May 2024 Volume 6

ENERGY

The Path to Decarbonization

Hydrogen Combustion Furnaces

2400°F

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Electric Radiation Furnaces

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1750°F R A

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Electric Convection Ovens

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1100°F

450°F

FURNACE VOLUME

Figure 2: The Path to Decarbonization

With industry and government targets having been set all around the world – including the 2050 net zero commitment – then appropriate use of resources and high levels of energy efficiency become para mount, and electric heating can make a major contribution. Energy efficiency can exceed 95 percent, compared to 60 to 80 percent with gas-fired furnaces. Additionally, there is no need for expensive venti lation systems and gas recuperators. Typically, electric furnaces are also quieter, safer and free of pollution (such as NOx). Electric Elements There is no ‘one size fits all’ approach to electric heating, whether for a new furnace or a retrofit, and all aspects are considered on their merits. So, for instance, Nutec Bickley considers various types of elements, according to application: • Ambient temperature at 1,100°F (600°C): Tubular type elec trical elements. • Ambient at 2,280°F (1,250°C): Electrical resistor elements made of metallic material (FeCrAl: wire, rod, strip) of various shapes (retention system of insulation, vacuum-formed ceramic modules, bayonet, etc.). • From 1,100°F (600°C) to 2,730°F (1,500°C): Silicon carbide (SiC) electrical elements (note: there is a lower limit for the operating temperature, but the load of the surface of the element must be set to achieve an element temperature of least 1,650°F (900°C). • High temperature – 2,190°F (1,200°C) to 3,090°F (1,700°C): molybdenum disilicide (MoSi2).

For all types of electrical resistance design, the surface charge (W/ cm²) is essential for superior performance and a longer useful life. For power control, again we select the most appropriate solution, depending on the unit, the product, and the element type. Gener ally, based on SCR (silicon-controlled rectifier thyristor) technolo gies, we would look to specify either SCR-zero cross or SCR-phase angle for our equipment lines. Hydrogen Firing The past few years have seen an increasing concentration on the potential of hydrogen as a combustion fuel, with various pilot plants around the world, and a number of technological approaches. Sources of hydrogen also vary (see Figure 3), and a summary of the main types is: • Green Hydrogen: Produced by electrolysis of water using renewable energy. • Blue Hydrogen: From natural gas with carbon capture and storage. • Grey Hydrogen: Sourced from coal and natural gas. Gener ates CO2 emissions. Considering its use for combustion processes, hydrogen (H2) reac tion delivers less energy per standard cubic feet (scf), which leads to a higher volume needed to deliver the same amount of energy. Typically, natural gas would deliver 1,000 Btu/scf, while H2 would achieve more like 325 Btu/scf. Energy density by mass is higher, so H2 is pressurized to transport it more efficiently. An obvious upside is that hydrogen combustion

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FIA MAGAZINE | MAY 2024