Urea Composition with Paraffin for SCR Deposit Prevention
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Solution Overview
Problem
Existing SCR systems for diesel engine exhaust treatment face issues with deposit formation and foaming in urea-based solutions, leading to blockages and inaccurate metering, which are not adequately addressed by current additives.
Innovation Solution
An aqueous composition comprising urea and C20-C36 paraffins, stabilized by nonionic surfactants and emulsion stabilizers, is introduced to prevent deposit formation and reduce foaming, allowing precise metering and stable handling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If urea is injected into the exhaust system for SCR treatment, then nitrogen oxides are reduced, but deposit formation occurs in the exhaust pipes
Solution Approach 1:
A surfactant is introduced as an intermediary substance between the urea and the exhaust pipe surface. The surfactant modifies the interaction between urea droplets and the pipe wall, preventing direct adhesion and deposit formation while allowing the SCR reaction to proceed effectively.
Solution Approach 2:
The physical-chemical parameters of the urea solution are modified by adding surfactants. This changes the surface tension, wetting properties, and droplet behavior of the urea solution, preventing it from adhering to the pipe wall and forming deposits while maintaining its SCR functionality.
2Ease of operation
If urea solution is handled in storage tanks, then urea is available for injection, but foaming occurs disrupting control
Solution Approach 1:
The surfactant acts as an intermediary that modifies the foam formation behavior of the urea solution. It controls the surface tension and bubble stability, preventing excessive foaming during tank filling and injection operations, thereby ensuring precise control of the injected amount.
3Loss of time
If urea droplets settle on pipe wall due to limited vaporization time, then deposits form from incomplete decomposition, but higher temperatures are rarely reached
Solution Approach 1:
The surfactant serves as a protective intermediary layer between the urea droplets and the pipe wall. It prevents direct contact and adhesion of urea to the pipe surface, allowing complete vaporization and decomposition even within limited timeframes, thereby preventing cyanuric acid deposit formation.
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
The composition effectively reduces deposit formation in SCR systems, minimizes foaming, and enables precise control of urea injection, improving system efficiency and handling stability.
Implementation Method 1
it has been observed that some ammonia precursor solutions, particularly urea, with additives, tend to foam when introduced into the tank. This foaming hinders tank filling and can lead to overflow. Furthermore, this foaming can cause air to be injected into the system.
Implementation Method 2
An aqueous composition comprising urea and C20-C36 paraffins, stabilized by nonionic surfactants and emulsion stabilizers, is introduced to prevent deposit formation and reduce foaming, allowing precise metering and stable handling.
Implementation Method 3
The urea, injected at an average temperature generally ranging from 150 to 400°C, gradually hydrolyzes into gaseous ammonia.
Implementation Method 4
The urea, injected at an average temperature generally ranging from 150 to 400°C, gradually hydrolyzes into gaseous ammonia.
Data Source
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AI summary
An aqueous composition comprising an NOx reducing agent or a precursor of such an agent, in particular urea, and at least one paraffin dispersed in the aqueous phase. Such a composition can be used for reducing the formation of deposits in an SCR exhaust system while preventing foaming during the handling of same.