Turbine Extraction Ejector Cooling for Steam Production
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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 when grid demand is low, leading to reduced overall efficiency and increased emissions of NOx and CO.
Innovation Solution
A system that extracts combustion gas from a gas turbine and cools it using an ejector before mixing it with exhaust gas, increasing thermal energy for enhanced steam production in a heat exchanger, allowing for modulated steam production and reduced power output while maintaining efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If the gas turbine operates at full-speed full-load conditions to meet steam demand and maintain acceptable emissions levels, then emissions of NOx and CO are controlled, but overall power plant efficiency is reduced
Solution Approach 1:
The turbine exhaust stream is segmented into two separate paths: one path directs a portion of the exhaust to the HRSG for steam generation, while the other path directs the remaining exhaust directly to the atmosphere or stack. This segmentation allows the system to generate required steam without forcing the gas turbine to operate at full load, thereby maintaining efficiency while controlling emissions
Solution Approach 2:
The system dynamically adjusts the split ratio between the two exhaust paths based on steam demand and power plant operating conditions. By making the exhaust distribution dynamic rather than fixed, the system can optimize the balance between steam production and power generation efficiency while maintaining emissions control
2Object-generated harmful factors
If the gas turbine load is coupled to steam production requirements to meet emissions restrictions, then emissions levels are maintained, but power plant efficiency is reduced when grid demand is low
Solution Approach 1:
The exhaust system is divided into separate pathways that can be independently controlled, allowing steam production to be decoupled from gas turbine load. This enables the gas turbine to operate at optimal efficiency points for power generation while steam demand is met through controlled allocation of exhaust energy
Solution Approach 2:
The system changes the operational parameters by allowing independent control of steam production from power generation. By separating these previously coupled parameters, the system can optimize each function independently - maintaining emissions control through adequate steam production while maximizing power plant efficiency through optimal turbine operating points
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 without proportional power generation, optimizing fuel use and reducing wasteful power production, enabling cost-effective and efficient operation by maintaining thermal and operating efficiencies.
Implementation Method 1
The cooled combustion gas mixes with the exhaust gas within the exhaust duct
Implementation Method 2
Thermal energy from the exhaust gas is transferred to water flowing through one or more heat exchangers of the HRSG, thereby producing superheated steam
Implementation Method 3
The combustion gas is routed along a hot gas path from the combustor through the turbine where they progressively expand as they flow across alternating stages of stationary vanes and rotatable turbine blades which are coupled to a rotor shaft. Kinetic energy is transferred from the combustion gas to the turbine blades thus causing the rotor shaft to rotate.
Implementation Method 4
The rotational energy of the rotor shaft may be converted to electrical energy via a generator.
Data Source
AI summary
A power plant includes a turbine disposed downstream from a combustor. The turbine includes an extraction port that is in fluid communication with a hot gas path of the turbine and which provides a flow path for a stream of combustion gas to flow out of the turbine. An exhaust duct is disposed downstream from the turbine and receives exhaust gas from the turbine. An ejector coupled to the extraction port and to an air supply cools the stream of combustion gas upstream from the exhaust duct. The cooled combustion gas flows into the exhaust duct at a higher temperature than the exhaust gas. The cooled combustion gas mixes with the exhaust gas within the exhaust duct to provide a heated exhaust gas mixture to a heat exchanger disposed downstream from the exhaust duct. The heat exchanger may extract thermal energy from the exhaust gas mixture to produce steam.