Two streams containing pyridine and acetic acid at 25C are mixed and fed into a heat exchanger.

Question:

Two streams containing pyridine and acetic acid at 25°C are mixed and fed into a heat exchanger. Due to the heat-of-mixing effect, it is desired to reduce the temperature after mixing to 25°C using a stream of chilled ethylene glycol as indicated in the diagram. Calculate the mass flow rate of ethylene glycol needed. The heat capacity of ethylene glycol at these conditions is approximately 2.8 kJ/(kg K), and the enthalpy change of mixing (Δ_mixH) is given below.

Pyridine 1 kmol/min T = 25C Acetic acid 1 kmol/min T = 25C Ethylene glycol T = 25 C Pyridine + acetic acid 2

Data: Heat of mixing for pyridine (C₅H₅N) and acetic acid at 25°C [H. Kehlen, F. Herold and H.- J. Rademacher, Z. Phys. Chem. (Leipzig), 261, 809 (1980)].

Pyridine Mole Fraction 0.0371 0.0716 0.1032 0.1340 0.1625 0.1896 0.2190 0.2494 0.2760 0.3006 0.3234 0.3461