Oxidation Catalyst Regeneration in Steam Generator Exhaust
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Solution Overview
Problem
Current emissions control systems, such as SCR and FGD, face limitations in reducing NOx emissions, especially during transient phases and at lower flue gas temperatures, and are prone to fouling by sulfur contaminants, which affects the efficiency of NOx reduction and catalyst regeneration.
Innovation Solution
A heat recovery steam generator (HRSG) system with a heating device and an oxidation catalyst is used to heat exhaust gases from a gas turbine engine, allowing NOx reduction at lower temperatures and simultaneous catalyst regeneration by adjusting the temperature to optimal ranges for effective NOx conversion and catalyst maintenance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If selective catalytic reduction (SCR) is used to reduce NOx emissions, then NOx reduction capability is improved, but the system requires high flue gas temperatures to achieve sufficient reaction rate, limiting effectiveness during transient phases and startup operations
Solution Approach 1:
The patent applies parameter changes by modifying the temperature parameter of the flue gas to optimize catalyst performance. During transient phases and startup operations, the system increases the flue gas temperature parameter to above 200°C to ensure sufficient reaction rate for NOx reduction, while during steady-state operation it maintains temperature between 100-200°C to balance NOx reduction with catalyst regeneration and prevent sulfur dioxide formation
Solution Approach 2:
The patent implements dynamics by making the flue gas temperature adjustable and adaptive to different operating conditions. The system dynamically adjusts temperature based on whether the operation is transient/startup or steady-state, allowing the SCR system to effectively operate across varying temperature conditions rather than requiring constant high temperature
2Productivity
If oxidation catalyst is used to convert NO to NO2 for enhanced solubility, then NOx conversion efficiency is improved, but the catalyst fouls over time due to sulfur dioxides, reducing oxidation yield
Solution Approach 1:
The patent applies periodic action by implementing periodic temperature cycles to regenerate the oxidation catalyst. During steady-state operation, the system periodically increases temperature to 200-400°C to burn off sulfur dioxide and other contaminants from the catalyst surface, then returns to normal operating temperature. This periodic regeneration maintains catalyst activity and prevents permanent fouling
Solution Approach 2:
The patent uses parameter changes by adjusting temperature parameter to distinguish between normal operation and regeneration modes. During normal operation, temperature is maintained at 100-200°C for optimal NO oxidation. During regeneration, temperature is increased to 200-400°C to remove contaminants, then gradually reduced to avoid thermal shock and catalyst damage
3Productivity
If flue gas temperature is increased to improve NOx reduction reaction rate, then SCR effectiveness is improved, but energy consumption increases and sulfur dioxide formation is promoted
Solution Approach 1:
The patent applies parameter changes by optimizing temperature to different operational modes: during transient phases and startup, temperature is increased above 200°C to ensure sufficient reaction rate; during steady-state operation, temperature is maintained between 100-200°C to balance NOx reduction with energy efficiency and prevent sulfur dioxide formation
Solution Approach 2:
The system dynamically adjusts temperature based on operational conditions, increasing temperature only when needed for sufficient reaction rate (transient phases) and maintaining lower temperature during steady-state operation to minimize energy consumption and avoid promoting sulfur dioxide 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
This approach enhances NOx reduction efficiency, particularly during startup and transient operations, and extends catalyst lifespan by regenerating the oxidation catalyst within a desired time frame, ensuring compliance with stringent emission standards.
Implementation Method 1
a heating device configured to heat the exhaust gases that include oxides of nitrogen (NOx)
Implementation Method 2
an oxidation catalyst coupled downstream from the heating device. The oxidation catalyst facilitates reducing an amount of NOx in the exhaust gases
Implementation Method 3
an oxidation catalyst coupled downstream from the heating device. The oxidation catalyst facilitates reducing an amount of NOx
Implementation Method 4
at a second temperature that is approximately equal to at least the thermal regeneration temperature for a catalytic material such that the catalytic material is simultaneously regenerated
Data Source
AI summary
A steam generator coupled in flow communication downstream from a combustion device that produces a flow of exhaust gases includes a heating device configured to heat the exhaust gases that include oxides of nitrogen (NOx), and an oxidation catalyst coupled downstream from the heating device. The oxidation catalyst facilitates reducing an amount of NOx in the exhaust gases channeled into the oxidation catalyst at a first temperature that is less than a thermal regeneration temperature for a catalytic material and at a second temperature that is approximately equal to at least the thermal regeneration temperature such that the catalytic material is simultaneously regenerated.