Patent ID: 6144897
Filing Date: 2000-11-07
Classification: B01J,C08F,G05B,Y02P

Abstract:
A control method for synthesis of at least one chemical product in an apparatus comprising at least one reactor (R), in which one or more manipulated variables (GC) is allowed to act on the course of the process in order to make one or more controlled variables (GR) related to the properties of the product and/or to the course of the process, equal to corresponding set points (C.sub.GR), said method comprising:(a) inputting set points concerning the controlled variables (C.sub.GR);(b) computing, by means of a prediction unit (OP), predictions of the controlled variables (P.sub.GR), based on measurements of the process manipulated variables (M.sub.GC);(c) using a control unit (OC) to compute the set points of the process manipulated variables (C.sub.GC), based on the set points (C.sub.GR) and the predictions (P.sub.GR) of the controlled variables;(d) transmitting the set points of the process manipulated variables (C.sub.GC) to actuators, in order to act on the course of the process;wherein the prediction unit (OP) is based on a mathematical model of the process (M); and wherein the prediction unit (OP) is designed in such a way that the mass M.sub.XR of at least one constituent (X) in the reactor (R) is predicted by the equation:M.sub.XR =LAG(F.sub.XRin .multidot..tau..sub.X, .tau..sub.x)in which:F.sub.XRin is the mass flow rate of the constituent X entering the reactor R;.tau..sub.X is the residence time of X in the reactor, the value of which i s.tau..sub.X =M.sub.XR /(.SIGMA.Fxdis)in which:M.sub.XR denotes the last calculated value of the mass of the constituent X present in the reactor R;.SIGMA. Fxdis denotes the sum of all the mass flow rates Fxdis at which the constituent X disappears from the reactor R, including by reaction and/or by leaving the reactor;the function y=LAG (u, .tau.) is the solution of the differential equation ##EQU12## calculated with the instantaneous value of u and of .tau., and with the last calculated value of y.