Chapter 9, Problem 9.44P

Hydrogen is produced in the steam reforming of propane:

   $C_3{H}_8\left(g\right)+3H_{2}O\left(v\right)\to 3CO\left(g\right)+7H_2\left(g\right)$

The water-gas shift reaction also takes place in the reactor, leading to the formation of additional hydrogen: $CO\left(g\right)+H2O\left(v\right)\to C{O}_2\left(g\right)+H_2\left(g\right)$

The reaction is carried out over a nickel catalyst in the tubes of a shell-and-tube reactor. The feed to the reactor contains steam and propane in a 6:1 molar ratio at 125°C, and the products emerge at 800°C. The excess steam in the feed assures essentially complete consumption of the propane. Heat is added to the reaction mixture by passing the exhaust gas from a nearby boiler over the outside of the tubes that contain the catalyst. The gas is fed at 4.94 m³/mol C₃H₈, entering the unit at 1400°C and 1 atm and leaving at 900°C. The unit may be considered adiabatic.

Calculate the molar composition of the product gas, assuming that the heat capacity of the heating gas is 0.040 kJ/(mol·°C).

1. Is the reaction process exothermic or endothermic? Explain how you know. Then explain how running the reaction in a reactor-heat exchanger improves the process economy.