Self Assessment Quiz

Q3.1. You are operating a plug flow reactor where a first order irreversible liquid reaction A↔B is taking place where conversion of A 0.66 is obtained.  What would be the conversion if a recycle reactor with R = 4 is used

Q3.2. A gas phase reaction  A = B + C is taking place in a plug flow reactor at 5000C. 5cum gas is recycled for every cum of fresh feed. Determine space time required to achieve 70 percent conversion. Data: k = 1.2/s, P = 1013 kPa . Sourced from Fogler.

Q3.3. The elementary gas phase reaction A→B is carried out in a packed bed reactor at 3000C. Recycle ratio is 5, volumetric flow rate is 10 lit/s and pressure gradient 0.0025 atm/m. The flow is turbulent. What overall conversion can be achieved in a 10m reactor and 0.02 sq.m in cross section. Source Fogler.  Data: CA0 = 0.10mol/L , P0 = atm, assume ideal gas, V0 = 10 lit/s K = 0.25/s

Q3.4.Consider the recycle reactor system where the reaction A + B = C is carried out isothermally at 5700C, 1.0atm pressure. A part of the consider exit gases are heated to reactor temperature and recycled. The pressure drop may be neglected. Estimate the reactor volume for 50 percent conversion .What might be the reactor volume required if C was not a condensable gas?


FA0 = 1 mol/hr

FA0 = 1 mol/hr

R = 4

K = 1 cum/kmol-sec

Condenser exit is at 45°C, Vapor pressure at 45°C = 0.2atm

Q3.5. An autocatalytic reaction  A→B with a rate constant  k = 10/min,  feed rate 12 gmol/min is to be carried out. Determine the Residence time to get a conversion of  99%  in a (a) CSTR (b) PFR (c) Recycle Reactor with R =4  (d) Optimum recycle. CA0 = 1.0 kmol/cum. . Sourced from Levenspiel.

Q3.6. An isothermal reaction A <=> B is carried out in an aqueous solution. The reaction is first order in both directions. The forward velocity constant is 0.4/hr and equilibrium constant 4.0. The feed to the plant contains 100 kg/cum A and enters at 12 cum/hr.

The reactor effluent passes to a separator where B is completely recovered. The reactor is a stirred tank of volume 60 cum. A fraction “y” of the unreacted effluent is recycled as a solution containing 100 kg/cum of A and rest discarded.

Product B is worth Rs.2.0/kg and operating costs are Rs. 50/ cum solution entering the separator. What value of “y” maximizes the operational profit of the plant? What fraction of A fed to the plant is converted at the optimum? . Sourced from Denbigh