H2O2-assisted regeneration of diesel particulate traps at typical exhaust gas temperatures

A commonly accepted method of reducing the emission of soot particles from diesel engines is to use particulate traps. They must be regenerated from time to time, usually by combustion of the soot deposit. As an alternative to the well-tested methods of thermal or catalytic regeneration, oxidation of soot (at exhaust gas temperatures) enhanced by hydrogen peroxide (H2O2) was studied. Ceramic fiber-coil soot filters were loaded by a DI diesel engine under stationary conditions at partial load. The filters were regenerated at typical exhaust gas temperatures (250 to 500 degrees C) by H2O2-assisted soot burnout. Two devices were used: filter regeneration after disconnection from the engine in a specially designed flow reactor (ex situ measurements) and direct filter regeneration in the exhaust gas system of the engine (in situ measurements). In the first case it was possible to realize a broad range of reaction conditions, independent of the engine operating conditions. The results of the eu situ oxidation of soot particles collected in a filter matrix can be represented by: dm(C)/m(C) = -kC . Y-beta . dt; beta approximate to 0.4 k(C) = 0.23 . exp (-11,033 J mol(-1)/RT)s(-1) with k(C) m(C) and beta being the apparent rate coefficient, the mass of soot collected in the filter, and the reaction order, respectively. The property Y is the ratio of the mass flow rates of H2O2 and the gas through the filter. The results of the in situ experiments could also be represented by the above rate law. (C) 1998 by The Combustion Institute.