Otimização e controle de secadores convectivos tipo túnel. Estudo de caso: secagem de tijolos cerâmicos vazados.

Abstract

Controlling and optimizing the drying process of ceramic bricks is essential to guarantee the quality of the product, avoid waste and energy waste, promoting a lower environmental impact, as well as lower production costs and more safety in the process. The present work aims to study the control of the drying process of ceramic brick cast in a cross-flow dryer using the PID controller. It was proposed a mathematical modeling for the drying phenomenon based on the mass and energy balances written for a differential volume located in an arbitrary position of the solid layer. The PID controller modeling was proposed from the classical control laws. To obtain the numerical solution of the governing equations of the drying phenomenon, the finite volume method was used in an explicit formulation and the "upwind" scheme was used as a function of interpolation for the convective terms. The tuning of the controller parameters was done by trial and error. The methodology was used to describe both the drying process of hollow ceramic bricks with industrial dimensions and the control of the dryer with real dimensions in different operating conditions, as well as the tuning of control parameters. Results of the influence of the parameters on the drying process and time, as well as the moisture content and temperature of the product, absolute humidity, relative humidity and air temperature throughout the bed, are presented, analyzed and discussed at different times. It has been found that drying at moderate relative humidity and temperatures generates good post-drying product. As for the parameters, it was verified that the parameter related to the term of the derivative is very sensitive, since for small variations the dynamic response varies greatly.