transformed the nature of our transportation for the worse. A century later, electric vehicles are making a comeback with the promise of better energy efficiency and cleaner environment.

On 20 March 2007, a chain of events resulted in a small fire in the heat transfer system at ELM a leading bio-based lubricants manufacturing plant and grew out of control. Later research showed that heat transfer oils, while a mature technology, require significant fire prevention schemes. The ELM devastating experience dealt a blow to the growth of bio-based greases; but also inspired an active search for alternative heating methods.

Among many possible candidate heating methods considered, the use of microwaves was selected as showing the best potential for processing grease and lubricants. Initial laboratory success was followed by further experiments at AMTek Microwave Technology, a leading industrial microwave company that collaborated with the researchers at University of Northern Iowa. In 2010 the first microwave-based grease processing plant began producing grease at a new ELM manufacturing plant. The use of microwaves for heating products goes far beyond the grease and lubricants manufacturing. It promises to replace steam and hot oil heat transfer heating, and jackets for the vessels in many food and chemical processing applications. The expected savings in energy and in capital expenditure by switching to microwave


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processing parallels the conversion of automobiles from internal combustion engines to electric motors in electric vehicles. It appears that an accidental grease plant fire in 2007, may have well become the catalyst to eventually transforming the processing industry for the better.

Manufacturing Grease Manufacturing grease requires reacting a strong base and an [fatty] acid to make soap. The reaction results in water as by-product which requires high temperatures for dehydration. Most processing vessels are jacketed and use a heat transfer oil to heat the walls of the vessel and subsequently heat the product inside. This often requires scrape-surface arms to wipe the walls of the vessel and an additional mechanism with propellers to mix the product for effective and uniform heating. While mature and very well developed, this process in general is inefficient because of indirect heating of the product. Despite common misconceptions, microwaves can be applied to products in a metallic vessel to heat them directly. Microwave technology is also mature and is used in many households and industrial applications including drying, tempering, and cooking. But, the application of microwaves to a metal vessel for processing grease started in 2010 and was patented in 2012. This article provides an update on the enhancements to the technology and changes that should help to grow the use of microwaves in varied industrial uses.

Microwave heating eliminates the need for jackets on vessels and the heat transfer media. Instead, electrical energy is converted to microwaves; and microwaves are applied directly to the product to heat. This process, in general does not require scraped surface agitation and mechanical mixing as microwaves can penetrate the product and heat uniformly with some required mixing through pump circulation. In case of thicker products mixing arms can be used for better mixing but no surface scraping is needed since the vessel walls are not heated externally.


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