Low-medium temperature application of selective catalytic reduction denitration in cement flue gas through a pilot plant

Abstract Low-medium temperature application of selective catalytic reduction (SCR) denitration in cement flue gas was established and investigated in this study. The 2000h continuous operation shows the concentration of NOx at the outlet can be maintained at 24 mg/Nm3 on average, while due to the increase of SO2 in flue gas, the NOx concentration increased to 57.5 mg/Nm3 after long time operation. The sulfur deposition is the main reason for catalyst deactivation, and SO2 is still a big obstacle for low-medium temperature SCR application in cement flue gas. The denitration efficiency was tested as fluctuated from 73.5% to 86.2%, and ammonia concentration after SCR was as still as high as 22.5∼60.0 mg/Nm3 due to the excessive ammonia injection from selective non-catalytic reduction (SNCR), shows serious ammonia escape problem for SNCR, and the potential application of hybrid SNCR-SCR technology. In order to maintain the denitration efficiency above 85%, the gaseous hourly space velocity (GHSV) should not be exceeded 2800 h-1, the electrostatic precipitators (ESP) setting at 60 kV was relatively appropriate, the temperature of the flue gas should be kept at above 200°C. The concentrations and toxic equivalent quantities (TEQs) of the PCDD/Fs congeners in the flue gas raised greatly after SCR reactor, indicating the PCDD/Fs concentration should be concerned during the application of low-medium temperature SCR, especially for the waste co-disposal processes.