Chemical engineering

CBEE 212 Winter 2018 Written HW 7 Due in Studio Tuesday March 6

Hydrogen (H2) shows great promise as an energy source to replace petroleum-based fuels such as gasoline, which will be depleted in the next few decades. Hydrogen can be produced by steam reforming of propane: C3H8(g) + 3 H2O(v) → 3 CO(g) + 7 H2(g) (Reaction 1) In the presence of a catalyst, hydrogen can also be produced from the “water-gas shift reaction”: CO(g) + H2O(v) → CO2(g) + H2(g) (Reaction 2) The process is carried out over a nickel catalyst in a “shell-and-tube” reactor, as shown below. 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 a hot gas 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 the heat capacity of the heating gas is 0.040 kJ/(mol∙°C).

Feed gas @ 125 °C

nC3H8,f C3H8(g)

nH2O,f H2O(v)

nC3H8 C3H8(g)

nH2O H2O(v)

nCO CO(g)

nCO2 CO2(g)

nH2 H2(g)

Products @ 800 °C

ngas = 4.94 m3/ mol C3H8