Low-pressure Electrolyser

Based on the BAMAG System


The electrolysis of water is a process for production of high purity hydrogen and oxygen Active in this field for over 80 years, BAMAG accumulated a rich fund of experience resulting from a total of more than 450 water electrolyser constructed and commissioned to date.

By having access to the know-how (and personnel) regarding the BAMAG type electrolyser, ELB is today qualified to supply electrolyser plants that will fulfil the highest demands. The advanced engineering of electrolyser according to the system BAMAG assures a high level of plant reliability and availability coupled with long life and low investment costs. This results in an optimum cost-to-benefit ratio.


The electrolyser are constructed as filter-press type units with bipolar cells. In order to reduce energy consumption, the electrodes are activated with a special method. Diaphragms may be made either of conventional material or of new materials featuring high environmental acceptability.

The electrolyte used is 25% potassium hydroxide solution. Separation of gas from the electrolyte and cooling of the product takes place in special optimised electrolyte drums and gas coolers mounted above the cells. Due to this configuration, natural circulation of the electrolyte is achieved. No pumps are needed to circulate the electrolyte in the electrolyser.

Gas purification takes place in scrubbers working with automatic hydraulic pressure equalisation, which doubles as a safeguard against system overpressure.



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

The major advantages are:

  • Hydraulic pressure equalisation
  • Natural circulation of electrolyte, no pumps
  • Visual working check on every cell
  • Low energy consumption due to special activated electrodes
  • Standard-design units for all capacities
  • Small space requirements
  • Minimum installation time and expense
  • No utilities needed other than electricity and water
  • Simple operation
  • Automatic monitoring
  • Safety vent
  • Low capital outlay

Range of Supply

The low-pressure electrolyser are available in unit capacities of 2 – 480 Nm3/h hydrogen and 1 – 240 Nm3/h oxygen output. Larger capacities can be  obtained by operating a multiple number of units in parallel.

Four standard types are available, based on the same advanced technology but with varying electrode surface areas:

  • ND1 (S25)          approx. 0,25 m2 per cell
  • ND2 (S100)        approx. 1,0 m2 per cell
  • ND3 (S150)        approx. 1,5 m2 per cell
  • ND4 (S300)        approx. 3,0 m2 per cell

The capacity of the low-pressure electrolyser is matched to the given gas demand by choosing the electrode surface area and modifying the number of cells between 10 and 120 depending on the electrolyser type, meaning that any capacity within the standard range can be accommodated by our standard type units.

In addition to the electrolyser, the overall plant comprises

  • Modern signaling and monitoring system
  • Transformer/Rectifier
  • Feed water system
  • Electrolyte station
  • Low pressure gas holder
  • Gas analysis station

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 less than 1 ppm
  • Gas compressors, for instance to deliver gas at bottling pressure (200 bar)
  • Gas bottles and bottle bundles
  • Gas cylinder bundles
  • Gas storage vessels
  • Modern signaling and monitoring systems


Operating Data

Hydrogen and oxygen are generated at a pressure of approx. 30 mbar.

Gas purities

Hydrogen:                      99,8 – 99,9 vol%
Oxygen:                          99,5 – 99,8 vol%

Residual impurities in product gases:
O2 in H2:                        0,1 – 0,2 vol%
H2 in O2:                        0,2 – 0,5 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:                        3,90 – 4,22 kWh/m3 H2
(gas at 20°C, 1013 mbar, moist)

Energy:                        4,3 – 4,6 kWh/Nm3 H2
(gas at 0°C, 1013 mbar, dry)

Feedwater:                  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 low-pressure electrolysers are designed for many years of uninterrupted operation and during that time are essentially free from maintenance requirements.

An partial overhaul of the plant is recommended after 15 years in service. By reason of extensive standardisation, all parts needed for routine overhaul can be delivered in advance. This minimises the duration of the shutdown for maintenance.

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