SCR Vaporizing Portion Temperature Control to Prevent Urea Crystals
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Solution Overview
Problem
SCR systems face issues with crystal formation of reducing agents, leading to reduced performance and potential plugging, which is difficult to clean and requires purifying, especially when heavy dosing occurs, as it cools the vaporizing module and forms crystals upstream of the SCR substrate.
Innovation Solution
A method that continuously monitors the temperature of the vaporizing portion in the SCR system and controls the engine's operation to avoid crystal formation by shifting modes based on fuel economy and exhaust gas purification requirements, reducing the need for reducing agents when temperatures are low, thereby preventing cooling and crystal formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If heavy dosing of reducing agent is applied to maximize NOx conversion, then exhaust gas purification is improved, but the vaporizing module temperature drops causing crystal formation
Solution Approach 1:
The control unit continuously monitors the temperature of the vaporizing module and adjusts the dosing rate of the reducing agent accordingly. When the temperature drops below a threshold, the dosing rate is reduced to prevent crystal formation, creating a closed-loop feedback system that balances purification performance with temperature maintenance
Solution Approach 2:
The dosing rate is made dynamic rather than fixed, allowing the system to adapt the reducing agent injection amount based on real-time temperature conditions. This dynamic adjustment enables the system to respond to changing thermal conditions and prevent crystal formation while maintaining optimal NOx conversion when temperatures are sufficient
2Reliability
If heavy dosing of reducing agent is applied to maximize NOx conversion, then exhaust gas purification is improved, but crystal formation occurs causing system plugging
Solution Approach 1:
The control unit takes preliminary action by reducing the dosing rate before crystal formation can occur. By monitoring temperature and proactively adjusting the dosing rate when temperature drops approach the crystal formation threshold, the system prevents the harmful effect rather than reacting after crystals have formed
Solution Approach 2:
The system uses temperature feedback to continuously adjust the dosing rate, creating a self-regulating mechanism that prevents crystal formation by reducing dosing when temperatures become too low, thus eliminating the harmful effect of plugging
3Use of energy by moving object
If the system operates with low fuel consumption modes, then fuel economy is improved, but exhaust gas temperature decreases increasing crystal formation risk
Solution Approach 1:
The dosing rate is dynamically adjusted based on exhaust gas temperature conditions. When operating in low-fuel-consumption modes that produce lower temperatures, the system automatically reduces the reducing agent dosing rate to match the reduced thermal conditions, preventing crystal formation while maintaining fuel-efficient operation
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively minimizes the risk of urea stone formation while maintaining high NOx conversion performance, optimizing fuel consumption, and ensuring environmental sustainability by adjusting engine operation modes to manage temperature and reduce reducing agent dosing.
Implementation Method 1
An SCR system comprises a vaporizing portion where supplied reducing agent is vaporized so as to effectively be mixed before treatment by an SCR substrate
Implementation Method 2
SCR (selective catalytic reduction) systems which comprise an SCR catalyst in which said reductant and NOx gas can react and be converted to nitrogen gas and water
Data Source
Figure 1~2a
Figure 2b
Figure 3
AI summary
The invention relates to a method pertaining to an SCR system wherein a reducing agent is provided an exhaust gas stream from an engine (231) for purifying the exhaust gas with respect to among other things content of NOx and wherein the SCR system comprises a vaporization portion (361) being arranged upstream a catalyst arrangement (260; 262) comprising the step of: - (s410) continuously monitoring changes of a temperature (Tmod) of said vaporizing portion. The method further comprises the step of: - controlling (s420, s430) mode of operation of said engine (231) on the basis of said changes of the temperature (Tmod) of the vaporizing portion so as to operate said engine (231) based on requirements regarding fuel economy as well as exhaust gas purification and at the same time avoid formation of crystals in said vaporizing portion (261). The invention relates also to a computer programme product comprising programme code (P) for a computer (200; 210) for implementing a method according to the invention. The invention relates also to an SCR system and a motor vehicle equipped with the SCR system.