Development of a non-dispersive UV-visible analyzer for simultaneous measurmeents and of SO_2 and NO_2 in stacks emissions

摘要

Non-dispersive analyzers have been used for measurement of gases for many years and were recently introduced as on-line meters for continuous stack emission measurements in industrial plants. SO_2 and NO_2 are among the most important gases in the emissions of the petrochemical industry. The development of a UV-visible meter for these gases is presented. It consists of three optical channels snesing differnet spectral regions: 300 nm for SO_2, 380 nm for NO_2 and 320 nm used as a common refernece. Each channel has an interference filter of 10 nm bandwidth centered at each channel's wavelength. Each filter is followed by a photodiode and its electronics which are housed in a single compartment with no moving parts. An incandescent lamp with high output in the UV region was selected and mounted on the opposite side of the stack by appropriate flanges. The equipment was designed to measure in the range between 0 and 500 ppmv with a resolution of about 2 ppmv. Performance parameters like signal stability, dark current, detection limit and calibration curves are shown.