Exhaust Purification Apparatus NH3 Generation for Regeneration
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Solution Overview
Problem
During filter regeneration in exhaust gas purification systems for internal combustion engines, the NOx removal or reduction rate decreases due to difficulties in maintaining high oxygen concentration and temperature, which hampers the operation of NOx storage and reduction catalysts.
Innovation Solution
An exhaust gas purification apparatus is designed with an NOx selective reduction catalyst, an NH3 generation catalyst, a regeneration unit, and a generation unit that generates NH3 before filter regeneration, ensuring a sufficient supply of NH3 to the NOx selective reduction catalyst, thereby maintaining NOx reduction efficiency during filter regeneration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If filter regeneration is performed by supplying oxygen and raising temperature, then PM removal efficiency is improved, but NOx removal rate decreases due to hindered catalyst operation
Solution Approach 1:
The system performs preliminary action by generating and storing NH3 in the SCR catalyst before filter regeneration begins. The generation unit creates NH3 from exhaust gases, and the storage unit retains it in the SCR catalyst's pores, ensuring NH3 is available when needed during regeneration without requiring continuous NH3 generation during the high-temperature regeneration process
Solution Approach 2:
NH3 acts as an intermediary substance that mediates between the filter regeneration process and NOx removal function. The SCR catalyst stores NH3 as an intermediary carrier, which then reacts with NOx during regeneration, allowing the system to maintain both PM removal (through regeneration) and NOx removal functions simultaneously
2Productivity
If high oxygen concentration and temperature are maintained during regeneration, then filter regeneration is enhanced, but NH3 generation is inhibited
Solution Approach 1:
The system performs NH3 generation in advance before regeneration begins, when exhaust gas conditions (lower temperature, appropriate oxygen concentration) are still favorable for NH3 production. The generation unit operates during this preliminary phase to fill the SCR catalyst with NH3, after which the regeneration unit can proceed with high-temperature oxygen-supplied regeneration without NH3 generation constraints
Solution Approach 2:
The system dynamically adjusts operational modes: first operating in NH3 generation mode with appropriate exhaust conditions, then switching to regeneration mode with high temperature and oxygen supply. This dynamic transition allows the system to optimize for NH3 generation when conditions permit, then optimize for regeneration when temperature and oxygen levels are elevated
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 effectively suppresses the decrease in NOx removal or reduction rate during filter regeneration by ensuring a consistent supply of NH3, maintaining catalyst efficiency and preventing NH3 shortages, thus optimizing both filter regeneration and NOx reduction processes.
Implementation Method 1
an NH3 generation catalyst that is arranged in the exhaust passage at the upstream side of the NOx selective reduction catalyst and generates NH3 when the air fuel ratio of the exhaust gas is equal to or less than a stoichiometric air fuel ratio
Implementation Method 2
an NOx selective reduction catalyst that is arranged in an exhaust passage of the internal combustion engine and reduces NOx by using NH3 as a reducing agent
Implementation Method 3
a regeneration unit that regenerates the filter by supplying oxygen to the filter while raising the temperature of the filter
Implementation Method 4
a regeneration unit that regenerates the filter by supplying oxygen to the filter while raising the temperature of the filter
Data Source
AI summary
A decrease in an NOx removal or reduction rate at the time of filter regeneration is suppressed. To this end, provision is made for an NOx selective reduction catalyst, a filter arranged at the upstream side of the NOx selective reduction catalyst, an NH3 generation catalyst arranged at the upstream side of the NOx selective reduction catalyst to generate NH3 when the air fuel ratio of an exhaust gas is equal to or less than a stoichiometric air fuel ratio, a regeneration unit to carry out regeneration of the filter, and a generation unit to make the air fuel ratio of the exhaust gas equal to or less than the stoichiometric air fuel ratio, thereby causing NH3 to be generated in the NH3 generation catalyst, wherein the regeneration unit inhibits the regeneration of the filter until the generation of NH3 by the generation unit is completed.