LBL PHOSNOX PROCESS FOR COMBINED REMOVAL OF SO2 AND NOX FROM FLUE-GAS

The addition of yellow phosphorus in wet scrubbing systems can result in the high efficiency simultaneous removal of SO2 and NO(x) from flue gas. Yellow phosphorus reacts with O2 to produce O3 which selectively oxidizes NO to NO2. Subsequently, NO2 and SO2 are removed from flue gas by dissolution into an aqueous alkaline solution/slurry, where they are converted to ammonium sulfate and gypsum. Yellow phosphorus is oxidized to yield a desirable commercial by-product, phosphoric acid. This new technology has been tested jointly by LBL and Bechtel at LBL with a 20 cfm [9.44 x 10(-3) m3/sec] bench-scale scrubbing absorber. The test results indicated that greater than 90% NO removal efficiency could be achieved with an L/G > 60 (gal/min)/(1000 cu ft/min) [1 liter/m3 = 7.48 gal/1000 cu ft] for NO concentrations ranging from 60 to 600 ppm. A stoichiometric ratio, P/NO, as low as 0.6 has been achieved. Economic projections for the PhoSNOX process have been made based on a conceptual process configuration. The estimated costs compare favorably with the SCR for high removal and are competitive with urea injection processes for low levels of NO(x) removal. FMC has conducted a safety study of the process and concluded that the potential safety hazards of yellow phosphorus can be avoided if proper precautions are taken.