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/lye phase separator
Puri er
Water feed
Regenerative twin bed dryer
Gas/lye phase separator
KOH management
Lye tank
Control valve
Pressurised alkaline electrolysis stack
+
–
Cooling water
H
Gas purity analysis
Recirculation pump
Filter
DC
Electricity
Fresh KOH
AC
Recti er Transformer
Figure 3 Pressurised alkaline electrolysis process
scheme. To put this into context, the power management system involving the transformer and rectifier to convert grid, wind, or hydropower to be suitable DC electricity for the electrolyser would be around 20%. Cooling water and balance of plant power Electrolysers are approximately 70% efficient when they convert power to hydrogen. The
wasted power generates heat which is generally dissipated on a cooling tower. A typical cooling tower will need about 2% of the daily recirculated cooling water volume to be topped up due to evaporation losses (see Figure 3 ). The pumps that recirculate the cooling water, drive the cooling tower fans, and recirculate the electrolyte around alkaline electrolysers all consume power. However, the power demand
Condenser
Water feed
Preheater
Steam superheater
Syngas CO/H
Water outlet
Sweep air feed
Oxygen heat recovery
Vapouriser
Compressor
Air & oxygen exhaust
Expander
SOE stack + –
CO feed
Recti er
Transformer
AC
Electricity
DC
Figure 4 Solid oxide CO-electrolysis process for syngas generation
www.decarbonisationtechnology.com
24
Powered by FlippingBook