Ammonia Storage on SCR Catalyst for NOx Reduction
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Solution Overview
Problem
In Selective Catalytic Reduction (SCR) systems, excess ammonia introduced into the exhaust system is not efficiently utilized once the SCR catalyst reaches its maximum ammonia storage capacity, leading to ammonia slip, where excess ammonia passes through the catalyst and into the atmosphere without contributing to NOx conversion.
Innovation Solution
A system and method that correlate the efficiency of NOx conversion to N2 and H2O using ammonia with the quantity of ammonia stored on the SCR catalyst, controlling ammonia introduction to build storage capacity while avoiding slip, using a processor-based ammonia dosing controller and algorithms to estimate ammonia consumption and storage, ensuring optimal NOx reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If excess ammonia is introduced into the exhaust system to ensure sufficient ammonia presence on SCR catalyst surfaces, then the catalytic conversion of NOx is improved, but ammonia slip increases and environmental harm worsens
Solution Approach 1:
The system continuously monitors ammonia storage capacity on the SCR catalyst and adjusts ammonia dosing accordingly. When the catalyst approaches maximum storage capacity, the controller reduces or stops ammonia introduction, preventing excess ammonia from slipping into the atmosphere while maintaining sufficient ammonia for NOx conversion.
Solution Approach 2:
The system dynamically changes the ammonia dosing rate based on real-time measurements of ammonia storage capacity. By adjusting the introduction rate of ammonia according to the current storage level, the system optimizes NOx conversion while avoiding excessive ammonia slip.
2Productivity
If ammonia is continuously introduced to maintain catalytic conversion, then NOx reduction is improved, but ammonia storage capacity is exceeded leading to waste
Solution Approach 1:
The controller receives feedback from sensors measuring ammonia storage capacity and adjusts ammonia dosing to match the catalyst's actual storage capacity, preventing waste of excess ammonia while maintaining effective NOx reduction.
Solution Approach 2:
The system introduces ammonia at rates that may initially exceed storage capacity to ensure sufficient coverage, but then adjusts to partial action levels once capacity is reached, avoiding continuous excessive introduction and associated waste.
3Productivity
If ammonia storage capacity is increased to improve conversion efficiency, then NOx conversion is improved, but system complexity increases due to monitoring and control requirements
Solution Approach 1:
The system uses feedback from ammonia sensors and stored data about catalyst storage capacity to automatically adjust dosing, reducing the need for complex manual control systems while maintaining high conversion efficiency.
Solution Approach 2:
The SCR system self-regulates ammonia dosing based on its own storage capacity measurements, reducing the need for external complex control mechanisms and enabling autonomous optimization of conversion efficiency.
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 allows for efficient NOx conversion by ensuring the SCR catalyst operates at maximum ammonia storage capacity without ammonia slip, maintaining high conversion efficiency and reducing excess ammonia emissions.
Implementation Method 1
ammonia is stored on surfaces of an SCR catalyst
Implementation Method 2
chemical reactions which reduce NOx take place on surfaces of which ammonia is stored
Data Source
AI summary
A system and method for calculating quantity of ammonia stored on an SCR catalyst at various times during an interval of time by processing certain data, including the aggregate quantity of ammonia introduced into an exhaust flow during the interval of time, calculating the efficiency of catalytic conversion of NOx to N2 and H2O by ammonia at each of the various times by processing certain data, including NOx measurements obtained from upstream and downstream NOx sensors, and establishing a correlation between efficiency of catalytic conversion of NOx to N2 and H2O by ammonia and quantity of ammonia stored on the SCR catalyst over the interval of time which comprises calculated efficiency of catalytic conversion of NOx and calculated quantity of ammonia stored on the SCR catalyst at each of the various times.