What are the problems in SNCR applications?

There are issues in SNCR applications: low denitrification efficiency, as well as poor operational reliability and stability. 1. Due to the absence of a catalyst, the temperature required for the denitrification reaction is relatively high; for example, when ammonia is used as the denitrifying agent, the reaction temperature range is 870–1100°C. When the flue gas temperature exceeds 1050°C, ammonia begins to be oxidized into NOx; at 1100°C, the oxidation rate increases significantly, which in turn reduces the denitration efficiency ； On the other hand, it increases the amount and cost of the reducing agent. When the flue gas temperature is below 870°C, the reaction rate of denitrification decreases significantly. 4. Due to the reaction temperature range, the reaction time, as well as the setting and switching of the ammonia injection point, are restricted by the layout of the boiler furnace and/or the heating surfaces. 5. To meet the requirements for reaction temperature, the control of ammonia injection is highly demanding. Ammonia injection control has become the technical key to SNCR, as well as the biggest obstacle limiting the denitration efficiency of SNCR and the stability and reliability of its operation. 6. The ammonia leakage rate is relatively high, generally controlled at 5–10 ppm. 7. Due to limitations in the reaction temperature range and ammonia leakage, the denitration efficiency is low, typically ranging from 30% to 50%; for large power plant boilers, this efficiency is generally below 40%.

It has high requirements, is not easy to control, and there is excessive ammonia leakage

1. When the operating conditions of the boiler change, the amount of ammonia injected also changes; it is difficult to control this amount of ammonia, which requires high skill levels from the operators； 2. Low ammonia injection volume, resulting in flue gas emissions that do not meet standards ； To meet **environmental standards, a large amount of ammonia must be sprayed, resulting in a significant increase in ammonia emissions.