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FEATURE
A D V A N C E D M A T E R I A L S & P R O C E S S E S | N O V E M B E R / D E C E M B E R 2 0 1 5
6 4
8
The overall reforming reactions are endothermic (re-
quire heat), which is supplied by the combustion of fuel. Tail
gas from the pressure swing adsorption (PSA) systemmeets
most of the fuel requirement with the rest being supplied by
natural gas.
The hydrogen-rich stream is purified using pressure
swing adsorption. PSA is a physical process that depends on
selective physical binding of gas molecules. Hydrogen is es-
sentially not adsorbed by the proprietary adsorbent materi-
al, amixture of carbonmolecular sieve and zeolites, because
it is nonpolar and highly volatile. The system operates on a
repeated cycle consisting of two basic steps: adsorption and
regeneration. Regeneration consists of depressuring, purg-
ing, and repressuring.
PLANT DESIGN
Inputs to the modular plant are natural gas, demin-
eralized water, and electric power. Outputs are high purity,
gaseous H
2
. There is no export steam. This plant produces H
2
with the following specifications:
•
Flow rate: 165-330 Nm
3
/h
•
Purity: 99.999+%
•
Pressure: 13.8 barg
The plant is designed to be easily shipped all over
the world. It can be hauled on a flatbed truck, thereby
simplifying logistics and transportation. Figure 4 shows a
14 m long by 3 m wide by 4 m high partly assembled plant
module in transit.
Plants are heat integrated for high thermal effi-
ciency. Typical operating characteristics for a 330 Nm
3
/h
(0.3 MMSCFD) plant are:
Operating parameter
H
2
capacity, Nm
3
/h
330
H
2
purity, %
99.999
CO + CO
2
, ppm
<1
Pressure, barg
13.8
Natural gas /H
2
MM cal/Nm
3
H
2
(HHV)
4.4
Power, kW
60
Demineralized water, kg/h
550
These resultswere achieved in actual commercial oper-
ation over an extended time.
Advantages of the Hydroprime plants include:
•
Simple, quick site installation
•
Outdoor installation
•
Excellent accessibility for maintenance
•
Small footprint
The plants are standardized with fully automatic fail-
safe controls, allowing unattended operation with remote
start-up and 24/7monitoring. This enables quick response to
Fig. 3 —
Flow diagram of steammethane reforming (SMR) process.