Application of a Mean Flow Velocity Estimation Scheme Based on Flow Field Characterization and Distribution Point Optimization for Carbon Monitoring in Coal-Fired Power Plants: A Numerical Study

CO2 online monitoring provides a method to obtain carbon emissions by directly quantifying the flue gas flow velocity and CO2 concentration. However, significant flow rate measurement errors arise due to the complexity of turbulence in large-diameter stacks. To address the issue, this study utilizes turbulent numerical simulation combined with mean velocity estimation error analysis to investigate the flow field of typical stacks in coal-fired power plants. The simulation results demonstrated that the evolution of turbulence exaggerates velocities. The flow field exhibits stable turbulent characteristics in a single-introduced stack, while in the double-introduced stack, the flow field dynamically evolves due to asymmetric collisions and abrupt expansion. Furthermore, the effects of load and temperature on the estimation error of flow velocity is established. The optimum monitoring height, the ideal chord angle and the stepped number of deployment points based on the log-linear method is determined. The turbulence correction factor is introduced, and the formula linking estimation error and monitoring height is established in the single-introduced stack. The maximum estimation error is reduced from 14 % to 0.3 %. Finally, the systematic and simplified optimization scheme for estimating mean flow velocity is summarised, which provides a powerful reference for flow rate measurement for online CO2 monitoring in coal-fired power plants.