The application belongs to the field of
flue gas
carbon dioxide concentration determination, and particularly discloses a
flue gas
carbon dioxide concentration online detection method and
system, which comprises the following steps: obtaining the average absorption coefficients of
carbon dioxide and
water vapor under different temperatures and concentrations respectively, and obtaining the relationship between the
flue gas average absorption coefficient and the temperature and concentration; constructing the relationship between the theoretical
spectral radiation intensity of the gas layer outward emission and the
flue gas average absorption coefficient, and obtaining the relationship between the theoretical
spectral radiation intensity and the gas temperature and concentration; collecting the actual
spectral radiation intensity of the
flue gas emission along the direction perpendicular to the
airflow direction in real time through an
infrared spectrum measuring device; constructing a target function with the difference between the actual spectral
radiation intensity and the theoretical spectral
radiation intensity; solving the target function by using an optimization
algorithm, and obtaining the temperature and concentration of carbon dioxide and
water vapor corresponding to the lowest target function value. The application can realize carbon dioxide concentration measurement without an additional
light source emission device, and has simple structure and efficient collection.