2. A completely stirred tank reactor (CSTR) is used to treat an industrial waste

Question

2. A completely stirred tank reactor (CSTR) is used to treat an industrial waste product using a reaction that destroys the pollutant according to first-order kinetics, with the rate constant k = 0.216 day. The reactor volume is 500 m and is constant, the volumetric flow rate of inflow and outflow is 50 m/day, and the inflow pollutant concentration is constant at 100 mg/L a) What is the steady state outflow concentration after treatment? b) The industrial waste feed to the reactor is shut down (flow = 0). Starting at t 0, the flow entering and leaving the CSTR is set to O. What is the concentration in the reactor at the end of 5 days after t = 0?

Explanation / Answer

Rate constant k = 0.216 /day

Inlet concentration C in = 100 mg/L

Inlet flow rate Q = 50 m3/day

Volume V = 500 m3

Part a

At steady state

Material balance of pollutant

Input = output + generation

Q * C in = Q * C out + k*V*C out

C out = Q * C in / (Q + k*V)

= 50*100/(50+0.216*500)

= 31.65 mg/L

Part b

After t = 0

Accumulation = input - output - consumption

VdC/dt = 0 - QC - kCV

After integration

Ct /C in = exp [(-Q/V + k)t]

Ct = 100 x exp[(-50/500 + 0.216)*5]

= 20.597 mg/L

Related Questions

Navigate

• Browse (All)
• Browse 2
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.