H 2 -ready process burners
Advancements in hydrogen burner technology enable safe, stable combustion with ultra-low NOx emissions while firing up to 100% hydrogen
Eric Pratchard Zeeco Inc.
R ising fuel costs, new regulations requiring carbon footprint reductions, and global net-zero carbon initiatives continue to pressure the refining and chemical industry markets. The two main methods to reduce carbon monoxide (CO) and carbon dioxide (CO₂) emissions are either to capture and sequester carbon from the flue gas or to remove carbon from the fuel before combustion. Many organisations are considering refuelling existing fired equipment with sustainable, low- carbon fuels. One such fuel is hydrogen (H₂), which is mainly produced through renewable energy sources (green H2) or by reforming natural gas (blue H2). Removing carbon before combustion eliminates the need for costly equipment to capture and sequester it from the flue gas. Whether produced from green or blue sources, or recovered from existing plant processes, H₂ can be injected into existing fuel gas networks to produce high H2 blends, or used in pure form to fuel fired heaters and process furnaces. As H₂ displaces hydrocarbons in the fuel composition, the number of carbon atoms decreases. A fuel stream composed of 100% H₂ cannot generate CO nor CO₂ as a byproduct of combustion due to the lack of carbon in the combustion reaction. Therefore, the higher the H₂ content of a fuel, the lower the overall CO and CO₂ emissions. Due to the markedly different combustion characteristics of H2 compared with conventional hydrocarbon fuel gases, there are several challenges that plant owners and operators need to consider when transitioning to H2 firing. Design challenges Most fired heaters and process furnaces in use today were designed to burn natural
gas or refinery fuel gases that contain a high proportion of saturated hydrocarbons, along with H2 , inert gases, and traces of other compounds. Typical H2 content for refinery fuel gas may range from 20-40% by volume. For H2 refuelling, H₂ concentrations of 90-100% are probable. This quantity of H2 alters the burner’s operating parameters, so special attention must be paid to the burner design to ensure the heater’s operation is not adversely affected. Firstly, the laminar flame speed of H2 is significantly higher than that of hydrocarbon fuels, promoting a more rapid combustion “ Employing ultra-low NOx burner technologies can help maintain compliance with legislative NOx emission requirements when firing high H₂ fuel ” process and increased heat release per unit volume. Combining that fact with higher adiabatic peak flame temperatures leads to elevated temperatures local to the burner, which directly increases thermal NOx emission rates by up to a factor of three. Employing ultra-low NOx burner technologies can help maintain compliance with legislative NOx emission combustion is approximately 5.7 ft per second (ft/s), while the flame speed of natural gas is significantly slower at only 1.3 ft/s. H₂ firing has a higher stoichiometric adiabatic flame temperature of 3,960°F, while natural gas has an adiabatic flame temperature of 3,518°F.1 These significant differences in combustion characteristics require engineers to evaluate the requirements when firing high H₂ fuel. For example, the flame speed in H₂
Refining India
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