scholarly journals On the modeling of pulp properties in CTMP processes

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Fredrik Bengtsson ◽  
Anders Karlström ◽  
Torsten Wik
Keyword(s):  
Specific Energy ◽  
Fiber Length ◽  
Linear Models ◽  
Internal Variables ◽  
Process Conditions ◽  
Residence Times ◽  
Normal Process ◽  
Soft Sensors ◽  
Pulp Properties ◽  
Flat Zone

Abstract The goal of this paper is to model the pulp properties fiber length, shives width and freeness. This will be done utilizing specific energy, flat zone inlet consistency and the internal variables, consistencies and fiber residence times estimated from refining zone soft sensors. The models are designed using more than 3600 hours of data from a RGP82CD refiner. The pulp properties are sampled using a measurement device positioned after the latency chest. Such measurements are noisy and irregularly sampled which opens for a number of challenges to overcome in modeling procedures. In this paper it is shown that the models for shives width and fiber length are capable of predicting most of the major dynamics. However, for freeness no reliable linear models can be derived. When estimating fiber length, the specific energy together with flat zone inlet consistency, fiber residence times and the consistency in the conical zone were the dominant inputs. For shives width it was found that a similar set of inputs resulted in the best models, except that the consistencies during normal process conditions did not significantly influence shives width. Furthermore, fiber residence times were shown to have considerably more pronounced impact on fiber length compared with shives width estimates.

scholarly journals TMP properties and refiner conditions in a CD82 chip refiner at different operation points. Part II: Comparison of the five tests

2018 ◽  
Vol 33 (1) ◽  
pp. 82-94
Author(s):  
Rita Ferritsius ◽  
Olof Ferritsius ◽  
Jan Hill ◽  
Anders Karlström ◽  
Karin Eriksson
Keyword(s):  
Specific Energy ◽  
Specific Energy Consumption ◽  
Optimal Operation ◽  
Operating Conditions ◽  
Process Conditions ◽  
Residence Times ◽  
Entropy Model ◽  
Refining Zone ◽  
Tensile Index ◽  
Pulp Properties

Abstract This paper is part two of a study on a CD 82 TMP chip refiner where relations between changes in the process conditions and changes in the properties of the produced pulp are investigated. Focus is on the ratio between tensile index and specific energy consumption when results from five tests are compared. Pulp properties were measured for composite pulp samples taken from the refiner blow line. Residence times and pulp consistencies were estimated by use of the extended entropy model. Clearly, an increase in specific energy does not necessarily implicate an increase in strength properties of the pulp produced. It is of high importance to have access to information about the refining zone conditions when searching for an optimal operation point in terms of the ratio between tensile index and specific energy. In these tests, this ratio had a maximum at about 55 % measured blow line consistency. Unfavourable operating conditions were identified at high pulp consistencies, especially after the FZ, where pulp consistencies well above 70 % were observed. The estimated residence time for each refining zone responded differently when applying changes in production rate, plate gaps and dilution water flow rates. In conclusion, the results associated with estimated pulp consistencies where easier to interpret compared with results for residence times, implying that additional tests are required for the latter variable. In addition to tensile index, pulp properties like freeness, Somerville shives and light scattering coefficient were included in the analysis.

Fiber energy efficiency Part I: Extended entropy model

2014 ◽  
Vol 29 (2) ◽  
pp. 322-331 ◽  
Author(s):  
Anders Karlström ◽  
Karin Eriksson
Keyword(s):  
Energy Efficiency ◽  
Temperature Profile ◽  
Dynamic Models ◽  
Fluid Dynamic ◽  
Multiscale Model ◽  
Process Conditions ◽  
Entropy Model ◽  
Refining Zone ◽  
Energy Balances ◽  
Flat Zone

