Q-2 [10-maris) A fixed bed (lab-scale) of activated carbon was designed to study the adsorption of n-butanol from air. The bed had a diameter of 0.1 m and a length of 0.9 m. The bulk density of activated carbon was 470 kg/m. The n-butanol-air mixture entered the fixed bed with a superficial velocity of 0.5 m/s and a density of 1.08 kg/m. The initial concentration of n-butanol in the air before the adsorbed was 0.05 kg n-butanol/kg activated carbon. The lab-scale breakthrough data of the mixture flowing through the fixed bed are given in the following table. 4 5 6 Time 0 1 1.5 2. 2.5 3 3.5 (hr) Conc. 0 0.0005 0.00125 0.0025 0.004 0.0065 0.01 Concentration values are in kg n-butanol/kg activated carbon 7 8 0.0145 0.028 0.039 0.0465 0.049 (a) Determine the breakthrough time (tb) if the breakthrough concentration is 2% of feed concentration. [3 marks] (b) Determine the length of unused bed (LUB) at the breakthrough concentration. [3 marks] (c) If the breakthrough time required for a new bed is 10 hrs, calculate the new total length of bed required for the fixed bed. [4 marks]