Purification of exhaust gases - by using rich mixtures absorbing hydrocarbons and catalytically oxidising carbon monoxide

摘要

Internal combustion engines are operated using fuel-air mixts. in wt. ratios of 1:12.5 - 11.0, the exhaust gas cooled to above the dew pt. of water, the unburnt hydrocarbons adsorbed on a layer of granular active carbon and the CO oxidised over a catalyst. Pref. the adsorbed hydrocarbons are desorbed from the carbon by air and drawn back into the engine. Use of richer mixts. than the usual fuel-air ratio of around 1 : 14.5 prevents formation of oxides of nitrogen. Better utilisation of fuel by 5-20 % is achieved. The need for temps. of 750-900 degrees C, which are difficult to maintain in motor vehicles, for catalytic reduction of nitrogen oxides, is eliminated.