Method and Apparatus for Particle-Free Exhaust Gas Reciculation for Internal Combustion Engines: 6,964,158

An exhaust gas recirculation system for reducing NOx emissions from engines, comprising an exhaust recovery means for passing an exhaust gas stream in molecular contact with a clean air engine intake stream. A molecular diffusion means separates particulate matter in the exhaust stream by molecular diffusion by exposing the two streams to each other and allowing molecular transfer to occur between the two streams, until near gas phase equilibrium is achieved. Little or no particle transfer takes place between the two streams due to their slow diffusion relative to gas phase species so that some of the oxygen present in the intake air stream is replace with with CO2 and H2O molecules from the exhaust.