Tsutomu Higo

Pilot plant experiment of NOx and SO2 removal from exhaust gases by electron beam irradiation

Abstract The effects of a small quantity of ammonia (NH3) added to exhaust gases containing nitrogen oxides (NOx) and sulfur dioxide (SO2), the characteristics of the NH3 added to the gases to facilitate the removal of NOx and SO2 when the gases were irradiated by electron beam were studied. The experiment was conducted in a pilot plant (capacity: 1000 Nm3/h) for one and a half years. The Phenol Disulfonic Acid Method and the Arsenazo-III Method were used for NOx and SOx determination in the irradiated gases respectively. The NH3 was added at either the reactor inlet or outlet and greatly improved the efficiency of NOx and SO2 removal, and made the by-products stable. NOx and SO2 removal were shown to be solely determined by total dose regardless of dose rate and residence time. A maximum efficiency of 90% was accomplished both in NOx and SO2 removals. Under the most economical conditions, 80% of NOx and 75% of SO2 were simultaneously removed with 80 ppm of NH3 exhausted to the atmosphere. The amounts of nitrogen and sulfur in the gas before and after irradiation satisfactory balance under this condition. The collected products in the electrostatic precipitator are largely composed of a mixture of ammonium sulfate (NH4)2SO4 and ammonium nitrate sulfate (NH4)2SO4▿2NH4NO3 plus (NH4)2SO4▿3NH4NO3.