A stream of nitrogen gas containing 9.5 % benzene by volume is to be scrubbed in...

Transcribed Image Text:

A stream of nitrogen gas containing 9.5 % benzene by volume is to be scrubbed in a packed tower with an absorption oil in order to reduce the benzene content to 0.5 % by volume before the gas can be recycled. The feed gas rate is 1550 Nm3 /h; it enters the column at 308 K. The column operates at 308 K and 1.07 bar pressure. Benzene free oil is fed to the column at a rate of 4600 kg/h. The equilibrium distribution of benzene between the gas and the oil is given below: Y = 0.19 X 1 + 0.81 X Where X = moles of benzene per mole of benzene-free oil Y = moles of benzene per mole of nitrogen The properties of oil are: density = 840 kg/m3 ; viscosity = 4.5 CP, and mol.wt. = 230 (a) Do you think that the system is ideal (i.e. obeys Raoult's law) in respect of equilibrium? Justify your answer by calculations. Can you calculate the vapor pressure of benzene at the given temperature? (b) Calculate the mole fraction of benzene in the oil at the bottom of the tower (c) Calculate the diameter of the tower if the superficial gas velocity is 0.32 m/s. If the tower is packed with 1 1 2 (inch Raschig ring, calculate the ratio of actual gas rate to that of flooding. (d) If the separation is done in a plate column and the overall tray efficiency is 35 %, determine the number of real trays required. A stream of nitrogen gas containing 9.5 % benzene by volume is to be scrubbed in a packed tower with an absorption oil in order to reduce the benzene content to 0.5 % by volume before the gas can be recycled. The feed gas rate is 1550 Nm3 /h; it enters the column at 308 K. The column operates at 308 K and 1.07 bar pressure. Benzene free oil is fed to the column at a rate of 4600 kg/h. The equilibrium distribution of benzene between the gas and the oil is given below: Y = 0.19 X 1 + 0.81 X Where X = moles of benzene per mole of benzene-free oil Y = moles of benzene per mole of nitrogen The properties of oil are: density = 840 kg/m3 ; viscosity = 4.5 CP, and mol.wt. = 230 (a) Do you think that the system is ideal (i.e. obeys Raoult's law) in respect of equilibrium? Justify your answer by calculations. Can you calculate the vapor pressure of benzene at the given temperature? (b) Calculate the mole fraction of benzene in the oil at the bottom of the tower (c) Calculate the diameter of the tower if the superficial gas velocity is 0.32 m/s. If the tower is packed with 1 1 2 (inch Raschig ring, calculate the ratio of actual gas rate to that of flooding. (d) If the separation is done in a plate column and the overall tray efficiency is 35 %, determine the number of real trays required.

Answer rating: 100% (QA)

The detailed ... View the full answer