Continuous analyser for sulphur dioxide - in flue gases using cathode tube to irradiate test cell

摘要

Process uses a fused concave cathode lamp filled with dry air at a pressure of several mm. Hg. This is operated at a charging current of several mA. This forms a stable oscillation i the activated N2 mols. in the tube. A radiation is emitted from these mols. at various energy levels. Firstly there is a measurement beam of infiltered radiation in one frequency band. There is then a second reference beam in a neighbouring frequency band filtered through an SO2 capsule. Both pass through the test cell. The quotient of the intensities of these two beams in the spectral region of the neighbouring frequency bands after passage through the absorption cell is used as a measure for the SO2 concn. in the gas mixture being analysed. Used esp. for the determination of SO2 concn. in exhaust and flue gases. e.g from the combustion S contg. fuels such as coal, oil, petrol, diesel oil etc., Flame photometry detectors (FPD) have high sensitivity but are interfered with by CO2, H2O and hydrocarbons. The method described gives a means of determining SO2 accurately and with high sensitivity given in the presence of these components.