How Microwave Drying Works
Microwaves are radio waves that operate in discrete frequency bands; they are non-ionizing and non-nuclear. Unlike all other methods of heating which begin heating from the surface and move inward, microwaves simultaneously penetrate all parts of the material so that heating occurs uniformly. This is called volumetric heating.
Microwaves produce heat by vibrating polarized molecules (usually water molecules, which are highly polarized), almost a billion times per second. The resulting friction converts the radio waves to heat and vaporizes the water. Molecules of other non-polar substances, such as protein, fat, and fiber, do not readily absorb microwave energy, and thus do not heat up as much. This effect, combined with the evaporation of surrounding water, keeps the product much cooler than in conventional gas fired dryers. As a result, almost all the energy applied removes water, unlike conventional dryers where a significant portion of energy is lost heating air and steel. Microwave dryers typically have 80%+ energy efficiency compared to about 50% for gas-fired rotary drum dryers.
Industrial Microwave System Components
Unlike home microwaves, our industrial microwave systems separate microwave generation from the cooking/drying cavity. A system is constructed using one or more microwave generator units. Standard generators are able to produce up to either 75 KW or 100 KW of output power. Using special duct called waveguide, the energy is carried from the microwave generator to one or more industrial-sized microwave cavities. A typical cavity is about 12 feet long and five feet wide. A conveyor belt fabricated from microwave-transparent material carries the product through the cavities. A simple system may consist of one generator and one cavity, while a large system may have a dozen generators and six cavities. This inherent modularity provides great flexibility when constructing a system from the ground up, or when scaling up an existing system up to meet customer needs.
Producing Better Quality Products
Conventional gas dryers have internal temperatures of 500ºF to 1100ºF which results in significant degradation of protein and amino acids in animal feeds. Caramelization and Mailard reactions occur at a temperature of about 300 ºF. In our industrial microwave heating systems, product temperatures typically do not exceed 212ºF, well below the temperature where amino acids and proteins are degraded. The result is that the full nutritional value of the feed is preserved.
Additionally, microwaves can enhance the activity of enzymes applied to animal feeds. Microwave energy breaks down the structure of cellular walls that gives enzymes more attachment points on the otherwise crystalline cellulose structure. This can greatly enhance the activity of enzyme treatment. Also, it has been well established that microwave processing can destroy E. Coli, listeria, and certain other harmful microorganisms.