Flasher-Integrated HRSG for Low-Temperature Waste Heat Recovery
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Solution Overview
Problem
In large gas turbine combined cycle power systems, it is challenging to efficiently recover waste heat due to reduced temperatures at the exit portion of multi-pressure heat recovery steam generators (HRSGs), which affects overall system efficiency.
Innovation Solution
A multi-pressure type HRSG system is implemented with additional economizers, steam generators, and a flasher to efficiently recover waste heat by generating flash steam and utilizing it directly in the steam turbine, along with a recirculation system to manage water and prevent condensation issues, and an auxiliary steam header to support steam supply and sealing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a multi-pressure type HRSG is used to recover waste heat from large gas turbines, then waste heat recovery efficiency is improved, but the temperature at the exit portion is reduced making low-temperature heat recovery difficult
Solution Approach 1:
The patent changes the physical state parameters of water by introducing a flasher that reduces pressure, causing water to flash-evaporate and generate steam at lower temperatures. This allows effective utilization of the low-temperature waste heat that would otherwise be difficult to recover.
Solution Approach 2:
The patent utilizes phase transition of water from liquid to vapor through flash evaporation in the flasher. By reducing pressure, water rapidly evaporates and generates flash steam, converting low-temperature thermal energy into useful steam for power generation or process use.
2Loss of energy
If water is heated by the first economizer to recover waste heat, then heat recovery is improved, but condensation of exhaust gas may occur causing operational issues
Solution Approach 1:
The patent extracts a portion of the heated water from the first economizer output and directs it to the flasher before it enters the steam generator. This separation allows the extracted water to be used for flash evaporation, preventing it from causing condensation issues in the main steam generation system while still recovering its thermal energy.
Solution Approach 2:
The flasher acts as an intermediary device between the first economizer and the steam generator. It processes the extracted water through pressure reduction and flash evaporation, transforming it into flash steam and drain water that can be safely reintroduced into the system without causing condensation problems.
3Temperature
If a flasher is introduced to generate flash steam from heated water, then low-temperature heat utilization is improved, but system complexity increases
Solution Approach 1:
The flasher serves multiple functions: it generates flash steam from low-temperature heated water, produces drain water for reuse in the system, and prevents condensation issues by removing problematic water before it enters the steam generator. This multi-functionality justifies the added complexity by delivering multiple benefits from a single device.
Solution Approach 2:
The patent combines the flash evaporation process with the existing waste heat recovery system by integrating the flasher into the water flow path from the first economizer. The flash steam and drain water are reintroduced into the system, merging the flash evaporation function with the overall heat recovery process.
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 configuration enhances the power generation efficiency of the combined cycle power system by effectively utilizing low-temperature waste heat and preventing condensation-related issues, thereby improving overall system performance.
Implementation Method 1
a flasher which generates a first flash steam and a first drain water by flashing a portion of the water heated by the first economizer
Data Source
AI summary
A combined cycle power system includes a gas turbine exhausting an exhaust gas, a heat recovery steam generator including, a first economizer, a first steam generator, a second economizer, a second steam generator, a steam turbine which is driven by the steam generated at the first steam generator and the second steam generator, and a flasher which generates a first flash steam and a first drain water by flashing a portion of the water heated by the first economizer.