Stoichiometric Combustion Control in Recirculating Power Plants
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Solution Overview
Problem
Existing combustion turbine systems face challenges in achieving stoichiometric point operation efficiently, which is desirable for lowering emissions and performance tuning, especially in systems with exhaust gas recirculation, as they struggle to produce working fluids with desired characteristics like high carbon dioxide and nitrogen levels for industrial applications.
Innovation Solution
The method involves a power plant system with a recirculation loop that includes an oxidant compressor, a recirculation compressor, upstream and downstream combustors, and a heat-recovery steam generator, where the oxidant and fuel are carefully controlled to achieve stoichiometric combustion, allowing for the extraction of high CO2 and N2 gases by optimizing the flow and pressure of gases through the system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If exhaust gas recirculation is implemented in combustion turbine systems, then emissions are lowered and working fluid composition is improved, but achieving stoichiometric point operation becomes difficult and system complexity increases
Solution Approach 1:
The combustion process is divided into two separate combustors: a first combustor that operates at stoichiometric point to produce high CO2 and N2 working fluid, and a second combustor that operates with excess air to complete the combustion process. This segmentation allows each combustor to be optimized for its specific function, enabling stoichiometric operation without compromising overall combustion efficiency or increasing excessive system complexity.
Solution Approach 2:
The system dynamically adjusts the split of combustion between the two combustors based on operating conditions. By changing the combustion parameters (fuel-air ratio, exhaust gas recirculation rate) in each combustor, the system maintains stoichiometric point operation in the first combustor while adapting to varying power demands and maintaining low emissions across different operating points.
2Quantity of substance
If stoichiometric point operation is achieved, then working fluid with high CO2 and N2 levels is produced for industrial applications, but combustion control becomes more difficult and reliability decreases
Solution Approach 1:
The first combustor acts as an intermediary device that receives a portion of the fuel and oxidant, operates at the precise stoichiometric point to generate working fluid with desired CO2 and N2 composition, and then combines its exhaust with the second combustor's exhaust. This intermediary approach allows independent optimization of working fluid composition without compromising the stability of the overall combustion system.
Solution Approach 2:
Instead of requiring the entire combustion system to operate at stoichiometric point (which would be unstable), only a partial portion (first combustor) operates at stoichiometric conditions, while the second combustor operates with excess air to ensure complete combustion and system stability. This partial action approach achieves the desired working fluid composition while maintaining combustion reliability.
3Productivity
If existing power plants are modified to achieve stoichiometric operation, then economic value is created through gas extraction, but modification costs and ease of manufacture decrease
Solution Approach 1:
The first combustor is designed with multi-functionality: it serves both as a combustion device and as a working fluid generation unit. By operating at stoichiometric point, it simultaneously produces power and generates high-concentration CO2 and N2 streams for industrial extraction. This universal design allows existing power plants to add gas extraction capability with minimal additional equipment, improving productivity while controlling modification costs.
Data Source
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AI summary
A method of controlling a power plant (9) that comprises a working fluid and a recirculation loop (10), wherein the power plant (9) includes a combustor operably connected to a turbine, the method including the steps of: recirculating at least a portion of the working fluid through the recirculation loop (10); controlling the power plant (9) such that the combustor at least periodically operates at a preferred stoichiometric ratio; and extracting the working fluid from at least one of a first extraction point (75) and a second extraction point (76) positioned on the recirculation loop during the periods when the combustor operates at the preferred stoichiometric ratio.