Stabilizing operation of a solar aided power generation (SAPG) plant by adjusting the burners’ tilt and attemperation flows in the boiler

Abstract

Solar Aided Power Generation (SAPG) technology has been proved to be one of the most efficient ways to integrate solar energy into a coal-fired power plant. However, previous studies on SAPG systems have mainly focused on their design and design optimization. There are few studies on their operation. In an SAPG plant, solar heat is used to replace the extracted steam to preheat feedwater. However, the introduction of solar energy inevitably affects the steam flow rate through the boiler, especially when the SAPG plant is in fuel-saving operation mode, thus affecting the boiler's operation. Namely, the steam parameters at the boiler outlets would change with various solar inputs if no control mechanism were applied. A mechanism for adjusting the burners' tilt and attemperation flows in the boiler is therefore proposed in this study, in order to stabilize the temperature of the steam at the outlet of the boiler. To simulate the effectiveness of the mechanism, a transient model of the SAPG plant, including a series of modules for key components in the plant, has been developed in this study. The simulation results in a case study of a 300 MWe SAPG plant, showing the proportion of heat that was absorbed in the boiler was redistributed due to the solar input, without adjusting the burners' tilt and attemperation flows, resulting in temperature drops of superheated/reheated steam when in a fuel-saving mode. However, the simulation in the case study also shows that by swinging the burner tilt angle up to 22.7° and adjusting the attemperation flows in the super-heaters and re-heaters in the boiler, the superheated/reheated steam temperature can be restored from 523 °C and 510 °C respectively back to 543.0 °C, the desired temperature.