Dual Dosing SCR Filter for NOx Conversion and Regeneration
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Solution Overview
Problem
SCR systems with SCR function-coated filters face impaired passive regeneration due to high reduction of NO2, necessitating expensive active regeneration methods, which include external hydrocarbon-based reducing agents, and struggle with efficient NOx conversion and soot load management during cold starts.
Innovation Solution
The implementation of a dual dosing unit system in SCR systems that continuously determines differential pressure over the filter and adjusts reducing agent dosing based on soot load and NOx content, allowing for optimized NOx conversion and passive regeneration without the need for external hydrocarbon-based agents, by using two dosing units to manage reducing agent distribution upstream and downstream of the SCR catalyst.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If an SCR function coated filter is used to enable early-stage NOx conversion, then NOx purification is improved, but passive regeneration capability deteriorates due to high reduction of NO2
Solution Approach 1:
The patent divides the exhaust treatment function into two separate units: an SCR function coated filter for NOx conversion and a separate dosing unit for providing reducing agents. This segmentation allows each component to perform its specialized function optimally without interfering with the other, resolving the contradiction between NOx conversion efficiency and passive regeneration capability
Solution Approach 2:
The patent introduces a dosing unit as an intermediary component that provides reducing agents (such as hydrocarbons or diethyl carbonate) to the exhaust stream. This intermediary enables passive regeneration to occur independently of the SCR function, allowing NO2 to be maintained at levels necessary for soot combustion without compromising NOx conversion efficiency
2Reliability
If active regeneration is implemented to restore filter performance, then passive regeneration capability is improved, but system complexity and cost increase due to expensive precious metal components
Solution Approach 1:
The patent enables the filter to perform self-regeneration through the action of reducing agents introduced by the dosing unit. The system uses readily available reducing agents rather than expensive precious metal catalysts, allowing the filter to restore its performance autonomously without complex active regeneration systems
Solution Approach 2:
The patent replaces expensive precious metal components with cheaper reducing agents such as hydrocarbons or diethyl carbonate. These consumable reducing agents are injected in controlled amounts to enable regeneration, providing a cost-effective alternative to expensive catalytic regeneration systems
3Productivity
If reducing agent dosing is increased to improve NOx conversion, then NOx purification is improved, but risk of ammonium slip and crystal formation increases
Solution Approach 1:
The patent employs a control unit that continuously monitors differential pressure across the filter and adjusts the dosing rate of reducing agents accordingly. This feedback mechanism ensures optimal dosing levels are maintained, improving NOx conversion while preventing excessive dosing that would lead to ammonium slip and crystal formation
Solution Approach 2:
The patent changes the type and amount of reducing agents used based on operating conditions. By selecting appropriate reducing agents (hydrocarbons or diethyl carbonate) and adjusting their dosing rates according to differential pressure readings, the system optimizes NOx conversion efficiency while minimizing harmful side effects
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 enhances passive regeneration efficiency, reduces the risk of ammonium slip and crystal formation, minimizes the need for expensive regeneration components, and enables effective NOx conversion and soot management, while allowing for early-stage exhaust gas treatment even at cold starts without waiting for the SCR catalyst to reach operational temperature.
Implementation Method 1
SCR (selective catalytic reduction) systems which comprise an SCR catalyst in which said reducing agent and NO x gas can react and be converted to nitrogen gas and water
Implementation Method 2
upstream of said SCR catalyst arranged and for SCR function coated filter
Implementation Method 3
The system has also a pump adapted to drawing said reducing agent from the container via a suction hose and supplying it via a pressure hose to a dosing unit
Data Source
Figure 1~2
Figure 3
Figure 4a~4b
AI summary
The invention relates to a method pertaining to an SCR system wherein a reducing agent is provided to an exhaust gas stream from an engine (230) for purifying said exhaust gas with respect to among other things content of NOx, wherein said SCR system comprises an SCR catalyst (265) and an upstream of said SCR catalyst (265) arranged and for SCR function coated filter (260), a first dosing unit (250a) for provision of reducing agent being arranged upstream of said filter (260) and a second dosing unit (250b) for provision of reducing agent being arranged upstream of said SCR catalyst (265) and downstream of said filter (260). The method comprises the steps of: - continuously determining a differential pressure (P) over said filter (260); - where applicable, controlling dosing of said first and said second dosing unit (250a, 250b) on the basis of the thus determined differential pressure (P) over said filter (260). 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.