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.
Keywords: Electric arc furnace PCDD/Fs quenching congener distribution.
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