$26.$ For a fluidized bed reactor with air density at $1\mathrm{.}2$ kg$/$m and particle density of $2600$ kg$/$m$,$ calculate the minimum fluidization velocity for particles of $150$ m diameter, then estimate the bed height at three times the minimum fluidization velocity.

$27.$ In a pneumatic conveying system with a diameter of $150$ mm$,$ if the air velocity is $20$ m$/$s and the solid particles conveyed have a density of $2500$ kg$/$m with a mass flow rate of $0\mathrm{.}1$ kg$/$s$,$ calculate the solid loading ratio and then the pressure drop over a $10$ m section.