Gas Turbine Exhaust Catalyst Layout for Low-Load Emissions Compliance
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Solution Overview
Problem
Gas turbine exhaust emissions significantly increase below 50% load, exceeding permit compliance levels, forcing plants to shut down or increase load, which hampers grid stability and operational flexibility, and degrades economics, especially with increased intermittent renewable energy demands.
Innovation Solution
The configuration of additional oxidation (CO) catalysts and high NO2 reduction or multi-pollutant SCR catalysts in the exhaust path, along with control system modifications and steam cycle management, extends the emissions compliant operational range and reduces emissions during startups and shutdowns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If gas turbine operates below 50% load, then operational flexibility and grid stability are improved, but exhaust emissions increase significantly exceeding permit compliance levels
Solution Approach 1:
The exhaust path is segmented into multiple zones with different catalyst types positioned at specific locations. Oxidation catalysts are placed upstream to handle CO and VOC, while high NO2 reduction SCR catalysts are placed downstream to specifically target NO2. This segmentation allows each catalyst zone to optimize its function for the specific emission components present at that stage, enabling compliance across a broader load range.
Solution Approach 2:
Different catalyst materials and configurations are used at different locations in the exhaust path based on local conditions. The oxidation catalyst section uses materials optimized for CO/VOC conversion, while the SCR section uses catalysts specifically tuned for NO2 reduction. This local quality approach ensures that each section of the exhaust path has the appropriate catalytic activity for the emissions profile at that operating point.
2Reliability
If traditional emissions control systems are used, then emissions are controlled at normal loads, but they cannot sufficiently destroy NOx, CO and VOC at low loads
Solution Approach 1:
The emissions control system is designed with multi-functionality to handle different emission components across varying load conditions. The combination of oxidation catalysts (for CO and VOC) and high NO2 reduction SCR catalysts (for NOx) creates a universal system that can effectively control all major emission types regardless of whether the plant is operating at high load, low load, during startup, or shutdown, thereby achieving permit compliance across the entire operational envelope.
Solution Approach 2:
The system leverages parameter changes in the exhaust gas composition and temperature profile across different operating conditions. By positioning catalysts to take advantage of the natural variations in exhaust temperature, oxygen concentration, and emission component ratios that occur during load changes, startup, and shutdown, the system maintains effective emissions control without requiring active adjustment of catalyst properties.
3Object-generated harmful factors
If gas turbine increases load or shuts down to maintain emissions compliance, then emissions compliance is achieved, but grid stability is hampered and operational flexibility is reduced
Solution Approach 1:
The oxidation catalysts are positioned upstream in the exhaust path to perform preliminary destruction of CO and VOC before the gases reach the SCR catalyst section. This preliminary action reduces the burden on the downstream SCR system and ensures that CO and VOC emissions are controlled across all operating conditions, including low load and transient operations, without requiring load changes.
4Adaptability or versatility
If additional emission control equipment is added, then emissions compliant operational range is increased, but device complexity increases
Solution Approach 1:
The patent combines oxidation catalysis and SCR catalysis into a single integrated exhaust treatment train. Rather than separate independent systems, the oxidation catalysts and high NO2 reduction SCR catalysts are positioned in sequence within the same exhaust path, sharing common support structures and control systems. This merging reduces the overall footprint and complexity compared to completely separate emission control systems while achieving broader compliance.
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 allows gas turbine power plants to operate continuously from 100% to 40% load while maintaining stack emissions compliance, significantly reducing cumulative emissions and ensuring operational flexibility and reduced plant emissions during steady-state, startups, and shutdowns.
Implementation Method 1
addition of a series of oxidation (CO) catalysts
Implementation Method 2
oxidation (CO) catalysts
Implementation Method 3
high NO2 reduction or multi-pollutant SCR catalysts
Implementation Method 4
high NO2 reduction
Data Source
AI summary
An apparatus for a gas turbine power plant that uniquely configures emission control equipment such that the plant can extend the emissions compliant operational range, the apparatus including a plurality of oxidation (CO) catalysts arranged in series.