Finger Mixer Tempering Air System for Gas Turbine SCR
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Solution Overview
Problem
The efficiency of selective catalyst reduction systems in gas turbine engines is limited by the narrow temperature range and uneven temperature profiles of hot combustion gases, which can hinder the effective reduction of nitrogen oxides unless the gases are cooled and temperature profiles are evened out before reaching the catalyst.
Innovation Solution
A tempering air system comprising a finger mixer and mixing boxes with progressively reduced length finger ducts is used to inject cooling air into the combustion gas stream, mixing it uniformly before it reaches the catalyst, ensuring the gas stream is cooled and has a stable temperature profile for efficient nitrogen oxide reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If cooling air is injected into the combustion gas stream, then the temperature is reduced to within the efficient range for the catalyst, but the temperature profile becomes uneven
Solution Approach 1:
The cooling air injection system is divided into multiple zones along the length of the combustor, with different injection rates in different sections. This segmentation allows progressive cooling that maintains temperature uniformity while achieving the target temperature range for catalyst efficiency.
Solution Approach 2:
Different regions of the combustion gas stream receive different amounts of cooling air based on their local temperature requirements. The system adjusts cooling air distribution to match the non-uniform temperature profile of the combustion gases, ensuring each region is cooled appropriately to maintain overall uniformity.
2Reliability
If the combustion gas stream is cooled before reaching the catalyst, then the catalyst operates within its efficient temperature range, but the system complexity increases
Solution Approach 1:
The tempering air system is integrated with the existing combustor structure, combining the cooling air injection function with the combustor's natural airflow paths. This merging approach achieves catalyst temperature control without adding separate complex cooling systems.
Solution Approach 2:
The system uses a portion of the combustion air intake as the cooling air source, allowing the system to self-regulate temperature using resources already available in the combustion process. This eliminates the need for external cooling systems and reduces overall complexity.
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 tempering air system effectively cools and stabilizes the temperature profile of the combustion gas stream, enhancing the efficiency of the selective catalyst reduction process by optimizing the conditions for the catalyst to react with nitrogen oxides, thereby reducing emissions within the desired temperature range.
Implementation Method 1
mixing the combustion gas stream and the cooling air stream into a substantially uniform profile
Implementation Method 2
injecting a cooling air stream into the combustion gas stream
Implementation Method 3
reacting the mixed stream in a catalyst
Implementation Method 4
the reactant reacts with the nitrogen oxides in the combustion gas stream to form water and nitrogen
Data Source
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AI summary
The present application provides a selective catalyst reduction system (100) for use with a combustion gas stream (35) of a gas turbine (10). The selective catalyst reduction system (100) may include a tempering air system (140) with a finger mixer (150) and a number of mixing boxes (250) positioned downstream of the finger mixer (150) and a catalyst (130) positioned downstream of the tempering air system (140). The tempering air system (140) cools the combustion gas stream (35) before the combustion gas stream (35) reaches the catalyst (130).