H2Tech - Q3 2021 - 20

SPECIAL FOCUS HYDROGEN INFRASTRUCTURE DEVELOPMENT
medium-pressure steam is mixed at the inlet of the shift reactor,
operating with a steam/dry syngas ratio of at least of 1.5
to maintain the shift exit temperature below 480°C. Due to the
high CO content, a two-stage shift reaction is foreseen to properly
control any variation of CO content deriving from the heterogeneous
nature of waste.
CO + H2
O } CO2
+ H2
(1)
The resulting syngas is cooled through heat recovery and
cooling water, sent to a gas-liquid separator for condensate removal
and routed to a PSA unit. The latter unit allows for the
production of H2
is used as fuel in the auxiliary boiler.
A different approach may be adopted when CO2
required. The high partial pressure of CO2
at a purity of 99.99%, and the purge gas stream
capture is
in the cooled syngas
fed to the PSA allows a less energy-intensive capture compared
TABLE 2. Waste used for the case study (mixture of 50% RDF
and 50% PW)
Component, wet basis
C, wt%
H, wt%
O, wt%
N, wt%
S, wt%
Cl, wt%
Moisture, wt%
Inert, wt%
LHV, MJ/kg
ASU
O2+ N2
NG
Waste
HT-Gasification
and cleaning
Inert granulate
Sludge to
wastewater
treatment
Alkaline scrubber,
subcooling and WESP
Syngas storage
Syngas compression
HT-Gasification
and cleaning
HT-Gasification
and cleaning
Metals/chlorine
removal
Hydrolysis
COS (HCN)
Hg removal
H2S
removal
H2S
deep polishing
Condensate
Demineralized water
Fuel
FIG. 3. Waste-to-H2 block diagram.
20 Q3 2021 | H2-Tech.com
Auxiliary boiler
Flue gas
Purge
gas
Shift reaction
steps
PSA
H2
Gasification and preliminary gas cleaning
Syngas purification
Syngas conditioning
Value
41.7
6
19
0.7
0.2
1.1
13.5
17.8
17.9
H2 cost of production. To assess the economic feasibility of
the waste-to-H2
technology, an economic evaluation was carried
out to estimate CAPEX and OPEX. The overall CAPEX
was estimated at approximately €242 MM. A breakdown of relevant
costs is shown in TABLE 5.
To evaluate OPEX and the related H2
cost of production,
specific utilities costs have been assumed as outlined in TABLE 6.
On the basis of utilities consumption derived from heat and
material balance (TABLE 4), the OPEX has been estimated at approximately
€28 MM/y, with the breakdown shown in FIG. 4.
The resulting cost of production is strictly related to the waste
gate fee. By varying the gate fee from €130/t to €150/t, the resulting
H2
cost of production ranges from €0.102/Nm3
Nm3
emissions for waste-to-H2
to €0.083/
. These values are promising and competitive with the cost
of production of a conventional steam reforming process.
CO2
. For a better understanding of
the potential carbon footprint reduction of the proposed wasteto-H2
technology,
a simplified lifecycle assessment (LCA) analysis
was performed.
The use of waste as feedstock for chemical synthesis allows
for the simultaneous fulfillment of two different services: the
to CO2 capture of hot flue gas. The case study analyzed here is
based on a plant architecture without CO2
capture.
In the proposed architecture, three gasification lines are ad/y
of H2
. Heat and mateopted
with an overall capacity of approximately 192,000 tpy of
waste delivering around 200 MMNm3
rial balance for the proposed scheme were performed using a
proprietary simulation program. The key products and byproducts,
as well as utilities consumption, are shown in TABLE 4.
MP Steam
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