Paper quality controls by utilizing new consistency measurement capabilities: both optical and microwave techniques provide good results
The main idea in headbox total consistency control is to reduce the time delay in controlling consistency disturbances in the headbox. Normally, disturbances in headbox consistency are measured as disturbances in basis weight. When headbox consistency is measured, the transport delay from headbox to...
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Published in | Pulp & paper Canada Vol. 99; no. 7; p. 50 |
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Main Authors | , , , |
Format | Magazine Article |
Language | English |
Published |
Westmount
Annex Publishing & Printing, Inc
01.07.1998
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Subjects | |
Online Access | Get full text |
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Summary: | The main idea in headbox total consistency control is to reduce the time delay in controlling consistency disturbances in the headbox. Normally, disturbances in headbox consistency are measured as disturbances in basis weight. When headbox consistency is measured, the transport delay from headbox to dry end disappears and disturbances can be eliminated more quickly. When the consistency and the volume flow deviate from the setpoints mentioned above, they get the values Cs[Symbol Not Transcribed]=[Symbol Not Transcribed]Cs and q[Symbol Not Transcribed]+snot;q, where [Symbol Not Transcribed]Cs and [Symbol Not Transcribed]q are deviations from the setpoints of consistency and flow, respectively. The fibre flow gets the value (Cs[Symbol Not Transcribed]+[Symbol Not Transcribed]Cs)[Symbol Not Transcribed](q[Symbol Not Transcribed]+[Symbol Not Transcribed]q). The fibre flow should be kept equal to the steady-state value, i.e. Based on the results of this research, it is possible to improve paper quality by consistency controls. The feedforward control of thick stock total consistency can prevent thick stock consistency variations from disturbing the short circulation, while whitewater total consistency control and headbox ash consistency control contribute to the stability of the short circulation. Feedforward of thick stock ash content will be tested in the near future, and further research is still needed on measuring headbox consistency. |
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ISSN: | 0316-4004 1923-3515 |