Effects of co-disposal of sludge based on TTF-type precalciner on NOx emissions

To reduce the emission of nitrogen oxides (NOx) during the co-disposal of sludge in a TTF-type precalciner, an optimized co-disposal process of a TTF-type precalciner has been implemented in a cement plant in Hebei. The model was built using ANSYS FLUENT software. The effects of three singlefactor perspectives (sludge input ratio, gas flow rate, and tertiary air temperature on NO concentration) were investigated. The response surface method of Box–Behnken design was used. When the sludge ratio increased from 0 to 25%, the NO concentration at the outlet was 122–297 mg/m3. Meanwhile, it increased from 192 mg/m3 to 241 mg/m3 since the airflow increased from 95 m3/s to 122 m3/s. The maximum NO concentration was 192 mg/m3 when the tertiary air temperature was 1170 K. The interaction between airflow and sludge ratio was more significant than any other interaction between other conditions (P < 0.05). Finally, the optimum conditions were a sludge ratio of 5%, airflow 109 m3/s, and tertiary air temperature 1280 K. NO concentration was 166.9 mg/m3 under this condition.