Methanation:
CO g
ð Þ þ 3H 2 g
ð Þ ! CH 4 g
ð Þ þ H 2 O g
ð Þ þ heat
(19)
Table 4 provides a summary of the wet chemical/solvent processes that are
available for hydrogen purification, along with a few comparison notes. Some of the
processes employ simple chemical solvents. Some use physical solvents. Some use
combined chemical and physical solvents. Some of these processes may be patented
or involve proprietary information.
Most of these processes offer an option that is not readily available in a PSA
system: i.e., food-grade carbon dioxide is a by-product of the process. This CO 2
product can be sold to help offset operating costs. This has some advantage in the
current drive to reduce greenhouse gas emissions.
Figure 6 provides a typical flow sheet for a wet chemical/solvent system of
hydrogen purification. An amine-type system is used in this example since these are
the most common. Individual processes and units may deviate from this flow, but
the general principles are the same.
In the wet chemical/solvent approach, cool, raw hydrogen is sent to an absorber
where the CO 2 is removed by a circulating solvent. The scrubbed hydrogen, with
residual CO and saturated with water, is heated and sent through a fixed-bed
methanation reactor (methanator). The catalyst in the reactor is a high nickel
oxide material, in a reduced form. The CO is converted almost quantitatively to
methane according to Eq. 19 above, consuming some of the hydrogen. Note that
methanation is really just undoing the reaction we performed in the SMR furnace,
and it will release just as much heat – although from much less reactant.
Table 4 Typical SMR hydrogen plant CO 2 removal solvents (Reference: Benamor (2012)
Carbon capture and Storage . . ., Gas Processing Center, Qatar University)
Removal system type and technology
Licensor/Supplier
Amine solvent systems
Monoethanolamine (MEA)
Fluor (Econamine
SM )
Diglycolamine (DGA)
Fluor (Econamine
SM )
Methyldiethanolamine (MDEA)
Jefftreat
Huntsman
Gas/Spec CS-2000
Ineos
BASF aMDEA (MDEA + Accel)
BASF
ADIP-X (MDEA + Accel)
Shell
Ucarsol
Dow
KM CDR (KS-1 hindered amine)
Mitsubishi Hvy Ind
Hot potassium carbonate systems
Catacarb and LRS-10
Eickmeyer and assoc
Benfield and Benfield ACT-1
UOP
Physical solvents
Selexol
UOP/Dow
Mixed solvents
Hydrogen Production and Management for Petroleum Processing
585
CO g
ð Þ þ 3H 2 g
ð Þ ! CH 4 g
ð Þ þ H 2 O g
ð Þ þ heat
(19)
Table 4 provides a summary of the wet chemical/solvent processes that are
available for hydrogen purification, along with a few comparison notes. Some of the
processes employ simple chemical solvents. Some use physical solvents. Some use
combined chemical and physical solvents. Some of these processes may be patented
or involve proprietary information.
Most of these processes offer an option that is not readily available in a PSA
system: i.e., food-grade carbon dioxide is a by-product of the process. This CO 2
product can be sold to help offset operating costs. This has some advantage in the
current drive to reduce greenhouse gas emissions.
Figure 6 provides a typical flow sheet for a wet chemical/solvent system of
hydrogen purification. An amine-type system is used in this example since these are
the most common. Individual processes and units may deviate from this flow, but
the general principles are the same.
In the wet chemical/solvent approach, cool, raw hydrogen is sent to an absorber
where the CO 2 is removed by a circulating solvent. The scrubbed hydrogen, with
residual CO and saturated with water, is heated and sent through a fixed-bed
methanation reactor (methanator). The catalyst in the reactor is a high nickel
oxide material, in a reduced form. The CO is converted almost quantitatively to
methane according to Eq. 19 above, consuming some of the hydrogen. Note that
methanation is really just undoing the reaction we performed in the SMR furnace,
and it will release just as much heat – although from much less reactant.
Table 4 Typical SMR hydrogen plant CO 2 removal solvents (Reference: Benamor (2012)
Carbon capture and Storage . . ., Gas Processing Center, Qatar University)
Removal system type and technology
Licensor/Supplier
Amine solvent systems
Monoethanolamine (MEA)
Fluor (Econamine
SM )
Diglycolamine (DGA)
Fluor (Econamine
SM )
Methyldiethanolamine (MDEA)
Jefftreat
Huntsman
Gas/Spec CS-2000
Ineos
BASF aMDEA (MDEA + Accel)
BASF
ADIP-X (MDEA + Accel)
Shell
Ucarsol
Dow
KM CDR (KS-1 hindered amine)
Mitsubishi Hvy Ind
Hot potassium carbonate systems
Catacarb and LRS-10
Eickmeyer and assoc
Benfield and Benfield ACT-1
UOP
Physical solvents
Selexol
UOP/Dow
Mixed solvents
Hydrogen Production and Management for Petroleum Processing
585