Exhaust Gas Purification Catalyst Arrangement for Desulfurization
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Solution Overview
Problem
NOx occlusion reduction type catalysts face challenges in desulfurization due to SOx occlusion, thermal degradation, and varying NOx removal efficiency across temperature ranges, especially in lean fuel conditions of diesel engines, where high-temperature and low-temperature catalysts have contrasting performance and desulfurization is difficult.
Innovation Solution
An exhaust gas purification system with an oxidation catalyst upstream of high-temperature NOx occlusion reduction type catalysts to create a rich atmosphere for desulfurization, combined with a catalyzed DPF downstream to prevent HC slip and raise temperatures for PM regeneration, and controlled hydrocarbon addition based on temperature to optimize NOx reduction across temperature ranges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an oxidation catalyst is disposed on the upstream side of the high-temperature NOx occlusion reduction type catalyst, then desulfurization is facilitated and NOx reduction efficiency is improved, but the device complexity increases
Solution Approach 1:
The patent combines multiple catalyst functions into a unified exhaust gas purification system where an oxidation catalyst is integrated upstream of the high-temperature NOx occlusion reduction type catalyst. This merging approach allows the system to perform both oxidation and NOx reduction functions in a coordinated manner, facilitating desulfurization while maintaining manageable system complexity through functional integration.
Solution Approach 2:
The oxidation catalyst performs preliminary oxidation of hydrocarbons and carbon monoxide before the exhaust gas reaches the high-temperature NOx occlusion reduction type catalyst. This preliminary action prepares the exhaust gas composition and temperature conditions optimal for subsequent desulfurization and NOx reduction processes, improving overall system efficiency.
2Reliability
If hydrocarbons are supplied to improve NOx reduction efficiency, then NOx removal performance is enhanced, but HC slip increases
Solution Approach 1:
The patent converts the potential harm of hydrocarbon addition (which could cause HC slip) into a benefit by carefully controlling the oxidation process. The oxidation catalyst upstream converts added hydrocarbons into useful reducing agents and heat for NOx reduction, while the catalyzed DPF downstream captures any unoxidized hydrocarbons, thus converting what could be harmful emissions into beneficial process inputs.
Solution Approach 2:
The system dynamically controls hydrocarbon addition parameters including the type, amount, and timing of hydrocarbon injection based on exhaust gas temperature and composition. By optimizing these parameters, the system achieves effective NOx reduction while minimizing HC slip, adapting the hydrocarbon supply strategy to prevailing operating conditions.
3Reliability
If a catalyzed DPF is disposed on the downstream side to raise temperature for PM regeneration, then PM removal is improved, but the device complexity increases
Solution Approach 1:
The catalyzed DPF is designed to perform multiple functions: it acts as a particulate matter filter, a temperature raising device through catalytic combustion, and an additional NOx reduction component. This multi-functionality justifies its integration into the system, as it addresses several performance requirements simultaneously rather than requiring separate dedicated components for each function.
Solution Approach 2:
The system dynamically manages the catalyzed DPF operation by controlling hydrocarbon supply timing and amount to optimize temperature generation for PM regeneration. The control strategy adapts to operating conditions, activating catalytic combustion only when sufficient PM accumulation exists and exhaust temperature is appropriate, thereby managing system complexity through intelligent dynamic control rather than continuous operation.
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
Facilitates desulfurization of both high-temperature and low-temperature NOx occlusion reduction type catalysts, improves NOx reduction efficiency, and maintains high NOx removal performance across a wide temperature window while reducing HC slip and operational costs.
Implementation Method 1
an oxidation catalyst disposed on an upstream side of the high-temperature NOx occlusion reduction type catalyst
Implementation Method 2
the nitrogen dioxide is bound to the NOx occlusion material to form a nitrate (Ba 2 NO 4 ) or the like and is occluded
Implementation Method 3
the released nitrogen dioxide is reduced to nitrogen (N 2 ) with unburned hydrocarbons (HCs), carbon monoxide, or the like contained in the exhaust gas by the three-way function of the catalytic metal
Implementation Method 4
the temperatures of the exhaust gas and the catalyzed DPF can be sufficiently raised
Data Source
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AI summary
Provided is an exhaust gas purification system including NOx occlusion reduction type catalysts, wherein a high-temperature NOx occlusion reduction type catalyst 22 in which a NOx occlusion material containing an alkali metal is supported and a low-temperature NOx occlusion reduction type catalyst 23 in which a NOx occlusion material containing an alkaline earth metal is supported are disposed in series on an upstream side and a downstream side, respectively, and an oxidation catalyst 21 is disposed on an upstream side of the high-temperature NOx occlusion reduction type catalyst 22. The compositions and arrangement of the NOx occlusion reduction type catalysts are designed with ingenuity, so that the desulfurization of the NOx occlusion reduction type catalysts is facilitated, and the NOx reduction efficiency is improved by the partial oxidation of hydrocarbons in the exhaust gas, while a wide NOx active temperature window is achieved.