You plan to use a tank of total volume V= 10 m3 to remove a contaminant at concentration Cin = 1 g/m3 from a waste stream with a flow rate of Q = 1 m3/h. The reaction is first order with a rate constant k1 = 0.5 h-1. Being a good process engineering, you run a tracer study and find that the tank can be represented as a CSTR in contact with a well-mixed but relatively stagnant region. The volume of the stagnant region is Vs = 2 m3 and the exchange flow between the two regions is q= 0.2m3/h.
a. Using symbols, draw the control volumes and develop the transient (unsteady-state) mass balance for both compartments.
b. Assuming steady-state, calculate the effluent concentration from the reactor.
c. Compare (b) to the case where the entire tank is considered to be well mixed. What do you conclude?