Full scale combustion tests for a conventional fuel nozzle and a self-biased one were carried out using a two-stage radiant tube burner as the basis. Compared with the conventional nozzle, more than 40% reduction in NO_x emission was achieved with the self-biased nozzle. Under the same furnace temperature, the peak temperature was lowered and the temperature uniformity on the radiant tube was enhanced with the self-biased nozzle. The optimal design criteria for the self-biased nozzle were derived.