SCR Catalyst Temperature Control via Exhaust Gas Mixing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The challenge lies in maintaining the selective catalytic reduction (SCR) catalyst within a specific temperature range to effectively convert NOx into N2 and H2O, as temperatures above a threshold can lead to NH3 release or oxidation, while temperatures below a second threshold result in reduced efficiency, and the catalyst requires NH3 to function properly.
Innovation Solution
The method involves controlling the temperature at the SCR catalyst's inlet by mixing exhaust gases from two parallel passages, one with cooling fins and the other without, using a diverter valve or venturi to adjust the gas flow, ensuring the temperature falls within a desired range (200-400°C) to optimize SCR catalyst operation and diagnostics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If exhaust gas temperature is reduced below a second threshold temperature, then SCR catalyst temperature is maintained within optimal range, but SCR conversion efficiency decreases
Solution Approach 1:
The system dynamically adjusts exhaust gas temperature parameters by controlling the mixing ratio between cooled and uncooled exhaust streams, allowing the SCR catalyst temperature to be maintained within the optimal range for conversion efficiency
2Temperature
If exhaust gas temperature is increased above a first threshold temperature, then SCR catalyst operates at higher temperature, but NH3 is released or oxidized to NOx
Solution Approach 1:
The system controls the temperature parameter of exhaust gas entering the SCR catalyst by adjusting the mixing ratio, preventing the temperature from exceeding the threshold that causes NH3 release or oxidation while maintaining effective NOx conversion
3Device complexity
If a single exhaust passage is used, then system complexity is reduced, but SCR temperature control precision is insufficient
Solution Approach 1:
The exhaust system is divided into separate passages: one for cooled exhaust gas and one for uncooled exhaust gas, allowing independent control of each stream before mixing, thereby achieving precise temperature control at the SCR catalyst inlet
Solution Approach 2:
A mixing passage serves as an intermediary component that combines cooled and uncooled exhaust streams in controlled proportions, enabling precise adjustment of the temperature parameter delivered to the SCR catalyst
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
This approach enhances SCR catalyst efficiency, reduces the risk of degradation, and improves diagnostic capabilities by maintaining the catalyst within the optimal temperature range, thereby enhancing emissions reduction and NH3 storage capacity.
Implementation Method 1
the second exhaust passage including cooling fins, the first exhaust passage not including cooling fins
Implementation Method 2
controlling a temperature at an inlet of the SCR via mixing exhaust gas flowing through a first exhaust passage and exhaust gas flowing through a second exhaust passage
Data Source
AI summary
Methods and systems to control a temperature of a selective catalytic reduction catalyst are disclosed. In one example, a diverter valve that includes two butterfly valves that are coupled together via a shaft is adjusted to control a temperature at an inlet of the selective catalytic reduction catalyst so that the selective catalytic reduction catalyst may operate efficiently.