It is impossible to explain everything here. First there is the choice of technology, choice of furnaces, smoke treatment, recovery of energy, determination of air volumes, determination of smoke volumes, etc..The choice of furnaces is generally made on grid ovens because they have a number of advantages (Provides good thermal efficiency and destruction: the grids facilitate the combustion of the waste by guaranteeing the release of energy and maintain the ignition and combustion).
Impossible to go over everything without writing an entire book about it. The first question you need to ask yourself, what is it you are incinerating? An incinerator that disposes of bodies will be entirely different than an incinerator that disposes of expired organophosphates.