A-Shaped Catalyst Bed for Gas Turbine Exhaust Emission Control
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Solution Overview
Problem
The placement of a catalyst bed in the exhaust stream of a gas turbine, where both turbine exhaust gases and cooling air pass through it, results in excessive pressure drop and reduced catalyst effectiveness due to temperature decrease, compromising its performance and causing pressure rise in the enclosure.
Innovation Solution
Placing the catalyst bed immediately downstream of the gas turbine exhaust, where primary exhaust air passes through it before mixing with cooling air, and forming the catalyst bed in an A-shaped structure to increase surface area and reduce gas velocity, thereby maintaining low enclosure pressure and optimizing catalyst effectiveness while reducing exhaust gas temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If the catalyst bed is placed across the enclosure where both turbine exhaust gases and cooling air pass through it, then emission reduction is achieved, but the pressure drop through the catalyst causes excessive pressure rise in the enclosure and reduces the temperature at the catalyst, rendering it less effective
Solution Approach 1:
The exhaust stream is segmented into two separate paths: one for hot exhaust gases flowing through the catalyst bed, and another for cooling air that bypasses the catalyst. This segmentation prevents cooling air from reducing catalyst temperature and eliminates the excessive pressure drop caused by cooling air passing through the catalyst bed.
Solution Approach 2:
The catalyst bed is positioned specifically in the hot exhaust gas stream where high temperature conditions prevail, ensuring optimal catalyst effectiveness. The cooling air is directed through a separate path that does not interfere with the catalyst's thermal environment, creating locally optimized conditions for both cooling and catalysis functions.
2Temperature
If cooling air is mixed with gas turbine exhaust gases to reduce temperatures, then exhaust temperature is reduced for silencer and stack protection, but the catalyst effectiveness is reduced due to lower temperature at the catalyst
Solution Approach 1:
The system segments the thermal management functions: the catalyst bed handles emission reduction in the hot exhaust stream, while a separate cooling air path provides temperature reduction downstream. This eliminates the trade-off by performing catalysis at high temperature and cooling afterward.
Solution Approach 2:
The catalyst bed is positioned upstream in the exhaust stream before the cooling air mixing point. This preliminary action ensures that emission reduction occurs while exhaust gases are still hot, and cooling is applied subsequently, preserving catalyst effectiveness while achieving temperature reduction.
3Object-generated harmful factors
If the catalyst bed is placed across the enclosure with both exhaust gases and cooling air passing through it, then emission reduction occurs, but the velocity of exhaust gases through the catalyst is too high, reducing contact time and effectiveness
Solution Approach 1:
By segmenting the exhaust stream to exclude cooling air from passing through the catalyst bed, the velocity of gases through the catalyst is reduced to optimal levels, increasing contact time and catalytic effectiveness while maintaining emission reduction functionality.
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 configuration maintains low enclosure pressure, optimizes catalyst effectiveness, and reduces exhaust gas temperatures before they enter the stack, extending the life of silencers and exhaust stacks by ensuring efficient emission reduction without losing temperature benefits.
Implementation Method 1
a catalyst bed which is placed in the exhaust stream of a gas turbine... to reduce the harmful emissions
Implementation Method 2
the catalyst bed is formed in an A-shaped structure so as to thereby increase the surface area of the catalyst bed and reduce the velocity of the exhaust gases therethrough
Implementation Method 3
provide a flow of cooling air within the enclosure around a gas turbine and to mix the cooling air with the gas turbine exhaust gases so that the temperatures are reduced
Data Source
AI summary
In a gas turbine installation having an enclosure for passing cooling air therethrough and around the gas turbine, provision is made for a mixing of the cooling air with the exhaust gases being emitted from the gas turbine to thereby reduce the temperature thereof prior to its passing into the exhaust stack, but only after the primary air has passed through a catalyst bed which is disposed in a position over the gas turbine exhaust opening. The shape of the catalyst bed is preferably A-shaped in cross-section to thereby increase the surface area thereof. In this way, the temperature at the catalyst bed is maintained at an elevated level to obtain superior performance while a subsequent mixing of the primary air with the cooling air results in lower temperatures of the gases passing through the exhaust stack.