SYSTEM OF AUTOMATIC CONTROL OF THE OIL HEATING PROCESS IN THE WAY HEATER

Abstract

Oil (gas) is preheated in inline heaters with an intermediate heat carrier before being supplied to consumers or the pipeline network to reduce oil viscosity or prevent hydrate formation caused by pressure reduction.

The article addresses the problem of synthesizing a cascaded system where the primary channel is "fuel gas flow rate – oil temperature at the heater outlet," and the auxiliary channel is "fuel gas flow rate – flue gas temperature."

The control system synthesis problem was solved based on a linearized mathematical model, the analysis of which showed that the transfer function of such a system is of the nineteenth order. Such a high order of the transfer function makes it impossible to synthesize the system using a generalized quadratic criterion. Therefore, using the Hankel method and the area method, reduced transfer functions were obtained for the main and auxiliary control system channels. This allowed reducing the order of the control error transfer function relative to the main regulator's target to the sixth order.

The synthesized control system structure includes a PI-controller (main loop) and a P-controller (auxiliary loop). The task of calculating the PI and P controller tuning parameters was formulated as a nonlinear programming problem with a generalized quadratic criterion and constraints arising from the stability of the control system. Using software developed in the MatLab environment, the PI and P controller tuning parameters were calculated, and the quality of the control process for the thermal regime of the inline heater with an intermediate heat carrier was assessed.