Diesel Exhaust Fluid Additives for Low-Deposit Urea Decomposition
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Solution Overview
Problem
Existing diesel exhaust fluid (DEF) formulations fail to effectively reduce nitrogen oxide emissions and prevent the deposition of urea and its decomposition compounds on exhaust pipe walls, leading to reduced fuel efficiency, catalyst damage, and increased particulate emissions.
Innovation Solution
A DEF composition comprising 15-40 wt% urea, purified water, and a compound additive such as sugar, acetic acid, or ammonium acetate that generates water at high temperatures to interfere with competing reactions, promoting complete urea decomposition and reducing undesired deposits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If conventional DEF formulations (32.5 wt% urea in water) are used for selective catalytic reduction, then nitrogen oxide emissions can be reduced, but urea deposits accumulate on exhaust pipe walls
Solution Approach 1:
The patent modifies the chemical composition parameters of DEF by adding specific compounds (sugars, carboxylic acids, or their salts) to alter the decomposition behavior of urea. These additives change the reaction pathways and intermediates formed during urea decomposition, preventing deposit formation while maintaining NOx reduction capability.
Solution Approach 2:
The additives act as intermediaries in the urea decomposition process. They interfere with the formation of harmful intermediates (such as isocyanic acid and cyanuric acid) that lead to deposits, redirecting the reaction pathways toward beneficial products (ammonia and carbon dioxide) without compromising the overall NOx reduction function.
2Reliability
If urea decomposition is incomplete, then deposits form in the exhaust system, but increasing decomposition completeness may require higher temperatures that increase fuel consumption
Solution Approach 1:
The patent replaces the reliance on thermal energy (heat) alone to drive complete urea decomposition with a chemical mechanism. The additives catalyze or facilitate the decomposition reaction, allowing complete decomposition to occur at lower temperatures than would be required through thermal processes alone, thereby reducing fuel consumption while maintaining decomposition completeness.
3Productivity
If DEF is dosed into hot exhaust pipes, then urea decomposes to ammonia for NOx reduction, but intermediate compounds stick to pipe walls and form deposits
Solution Approach 1:
The patent converts the harmful effect of intermediate compounds (which normally stick to walls and form deposits) into a beneficial process. The additives modify the intermediate compounds' properties or reaction pathways so that they either decompose further into harmless substances (ammonia, carbon dioxide, water) or remain in the gas phase without adhering to surfaces, thus transforming the deposition problem into an enhanced decomposition process.
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 solution enhances NOx reduction efficiency, minimizes urea deposition, and extends catalyst life by ensuring complete urea decomposition and reducing particulate emissions without significant fuel economy penalties.
Implementation Method 1
a compound additive that generates water in the diesel exhaust streams at temperatures greater than 100° C. (or 125° C. or 150° C.), interferes with competing reactions that would otherwise prevent decomposition of urea
Implementation Method 2
Urea is broken down (i.e., decomposes) through thermolysis and hydrolysis to ammonia and carbon dioxide when dosed by dispersion into the hot exhaust pipe
Implementation Method 3
Urea is broken down (i.e., decomposes) through thermolysis and hydrolysis to ammonia and carbon dioxide when dosed by dispersion into the hot exhaust pipe
Data Source
AI summary
A diesel exhaust fluid (DEF) for reducing nitrogen oxides in diesel exhaust streams while also reducing the deposition of urea and/or urea decomposition compounds in diesel exhaust systems of engines that use DEF and require selective catalytic reduction. The DEF has about 15 wt. % to about 40 wt % urea; substantially purified water; and a compound additive that generates water in the diesel exhaust streams at temperatures greater than 100° C., interferes with competing reactions that would otherwise prevent decomposition of urea or produce undesired decomposition deposit compounds including biuret, cyanuric acid, ammelide, ammeline, and melamine, or both generates water and interferes with the competing reactions. The compound additive is preferably a sugar, acetic acid, or ammonium acetate. Also disclosed are a related method of using the DEF in a diesel exhaust system and a system including the DEF as one component.