scholarly journals Modelling and optimization of the last two stages of an environmentally-compatible TCF bleaching sequence

BioResources ◽  
2018 ◽  
Vol 13 (3) ◽  
pp. 6642-6662
Author(s):  
Tamara Llano ◽  
Carlos Arce ◽  
Gema Ruiz ◽  
Naveen Chenna ◽  
Alberto Coz
Keyword(s):  
Linear Optimization ◽  
Cost Savings ◽  
Pulp Mill ◽  
Nanofibrillated Cellulose ◽  
Regenerated Cellulose ◽  
Cellulose Content ◽  
Quality Properties ◽  
Operational Conditions ◽  
Dissolving Pulps ◽  
Two Stages

A totally chlorine free (TCF) bleaching sequence was studied for an acid sulfite pulp mill that produces dissolving pulps. Laboratory analyses of the last two bleaching stages, an oxidant-reinforced alkaline extraction stage (EOP), and a subsequent pressurized peroxide with oxygen stage (PO), were performed on a eucalypt pulp that had been delignified by an ozone (Z) stage in the pulp mill. The goal was to predict the optimal costs and operational conditions for the (EOP)(PO) partial bleach sequence for three different specialty pulp products. Four independent variables affecting the pulp quality properties were examined for each stage (i.e., reaction temperature, reaction time, NaOH dosage and H2O2 dosage). The dependent variables were various pulp properties, such as intrinsic pulp viscosity, alpha-cellulose content, kappa number, and GE brightness. Three scenarios were considered to optimize the bleaching process, which related to a regenerated cellulose product (viscose) that is widely commercialized, and to two novel products (nanocrystalline cellulose (NCC) and nanofibrillated cellulose (NFC). Statistical response surface models indicated that the bleaching behavior of the ozone-treated pulp could be represented by second-order polynomial equations. These non-linear optimization models predict cost savings of 62.2%, 73.4%, and 63.3% for producing viscose, NCC, and NFC pulp grades, respectively.

scholarly journals Dissolving Pulp From Eucalyptus Sawdust For Regenerated Cellulose Products

2021 ◽  
Author(s):  
Graciela Viviana Olmos ◽  
María Claudia Taleb ◽  
Fernando Esteban Felissia ◽  
Nanci Vanesa Ehman ◽  
Maria Soledad Peresin ◽  
...  
Keyword(s):  
Raw Materials ◽  
Degree Of Polymerization ◽  
Dissolving Pulp ◽  
Regenerated Cellulose ◽  
Cellulose Content ◽  
Cellulose Carbamate ◽  
Soda Pulping ◽  
Dissolving Pulps ◽  
Regenerated Cellulose Films ◽  
Eucalyptus Sawdust

Abstract This study assesses the possibility of obtaining regenerated cellulose products (beads and films) from eucalyptus sawdust dissolving pulps produced by non-conventional processes, compared with a commercial dissolving pulp as a reference. Eucalyptus sawdust dissolving pulps were obtained by soda pulping followed by two different TCF sequential bleaching processes OOpZ and OOp (where O is oxygen, Op is oxygen reinforced with hydrogen peroxide, and Z is ozone), followed by a cold soda extraction. The characterization of dissolving pulps involved alpha-, beta- and gamma-cellulose content, alkali solubility with 10 wt% (S10), and 18 wt% NaOH (S18) aqueous solutions, and degree of polymerization. Fock´s method was used to measure cellulose reactivity and the alkali solubility in a 9 wt% NaOH aqueous solution at -5 °C to evaluate the pulps dissolving capacity. Dissolving pulps presented high cellulose content (> 93 %, expressed as a-cellulose) and good reactivity (almost 84 %). The dissolving pulps were adequate raw materials for regenerated cellulose products (beads and films) from two cellulose dissolution methods: direct dissolution in NaOH/urea and cellulose carbamate solution. The sequence OOpE (where E is an alkaline extraction) was determined to be a more economically feasible and straightforward process to produce dissolving pulp than OOpZE. The experimental pulps showed the expected characteristics of the dissolving pulp to obtain regenerated cellulose products. However, it is necessary to deepen the study of producing regenerated cellulose films with enhanced mechanical properties from experimental dissolving pulps, solvents, coagulation, and regeneration conditions.

scholarly journals Chemometric Optimisation of a Copper Sulphide Tailings Flocculation Process in the Presence of Clays

Minerals ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 582 ◽  
Author(s):  
Claudia Castillo ◽  
Christian F. Ihle ◽  
Ricardo I. Jeldres
Keyword(s):  
Settling Rate ◽  
Mixing Conditions ◽  
Fine Content ◽  
Operational Conditions ◽  
Coarse Aggregates ◽  
Series Of Experiments ◽  
Sulphide Tailings ◽  
Solids Content ◽  
Two Stages ◽  
Flocculation Process

