Low pressure scr system and its control method

Abstract

A low-pressure SCR system, comprising an SCR reactor (30); an exhaust pipeline (11), which is used to guide low-temperature exhaust gas through a turbocharger (20) to the SCR reactor (30); a urea decomposition device (40) , which has a urea decomposition chamber (41), and is configured to decompose urea to produce ammonia and deliver the produced ammonia to the SCR reactor (30); the first bypass line (13), which is used for high temperature exhaust gas from Before the engine flows into the turbocharger (20), extract a part of the high-temperature exhaust gas and guide the part of the high-temperature exhaust gas to the urea decomposition device (40); the second bypass line (14), which is configured to connect to the first bypass pipeline (13) and exhaust pipeline (11) to distribute the high-temperature exhaust gas flowing in the first bypass pipeline (13) to the exhaust pipeline (11) in order to change the supply through the first bypass pipeline (13) The flow rate of the bypass gas to the urea decomposition device (40); and the third bypass line (16), which is configured to connect the exhaust line (11) and the first bypass line (13), so that it There is a branch point (P3) in the exhaust line (11) upstream of the junction point (P2) of the second bypass line (14) with said exhaust line (11), and at the second bypass line (14 ) has a junction point (P4) in the first bypass line (13) downstream of the branch point (P1) joining said first bypass line (13), said third bypass line (16) Extracting a part of the low-temperature exhaust gas flowing in the exhaust line (11) through the turbocharger (20) and supplying the low-temperature exhaust gas to the urea decomposition device (40) as heating for cooling for urea decomposition Extra gas for gas.

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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