The regenerated (“lean”) solvent from the bottom of the stripper is cooled and
circulated back to the CO 2 absorber for reuse. Small amounts of makeup water or
solvent may be needed to cover losses or a small water purge may be necessary to
avoid accumulation. Water balance and solvent purity must be controlled within
limits.
Key operating conditions for a solvent CO 2 removal system depend on the
solvent used, so are not listed here. A methanator will normally operate in the
200–300 psig range with temperatures from 600 to 700
F inlet and 700–800
F
outlet. The temperature rise in the methanator will be about 130
F per v% CO in
the methanator feed and about 108
F per v% CO 2 in the methanator feed.
Overall Hydrogen Plant Reaction
For material balance, catalyst activity monitoring, and process control purposes, it
is helpful to look at the overall hydrogen plant reaction equation. The overall
equation for an SMR hydrogen plant is
CH 2α 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
(20)
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
This equation allows you to calculate the composition of the wet gas at any point
in the process from the SMR furnace inlet to the final shift outlet, as well as the
composition at the methanator outlet – given a few of the gas analyses in the
system. You can assume equilibrium (or some temperature difference from equilibrium) and use the K p value tables. The calculation will be iterative. There is more
about this under “Operations and Monitoring.”
Another useful view of steam-methane reforming is presented in Figs. 7, 8, 9, 10,
11, and 12, based on information in Catalyst Handbook (by Katalco, SpringerVerlag, NY, 1970). These charts show how the various reactions involved in steammethane reforming are interrelated to reach the final product. The values from the
charts are only approximate, but can be used to help calculate wet gas compositions
at the reformer outlet.
There are separate charts for reformer outlet methane, CO, and CO 2 from
reforming of both gases (methane) and liquids (naphtha). The methane charts
would apply when 2α in Eq. 20 is greater than about 2.5 (butane and lighter).
When 2α is less than 2.5 (pentane and heavier), the naphtha charts can be used.
Hydrogen Production and Management for Petroleum Processing
587
circulated back to the CO 2 absorber for reuse. Small amounts of makeup water or
solvent may be needed to cover losses or a small water purge may be necessary to
avoid accumulation. Water balance and solvent purity must be controlled within
limits.
Key operating conditions for a solvent CO 2 removal system depend on the
solvent used, so are not listed here. A methanator will normally operate in the
200–300 psig range with temperatures from 600 to 700
F inlet and 700–800
F
outlet. The temperature rise in the methanator will be about 130
F per v% CO in
the methanator feed and about 108
F per v% CO 2 in the methanator feed.
Overall Hydrogen Plant Reaction
For material balance, catalyst activity monitoring, and process control purposes, it
is helpful to look at the overall hydrogen plant reaction equation. The overall
equation for an SMR hydrogen plant is
CH 2α 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
(20)
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
This equation allows you to calculate the composition of the wet gas at any point
in the process from the SMR furnace inlet to the final shift outlet, as well as the
composition at the methanator outlet – given a few of the gas analyses in the
system. You can assume equilibrium (or some temperature difference from equilibrium) and use the K p value tables. The calculation will be iterative. There is more
about this under “Operations and Monitoring.”
Another useful view of steam-methane reforming is presented in Figs. 7, 8, 9, 10,
11, and 12, based on information in Catalyst Handbook (by Katalco, SpringerVerlag, NY, 1970). These charts show how the various reactions involved in steammethane reforming are interrelated to reach the final product. The values from the
charts are only approximate, but can be used to help calculate wet gas compositions
at the reformer outlet.
There are separate charts for reformer outlet methane, CO, and CO 2 from
reforming of both gases (methane) and liquids (naphtha). The methane charts
would apply when 2α in Eq. 20 is greater than about 2.5 (butane and lighter).
When 2α is less than 2.5 (pentane and heavier), the naphtha charts can be used.
Hydrogen Production and Management for Petroleum Processing
587