Application Of The SNCR-SCR DeNO_x Technology On A 500 T/d Municipal Waste Incinerator

In recent two decades, Waste-to-Energy business has been progressively developed in China. At the same time, the national emission standard for WTE is increasingly stringent.Especially,the emission standard for NOx has changed from 400 mg/m3 to 250 mg/m3. The technology selection, design and operation for the deNOx of the flue gas from Nanjing Jiangnan Waste-to-Energy Plant under China Everbright International Limited(the Project) has been studied in this paper.The Project is equipped with 4 municipal solid waste incinerators with a treatment capacity of 500 t/d each. After technical and economic evaluation, the SNCR/SCR deNOx process is adopted in the Project. For the high-efficiency SNCR system, sprayers are arranged in multiple layers and spots, two layers of which were put into use simultaneously in operation. As for the operation parameters of the sprayers, the compressed air pressure is designed at 3.0 bar and ammonia flow at 85 L/h. The SCR reactor is placed between the bag filter and the draught fan, adopting low-temperature catalyst with the support of TiO2 and the active component of V2O5 based on lateral flow reactor. Three catalyst modules are placed as one layer for each line. 16.5 L/h of ammonia water is used after evaporation to supply the reagent for the SCR system.The dosage of ammonia water can be adjusted by the control system.After experiment, it’s concluded that the jointly used of high-efficiency SNCR system and highly distributed sprayers can provide higher deNOx efficiency and lower ammonia slip. That’s because adopting the thermocouples in the SNCR system are helpful to trace the temperature precisely and timely inside the boiler in three dimensions. So it’s realistic to control the sprayers more accurately. It’s recommended to directly supply ammonia for the SCR system to save the operation costs. The experiment shows that the deNOx efficiency of SCR can meet the emission standard with the inlet gas temperature of above 150 ℃. In the daily operation, the emission index of NOx is often less than 80 mg/m3, with an obvious deNOx effect.The purchasing cost of SCR accounts for 72% of the total deNOx cost, 42% of which is for catalyst module. The unit cost of catalyst accounts for 66% of the total cost of deNOx system after considering the life cycle. The unit deNOx operation cost is 4.42 RMB/t and the depreciation cost of the deNOx equipment is 6.57 RMB/t. The total unit deNOx cost is approximately 11 RMB/t.Based on the study of the Project, it’s proved that the application of SNCR/SCR deNOx process in Waste-to-Energy plant is feasible and economically manageable.