Dynamic assessment of 1000 MW ultra-supercritical coal-fired power flexibility retrofitting through lean- and rich-fuel integrated gas turbine

Development of renewable energy imposes high flexibility requirements on fossil-fuelled power generation systems for power grid's stability and security. This study proposes novel flexibility retrofitting on the ultra-supercritical coal-fired power plants through integrated gas turbine, enhancing the abilities for fuel ramp rate modulation and primary frequency-regulation power generation. Dynamic assessments of the integrated system are performed to investigate time-dependent variations of working fluid and flue gas under the diverse combustion modes and load-switching processes. Without control, the step changes in coal fuel have the highest impact on the flue gas, followed by the natural gas fuel and the feedwater. In terms of individual regulation, the lean-fuel combustion mode has minor impacts on the steam temperature, flue gas adiabatic temperature, flue gas composition and furnace pressure. The oscillation time of the integrated system in the lean-fuel combustion mode decreases by 43.7 % compared to rich-fuel combustion mode, demonstrating the regulation potential during power grid fluctuations. For coordinated regulation, the overall plant load ramp rates in the rich-fuel combustion modes without and with the coal ramp feed are 11.6 and 15.2 %/min, up to 3.2–4.2 times higher than those of the traditional plants. Meanwhile, the carbon emissions are reduced by 8.5%–25.9 %, further confirming the viability of flexible upgrading and carbon reduction in the fossil-fuelled power systems.