On the videos I've seen of blast furnaces, the iron is one solid stream from tapping till the mud gun closes the hole. Motion is imparted by the movement of pieces of Slag floating on top of the iron. INMO if you want to mimic this movement, use GRJ's idea of closely spaced LEDS but couple them to some sort of "chase lighting " module set at the slowest rate possible for effect. Something like is used on theater marquees.
BTW great looking blast furnace complex.
As for figures, you can get any from number of makers suitable construction workers but nobody makes steel mill specific figures. I'm thinking of using firemen that are modified and painted to resemble someone wearing "silvers".