Control Applications ◽  
Transient Dynamic ◽  
Axial Forces ◽  
Torque Capacity ◽  
State Models

A continuously variable transmission (CVT) enhances the fuel economy and acceleration performance of a vehicle by allowing the engine to operate at or near its best specific fuel consumption rate for variable driving scenarios. A large volume of work has been reported on the dynamic modeling a metal V-belt CVT system. Most of the models mentioned in literature are steady-state quasi-static equilibrium based or multibody-formalism based, thereby being unsuitable for CVT control applications. Since steady state models fail to accurately capture inertial effects and multibody models present a challenge for control applications due to the large number of bodies involved, the focus of the current work has been to develop a simulation model relatively quick and accurate enough to predict the power transmission behavior and inertial dynamics of a metal pushing V-belt CVT at transient states. The objective of this research is to develop a detailed continuous one-dimensional transient-dynamic model of a metal V-belt CVT system for control applications. The model presented in this work is able to capture the dynamic correlation between the required pulley axial forces and the corresponding transmission ratio. In addition to this, it takes into account detailed inertial effects and predicts the slip behavior and torque capacity of the CVT system under both transient and steady-state regimes. The model proposed in this work would serve as a powerful tool to develop fast, reliable, and accurate controllers for a CVT-equipped driveline to meet the objectives of reduced losses, higher torque capacity, higher vehicle fuel economy and better acceleration performance. The results from the present model subsequently discuss in detail the transient performance of a metal V-belt CVT drive for high torque loading conditions. Various control strategies can be readily implemented with this detailed transient-dynamic model of a metal V-belt CVT system to achieve minimum slip loss and maximum fuel economy and torque capacity.

scholarly journals Chlorine dioxide bleaching of nineteen non-wood plant pulps

2020 ◽  
Vol 35 (4) ◽  
pp. 569-576
Author(s):  
Taslima Ferdous ◽  
M. A. Quaiyyum ◽  
M. Sarwar Jahan
Keyword(s):  
High Temperature ◽  
Wheat Straw ◽  
Chlorine Dioxide ◽  
Kappa Number ◽  
Alkaline Extraction ◽  
Elemental Chlorine ◽  
Wheat Straw Pulp ◽  
Stage D

AbstractBleaching of unbleached and oxygen delignified pulps from nineteen non-wood plants has been evaluated in elemental chlorine free bleaching. Chlorine dioxide charge (kappa factor 0.15, 0.20 and 0.25) and temperature (70 and 85 °C) in the delignification stage (D) were varied. Chlorine dioxide (ClO2) charge and temperature exhibited lower kappa number and higher brightness after alkaline extraction (EP) stage. High temperature ClO2 delignification (DHT) exhibited higher final pulp brightness. The final brightness of wheat straw pulp reached to 90 % after D0/DHT(EP)D1 bleaching, while banana pseudo stem pulp showed the worst bleachability. Residual hexeneuronic acid contents in final pulp from most of the non-wood plants were lower and exhibited 1–2 % higher pulp brightness in DHT process than D0 process. Oxygen delignified pulp and DHT process discharged lower COD load.

scholarly journals Enzymes improve ECF bleaching of pulp

BioResources ◽  
2006 ◽  
Vol 1 (1) ◽  
pp. 34-44 ◽  
Keyword(s):  
Chlorine Dioxide ◽  
Acid Treatment ◽  
Kraft Pulp ◽  
Elemental Chlorine ◽  
Eucalyptus Kraft Pulp ◽  
Mediator System ◽  
Pulp Properties ◽  
Laccase Enzyme ◽  
Ecf Bleaching ◽  
Appreciable Reduction

The delignification efficiency of different laccase enzymes was examined on the eucalyptus Kraft pulp. The laccase enzyme from Trametes versicolor showing the highest delignification efficiency was selected and used in the elemental chlorine-free bleaching sequence for improving the pulp bleachability. A n appreciable reduction in chlorine dioxide consumption was also obtained. Further reduction in chlorine dioxide consumption was obtained when the same laccase treated pulp was subjected to an acid treatment after the extraction stage followed by the DE P D sequence. Elemental-chlorine free bleaching was also performed using the xylanase-laccase treated pulp. Xylanase treatment was incorporated to the laccase mediator system in the elemental-chlorine free bleaching both sequentially and simultaneously. The bleaching sequence DE P D followed and in both the cases, the reduction in chlorine dioxide consumption was greater in comparison to the control. The chlorine dioxide consumption was reduced further when xylanase-laccase treated pulp was given an additional acid treatment. The final pulp properties of the treated pulps were comparable to the control pulp.

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