Home  About us  Contact
 

Paper Machines (paper + machines)

Distribution by Scientific Domains
Chemistry75%

Selected Abstracts

Hierarchical multivariate analysis of cockle phenomena

JOURNAL OF CHEMOMETRICS, Issue 10 2003
Zdravko I. Stefanov
Abstract The phenomena called cockle are small wrinkles on the paper surface that appear during paper production. This condition poses significant economic and operability problems in the production of magazine paper, as it deteriorates the printabilty of the paper. There are many and varied sources that can lead to cockle, and their detection is often very complicated. In this work a multivariate hierarchical approach is proposed to analyze the cause of cockle. The hierarchy has two levels, the first of which is a three-way decomposition and analysis of the data collected from sections of a paper machine. The second level is a two-way decomposition and analysis between the combined loadings from the three-way decomposition and the measured cockle data. The results show that this approach is capable of identifying the important process sections and process variables, in spite of the large dimensionality of the problem. Data analyzed from two real industrial paper machines, involving several grades of paper, are used to demonstrate the proposed hierarchical approach. Copyright © 2003 John Wiley & Sons, Ltd. [source]

Technical efficiency and embodied technical change in the Indonesian pulp and paper industry

JOURNAL OF INTERNATIONAL DEVELOPMENT, Issue 2 2006
Michiel Van Dijk
Abstract In this paper the dynamics of technological change and technical efficiency in the Indonesian pulp and paper industry are analysed. The industry is characterised by rapid growth of output and capacity, with some mills investing heavily in state-of-the-art machinery after 1984. Using stochastic frontier analysis, we distinguish between technological advances of best practice mills and the rate of technological inefficiency. We use a newly constructed micro-level dataset describing the complete population of Indonesian paper mills and paper machines from 1975 to 1997. We find an increasing divergence in technical efficiency over time, indicating that most plants have been not able to keep up with the technological leaders in the industry. Several of the plants operating the latest technologies have lower levels of efficiency than mills operating more outdated equipment. These outcomes qualify the common understanding of dualistic economic structures in developing countries, composed of less efficient traditional and more efficient modern capital intensive establishments. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Dynamic simulation and control of a paper machine wet end

THE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 2 2001
Eddy F. Yap
Abstract A good simulation model for paper machines can be used to identify deficiencies in the design, bottlenecks during operation, and regions of poor control. It also allows users to test their hypotheses and innovations without potentially causing major upsets and reducing throughput. In this work, a dynamic model of the wet end system has been developed using the IDEASTM platform, describing the distribution of fines, fillers and fibres throughout the system. The model was then tested at steady state with mill data for the low-ash and high-ash production grades, and the results show that over 70% of the predicted values had only 5% deviation. The dynamic simulation was also used to show that the retention aid controller would react in the wrong direction due to changes in the wire pit consistency and the stock ratio would cause major changes in stream compositions and consistencies of the wet end. Un bon modèle de simulation des presses de papier peut en effet ,tre utile pour déterminer les failles dans la conception, les goulots d'éranglement en cours d'opération et les régions mal régulées. De m,me, il permet aux utilisateurs de tester leurs hypothèses et innovations sans risquer de causer des problèmes majeurs ou de réquire la capacité. Dans ce travail, un modèle dynamique du système à fraction humide a été mis au point à l'aide de la plate-forme IDEASTM, décrivant la distribution des fines, des agents de remplissage et des fibres dans le système. Ce modèle a ensuite été testé à l'état permanent avec les données d'une papeterie pour des qualités de papier à faibles et fortes teneurs en cendres et les résultats montrent que plus de 70% des valeurs prédites n'avaient qu'un écart de 5%. La simultation dynamique a montré que le régulateur d'aide à la rétention réagirait dans la mauvaise direction à cause de changements dans la consistance sur la toile et que le taux d'approvisionnement entra,nerait d'importants changements dans les compositions et consistances des courants de la fraction humide. [source]

Cross-directional Estimation and Predictive Control of Paper Machines Using DWT

ASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 1-2 2001
Zhihuan Song
This paper proposes a novel approach for cross-directional (CD) estimation, modeling and control on paper machines based on discrete wavelet transforms (DWT). The CD basis weight variations are approximated at various resolutions using wavelet multiresolution analysis (WMRA). The controllable component of CD variations can be extracted from the original samples by choosing a suitable threshold resolution. An acceptable response model describing the relationship between the settings of the slice-screws to the basis weight profile is obtained. The controller synthesis, model prediction, optimization and parameter estimation are all performed in the DWT domain. The size of optimization and control problems associated with such large dimensions can be significantly reduced. [source]