Modeling and calculation of a multi-cascade temperature control system for a tube furnace

In the context of rising energy prices and stricter environmental requirements, enterprises strive to minimize energy consumption without compromising product quality and productivity. Reducing fuel gas consumption in production processes plays a key role in increasing economic efficiency and reducing negative environmental impacts. The most significant consumers of fuel gas are the energy sector, the processing industry and oil refining. For oil refining processes, tubular furnaces are often used, designed to heat raw materials to the required temperature. The introduction of more advanced automated control systems for heating raw materials in a tubular furnace will significantly reduce costs, increase energy efficiency and reduce emissions of pollutants. To increase control efficiency, a multi-stage system for automatic temperature control at the outlet of a tubular furnace is proposed. The consumption of fuel gas supplied to the burners and the temperature of the flue gases at the boundary of the radiant and convective chambers of the furnace are used as auxiliary adjustable parameters. A mathematical model of a multistage automatic control system for a tubular furnace is proposed. The tuning parameters of the regulators of a multistage system are calculated based on the Ziegler-Nichols method, taking into account the mutual influence of the regulator parameters. Transients in control and disturbing effects in single-circuit, traditional two-stage and three-stage systems are considered. A comparative analysis of the characteristics of the transient process of single-circuit, two-stage and three-stage automatic control systems is carried out. It is shown that the use of the proposed multi-stage structure of the control system will optimize the operation and improve the quality of control of tubular furnaces, as well as similar technological facilities with significant transport and capacitive delays with high inertia. The practical implementation of multi-stage systems is carried out on the basis of standard functional blocks of PID control of industrial controllers, which expands the application of the proposed approach.