Catalytic devices types

Even if the device has been properly calibrated for the particular gas in air, some analyzers such as catalytic bead types will not function in oxygen deficient atmospheres containing less than about 10 vol% oxygen. Some portable analyzers are supplied with antistatic tubing but others are supplied with nonconductive tubing such as Tygon. 

Physical devices (catalytic devices) for the nonchemical treatment of water and, more specifically, devices for scale prevention that employ magnetic fields have been part of the water treatment marketplace around the world since its earliest days. These devices include electronic, catalytic, electrostatic, and magnetic water treatments. There are also various other types of more recent alternative technologies (to chemical treatments) now available in the marketplace. These are being promoted for use in treating all types of MU water, FW, and BW. 

It is important to have a clear picture of the detection mechanism before we introduce the different types of field-effect transistor (FET) devices and their gas sensing properties. The sensing mechanism is largely independent of the device type, since the chemical reactions responsible for the gas response are defined by the type of catalytic material processed onto the device and the operation temperature [1,2, 20, 21]. Even at a temperature of 600°C, chemical reactions occur on the catalytic metal surface at a rate of a few milliseconds, which is slower than the response time of the devices. 

Monoliths and microchannel reactors (MRs) are two of the different types of structured reactors. A thin layer of catalyst deposited on stiff 3D structures with channels or macro-pores and high lateral surface is characteristic of these catalytic devices. These structures overcome flow maldistribution, high pressure drop, and diffusional limitations in the pores that are frequently associated with the conventional packed-bed reactors (PBRs) commonly used for catalytic reactions. Compared with PBR, structured reactors have unquestionable advantages not only in lowering pressure drop and decreasing flow maldistribution, which... 

Once an undesirable material is created, the most widely used approach to exhaust emission control is the appHcation of add-on control devices (6). Eor organic vapors, these devices can be one of two types, combustion or capture. AppHcable combustion devices include thermal iaciaerators (qv), ie, rotary kilns, Hquid injection combusters, fixed hearths, and uidi2ed-bed combustors catalytic oxidi2ation devices flares or boilers/process heaters. Primary appHcable capture devices include condensers, adsorbers, and absorbers, although such techniques as precipitation and membrane filtration ate finding increased appHcation. A comparison of the primary control alternatives is shown in Table 1 (see also Absorption Adsorption Membrane technology). 

For catalytic investigations, the rotating basket or fixed basket with internal recirciilation are the standard devices nowadays, usually more convenient and less expensive than equipment with external recirculation. In the fixed basket type, an internal recirculation rate of 10 to 15 or so times the feed rate effectively eliminates external diffusional resistance, and temperature gradients. A unit holding 50 cm (3.05 in ) of catalyst can operate up to 800 K (1440 R) and 50 bar (725 psi). 

Wet air pollution control (WAPC) devices are used to treat exhaust gases from stainless steel pickling operations, thereby generating wastewater, which are treated using the selective catalytic reduction (SCR) technology in which anhydrous ammonia is injected into the gas stream prior to a catalyst to reduce NO, to nitrogen and water. The most common types of catalysts are a metal oxide, a noble metal, or zeolite. 

Nakshima et al. have fabricated p-n junction devices by employing A1 implantation to yield a p-doped layer in n-type 6H-SiC [66]. A Pt layer on top of the p-type ohmic contact (PtSi) provided both protection and a catalytic metal contact to create a chemical gas sensor device. A response (30 and 60 mV, respectively) was obtained to both 50 ppm and 100 ppm of ammonia in nitrogen at 500°C. 

Ion sputtering mass spectrometry has been applied to several problems in the analysis of solids with various types of instruments. These include studies of semiconductor devices as shown in Fig. 3. oxygen concentrations and concentration gradients and of processes of oxidation in a variety of metals, some catalytic and corrosion processes on metals, and the chemistry of trace elements in geologic specimens. The distribution of trace elements in lunar rocks has also been studied. 

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