SCR Catalyst Initialization via Thermal Desorption
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Solution Overview
Problem
Existing exhaust gas purification systems for internal combustion engines face challenges in accurately initializing ammonia adsorption on SCR catalysts, leading to errors in NOx purification rates due to complex calculations and measurement inaccuracies, which hinder precise control of urea injection and NOx purification.
Innovation Solution
An exhaust gas purification apparatus and method that calculates ammonia adsorption estimates based on urea injection and temperature, heats the SCR catalyst to initialize adsorption, and determines initialization through error comparisons and operational range checks, simplifying the process and eliminating the need for complex calculations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the amount of NH3 adsorption is estimated based on sensor measurements and calculations, then the NOx purification rate can be monitored, but measurement errors and calculation errors accumulate, preventing highly accurate control of urea injection and NOx purification
Solution Approach 1:
The patent changes the state of the SCR catalyst by heating it to a high temperature (e.g., 350°C or higher) to desorb NH3 from the catalyst surface. This temperature parameter change resets the NH3 adsorption amount to zero, eliminating accumulated errors in estimation and enabling reliable re基准ing of the control system.
2Measurement precision
If the SCR catalyst is heated to initialize NH3 adsorption, then the amount of NH3 adsorption can be reset accurately, but energy is consumed and the catalyst temperature increases
Solution Approach 1:
The patent implements periodic heating of the SCR catalyst at predetermined intervals or when specific conditions are met (e.g., when NH3 adsorption amount reaches a threshold). This periodic action resets NH3 adsorption only when necessary, achieving accurate initialization while minimizing unnecessary energy consumption.
3Measurement precision
If complex calculations are performed to balance reducing agent supply and consumption, then the amount of NH3 adsorption can be initialized, but the procedure becomes troublesome and complicated
Solution Approach 1:
The patent replaces complex mechanical calculation procedures with a thermal field approach. Instead of performing complicated calculations to balance reducing agent supply and consumption, the system simply heats the catalyst to a predetermined temperature, using thermal energy to desorb NH3 and reset the adsorption amount to zero, thereby simplifying the initialization operation.
4Productivity
If the amount of NH3 adsorption is continuously monitored, then the NOx purification rate can be controlled, but errors accumulate over time, requiring frequent initialization
Solution Approach 1:
The patent uses feedback from NH3 sensors (upstream and downstream of the SCR catalyst) to monitor NH3 adsorption in real-time. When the adsorption amount reaches a predetermined threshold or when a predetermined time interval elapses, the system triggers heating to reset the adsorption amount, thereby preventing error accumulation and maintaining continuous control 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 accurate initialization of the SCR catalyst, ensuring precise NOx purification control without complex procedures, reducing errors and unnecessary heating, and maintaining operational efficiency.
Implementation Method 1
selective catalytic reduction (SCR), a technique for selectively purifying nitrogen oxide (NOx) in exhaust gas using ammonia as a reducing agent
Implementation Method 2
The injected urea is degraded to ammonia (NH3) to be adsorbed on the SCR catalyst
Implementation Method 3
heating the SCR catalyst in order to initialize the amount of NH3 adsorption of the SCR catalyst
Data Source
AI summary
In embodiments, an exhaust gas purification apparatus and method for an internal combustion engine initializes a SCR catalyst by heating the SCR catalyst under predetermined conditions without accompanying troublesome procedures and complicated calculations. With the exhaust gas purification apparatus for an internal combustion engine, arranged on an exhaust-gas passage of the internal combustion engine and including the SCR catalyst for purifying NOx in exhaust gas in the internal combustion engine, the method calculates and accumulates estimated values of NH3 adsorption adsorbed on the SCR catalyst, on the basis of the amount of NH3 injection from urea-aqueous solution injected into the exhaust-gas passage from the upstream side of the SCR catalyst and the amount of NH3 injection for purifying NOx at the upstream side of the SCR catalyst, and initializing the SCR catalyst by heating the SCR catalyst to initialize the estimated value of NH3 adsorption.