Numerical-and-Experimental Substantiation of Deep Unloading of an E-420-13.8-560GM Boiler

One of the main characteristics of the maneuverability of power equipment is whether the load may be reduced to the minimum allowable level. The ability of power equipment to operate in a variable regime (with unloading during night time) enables it to participate in the control of frequency and power in the power system. It is important to note that low-load operation of the equipment should not make its performance poorer. In particular, for drum boilers, the required steam conditions and reliable circulation of the working fluid in the evaporation waterwalls should be maintained in the entire operating load range. The numerical-and-experimental studies have substantiated the possibility to reduce the minimum allowable steam load of a typical E-420-13.8-560GM boiler from 210 to 150 t/h. According to the results of thermal design calculations by the Boiler-Designer code, the required steam superheat temperature (560°С) cannot be attained at lower loads. Field tests of an operating boiler have revealed that difficulties with fuel flow control and failures of the furnace’s combustion process arise at loads below 150 t/h. Calculations and experimental measurements performed using flow measuring tubes installed in the furnace waterwalls have demonstrated that the fluid circulation of a fluid in the evaporation water walls remains even on a load decrease to 110 t/h. It is pointed out that more than 100 E-420-13.8-560GM boilers, whose design was modified during long-term operation (for more than 40 years), are operating now. Therefore, the minimum steam load should be finalized only after additional studies for each boiler of this type.