| Summary: | In this thesis, mathematical models for the process units of a chemi-thermomechanical pulping
(CTMP) plant have been developed. The models were developed based on first principles and
empirical modelling approaches. The models have been used to simulate the dynamic behavior
of a CTMP plant. A CTMP plant is composed of four major processes: the chip pretreatment
process, the refining process, the pulp processing process, and finally the bleaching process. A mill
audit was performed to study the chip quality variations along the chip pretreatment process and
typical variations were used for the simulation of a CTMP plant. The refining process was modelled
based on the concept of specific energy and refining intensity. The model was used to predict pulp
properties and handsheet properties from the refiner operating conditions. Data from mill trials and
literature were compared with the prediction and there was good agreement between predicted and
measured values. The effects of reject rate on fibre fractionation, freeness, and consistency through the
screens were investigated and models were developed. In modelling the bleaching process, a kinetic
model was used to relate the final pulp brightness to the hydrogen peroxide charge, temperature, and
retention time. The flow pattern of the pulp stock in the bleaching tower was studied and modelled as
a combination of continuous stirred tank reactors and a plug flow reactor. The dynamic simulations
revealed the impact of the major disturbances and operating conditions on the performance of the
whole pulping process. Control strategies have been proposed and tested for the bleaching plant. This
work has systematically studied the dynamics of a CTMP plant and brought a thorough understanding
of the dynamic behavior of the plant. The models developed in this work can be used as a tool for
process modification, process operation, and process control. === Applied Science, Faculty of === Chemical and Biological Engineering, Department of === Graduate
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