A Study of the Vapor- and Particle-Phase Sulfur Species in the Heavy-Duty Diesel Engine EGR Cooler

To meet future NO, heavy-duty diesel emissions standards, exhaust gas recirculation (EGR) technology is likely to be used. To improve fuel economy and further lower emissions, the recirculated exhaust gas needs to be cooled, with the possibility that cooling of the exhaust gas may form sulfuric acid condensate in the EGR cooler. This corrosive condensate can cause EGR cooler failure and consequentially result in severe damage to the engine. Both a literature review and a preliminary experimental study were conducted. In this study, a manually controlled EGR system was installed on a 1995 Cummins Ml l-330E engine which was operated at EPA mode 9* (1800 rpm and 75% load). The Goksoyr-Ross method (1)** was used to measure the particle-phase sulfate and vapor-phase H₂SO₄ and SO₂ at the inlet and outlet locations of the EGR cooler, obtaining H₂SO₄ and SO₂ concentrations. About 0.5% of fuel sulfur in the EGR cooler was in the particle-phase. The remaining fuel sulfur was as SO₂ and vapor phase sulfuric acid. The particle phase sulfate concentrations were higher at the outlet location of the EGR cooler indicating conversion of SO₂ to sulfate as the exhaust gas is cooled.