This work presents a model-based approach to systematically
derive
optimal operating policies for an existing industrial-scale tunnel
dryer. The primary focus of the study is to control the shrinkage
stage, during which product fracture risk is highest, with the minimum
energy cost possible. First, the steady-state dryer operation is optimized
with the attained operating policy resulting in 1.5% fuel economy,
while assuring product quality. The dryer operation is then optimized
at transient state, investigating two case studies, with the derived
optimization results being thoroughly compared with those attained
when no control actions are taken. The first case considers a 9.57%
increase in dryer productivity. It is demonstrated that the derived
operating policy guarantees a well-controlled drying process, with
the minimum extra fuel consumption being about 7.7%. The second case
study considers the coexistence of two different raw clay-based ceramics
in the dryer. Once again, the optimal operating scheme assures the
final product quality, but with a minimum thermal energy consumption
increase of 3.4%.