A Review of EGR Intercooler Soot Deposition

The exhaust gas recirculation (EGR) is an effective method for reduction of NOx emission from diesel engine. Especially the cooled EGR can get better trade off among NO_x, PM and brake specific fuel consumption (BSFC). Soot and HCs within the exhaust gas deposit onto the wall of heat exchanger when the exhaust gas flow through the intercooler and cooled down. The thermophoresis is the main mechanism of deposition, and diffusion, static charge and condensation are also affecting the deposition. The deposition in EGR intercoolers may causes the degradation in heat exchange efficiency on the order of 20%-30%, which may affect the NOx and PM emission. The deposition also increases the back pressure of the EGR intercooler and thus adversely affects the BSFC. The back pressure of fouled intercooler may be as twice as the back pressure of fresh intercooler. Temperature, soot diameter distribution and HCs concentration are main factors that affect the deposit formation process, and it is also affected by the structure, fuel and after treatment et al. Mitigation of the deposit can be achieved by controlling these factors that affect the deposit formation process. There is no effective method to remove the deposit of EGR intercooler because the deposit removal mechanisms is not fully understood. But here have some potential method for EGR intercooler regeneration based on results from some published literatures as follow: using high speed flow to blow out loose soot, HCs evaporation, soot burning, and cracking and/or flaking for water and acids condensation.