Energy efficiency of photocatalytic gas cleaning

The recovery of small amounts of organic compounds from gas streams is usually not a
viable solution and so called “end-of-pipe” processes are preferred. For the destruction of
volatile organic compounds (VOC) catalytic combustion is known as the most simple and
reliable technology. It shall be compared with photocatalysis in terms of operating energy
consumption. Photocatalysis uses light i.e. photons preferentially in the ultra-violet range as
an energy source to reach the exited state of a semi-conducting material (TiO2) which in turn
creates radicals that can destroy the organic molecules. The chlorinated hydrocarbon
trichloroethylene (TCE) is chosen as a model substance for the theoretical evaluation of the
specific energy demand. The results show that energy efficiency of photocatalysis mainly
depends on pollutant concentration, quantum yield and efficiency of the needed light source.
It is energetically more favourable than catalytic combustion when the specific energy
demand below 100W·h·m-3.
This can be achieved for an inlet concentration below 1000-1500ppm, depended on the kind of organic.