A gas containing water vapor has a dry-basis composition of 7.5 mole% CO, 11.5% CO2

Chapter 8, Problem 8.35

(choose chapter or problem)

A gas containing water vapor has a dry-basis composition of 7.5 mole% CO, 11.5% CO2, 0.5% O2, and 80.5% N2. The gas leaves a catalyst regeneration unit at 620C and 1 atm with a dew point of 57C at a flow rate of 28.5 SCMH [m3 (STP)/h]. Valuable solid catalyst particles entrained in the gas are to be recovered in an electrostatic precipitator, but the gas must first be cooled to 425C to prevent damage to the precipitator electrodes. The cooling is accomplished by spraying water at 20C into the gas. (a) Use simultaneous material and energy balances on the spray cooler to calculate the required water feed rate (kg/h). Treat the spray cooler as adiabatic and neglect the heat transferred from the entrained solid particles as they cool. (b) In terms that a high school senior could understand, explain the operation of the spray cooler in this problem. (What happens when the cold water contacts the hot gas?)