Hydrogen is quickly becoming one of the most talked about future fuels. Manufactured in a variety of ways, it is created using various techniques from renewable to non-renewable energy and poised to be the fuel of the future.
In a recent project, we were tasked with supporting large scale production of green hydrogen using alkaline water electrolysis. This process can produce greener hydrogen and is an important step towards environmentally friendlier energy production.
The electrolyser has two electrodes – one positively charged anode and one negatively charged cathode. These are immersed in a 30% potassium hydroxide (KOH) caustic aqueous solution, and separated by a diaphragm or membrane.
During electrolysis with KOH, water is split into its component parts, hydrogen and oxygen.
When an electric current is passed through the electrolyte, it causes the water molecules near the negative electrode to reduce, producing hydrogen gas. At the same time, oxidation of hydroxyl ions takes place at the positive electrode, generating oxygen gas.
The gas mixture of hydrogen and oxygen produced can be used to generate electricity or as a fuel. The only by-product of electrolysis is water. So, alkaline water electrolysis using KOH contributes to a better, long-term solution to greener energy generation.
Our project specification
Here at North Ridge Pumps, we can specify a large range of pumps for a wide variety of industrial applications and sectors.
What’s more, we’re not restricted to just one pump technology. The technical expertise of our experienced team enables us to deliver a bespoke solution, not something straight off the shelf. So we can always select the most cost-effective pump for any particular client, project or application.
For this hydrogen gas generation project using alkaline water electrolysis, we specified two high pressure vertical multistage pumps.
Many other pump designs and systems are available including horizontal pumps. So why did we choose this specific design?
Vertical multistage pumps vs horizontal centrifugal pumps
Different pumps are suitable for different jobs, locations and processes. For this application, a vertical multistage pump is perfect because it has a smaller overall footprint than a horizontal pump which would take up more floor space.
In addition, the overall casing pressure would be able to take up to 63 bar of pressure. Plus, vertical pumps have a sleeve bearing at the pump end lubricated by the pumped medium, whereas horizontal pumps feature a heavy duty thrust bearing located at the opposite end to the drive end.
What does multistage mean?
Centrifugal pumps, whether horizontal or vertical, usually have just one impeller, where a multistage pump has multiple impellers fitted back to back.
Adding extra impellers like this enables the pump to generate much higher pressures than can be achieved by using a single impeller at maximum diameter.
This is because when an impeller reaches a particular diameter, the side friction which increases with size reduces overall pump efficiency. This means that additional impellers have to be added along the shaft in stages called ring sections to achieve high pressures.
More impellers for higher pressure
These extra ring sections increase the total head and shaft power in proportion to the number of stages added – but without negatively affecting the flow rate.
In short, multistage pumps are highly efficient, and can also provide multiple duty points by using a variable speed drive or multiple outlets on the same pump.
They are ideal for applications that include high pressure circulation, boiler feed and pressure boosting of clean fluids. They are also suitable for slightly contaminated fluids if the pumps are larger and gaps within the pump design allow solids to pass through.
The vertical multistage pumps we specified for this hydrogen generation job were specified with an inlet pressure of 40 bar and up to 10 bar differential pressure. They were made from hardwearing stainless steel and achieved a flow rate of between 50L/min and 150L/min.
If you have a fluid transfer application requiring the movement of sensitive fluids, solids or viscous materials and aren’t sure which pump to specify, speak to North Ridge Pumps to see how we can help.
