Ammonia Supply Controller for SCR Catalyst NOx Purification
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Solution Overview
Problem
Existing exhaust gas purification systems for engines face challenges in efficiently purifying NOx due to excessive ammonia supply to the SCR catalyst, which can lead to ammonia discharge and reduced NOx purification performance, as the generation of ammonia varies with temperature and is not accurately accounted for in current systems.
Innovation Solution
An exhaust gas purification controller that includes an NOx catalyst, an NOx catalyst regenerator, an SCR catalyst, an ammonia supplier, and an ammonia supply amount controller, which adjusts the ammonia supply based on the amount of reducing agents detected in the exhaust gas to prevent excessive ammonia discharge and optimize NOx purification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the ammonia supply to the SCR catalyst is increased to improve NOx purification, then the NOx purification performance is improved, but ammonia discharge occurs downstream the SCR catalyst
Solution Approach 1:
The control device calculates the amount of ammonia generated by the NOx catalyst based on detected exhaust gas parameters (temperature, flow rate, air-fuel ratio) and uses this feedback information to adjust the ammonia supply amount to the SCR catalyst, preventing both excessive ammonia discharge and insufficient NOx purification
Solution Approach 2:
The system dynamically changes the ammonia supply parameter based on varying exhaust gas temperature and flow rate conditions, optimizing the balance between NOx purification efficiency and ammonia discharge prevention under different operating conditions
2Object-generated harmful factors
If the ammonia supply to the SCR catalyst is decreased to prevent ammonia discharge, then ammonia discharge is inhibited, but the NOx purification performance deteriorates
Solution Approach 1:
The control device continuously monitors exhaust gas parameters and adjusts the ammonia supply amount in real-time based on the calculated ammonia generation amount from the NOx catalyst, ensuring optimal NOx purification while preventing ammonia discharge
Solution Approach 2:
The ammonia supply amount is made dynamic rather than fixed, adjusting continuously according to changing exhaust gas temperature, flow rate, and composition to maintain optimal purification performance under varying conditions
3Device complexity
If the ammonia supply is controlled without considering NH3 generation amount, then the control system is simple, but it is impossible to sufficiently inhibit ammonia discharge or may result in shortage of NH3
Solution Approach 1:
The control device calculates the ammonia generation amount using detected exhaust gas parameters (temperature, flow rate, air-fuel ratio) and existing catalyst characteristics, without requiring additional sensors or complex external systems, achieving self-sufficient ammonia supply optimization
Solution Approach 2:
The control device performs multiple functions: it controls fuel injection for NOx catalyst regeneration, calculates ammonia generation amount, and adjusts ammonia supply to SCR catalyst, consolidating these functions in a single control system
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
The system effectively inhibits ammonia discharge and enhances NOx purification efficiency by accurately controlling ammonia supply, considering the varying generation rates and reducing agent levels, thereby maintaining optimal purification performance.
Implementation Method 1
occlude NOx in an flowing-in exhaust gas in a state wherein an air-fuel ratio of the flowing-in exhaust gas is leaner than a stoichiometric air-fuel ratio
Implementation Method 2
purify NOx by a reaction with NH3
Data Source
AI summary
An NH3 supply amount controller reduces and adjusts a supply amount of NH3 to an SCR catalyst by an NH3 supplier, when an exhaust gas flowing into an NOX catalyst has a rich air-fuel ratio and NOX occluded by the NOX catalyst is reduced to N2. A reduction amount of the supply amount of the NH3 controlled by the NH3 supply amount controller is set larger when an amount of reducing agent detected or estimated by a reducing agent amount detector is larger.