Sludge blending has become one of the means to transform the energy structure of coal-fired power plants. Based on the existing coal-fired flue gas system of Zhejiang Jinhua Ningneng Thermal Power Plant, this paper proposed to add activated carbon injection purification technology in the flue gas system. Based on Fluent simulation and analysis, the numerical simulation analysis of the uniformity of the spray distribution of activated carbon in the flue gas was conducted from three aspects, such as the position of the spray point of single and multiple holes, the spray angle, and the mass flow rate of the spray, and the impact and safety of the activated carbon spraying system applied in the field of flue gas treatment were analyzed. The results showed that compared with single-nozzle injection, multi-nozzle injection could make the activated carbon distribution more uniform, but the cost was higher. For single-nozzle spraying, when the location of the spraying point was at the centre of the section from the horizontal elbow to the exit of the vertical elbow, the diffusion effect was good and the activated carbon had a long retention time. The economic efficiency was the highest when the spraying angle was selected to be parallel to the flue gas flow and the mass flow rate was selected to be 10 kg/h. For multiple-nozzle spraying, the adsorption effect of the activated carbon was better when the mass flow rate was selected to be 15 kg/h, but the cost was higher. Whether it is single-nozzle injection or multi-nozzle injection, parallel flue gas flow was chosen as the angle of activated carbon injection, in which the diffusion area was relatively large, the diffusion effect of activated carbon was relatively good, and the distribution was relatively uniform in the cross-section. The application of activated carbon injection system in the field of flue gas treatment has less impact on the environment and the safety is within the controllable range.