Gas purification techniques

Catalytic post-combustion 

For chlorinated connections catalysts as chromium/alumina, cobalt oxide and copper oxide/manganese oxide are use. Platinum based catalysts is suitable for sulphur containing components but becomes fast deactivated in the presence of chlorine. The presence of catalyst poisons such as chemical substances and substance particles can strongly reduce the life span of a catalyst. Examples of catalyst poisons are fast working poisons (vb. Phosphorus, bismuth, arsenic, antimony, lead and mercury), slow working poisons (iron, tin, silicon), reversible inhibitors (sulphur, halogen, zinc), surface maskers (organic fixed substances) and eroding -,masking components (inert particles). It is important to know the composition of the gases well so that the correct catalyst can be selected and unexpected deactivation can be avoided.

There are two different systems of catalytic post-combustion, as it happens, fixed bed and fluorescent bed systems. Fixed bed installations can be carried out with a structured catalyst or a caught bed. The structured catalyst exists from monolithic material with the necessary air canals in the direction of the gas flow. Caught bed catalysts exists from catalyst grains which in a tube, plate or barge has been brought as a result of which passes the gases. In fluorescent bed air is upward sent by the catalyst bed. By the high flow speeds the grains in the catalyst bed will move so that entirely expands and as a fluid will behave itself. Catalytic post-combustion can be combined with energy recuperation. These energy recuperation can be both recuperative and regenerative. 

The advantages of catalytic post-combustion are:

• More compactly than thermal oxidation

• Lower oxidation temperature so that less support fuel is necessary

• Low NO_x production; approximately 20 - 30% of the NO_x at thermal post-combustion

• CO are destroyed with the other components

• High constant and reliable performances possible

• By the low temperature less heat insulation has been required than
  at thermal post-combustion

• More lower fire risk with respect to thermal oxidation

The disadvantages are:

• More lower output for fox disposal than thermal oxidation

• System are sensitive for changes in energy-input of the gas

• Risk of dioxin shaping connections chlorinated at presence of

• All catalysts are liable to catalyst far grants and polluting
  substances.

• Substance must be removed for post-combustion

• Deactivated catalyst cannot be regenerated and must be removed.

Catalytic oxidation is especially applied at disposal of VOC of
solvent evaporation.
Examples apply:

• Fuel bulkloadstations

• Production of organic chemicals

• Production of rubber and polymers

• Resin production

• Attaching and drying solvent containing coatings.

• Destruction of ethylene oxide of sterilization at 140 - 235 °C and
  ongoing concentration of 3000 ppm 

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