$7.$ What do you mean by fluidized bed reactor? Also give design equation for fluidized bed reactor. Explain in detail. $(15)$

$8.$ Describe the following:

$($a$)$ The working and design equations for non$-$isothermal and non$-$adiabatic conditions encountered in fixed bed reactors.

$($b$)$ Discuss the two phase fluidized bed model used for solid catalyzed reactions.