Apparatus and a method for tapping metal
An apparatus and a method for tapping molten metal from below a molten electrolyte layer less dense than the metal is described. The apparatus comprises a pipe comprising a protruding enlarged wall portion at an operative end which is immersed in the molten electrolyte and metal during tapping operation. The enlarged wall portion helps to minimize entrainment of electrolyte residue from the electrolyte/metal interface during tapping. The orientation of the enlarged wall portion may be in the general direction of the crucible.
1. An apparatus for tapping molten metal from below a molten electrolyte less dense than the molten metal, the molten metal and the molten electrolyte forming a boundary at an electrolyte/metal interface, the apparatus comprising:
a pipe having a first end and a second end opposite the first end,
the second end adapted for immersion into the molten metal,
the pipe defining an internal bore extending along a length thereof between the first end and the second end, the internal bore for passage of molten metal therethrough,
the pipe having an enlarged wall portion proximate the second end, the enlarged wall portion extending radially outwardly from the bore in at least one direction and extending axially away from the second end a predetermined distance,
the pipe having a front wall portion proximate the second end, said front wall portion being opposite the enlarged wall portion, the front wall portion having a first wall thickness, the first wall thickness being defined from the internal bore to a leading edge,
the enlarged wall portion having a second wall thickness greater than the first wall thickness, the second wall thickness being defined from the internal bore to a trailing edge and
wherein the second wall thickness is greater than 1.5 times the first wall thickness,
whereby during tapping the enlarged wall portion traverses the electrolyte/metal interface and defines an obstacle to limit entrainment of electrolyte into the pipe.
2. The apparatus according to claim 1 , wherein the second wall thickness is greater than 2 times the first wall thickness.
3. The apparatus according to claim 1 , wherein the second end of the pipe in cross-section has an elliptical perimeter defining a major and a minor axis.
4. The apparatus according to claim 3 , wherein the internal bore is positioned off-centered along the major axis.
5. The apparatus according to claim 1 , wherein the trailing edge of the enlarged wall portion defines a straight edge.
6. The apparatus according to claim 1 , wherein the enlarged wall portion in cross-section defines a substantially triangular perimeter.
7. The apparatus according to claim 1 , wherein the second end of the pipe in cross-section has a circular perimeter.
8. The apparatus according to claim 7 , wherein the internal bore is eccentrically adjacent the front wall portion.
9. The apparatus according to claim 1 ,
the front wall portion comprises a forwardly facing projection, and
the enlarged wall portion defining a rear width at the trailing edge, the second wall thickness being between 1.5 to 2 times the first wall thickness.
10. The apparatus according to claim 9 , wherein the trailing edge of the enlarged wall portion defines a straight edge.
11. The apparatus according to claim 10 , wherein the enlarged wall portion in cross-section defines a substantially triangular perimeter.