Abstract This is the first in a series of papers presenting the development of a comprehensive multiscale model with focus on fiber energy efficiency in thermo mechanical pulp processes. The fiber energy efficiency is related to the defibration and fibrillation work obtained when fibers and fiber bundles interact with the refining bars. The fiber energy efficiency differs from the total refining energy efficiency which includes the thermodynamical work as well. Extracting defibration and fibrillation work along the radius in the refining zone gives information valuable for fiber development studies.Models for this process must handle physical variables as well as machine specific parameters at different scales. To span the material and energy balances, spatial measurements from the refining zone must be available. In this paper, measurements of temperature profile and plate gaps from a full-scale CD-refiner are considered as model inputs together with a number of process variables. This enables the distributed consistency in the refining zone as well as the split of the total work between the flat zone and the CD-zone to be derived. As the temperature profile and the plate gap are available in the flat zone and the CD-zone at different process conditions it is also shown that the distributed pulp dynamic viscosity can be obtained. This is normally unknown in refining processes but certainly useful for all fluid dynamic models describing the bar-to-fiber interactions. Finally, it is shown that the inclusion of the machine parameters will be vital to get good estimates of the refining conditions and especially the split between the thermodynamical work and the defibration/fibrillation work.

scholarly journals TMP properties and refining conditions in a CD82 chip refiner. Part I: Step changes of process variables, description of the tests

2018 ◽  
Vol 33 (1) ◽  
pp. 69-81
Author(s):  
Rita Ferritsius ◽  
Olof Ferritsius ◽  
Jan Hill ◽  
Anders Karlström ◽  
Karin Eriksson
Keyword(s):  
Specific Energy Consumption ◽  
Fibre Length ◽  
Thermomechanical Pulp ◽  
Process Variables ◽  
Negative Effects ◽  
Entropy Model ◽  
Tensile Index ◽  
Pulp Consistency ◽  
Pulp Properties ◽  
Flat Zone

Abstract The study explores how changes in process variables, residence time and pulp consistency in refining influence the pulp properties. The equipment utilized in this study was a conical disc chip refiner (RGP82CD) producing thermomechanical pulp (TMP). The focus was on the ratio between tensile index and specific energy consumption. Pulp properties were measured for composite pulp samples taken from the refiner blow line. Residence times and pulp consistencies were estimated by use of the extended entropy model. This showed that the CD-refiner, with the flat and conical refining zone, has a process performance similar to that of a two-stage refiner set-up, and that the consistency in both refining zones is of high importance. Comparing different periods revealed that even if the values of measured blow line consistency are similar, significant differences in the estimated consistency in the flat zone can prevail. Therefore, only monitoring blow line consistency is not enough. Specifically, it was found that the pulp consistency after the flat zone could be very high, considerably higher than in the blow line, and this could have negative effects on tensile index and fibre length.

Effect of the initial fiber alignment on the mechanical properties for GMT composite materials

2017 ◽  
Vol 31 (1) ◽  
pp. 91-109 ◽  
Author(s):  
Yuyang Song ◽  
Umesh Gandhi ◽  
Adam Koziel ◽  
Srikar Vallury ◽  
Anthony Yang
Keyword(s):  
Mechanical Properties ◽  
Fiber Orientation ◽  
Fiber Length ◽  
Initial Conditions ◽  
Length Distribution ◽  
Material Model ◽  
Bending Test ◽  
Process Conditions ◽  
Fiber Concentration ◽  
Finished Part

A glass-mat-reinforced thermoplastic (GMT) material is widely used in the automotive industry for components such as underbody shields, seat structures, front/rear bumper, and front-end modulus. Due to the higher residual length of the glass strands, GMT usually offers better mechanical properties than injection-molded fiber-reinforced thermoplastics. The GMT material is typically manufactured by compression molding (CM) of preimpregnated fibers–reinforced resin sheets called mat. Two types of mats, one with discontinuous random (RD) fibers and other with aligned continuous fibers, are considered in this study. A stack of such mats with different combinations is used to tailor the mechanical properties of the final part. During the CM, the fibers in the mat flow with the resin and change the alignment. In this study, we are presenting an approach to account for the initial condition, such as fiber length, orientation and concentration of the fibers in the mat, and process conditions used, to develop a material model for the finished part. First, a stack of mat with known fiber orientation, length, and concentration as initial conditions is simulated for CM to predict the fiber orientation in the finished part. Next, the material model for the finished parts is developed using a Mori–Tanaka homogenization approach. The fiber orientation in the finished part is mapped from the CM simulation. For the fiber concentration and fiber length distribution, we used an empirical approach. The cross section of the finished part is investigated under optical microscope, and the fiber length and concentration are estimated based on the microstructure and initial stacking of mats. The predicted fiber orientation tensor is verified with orientations measured using computerized tomography (CT) scan on actual parts. The material model is verified by comparing the predicted performance with the actual tensile and bending test results.

