Historic and futuristic review of electron beam technology for the treatment of SO2 and NOx in flue gas

Despite worldwide effort, most electric power is still generated by the combustion of fossil fuel. Among the various combustion exhaust gases, SO2 and NOx can exert adverse effects on the human health and environment in both direct and indirect ways. However, their conventional removal technologies (e.g., flue gas desulfurization (FGD: wet, semi-dry, dry), selective catalytic reduction (SCR), and selective non-catalytic reduction (SNCR)) are often restricted to treat only a single target due to several disadvantages (e.g., high capital cost, low efficiency, and waste by-products (including acidic pollutant)). As a means to overcome these drawbacks, electron beam (EB) technology has been developed over the past four decades. A wide range of EB-related research has been undertaken from laboratory to pilot plant scale in Japan, Germany, US, Saudi Arabia, and Bulgaria, while EB flue gas treatment technology has been developed into industrial scale plant in China, Japan, and Poland. EB is well-known for simultaneous removal of SO2 and NOx while producing useful by-products (e.g., fertilizer). In this review, the theoretical background of EB technology is described with respect to the removal of SO2 and NOx from the flue gas based on the lab, pilot plant, and industrial plant. We also discuss the new EB hybrid technology proposed to overcome the problems associated with the stand-alone EB process. Finally, this review addresses the current status and limitations of EB technology along with its prospects.