Water treatment for hydrogen production

The amount varies depending on the efficiency of your electrolyser, but a good rule of thumb is around 200 L/h per MW electrolysis capacity. This does not include water for cooling.

Water contains two atoms of hydrogen and one oxygen atom. Because oxygen is 16 times heavier than hydrogen, it takes up most of the mass in a water molecule. 89% of the mass is oxygen and 11% is hydrogen. This means that to produce 1 kg of hydrogen, 9 kg of water are required. In reality, 10-13 kg of water are required due to losses and inefficiencies.

The quality depends on the type of electrolysis equipment you use, alkaline or PEM, and from which manufacturer the equipment is supplied. From a conductivity perspective, values can vary from 0.056-5 µS/cm, but many constituents affect the electrolysis process depending on the specific technology used.

ASTM Type I, II, II and IV are a set of international standards for water quality often used to describe water quality requirements for electrolysers. They cover conductivity/resistivity, sodium, chloride, TOC and silica, but in reality, they are often insufficient to properly describe the water quality needs for electrolysers.  

Both PEM and alkaline electrolysis requires make-up water treatment. PEM also requires continuous polishing of the water once it has entered the electrolysis cell. 

Whether to use EDI or mixed bed depends on whether you need it for make-up water polishing or internal polishing. Also, EDI tends to have higher CAPEX, but allows you to avoid regeneration of spent resins.

The choice of resin is very important to ensure a stable electrolysis process. Use of the wrong type of resin can lead to irreversible damage to your electrolysis stack.

Yes. Each source of water requires special attention to specific constituents in the water and you need to take variations in the inlet water quality into account. In general, we can say that wastewater requires special attention to nutrients and microorganisms that can cause biofouling, as well as the load of organics, while seawater requires focus on high retention of ions. 

The lifetime stated by electrolyser manufacturers is completely dependent on compliance with water quality requirements. Even small amounts of unwanted ions and molecules in the water can cause irreversible damage to the electrolysers. 

Typically, we need first to bring the raw water to a state similar to drinking water quality. From here the water most be conditioned to avoid scaling, after which a RO process is used to remove the bulk of the ions, organics, and colloids. A targeted process is also required to remove dissolved gasses. Finally, a polishing step can be implemented depending on the specific needs of the electrolyser.

Our equipment covers the range from small 1-10 MW installations to large scale GW installations.