Since IMS can offer three different types of traveling-wave applicators, it may provide a better solution than a one-size-fits-all multimode microwave planar design.

An IMS PHS has advantages over conventional dryers in two areas of their design that are intrinsically inefficient: (1) pre-heating a product to evaporative temperature, and (2) removing water from products with relatively low overall moisture content.  The volumetric heating characteristic of microwave drying and the high energy densities that are possible with certain microwave dryer designs can overcome these two inefficiencies of conventional dryers.

The Ridged Waveguide Applicator Design is ideal for commercial applications involving materials that do not easily absorb microwave energy, are extremely thin ( less than about 0.25 inches or 6 mm), and have a low initial moisture content ( less than about 25%).  Final moisture levels of 0.2% or less have been achieved with some products.

The Wide Applicator Design is best suited for materials ranging from 0.25 to 2.00 inches (6 to 25 mm), that can easily absorb microwave energy and have a high initial moisture content (typically up to 50%).

Both the Ridged Waveguide and Wide applicators can heat and dry products with a width up to about 120 inches or 3000 mm. However, the Linear Applicator Design is limited to a product width of about 20 inches (500 mm) to insure its maximum efficiency when heating and drying.  It is therefore ideal for small-scale production or pilot plant use.

An IMS PHS can be used for many stand-alone commercial heating and drying applications.  These include textiles, pet food and treats, non-woven materials, foam, coal, biomass and agricultural materials.  However, its specific benefits and economic advantages are best achieved when applied to pre-heating materials before entering a conventional dryer to raise the product moisture to its evaporative temperature, or post drying materials after a conventional dryer to optimize the uniformity of its final moisture content.  Some typical applications are shown in the following examples:

  • An IMS PHS can increase production throughputs because rapid, uniform volumetric heating can significantly reduce overall drying timesA company that processes a glass fiber substrate product replaced a Radio Frequency dryer with a stand-alone IMS unit, and was able to reduce production downtime significantly while achieving faster and more uniform drying.  This is because it is easier to control the heating process in thin materials using microwave energy since the longer wavelength electromagnetic energy emitted by radio frequency generators is typically better suited to thicker products (>2 inches or 150 mm, depending on the material).  In addition, this customer was able to reduce the original RF heater footprint since his product could be dried vertically in the IMS PHS without the use of a conveyor belt.
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  • Improved operating efficiencies have been achieved by a PHS installed in a non-wovens insulation processing facility.  The product was extremely difficult to dry using conventional heaters or dryers due to its high resistance to conduction or convective heat transfer.  The IMS PHS was able to achieve the required final moisture level consuming considerably less energy.
  • Similar results have been achieved by manufacturers of thin foams, where the volumetric heating allowed for a faster drying process than would be possible with a conventional dryer.  In addition to the reduction in overall drying time, the patented IMS applicator design eliminates the hot spots associated with conventional microwave heaters, minimizes the risk of over-drying or marring the surface of the product, and allows the microwave energy to be increasingly absorbed in areas of higher moisture content.
  • Improvement of the manufacturing environment can be achieved by using modular designs, suitable for both vertical and horizontal applications.  This allows for a compact system footprint and was a prime reason a European processor of organic tiles selected IMS for its horizontal stand-alone dryer.  In addition to eliminating the NOx and SOx emissions from previous gas-fired dryers, the required final level of <3% moisture could be achieved in the IMS PHS while occupying less than half the footprint of a conventional unit.
  • IMS PHS technology can produce new products that conventional heaters and/or dryers cannot.  A major US manufacturer needed equipment that would quickly and uniformly dry a coating applied to its paper product.  After several in-house product trials, this customer purchased two IMS high speed 2450 MHz microwave dryers for commercial production of the special paper, which would have been virtually impossible to accomplish with any other dryer design.
  • Combined with other thermal technologies, IMS PHS designs can optimize final heater retrofits or new production lines.  As indicated previously, optimum payback is usually obtained by utilizing a PHS in a process application, either as a pre-heater or as a post heater, in combination with a traditional gas-fired re-circulating hot air dryer.
  • Operating and maintenance costs can be reduced as the IMS PHS has few moving parts other than the product conveyor belt.  The heating and/or drying process is easy to control, clean and inspect when required.


IMS recognizes that its technological innovations and applications knowledge are its most valuable assets. The ability to generate a uniform distribution of microwave energy and eliminate the uneven heating patterns (or "hot spots") traditionally associated with microwaves makes Industrial Microwave Systems’ technology unique and patentable. To date, patents on the Company’s Planar Heating technology include:

U.S. Patent #5,958,275 "Method and Apparatus for Electromagnetic Exposure of Planar or Other Materials", issued on September 28th, 1999.
U.S. Patent #5,998,774 "Method and Apparatus for Providing Uniform Electromagnetic Exposure", issued on December 8th, 1999.
U.S. Patent #6,075,232 "Method and Apparatus for Electromagnetic Exposure of Planar or Other Materials", divisional issued on June 13th, 2000.
U.S. Patent #6,087,642 "Electromagnetic exposure chamber for improved heating", issued on July 11th, 2000.
U.S. Patent #6,246,037 "Method and Apparatus for Electromagnetic Exposure of Planar or Other Materials", divisional issued on June 12th, 2001.
U.S. Patent #6,259,077 "Method and Apparatus for Electromagnetic Exposure of Planar or Other Materials", divisional issued on July 10th, 2001.
U.S. Patent #6,396,034 "Method and apparatus for electromagnetic exposure of planar or other materials", issued on May 28, 2002.
U.S. Patent #6,590,191 "Method and Apparatus for Electromagnetic Exposure of Planar or Other Materials", issued on July 8, 2003.
U.S. Patent #6,753,516 "Method and Apparatus for Controlling an Electric Field Intensity within a Waveguide", issued on June 22, 2004.
U.S. Patent #6,888,115 "Cascaded Planar Exposure Chamber", issued on May 3, 2005.
U.S. Patent #7,368,692 "Ridged Serpentine Waveguide Applicator:, issued on May 6, 2008.
U.S. Patent #7,470,876 "Waveguide Exposure Chamber for Heating and Drying Material", issued on December 30, 2008.
U.S. Patent #7,666,235 "Microwave Drying of Coal", issued on February 23, 2010.