Ejector-Based Combustion Gas Cooling for Steam Generation
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Solution Overview
Problem
Gas turbine power plants face inefficiencies due to stringent emission regulations, requiring operation at full-speed full-load conditions even during low grid demand, which reduces overall efficiency and increases unnecessary power production.
Innovation Solution
A system that cools combustion gas extracted from a turbine using compressed air and ambient air, mixing it with exhaust gas to enhance thermal energy transfer in the heat recovery steam generator, allowing for modulated steam production and reduced power output while maintaining efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the gas turbine operates at full-speed full-load conditions to meet steam demand, then steam production is sufficient, but overall power plant efficiency decreases
Solution Approach 1:
The system segments the combustion gas flow into two paths: one going through the turbine for power generation and another being extracted and cooled separately for steam generation. This allows independent optimization of steam production without forcing the entire system to operate at full load, thereby resolving the contradiction between steam supply and efficiency.
Solution Approach 2:
A cooling medium (such as water or another fluid) is introduced as an intermediary substance to extract thermal energy from the combustion gas. This intermediary enables controlled heat transfer for steam generation while allowing the main turbine flow to operate at optimal efficiency points, decoupling the two functions.
2Object-generated harmful factors
If the gas turbine operates at full-speed full-load conditions to maintain acceptable emissions levels, then emissions requirements are met, but unnecessary power production increases
Solution Approach 1:
By segmenting the combustion process and exhaust flow, the system allows the turbine to operate at lower power output while maintaining emissions control through the separate cooling and combustion gas management path, eliminating unnecessary power production during low demand periods.
Solution Approach 2:
The system dynamically adjusts the extraction ratio of combustion gas and the flow distribution between turbine and cooling paths based on real-time steam demand and emissions requirements. This dynamic control enables the plant to maintain emissions compliance while optimizing power output according to actual grid demand, reducing wasteful generation.
3Temperature
If compressed air is used to cool combustion gas, then thermal energy transfer is enhanced, but device complexity increases
Solution Approach 1:
The compressed air cooling system serves multiple functions: it cools the combustion gas for thermal energy transfer, provides a controlled cooling medium that can be regulated independently, and utilizes existing compressor infrastructure. This multi-functionality enhances thermal management while minimizing additional complexity compared to dedicated cooling systems.
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 system increases steam production capacity without proportional power increase, reduces wasteful power generation, and operates at a more cost-effective and efficient capacity by optimizing thermal energy use.
Implementation Method 1
The first ejector cools the stream of combustion gas via compressed air extracted from the compressor
Implementation Method 2
a second ejector having a primary inlet fluidly coupled to the compressor extraction port, a suction inlet in fluid communication with an air supply
Implementation Method 3
The cooled combustion gas mixes with the exhaust gas within the exhaust duct to provide a heated exhaust gas mixture
Data Source
AI summary
A power plant includes an exhaust duct downstream from an outlet of a turbine which receives exhaust gas from the turbine outlet, a first ejector having a primary inlet that is fluidly coupled to a turbine extraction port and an outlet that is in fluid communication with the exhaust duct. The power plant further includes a second ejector having a primary inlet fluidly coupled to the compressor extraction port, a suction inlet in fluid communication with an air supply and an outlet in fluid communication with a suction inlet of the first ejector. The first ejector cools the stream of combustion gas via compressed air extracted from the compressor and cooled via the second ejector. The cooled combustion gas mixes with the exhaust gas within the exhaust duct to provide a heated exhaust gas mixture downstream from the exhaust duct.