A gas stream containing 40.0 mole% hydrogen, 35.0% carbon monoxide, 20.0% carbon

Question

A gas stream containing 40.0 mole% hydrogen, 35.0% carbon monoxide, 20.0% carbon dioxide, and 5.0% methane is cooled from 1000°C to 10°C at a constant absolute pressure of 35.0 atm. Gas enters the cooler at 120 m3 /min and upon leaving the cooler is fed to an absorber, where it is contacted with refrigerated liquid methanol. The methanol is fed to the absorber at a molar flow rate 1.2 times that of the inlet gas and absorbs essentially all of the CO2, 98% of the methane, and none of the other components of the feed gas. The gas leaving the absorber, which is saturated with methanol at –12°C, is fed to a cross-country pipeline.

(a) Calculate the volumetric flow rate of methanol entering the absorber (m3 /min) and the molar flow rate of methanol in the gas leaving the absorber. Do not assume ideal gas behavior when doing PVT calculations.

Explanation / Answer

Calculate the volumetric flow rate of methanol entering the absorber (m3 /min) and the molar flow rate of methanol in the gas leaving the absorber. Do not assume ideal gas behavior when doing PVT calculations. Strategy • We will first do a degree-of-freedom analysis on the overall system to make sure we have enough information to determine the requested quantities (V! F ,n!G , y1 ). • Assuming we do, we will then use an equation of state to convert the volumetric flow rate of the feed stream (120 m3 /min) to a molar flow rate and the latter to the volumetric flow rate of the cooler outlet stream (V! F ). Since each stream is a mixture of species and Chapter 5 only presents one way to do PVT calculations for mixtures (the compressibility factor equation of state with Kay’s rule), we’ll use that one. • Finally, we’ll write and solve the equations listed in the DOF analysis. Solution (6.32-1) DEGREE-OF-FREEDOM ANALYSIS: OVERALL SYSTEM UNKNOWNS AND INFORMATION JUSTIFICATION/ CONCLUSION + 8 unknowns ________________ – 5 material balances ________________ – 1 eq. of state at cooler inlet Calculate _____ – 1 Raoult’s law for CH3OH Calculate _____ – 1 98% CH4 absorption ______________________ 0 DOF Problem is solvable

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.