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Journal articles
Open Access
The laboratory twin-former part 1: design and performance, TAPPI JOURNAL, October 2000, Vol. 83(10)

The laboratory twin-former part 1: design and performance, TAPPI JOURNAL, October 2000, Vol. 83(10)

Journal articles
Open Access
Developments in activity generation on fourdriniers, TAPPI JOURNAL, October 2000, Vol. 83(10)

Developments in activity generation on fourdriniers, TAPPI JOURNAL, October 2000, Vol. 83(10)

Journal articles
Open Access
An inside view on impulse drying phenomena by modelling, TAPPI JOURNAL, October 2000, Vol. 83(10)

An inside view on impulse drying phenomena by modelling, TAPPI JOURNAL, October 2000, Vol. 83(10)

Journal articles
Open Access
Paper surface makeup process observed by ultrasound, TAPPI JOURNAL, October 2000, Vol. 83(10)

Paper surface makeup process observed by ultrasound, TAPPI JOURNAL, October 2000, Vol. 83(10)

Journal articles
Open Access
Impulse drying of board grades; pilot production trials, TAPPI JOURNAL, September 2000, Vol. 83(9)

Impulse drying of board grades; pilot production trials, TAPPI JOURNAL, September 2000, Vol. 83(9)

Journal articles
Open Access
Computational modelling of paper drying machines, TAPPI JOURNAL, September 2000, Vol. 83(9)

Computational modelling of paper drying machines, TAPPI JOURNAL, September 2000, Vol. 83(9)

Journal articles
Open Access
Qualification of welding procedures for duplex stainless steels, TAPPI JOURNAL, September 2000, Vol. 83(9)

Qualification of welding procedures for duplex stainless steels, TAPPI JOURNAL, September 2000, Vol. 83(9)

Journal articles
Open Access
Effect of entrained air on the performance of a pressure screen, TAPPI JOURNAL, September 2000, Vol. 83(9)

Effect of entrained air on the performance of a pressure screen, TAPPI JOURNAL, September 2000, Vol. 83(9)

Journal articles
Magazine articles
Open Access
Flocculation of fiber suspensions studied by Rheo-OCT, TAPPI Journal September 2024

ABSTRACT: When dealing with papermaking fiber suspensions, particle flocculation takes place even before the paper web is formed. The particle flocculation depends on several aspects, including particle mass concentration (consistency), particle collisions, electrochemical interactions promoted by chemical additives, etc. Due to its importance, fiber suspension flocculation has been studied for a long time in papermaking, and several methods have been developed for this purpose. The traditional techniques include, for example, focused beam reflectance microscopy (FBRM) and high-speed video imaging (HSVI). Recently, a new optical method, optical coherence tomography (OCT), has emerged for flocculation analysis. The advantages of OCT are the possibility to study opaque suspensions, its micron-llevel resolution, and its high data acquisition speed. The OCT measurements can be combined with rheological (Rheo) measurements, allowing simultaneous measurement of both the time evolution of the floc size and the suspension viscosity. In this work, we used this approach, Rheo-OCT, to study the flocculation of suspensions of various papermaking furnishes. We analyzed the time evolution of the floc size and the fiber suspension viscosity when the studied papermaking suspensions were treated with highly refined furnish (HRF) — a furnish that contained a significant amount of micofibrillated cellulose (MFC)-type fibrils — and/or chemical additives. Such studies can lead to a better understanding of the impact of flocculation on the produced paper web in terms of qualities like formation, drainage potential, and strength behavior.

Journal articles
Magazine articles
Open Access
Control of continuous digester kappa number using generalized model predictive control, TAPPI Journal September 2024

ABSTRACT: Kappa number variability at the digester impacts pulp yield, physical strength properties, and lignin content for downstream delignification processing. Regulation of the digester kappa number is therefore of great importance to the pulp and paper industry. In this work, an industrial application of model-based predictive control (MPC), based on generalized prediction control, was developed for kappa number feedback control and applied to a dual vessel continuous digester located in Western Canada. The problem was complicated by the need to apply heat at multiple locations in the cook. In this study, the problem was reduced from a multiple to a single input system by identifying three potential single variable permutations for temperature adjustment. In the end, a coordinated approach to the heaters was adopted. The process was perturbed and modeled as a simple first order plus dead time model and implemented in generalized predictive control (GPC). The GPC was then configured to be equivalent to Dahlin’s controller, which reduced tuning parameterization to a single closed loop time constant. The controller was then tuned based on robustness towards a worst-case dead time mismatch of 50%. The control held the mean value of the kappa number close to the setpoint, and a 40% reduction in the kappa number’s standard deviation was achieved. Different kappa number trials were run, and the average fiberline yield for each period was evaluated. Trial results suggested yield gains of 0.3%•0.5% were possible for each 1 kappa number target increase.

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