New technique for in-situ measurement of ammonia distribution in industrial combustion systems

A new technique of a laser gas monitoring system with a linear Charge-Coupled Device (CCD) has been developed to measure in-situ distribution of ammonia concentrations at various temperatures. The concentration is determined by measuring absorption with a tunable 13CO2 waveguide laser that is frequency modulated between two adjacent emission lines. One line coincides with a strong ammonia absorption line, while the other is used as a reference. By its referencing the system is auto-calibrated continuously. The high spectral resolution of the laser suppresses interference by other species. Multi-light path is used to achieve distribution of ammonia concentration in the flue gas channel, which is inhomogeneous. The linear CCD is used to replace detectors, which can avoid errors caused by parameter inconsistency of multi-detector and enable lower cost, fast and exact data acquisition and processing with computer by video interface. The measuring technique presented in this paper can be used to protect industrial environment against pollution in the chemical industry, several power plants and waste incinerators.