Global control of a nonisothermal CSTR using a moving model

✍ Scribed by Wen-Teng Wu; Jing-Jy Cheng

• Publisher: Elsevier Science
• Year: 1986
• Tongue: English
• Weight: 386 KB
• Volume: 41
• Category: Article
• ISSN: 0009-2509
• DOI: 10.1016/0009-2509(86)80031-8

✦ Synopsis

of a multivariable nonlinear continuous stirred tank reactor (CSTR) via a moving model is presented. Both cooling and heating media are used to manipulate the concentration and the temperature. The system can be operated around an unstable steady-state or across a separatrlx from a low-temperature point to a high-temperature steady state. INTRODUCHON Continuous stirred tank reactors (CSTRs) are frequently used in the chemical process industry. A rigorous analysis of CSTR dynamic behaviour has been carried out [l, 23. On the other hand, most control studies have used linearized models, Global control of a nonisothermal CSTR is seldom considered. Optimal control theory provides a procedure for synthesizing a multivariable controller. A quadratic performance index for linear feedback control is frequently considered [3,4]. The solution to this optimal control problem usually requires the solution of a set of equations with a two-point boundary value. This solution, however. is impractical for on-line optimal control. In the present study, a moving model [S, 63 is used to describe CSTRs in which an exothermic reaction takes place. The control law is determined by the use of a quadratic performance index and a moving model. Hence, a method for global control of a CSTR is developed. It is possible to control the system from a far-away point to a desired steady-state. The steadystate may be a stable steady-state or an unstable one. THE SYSTEM The control system is a nonisothermal CSTR. The reaction in the reactor is a first-order one. The material and heat balance for the CSTR can be written as [7]: Vg = q (cf-c) -Vk, ceeElR7 (1) uz. Kh 4c -