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4 Efficient Electrotechnologies for Process Heating

Key Points
  • Process heating accounts for about 33 percent of industrial energy use.
  • Innovative heating technologies include induction, infrared, microwave and radio frequency.
  • These technologies can reduce energy costs by 20 to 50 percent in some cases.

Infrared heatingHeating processes consume about 3.0 quads (quadrillion Btu) of energy each year, according to the U.S. Department of Energy (DOE). In case you were wondering, that's a lot of energy—about 33 percent of total industrial energy use. Unfortunately, much of that energy is wasted. The following innovative technologies are helping to improve process heating efficiency, while also increasing productivity and product quality.

1. Induction heating has replaced a wide variety of conventional process heating technologies, such as electric and gas furnaces, flame heating and specialized brazing processes. These methods heat the outer surface, while induction heating goes deep inside the workpiece. Energy cost savings of 20 to 50 percent are possible.

In one example, induction heaters replaced a salt bath and a gas-fired furnace for energy savings of 50 percent. Additional benefits included a 40 percent increase in process productivity and a 20 percent reduction in rejects. Another facility replaced their aluminizing process with an induction hardening system. The result was energy cost savings of 20 percent and productivity increase of 25 percent.

2. Infrared heating uses electromagnetic waves and has a higher rate of heat transfer than conventional convection ovens. Metal filaments are heated to generate the infrared energy. The method is best applied to heating the surfaces of flat objects. Multiple infrared heaters can be used for heating angled or curved surfaces. It's most effective in application such as drying paper and textiles, curing of rubber and preheating aluminum.

The advantages of infrared heating include shorter curing times, faster line speeds, high energy efficiency and low standby losses. The process is also easy to control.

3 Variable frequency microwave (VFM) heating. Conventional microwave furnaces use standing waves that create a non-uniform energy distribution in the working cavity. VFM furnaces eliminate non-uniform energy distribution and provide reproducible heating with every batch. The benefits of VFM units include rapid curing (typically 10 to 20 times faster than convection), selective heating and precise control of temperature profiles.

VFM furnaces are mainly used in electronic assemblies and semiconductor packaging for curing adhesives and polymer coatings, as well as for annealing dopants and other layers on silicon wafers.

4. Radio frequency (RF) heating and drying replaces hot-air drying ovens that rely on fossil fuels or steam generated with fossil fuels. This method is used for ceramics and glass-fiber products, food processing, textiles, as well as inks and adhesives. Treating nylon materials or polymers with RF energy can also improve the strength and other mechanical properties of these materials.

RF electromagnetic radiation heats the interior of the material, as well as the surface at the molecular level. Materials that are difficult to heat, dry or cure with convection or IR heating are good candidates for RF.

How can you save money by improving process heating system performance? Use the DOE's Process Heating Assessment and Survey Tool to estimate the energy consumption of your process heating systems and assess the benefits of equipment upgrades.

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