moisture in the feed. Use these values to calculate alpha (α) for use in Eq. 20.
In this case, we have 816.2 mols of carbon per hour and 3,105.5 mols
hydrogen per hour:
2α ¼ 3, 105:5=816:2 ¼ 3:80
α ¼ 3:80=2 ¼ 1:90
4. Calculate the steam/carbon ratio (X) at the reformer inlet by converting the
steam rate to moles per hour and dividing it by the moles per hour of carbon:
66,500 lb/h steam/18 = 3694.4 mols/h steam
Steam/Carbon = 3694.4/816.2 = 4.53 S/C Ratio = X
5. Calculate the wet shift converter outlet composition using the following
equation and knowing α and X from above. The methane, CO, and CO 2
proportions (1-a-b, a, and b) come from the PSA inlet dry gas. The steam
portion is calculated from the equation. Hydrogen falls out in the calculation. Remember that the nitrogen will come through as an inert:
CH 2 α þ XH 2 O ! aCO þ bCO 2 þ 1 À a À b
ð
Þ CH 4
þ X À a À 2b
ð
Þ H 2 O þ 3a þ 4b þ α À 2
ð
Þ H 2
(31)
where
α = factor based on feed C/H molar ratio
X = steam/carbon molar ratio
a, b = coefficients for CO and CO 2 concentrations, respectively, at any point
in the process
6. The shift or process condensate should be the residual water from the
reaction. Use this as the process condensate flow rate. You can include
dissolved CO 2 , but the amount of dissolved CO 2 is not significant in the
overall process.
7. Now check the overall balance in the unit by adding the feeds (feed gas plus
steam plus any recycle hydrogen) and comparing to the HTSC outlet (PSA
inlet gas plus calculated process condensate). Check the carbon and hydrogen balances also. Make adjustments to flow rates until you closed the
balance. This sometimes means compromising on rates or slight adjustments
to compositions. There are many sources of possible error in these calculations so flexibility is needed. If the balance can be closed to +/À2 %, that is
good enough for the analysis.
8. Now estimate the reformer outlet composition.
• Assume the HTSC outlet (in moles) is the correct methane slip from the
reforming furnace. Here the slip is 2.5 v% of the dry gas or about
87 mols/h.
• Calculate the CO and CO 2 proportions by assuming the gas is at watergas shift equilibrium at the reformer outlet. The CO and CO 2 proportions
can be derived by iteration until the calculated K WGS at the reformer
Hydrogen Production and Management for Petroleum Processing
641
In this case, we have 816.2 mols of carbon per hour and 3,105.5 mols
hydrogen per hour:
2α ¼ 3, 105:5=816:2 ¼ 3:80
α ¼ 3:80=2 ¼ 1:90
4. Calculate the steam/carbon ratio (X) at the reformer inlet by converting the
steam rate to moles per hour and dividing it by the moles per hour of carbon:
66,500 lb/h steam/18 = 3694.4 mols/h steam
Steam/Carbon = 3694.4/816.2 = 4.53 S/C Ratio = X
5. Calculate the wet shift converter outlet composition using the following
equation and knowing α and X from above. The methane, CO, and CO 2
proportions (1-a-b, a, and b) come from the PSA inlet dry gas. The steam
portion is calculated from the equation. Hydrogen falls out in the calculation. Remember that the nitrogen will come through as an inert:
CH 2 α þ XH 2 O ! aCO þ bCO 2 þ 1 À a À b
ð
Þ CH 4
þ X À a À 2b
ð
Þ H 2 O þ 3a þ 4b þ α À 2
ð
Þ H 2
(31)
where
α = factor based on feed C/H molar ratio
X = steam/carbon molar ratio
a, b = coefficients for CO and CO 2 concentrations, respectively, at any point
in the process
6. The shift or process condensate should be the residual water from the
reaction. Use this as the process condensate flow rate. You can include
dissolved CO 2 , but the amount of dissolved CO 2 is not significant in the
overall process.
7. Now check the overall balance in the unit by adding the feeds (feed gas plus
steam plus any recycle hydrogen) and comparing to the HTSC outlet (PSA
inlet gas plus calculated process condensate). Check the carbon and hydrogen balances also. Make adjustments to flow rates until you closed the
balance. This sometimes means compromising on rates or slight adjustments
to compositions. There are many sources of possible error in these calculations so flexibility is needed. If the balance can be closed to +/À2 %, that is
good enough for the analysis.
8. Now estimate the reformer outlet composition.
• Assume the HTSC outlet (in moles) is the correct methane slip from the
reforming furnace. Here the slip is 2.5 v% of the dry gas or about
87 mols/h.
• Calculate the CO and CO 2 proportions by assuming the gas is at watergas shift equilibrium at the reformer outlet. The CO and CO 2 proportions
can be derived by iteration until the calculated K WGS at the reformer
Hydrogen Production and Management for Petroleum Processing
641