LOW-PRESSURE SCR SYSTEM AND METHOD FOR CONTROLLING SAME

摘要

A low pressure SCR system comprises: an SCR reactor (30); an exhaust line (11) for guiding low-temperature exhaust gas, which has passed through a supercharger (20), to the SCR reactor (30); a urea-decomposing device (40) having a urea-decomposing chamber (41) for decomposing urea to produce ammonia, and sending the produced ammonia toward the SCR reactor (30); a first bypass line (13) for extracting, from an engine, a portion of high-temperature exhaust gas before being introduced into the supercharger (20) and guiding the high-temperature exhaust gas to the urea-decomposing device (40); a second bypass line (14) capable of changing the flowrate of bypass gas supplied to the urea-decomposing device (40) through the first bypass line (13), by connecting the exhaust line (11) to the first bypass line (13) so that the high-temperature exhaust gas flowing through the first bypass line (13) is distributed to the exhaust line (11); a third bypass line (16) for extracting a portion of the low-temperature exhaust gas, which has passed through the supercharger (20) and flows through the exhaust line (11), and supplying, to the urea-decomposing device (40), the low-temperature exhaust gas as additional gas to cool heated gas for decomposing urea; and a blower (50) and a bypass flowrate control valve (67) installed on the third bypass line (16) to forcibly add the exhaust gas flowing through the exhaust line (11).