#### Observer design for state and clinker hardness estimation

Separator Fig 1 Cement mill process The mathematical model of the process is described by three diﬀerential equations see Grognard et al 2021 The ﬁrst two equations 1 and 2 describe how the input ﬂow rate of the separator is divided into the overﬂow and the underﬂow depending on the separation function Equation 3 corresponds to the material conservation in the ball