Internal interconnections impact on control performance in a thermomechanical pulping process

Process integration may indeed be advantageous, particularly in a plant-wide economical sense, but there is also a potential risk that unnecessary difficulties are introduced when it comes to process control. This work identified several internal interconnections in a thermomechanical pulp refiner line as a result of an integration approach adopted during the process design. Firstly, a disturbance sensitivity analysis for the overall production process is carried out. Secondly, a simulation model is constructed and using real process data it is found to successfully reflect the complex dynamic behavior observed at the actual plant. The simulation model can provide indications on how the process performance can be improved by process design modifications. The results suggest that the presence of internal interconnections increases the demands on the control system and also set limits for its performance. If control aspects had been considered at the earliest stages of process development, the possibility to achieve satisfactory process performance could have been significantly improved.

[1]  Paul Stuart,et al.  Controllability analysis of a TMP-newsprint refining process , 2006 .

[2]  Anders Karlström,et al.  Refining models for control purposes , 2008 .

[3]  W. Luyben.  Dynamics and control of recycle systems. 2. Comparison of alternative process designs , 1993 .

[4]  A. Karnis,et al.  The effect of control variables on refining zone conditions and pulp properties , 1991 .

[5]  Karin Eriksson.  An Entropy-based Modeling Approach to Internally Interconnected TMP Refining Processes , 2005 .

[6]  K.J. Astrom,et al.  Wood chip refiner control , 1988, IEEE Control Systems Magazine.

[7]  Hartmut Logemann,et al.  Multivariable feedback design : J. M. Maciejowski , 1991, Autom..

[8]  W. Luyben.  Dynamics and control of recycle systems. 3. Alternative process designs in a ternary system , 1993 .

[9]  Ricardo Femat,et al.  Temperature oscillations in a biological reactor with recycle , 2004 .

[10]  W. Luyben.  Dynamics and control of recycle systems. 1. Simple open-loop and closed-loop systems , 1993 .

[11]  Hong Cui Carlemalm.  Studies on controllability of integrated process systems , 2003 .

[12]  Ram Lavie,et al.  Dynamics of plants with recycle , 1982 .

[13]  Ian Postlethwaite,et al.  Multivariable Feedback Control: Analysis and Design , 1996 .

[14]  Sigurd Skogestad,et al.  Dynamic behaviour of integrated plants , 1996 .

[15]  Sebastian Engell,et al.  Dynamics and Control of a Process with Recycle Streams , 1997 .

[16]  J. Hill,et al.  On the control of chip refining systems , 1993 .

[17]  William L. Luyben.  Chapter A1 - The need for simultaneous design education , 2004 .

[18]  Karin Eriksson.  Towards Improved Control of TMP Refining Processes , 2009 .