Dissertação
Implementação de uma estrutura de controle indireto da concentração de etanol em uma coluna de destilação híbrida
Fecha
2013-01-31Registro en:
GEHLEN, Cindi de Oliveira. IMPLEMENTATION OF A INDIRECT CONTROL STRUTURE OF THE
ETHANOL COMPOSITION CONTROL IN A HYBRID DISTILLATION
COLUMN. 2013. 109 f. Dissertação (Mestrado em Engenharia) - Universidade Federal de Santa Maria, Santa Maria, 2013.
Autor
Gehlen, Cindi de Oliveira
Institución
Resumen
The unit operation of distillation demands the largest amount of energy in the ethanol
separation. It is of utmost interest to minimize the energy expended in the process,
playing the control an important role on this task. Here a Proportional-Integral-
Derivative (PID) controller is proposed to ensure the fuel ethanol composition at
desired value, i. e., above 92,5°INPM as the same time as save energy through the
minimal use of reboiler power. It is well known that the composition analyzers are
expensive and have a high response time. Due to such limitation, we have developed
an inference model in which the product composition is inferred from the product
temperature and thermodynamics relations, enabling the monitoring and the indirect
control a posteriori of this variable. In addition, the inference of composition allows
defining the reference value of product temperature which ensures the fuel ethanol
production at desired composition. The chosen control structure takes into account
the reference value of product temperature as set-point of a SISO (Single Input
Single Output) controller, i. e., the product ethanol composition is indirectly
controlled by the direct control of product temperature. The control design depends
on a good dynamic model between the manipulated variable (reboiler power) and the
controlled variable (product temperature). Such relationship was obtained by process
data identification with discrete parametric models, being Output Error and ARMAX
the models with the best performance. Several tuning methods were compared for the
controller design. Among these methods, the Internal Model Control (IMC) has
presented the best relationship between robustness and performance to be used in the
distillation process of this study. Finally, the proposed controller was validated in the
process and the results have shown its good performance to obtain the product
composition at desired value. Thus, we can conclude that the proposed controller,
through the simple PID control strategy, performed as expected within the limitations
of available instrumentation and the process particularities.