Sep-2023

Process heating solutions for hydrogen production

With the demand for electrical power continuing to rise, along with the need for renewable power, an alternative and sustainable solution is hydrogen.

Thermon

Article Summary

The demand for electrical power globally has never been greater and continues to rise. First, there is a demand to help reduce carbon dioxide and other greenhouse gases. Second, there is a demand for sustainable and renewable power sources. The buzzword that describes this is ‘Electrification’. It’s a term that describes renewable power generation and the use of electricity as an energy source.

One of the alternative solutions toward a clean and renewable fuel source is hydrogen.
Hydrogen can be a sustainable feedstock fuel option for electrification, provided the water source does not impact other supplies and the electricity comes from a sustainable source such as wind or solar. Hydrogen is fuel, an energy transport method, and an indirect electrification method. Storing hydrogen or ammonia provides abundant, sustainable electricity for the chemical and petrochemical industries.

Governments are interested in finding alternative, clean energy sources that achieve net-zero CO₂ emissions by 2050. The European Union plans to invest $740 billion in renewable hydrogen projects. In the US, 16 states have committed to reducing carbon emissions by 50% to 100% by 2050 or earlier.

The global demand for hydrogen has risen to over 70 million tons annually. Hydrogen has become the clean energy source of choice for climate change mitigation strategies worldwide.

This article will explore the methods for generating green hydrogen and its use as an alternative fuel source.

Hydrogen – a renewable energy source
Hydrogen is the universe’s most abundant element. When it combines with other atoms, it requires energy to separate. For example, one water molecule is two hydrogen atoms and one oxygen atom or H₂O. Running an electric current through water can split the atoms into one-part pure oxygen and two parts pure hydrogen. The process is known as electrolysis.

Hydrogen has a colour code such as Green, Blue, Gray, and Brown for various manufacturing processes.
Here’s what the different colours of hydrogen represent:
• Brown hydrogen comes from the gasification of coal. The downside is that the carbon dioxide and other emissions get released into the air, causing pollution.
• Grey hydrogen’s source is natural gas, and the associated emissions flow directly into the air during this process.
• Blue hydrogen also comes from natural gas, methane, or coal gasification. During the process, the carbon dioxide gets captured and stored.
• Green hydrogen comes from water using electrolysis powered by renewable electricity.

Three methods to produce green hydrogen by electrolysis
Hydrogen by electrolysis
Electrolysis breaks down water molecules (H₂O) into oxygen (O₂) and hydrogen (H₂) using sustainable electricity. The process starts by immersing two electrodes in a water tank with minerals added to improve conductivity. As the electric current passes between the electrodes, oxygen gets released on the positive anode side and hydrogen on the negative cathode side. The gases get collected and stored.

There are three methods of producing hydrogen, electrolysis, Alkaline, Proton Exchange Membrane, and Solid Oxide.
υ Alkaline electrolysis (AEL)
AEL uses a liquid electrolyte, potassium hydroxide, with two metal electrodes suspended in the solution and a diaphragm separating them that is non-permeable to hydrogen and oxygen.
Industrial scale AEL technology has been around since 1927. It has a lower operating cost and a longer service life and achieves efficiencies between 70% and 80%. The drawbacks are that it takes about 50 minutes to cold start the process and is more sensitive to impurities as the gases dissolved in the electrolyte remain in the cycle.

ϖ Proton Exchange Membrane electrolysis (PEM)
A PEMFC is similar in that it uses an anode, electrolyte, and cathode to produce electricity. The difference is with the components. A PEMFC’s electrolyte uses a water-based, acidic polymer membrane and the electrodes use platinum. This design allows it to generate electricity at much lower temperatures below 100°C.

A PEMFC is similar in that it uses an anode, electrolyte, and cathode to produce electricity. The difference is with the components. A PEMFC’s electrolyte uses a water-based, acidic polymer membrane and the electrodes use platinum. This design allows it to generate electricity at much lower temperatures below 100°C.
Industrial PEM fuel cells require additional heat from a boiler for cold weather start-ups. Thermon’s electric boilers can expedite cold weather start-ups. Once the PEM electrolyte is active and warm, the boiler will shut down.

ω Solid Oxide Electrolysis (SOEL)
In SOEL, a solid oxide that conducts oxygen ions separates the two electrodes. This system operates at temperatures of up to 1000°C using superheated water vapour. Reaching these high temperatures requires electrical steam superheaters or circulation heaters. If powered by an external heat source, such as industrial waste heat, SOEL achieves the highest efficiency of around 80%.

Caloritech (EX) circulation heaters are used in this high-temperature application to superheat the steam for the electrolysis unit to operate at optimal temperatures. Thermon’s steam superheating systems provide instantaneous heating of process steam to the solid oxide electrolyser while only using the exact amount of power needed when paired with SCR controllers.

Cleaning and purification of hydrogen
There are two primary methods to purify hydrogen gas, Pressure Swing Adsorption (PSA) and Temperature Swing Adsorption (TSA).