Question

A process to remove contaminant A includes two independent pipes flowing into a cylindrical reactor, and a single outlet port. The reactor has a diameter of 2.8 m and a height of 2 m. The flow in the larger of the inlet pipes is 2.5 m3/s and contains 50 μg/L of A. The smaller pipe also carries contaminant A at a rate of 5x104 μg/s. Under these conditions, the reactor’s outlet flow is 3.25 m3/s. Assuming that the removal of contaminant A follows first-order kinetics (k = 0.35 s-1): a) Sketch the described process and write a mass-balance equation for contaminant A around the entire control volume assuming the reactor behaves as an ideal CSTR. Calculate the steady-state concentration of A in the reactor, in μg/L. Answer: C=23.2 µg/m3 b) Calculate the flow and concentration of A in the smaller pipe, in m3/s and μg/L, respectively. c) If the smaller pipe inlet valve is suddenly closed so that its flow into the reactor is completely stopped, what is the new steady-state concentration of A in the reactor, in μg/L? Answer: C =18.4 µg/m3 d) How long does it take the contaminant A concentration to regain steady-state condition after this change? Express answer in seconds. Answer: t = 53.8 s

Answer 1