Thermal afterburning

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The thermal post-combustion (TNV) ( English thermal oxidizer ), thermal combustion or thermal emission control is a process for thermal waste gas purification . It is usually carried out using additional energy and is preferably used to reduce total carbon emissions .

Basics

The exhaust gas loaded with combustible - usually organic - compounds is burned in a combustion chamber at temperatures which are usually above 800 ° C. A burner is required to heat the combustion chamber and maintain the required operating temperature . The design of the burner can be very different in systems for thermal post-combustion. For example, point burners, swirl burners or surface burners can be used. An autothermal operation of the plant is from a content of total carbon of about 5 g / m 3 possible. If this is not possible, liquid or gaseous fuel or a combination of both must be added to the exhaust gas. A supply of combustion air is also necessary if the exhaust gas contains too little molecular oxygen. Residence time and combustion temperature depend on the type of compounds to be burned. Since the composition of the exhaust gas can be subject to strong fluctuations, the combustion temperature to be achieved is normally regulated via the fuel supply. In the event of excessive fluctuations, such as occur, for example, during batch operation , the concentrations of the exhaust gas to be treated must be made uniform.

In order to save fuel, a continuously operating heat exchanger (recuperator) is often used, with which the exhaust gas to be burned is heated by the burned exhaust gas. The efficiency of such a heat exchanger is below that of a regenerator , but is easier to connect.

An important parameter of thermal post-combustion is the degree of burnout, which is the size of the proportion of completely converted combustible substances. It can essentially be changed by changing the parameters

to be influenced.

application

Thermal post-combustion systems are used in a wide variety of industries and companies. These are among others:

particularities

In TNV systems with recuperative heat recovery, only part of the heat generated during combustion can be used to preheat the exhaust gas. Therefore, in order to save energy costs, it is necessary to use the heat in the upstream production facility.

The reaction mechanisms of carbon monoxide and nitrogen oxides run in opposite directions, which is why it becomes more difficult to comply with any emission limits for nitrogen oxides as the combustion temperature increases. In order to keep the reaction temperatures low or to avoid temperature peaks, exhaust gas cleaning processes are often used that work on the principle of catalytic or regenerative afterburning , also to reduce fuel consumption .

If the combustion process produces inadmissibly high concentrations of pollutants such as nitrogen oxides or halogenated hydrogen compounds, a further cleaning stage must be added.

In the Claus process , thermal post-combustion is used to oxidize sulfur-containing compounds in the exhaust gas to sulfur dioxide .

literature

  • VDI 2442: 2014-02 exhaust gas cleaning; Processes and technology of thermal waste gas cleaning (Waste gas cleaning; Methods of thermal waste gas cleaning). Beuth Verlag, Berlin. ( Summary and table of contents online )

Individual evidence

  1. ^ A b c Franz Joseph Dreyhaupt (editor): VDI-Lexikon Umwelttechnik. VDI-Verlag Düsseldorf 1994, ISBN 3-18-400891-6 , pp. 839-840.
  2. ↑ Heinz Meier to Köcker: exhaust gas purification by thermal combustion; Part I: Thermal stability in the heat exchanger tube. In: Dust - cleanliness. Air . 38, No. 3, 1978, ISSN  0949-8036 , pp. 101-105.
  3. ^ Günter Baumbach: Air pollution control . Springer-Verlag Berlin, Heidelberg, New York, 2nd edition 1992, ISBN 3-540-55078-X , p. 393.
  4. ↑ Harald Menig: Air pollution control through adsorption, absorption and oxidation. Deutscher Fachschriften-Verlag, Wiesbaden 1977, ISBN 3-8078-8056-9 , p. 352.
  5. ↑ a b c VDI 2442: 2014-02 exhaust gas cleaning; Processes and technology of thermal waste gas cleaning (Waste gas cleaning; Methods of thermal waste gas cleaning). Beuth Verlag, Berlin. P. 42.
  6. ↑ VDI 3467: 2014-11 emission reduction; Production of carbon and electrographite materials (Emission control; Production of carbon and electrographite materials). Beuth Verlag, Berlin. P. 37.
  7. ↑ VDI 3892: 2015-03 Emission Reduction; Roasted Coffee Industry; Plants with a daily production of at least 0.5 tonnes of roasted coffee (emission control; roasted coffee-producing industry; plants with a minimum daily output of at least 0.5 tonnes). Beuth Verlag, Berlin. P. 30.
  8. ↑ VDI 3475 sheet 3: 2006-12 Emission reduction - systems for the mechanical-biological treatment of municipal waste (Emission control; Mechnical-biological treatment facilities for municipal solid waste). Beuth Verlag, Berlin. Pp. 89-91.
  9. ↑ VDI 2595 sheet 1: 2010-03 emission reduction; Smoking systems; Food (except fish) (Emission control; Smokehouses; Food, except for fish). Beuth Verlag, Berlin. P. 22.
  10. ↑ Otto Carlowitz, Olaf Neese: Starting points for the conceptual and operational optimization of thermal exhaust gas cleaning systems with regenerative exhaust air preheating. In: Hazardous substances - cleanliness. Air . 65, No. 7/8, 2005, ISSN  0949-8036 , pp. 320-327.
  11. ↑ Otto Carlowitz, Olaf Neese: Requirements for thermal exhaust gas cleaning systems with regard to the amended TA Luft. In: Advances in air pollution control technology - production-integrated emission reduction and exhaust gas cleaning. VDI-Verlag Düsseldorf, 2002. ISBN 3-18-091722-9 , pp. 117-128.
  12. ↑ VDI 2442: 2014-02 exhaust gas cleaning; Processes and technology of thermal waste gas cleaning (Waste gas cleaning; Methods of thermal waste gas cleaning). Beuth Verlag, Berlin. P. 6.
  13. ↑ VDI 3454 sheet 1: 2012-04 emission reduction; Claus plants (emission control; Claus units). Beuth Verlag, Berlin. P. 7.