9th September 2010 17:07
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Solution to runnability problems in papermaking
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Problem Statement
In paper making web breaks cause loss of production and a large broke system binds capital. |
Improvement Approach
Runnability problems often come from variation in key process parameters, which will be monitored and the cause-symptom relationships revealed by means of mathematical process diagnostics. |
Benefits
Reduction in web breaks directly improves the productivity and the payback time is typically a few months. |
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Company Contact Information
KCL
KCL, P.O.Box 70, FIN-02151 Espoo, Finland
Tel.
+358 (0)9 4371 491, Fax. +358 (0)9 464 305
E-mail
isko.kajanto@kcl.fi
www.kcl.fi
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A typical problem in paper making is poor runnability, which emerges as web breaks. Web breaks can be avoided by e.g. using more chemical pulp in wood-containing paper grades, or using more softwood fibre in fine paper. These remedies are non-optimal, because they increase cost and make the product quality poorer. |
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The on-line data of the paper making process is analysed using KCL-WEDGE software. If needed, additional sensors describing the chemical state of the process are installed. Typically extra pH, temparature, conductivity and charge analyser are used. Depending on the paper grade, also a Ca-probe and air-content probe can be installed.
The advantage with the approach is that mostly existing and readily available data is used. On-line measurements also provide information about fast changes in the process state, which is not possible with off-line analysis. Using remote data connections, much of the analysis work can be done remotely from KCL.
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Typical findings in a process analysis include improper operational practices, which again are a result of not undertanding the process dynamics properly. Some examples are temperature or pH variations in the stock, strong and uncontrolled variations in dosing of paper chemicals and incorrect tuning of automatic controllers. Often the faults can thus be corrected without investments, and the payback time is especially short. In the best cases the process analysis has resulted in savings of hundreds of thousands of euros within months, thus giving a payback time of a few weeks. Also the product quality improves because of less process variability. |
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