Inflatable bladder damper for heat recovery steam generator stack
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Solution Overview
Problem
Heat loss through the stack of a heat recovery steam generator during outage periods leads to increased fuel costs and longer startup times, causing cyclical stresses in components due to uneven thermal expansion and contraction, and existing metallic dampers are not retrofittable into existing stacks without significant modifications.
Innovation Solution
A lightweight damper assembly with an inflatable bladder, supported by a tripod-like mounting assembly, that can be easily installed in existing heat recovery steam generator stacks to create a fluid-tight seal during shutdowns, minimizing heat loss and reducing thermal stresses by maintaining internal component temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If metallic dampers are used to prevent heat loss through the stack during shutdown, then heat loss is reduced and thermal stresses are minimized, but the weight of the dampers requires complete redesign of the stack and foundations
Solution Approach 1:
The patent uses a pneumatic system with an inflatable bladder to create a light-weight damper that can seal the stack during shutdown. The bladder is inflated with air or gas to expand and block the stack opening, replacing the need for heavy metallic dampers while achieving the same heat loss prevention function
Solution Approach 2:
The patent employs a flexible bladder made of heat-resistant material that can be inflated to seal the stack. This flexible membrane structure provides the sealing function without the weight of rigid metallic dampers, allowing easy installation in existing stacks without structural redesign
2Loss of time
If metallic dampers are installed to reduce heat loss, then fuel cost and startup time are reduced, but significant modifications to existing stack and foundation are required
Solution Approach 1:
The pneumatic bladder damper can be easily installed in existing stacks without structural modifications. The lightweight design allows for simple mounting using minimal support structures, and the pneumatic inflation system can be connected to existing air supplies or portable compressors, enabling rapid deployment and reducing startup time
Solution Approach 2:
The bladder damper is designed as a temporary, replaceable component that can be easily installed and removed as needed. This disposable-like approach eliminates the need for permanent, complex installations while achieving the same heat loss prevention and startup time reduction benefits
3Adaptability or versatility
If frequent shutdown and startup occur, then operational flexibility is improved, but cyclical thermal stresses increase due to uneven temperature changes in thick-walled components
Solution Approach 1:
The bladder damper is inflated immediately upon shutdown to prevent heat loss and maintain component temperatures. This preliminary action prevents the temperature drops that cause thermal contraction and stress, allowing frequent shutdowns without compromising component strength
Solution Approach 2:
The patent converts the potential harm of frequent shutdowns (which cause thermal stress) into a benefit by using the shutdown period to inflate the bladder and maintain heat. The controlled environment created by the sealed stack transforms the harmful thermal cycling into a controlled thermal maintenance opportunity
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
The damper assembly effectively reduces heat loss and thermal stresses, allowing for quicker and more efficient startup, lowering fuel costs and extending the lifespan of power generation components without requiring stack or foundation redesigns.
Implementation Method 1
The bladder is selectively movable between a first position in which the bladder is deflated and received within the housing, and a second position in which the bladder is positioned outside the housing and inflated
Data Source
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AI summary
A damper assembly for minimizing heat loss through an exhaust stack includes a housing mounted within the stack and a bladder received within the housing. The bladder is selectively movable between a first position in which the bladder is deflated and received within the housing, and second position in which the bladder is positioned outside the housing and inflated such that a peripheral surface of the bladder contacts an interior sidewall of the stack to create a gas seal. A damper assembly can be used for minimizing heat loss through a stack of a heat recovery steam generator. A method for minimizing heat loss through an exhaust stack comprises the steps of mounting a damper assembly withing the exhaust stack, upon entering shutdown mode inflating the bladder, and upon entering restart mode deflating said bladder.