Parallel Tube Bundle Steam Generator for Flexible Low-Load Operation
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Solution Overview
Problem
Heat recovery steam generators face challenges in adapting to fluid flow rate changes, requiring frequent start/stop cycles, and maintenance issues due to scale deposition, leading to inefficiencies and instability, especially in once-through steam generators at low loads.
Innovation Solution
A heat exchanger design with multiple parallel tube bundles in separate shell sections, allowing for independent fluid flow control and easy access for maintenance, and a bypass duct for improved insulation and strength, enabling continuous operation and flexibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a single large tube bundle is used in heat recovery steam generators, then heat exchange capacity is sufficient, but maintenance becomes difficult due to weight and accessibility issues
Solution Approach 1:
The heat exchanger is divided into multiple separate shell sections (first shell section, second shell section, third shell section) with tube bundles in each section. This segmentation allows each tube bundle to be independently accessed and maintained without handling the entire large bundle, solving the accessibility issue while maintaining sufficient total heat exchange capacity across all sections.
2Adaptability or versatility
If heat recovery steam generators operate at low loads, then production flexibility is improved, but steam generator stability deteriorates
Solution Approach 1:
By having multiple independent shell sections with tube bundles, the system can selectively operate different sections at different loads. This allows the steam generator to maintain stability by distributing flow across multiple bundles rather than forcing a single bundle to operate at unstable low loads, while still providing production flexibility.
Solution Approach 2:
The system incorporates flow distributing means that can dynamically adjust and redistribute the first heat exchange fluid between different shell sections based on operating conditions. This dynamic flow distribution enables stable operation across a wide range of loads by optimizing fluid allocation to active tube bundles.
3Adaptability or versatility
If frequent start/stop cycles are required, then production flexibility is improved, but system reliability deteriorates
Solution Approach 1:
Multiple independent shell sections allow the system to perform warm-up and cooldown operations in individual sections without affecting others. During start/stop cycles, certain sections can be maintained in a ready state while others are cycled, distributing thermal stress and improving overall system reliability while maintaining production flexibility.
4Loss of energy
If scale deposits on tube surfaces, then heat transfer coefficient is reduced, but maintenance frequency increases
Solution Approach 1:
The segmented design with multiple accessible shell sections allows for targeted maintenance of individual tube bundles. Scale deposits can be addressed in specific sections without halting the entire system, reducing maintenance frequency impact and allowing continuous operation while maintaining heat transfer efficiency through periodic localized cleaning.
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
Enhances operational flexibility, reduces maintenance complexity, and maintains efficiency by allowing different fluid and pressure combinations, preventing instability and scale deposition, even under varying load conditions.
Implementation Method 1
a waste heat recovery unit, i.e. a heat exchanger configured to transfer the residual enthalpy of the exhaust fluid of the heat source to a working fluid of the waste heat recovery system
Implementation Method 2
one fluid flows inside one or more tubes, forming a tube bundle, while the other fluid flows outside the tubes, in a volume confined inside a shell
Data Source
AI summary
The disclosure concerns a heat exchanger, and in particular a waste heat recovery unit used to generate steam. In particular, the heat exchanger is provided with two or more separate tube bundles, each tube bundle being arranged in a separate section of a shell. An additional separate by-pass section is arranged in the middle of the shell. A first heat exchanging fluid, in particular a waste heat fluid, flows through the shell and is distributed between the separate sections of the shell and a second heat exchanging fluid, in particular water, flows through each tube bundle and exchanges heat with the first heat exchanging fluid. Alternatively, at least one tube bundle is flown by a different heat exchanging fluid.