Date of Award

Spring 1998

Document Type

Thesis

Degree Name

Master of Science in Environmental Science - (M.S.)

Department

Chemical Engineering, Chemistry and Environmental Science

First Advisor

Henry Shaw

Second Advisor

Howard David Perlmutter

Third Advisor

Richard B. Trattner

Fourth Advisor

Norman J. Van Houten

Abstract

Alkaline solutions of tert-butyl hydroperoxide (TBHP) selectively remove NO from simulated flue gasses. The investigation was conducted in a bubbling scrubber. NO removal efficiency of the scrubbing solutions was evaluated as a function of various operating parameters such as pH, oxidant concentration, oxidant to base mole ratio, residence time, temperature and flue gas compositions.

Alkaline solutions of TBHP show promise of being an economical choice for the selective removal of NO from flue gas. Solutions containing 0.2 M TBHP, 0.03 M NaOH (pH 12.5), and 1 minute NO residence time remove NO to below detectable levels at 53°C. The source, of alkalinity including KOH, NaOH and Ca(OH)2 was not a significant factor. NO removal increased with increasing ratio of alkali to TBHP, residence time, and temperature up to 80 °C. Above 80 °C vaporization of the reactant becomes significant. The ratio of alkali to TBHP resulted in a curve starting from 0.0004:1 where 100% removal was not observed to a plateau starting at 1:1 where 100% removal was observed at 75 °C. A nadir is obtained between a mole ratio of 0.005:1 to 0.03:1 TBHP solutions containing calcium hydroxide as the source of alkali (whose corresponding sulfite salt is not soluble) show little or no sulfite reaction and may be a good choice for scrubbing systems where SO2 is present. Calcium hydroxide solutions can oxidize and absorb NO to below detectable levels with 0.2 M TBHP, 0.0056 M Ca(OH)2 (pH 11.75), and 1 minute residence time at 63 °C.

The end products obtained from the oxidation of NO with TBHP are tert-butanol, and inorganic nitrite and nitrate.

This chemistry lends itself to application in conventional flue gas desulfurization (POD) scrubbers that use lime or limestone slurries as the scrubbing medium for SO, control. TBHP would be added to the FGD scrubber as an additive. This approach would convert an existing FGD scrubber to a SOx /NOx control unit at a fraction of the cost for separate NOx control.

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