Catalytic post-combustion

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The catalytic combustion systems (COS) ( English catalytic post-combustion ) is a process for thermal waste gas purification . The process, also known as catalytic oxidation , is preferably used to reduce hydrocarbon emissions. The advantage over thermal afterburning is the lower reaction temperature.

Basics

The catalytic afterburning works on the principle of heterogeneous catalysis . An exhaust gas laden with pollutants flows through a reactor in which the catalytic converter is located. The gaseous hydrocarbons contained in the exhaust gas are ideally oxidized to carbon dioxide and water. This can be done either directly or via the formation of intermediate products .

Depending on the composition of the exhaust gas, conditioning is necessary, which consists of one or more stages. For example, particles that can act as catalyst poisons must be removed. The exhaust gas to be cleaned must also have a minimum temperature so that the light-off temperature of the catalytic converter is reached. To achieve this minimum temperature, a part of the enthalpy of the cleaned exhaust gas is transferred to the exhaust gas that has yet to be cleaned by means of a heat exchanger . Support firing is necessary for low hydrocarbon concentrations; higher concentrations allow autothermal operation .

The catalyst material usually consists of mixed oxides on oxide ceramic supports or noble metals such as platinum or palladium on metallic supports. The operating temperatures are generally between 300 ° C and 600 ° C. With ceramic carrier materials, there is a greater risk that the catalyst will be damaged if the temperature is exceeded.

In addition to the catalytic converter properties and the pressure loss , the space velocity is an essential parameter of catalytic afterburning. The space velocities in this exhaust gas cleaning process are generally around 10,000 h −1 to 40,000 h −1 , but can assume values ​​of less than 5000 h −1 for compounds that are difficult to break down .

application

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

particularities

Due to the comparatively low reaction temperatures, the use of expensive, heat-resistant materials can largely be dispensed with in catalytic post-combustion.

When recycling precious metal catalysts that have been decommissioned, the plant operator usually receives a credit from the recycling company, since the precious metal can be almost completely recovered.

literature

  • VDI 3476 sheet 2: 2010-01 exhaust gas cleaning; Process of catalytic exhaust gas purification; Oxidative processes (Waste gas cleaning; Catalytic waste gas cleaning methods; Oxidative processes). 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. 46-47.
  2. ↑ Walter Mucha, Jan Konieczynski: Influence of the process parameters in the catalytic combustion of vapors of organic compounds using the example of 1-butanol and butyl acetate. In: Hazardous substances - cleanliness. Air . 63, No. 1/2, 2003, ISSN  0949-8036 , pp. 53-57.
  3. ↑ VDI 3476 sheet 2: 2010-01 exhaust gas cleaning; Process of catalytic exhaust gas purification; Oxidative processes (Waste gas cleaning; Catalytic waste gas cleaning methods; Oxidative processes). Beuth Verlag, Berlin. P. 34.
  4. ^ Günter Baumbach: Air pollution control . Springer-Verlag Berlin, Heidelberg, New York, 2nd edition 1992, ISBN 3-540-55078-X , p. 394.
  5. ↑ VDI 2442: 2014-02 exhaust gas cleaning; Process and technology of thermal exhaust gas cleaning. Beuth Verlag, Berlin. P. 7.
  6. ↑ VDI 3476 sheet 2: 2010-01 exhaust gas cleaning exhaust gas cleaning; Process of catalytic exhaust gas purification; Oxidative processes (Waste gas cleaning; Catalytic waste gas cleaning methods; Oxidative processes). Beuth Verlag, Berlin. Pp. 41-42.
  7. ↑ VDI 3476 sheet 2: 2010-01 exhaust gas cleaning; Process of catalytic exhaust gas purification; Oxidative processes (Waste gas cleaning; Catalytic waste gas cleaning methods; Oxidative processes). Beuth Verlag, Berlin. P. 54.
  8. ↑ 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.
  9. ↑ VDI 3476 sheet 2: 2010-01 exhaust gas cleaning; Process of catalytic exhaust gas purification; Oxidative processes (Waste gas cleaning; Catalytic waste gas cleaning methods; Oxidative processes). Beuth Verlag, Berlin. P. 47.
  10. ↑ Harald Menig: Air pollution control through adsorption, absorption and oxidation. Deutscher Fachschriften-Verlag, Wiesbaden 1977, ISBN 3-8078-8056-9 , p. 415.
  11. ↑ VDI 3476 sheet 1: 2015-06 exhaust gas cleaning; Process of catalytic exhaust gas purification; Basics (Waste gas cleaning; Methods of catalytic waste gas cleaning; Fundamentals). Beuth Verlag, Berlin. P. 20.