| 1. |
- Ander, Paul, et al.
(författare)
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Differences between Scots pine and Norway spruce TMP pulps as revealed bt the HCL method
- 2009
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Ingår i: SPCI meddelande / The Swedish Association of Pulp and Paper Engineers. - 0280-6800. ; , s. 322-324
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Konferensbidrag (refereegranskat)abstract
- The HCl method was used to compare pine and spruce TMP pulps. Delignification gave much stronger fibre cleavage by HCl (3.5-5x for Stage 3) indicating that lignin and hemicelluloses protect the fibres from acid attack. Cleavage per fibre for TMP was similar as kraft pulps, while spruce TMP was more sensitive to HCl than pine TMP. A more robust secondary wall and a lower number of dislocations and weak points may be related to the higher refining energy needed for pine TMP pulps
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| 2. |
- Daniel, Geoffrey, et al.
(författare)
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Energy consumption in refining of Scots pine and Norway spruce TMP is governed by fibre morphology and ultrastructure
- 2009
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Ingår i: SPCI meddelande / The Swedish Association of Pulp and Paper Engineers. - 0280-6800. ; , s. 82-86
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Konferensbidrag (refereegranskat)abstract
- Studies on the different behaviour of Scots pine and Norway spruce during thermomechanical pulping were conducted to find reasons for explaining the greater energy consumption of pine. Well characterized wood samples from clear-cut trees and thinnings were used in pilot scale trials to produce highly characterized pulps. Structural and topochemical differences found between pine and spruce likely to have a strong negative impact on energy included: i) presence of a greater proportion of latewood fibres in pine annual rings with thick secondary cell walls and concomitant reduced fibre collapsibility; ii) ultrastructural differences in the location of fractures at the fibre secondary wall level during primary refining with pine showing greater resistance to refining although it defibrated easier than spruce; iii) that fibre separation and fibre development were sequential processes in pine and not concurrent as in spruce; and iv) the greater amounts of extractives in pine and their redistribution onto the surfaces of fibres and fines during processing
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| 3. |
- Ericsson, Stefan, et al.
(författare)
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Implementation of an on-line detection procedure for oscillating control loops
- 2002
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Ingår i: Proceedings : control systems 2002 (SPCI-meddelande ; 76). - 0280-6800.
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Konferensbidrag (refereegranskat)abstract
- This paper describes a method for online supervision of control loops that automatically detects oscillations in the loops. The paper describes the method, its implementation in a Honeywell TDC3000 system, and experiences obtained from its use in the mill AssiDomän Frövi.
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| 4. |
- Petersson, Mikael, et al.
(författare)
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Control Structure Assessment in an Industrial Control System
- 2002
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Ingår i: Proceedings : control systems 2002, june 3-5 2002, Stockholm, Sweden : The world pulp and paper week 2002 (SPCI-meddelande ; 76). - 0280-6800. ; 76
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Konferensbidrag (refereegranskat)abstract
- This paper describes the implementation of a structure assessmentmethod in an industrial control system. The method uses available signals to evaluate if a given signal can be used for additional feed forward control action to improve the performance of a control loop.
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| 5. |
- Slätteke, Ola, et al.
(författare)
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On identification and control tuning of cylinder dryers
- 2002
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Ingår i: Proceedings : control systems 2002, june 3-5 2002, Stockholm, Sweden : The world pulp and paper week 2002 (SPCI-meddelande ; 76). - 0280-6800. ; , s. 298-302
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Konferensbidrag (refereegranskat)abstract
- The steam pressure control loops in the drying section of a paper machine play an important role for the quality of the moisture content control. The steam pressure loops are essential for the effective use of advanced control schemes for the moisture control. From mathematical model building and experiments on industrial paper machines it is found that the dynamics from the steam valves to the steam pressure can be described by a simple process model, the so called IPZ model. This model has an integrator, one pole, and one zero. The process is characterised by three parameters that vary significantly with the operating conditions. A typical step response of the open loop process has a fast and a slow transient. The steam pressure in the cylinders is in general controlled by PI-controllers. Some previous work on this subject has been done by Nelson and Gardner.The paper discusses the specifications for control of the IPZ process. Different controller structures are discussed and general tuning rules for the IPZ process are derived. It is shown that the tuning should be based on a compromise between reference signal tracking and disturbance attenuation. The disturbance attenuation is essential to avoid coupling between the different steam groups.An important property of the tuning rules is that it is possible to determine the controller parameters based on quite simple experiments on the process. The new tuning rules are compared with the common practice of making lambda-tuning based on the fast dynamic of the process.The main results of the paper are a controller structure for steam pressure control and a set of tuning rules for the controller. The tuning rules have been tested on paper machines in the industry.
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| 6. |
- Stenström, Stig, et al.
(författare)
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Productivity increase from a better understanding of dynamic processes and control of the paper dryer
- 2002
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Ingår i: Proceedings / 7th International Conference on New Available Technologies (SPCI-meddelande ; 75). - 0280-6800. ; , s. 70-73
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Konferensbidrag (refereegranskat)abstract
- The development of simulation models describing the process dynamics and tuning of the control systems for the multi-cylinder dryer section is presented. This includes models and controls of the condensate system, the sheet moisture content at the reel as well as moisture gradients in the thickness direction of the sheet.
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