Urea crystallization test method for SCR post-treatment system

Abstract

The invention discloses a urea crystallization test method for an SCR post-treatment system. The method can accurately judge the occurrence time and position of urea crystallization in the development process of a diesel engine selective catalytic reduction product and optimize and improve from the perspective of an SCR mixing structure and calibration. After optimization is completed, checking and confirmation are carried out through transient working conditions capable of reflecting actual road conditions, the urea crystallization risk in later actual operation of a product verified through the method can be greatly reduced, and losses caused by the urea crystallization risk to users and enterprises are avoided.

Description

technical field [0001] The invention relates to the technical field of tail gas post-treatment, in particular to a method for testing urea crystallization in an SCR post-treatment system. Background technique [0002] As the number of motor vehicles increases year by year, environmental pollution issues have increasingly become the focus of attention, and exhaust pollutant emission regulations have become increasingly stringent. Internal combustion engine companies have increased research on in-cylinder purification technology and post-treatment technology. As the selective catalytic reduction (SCR) system of diesel engine is more and more widely used, SCR technology has gradually matured. [0003] The principle of selective catalytic reduction (SCR) technology for diesel engines is: under certain engine operating conditions, the urea injection unit sprays the metered urea solution into the catalytic muffler through the nozzle; the mist-like urea solution and engine exhaust ...

AI Technical Summary

Problems solved by technology

However, under low-temperature exhaust conditions, the decomposition process of urea is accompanied by polymers such as cyanuric acid and melamine. Under the mixing action of these intermediate products and exhaust gas, deposits are easily formed in the mixer, and even accumulate on the end surface of the carrier, causing blockage. The mixer and the catalyst hole will cause the exhaust back pressure to increase, the NOx conversion efficiency will decrease, and the emission will not meet the standard. In severe cases, the engine torque will be limited, affecting the normal operation of the engine and the whole vehicle

[0004] With the full implementation of the National VI emission regulations for diesel vehicles, all types of diesel vehicles on the market basically adopt SCR after-treatment systems. More and more, directly affect the daily operation of users, and bring certain losses to users and enterprises

The problem of urea crystallization in the SCR system has always been the research focus of post-processing companies, engine manufacturers and vehicle manufacturers. How to reduce the risk of urea crystallization on the basis of meeting the emission requirements, domestic manufacturers are still in a relatively rough stage or verification of this problem. The method is relatively single, unable to reflect the actual road conditions and accurately assess the crystallization risk of SCR products during the development process

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