Underflow SCR Ammonia Slip Detection via Steady-State Perturbation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing exhaust systems with selective catalytic reduction (SCR) units face challenges in maintaining optimal NOx reduction efficiency due to issues with ammonia slip and storage, where either insufficient or excessive ammonia can lead to decreased conversion efficiency and increased emissions.
Innovation Solution
The system incorporates an underflow selective catalytic reduction (UFSCR) device and NOx sensors to detect steady-state conditions, perturb reductant injection, and calculate gradients to identify reductant slip or poor efficiency, allowing for adaptive reductant dosing adjustments to maintain optimal ammonia storage and reduce emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If excess ammonia is supplied to the SCR device, then NOx reduction efficiency is improved, but ammonia slip increases
Solution Approach 1:
The system employs NOx sensors positioned upstream and downstream of the SCR device to continuously monitor NOx levels. The controller compares these measurements and adjusts the reductant injection rate dynamically to maintain optimal ammonia storage, preventing both ammonia slip and breakthrough conditions through closed-loop feedback control
Solution Approach 2:
The reductant injection rate is made dynamic rather than fixed, allowing the system to adapt to changing operating conditions. The controller modulates the injection rate based on real-time NOx measurements and calculated ammonia storage levels, enabling the system to respond to transient conditions while maintaining optimal performance
2Object-generated harmful factors
If insufficient ammonia is supplied to the SCR device, then ammonia slip is reduced, but NOx conversion efficiency decreases
Solution Approach 1:
The controller uses feedback from downstream NOx sensor measurements to detect ammonia slip conditions and increases reductant injection accordingly, ensuring that insufficient ammonia supply is corrected while maintaining control over slip conditions
Solution Approach 2:
The system performs preliminary detection of steady-state conditions and proactively perturbs the reductant injection to assess system response before actual slip or breakthrough occurs, allowing preventive adjustment of ammonia storage levels
3Productivity
If reductant injection is increased to maintain ammonia storage, then NOx conversion efficiency is improved, but reductant consumption increases
Solution Approach 1:
The system uses the natural exhaust flow and thermal energy from the engine to drive the SCR process, requiring only minimal reductant injection. The controller optimizes injection timing and amount to leverage existing exhaust conditions, reducing reductant consumption while maintaining efficiency
Solution Approach 2:
The controller adjusts multiple parameters including injection timing, injection rate, and pulse duration to optimize reductant utilization. By changing these parameters dynamically, the system achieves high NOx conversion efficiency with minimized reductant consumption
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 NOx conversion efficiency by accurately managing ammonia levels, preventing slip and breakthrough, and maintaining efficient emissions control, thereby reducing harmful emissions and extending reductant storage capacity.
Implementation Method 1
An SCR device includes a substrate having an SCR catalyst disposed thereon to reduce the amount of NOx in the exhaust gas
Implementation Method 2
the NH3 reacts with the NOx in the presence of the SCR catalyst to reduce the NOx emissions
Implementation Method 3
a first NOx sensor operably connected to and in fluid communication with the exhaust gas downstream of the SCR device
Data Source
AI summary
A method for treating exhaust gas from an internal combustion engine including, determining if a steady state condition exist and perturbing a reductant injection corresponding the steady state. Measuring a first and a second NOx values corresponding to the steady state and resulting from the perturbation, and computing a gradient of the NOx values relative to the steady state respectively. The method also includes comparing the gradient of the second NOx value with one of the first NOx value, if the gradient of the first NOx value is within a selected range of the gradient of the second NOx value, identifying poor efficiency operation for the engine and setting an estimated reductant storage at zero. Otherwise if the gradient of the second NOx value exceeds a selected threshold, identifying a reductant slip condition and setting the estimated storage at maximum, if not, making no corrections in estimated storage.