Shadow spectrometer measurements of particle sizes from air-assisted atomizing spray nozzles

A major concern of industrialized nations is that power generation systems that burn hydrocarbon fuels release pollutants into the atmosphere that con tribute to acid rain and other atmospheric environment problems. Therefore, an active program of research on exhaust gas pollutant control has been identified and funded by the United States Department of Energy (DOE). A part of this program is a project on direct sorbent injection for combined SO₂/NO_χ; removal funded by the United States Department of Energy at the University of Tennessee Space Institute (UTSI). In this project, a wet sorbent slurry is injected into an exhaust stream in a duct. The sorbent chemically reacts with the SO₂ and NO_χ, and the exhaust gas SO₂ and NO_χ, are reduced.

The effectiveness of the SG2 removal process depends significantly on the gasdroplet surface contact. Thus, the spray atomization performance of the slurry spray nozzles has to be investigated. Research was done, where four l/4J-series air-atomizing nozzles (J22B, J22, J42, and J46) were characterized in atmospheric conditions, and one nozzle (J22) was characterized in a ducted hot gas, and two special, large fiow-rate nozzles producing different spray patterns were investigated in the atmosphere. There were the SGNIMIST^™ Ultrasonic and CasterJet^TM nozzles. An advanced, laser shadow spectrometer was used to measure the spray characteristies.

Results indicate that any of these nozzles (J22B, J22, J42, and J46) could produce a spray finely enough atomized for slurry sorbent injection for effective flue-gas clean up. The J22B nozzle operated satisfactorily between 2 gph and 10 gph; the other nozzles operated satisfactorily in the 5 to 20 gph range. In the hot duct, the J22 nozzle worked very well in atomizing water, and its spray filled the hot gas duct but did not impinge on the duct walls to any measurable extent; about 99 percent of the spray water mass evaporated within 17 feet of the nozzle tip. The two special nozzles operated at much larger flow rates (2-6 times larger) than the l/4J-series nozzles. However, because of their design, they produced sprays with Sauter-mean and volumetric-mean diameters comparable to the size ranges produced by the air-atomizing l/4J-series of nozzles used in the cold flow and hot duct tests. But, the distrbutions of the hquid water content measured in these sprays showed that the spray clouds were spatially nonuniform.