(42h) Validation of an Exergy Analisys Using Aspen PLUS for the Methanol/Water System – a Case of Study

Between all industrial separation processes, the distillation is one of
the largest energy consumers. So is justified the search for methods of energy
optimization for distillation columns. The optimization of parameters such feed
stage, thermal condition of the feed, use of intermediate reboilers can be
obtained analysing the exergy profile
of the column, which in turn depends on the determination of consistent thermodynamic
properties of all feeds inside the collumn. This work aims to analyze and
validate a determination of the exergy
loss profile along a distillation column using the software Aspen Plus for the binary system
Methanol / Water with a rigorous design method, comparing the simulation
results with the results obtained by Faria
in his doctoral thesis (Unicamp - 1996) applying the appropriate
thermodynamic models and performing the material and energy balances for each
stage of the column, then identifying models that result in consistent exergy balances for the column. The
results show that appropriate models allow to obtain consistent balances of exergy only in a limited set of cases,
and then, to correct this, it is necessary to use models that consider the the
values of enthalpy ​​and entropy with excess. The validation of the
method allowed us to search optimized operational conditions for the
distillation column, which aims to minimize the exergy loss in each separation stage and makes it more efficient
thermodynamically.