[ water treatment ]
Fig . 3 . Circulated water polishing system with a capacity of 123 m 3 / h for a green hydrogen plant in Germany , designed and manufactured by Hidrofilt Water Treatment Ltd .
designed to remove ions and any by-products from the electrodes during the process to prevent the formation of secondary microbiological activity and the accumulation of total organic compounds ( TOC ).
Water qualities
The source of feedwater ( groundwater , urban water , surface water ) and its treatment significantly impact the price of feedstock water and , consequently , the cost of hydrogen production . Table 1 shows the required feedwater qualities for demi and ultrapure water .
The water quality requirements for recirculated water during electrolysis are determined by the technology supplier . Table 2 shows the water quality requirements for the circulated ( electrode ) cooling water used in a green hydrogen production plant in Germany .
Special considerations
In designing the recirculated water circuit , it is crucial to prevent metal ions release from piping and other components within the typical 50 – 60 ° C temperature range of the circuit , while also meeting the pressure requirements of around 8 bar ( g ). Limiting TOC leaching from watercontacting components and water treatment equipment is vital ; otherwise , the TOC content of the circulating water cannot be kept below the required limit , impairing conditions for economic and safe operation . Due to strict water quality requirements , maintaining high purity internal
Table 1 . Sample for main water requirements for hydrogen production make-up water |
Parameters |
Unit |
Demi water |
Ultrapure water |
pH |
- |
7 |
7 |
Temperature |
° C |
15 – 25 |
15 – 25 |
Electrical conductivity |
µ S / cm |
< 0.2 |
< 0.06 |
Resistivity |
MOhm-cm |
5 |
18.2 |
Total organic carbon ( TOC ) |
mg / l |
< 0.2 |
< 0.01 |
Silicate ( SiO 2 ) |
mg / l |
< 0.2 |
< 0.005 |
Iron ( Fe 3 + ) |
mg / l |
< 0.002 |
< 0.0002 |
Cooper ( Cu 2 + ) |
mg / l |
< 0.003 |
< 0.0002 |
Cobalt ( Co 2 + ) |
mg / l |
< 0.003 |
< 0.0002 |
Barium ( Ba 2 + ) |
mg / l |
< 0.05 |
< 0.005 |
Calcium ( Ca 2 + ) |
mg / l |
< 0.002 |
< 0.002 |
Chromium ( Cr 3 + ) |
mg / l |
< 0.002 |
< 0.002 |
Manganese ( Mn 2 + ) |
mg / l |
< 0.002 |
< 0.002 |
Chloride ( Cl - ) |
mg / l |
< 0.2 |
< 0.02 |
Fluoride ( F - ) |
mg / l |
< 0.005 |
< 0.0005 |
42 Hydrogen Tech World | Issue 15 | April 2024