H2Tech - Q2 2021 - 27

PATHWAYS FOR SUSTAINABLE HYDROGEN
Finally, the low-pressure CO2 product requires drying and
multistage compression or liquefaction to be transport-ready.
For end-users that want gas-phase CO2 and are long on steam,
an amine unit is a reliable, proven choice for CO2 recovery, albeit at a higher cost of capture than tail gas recovery (TABLE 2).
In all cases, the composition of the fuel gas recycled to the
SMR furnace is significantly altered. As a result, burner revamp
is required. CO2 removal from the fuel gas requires advanced
burner technology for stability and to achieve low NOx emissions. Advanced burners are customized to the furnace licensor's specifications and can be revamped to enable low-carbonintensity H2 production, including the ability to rapidly switch
between multiple fuels in the event the CO2 system is bypassed.
Adding any of the three pre-combustion CO2 removal technologies discussed to a conventional SMR unit will reduce
emissions by up to 60%. For a typical refinery SMR producing
100 ktpy of H2 (125 MMsft3d), up to 520 ktpy of CO2 can be
captured, which is enough to make a significant impact in many
near-term CO2 reduction pledges.
To further reduce emissions, CO2 must be eliminated from
the furnace flue gas. Two options exist to reduce flue gas emissions:
1. Solvent-based post-combustion CO2 absorption
2. SMR revamp options to minimize furnace firing
and use of an H2-rich fuel.
The flue gas stream is the most expensive stream to scrub CO2
due to the low pressure and low concentration. Current bestin-class solvent technology for flue gas capture results in costs
2-4 times more per metric t of CO2 captured than pre-combustion capture due to the low CO2 partial pressure and solvent
degradation. To reduce the cost of SMR flue gas CO2 capture,
advanced solvents with high solvent stability, improved mass
transfer properties, and low heat of regeneration are needed.
Flue gas emissions also can be reduced through SMR revamp options that minimize furnace firing and use of an H2-rich
fuel. Several options can result in greater than 90% CO2 capture
without the need for expensive post-combustion capture. These
options include operating the reformer at high methane conversion in a pre-reformer, a primary reformer and, optionally, a secondary gas heated reformer in series or in parallel; eliminating
excess steam export; using a structured catalyst insert; adding
low-temperature water-gas shift to minimize CO content in the
shifted syngas; removing the pre-combustion CO2 from either
the syngas or the tail gas, and diverting a slipstream of H2-rich
fuel to the furnace.5 These revamp options to minimize furnace
firing may be invasive for existing assets, but this type of optimized SMR design that concentrates CO2 for pre-combustion
capture is expected to play a significant role for new assets.
SMR retrofit financials. For low-carbon-intensity H2 projects

to be viable, government policy must provide a business case
for investment-which can come in the form of funding, incentives, trading schemes, credits and even taxes on CO2. Recently, CO2 price structures, national decarbonization strategies, and public- and private-sector investments in clean energy
have been seen globally.
Now is an active time for CCS in the U.S. because of the enhanced 45Q federal tax credit signed into law in 2018, with the
IRS issuing final guidance in August 2020. The final guidance

SPECIAL FOCUS

provides the clarity and assurance that CCS developers and investors need to move beyond the preliminary stage. The tax
credit provides up to $35/t of CO2 for enhanced oil recovery
(EOR) and $50/t of CO2 for permanent geological storage for
CO2 captured in facilities that meet thresholds in terms of size,
and where construction begins by the end of 2025.
Another example is in the EU, where the Emissions Trading System (ETS), a cap-and-trade scheme, saw CO2 prices rise
to more than €40/t ($48/t) in Q1 2021. These carbon prices
are sufficient to make blue H2 projects commercially attractive
today. TABLE 3 shows that retrofitting an SMR with cryogenic
fractionation on tail gas can provide solid payback in both the
U.S. and EU.
New blue H2 as fuel plants. Growth in H2 demand is expected
to come largely from its use as a CO2-free energy source to partially displace natural gas for heat and power in industrial and
Flue gas

Shifted
syngas

Natural gas
Water

Export steam

SMR

Solvent absorption
system

Air

H2 PSA
Tail
gas

CO2 to drying and compression

FIG. 3. SMR retrofit CO2 capture option 3.

TABLE 3. Example ﬁnancials for viable SMR retroﬁt projects
Cost of CO2 captured, $/t

U.S.

Utility cost

-21

-45

Fixed cost (maintenance and overhead)

-11

Annualized capital cost

-18

Net cost of carbon captured

-22

-37

CO2 transport and storage

-10

CO2 price

482

Net value

Carbon capture plant costs

Product values
Value of 10% additional H2 recovery
Total

Basis: Negative values are costs and positive values are revenues on $/t CO2 basis
U.S.: $3/GJ (LHV) natural gas price; $1.35/kg H2 value
EU: $6.6/GJ (LHV) natural gas price; $1.8/kg H2 value
1
Tax credit in U.S. under IRC Section 45Q for carbon captured in permanent
geological storage
2
EU allowance unit trading at €40/t CO2 in Q1 2021

TABLE 4. Selected H2 purity speciﬁcations by end use
For reﬁning and For natural gas
chemical
pipeline
H2 purity

For fuel cells

99.9+%

98%

99.97%

CO, max ppmv

0.2

CH4, max ppmv

100

O2, max ppmv

2,000

5
H2Tech | Q2 2021

H2Tech - Q2 2021

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