Process for the removal of acid forming gases from exhaust gases and production of phosphoric acid

Patent · Wed Jan 01 04:00:00 EST 1992

OSTI ID:868251

Chang, Shih-Ger ^[1]; Liu, David K ^[2]

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1. El Cerrito, CA
2. San Pablo, CA

Exhaust gases are treated to remove NO or NO.sub.x and SO.sub.2 by contacting the gases with an aqueous emulsion or suspension of yellow phosphorous preferably in a wet scrubber. The addition of yellow phosphorous in the system induces the production of O.sub.3 which subsequently oxidizes NO to NO.sub.2. The resulting NO.sub.2 dissolves readily and can be reduced to form ammonium ions by dissolved SO.sub.2 under appropriate conditions. In a 20 acfm system, yellow phosphorous is oxidized to yield P.sub.2 O.sub.5 which picks up water to form H.sub.3 PO.sub.4 mists and can be collected as a valuable product. The pressure is not critical, and ambient pressures are used. Hot water temperatures are best, but economics suggest about 50.degree. C. The amount of yellow phosphorus used will vary with the composition of the exhaust gas, less than 3% for small concentrations of NO, and 10% or higher for concentrations above say 1000 ppm. Similarly, the pH will vary with the composition being treated, and it is adjusted with a suitable alkali. For mixtures of NO.sub.x and SO.sub.2, alkalis that are used for flue gas desulfurization are preferred. With this process, better than 90% of SO.sub.2 and NO in simulated flue gas can be removed. Stoichiometric ratios (P/NO) ranging between 0.6 and 1.5 were obtained.

• Research Organization: Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA
• DOE Contract Number: AC03-76SF00098
• Assignee: Regents of University of California (Alameda, CA)
• Patent Number(s): US 5106601
• OSTI ID: 868251
• Country of Publication: United States
• Language: English

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