Pollution Control Technology 193
and performance. In general, the use of electric energy for transport as well
as for other urban energy needs could drastically improve the atmosphere
of cities. Of course, the production of electricity will environmentally burden some other areas, while the production of cleaner fuels requires energy
consumption. Nevertheless, it is generally easier to deal with the pollution
caused by a few assembled energy production stations than the pollution
caused by cars and other scattered sources of burning, especially inside the
city. Many specific technical and financial problems should be resolved in
order for the above possibilities to become effective actions.
The other technological direction for dealing with atmospheric pollution
is the removal of pollutants from flue-gases through the proper treatment,
their better dispersion in the atmosphere, e.g. with tall chimneys, and the
creation of conditions for more proper burnings so that CO, SO 2 , NO and
unburned hydrocarbons’ emissions are reduced.
Industry applies a great variety of treatment methods depending on the
kind of pollutants and also on the kind and the scale of the industrial unit or
other special conditions. For the removal of SO 2 various methods are used:
binding of sulphur in ammonium sulphate by the use of ammonia, conversion of SO 2 to H 2 SO 4 under suitable temperature and humidity conditions
in the presence of fine-grained coke by which it is absorbed, addition of
lime in the burning chamber and then removal of the formed CaSO 4 dry
dust through leaching etc. The removal of nitrogen oxides in industry is
possible by, among other methods, their absorption by alkaline solutions
and their reduction to ammonia in the presence of a catalyst. When the
oxides are produced by burning, decrease of their production can be pursued by proper design and function of the burning system. The removal
of suspended solids can generally be carried out by channelling the gases
through a suitable treatment chamber where a force (gravity, electrostatic,
centrifugal) removes them from the gases’ current. CO and hydrocarbon
emission control is achieved in industry by suitable conditions of burning
and by complementary facilities for burning the generated exhaust fumes.
During the last decade of the 20th century, significant improvements in
gasoline-powered cars were applied thanks to the use of catalytic converters
made of noble metals, together with lead-free gasoline. The operation of
catalytic converters is impossible if the gasoline contains lead. Three-way
catalytic converters facilitate the oxidation of carbon monoxide and hydrocarbons to carbon dioxide and water vapours, while at the same time they
achieve the reduction of nitrogen monoxide to molecular nitrogen gas.
The result is a significant decrease of the atmospheric pollutants of cities,
i.e. CO, NO x (nitrogen oxides) and hydrocarbons and the secondary pollutants of photochemical smog. The performance of catalytic converters in
ideal conditions reaches 80–90%; to achieve this performance good maintenance is necessary; when the catalyst is cold, high performance cannot
be achieved in a short drive. It should not be expected that the decrease of
and performance. In general, the use of electric energy for transport as well
as for other urban energy needs could drastically improve the atmosphere
of cities. Of course, the production of electricity will environmentally burden some other areas, while the production of cleaner fuels requires energy
consumption. Nevertheless, it is generally easier to deal with the pollution
caused by a few assembled energy production stations than the pollution
caused by cars and other scattered sources of burning, especially inside the
city. Many specific technical and financial problems should be resolved in
order for the above possibilities to become effective actions.
The other technological direction for dealing with atmospheric pollution
is the removal of pollutants from flue-gases through the proper treatment,
their better dispersion in the atmosphere, e.g. with tall chimneys, and the
creation of conditions for more proper burnings so that CO, SO 2 , NO and
unburned hydrocarbons’ emissions are reduced.
Industry applies a great variety of treatment methods depending on the
kind of pollutants and also on the kind and the scale of the industrial unit or
other special conditions. For the removal of SO 2 various methods are used:
binding of sulphur in ammonium sulphate by the use of ammonia, conversion of SO 2 to H 2 SO 4 under suitable temperature and humidity conditions
in the presence of fine-grained coke by which it is absorbed, addition of
lime in the burning chamber and then removal of the formed CaSO 4 dry
dust through leaching etc. The removal of nitrogen oxides in industry is
possible by, among other methods, their absorption by alkaline solutions
and their reduction to ammonia in the presence of a catalyst. When the
oxides are produced by burning, decrease of their production can be pursued by proper design and function of the burning system. The removal
of suspended solids can generally be carried out by channelling the gases
through a suitable treatment chamber where a force (gravity, electrostatic,
centrifugal) removes them from the gases’ current. CO and hydrocarbon
emission control is achieved in industry by suitable conditions of burning
and by complementary facilities for burning the generated exhaust fumes.
During the last decade of the 20th century, significant improvements in
gasoline-powered cars were applied thanks to the use of catalytic converters
made of noble metals, together with lead-free gasoline. The operation of
catalytic converters is impossible if the gasoline contains lead. Three-way
catalytic converters facilitate the oxidation of carbon monoxide and hydrocarbons to carbon dioxide and water vapours, while at the same time they
achieve the reduction of nitrogen monoxide to molecular nitrogen gas.
The result is a significant decrease of the atmospheric pollutants of cities,
i.e. CO, NO x (nitrogen oxides) and hydrocarbons and the secondary pollutants of photochemical smog. The performance of catalytic converters in
ideal conditions reaches 80–90%; to achieve this performance good maintenance is necessary; when the catalyst is cold, high performance cannot
be achieved in a short drive. It should not be expected that the decrease of