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PhoSNOX: Yellow Phosphorous for Flue Gas Scrubbing


E.O. Lawrence Berkeley National Laboratory




Fossil fuels often contain sulfur an nitrogen compounds that, upon combustion, release SO2 and various oxides of nitrogen (NOx) into the atmosphere causing acid rain. Sulfur oxides can be effectively removed by wet flue gas desulfurization scrubbers which use aqueous slurries of limestone or other alkaline material to neutralize the sulfurous and sulfuric acids produced by dissolution and subsequent oxidation of SO2 . The resulting solid slurry is disposed of in landfills. The wet flue gas desulfurization scrubbers can not remove sufficient amounts of NOx because of the low solubility of NOx in aqueous solution. A separate scrubber for NOx removal requires additional capital investment; and current denitrification methods are insufficient to meet Federal emission standards of n con= 75 ppm, require expensive starting materials, and create a disposal problem for the by-products of the processes.

Ted Chang and David Liu at Berkeley National Laboratory have developed a process that simultaneously removes almost 100% of SO2 and NOx from exhaust gases in a cost efficient manner and produces commercially valuable by-products. The process uses an aqueous emulsion or suspension of yellow phosphorous to help convert NOx into nitrous and nitric acids, effectively reducing the NOx concentration to uire 20 ppm. By keeping the emulsion alkaline with the addition of any suitable alkaline material, sulfur oxides are also removed. The resulting by-products include phosphate, nitrate, and sulfate salts of calcium, magnesium, sodium, potassium, and ammonium, depending on the alkaline material used, which are important plant nutrients and constitute the major components of fertilizers.

STATUS: U.S. Patents #5,164,167, #5,106,601. Available for licensing



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