The presence of fine and ultra-fine gangue minerals in flotation plants can contribute to sub-optimal valuable ore recovery and incomplete water recycling from thickeners, with the performance of the latter equipment relying on adequate flocculation. In order to study the dependence of the flocculation process on the suspension-flocculant mixing conditions, a series of experiments—chosen using chemometric analysis—were carried out by varying mixing conditions, solid concentration, water salinity and flocculant dosage. To this purpose, two different tailings (both featuring coarse and fine content) were considered and a response surface methodology based on a Doehlert experimental design was used. The results suggest that the operational conditions to optimise the flocculated tailings settling rate and the suspended solids that report to a thickener overflow are not necessarily the same. This is a reasonable outcome, given that the settling rate depends on the coarse aggregates generated in the slurry, while the overflow solids content is governed both by either fine particle content (and its characteristics) or small aggregates. It is inferred that to maximise dewatering performance two stages should be involved—a separate treatment of the thickener overflow to remove fine content and thickening at optimal flocculant dosage to enhance this process.

scholarly journals Influence of Input Variables over the Wood Digestion in a Sulfite Pulp Mill for Biorefinery Purposes

2015 ◽  
Vol 6 (2) ◽  
pp. 160
Author(s):  
Cristina Rueda ◽  
Carlos Tejedor ◽  
Natalia Quijorna ◽  
Ana Andrés ◽  
Alberto Coz
Keyword(s):  
Pulp Mill ◽  
Raw Material ◽  
Pulp Yield ◽  
Cellulose Content ◽  
Digestion Process ◽  
Sulfite Pulp ◽  
Input Variables ◽  
Major Attention ◽  
Wood Digestion ◽  
Better Than

Eucalyptus globulus is the most profitable specie in Europe for pulping. However, in recent years some diseases and pests have caused its defoliation, affecting the available quantity of wood. In this sense, the mills are studying how to avoid the loss of pulp yield as well as the optimization of byproducts in order to take advantage of every component present in the wood using biorefinery processes. One of the possible options is to complete the consumption of E. globulus with other species such as Eucalyptus nitens.The objective of this paper is to study the behavior of both species related to the dissolving pulp manufacturing process as well as the characteristics of the resulting products. Parameters that can be very useful for the evaluation of the raw material, such as the growing data or density of both species, have been compared. Major attention has been focused on the composition of both species and how it affects the characteristics of the possible final products.E. nitens presents good results of forestry characteristics, being better than E. globulus in terms of growing and resistance to frosts. The cellulose content of both species is similar, however the digestion process in the case of E. nitens needs to be improved in order to optimize the involved energy and the obtained products.

Totally Chlorine Free Bleaching of Eucalyptus globulus Dissolving Pulps Delignified with Peroxyformic Acid and Formic Acid

Holzforschung ◽  
2002 ◽  
Vol 56 (1) ◽  
pp. 60-66 ◽  
Author(s):  
S. Abad ◽  
B. Saake ◽  
J. Puls ◽  
J. C. Parajó
Keyword(s):  
Hydrogen Peroxide ◽  
Formic Acid ◽  
Eucalyptus Globulus ◽  
Molar Mass ◽  
Oxygen Delignification ◽  
Operational Conditions ◽  
Bleached Pulp ◽  
Target Values ◽  
Dissolving Pulps ◽  
Peroxyformic Acid

Summary Eucalyptus globulus wood samples were delignified in two-stage treatments carried out in media made up of formic acid, water and hydrogen peroxide under selected operational conditions. The pulps were subjected to Totally Chlorine Free (TCF) bleaching sequences. Alkaline treatments, oxygen delignification, ozone stages and treatments with peroxyacids were assayed in order to reach the target values for dissolving pulps. Under the best conditions, a fully bleached pulp (91.6% ISO brightness) with SCAN viscosity of 649 ml/g and favourable molar mass distribution was obtained.

scholarly journals Ultralight-Weight Cellulose Aerogels from NBnMO-Stabilized Lyocell Dopes

2007 ◽  
Vol 2007 ◽  
pp. 1-4 ◽  
Author(s):  
Falk Liebner ◽  
Antje Potthast ◽  
Thomas Rosenau ◽  
Emmerich Haimer ◽  
Martin Wendland
Keyword(s):  
Carbon Dioxide ◽  
Solid State ◽  
Solution Structure ◽  
Supercritical Drying ◽  
Regenerated Cellulose ◽  
Cellulose Content ◽  
Solvent Exchange ◽  
New Materials ◽  
Specific Density ◽  
Regeneration Procedure

Cellulose aerogels are intriguing new materials produced by supercritical drying of regenerated cellulose obtained by solvent exchange of solid Lyocell moldings. FromN-methylmorpholine-N-oxide solutions with cellulose contents between 1 and 12%, dimensionally stable cellulose bodies are produced, in which the solution structure of the cellulose is largely preserved and transferred into the solid state. The specific density and surface of the obtained aerogels range from 0.05 to 0.26 g/cm3and from 172 to 284m2/g, respectively, depending on the cellulose content of the Lyocell dopes and regeneration procedure. A reliable extraction and drying procedure using supercritical carbon dioxide, the advantageous use of NBnMO as stabilizer for the Lyocell dopes, and selected physical properties of the materials is communicated.

