Exhaust gas

from Wikipedia, the free encyclopedia
Condensing exhaust gas from a waste incineration plant

Exhaust gases are the gaseous waste products that arise during a material conversion process . In common parlance, they are referred to as combustion exhaust gases, i.e. the exhaust gases from a combustion .

DIN EN 1443 defines exhaust gases in such a way that they only contain gaseous combustion products, without solid soot (correctly glossy soot ) and liquid water. Flue gas and smoke contain soot. The all-encompassing term would be volatile combustion products . Depending on the textual context, the terms fire gases or, rarely, exhaust air are also used.

From a chemical point of view, exhaust gases are an aerosol , i.e. a dispersion (a heterogeneous mixture ) of solid or liquid suspended particles in gases .

Most exhaust gases are harmful and dangerous for people and the environment. For technical and industrial systems, exhaust gas cleaning is common and system-related, also legally binding.

Exhaust gases by origin

Exhaust gases from internal combustion engines

Exhaust gases from a motor vehicle

The term “exhaust gas” is particularly common in internal combustion engines ( internal combustion engines and gas turbines ). A catalytic converter is the usual compact exhaust gas cleaning system in motor vehicles and is mandatory in many countries; In addition, since 2007, diesel vehicles have had an oxidation catalytic converter, a diesel particulate filter and nitrogen oxide aftertreatment with a NOx storage catalytic converter or SCR system . A gasoline particulate filter has been widely used for gasoline systems with direct injection since 2017 .

The flow energy of the exhaust gases from combustion engines can be used to drive a turbocharger , which pre-compresses the combustion air of the engine and thus allows an increased supply of the fuel- air mixture and thus a higher engine output and an improved efficiency of the engine.

To use the thermal energy of the exhaust gases from large internal combustion engines, e.g. B. on ships, so-called. Exhaust gas boilers are used.

A reduction in pollutant emissions can be achieved in internal combustion engines primarily through optimal combustion control with regard to temperature and air ratio.


HC [g / km] CO [g / km] NO x [g / km] PM [g / km] Carbon dioxide [g / km]
Real emissions 1970 9 72.3 2.5 0.25
Real emissions 2000 1.75 13.06 0.87 258
Comparison: Euro 4 standard (gasoline engine) 0.1 1 0.08

Exhaust gases from technical incineration plants

Exhaust gases from gas heating boilers typically contain carbon monoxide , carbon dioxide , sulfur oxides , nitrogen oxides and water vapor , as well as small amounts of dust and soot . Chlorine , fluorine and phosphorus can be included if they were included in the burned materials.

Exhaust gases from large-scale, fixed furnaces and incineration plants (e.g. power plants ) are usually referred to as flue gases , even if they do not contain any noteworthy “ smoke ” in the classic sense ( soot and dust particles). The exhaust gas from gas firing or the exhaust gas after flue gas cleaning ( dedusting ) is practically free of dust.

Combustion calculations with the corresponding exhaust gas compositions are particularly efficient for the heating technology application area using a Boie calculation algorithm .

Exhaust gases from fireplaces and fires

"Combustion gases", ie exhaust gases from open fires , smaller fireplaces such as campfires or barbecues and especially fires are usually referred to as smoke , and more rarely also as smoke gases.

Cold exhaust gases that are not produced by burns

Cold exhaust gases (<100 ° C), which do not come from combustion but from another process and which mainly consist of air, are also referred to as " exhaust air ". Depending on the type of process, such exhaust air can also be heavily contaminated with pollutants, especially dusts, vapors, volatile organic compounds, etc.

Environmental and health damage

Exhaust fumes contain no cleaning usually polluting , environmentally and harmful pollutants . For reasons of environmental protection, there are legal regulations depending on the country to limit the pollutants. In Germany, the release of such emissions is regulated by the Federal Immission Control Act (BImSchG) with the corresponding implementing ordinances (BImSchV) and / or the technical instructions for keeping the air clean (TA Luft). Often, exhaust gas cleaning is necessary to achieve the maximum limit values ​​specified in these regulations. A high chimney can also control the spread of emissions and achieve dilution.

Pollutants in exhaust gases
Pollutant source effect
Carbon dioxide (CO 2 ) fossil fuels, organic substances makes a contribution to global warming through the greenhouse effect ; As one of the main components of the combustion exhaust gases, it can displace the oxygen-containing air in high volumes and thus cause asphyxiation
Sulfur oxides (SO x ) sulphurous petroleum, proteins by formation of sulfuric acid produced acid rain , which for forest death and damage to buildings by flue gas weathering leads (especially in natural stone and metals).
Hydrochloric acid (HCl) mainly from PVC burn-off With the appropriate heating system, toxic dioxins and furans are produced
Nitrogen oxides (NO x ) Due to the temperature control, atmospheric nitrogen is incorporated into car exhaust gases that are not treated with a catalytic converter Nitrous gases are poisonous , acid rain leads to nitrogen being added to the soil and thus to eutrophication ; the by-product nitric acid also causes damage to buildings.
Carbon monoxide (CO) incomplete combustion of carbonaceous fuels in the absence of oxygen toxic
Hydrocarbons (C m H n ) Incomplete combustion / decomposition of fuels containing hydrocarbons or their heating carcinogen
Heavy metals through (formerly) lead in gasoline, through wood treated with copper salts, when burning garbage, sewage sludge toxic , carcinogenic
NMVOC Ozone formation (→ smog )
particulate matter
Fly ash

See also


Web links

Wiktionary: exhaust gas  - explanations of meanings, word origins, synonyms, translations

Individual evidence

  1. H.Göddekke, A.Höß, A.Kalisch, E. Memmert, R.Michel, W.Münz, D.Stehmeier, I. Steiglechner, H.Vogel: Exhaust systems. Commentary on DIN EN 15287-1, 2nd extended edition . Beuth Verlag, Berlin Vienna Zurich 2009, ISBN 978-3-410-16295-7 ( limited preview in Google book search).
  2. Duden: Rauchgas
  3. Christof Vieweg: Fine dust: petrol engines also need a filter . In: The time . February 25, 2017, ISSN  0044-2070 ( zeit.de [accessed December 11, 2019]).
  4. ^ Environment: Senate wins Clean Car Race . In: Nature . tape 228 , no. 5266 , October 1970, p. 11-12 , doi : 10.1038 / 228011b0 ( PDF ).
  5. ^ Average Annual Emissions and Fuel Consumption for Passenger Cars and Light Trucks . In: Transportation and Air Quality . United States Environmental Protection Agency.
  6. ^ Internet lexicon heating and ventilation technology, entry chimney , Bruno Bosy, In: Bosy-Online.de
  7. Bernd Glück: "Material values ​​and combustion calculation" .