The hot face service temp is 2,200ºf but the material is considered a consumable at those temps. Blast furnaces need regular maintenance and filling with the refractory patch at those working temps.
Your KK grill is designed to last a lifetime at "food cooking temps" not to be used as a kiln.
The smoke point of lard is only 370ºf So high temps where you create enough heat to make your grill expand is really unnecessary... There is no escaping physics.. the grill does and will expand when taken to high temps.. This can be confirmed by the small crazing on the smooth grout finish on your grill's lips. High temp blasting your grill from black to grey will be detrimental to it's long life and is not necessary. The inside of a grill/smoker should be black.. it's not dirty.
Regularly taking your KK to 900ºf dome / 1452ºf lower to clean your grates is a good way to damage your grill..
Please do not do it..