High Pressure Atex Multistage Pump for Green Hydrogen Energy Plant

4 min read

Can pump a wide range of clean low viscosity fluids..

Low Emission Fuel Background

The demand for cleaner low emission fuels has been on the rise in recent times due to the ongoing threat of global warming and the greener mindset of younger generations. In 2010 only 7% of the UK’s generated power was from renewable sources, however in 2020 this skyrocketed to 47%, an obvious sign of change for the better.

The most popular types of renewable energy include solar, wind, hydro, tidal, geothermal and biomass, these are in abundant supply and usage is on the increase. However dirty sources of power such as fossil fuels (gas, oil and coal) and nuclear energy still account for the largest proportion and it will take many years for them to become obsolete.

Hydrogen Types, Production & Energy Density

A new source of power increasing in popularity is hydrogen which is the most abundant element on Earth. It is an energy carrier that does not normally exist naturally, it must be produced from other materials. There are no harmful emissions from hydrogen once used, however it is the process of producing it that determines if it is considered a clean energy or not. There are many uses for hydrogen, including fuel cells, vehicle engines, powering commercial buildings and even for spacecraft propulsion making it a very exciting alternative source of power.

In the below graph you can see it has a far higher energy density – measured in Megajoules per kg than any other fuel currently used meaning far less is required to generate large amounts of energy.

image by By Scott Dial - Own workData Source: Energy density, Lithium-ion battery, Public Domain, https://commons.wikimedia.org/w/index.php?curid=5551431

The main types of hydrogen are blue hydrogen, grey hydrogen, and green hydrogen. Blue and grey hydrogen are the most common and involve splitting hydrogen from fossil fuels, mainly natural gas. This is achieved by either Steam Methane Reforming (SMR) or Auto Thermal Reforming (ATR), both methods produce Carbon Dioxide (CO2) as a biproduct which is harmful to the environment. The CO2 is released into the atmosphere during the production of grey hydrogen whereas it is captured and stored during the production of blue hydrogen making it a cleaner and safer option.

The most promising and cleanest is green hydrogen, this is produced by splitting the hydrogen from water by electrolysis. The only components produced are hydrogen and oxygen, there are no harmful emissions or biproducts. In addition to this, to be classed as green the electricity used to power the equipment during production must be derived from renewable sources such as wind or solar, this makes the entire production and end use zero emission and carbon free. Due to the potential use, abundant supply, and clean nature of green hydrogen, it is likely to become one of the main sources of energy in years to come.

Safe Transfer Utilising a Carrier Fluid

It is possible to make hydrogen easy to transport through the use of Liquid Organic Hydrogen Carriers (LOHC) utilizing Benzene, Dibenzyltoulene (DBT), Napthalene, Toluene or a derivative to absorb the molecules into their structure.

It is hydrogenated with a base carrier to handle it and then dehydrated to extract the gas. Hydrogenious technology requires high pressures and temperatures to extract the gas from a carrier making it energy intensive to produce and extract, whilst remaining safe to handle. This safe method of handling is expected to be used as its use becomes more commonly used throughout industry.

Process Background

We worked in collaboration with a leading manufacturer of green hydrogen systems to find a solution to their pumping requirements. Electrolysis requires the circulation of high temperature water with small concentrations of potassium hydroxide while the system pressure can be as high as 40 bar. The differential pressure required from the pump is only 2 bar however the inlet of the pump can see pressures up to 37 bar, this requires a high-pressure pump that is built to cope with these strenuous demands.

Operating 24/7, they need a reliable and robust pump alongside being Atex rated to ensure the system is safe due to the flammable nature of hydrogen. Single stage centrifugal pumps can handle the flow and pressure requirements of this project however the high system pressure necessitates a multistage pump. The multiple impeller design allows the production of high pressures while the high-pressure flanges, double mechanical seal and robust casing allow the handling of high inlet pressures without risk of leakage, a perfect solution for an installation such as this.

We manufactured the pump with stainless steel 316 casing, impellers, and diffusers for chemical compatibility with the potassium hydroxide to guarantee long life for the components. The pump, coupling and motor are Atex certified for installation in non-safe areas such as this, this removes the risk of sparking while operating and ensures a safe environment for workers.

As energy output requirements can vary, the pump is being used in conjunction with a variable speed drive to allow high flow rates during peak times and low flow rates when demand is low, thus saving power when not required, adding to the already green nature of their equipment. They now have a robust and dependable pump solution and will be producing clean energy for years to come, a great project to be involved with.

Here are some key benefits of multistage pumps:


  • Can pump a wide range of clean low viscosity fluids.



  • Flow rates up to 1000m³/hr.



  • Operating pressures up to 55 bar and casing pressures up to 63 bar.



  • Multiple different inlet/outlet flange configurations for easy installation.



  • Vertical or horizontal installation options.



  • Fluid temperatures up to 140°C.



  • Installed with sacrificial wear rings to prolong the life of other components.



  • Available in a wide range of materials including cast iron, 316 stainless steel, duplex stainless steel, and bronze.



  • Gland packing or mechanical seal options.



  • ATEX versions on request.



  • Can be installed with an air powered or electric priming pump for self-priming applications.


Read more about Multistage Pumps in our Guide

Below are the specifications of the supplied Atex multistage pump:

Model:NRS-KM50C/2-1450EX - ATEX Stainless Steel Horizontal Multistage Centrifugal Pump
Fluid:High temperature water with low concentration Potassium Hydroxide
Materials:Stainless steel 316 casing, impellers, and diffusers
Flow rate:24m³/hr
Pressure:2 Bar differential, 40 Bar system pressure
Inlet/Outlet:DN65/DN50 – PN40
Motor:3 Kw/230-400V/3Ph/50Hz/IP66/1500 RPM, Atex