THE RATE OF DEPLETION OF NO BY REACTION WITH MOLTEN SODIUM-SALTS

Reactions of nitric oxide (NO) with molten sodium species have been id entified as a possible depletion mechanism in a kraft recovery furnace . Experiments have been conducted in which nitric oxide in helium was bubbled through molten sodium carbonate (Na2CO3) and mixtures of Na2CO 3 and sodium sulphide (Na2S). Results show that the depletion of NO fo llows a pseudo first-order rate expression. The rate of reaction is en hanced by the presence of sodium sulphide. Calculated activation energ ies are 89.0 and 41.2 kcal/mol for reaction with Na2CO3 and Na2CO3/Na2 S mixtures, respectively. Analysis of gaseous products for the Na2CO3 case indicates that NO is being reduced to nitrogen and oxygen accordi ng to the overall stoichiometry: 2NO double right arrow N-2 + O-2. Wit h Na2S present, no oxygen was detected in the gaseous product stream. It is not clear at this time whether Na2S reacts directly with the NO, or catalytically enhances the NO decomposition rate and then reacts w ith the O-2 produced. An example calculation for a recovery furnace sh ows that conversion of black liquor fuel nitrogen to NO which is subse quently depleted by reaction with sodium carbonate gives an exit gas c oncentration of 75 ppm NO in the flue gas.