Extremum seeking control for the catalytic oxidation of ammonia in non-stationary conditions

Abstract

The paper is devoted to the problem of automatic control of ammonia catalytic oxidation providing the maximum extent of conversion in the non-stationary conditions of nitric acid production. The analysis of the effect of proportion oxygen content and ammonia in ammoniac-air mix, its temperatures and speed on the oxidation process is made. It was established that the nature of this influence on extent of conversion is both extreme and cross. The adjustable parameters of the process were accepted as the extent of conversion and the temperature in the of contact oxidation zone. In the research of the system, the fluctuations of oxygen content in air and fluctuations of actual air volume were selected as the changing external influences at the contact device. The analysis of the conventional isothermal model of ideal replacement was made to prove its adequacy to the real catalytic oxidation of ammonia. The expediency of the experimental model of this process has been successfully tested. On the basis of a passive experiment, the regression model of the oxidation process has been built, and an inspection of its statistical reliability was made by means of multiple determination indexes using the Fischer’s criterion with five-percent significance value of a zero hypothesis. The structure of a multilevel control system has been developed, and a two-coordinate discrete controller was designed providing both the extremum search and the deduction of a conversion extent. The results of imitating simulation of the developed system confirm the efficiency of the selected method of extreme control.