Dynamic performance and control strategy modification for coal-fired power unit under coal quality variation

The variation in feeding coal quality is a major issue during coal-fired power unit operation because it causes output power fluctuation, increase in heat losses, and operation safety risks. Given this situation, the effect of coal quality variation on power plant performance should be explored to improve the control strategy considering coal quality variation. In this study, dynamic models of coal-fired power plants are developed. Results show that the unit efficiency decreases when the coal quality worsens, and the carbon, ash, and moisture contents in coal are dominant factors. Dynamic processes with coal quality variation are simulated, and overtemperature risks, deviation of output power, and additional energy consumption are evaluated. Then, the modification of control strategy is proposed to enhance the coal-fired power unit performance, which adds coal quality variation into the water–fuel ratio calculation. With the modified control logic, the duration of the dynamic process is reduced by approximately 40%, and the fluctuation amplitudes of the live and reheat steam temperatures are decreased by approximately 90% and 60%, respectively. In addition, the additional energy consumption is diminished.