Microwave industrial cavity

Fiber-optic thermometers can be applied up to 300°C, but are too fragile for real industrial applications. In turn, optical pyrometers and thermocouples can be used, but pyrometers measure only surface temperatures which in fact can be lower than the interior temperatures in reaction mixtures. Application of thermocouples which in case of microwaves are metallic probes, screened against microwaves, can result in arcing between the thermocouple shield and the cavity walls leading to failures in thermocouple performance. 

The CMR and MBRs provided the basis for modern commercial microwave reactors, including robotically operated automated systems that are now widely employed in synthetic research and pilot-scale laboratories in academia and industry [13]. Since 2000, commercial microwave reactors have become available. Batch systems, produced by three major companies in Italy and Germany, Sweden and the United States, typically operate on a scale from 0.5 mL up to 2 L. Other companies based in Austria, Poland and Japan have also recently entered the market. Systems possessing either multimodal or monomodal cavities are produced with one recent addition being a single unit capable of performing in either mode as required. Microwave reactors are employed extensively in chemical discovery where successive reactions can be performed rapidly in parallel or sequentially. One manufacturer recently estimated that about 10000 reactions per week were performed in its systems alone. This indicates the extent to which microwave chemistry in closed vessels has dramatically influenced approaches to synthesis. 

A helium microwave cavity plasma or MIP serves as the heart of a unique instmment dedicated to the analysis of particles with diameters between 1 and 20 pim. The analysis of small particles is becoming increasingly important in fields as diverse as the semiconductor industry where extremely low levels of contaminants can destroy semiconductor chips, to indoor and outdoor air quality and the health impact of respirable particles. This instrument is basically an atomic emission spectrometer, but designed to count particles, calculate particle size, and determine the chemical composition of each particle analyzed, one by one. 

Cavity applicators are a large class of applicators, but they are probably the most common type. Home microwave ovens are a typical example. They consist of metal boxes, which may be used for conveyor systems or in batch operations. The microwave energy may be coupled into this applicator by means of waveguide or coaxial cable through a single port or multiple ports (see Figure 13.7). There is an industrial system in which over 100 magnetrons are separately introduced... 

A resonant cavity has been used to excite and provide power to a low pressure mercury vapor lamp to produce UV radiation with 154 mn and 180 nm wavelengths. The conversion efficiency of microwave power into UV light power is very efficient at 80 % (Lucas 2005). This UV is used for germicidal activity within the food and drinks industry. By irradiating food with UV before MAP packaging doubles the shelf life. Likewise, a similar effect has been obtained with Turkish beers (Boza)... 

Microwaves are electromagnetic waves with frequencies in the range of 300-300 000 MHz. Microwave radiation neither possesses ionizing characteristics nor produces changes in the molecular structure it can be used to measure the movement of molecules due to the migration of ions and the rotation of dipoles. Of the four frequencies most often used in industrial and scientific applications (915 25, 2450 13, 5800 75, and 22125 125 MHz), the one with a power range 600-700 W (domestic ovens) is 2450 MHz, which can provide, to the microwave cavity, 43 500 cal in 5 min. 

Fig. 3. Development of standing waves TE103 resonant cavity electric field pattern. Reprinted from Industrial Microwave Heating, Peter Perigrinus, London (1983) [6] with permission... 

The highest performance and best safety features are the qualities of an advanced microwave extraction system in the industry. It offers fast heating of vessel together with homogeneous microwave distribution throughout the cavity. 

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