scholarly journals MECHANICAL PULPING.Effect of long fibre concentration on low consistency refining of mechanical pulp

2012 ◽  
Vol 27 (4) ◽  
pp. 702-706 ◽  
Author(s):  
Stefan Anderssou ◽  
Christer Sandberg ◽  
Per Engstrand
Keyword(s):  
Energy Consumption ◽  
Specific Energy ◽  
Specific Energy Consumption ◽  
Fibre Length ◽  
Pilot Scale ◽  
Process Conditions ◽  
Mechanical Pulp ◽  
Fibre Concentration ◽  
Fibre Network ◽  
Length Reduction

Abstract The aim of this study was to investigate the influence of lang fibre concentration on Ioadability and pulp properties during LC refming of mechanical pulp. Lang fibre concentration was adjusted to three different Ievels by screen fractionation of the pulp. The three pulps were refined in a single disc pilot scale LC refiner at simi1ar process conditions. Increased lang fibre concentration suppmied a larger refiner gap and resulted in less fibre . cutting at a given specific energy consumption. The higher lang fibre concentration probably contributed to a stronger fibre network that maintained a !arger refining gap at certain specific energy consumption. Increased long fibre concentration also enabled a higher tensile index increase in the LC refmer at certain fibre length reduction. The study supports a process combining LC refining with screen fractionation, where the lang fibre fraction is recycled to the refiner feed. This enables a . higher Ioadability and a more effective utilisation of the LC refiner. By using this technology, overall specific energy consumption can be reduced if a !arger share of the refining is performed in LC rather than HC refining.

scholarly journals On the modeling of tensile index from larger data sets

2019 ◽  
Vol 34 (3) ◽  
pp. 289-303 ◽  
Author(s):  
Anders Karlström ◽  
Lars Johansson ◽  
Jan Hill
Keyword(s):  
Laboratory Data ◽  
Internal Variables ◽  
Process Conditions ◽  
Data Sets ◽  
Process Data ◽  
Tensile Index ◽  
Specific Operating Condition ◽  
Secured Data ◽  
Operating Points ◽  
Handsheet Properties

Abstract The objective of this study is to analyze and foresee potential outliers in pulp and handsheet properties for larger data sets. The method is divided into two parts comprising a generalized Extreme Studentized Deviate (ESD) procedure for laboratory data followed by an analysis of the findings using a multivariable model based on internal variables (i. e. process variables like consistency and fiber residence time inside the refiner) as predictors. The process data used in this has been obtained from CD-82 refiners and from a laboratory test program perspective, the test series were extensive. In the procedure more than 290 samples were analyzed to get a stable outlier detection. Note, this set was obtained from pulp at one specific operating condition. When comparing such “secured data sets” with process data it is shown that an extended procedure must be performed to get data sets which cover different operating points. Here 100 pulp samples at different process conditions were analyzed. It is shown that only about 60 percent of all tensile index measurements were accepted in the procedure which indicates the need to oversample when performing extensive trials to get reliable pulp and handsheet properties in TMP and CTMP processes.

