Coupled Oxidation Catalyst System for Gas Turbine Exhaust
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Solution Overview
Problem
Gas turbines face challenges in reducing emissions of carbon monoxide (CO), volatile organic compounds (VOC), and oxides of nitrogen (NOx) during start-up, as existing technologies are not effective in these conditions and can lead to excessive NO2 formation, which affects the efficiency of selective catalytic reduction (SCR) catalysts.
Innovation Solution
A coupled oxidation catalyst system with two beds, one located in a high temperature region to initiate emission reduction during start-up and another in a lower temperature region to complete CO and VOC reduction at full load, optimizing catalyst placement and formulation to minimize NO2 formation and ensure efficient NOx reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single oxidation catalyst bed is used, then the device complexity is reduced, but the emission reduction performance during start-up and full load is insufficient
Solution Approach 1:
The oxidation catalyst system is divided into two separate beds: a high-temperature oxidation catalyst bed and a low-temperature oxidation catalyst bed. Each bed operates optimally in its respective temperature range, allowing effective emission reduction during both start-up (low temperature) and full load (high temperature) conditions, whereas a single catalyst bed cannot maintain high efficiency across the entire temperature range.
2Productivity
If oxidation catalysts are used at high temperatures, then CO and VOC oxidation is improved, but NO2 formation increases which affects SCR catalyst efficiency
Solution Approach 1:
The oxidation catalyst system is divided into two separate beds: a high-temperature oxidation catalyst bed and a low-temperature oxidation catalyst bed. Each bed operates optimally in its respective temperature range, allowing effective emission reduction during both start-up (low temperature) and full load (high temperature) conditions, whereas a single catalyst bed cannot maintain high efficiency across the entire temperature range.
Solution Approach 2:
Different regions of the exhaust stream are treated with catalysts optimized for their specific temperature conditions. The high-temperature bed handles full-load conditions with optimized catalyst formulation for high temp operation, while the low-temperature bed handles start-up conditions. This local optimization prevents excessive NO2 formation in each zone while maintaining overall system effectiveness.
3Productivity
If existing catalytic technologies are used during start-up, then emission reduction is attempted, but the technologies are not effective and can lead to excessive NO2 formation
Solution Approach 1:
Different regions of the exhaust stream are treated with catalysts optimized for their specific temperature conditions. The high-temperature bed handles full-load conditions with optimized catalyst formulation for high temp operation, while the low-temperature bed handles start-up conditions. This local optimization prevents excessive NO2 formation in each zone while maintaining overall system effectiveness.
Solution Approach 2:
The system uses catalysts with different temperature optima and formulations. The low-temperature oxidation catalyst is specifically formulated to be effective at start-up temperatures, while the high-temperature oxidation catalyst is formulated for full-load conditions. This parameter differentiation allows effective emission reduction across the entire operating range without excessive NO2 formation.
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 coupled system provides superior overall performance in reducing CO and VOC emissions, reduces the likelihood of exhaust gas bypass, and is less susceptible to poisoning, while optimizing NOx reduction and minimizing NO2 formation, thus meeting regulatory requirements at reduced costs and increased reliability.
Implementation Method 1
a first oxidation catalyst in a relatively high temperature zone to allow the gas turbine to begin reducing emissions during start-up
Implementation Method 2
a second oxidation catalyst in a relatively low temperature zone to provide additional catalyst surface and complete the desired CO and VOC reduction
Data Source
Figure 1~2
Figure 3
AI summary
An exhaust system for a power generating apparatus comprising a heat source for combusting a fuel in air to produce power, which exhaust system being adapted to receive a flowing exhaust gas and comprising a catalyst system for treating the exhaust gas, which catalyst system comprising a first oxidation catalyst and a second oxidation catalyst, wherein the first oxidation catalyst is positioned downstream from the heat source so that the flowing exhaust gas contacts the first oxidation catalyst before the second oxidation catalyst.