The cement industry has become the second largest source of CO2 and NOx emissions after the power industry, it is imperative to reduce CO2 and NOx emissions. O2/CO2 combustion technology can achieve CO2 enrichment and NOx reduction. As a result, its application possibilities are bright. In this article, a TTF-type decomposition furnace serves as the research object for a CFD simulation. In addition, the effects of pulverized coal combined O2/N2 and pulverized coal mixed O2/CO2 combustion on the velocity field, temperature field, material component, and NOx concentration distribution in the furnace are investigated concerning the changes of kinetic parameters of CaCO3 decomposition under different working conditions. Compared with the O2/N2 atmosphere, the temperature distribution in the high temperature zone of the decomposition furnace is more uniform under the O2/CO2 atmosphere. The temperature range is reduced in the area of extremely high temperatures. The NOx concentration at the decomposition furnace exit is reduced by 37%. The high concentration of CO2 at the output can be recycled and reused to reduce the greenhouse effect effectively. In addition, the high CO2 partial pressure increases the exit temperature by 111 K, doubles the O2 concentration, but decreases the raw meal decomposition rate from 95.9-82.2%. The process parameters must be improved to adapt to the O2/CO2 combustion technology.