Fuel cell system and tail gas burner assembly and method

A fuel cell system comprising:

• a burner assembly comprising:
• (i) a hollow longitudinally elongate body extending along a central axis and having a first end and a second end,
• (ii) a burner wall located between said first end and said second end, and defining a first volume from said first end to said burner wall, and a second volume from said burner wall to said second end,
• (iii) an oxidant inlet into said first volume, the oxidant inlet for providing an oxidant flow therethrough,
• (iv) at least one hollow elongate burner abutting said burner wall or extending through an opening in said burner wall from said first volume to said second volume, and comprising:
• (a) a burner plate or mixer having a first side opening into said first volume, and a second side opening into said second volume,
• (b) a first fuel inlet into said first volume for feeding a first fuel from a first fuel passageway to said first volume;
• and,
• (c) a second fuel inlet into said second volume for feeding a second fuel from a second fuel passageway to said second volume;
• wherein the system further comprises at least one connection for selectively connecting the first fuel passageway to the second fuel passageway for delivery of a mixture of the first fuel and second fuel to the second fuel inlet.