Process and apparatus for purifying an exhaust gas laden with vapours of a foreign substance with recovery of the foreign substance

摘要

In a process for purifying exhaust air laden with petrol vapours with recovery of the petrol, which process is based on condensing out the petrol by cooling the exhaust air, to achieve the low temperatures required for a virtually complete separation, the refrigerant medium provided for a heat exchanger 6 serving for separation is liquid nitrogen 17. To avoid the atmospheric oxygen condensing out and the formation of explosive mixtures connected with this and to create a sufficient refrigeration capacity with discontinuous feed of exhaust air, the heat exchange with the exhaust air is exclusively carried out via a buffer medium which has a transition between a solid and a liquid phase at a transformation temperature at or below the condensation temperature of the petrol vapours, but above the condensation temperature of the atmospheric oxygen, the buffer medium being cooled by the liquid nitrogen precisely to the conversion to the solid phase. <IMAGE>