PLASMA VERSUS THERMAL EFFECTS IN FLUE-GAS NOX REDUCTION USING AMMONIARADICAL INJECTION

A plasma-assisted ammonia injection technique was previously demonstra ted as having the potential to remove NOx from combustion flue gases a t SCR-comparable levels without the use of catalysts. However, these d emonstrations did not prove the advantage of plasma assistance because they did not explicitly account for enhanced radical production by bu lk thermal heating. An experiment using hot ammonia injection was perf ormed to separate this thermal effect from the effect of radical produ ction via interaction with a plasma. Under excess air conditions, resu lts show that a thermal effect does provide improved NOx reduction, bu t not to the level achieved with the use of a plasma source. However, heating the injection gases provides only a minor improvement in NOx r eduction at NH3/NOx ratios and temperatures typical of commercial cold SNCR applications. The plasma effect in ammonia radical injection was also found to be significant, accounting for an additional 15% to 35% of absolute NOx reduction beyond any thermal benefit at typical exces s air conditions. The ammonia radical injection technique continues to show promise as an effective NO, reduction alternative.