Nitrate estimation in the denitrifying post-filtration unit of a municipal wastewater treatment plant: the Viikinmäki case

2012 ◽  
Vol 65 (8) ◽  
pp. 1521-1529 ◽  
Author(s):  
M. Mulas ◽  
F. Corona ◽  
H. Haimi ◽  
L. Sundell ◽  
M. Heinonen ◽  
...  
Keyword(s):  
Wastewater Treatment ◽  
Wastewater Treatment Plant ◽  
Municipal Wastewater ◽  
Linear Models ◽  
Treatment Plant ◽  
Municipal Wastewater Treatment ◽  
Soft Sensors ◽  
Intrinsic Nonlinearity ◽  
On Line ◽  
Filtration Unit

In this work we present and discuss the design of an array of soft-sensors to estimate the nitrate concentration in the denitrifying post-filtration unit at the Viikinmäki wastewater treatment plant in Helsinki (Finland). The developed sensors aim at supporting the existing hardware analyzers by providing a reliable back-up system in case of malfunction of the instruments. In the attempt to design easy to implement and interpretable sensors, computationally light linear models have been considered. However, due to the intrinsic nonlinearity of the process, also nonlinear but still computationally affordable models have been considered for comparison. The experimental results demonstrate the potential of the developed soft-sensors and the possibility for an on-line implementation in the plant's control system as alternative monitoring devices.

scholarly journals Low consistency refining of mechanical pulp — system design

TAPPI Journal ◽  
2017 ◽  
Vol 16 (7) ◽  
pp. 419-429 ◽  
Author(s):  
CHRISTER SANDBERG ◽  
JAN-ERIK BERG ◽  
PER ENGSTRAND
Keyword(s):  
Energy Efficiency ◽  
Specific Energy ◽  
Energy Efficient ◽  
Fiber Length ◽  
Specific Energy Consumption ◽  
Main Line ◽  
Thermomechanical Pulp ◽  
Line Production ◽  
Tensile Index ◽  
Printing Papers

Many mechanical pulping mills use low consistency (LC) refining for energy efficient fiber development. In this study, energy efficiency and pulp quality were evaluated for six processes, of which four included LC refining. We studied two different types of chip refiners – single disc (SD) and double disc (DD) – with LC refining in the main and reject lines. All process combinations have been used in the Holmen Paper Braviken mill, Sweden, to make thermomechanical pulp for printing papers. LC refining was more energy efficient than high consistency (HC) refining at certain tensile index increases in all evaluated combinations. LC refining in the main line had somewhat higher energy efficiency than did LC refining in the reject line. The type of chip refiner (DD or SD) did not affect the efficiency or pulp property development in LC refining. The process with a combination of DD chip refining and LC refining had the highest energy efficiency (tensile index at certain specific energy consumption). All processes with LC refining produced pulp with somewhat lower light scattering and fiber length than did the corresponding system with only HC refining. Thus, for printing papers, the best combination was LC refining with DD chip refining. LC refiners seem to have a narrow range in specific energy for maximum energy efficiency and a good balance between tensile index increase and fiber length reduction. Much higher specific energy was applied on reject pulp. However, the reject share was only around 30%. The LC refining specific energy, based on main line production, was around 80 kWh/air-dried metric ton (a.d. metric ton), whereas up to 180 kWh/a.d. metric ton was applied in main line.

scholarly journals Theoretical considerations on the factors influencing the processing of hemp stalks

2020 ◽  
Vol 180 ◽  
pp. 03005
Author(s):  
Paul Găgeanu ◽  
Mihai Olan ◽  
Iuliana Găgeanu ◽  
Alexandru Zaica
Keyword(s):  
Specific Energy ◽  
Fiber Length ◽  
High Performance ◽  
Agricultural Products ◽  
Technical Equipment ◽  
Functional Characteristics ◽  
Factors Influencing ◽  
Functional Factors ◽  
Theoretical Considerations ◽  
Over Time

The present work is achieved based on the processing of the data accumulated over time, within the activity of research, technological engineering, and testing of machines for processing agricultural products in the last years, as well as studying the specialized literature with the latest achievements of some companies that make machinery for processing agricultural products. The compression of the hemp stalks for processing is analyzed, the main characteristics of the working rolls, the specific energy consumed are determined and an analysis of the obtained fiber length is performed. In order to develop a technical equipment for processing hemp stalks that ensures high performance, the following aspects were studied: the constructive and functional factors of a technical equipment that influence the working processes in order to choose a performance solution for processing hemp stalks. In the last part of the paper, the main technical and functional characteristics of a high-performance technical equipment for processing the hemp stalks harvested in green are established.

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