Catalytic Oxidation

The polluted waste gases are preheated up to the specific start-up temperature of the oxidation catalyst. The organic pollutants are oxidised in the catalyst to a residual concentration, in accordance with the limit value to be complied with, with heat being released. The waste gas is preheated through waste heat usage from the pure gases or by means of support firing. With higher exotherms, additional energy recovery is possible, in addition to the waste gas preheating. In stationary operation and with ideal operating conditions, the plant runs autothermally, i.e. no support firing is necessary. What is crucial for the design of these plants is the choice of the right catalyst, taking the following parameters into account:

pollutant composition in the waste gases

pollutant concentration (incl. fluctuations)

waste gas temperature

other accompanying substances in the waste gas (e.g. dust, aerosols, etc.)

Depending on the required application, the following catalyst types are used :

precious metal catalysts

mixed oxide catalysts

Bulk catalysts or honeycomb catalysts are used.

The following substances are catalyst toxins and must therefore be removed beforehand from the waste gas to be purified catalytically:

halogen compounds

dusts and aerosols

phosphorus, sulphur and silicon compounds

heavy and alkali metals

Waste gases that are ideal for the use of catalytic combustion are therefore waste gases with pollutants containing C, H and O2 in a concentration range that does not cause any thermal overloading of the catalyst by the pollutant exotherms.