Pressure Electrolyser

Based on the LURGI System


Pressure electrolysis is a established process for the production of high-purity hydrogen and oxygen from water. This Process has – compared to atmospheric electrolysis – the advantage that the product gases are available at a pressure of 30 bar as generated. As a result the hydrogen and oxygen are directly usable for most applications an do not require any separate compression.


The design of the Lurgi System pressure electrolyser Systems is distinguished by advance engineering, high reliability, convenient operation and a long life span. They are backed by decades of experience in the construction an commissioning of pressure electrolysis plants.

  • Bipolar Cells in filter-press type assembly
  • Electrodes made of steel with new galvanic protection activation and increase of the geometric and active electrode surface
  • Improved construction of the cell block parts like cell-frame, cell-plate and pre-electrodes. Designed for lower current resistance and increased active surface area. Produced without thermal and forming process related tension
  • Pressure process results in very compact equipment design. A large number of cells can be arranged in line and large quantities of hydrogen can generated in a single unit of low space requirements
  • Electrolyte used is 25% potassium hydroxide solution
  • Forced circulation of electrolyte provides for optimum heat dissipation an uniform electrolyte concentration in all cells
  • Separation of gas and electrolyte takes place in horizontal separators fitted with special internals to reduce aerosol level in product gases


The pressure electrolyser have many advantages that ensure a sophisticated and trouble-free hydrogen & oxygen production.

The major advantages are:

  • Pressure operation results in low specific energy consumption
  • Very low level of aerosols in product gases. Scrubbing of gases to clean them of KOH is not required
  • Hydrogen and oxygen are available at 30 bar pressure. No compressor required for storage and use of the product gases at this pressure, saving approx. 0,2 kWh/Nm3 H2 energy for compression
  • Capacities up to 1400 Nm3/h H2 accommodated in a single electrolyser, resulting in very small space requirements, low building construction costs and reduced maintenance expenditure
  • Easy and secure operation due to extensive automation
  • High availability of equipment together with extensive flexibility and long life
  • Convenient installation of factory-assembled cell blocks
  • Very high environmental compatibility. The only operating consumables required are water and electricity

Range of Supply

The pressure electrolysers are built in unit capacities of 200 to 1400 Nm3/h hydrogen output and 100 to 700 Nm3/h oxygen output. Larger capacities are readily obtained by operating a multiple number of units in parallel.

The capacity of the pressure electrolysers is matched to the given gas demand by just modifying the number of cells. These cells are factory-assembled as blocks of the 
required size.

ELB supplies the engineering and equipment for complete pressure electrolysis plants and undertakes on-site installation and commissioning. In addition to the electrolyser,  
The overall plant comprises:

  • Modern signaling and monitoring system
  • Transformer/Rectifier
  • Feed water system
  • Electrolyte station
  • Gas and electrolyte coolers

Auxiliary equipment to suit the intended use of the product hydrogen and oxygen is also available, including:

  • Catalytic gas purifiers for the production of highest purity H2 and O2 (residual impurities < 1 ppm)
  • Gas dryers to reduce residual moisture to dew points as low as -70°C
  • Gas compressors, for instance to deliver gas at bottling pressure (200 bar)
  • Gas bottling units and/or storage tanks


Operating Data

Hydrogen and oxygen are generated at a pressure of 30 bar.

Gas purities

Hydrogen:                      99,8 – 99,9 vol%
Oxygen:                         99,3 – 99,6 vol%

Residual impurities in product gases:
O2 in H2:                        0,1 – 0,2 vol%
H2 in O2:                        0,4 – 0,7 vol%
H2O:                                approx. 1 – 2 g/Nm3
KOH:                               < 10 mg/Nm3 H2

The product gases are free from CO, CO2, CH4 and sulphur or chlorine components.

Utilities consumption

Energy:                          4,3 – 4,65 kWh/Nm3 H2
(gas at 0°C, 1013 mbar, dry)

Feed water:                   0,85 l/Nm3 H2
Cooling water:              80 l/Nm3 H2

Gas production rate is variable between 25% and 100% of the nominal capacity on every electrolyser.


The pressure electrolysers are designed for many years of uninterrupted operation and are essentially free from maintenance requirements.

Plants now in service have been operating for more than 20 years without the cells having to be opened during the time.

ELB can offer you full after-sales services from inspections, maintenance support, qualified advices if any problems arise to optimisation of operating parameters.