Industrial Incinerator Emission Monitoring

The most important waste gases produced by incinerators are carbon dioxide (CO₂), sulfur dioxide (SO₂), and oxides of nitrogen (NO and NO₂, together known as NO_x). The major problem with carbon dioxide is through its contribution to the enhancement of Earth's greenhouse effect. (Andros 6512 with NO sensor)

Sulfur dioxide and oxides of nitrogen are important in the development of urban smog. These gases also contribute to the deposition of acidifying substances from the atmosphere, for example, as acid rain. Within limits, sulfur dioxide and oxides of nitrogen can be removed from the waste gases of incinerators. Most rely on the reaction of sulfur dioxide with finely powdered limestone (CaCO₃) or lime [Ca(OH)₂] to form a sludge containing gypsum (CaSO₄), which is collected and discarded in a solid-waste disposal site. Emissions of oxides of nitrogen can be controlled in various ways, for example, by reacting this gas with ammonia.(6500-RM as process controller).

One of the most contentious pollution issues concerning incinerators involves the fact that various chlorinated hydrocarbons are synthesized during the incineration process, including the highly toxic chemicals known as dioxins and furans. These are formed during combustions involving chlorine-containing organic materials, at a rate influenced by the temperature of the combustion and the types of material being burned, including the presence of metallic catalysts. The synthesis of dioxins and furans is especially efficient at 572-932°F (300-500°C), when copper, aluminum, and iron are present as catalysts. These reactions are an important consideration when incineration is used to dispose of chlorinated plastics such as polyvinyl chloride (PVC, commonly used to manufacture piping and other rigid plastic products) and polychlorinated biphenyls (PCBs).

Attention to combustion conditions during incineration can greatly reduce the rate of synthesis of dioxins and furans. For example, temperatures during incineration are much hotter, typically about 1,742-2,102°F (950-1,150°C), than those required for efficient synthesis of dioxins and furans. However, the synthesis of these chemicals cannot be eliminated, so emissions of trace quantities of these chemicals from incinerators are always a concern, and a major focus of NIMBY and BANANA protests to this technology.