Search system of fuel combustion control in industrial furnaces

There are several existing methods of decreasing specific consumptions of heat energy in the process of billets heating in industrial furnaces before rolling or heat treatment. One of available methods, which give a real decreasing of fuel consumption, is improvement of the fuel combustion process control in the heating furnaces working space. At present, there is a vast majority of control systems of fuel combustion process designed according to the scheme of volumetric proportioning gas and air consumption and implemented by using stabilization of their balance. This control process is not effective enough if the furnace operating conditions are unsteady. The dependence between the rational value of air consumption and the fuel consumption is nonlinearity and exposed to the action of various uncontrollable disturbances. One of the parameters, which make possible evaluation of the fuel combustion quality, is the flame temperature or heating furnace working space temperature. It was specified that the dependence between the flame temperature and the air consumption had an extremal form. It was proposed to use a search system of automated optimization (SAO), which would allow determining and maintaining the gas and air balance for maximum heating output of fuel combustion. The paper presents a practical double-loop configuration for the search system of the gas and air balance control. The first control loop provides a rapid identification of rational air consumption within the working space, where a safe fuel combustion is possible. The second control loop determines an optimum balance between gas and air for maximum flame temperature under the current conditions. An experimental appraisal of the system for optimization of fuel combustion in industrial furnaces of the sheet rolling mill has shown that decreasing of specific fuel consumption for heating billets is from 5.6%.