The ornamental design for a flare stack burnerassembly, as shown and described.
FIG. 1 is a perspective of the flare stack burner assembly;
FIG. 2 is a front elevational view thereof;
FIG. 3 is a right side elevational view thereof;
FIG. 4 is a left side elevational view thereof;
FIG. 5 is a rear elevational view thereof; and,
FIG. 6 is a top plan view thereof.
The broken lines in the drawing represent environmental subject matter and form no part of the claim.
The flare stack burner assembly comprises a high pressure flare stack burner, a low pressure flare stack burner having a spherical valve and a central pilot.