[en] A pilot plant for flue gas treatment with electron beam has been built at Power Plant Kaweczyn, near Warsaw. The irradiation part of the pilot plant was put into operation in 1991 and the complete installation in spring 1992. The starting tests consisted of studying the components reliability and influence of the two-stage irradiation process on efficiency of NO_x removal. The results have shown that the two-stage irradiation leads to remarkable energy savings and retains high NO_x removal. The mathematical models of the double and triple irradiation process are discussed. (author)