Accumulation of powder in hot zone of spray dryer

[R_mehmood]

We are using Rotary atomizer type spray dryer for drying of Herbal Powder Extracts.
a couple of days ago, during production, powder started burning at same process parameters.
When opened it was found that very thick layer of powder was accumulated at hot zone ( area above atomizer disk).(see the picture attached)
The powder is only at one side of the body.
No clue. can any one help

 

[Latexman]

Is this a one time thing? How long has this process ran? Does it happen always after some time?

Good luck,
Latexman

To a ChE, the glass is always full - 1/2 air and 1/2 water.