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The term NO x represents several forms of nitrogen oxides such as NO (nitric oxide), NO 2 (nitrogen dioxide) and N 2 O (nitrous oxide, also known as laughing gas).In a gasoline engine, NO is the most common form of NO x at around 93%, while NO 2 is around 5% and the rest is N 2 O.
A nondispersive infrared sensor (or NDIR sensor) is a simple spectroscopic sensor often used as a gas detector.It is non-dispersive in the fact that no dispersive element (e.g a prism or diffraction grating as is often present in other spectrometers) is used to separate out (like a monochromator) the broadband light into a narrow spectrum suitable for gas sensing.
In atmospheric chemistry, NO x is shorthand for nitric oxide (NO) and nitrogen dioxide (NO 2), the nitrogen oxides that are most relevant for air pollution. [ 1 ] [ 2 ] These gases contribute to the formation of smog and acid rain , as well as affecting tropospheric ozone .
Semiconductor gas sensors, most commonly metal–oxide–semiconductor (MOS) sensors, [3] detect gases by a chemical reaction that takes place when the gas comes in direct contact with the surface of the sensing element, which is usually heated to temperatures between 200 °C and 500 °C.
An Orsat gas analyser or Orsat apparatus is a piece of laboratory equipment used to analyse a gas sample (typically fossil fuel flue gas) for its oxygen, carbon monoxide and carbon dioxide content. Although largely replaced by instrumental techniques, the Orsat remains a reliable method of measurement and is relatively simple to use.
Unfortunately, the production of nitrogen oxides (NO x) increases at high temperatures. The goal of EGR is thus to reduce NO x production by reducing the combustion temperatures. In modern diesel engines, the EGR gas is usually cooled with a heat exchanger to allow the introduction of a greater mass of recirculated gas. However, uncooled EGR ...
Selective catalytic reduction (SCR) means converting nitrogen oxides, also referred to as NO x with the aid of a catalyst into diatomic nitrogen (N 2), and water (H 2 O). A reductant, typically anhydrous ammonia (NH 3), aqueous ammonia (NH 4 OH), or a urea (CO(NH 2) 2) solution, is added to a stream of flue or exhaust gas and is reacted onto a ...
Heat of condensation can be captured and reused rather than lost in the flue gas. Because nitrogen from air is absent, nitrogen oxide production is greatly reduced. If the fuel contains sulfur, sulfuric acid can possibly be recovered instead of being released as a dangerous environmental pollutant or "lost" in flue gas desulfurization.