Introduction  Before the project implementation, it is required to pre-evaluate the degree of flexible operation of coal-fired power plants, including the prediction of the technical index of boiler minimum combustion stable load rate. Since the existing experience and algorithms cannot meet the flexibility evaluation requirements of power plants, it is necessary to draw up a new semi-empirical calculation curve of the boiler minimum combustion stable load rate in combination with the performance index that the current equipment can achieve.

  Method  Based on the literature data and engineering experience, the parameters with strong correlation with stable combustion index were selected, and statistical and regression methods were used to fit the semi-empirical calculation curve.

  Result  With V_daf (volatile matter of coal) and φ (total output margin coefficient of the burner) as independent variables, combined with the statistical analysis value of minimum ignition energy, the theoretical index of boiler minimum combustion stable load rate can be obtained.

  Conclusion  The new calculation curve takes the known parameters available from the engineering data and can accurately calculate the theoretical value of boiler minimum combustion stable load rate under different conditions, which is consistent with the actual operation test data and can be used as tool for engineering design.