Estructura de control jerárquico aplicada a un reactor de amoniaco, tipo tubular, con enfriamiento intermedio
A hierarchic control structure applied to an ammonia tubular reactor with cold shot cooling
J. García1, G. Fernández–Anaya2*, F.D. Vargas–Villamil1 y E. Orduña1
1 Matemáticas Aplicadas y Computación, Instituto Mexicano del Petróleo Eje Central Lázaro Cárdenas 152, México, D.F. 07330
2 Depto. de Física y Matemáticas, Universidad Iberoamericana, Prolongación Paseo de la Reforma 880, Col. Lomas de Santa Fe, México, D. F. 01210. *Autor para la correspondencia. E–mail: guillermo.fernandez@uia.mx
]]>Recibido 31 de Mayo 2010.
Aceptado 18 de Agosto 2010.
Resumen
Las estructuras de control jerárquicas son útiles en procesos altamente integrados puesto que descomponen un sistema complejo en varios subsistemas que pueden tener diferentes objetivos (e.g. estabilización, desempeño, optimización) o escalas de tiempo. En este trabajo se propone una estructura jerárquica para el control de un reactor de amoniaco con enfriamiento intermedio que es altamente no lineal y está fuertemente acoplado. El sistema de control jerárquico tiene tres niveles. El primer nivel está compuesto de controladores tipo PI y su principal objetivo es la estabilización. El segundo nivel está compuesto de un consolador interpolante que provee la temperatura de referencia para el control de la primera cama del reactor. Su objetivo es ampliar el rango de operación del controlador y por lo tanto mejorar el desempeño. El tercer nivel está compuesto de un optimizador cuyo objetivo es maximizar la producción de amoniaco. Los resultados muestran que la estructura jerárquica permite tener un control robusto y estable en un amplio rango de operación, manteniendo las salidas de control en su valor de referencia y rechazando las perturbaciones.
Palabras clave: estructura jerárquica, control interpolante, control en cascada, camas de catalizador.
Abstract
Hierarchical control fractures eire useful in highly integrated processes, since they decompose a complex system in various subsystems, which may have different objectives (e.g. stabilization, performance, optimization) or scales of time. In this work, a hierarchical straciure ior the control of an ammonia reactor with cold–shot cooling, which is highly nonlinear and strongly coupled, is proposed. This hierarchical control system has three levels. The first level is composed of PI type controllers, and its main objective is stabilization. The second level is composed of an interpolated controller that provides the reference temperature for the control of the first bed of the reactor. Its objective is to extend the operating range of the controller and therefore, "to improve the performance. The Third level is composed of an optimizer whose objective is to maximize the ammonia production. The results show that the hierarchical structure results in a robust and stable controller in a large operating range, keeping the control outputs on its reference while rejecting the disturbances.
]]> Keywords: structure, interpolate controller, cascade controller, catalyst beds.
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