Quantitative Influence of Thermal Value of Coal on Steam Parameters of Thermal Power Units

Against the backdrop of frequent and variable coal quality in current coal-fired power units, effectively understanding the impact of coal calorific value on the operating parameters of thermal power units is of great guiding significance for peak shaving and rapid load changing operation of thermal power units. Based on the mass and energy balance equations of the boiler, and combined with the theory of differential deviation, a mathematical model was constructed to quantify the impact of changes in the calorific value of coal on the operating parameters of the unit. This model was used to study the quantitative effects of changes in calorific value on the main reheat steam parameters of thermal power units and the extraction port parameters of high-pressure heaters in steam turbines. The research results indicate that as the calorific value increases, the flow rate, pressure, and temperature of the main reheated steam also increase. Due to the influence of heat storage in the high-pressure cylinder and its reheated steam pipeline, the degree of change in reheated steam parameters is lower than that of the main steam. For every 1000 kJ/kg increase in calorific value, the main reheat steam flow rate increases by 98.6 t/h and 81.2 t/h respectively, and the average main steam pressure and temperature increase by 1.63 MPa and 5.21 °C. In addition, due to the influence of the relative internal efficiency of the high-pressure cylinder of the steam turbine, the pressure and temperature changes of each extraction port of the high-pressure heater show significant differences with the load. The research work has certain theoretical guidance significance for the operation and adjustment of thermal power units.