Hydrogen combustion holds great potential for decarbonizing sectors that are difficult to electrify with renewable sources, such as high-temperature industrial processes that currently rely on natural gas. Hydrogen’s ability to replace traditional fossil fuels, like natural gas, makes it an attractive option—though not without its challenges. In this article, we will explore the fundamentals, advancements, and future outlook of hydrogen combustion, with a focus on Spain, based on the experience Lean Hydrogen has gained in transitioning from natural gas to hydrogen.
Hydrogen combustion involves a chemical reaction between hydrogen and the oxygen in the air to produce energy in the form of heat. This process generates water as the only direct byproduct, with no carbon dioxide (CO₂) emissions, making it a cleaner alternative to traditional natural gas combustion by reducing the carbon dioxide equivalent emissions of the process. It is important to note that during combustion with air, the nitrogen present can react to form nitrogen oxides (NOx) depending on process conditions such as pressure and temperature. These compounds are atmospheric pollutants regulated by environmental standards due to their negative impact on air quality.
When aiming to implement hydrogen combustion to replace natural gas combustion, it’s essential to consider that the calorific value of natural gas varies depending on the extraction site. Natural gas has approximately three times the higher heating value (10.8–11.98 kWh/Nm³) compared to hydrogen (3–3.54 kWh/Nm³). Although natural gas has a higher volumetric energy density (kWh/Nm³), hydrogen surpasses natural gas in mass-based energy density (kWh/kg). Therefore, in any energy-consuming process, it is necessary to determine the required hydrogen amount to meet the process’s energy needs. At Lean Hydrogen, we can guide you if you’re unsure how to replace natural gas in your process with green hydrogen.
Specialist companies in boilers and burners that use natural gas as fuel are already working on hybridizing natural gas with hydrogen in their boilers and burners, even managing to operate their equipment 100% on hydrogen—as is the case with E&M Combustión. They are well aware of the challenges that must be addressed in hydrogen combustion, such as the generation of nitrogen oxides (NOx). Although hydrogen does not produce CO₂, the high combustion temperature can lead to the formation of NOx, an atmospheric pollutant. One way to reduce nitrogen oxide emissions is through flue gas recirculation, a method used in E&M Combustión’s equipment.
A noteworthy example of hydrogen use in combustion systems is a project where Lean Hydrogen was responsible for all the engineering. It integrates a 100 kW PEM technology electrolyzer, hydrogen storage, and a fire-tube steam boiler, which includes a combustion system for operation with natural gas and hydrogen from E&M Combustión. The steam used in the plant’s process, which previously used natural gas as fuel, now runs on a natural gas and hydrogen mix, with the potential to run solely on green hydrogen—achieving a significant reduction in emissions. This change helps reduce the process’s carbon dioxide equivalent emissions by around 5% annually, showcasing the impact of switching from natural gas to green hydrogen.
Hydrogen combustion is a promising solution for decarbonizing industrial sectors that are hard to electrify, especially those requiring high temperatures and traditionally dependent on natural gas. While its implementation faces technical challenges—such as NOx generation and the need to adjust energy supply due to its lower heating value compared to natural gas—green hydrogen can play a key role in reducing the equivalent emissions of a process.
If your process is considering the transition to green hydrogen but you’re unsure where to begin, Lean Hydrogen specializes in designing comprehensive solutions to replace fossil fuels with hydrogen. Don’t hesitate to contact us.
Author: Christian Preciado Cárdenas
Date:31/03/2025
