Exhaust Gas Catalyst Layout to Cut N2O During High-NOx Treatment
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Solution Overview
Problem
Existing exhaust gas treatment methods produce excessive dinitrogen monoxide (N2O) as a by-product when treating exhaust gases with high nitrogen oxide concentrations, particularly in combustion exhaust gases, due to the oxidative decomposition of ammonia.
Innovation Solution
An exhaust gas treatment device comprising a first denitration catalyst followed by a catalyst unit with an ammonia decomposition catalyst and a second denitration catalyst, where the ratio of ammonia concentration to dinitrogen monoxide concentration is maintained at not less than 10.0, and the length of the first denitration catalyst is at least three times that of the ammonia decomposition catalyst, with a specific ratio of catalyst lengths satisfying y ≥ 0.003x, to reduce nitrogen oxides and ammonia while suppressing N2O production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a large amount of ammonia is added as a reducing agent to sufficiently reduce nitrogen oxide in exhaust gas with high nitrogen oxide concentration, then nitrogen oxide reduction efficiency is improved, but the amount of dinitrogen monoxide produced as a by-product increases
Solution Approach 1:
The catalyst system is segmented into multiple functional zones: a first denitration catalyst layer for initial NOx reduction, followed by an ammonia decomposition catalyst layer to break down excess ammonia before it reaches the selective catalytic reduction catalyst. This segmentation prevents the formation of excessive N2O by removing the harmful ammonia intermediate before it can react to form the greenhouse gas byproduct.
Solution Approach 2:
The ammonia decomposition catalyst acts as an intermediary component between the denitration catalyst and the selective catalytic reduction catalyst. It mediates the ammonia concentration by decomposing excess ammonia into nitrogen and hydrogen, thereby controlling the amount of ammonia that reaches the SCR catalyst and preventing excessive N2O formation while maintaining NOx reduction efficiency.
2Quantity of substance
If an ammonia decomposition catalyst is added to decompose ammonia in exhaust gas, then unreacted ammonia is reduced, but dinitrogen monoxide is produced as a by-product of the oxidative decomposition reaction
Solution Approach 1:
The invention merges multiple catalyst functions into a single integrated catalyst composition containing both denitration catalyst components and ammonia decomposition catalyst components. This combined catalyst performs both NOx reduction and ammonia decomposition simultaneously, allowing the ammonia to be decomposed in situ where it is needed, preventing N2O formation while maintaining treatment efficiency.
Solution Approach 2:
The catalyst composition is designed with specific metal components (such as Cu, Fe, or Mn) and support materials (such as Al2O3, TiO2, or CeO2) that create optimal reaction conditions for ammonia decomposition. By controlling the physical and chemical parameters of the catalyst (metal loading, surface area, pore structure), the system promotes selective ammonia decomposition into nitrogen and hydrogen rather than oxidative decomposition that would produce N2O.
3Reliability
If multiple catalyst layers are arranged in sequence to treat exhaust gas, then treatment effectiveness is improved, but device complexity increases
Solution Approach 1:
The invention combines multiple catalyst functions into a single integrated catalyst composition or layer, eliminating the need for separate, multi-layered catalyst systems. The unified catalyst contains both denitration and ammonia decomposition functionalities, simplifying the overall device structure while maintaining the effectiveness of sequential treatment processes.
Solution Approach 2:
The catalyst composition is designed with multi-functionality, capable of performing both nitrogen oxide reduction and ammonia decomposition within the same catalyst bed. This universal catalyst approach maintains the treatment effectiveness of multiple catalyst layers while reducing device complexity by eliminating the need for separate catalyst units and complex flow distribution systems.
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
Effectively reduces nitrogen oxides and ammonia in exhaust gases while minimizing dinitrogen monoxide production, achieving concentrations below predetermined limits.
Implementation Method 1
a first denitration catalyst for reducing a nitrogen oxide in the exhaust gas
Implementation Method 2
an ammonia decomposition catalyst for decomposing ammonia in the exhaust gas
Implementation Method 3
the ammonia is oxidatively decomposed and nitrogen is mainly produced
Implementation Method 4
a second denitration catalyst for reducing the nitrogen oxide in the exhaust gas
Data Source
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AI summary
An exhaust gas treatment device is an exhaust gas treatment device for treating exhaust gas generated by combusting fuel, including: a first denitration catalyst for reducing a nitrogen oxide in the exhaust gas; and at least one catalyst unit each including an ammonia decomposition catalyst for decomposing ammonia in the exhaust gas, the ammonia decomposition catalyst being disposed downstream of the first denitration catalyst in an exhaust gas flow, and a second denitration catalyst for reducing the nitrogen oxide in the exhaust gas, the second denitration catalyst being disposed downstream of the ammonia decomposition catalyst in the exhaust gas flow, wherein a ratio (CNH3_FSCR/CN2O_SYS) of an ammonia concentration (CNH3_FSCR) at an outlet of the first denitration catalyst to a dinitrogen monoxide concentration (CN2O_SYS) at an outlet of the at least one catalyst unit is not less than 10.0.