Against the backdrop of global efforts to address climate change and actively promote the strategic goals of “carbon peak and carbon neutrality”, the clean and low-carbon transformation of the energy system has become a core issue for national development. Accelerating the low-carbon transformation of the coal-fired power industry and precisely reducing carbon emission intensity are key challenges in achieving climate goals. However, there are significant differences in the carbon emission characteristics of different types of coal-fired units, and their carbon emission levels and the emission reduction effects of coupling carbon capture technology have not been clearly compared. To reveal and compare the carbon emission intensities of different types of coalfired units, a carbon emission intensity calculation model applicable to different types of coal-fired units coupled with carbon capture and storage (CCS) systems was constructed.

The carbon emission intensities of typical coal-fired units such as 300 MW, 600 MW, 1 000 MW, double-reheat and IGCC at different load rates, as well as the carbon emission intensities after coupling with CCS systems, were compared and analyzed.

The research results show that at higher load rates, IGCC units have a lower carbon emission intensity, reaching 703 g/(kW·h) at 100% load rate, while the 300 MW unit has the highest carbon emission intensity, reaching 812 g/(kW·h). When the load rate decreases, the carbon emission intensity of the IGCC unit increases rapidly, reaching 948 g/(kW·h) at 50% load rate. The double-reheat unit has the lowest carbon emission intensity at 50% load rate, which is 781 g/(kW·h). CCS technology has a strong carbon emission reduction capacity and is an important means for the low-carbon transformation of coal-fired power. At 100% load rate, a 50% carbon capture rate can reduce the carbon emission intensities of 1 000 MW units, double-reheat units and IGCC units by 334, 329 and 295 g/(kW·h) respectively. Similarly, at a 50% load rate, a 50% carbon capture rate can respectively reduce the carbon emission intensity of 1 000 MW units, double-reheat units and IGCC units by 352, 358 and 379 g/(kW·h).

This study, through the construction of analytical models and systematic comparisons, quantitatively reveals the compound influence mechanism of the technical route of coal-fired units, operating load rate, and CCS coupling strategy on carbon emission intensity. In future power systems with a high proportion of renewable energy, coal-fired units will undertake more peak shaving and frequency regulation tasks. Quantifying the carbon emission differences of coal-fired units not only helps optimize the development path of low-carbon transformation in coalfired power, but also provides solid theoretical support and a decision-making basis for achieving the “dual carbon” goals.