Catalyst Heating System for Combined Cycle Emissions Control
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Solution Overview
Problem
The efficiency of selective catalyst reduction and oxidation systems in gas turbine engines is compromised by the narrow temperature range, leading to excessive emissions during startup and shutdown, as the catalysts are not within the optimal temperature for effective operation.
Innovation Solution
A catalyst heating system that extracts compressed air from a first gas turbine engine and directs it to the selective catalyst reduction and/or oxidation system of a second heat recovery steam generator, warming the catalyst and ammonia injection grid to maintain optimal temperature and reduce emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the catalyst system operates without external heating during startup and shutdown, then the system structure remains simple, but the catalyst temperature falls outside the efficient range leading to excessive emissions
Solution Approach 1:
Compressed air from the gas turbine compressor serves as an intermediary heating medium. The compressed air, which is already at elevated temperature due to compression, is diverted through a heater assembly to warm the catalyst substrate and ammonia injection grid, enabling the catalyst to reach its efficient operating temperature range without direct fuel combustion or external heating sources.
Solution Approach 2:
The system changes the temperature parameter of the catalyst by introducing compressed air through a controllable valve and heater assembly. By regulating the flow rate and heating the compressed air, the catalyst temperature is adjusted to maintain it within the efficient operating range during transient conditions such as startup and shutdown.
2Temperature
If compressed air extraction is used to heat the catalyst, then the catalyst temperature is maintained within the efficient range, but the gas turbine engine experiences reduced mass flow and potential efficiency impact
Solution Approach 1:
Only a portion of the compressed air from the gas turbine compressor is extracted for catalyst heating purposes. The control valve regulates the extraction flow rate to provide sufficient heat for catalyst warming while maintaining adequate mass flow through the gas turbine engine to preserve overall system efficiency and power output.
3Adaptability or versatility
If the catalyst system is designed for broad temperature operation, then it can handle various operating conditions, but the temperature range becomes too wide reducing efficiency during transient operations
Solution Approach 1:
The control valve is regulated to maintain the catalyst temperature within the efficient operating range by adjusting the compressed air flow rate in response to changing operating conditions. This feedback control ensures the catalyst remains at optimal temperature during transient operations such as startup and shutdown, maximizing emissions reduction efficiency.
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 reduces nitrous oxide and carbon monoxide emissions during startup and shutdown by maintaining the catalyst within the efficient temperature range, lowering overall emissions and enabling lower gas turbine turndown levels.
Implementation Method 1
the reactant reacts with the nitrous oxide in the combustion gas stream to form water and nitrogen
Implementation Method 2
the oxidation catalyst system promotes the reaction of carbon monoxide in the combustion stream to form carbon
Implementation Method 3
the selective catalyst reduction system adds a reductant, typically ammonia or urea, to the hot combustion gas stream
Implementation Method 4
The catalyst heating system directs an extraction from a first gas turbine engine to the selective catalyst reduction and/or oxidation catalyst system of a second heat recovery steam generator
Data Source
AI summary
The present application provides a combined cycle system. The combined cycle system may include a number of gas turbine engines, a number of heat recovery steam generators with a selective catalyst reduction and/or oxidation catalyst system, and a catalyst heating system. The catalyst heating system directs an extraction from a first gas turbine engine of the number of gas turbine engines to the selective catalyst reduction and/or oxidation catalyst system of a second heat recovery steam generator of the number of heat recovery steam generators.