SELECTIVE MONITORING OF TRS WITH CONTINUOUS SULPHUR GAS ANALYZERS.

Many of the real-time, continuous total reduced sulphur (TRS) analyzers used in the pulp and paper industry (e. g. , the ones with coulometric, fuel cell or ultra-violet sensors) are subject to positive errors in determining regulated odoriferous reduced sulphur (ORS) compounds. One of these errors can be caused by odorless carbonyl sulfide (COS) present in the flue gas of overloaded or poorly controlled recovery furnaces. The technique of successfully eliminating this positive error involves the use of acidified potassium dichromate for removing all sulfur compounds except COS in one of two parallel sampling channels, and determining the ORS by difference. The same reagent solution can also be used with a single channel analyzer of the above types in an ″on-and-off″ mode for periodic measurements of COS in the flue gas stream.