Dec 10, 2024
ELECTROMAGNETIC DRYING: IR AND MICROWAVE TECHNIQUES
PART 1 – SOLUTIONS FOR DIFFERENT INDUSTRIES
Electromagnetic drying encompasses infrared (IR) and microwave drying techniques, but they utilize different wavelengths of electromagnetic energy to dry materials. Microwave drying, which uses microwaves generated from electric energy, is effective for uniform and rapid heating of materials with varying thickness. While IR drying emits infrared waves from gas or electric energy, and can be ideal for uniformly heating thin materials. These technologies are widely used but a further understanding of their drying methods and wavelengths is key in selecting the right solution.
Diagram illustrating IR and microwave wavelengths in the electromagnetic spectrum.
DRYING METHOD
Both microwave and IR are energy-efficient drying techniques as they directly transfer energy (microwave or IR waves) to the molecules without significantly heating the surrounding air.
In IR systems, IR waves are generated from electric or gas energy and emitted into a chamber from emitters. A few types of emitters are quartz tubes, ceramics, and gas catalytic heaters. Molecules in the material absorb the IR waves causing them to vibrate more rapidly, increasing their kinetic energy. This kinetic energy is converted into thermal energy, increasing the temperature of the material.
In microwave systems, microwaves are generated from electric energy in magnetrons and direct into a chamber via waveguides. Polar molecules in the material absorb the microwaves and try to align to their electric field, causing rapid vibration and friction between molecules. This friction converts microwave energy into thermal energy, increasing the temperature of the material.
The energy penetration depth changes with wavelength for both technologies. For instance, larger wavelengths penetrate more than smaller wavelengths. Microwaves have longer wavelengths from 1 millimetre to 1 meter, while infrared wavelengths range from 1 millimetre to 700 nanometres. As a result, IR drying can heat the bulk of the material, but it cannot volumetrically heat material thicker than a few millimetres. Whereas microwave drying is a volumetric process that can penetrate deeper into material (depending on the material) for uniform heating.
MATERIALS AND END PRODUCT
IR drying is limited to material a few millimetres in thickness due to its wavelength. Whereas microwaves can penetrate material up to a few inches depending on the wavelength. As a result, IR drying is great for roasting food products and curing thin materials like paint, paper, and textiles. This is where IR can selectively act on the surface of a product, so energy is not wasted heating the rest of the bulk. Microwave drying is ideal for applications that require uniform heating or relatively thicker materials like foam, shelf-stable food products, and composite panels.
Ideal applications for IR and microwave drying: infrared drying thin food on the left, microwave drying foam on the right.
CONCLUSION
IR and microwave drying techniques both offer energy-efficient processing, but their applications differ primarily due to differences in wavelength penetration depth. For optimal results, consider your specific material characteristics, product goal, and drying requirements when choosing between these technologies. Contact us to learn more about microwave drying and its applications.