Removal of high concentrations of NOx and SO2 from diesel off-gases using a hybrid electron beam technology

Abstract

The removal of high inlet concentrations of NOx (>1000 ppm) and SO2 ( >500 ppm) from diesel engine off-gases was studied using hybrid electron beam technology, i.e. electron beam combined with a wet scrubber method. Five different wet scrubbing solutions were examined: 3.5% NaCl solution (simulated sea water), NaOH solution, NaCl-NaClO2-phosphate buffer solution, NaCl-NaClO2 solution, and NaCl-H2O2 solution. The SO2 removal efficiency for all hybrid experiments was 100% at 10.9 kGy irradiation dose for inlet concentrations of SO2 varying between 501 ppm and 723 ppm. The NOx removal efficiency increased with increasing the absorbed dose and decreased with increasing the gas flow rate. NOx removal efficiency also increased with increasing the oxidant concentration (NaClO2) in the wet scrubber solution. The order of the NOx removal efficiency from lowest to highest in the hybrid system with the different scrubber solution is as follows: (NaOH, salty water) < H2O2 < NaClO2. The addition of oxidant to the wet scrubber solution increased NOx removal efficiency. An NOx removal efficiency of greater than 89.6% was achieved at 10.9 kGy irradiation dose for inlet NOx concentrations around 1500 ppm when 3.5% NaCl-5mMNaClO2-phosphate buffer solution was used. After treatment, the cleaned off-gases can be released into the atmosphere.