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Thesis for the Degree of Licentiate of Technology

 

Year 1995
Marja Määttä

Study of Simulation of Deinking Process


ABSTRACT-The objective of the work was to study, with the aid of simulation, the relative advantages of alternative processes for designing a deinking plant, and to review production planning, process control and cost implications.

First, the simulators used in the paper industry were examined in a literature survey. Next, the reasons for using recycled fibre and the effects of recycling on the properties of paper were examined. Finally, the handling of recycled fibre was examined stage by stage, from slushing to bleaching.

The deinking plant at Kaipola was selected as the industrial simulation process. Massbal MK II was selected as the simulation tool, because this program has an established position in paper industry simulations.

Dissolved solids, solids, ash contents, flows, outputs and consistencies were selected for closer study. Consistency, waste paper daily tonnage and temperature were used as input data for the waste paper. The cleaning of 330 tons of waste was studied. Consistencies and reject consistencies. and pulp inlet consistency ratios, i.e. reject ratios, were used as input data for different subprocesses. Chemical flows and the steam infeed in connection with dispersion were excluded from the study.

Particular emphasis was given to studying the influence of reject ratios on yield. To this end, two different simulations were performed, using the same waste paper volume, but different consistencies and reject ratios.

The first simulation revealed the importance of using as accurate input data as possible to ensure a successful simulation. The fourth-stage cleaning and the DLR stage cleaning had to be excluded from the simulation.

In the second simulation, the screen after the pulper was replaced by a high-consistency cleaner and the pulper dilution water was taken from the cloudy filtrate tank.

The work revealed the great importance of the right equipment, reject ratios and consistencies for the yield of the deinking plant.


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