Against the background of carbon peak and carbon neutrality goals

improving the efficiency and promoting the carbon reduction retrofit of coal-fired power plant are critical tasks for construction of the new-type electric power system in China. In this study

an efficient and low-carbon power generation system based on staged combustion of natural gas and coal is proposed. By directly introducing the high-temperature exhaust from the gas turbine into the coal-fired boiler for combustion

the system saves high-grade chemical energy of raw coal

while reducing total flue gas emissions and enriching the CO2 concentration in flue gas. Results show that the coal consumption of the coal-fired power plant decreases by 17.01%

and the CO2 emission rate decreases by 19.55%. Furthermore

compared with the conventional coal-fired and natural gas-fired power generation systems

the retrofitted system achieves a net power generation efficiency of 49.67%

which is 1.28 percentage points higher than the conventional system; compared with the conventional gas turbine combined cycle

the electricity generated by the gas turbine exhaust heat is improved by 22.47%

and the net power generation efficiency of natural gas is increased by 4.62 percentage points. Exergy analysis reveals that the fundamental reason for energy saving in the retrofitted system lies in the reduction of exergy destruction and loss of the coal combustion

air preheater heat exchange

and flue exhaust

resulting in a 1.19 percentage points improvement in the exergy efficiency. After optimizing the mass flow rate of the bypass flue

the net electric and exergy efficiencies of the retrofitted system can further increase by 0.16 and 0.33 percentage points

respectively. After integrating the carbon capture unit

the CO2 concentration in the flue gas generated by natural gas combustion in the retrofitted system is enhanced by 2.43 times

reducing the total energy consumption for carbon capture by 5.28% and decreasing the energy efficiency penalty by 0.62 percentage points.