Flash System for HRSG Feed Water Steaming Mitigation
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Solution Overview
Problem
Combined cycle power plants with integrated gasification combined cycle (IGCC) systems face inefficiencies due to oversized high-pressure economizers during non-integrated operations, leading to undesirable steaming of feed water and reduced steam production, as they are sized for integrated processes with larger feed water volumes.
Innovation Solution
Incorporating a flash system that extracts excess feed water from the high-pressure economizer and directs it to a flash vessel, generating additional steam to supplement other sections of the heat recovery steam generator (HRSG), with a controller adjusting fluid flow ratios based on evaporator fluid levels to mitigate steaming and optimize steam production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the high-pressure economizer is sized for integrated gasification operations, then it can handle large feed water volumes during integrated processes, but it causes undesirable steaming of feed water and reduced steam production during non-integrated operations
Solution Approach 1:
The system dynamically adjusts feed water flow distribution between the high-pressure evaporator and flash system based on operational mode. During non-integrated operations, the controller redirects excess feed water to the flash system, preventing steaming in the economizer. During integrated operations, full feed water flow is directed to the high-pressure evaporator, maximizing steam production capability.
Solution Approach 2:
The feed water flow is segmented into two separate paths: one through the high-pressure evaporator and another through the flash system. This segmentation allows independent control of each path, enabling the system to optimize steam generation while preventing harmful steaming in the economizer during part-load operations.
2Productivity
If excess feed water is extracted and directed to the flash system, then additional steam is generated to supplement HRSG sections, but system complexity increases
Solution Approach 1:
The flash system serves multiple functions: it generates additional steam to supplement HRSG sections, prevents steaming in the high-pressure economizer, and provides operational flexibility during both integrated and non-integrated modes. This multi-functionality justifies the added complexity by delivering multiple benefits from a single system addition.
Solution Approach 2:
The controller monitors operational conditions and dynamically adjusts the feed water distribution ratio between the high-pressure evaporator and flash system. This feedback control ensures optimal steam production while preventing harmful steaming, automatically adapting to changing operational demands without requiring manual intervention.
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 enhances the efficiency of the combined cycle system by utilizing excess feed water to generate additional steam, improving steam production and reducing steaming issues during non-integrated operations, thereby optimizing energy conversion and system performance.
Implementation Method 1
a flash system including a first flash vessel that may receive a second portion of the feed water from the first pressure economizer and to generate a first flash steam flow
Implementation Method 2
Exhaust from the gas turbine engine may be supplied to a heat recovery steam generator ('HRSG') so as to generate steam for a steam turbine
Data Source
AI summary
A system includes a heat recovery steam generator (HRSG) including a first pressure economizer, a first pressure evaporator that may receive a first portion of a feed water from the first pressure economizer at a first pressure, a re-heat section that may receive the first portion of the feed water from the first pressure economizer as a first steam flow, and a flash system including a first flash vessel that may receive a second portion of the feed water from the first pressure economizer and to generate a first flash steam flow. The system may combine the first flash steam flow with the first steam flow of the feed water at a second pressure less than the first pressure.