HRSG Exhaust Flow Path Segmentation for Temperature Control

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Solution Overview

Problem

Heat recovery steam generator (HRSG) systems face inefficiencies in controlling fluid temperatures, leading to reduced plant electrical output and efficiency due to the need for attemperation methods that switch between heating and cooling, resulting in thermal efficiency loss.

Innovation Solution

The implementation of a HRSG system with multiple exhaust flow paths and a control system that determines which paths to use based on temperature indications, allowing exhaust to bypass heat exchangers to maintain optimal fluid temperatures without the need for attemperation, using dampers to control the flow of exhaust through these paths.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If attemperation is used to control fluid temperature by spraying cool fluid into heat exchangers, then fluid temperature can be controlled to predetermined levels, but thermal efficiency of the HRSG system is lost due to switching from heating to cooling and then heating again

Engineering Contradiction:

Improvefluid temperatureVSAvoidthermal efficiency

Core Design Contradiction:

TemperatureVSLoss of energy

Solution Approach 1:

The exhaust flow path is segmented into multiple separate paths, allowing independent control of exhaust flow through different heat exchangers. This enables selective routing of exhaust to maintain optimal temperatures without requiring attemperation, thereby preserving thermal efficiency while achieving precise temperature control.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Instead of cooling the fluid when it becomes too hot (attemperation), the invention inverts the approach by routing exhaust through alternative paths that prevent overheating in the first place. This eliminates the need for cooling and subsequent re-heating, maintaining continuous heating mode and preserving thermal efficiency.

Inventive Principle:

Principle #13The other way round (Inversion)

2Temperature

If attemperation is used to control fluid temperature, then temperature control is achieved, but plant electrical output and efficiency are reduced

Engineering Contradiction:

Improvefluid temperatureVSAvoidelectrical output

Core Design Contradiction:

TemperatureVSProductivity

Solution Approach 1:

The system dynamically adjusts exhaust flow distribution across multiple heat exchangers based on real-time temperature conditions. By continuously optimizing the flow paths, the system maintains optimal operating temperatures that maximize steam generation and electrical output, eliminating the productivity losses associated with attemperation cycles.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The invention changes the operational parameters by eliminating the cooling phase of attemperation. By maintaining exhaust flow through optimized paths, the system keeps the fluid in continuous heating mode, preventing temperature excursions that would otherwise require cooling and subsequent re-heating, thereby maximizing electrical output.

Inventive Principle:

Principle #35Parameter changes

3Loss of energy

If multiple exhaust flow paths are implemented to control temperature without attemperation, then thermal efficiency is improved, but device complexity increases

Engineering Contradiction:

Improvethermal efficiencyVSAvoidexhaust flow path configuration

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

The multiple exhaust flow paths are designed to serve multiple functions: temperature control, efficiency optimization, and adaptability to different operating conditions. This multi-functionality justifies the increased complexity by delivering superior thermal efficiency and eliminating the need for attemperation equipment.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The control system acts as an intermediary that manages the complexity of multiple exhaust flow paths. By automating the selection and adjustment of flow paths based on temperature sensors and control algorithms, the system handles the complexity centrally, allowing the physical infrastructure to remain relatively simple while achieving sophisticated temperature control.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 thermal efficiency of the HRSG system by preventing overheating and underheating, thereby improving overall performance and reducing the need for attemperators, resulting in increased electrical output and efficiency.

Implementation Method 1

heat exchange between exhaust from a gas turbine and a first heat exchanger

Methodology Applied

Scientific EffectHeat exchange: Heat Exchanger

Implementation Method 2

using dampers to control the flow of exhaust through these paths

Methodology Applied

Scientific EffectFlow control: Valve

Data Source

PatentUS9074494B2System and apparatus for controlling temperature in a heat recovery steam generator

Publication Date: 2015.07.07 GENERAL ELECTRIC CO

AI summary

A system that controls temperature in a heat recovery steam generator (HRSG). One heat recovery steam generator system may include a first exhaust path. The heat recovery steam generator system also may include a second exhaust path. The heat recovery steam generator system may include a first damper configured to selectively allow a portion of an exhaust to flow through the second exhaust path.