Hydrogen, the future of combustion?


Hydrogen, the future of combustion?

Today, most of the world’s energy is obtained by burning fossil fuels, which are cheaper than renewable resources.

Green hydrogen (H2) can replace some fossil fuels, especially natural gas, in some combustion plants as a fuel for gas turbines and industrial processes.

Some reduce pollution by 90% in the form of nitrogen oxides (NOx) produced by hydrogen combustion methods.

Hydrogen, the future of combustion

As the population grows, so does the world’s demand for energy. This is because, as an indisputable fact, almost all activities require energy: industry, domestic activities, urban, intercity, and intercontinental travel. Today, most of the energy used is obtained by burning fossil fuels, which of course is not a renewable resource because it is cheaper and renewables face a series of challenges that fossil fuels may not need to repeat.

Inevitable burning

The desire to stop burning fossil fuels doesn’t necessarily mean that combustion processes will disappear — they are widespread and have been in widespread use for about 150 years. Besides, there is no serious reason for them to disappear. However, there are too many of them: gas turbines, thermal and hybrid engines, burners for heating plants and petrochemical furnaces, burners for drying operations, combustion systems for industrial and domestic boilers, etc. Each is developed for a specific application.

Alternatives such as fuel cells or batteries may be interesting for some niche uses, but they are neither clean nor safe, and still cost a lot economically, socially, and environmentally. Which substances can replace fossil fuels, especially natural gas, in these combustion units is up for debate? The glass industry is considering green glass, and one of the potential candidates to meet its concerns and needs is green hydrogen (H2). This is also a perspective of the cement industry, and more broadly, of all industries.

Let us remember that pure hydrogen in the gaseous or liquid state does not exist in nature (it is present in very small amounts in Earth’s atmosphere). Even though it is theoretically possible to obtain from plant matter (biomass), it seems that we are moving towards production by electrolysis of water and/or using thermal processes.

Hydrogen, the future of combustion?

Combined with the use of renewable energy for production, green hydrogen represents a potential alternative fuel for gas turbines to produce low-emission electricity as well as the aforementioned industrial combustion processes. However, due to the physical differences between hydrogen and other fuels such as natural gas, a well-established gas turbine combustion system cannot be directly converted to hydrogen combustion – a process that has been developed over the years as it provides substantial reductions in NOx [ Pollution in the form of nitrous oxide (x=1) and nitrogen dioxide (x=2)] emissions, without emissions of particulate matter (PM or soot) or carbon dioxide.

Extensive fundamental research in academic and R&D laboratories has led to a good grasp of the combustion mechanism of hydrogen in oxygen or air. They can be implemented in-house or in commercial CFD (Computational Fluid Dynamics) code. They do not only consider fluid mechanics, transport properties and heat exchange. And, more recently, the chemical composition of the combustion is taken into account, and there is enough skill to know which areas of the equipment to act on to limit the only pollutants that can form during the H2/air combustion process – i.e. NOx or NOx formation.

Reduce pollutants

It should be noted that industrialists and academics who have been studying these strategies for decades have only now demonstrated how to limit the formation of nitrogen oxides during the combustion of fossil fuels. These strategies include but are not limited to, EGR (exhaust gas recirculation), SNCR (selective non-catalytic “advanced” combustion technology), and a combination of independently existing technologies.

These abatement strategies can be implemented in plants that burn hydrogen/air mixtures as needed. Knowing that some of these allow for a 90% reduction in NOx, it is clear that hydrogen combustion is a serious, clean, and safe option. Of course, the chemical risks involved with using hydrogen are not the same as with natural gas. However, these risks are known and perfectly controlled, exactly like those of fuel cells, etc.