(a) A 35m long standpipe carrying Group A solids at a rate of 85kg/s is to be aerated in order to maintain fluidized flow with a voidage in the range 0.52 to 0.58 . Solids enter the top of the standpipe at a voidage of 0.58 . The pressure and gas density at the top of the standpipe are 2.4 bar (abs) and 2.5 kg/m3 respectively. The particle density of the solids is 1550kg/m3. Determine the distance of the first aeration point from the top of the standpipe, the mass flow rate of aeration gas at this point and the gas pressure at this point. Explain the calculation procedure as you go along. Explain how you would determine the position and gas flow rates at the other aeration points