remedies. This table is by no means all-inclusive, but can be used as a starting point
for troubleshooting.
SMR Process Flow Sheet Variations
The foregoing section described the most common, and simplest, process flow
sheet for carrying out steam-methane reforming with a couple of minor variations
in the product hydrogen purification system. There are other process variations in
commercial operation. These are less common, but may be encountered or
considered for a specific plant. Some variations may be helpful in debottlenecking
or production rate increases. The three most common variations are briefly
described below.
Pre-reforming
A pre-reformer is a fixed-bed reactor installed upstream of the main SMR reforming
furnace. The pre-reformer performs the cracking part of the reactions (Eq. 8) and
does some minor reforming. At the pre-reformer outlet, the feedstock has been
converted to essentially all methane for the SMR furnace. This enables the furnace
tube volume to be devoted to the SMR reaction.
A pre-reformer also acts as a guard bed for the main reforming catalyst; it takes
any impacts from poisoning and protects the furnace catalyst. Pre-reformers can
often be taken off-line and changed out, while the main process continues, albeit
with an easier feed during the changeout. Pre-reformer catalyst is permanently
deactivated by sulfur, chlorine, and other poisons. The pre-reformer helps open up
the possible feedstocks for a hydrogen plant and levels out feedstock variations.
Heat is supplied to the pre-reformer by replacing one of the convection steam
generation coils with a pre-reformer preheat coil. This means less steam generation
from the plant, but improves hydrogen production efficiency.
Some process designers like to always include a pre-reformer in their flow sheet.
Others offer pre-reforming as an option or for increasing rate. Addition of a
pre-reformer to an existing hydrogen plant can enable it to make about 10–20 %
more hydrogen and use a lower steam/carbon ratio. The shift cooling and product
purification systems still need to have enough capacity to handle the incremental
raw hydrogen produced, so some additional debottlenecking may be required.
This technology is offered by Haldor Topsoe, ThyssenKrupp Uhde (Uhde),
CB&I/HoweBaker, Technip, Kellogg Brown & Root (KBR), and others.
Exchanger Reforming/Post-Reforming
An exchanger reformer uses waste heat from the SMR furnace to reform additional
feed and make more hydrogen. The post-reformer is usually an exchanger with
catalyst-packed tubes. Heat is supplied by waste heat in the SMR furnace effluent or
convection section at the expense of steam generation.
Hydrogen Production and Management for Petroleum Processing
617
for troubleshooting.
SMR Process Flow Sheet Variations
The foregoing section described the most common, and simplest, process flow
sheet for carrying out steam-methane reforming with a couple of minor variations
in the product hydrogen purification system. There are other process variations in
commercial operation. These are less common, but may be encountered or
considered for a specific plant. Some variations may be helpful in debottlenecking
or production rate increases. The three most common variations are briefly
described below.
Pre-reforming
A pre-reformer is a fixed-bed reactor installed upstream of the main SMR reforming
furnace. The pre-reformer performs the cracking part of the reactions (Eq. 8) and
does some minor reforming. At the pre-reformer outlet, the feedstock has been
converted to essentially all methane for the SMR furnace. This enables the furnace
tube volume to be devoted to the SMR reaction.
A pre-reformer also acts as a guard bed for the main reforming catalyst; it takes
any impacts from poisoning and protects the furnace catalyst. Pre-reformers can
often be taken off-line and changed out, while the main process continues, albeit
with an easier feed during the changeout. Pre-reformer catalyst is permanently
deactivated by sulfur, chlorine, and other poisons. The pre-reformer helps open up
the possible feedstocks for a hydrogen plant and levels out feedstock variations.
Heat is supplied to the pre-reformer by replacing one of the convection steam
generation coils with a pre-reformer preheat coil. This means less steam generation
from the plant, but improves hydrogen production efficiency.
Some process designers like to always include a pre-reformer in their flow sheet.
Others offer pre-reforming as an option or for increasing rate. Addition of a
pre-reformer to an existing hydrogen plant can enable it to make about 10–20 %
more hydrogen and use a lower steam/carbon ratio. The shift cooling and product
purification systems still need to have enough capacity to handle the incremental
raw hydrogen produced, so some additional debottlenecking may be required.
This technology is offered by Haldor Topsoe, ThyssenKrupp Uhde (Uhde),
CB&I/HoweBaker, Technip, Kellogg Brown & Root (KBR), and others.
Exchanger Reforming/Post-Reforming
An exchanger reformer uses waste heat from the SMR furnace to reform additional
feed and make more hydrogen. The post-reformer is usually an exchanger with
catalyst-packed tubes. Heat is supplied by waste heat in the SMR furnace effluent or
convection section at the expense of steam generation.
Hydrogen Production and Management for Petroleum Processing
617