ASU
Compressor
Ostwald process HNO
NH NO
e-fertiliser
O
Air
Haber - Bosch
e-fuels
N
NH
Compressor
H
Syngas
Steam
Renewable
PEM/AEC
electricity
rWGS
Reverse
SOE
H O
CH OH
osmosis
O
Renewable electricity
Hydro power
CO
From ASU, PEM or a lkaline electrolysis today and SOE in the near future
DAC
Air
Formaldehyde
Sea
River
Figure 1 Air, water, and renewable electricity for integrated e-fuels, e-fertilisers, and e-chemicals production
membrane (PEM) system, that will probably not be a major issue, but for an alkaline system an unplanned shutdown may result in corrosion of the electrodes and a reduction in electrolysis efficiency during future operation (see Figure 2 ). The capital and operating costs of pure water supply are low, but the costs of failure are high: reliability is key. Water supply for a typical green
hydrogen scheme will generally be only 1 or 2% of the total operating cost. Impurities such as calcium ions in the water will rapidly damage a PEM electrolyser membrane due to the interaction with the catalyst coating. Alkaline electrolysers also have sensitivities to poisons in the water. The consequences of an impure water supply are unacceptable.
Safety gas analysis H in O
Safety gas analysis O in H
Condensate trap
O
Control valve
Cooling water
Demister
Demister
Catalytic de-oxo unit
Cooling water
Cooling water
Feed water pump
Gas/water phase separator
Puri er
Water feed
Regenerative twin bed dryer
Gas/water phase separator
PEM electrolysis stack
Control valve
+
–
Cooling water
H
Recirculation pump
Ion exchange
Gas purity analysis
DC
Electricity
AC
Recti er Transformer
Figure 2 Pressurised PEM electrolysis process
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