Abstract:

Mill management is often faced with difficult questions
such as determining the effects of changes in processing variables
on subsequent quality. Generally these questions can
be answered, but often the time required to obtain sufficient
data to evaluate the results is prohibitive. Simulation
has been shown to be of value in quickly answering these types
of questions when a model is available which describes the
process under study. This thesis makes available a mathematical
model of the washing operation.
In developing this model of washing, appropriate
equations were written and tested for accuracy, and then a
simulation of changes in the process variables was performed
to observe their effects on final concentration. The procedure
used to model the washing operation was to first write
equations to explain a onebox washer. Then with certain
modifications the onebox washer model was expanded to a
fourbox model. All variables were separated into their
individual components and equation writing ended when the
last variables introduced could not be defined in terms of
other variables.
After the equations were written, the model was tested
for accuracy with mill data. The onebox model appeared to be reasonably accurate, but sufficient data to test the
fourbox model were unavailable. Until the data can be
obtained for complete validation of the fourbox model,
several experiments will have to be performed by the
individual mills employing this model to adapt it to their
particular operation. However, assuming that the model
closely resembles an actual washing operation, the simulation
will give an indication of the results that a mill would
expect to obtain. Future work devoted to fuller understanding
of the proportionality factors will ultimately allow
use of the model for multiple wash~rs without preliminary
plant experiments.
