Interest in hydrogen as a fuel continues to grow, in large part because it generates water when combusted, with no carbon dioxide generated. In the past, using hydrogen as a fuel was only economical in certain applications. As the costs to produce hydrogen continue to decline and the interest in reducing CO2 emissions grows, more applications are considering the use of high hydrogen fuels. A recent publication predicts the global market for hydrogen will increase four-fold in the next 30 years.Hydrogen has the potential to be an important green fuel depending on how the hydrogen is generated. Today, hydrogen is commonly produced on a large scale in hydrogen reformers. These react steam and methane in catalyst-filled tubes located inside a furnace heated by the combustion of fossil fuels. Those steam-methane reformer (SMR) furnaces generate CO2 emissions. If those CO2 emissions are captured, this is referred to as “blue hydrogen.” If the CO2 is not captured, this is referred to as “grey hydrogen.” There is currently considerable work on expanding the production of hydrogen in SMRs, such as improving catalyst performance. However, if hydrogen is made with renewable energy, such as wind or solar energy powering an electrolysis process for example, then CO2 would not be generated during hydrogen production. This is referred to as “green hydrogen.”While high levels of hydrogen have been used in some applications such as boilers and fired heaters for many years, there are important issues that need to be considered for new applications. For example, hydrogen has a higher potential for leakage, very wide flammability range, higher flame speed, lower heating value on a volume basis, less air required per unit heating value, and higher adiabatic flame temperature compared to most common hydrocarbon fuels. A potential problem with higher flame speed is a higher propensity to flashback in a premixed system. Another potential downside to using hydrogen for combustion is increased NOx emissions when air is the oxidant because of the increased adiabatic flame temperature. All of these issues impact the design of the combustion system which means that it is not necessarily a simple conversion from an existing hydrocarbon fuel to a fuel containing high levels of hydrogen. This includes the fuel delivery system, burner design, heat transfer, and pollution emissions, among others.This paper will provide an overview of the combustion of fuels containing high concentrations of hydrogen up to pure hydrogen. It will discuss the key considerations when designing a combustion system for high hydrogen fuels, including potential problems. It will also include some example applications of using high hydrogen combustion.

Hydrogen: Fuel of the Future?

Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2021/volume/85543

ASME 2021 International Mechanical Engineering Congress and Exposition (IMECE2021)

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