Low-pressure SCR system and method for controlling same

Abstract

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).

Description

technical field [0001] The present disclosure relates to an SCR system and a control method thereof, and particularly to a low-pressure SCR system in which an SCR reactor is installed downstream of an engine turbocharger and a control method thereof. Background technique [0002] Generally, exhaust gas discharged after combustion in engines of ships, vehicles, power plants, etc. contains many suspended particles, nitrogen oxides NOx and sulfur oxides SOx. [0003] Therefore, the exhaust line of the engine is equipped with a diesel particulate filter (DPF), a selective catalytic reduction (SCR) system, a scrubber (SCRubber, SOx removal), etc. to remove harmful substances in the exhaust gas. [0004] Among them, the SCR system allows nitrogen oxides (NOx) in exhaust gas to chemically react with reducing agents such as ammonia (NH3) and urea in a catalyst layer to decompose into harmless water and nitrogen, which are then discharged. [0005] Here, the SCR catalyst is composed...

AI Technical Summary

Problems solved by technology

If a cooling system is added, the system becomes complex and costs more to run

Also, since the cooling system is also running, it reduces overall system efficiency, wastes energy, and increases operating costs

Even so, there is no guarantee that the temperature of the urea decomposition chamber will be precisely controlled at the proper level

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