Investigation on the PCDD/Fs distribution of quenched off-gas from electric arc furnace

The method of quenching was adopted to reduce the emission of PCDD/Fs from a pilot scrap preheated EAF. Because quenching can effectively inhibit the de novo synthesis of dioxins. Meanwhile the temperatures at the inlet and outlet of the quenching part of EAF off-gas were measured to investigate the quenching effect. The results show that the temperatures of the off-gas are quenched from about 1300 °C to about 250 °C in the whole tap-to-tap cycle of EAF, which attains the expected cooling effect. The dioxin Toxic Equivalent Quantity (TEQ) concentrations and congener distributions of off-gas and three kinds of sampling ash were analyzed. The results indicate that the TEQ concentration of PCDD/Fs is 0.13 ng-I-TEQ/Nm³ at the outlet of the chimney A (D4), which is far below the dioxin emission limit for EAFs (0.5 ng-I-TEQ/Nm³) in China. At the same time the fingerprint suggests that the quenching effectively restrains the de novo synthesis, and dioxins de novo synthesize in the following flue and bag filter to some extent.