Common Problem

1. Reaction temperature & core principle SCR (Selective Catalytic Reduction) adopts catalyst to trigger reduction reaction between ammonia and NOₓ, with optimal reaction temperature ranging 280–400℃. SNCR (Selective Non-Catalytic Reduction) completes redox reaction without catalyst, requiring high flue gas temperature of 850–1100℃ to activate the reaction between sprayed ammonia/urea and nitrogen oxides. ||

2. Denitrification efficiency SCR achieves high removal efficiency of 85%–95%, capable of meeting ultra-low NOₓ emission standards for large power boilers. SNCR only reaches 40%–70% efficiency, unable to realize deep denitrification, suitable for loose emission control requirements.

3. Equipment layout & floor space SCR system needs independent catalyst layers, ammonia injection grids, static mixers and supporting heating devices, occupying large space and usually arranged at the tail of economizer. SNCR only sets simple urea/ammonia spraying nozzles inside furnace or high-temperature flue, with compact structure and tiny occupied area, low transformation difficulty for old kilns.

4. Ammonia escape risk & by-products SCR has uniform gas-liquid mixing and controllable ammonia escape (below 3ppm) under normal operation. SNCR suffers uneven reagent mixing; excess spraying leads to severe ammonia escape, which easily generates ammonium bisulfate, blocking subsequent air preheaters and dust removal equipment. 5. Operation & investment cost SCR features high initial investment due to expensive catalyst, which needs replacement every 3–5 years with extra maintenance expense. SNCR has low construction investment and no catalyst replacement cost, yet consumes more reducing agent, resulting in higher long-term reagent operating cost. 6. Applicable working conditions SCR matches large-capacity thermal power boilers with stable flue gas temperature. SNCR fits medium-small industrial kilns, garbage incinerators and boilers with wide temperature fluctuation inside furnaces.