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 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 diverse combustion modes and load-switching processes. Without any control, step changes in coal fuel have the highest impact on flue gas, followed by natural gas fuel and feedwater. In terms of individual regulation, 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 lean-fuel combustion mode decreases by 43.7% compared to rich-fuel combustion mode, demonstrating the regulation potential in power grid fluctuations. As for coordinated regulation, overall plant load ramp rates in rich-fuel combustion modes without and with coal ramp feed are 11.6 and 15.2%/min, up to 3.2-4.2 times higher than those of traditional plants. Meanwhile, carbon emissions are reduced by 8.5%-25.9%, further confirming the viability of flexible upgrading and carbon reduction in fossil-fuelled power systems.