scholarly journals Influence of Oil Content on Solution Load Ethanol-Soda Delignification of Oil Palm Mesocarp Fiber

2018 ◽  
Vol 13 (2) ◽  
pp. 200-208
Author(s):  
Taharuddin Taharuddin ◽  
Dewi Agustina Iryani ◽  
Megananda Eka Wahyu
Keyword(s):  
Palm Oil ◽  
Oil Palm ◽  
Industrial Waste ◽  
Room Temperature ◽  
Oil Content ◽  
Oil Extraction ◽  
Ethanol Solution ◽  
Cellulose Content ◽  
The Difference ◽  
Two Stages

Mesocarp fiber palm oil industrial waste can be processed into pulp, but this fiber still contains oil with varying levels. The difference oil content in fiber affects the amount of cooking solution required to make mesocarp waste into pulp. This study consists of two stages, namely the pretreatment stage of oil extraction to obtain variations in oil content in the mesocarp fiber waste and the delignification stage using the NaOH-ethanol solution with the ratio of solids:solvent is varied to 1: 8, 1:10 and 1:12. Oil content of the fiber was analyzed, it is consist of 9,5% oil. To vary the oil content, the fibers are soaked in ethanol at room temperature and the levels drop to 7%. And soaking at 40°C can lower the oil content drop to 2%. The obtained pulp had the largest cellulose content 50.77% from delignified product from fiber with 7.6% oil content and solids:solvent ratio: 1:10. While the lowest lignin that was 7.39% obtained at 2.5% oil content. In the delignification process with ratio 1:12, pulp produced is decreased in cellulose content and from FTIR results it is known that it occurs because of the degraded cellulose during the delignification process.

scholarly journals MULTILATERATION UNDER FLIP AMBIGUITY FOR UAV POSITIONING USING ULTRAWIDE-BAND

2020 ◽  
Vol V-1-2020 ◽  
pp. 317-323 ◽  
Author(s):  
K. Park ◽  
J. Kang ◽  
Z. Arjmandi ◽  
M. Shahbazi ◽  
G. Sohn
Keyword(s):  
Unmanned Aerial Vehicles ◽  
Linear Optimization ◽  
Position Estimation ◽  
Recursive Least Squares ◽  
Algebraic Solution ◽  
Planar Surface ◽  
Positioning Accuracy ◽  
Operational Conditions ◽  
Aerial Vehicles ◽  
Symmetric Reflection

Abstract. Ultrawide-band (UWB) ranging technology and multilateration techniques have recently been emerging solutions for positioning unmanned aerial vehicles (UAVs) in GNSS-denied environments. This solution offers cm-level ranging accuracy and considerable robustness to multipath receptions. UWB modules are commonly used in an anchor-based configuration; i.e., one UWB tag is mounted on the UAV, and several UWB anchors are installed on the ground. In real-world operational conditions, anchors can form a planar or a near-planar surface. This causes a geometric ambiguity, called flip ambiguity, in position estimation. Flip ambiguity can lead to considerable errors in the estimated position by multilateration. In this paper, we present a multilateration approach, which automatically resolves the flip ambiguity for UAV-positioning using UWB ranging. The proposed multilateration method first computes an algebraic solution through recursive least squares. If the initially estimated position is found to be flipped, then it is corrected by a symmetric reflection with respect to the anchor plane. Finally, the estimated position is refined by non-linear optimization. Extensive experiments in a real environment show that the proposed algorithm can effectively tackle the issue of flip ambiguity in multilateration, leading to a significant improvement in positioning accuracy.

scholarly journals The Value Of Information Sharing In Capacity Allocation In Serial Service Operations

2016 ◽  
Vol 32 (5) ◽  
pp. 1459
Author(s):  
Jin Kyung Kwak
Keyword(s):  
Information Sharing ◽  
Value Of Information ◽  
Cost Savings ◽  
Service Operations ◽  
Capacity Allocation ◽  
Previous Period ◽  
Waiting Cost ◽  
Two Stages ◽  
The Cost ◽  
Number Of Customers

In this study, we investigate the value of information sharing in serial service operations. When services are offered sequentially in two stages, we may use the demand information from the previous period in assigning servers at each stage. This study compares an information-based policy with a basic policy for capacity allocation in serial service operations in order to explore the value of information shared between the two stages. Among several possible candidates for an information-based policy, we chose an assigning rule such that the number of servers at the latter stage is determined by the number of customers served out of the prior stage in the previous period. On the other hand, the basic policy is designated as an assigning rule such that the two stages have the same constant number of servers through all periods. Assuming independent and identically distributed Normal demands with various parameters, we conducted computational experiments to compute the cost savings from using the information-based policy over the basic policy. The cost of using each policy includes the labor cost and the waiting cost. The results show that the cost savings of information sharing are relatively low and that the value of information sharing increases with demand variability or with unit waiting cost. These results give us some managerial insights on capacity allocation in serial service operations. 

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