Flare kilns

Flare kilns, pot kilns and field kilns include a number of designs, which may be roughly cylindrical, rectangular or other suitable shapes (Fig. 16.2). Wood is placed on the grate beneath a crude stone arch (or arches). Progressively smaller lumps of stone are placed above the arch(es). The wood is lit and the rate of combustion is adjusted by controlling the air flow which enters via the ash pits. Ad-... 

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). 

Thermal oxidisers are used to reduce emissions from almost all VOC sources, including reactor vents, distillation vents, solvent operations and operations performed in ovens, dryers and kilns. They can handle minor fluctuations in flow, but excess fluctuations require the use of a flare. Their fuel consumption can be high, when low-loaded waste gases are fed, so thermal units are best suited for smaller process applications with moderate to high VOC loadings. 

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