CO Oxidation Catalyst Placement Limits NO2 in Gas Turbines
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Solution Overview
Problem
Current methods for reducing NO2 emissions in combustion systems, such as gas turbines, are inadequate due to high NO2 formation at specific temperatures, leading to increased ammonia consumption and catalyst size requirements, which conflicts with stringent emission control standards and fuel efficiency goals.
Innovation Solution
The strategic placement of a carbon monoxide (CO) oxidation catalyst in the exhaust path at temperatures between 750°F to 1400°F, combined with downstream ammonia injection and selective catalytic reduction (SCR) elements, effectively limits NO2 production and reduces ammonia consumption, optimizing NOx reduction without increasing SCR catalyst size or pressure drop.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If CO oxidation catalyst is placed at lower temperatures to oxidize CO effectively, then CO conversion is improved, but NO2 production increases significantly
Solution Approach 1:
The patent changes the temperature parameter at which the CO oxidation catalyst operates, specifically placing it at higher temperatures (above 750°F) where CO oxidation remains effective but NO2 production is significantly reduced. This parameter change resolves the contradiction by finding an optimal temperature window that satisfies both CO conversion and NO2 emission control requirements.
2Object-generated harmful factors
If SCR catalyst size is increased to reduce NO2 emissions, then emission control is improved, but device complexity and cost increase
Solution Approach 1:
The patent applies preliminary action by placing the CO oxidation catalyst upstream of the SCR catalyst to pre-process the exhaust gas and limit NO2 formation before the gas reaches the SCR catalyst. This preliminary treatment reduces the burden on the SCR catalyst, allowing for a smaller, less complex SCR system while still achieving effective NO2 emission control.
3Object-generated harmful factors
If ammonia injection is increased to reduce NOx, then NOx reduction is improved, but ammonia consumption and cost increase
Solution Approach 1:
The CO oxidation catalyst performs preliminary action by oxidizing CO and limiting NO2 formation upstream of the ammonia injection point. By reducing the amount of NO2 that reaches the SCR catalyst, the preliminary action decreases the ammonia required for subsequent NOx reduction, thereby reducing ammonia consumption and associated costs.
4Quantity of substance
If CO catalyst is placed upstream to maximize CO oxidation, then CO conversion is improved, but NO2 formation increases requiring larger SCR system
Solution Approach 1:
The patent resolves this contradiction by changing the temperature parameter at which CO oxidation occurs. Instead of placing the CO catalyst in cooler regions where CO oxidation is more complete, the patent positions it in hotter exhaust streams (above 750°F) where CO oxidation is still effective but the equilibrium shifts to reduce NO2 production, thus avoiding the need for a larger SCR system.
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 significantly reduces NO2 emissions, decreases ammonia usage, and minimizes SCR catalyst surface area, resulting in lower costs and increased power output from gas turbines while avoiding the formation of a 'yellow plume' associated with high NO2 concentrations.
Implementation Method 1
a carbon monoxide (CO) oxidation catalyst disposed at a location in the gas turbine exhaust path adapted for limiting NO2 production from NO by the CO oxidation catalyst
Implementation Method 2
CO oxidation catalyst... oxidizes carbon monoxide to carbon dioxide
Implementation Method 3
selective catalytic reduction (SCR) element disposed downsteam of the ammonia injection apparatus adapted for reduction of NOx
Implementation Method 4
selective catalytic reduction... reduction of NOx in the flow of exhaust gases
Implementation Method 5
The ammonia is not a natural part of the combustion exhaust stream, but rather, it is injected into the exhaust stream upstream of the catalyst element for the specific purpose of supporting one or more of the following reduction reactions
Data Source
AI summary
A power generating apparatus including a gas turbine engine combusting a fuel in air to produce shaft power and producing a flow of exhaust gases including oxides of nitrogen (NOx), carbon monoxide (CO) and hydrocarbons (HC). An emissions treatment apparatus includes in the exhaust gas flowpath a CO oxidation catalyst disposed at a location with an exhaust gas temperature for which the CO oxidation catalyst advantageously limits NO2 production. The emissions treatment apparatus further includes an ammonia injection apparatus, a mixing section, and a selective catalytic reduction element disposed downsteam of the ammonia injection apparatus and adapted for reduction of NOx.