Exhaust Gas Purification System Dosing Valve Crystallization Prevention
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
During diesel engine exhaust gas purification, the high-temperature DPF regeneration process causes urea water in the dosing valve to crystallize and adhere, leading to potential malfunction and failure in controlling urea water injection.
Innovation Solution
An exhaust gas purification system with a Dosing Control Unit (DCU) that controls the dosing valve and supply module to intermittently open and return urea water to the tank, preventing adhesion by managing urea water injection based on SCR catalyst NH3 levels and exhaust gas temperature, ensuring the urea water is below crystallization temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If DPF regeneration is performed by flowing high-temperature exhaust gas, then PM trapped by DPF is oxidized and removed, but urea water in the dosing valve is heated to high temperature and crystallizes causing adhesion and potential malfunction
Solution Approach 1:
The system performs preliminary action by detecting the differential pressure across the DPF before regeneration and determining the need for regeneration in advance. The control unit prepares the dosing valve by controlling urea water supply to be stopped or reduced before high-temperature exhaust gas flows into the DPF, preventing urea water crystallization and adhesion before the harmful high-temperature condition occurs
Solution Approach 2:
The control unit acts as an intermediary between the DPF regeneration process and the dosing valve operation. It receives the regeneration determination result and mediates the dosing valve control accordingly, stopping or reducing urea water supply during regeneration to prevent the harmful effect of urea water crystallization while allowing the beneficial DPF regeneration to proceed
2Reliability
If urea water supply is stopped before DPF regeneration to avoid NH3 slip, then NH3 accumulated in SCR catalyst is preserved, but urea water accumulates in the dosing valve and is heated causing crystallization and adhesion
Solution Approach 1:
The control unit dynamically changes the operational parameters of the dosing valve based on the DPF regeneration status. During regeneration, it adjusts the urea water supply parameter to be stopped or reduced, which prevents both NH3 slip (by maintaining appropriate NH3 levels in SCR catalyst) and urea water crystallization (by preventing accumulation in the dosing valve exposed to high temperature)
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
Prevents urea water adhesion in the dosing valve during DPF regeneration, thereby maintaining proper urea water injection control and preventing dosing valve malfunction.
Implementation Method 1
when the urea water is heated to higher than or equal to a boiling point of C° C., moisture thereof starts to vaporize and gas α is generated through a solid matter w
Implementation Method 2
The gas α is crystallized at about D° C., and a solid matter x is generated. Within a temperature range of C° C. to D° C., the solid matter w, the gas α, and the solid matter x are left mixed with each other
Implementation Method 3
uses an SCR system including the SCR device to supply urea water stored in a urea tank to an exhaust gas upstream of SCR, generate NH3 by the heat of the exhaust gas, and reduce and purify NOx on an SCR catalyst by the NH3
Implementation Method 4
uses the DPF to trap a PM in exhaust gas
Implementation Method 5
raising a temperature of the exhaust gas to about 600° C. and burning and removing the PM trapped by the DPF by the high-temperature exhaust gas
Data Source
AI summary
An exhaust gas purification system includes a dosing control unit that controls a supply module to supply urea water between a dosing valve and a urea tank in order to remove urea water accumulated in the dosing valve, when receiving a diesel particulate filter regeneration authorization request from an engine control unit, and then transmits the authorization to the engine control unit, when determining that an NH3 amount of a selective reduction catalyst is less than or equal to a prescribed value.