Question

A stream of methane is being separated from other petroleum products in a distillation column and exits the column at 215 degFand 2.2 atm. The flow rate of this gas is measured with an orifice meter and the calibration chart for the meter indicates that the flow rate is 1.5E+05 SCFH. Standard conditions used are 0 Celsius and 1 atm. Calculate the molar flow rate in lbmol/h and the true volumetric flow rate of the stream in m^3/h

Answer 1

Given: Standard Temperature, T₁=0⁰C=491.67 ⁰R

Standard Pressure, P₁=1 atm

Temperature of the exit stream, T₂=215⁰F=674.67 ⁰R

Pressure of the exit stream, P₂=2.2 atm

Flow rate of methane, ₁=1.5*10⁵ SCFH=1.5*10⁵ ft³(STP)/h

(SCFH is Standard Cubic Feet per Hour)

An ideal gas occupies 359 ft³(STP)/lb mol at standard conditions.

Molar flow rate of the methane stream, , is

True volumetric flow rate of the methane stream is obtained using the ideal gas law

where ₂ is the True volumetric flow rate of methane stream

P₁, ₁ and T₁ is the Pressure, volumetric flow rate and temperature, respectively, at standard conditions

P₂, T₂ is the Pressure and Temperature of the exit stream, respectively

is the Molar flow rate

R is the Gas constant

Thus the molar flow rate is =417.83 lbmol/h and true volumetric flow rate is ₂=9.36*10⁴ ft³/h