Black Liquor Spray Properties in Operating Recovery Boiler Furnaces

摘要

Black liquor spraying and drop formation have been studied previously in cold test chambers. In this paper, spray properties in an operating fumace were studied with the unique furnace endoscope developed at the HUT. The velocity, the shape and the length of the black liquor sheet were measured with this furnace endoscope in five operating recovery boiler furnaces by using a multiple exposure CCD-camera and an image-analysis-system. Mass flux varied between 4 and 14 g/mm~2s. When firing at more than 7degC above the atmospheric boiling point it was observed that he lower the mass flux the higher the rate of flashing. When flashing occurs, the sheet velocity may be accelerted by a factor of 3.4 No droplets were observed, only ligaments adn alrge framents of the sheet within the limits fo the operation range (2 m) of the endoscope. When the liquor sheet was formed, two amin sheet break-up meachanisms were observe,d i.e. perforated-sheet disintegration and wave disintegration. In the case of flashing, the sheet break-up mechanism was different. The comparison between results from the test chamber and furnace showed that the spray properties in both environemnts depend on same main parameters, i.e. on the difference between the firing temperature and atmospheric boiling point as well as on the mass flux.