5500C? i thought it’s not that much, chemistry can get you there

apparently not

thermite tops at some 2000C-something, and in any case can’t work above boiling point of aluminum (2470C)

only in few cases of adiabatic flame temperatures reach above 4000C, and all in oxygen. highest listed in wikipedia is oxygen/dicyanoacetylene at 4990C. maybe some wacky highly fluorinated oxidizer will allow for even higher temperatures. adiabatic detonation temperatures also top out at some 4500C even for the most energetic explosives

so really only practical way to get to 5500C is through use of electric arc