I would like to suggest that the flame-thrower's flame particles have only forward force, and doesn't have gravitation force on them.
That results into one straight column of light (image #1) .. instead of "real" looking slight bended flame column (image #2).
This suggestion have base on real physics ... when (usually) flammable liquid exit from tip of flame-thrower, it's heavy and fall down .. and then, when it travels some distance, it's ignited and slowly raise up, as it's heated. (you can see on image #2)
This is ma 2 cents ..