Microwave use with chemicals to grow
National Centre for Industrial Microwave Processing (NCIMP), operated under the aegis of the High Power RF Faraday Partnership and based at the University of Nottingham, now is working with companies to evaluate the economics of microwave technology for specific applications and, for promising ones, to develop industrial-scale equipment.
This month [August], Stephen Bowater, project director at the partnership, and Sam Kingman of the University of Nottingham outlined at the International Microwave Power Institute conference in Boston the drivers for increased industrial application of the technology and the methodology the center uses to identify opportunities and develop equipment.
While some niche industrial applications have relied on high-power microwaves for decades, the technology has not broken into the mainstream of processing because of its high capital cost, they note. However, the increasing prices of fossil fuels and their environmental issues, coupled with microwaves innate advantages, are reinvigorating the prospects for broader industrial use, they say.
Unlike conventional heating, which relies on the thermal conductivity of the load for heat transfer, microwaves can heat the load both volumetrically and evenly without any high thermal gradients. This can lead to a reduction in processing time from, in some cases, days to hours. As a result of using microwave heating, it is also conceivable to change from batch to continuous processing, thus increasing the output per unit volume of factory space. This reduction in processing time also comes with a subsequent decrease in energy consumption of up to 95%, explains Bowater.
These very high energy savings are achievable for processes which require selective heating for instance, chemical processes which need to drive out water from the structure of a material. The microwave energy will be deposited in the water, heating this in preference to other phases. This will boil off the water quicker with a much smaller rise in the average temperature of the load. Additional benefit is gained by designing this as a continuous flow process which could, for example, help overcome mass-transfer limitations, he adds.
Installed microwave processing equipment is very reliable, Bowater notes. The NCIMP modular equipment design will ensure that, with a planned maintenance program, availability figures of over 99% will be achieved at energy conversion efficiencies of over 90% at industrial heating frequencies. Process equipment manufacturers will supply the commercial units, with NCIMP providing ongoing support.
NCIMP was established as a separate research center at the School of Chemical, Environmental and Mining Engineering at the University of Nottingham at the end of 2005. The center already is working with ten companies, ranging from multinationals to miniscule ones, including three in the chemical industry, notes Bowater. Six programs are underway, with two involving the demonstration of industrial-scale equipment. While NCIMP has not been in existence long enough for any of its work to reach plants yet, one of the demonstration-phase chemical-related projects boasts a likely payback of 28 months with oil at $65/bbl., he asserts. This process also will deliver greater process control, with the ability to process all product grades in one machine, rather than two different machines, as currently used, he says, adding that it also will lead to an improved working environment, thanks to less dust, heat, etc.