H2Tech - Q4 2021 - 37

INFRASTRUCTURE AND DISTRIBUTION
H2 value chain analysis comparing
different transport vectors-Part 2
N. CHODOROWSKA and M. FARHADI, Wood, Reading, UK
Part 1 of this article, published in the
Q3 issue, introduced the study concept
and methodology for examining four
transportation vectors to convert natural
gas from Ras Laffan Industrial City
in northeast Qatar into an H2
product
at South Hook LNG terminal in Milford
Haven, West Wales, UK. The value chain
for each option was defined, and CAPEX
and OPEX were calculated for each
unit within the process. Part 2 considers
H2
production with carbon capture and
the LNG value chain.
H2
production with carbon capture.
H2 production for all four options is
based on steam methane reforming
(SMR) technology. SMR was selected
based on the availability of in-house information
and the desire to have comparative
options. H2
of syngas generation, CO2
H2
production consists
removal and
extraction.
Syngas generation technologies include
SMR, autothermal reforming
(ATR) and partial oxidation (POX)
with a gas-heated reformer (GHR) for
additional efficiency. CO2
removal is
based on an amine system, which is a
mature technology. H2
extraction technologies
include pressure swing adsorption
(PSA) and membranes. PSAs are
proven technology producing higherpurity
products.
Blue H2
mizing the quantity of CO2
production focuses on minireleased
to
the atmosphere when a hydrocarbon
feedstock is used to produce the H2
authors' company's blue H2
nology targets > 90% CO2
simplified process diagram is shown in
FIG. 3.10
H2 production block in the comparison.
. The
SMR techcapture.
A
The process flow diagram in FIG. 4
production process and includes the
shows the unit processes required in the
H2
Treated natural gas initially mixes
with an H2 recycle from the downstream
process, including boiloff gas (BOG)
from storage, and then passes through
a feed preheater. The heated desulfurized
gas mixes with steam and passes
through the prereformer. In the prereformer,
higher-chain hydrocarbons are
converted into methane (CH4
carbon monoxide (CO) and H2
), CO2
. Addi,
tional
steam is injected into the gas leaving
the prereformer underflow control to
maintain the correct steam/carbon ratio
for the reforming process.
The process gas then enters the
gas heated reformer (GHR). In the
GHR, methane is partially converted
to H2
and CO in an endothermic reaction.
The reforming in the GHR means
that the advanced Terrace Wall steam
reformer (TWR) does not require supplemental
fuel gas firing compared to a
traditional SMR.
The reforming reaction is
endothermic and requires high process
temperatures to favor greater equilibrium
concentrations of CO and H2
gas shift reaction.
After the shift reactors, the syngas
is further cooled before it is sent to the
amine unit, where the CO2
is removed.
The syngas product leaving the amine
unit is then divided into two streams:
one stream is sent to the TWR furnace as
FIG. 3. Blue H2
process block.
a fuel gas for heating the catalyst tubes,
and the second stream is sent to the PSA
unit. The H2
is separated from the syngas
in the PSA absorbent, and the residual
tail gas is also sent as a fuel providing
supplemental firing of the reformer furnace,
if required. From the PSA unit, the
H2
is separated
from this stream to be recycled to the
front of the process underflow control to
be mixed with the incoming feed gas.
The CO2
leaving the amine unit is the
final product for three of the options.
This stream needs to be dehydrated and
compressed for reinjection into offshore
wells. These costs are not included in the
study comparison.
For the LNG value chain, the CO2
strongly
. The
syngas then passes through the shift reactors,
where the CO present in the syngas
is " shifted " to CO2
through the waterleaving
the amine unit is compressed and
liquefied for transport to Qatar; once
returned, it is sent for reinjection into
offshore wells. These costs are considered
in this study. Returning the CO2
to
Qatar is the most conservative approach,
although sequestration closer to the improduct
stream is sent to the battery
limit (BL). Some of the H2
FIG. 4. SMR + CCS process block diagram.
H2Tech | Q4 2021 37
H2Tech - Q4 2021

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