SNCR deNOx process by urea decomposition system and evaluation of CO2 reduction

In Japan, a Waste To Energy (WTE) plant with a strict NOx emission limit value of 50 ppm (O 2 12%-dry) has been operated with selective non-catalytic reduction (SNCR). Ammonia or urea is used as a media for SNCR, but urea is safer than ammonia and is easy to use. However, urea has a problem of lower NOx removal efficiency than ammonia. Therefore, a technology to convert urea to ammonia on-site is necessary. In this work, the basic performance of this urea decomposition system, the operation results of SNCR, and the CO 2 reduction by SNCR were studied.The urea decomposition system was a catalytic reactor, and when the catalytic temperature was above 250 °C and the space velocity was below 6000 h −1 , the conversion to ammonia was almost 100%. The NOx removal ratio of SNCR was 20% at an ammonia equivalence ratio of 0.4 and about 40% at an equivalence ratio of 0.6, a performance level similar to other plant. Furthermore, it was estimated that CO 2 emissions were reduced by 3.1% by applying SNCR instead of SCR, and when combined with other CO 2 reduction measures of this plant, CO 2 emissions were reduced by 16.2%.