Question

A gas containing water vapor has a dry-basis composition of 7.5 mole% CO, 1 1.5% CO2, 0.5%。2, and 80.5% N2. The gas leaves a catalyst regeneration unit at 620°C and i atm with a dew point of 57°C at a flow rate of 28.5 SCMH [m(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 425°C to prevent damage to the precipitator electrodes. The cooling is accomplished by spraying water at 20°C 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?)

Answer 1

A) required water feed rate is 2.63 kg/h

B) If cold water contacts hot gas, there will be transfer of heat from the hot gas to the cold water and this will decrease the temperature of the hot gas and increase the temperature of the cold water. Heat balance.

Step-by-step explanation:

See working to (A)