Shell-and-Tube Heat Exchanger Inversion for Corrosion Control
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Solution Overview
Problem
Conventional shell-and-tube waste heat boilers face issues with corrosion due to deposition of water-suspended solids, non-uniform water distribution, and overheating, leading to reduced reliability and increased costs, as well as the need for external steam drums that elevate equipment and space requirements.
Innovation Solution
A novel design where evaporation occurs in the tube side with integrated vapor fraction separation using gravity, aided by a separator, and controlled liquid level regulation to ensure homogeneous tube heating and steam purity, eliminating external drums and reducing corrosion risks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If evaporation occurs in the shell side with integrated steam drum, then equipment complexity is reduced, but corrosion and deposition of water-suspended solids occur leading to reduced reliability
Solution Approach 1:
The patent inverts the conventional arrangement by placing the evaporating medium inside the tubes rather than in the shell side. This inversion prevents water-suspended solids from depositing on the tube outer surfaces and tube sheet, eliminating the corrosion and deposition problems that reduce reliability while maintaining equipment compactness.
Solution Approach 2:
The patent introduces a heating section with enhanced heating capacity at the inlet region where the evaporating medium first enters. This local quality enhancement ensures uniform heat distribution and prevents dry-out conditions in critical areas, thereby improving overall system reliability without increasing overall equipment complexity.
2Productivity
If non-uniform water distribution in shell side occurs, then evaporation efficiency increases in certain regions, but deposition of solids and dry out occur reducing reliability
Solution Approach 1:
By inverting the flow arrangement and placing water inside the tubes, the patent ensures uniform water distribution through all tube passages. This eliminates the non-uniform distribution problem in the shell side while maintaining high evaporation efficiency through the enhanced heating section that provides intensified heat transfer where needed.
3Productivity
If inlet gas temperature is too high for tube material, then heat recovery capacity increases, but tube material corrosion and overheating occur
Solution Approach 1:
The patent introduces a heating section that pre-heats the evaporating medium before it enters the main evaporation zone. This preliminary action ensures that the tube material is protected from excessive temperatures at the inlet region, preventing corrosion and overheating while maintaining high heat recovery capacity in the subsequent evaporation sections.
4Reliability
If external steam drum is used for steam separation, then steam separation efficiency improves, but equipment cost and space requirements increase
Solution Approach 1:
The patent merges the steam separation function directly into the shell side of the heat exchanger, eliminating the need for a separate external steam drum. The shell side serves dual purposes: as the steam separation chamber and as the collection chamber for the evaporating medium, thereby reducing equipment cost and space requirements while maintaining effective steam separation.
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 design reduces corrosion and overheating by ensuring uniform heating of all tubes, eliminates the need for external separation equipment, and lowers overall costs by preventing solid deposition and maintaining high steam purity without external steam drums.
Implementation Method 1
separation of vapour fraction from liquid fraction (for example steam from water) by means of gravity, possibly with the help of a suitable separator
Implementation Method 2
evaporation of water takes place in the shell side
Implementation Method 3
shell-and-tube apparatus for heat recovery from a hot process stream
Data Source
Figure 1
Figure 2
AI summary
A shell-and-tube apparatus (1), suitable for use as a waste heat boiler, comprising a vessel with an exchanging section (2) and a separating section (3), wherein: said exchanging section (2) contains a bundle of U-tubes (4) fed with an evaporable liquid medium such as water (W) and exposed to a hot gas (G) flowing in a hot chamber around said tubes, so that said medium is partially evaporated in the tubes while recovering heat from hot gas flowing in the hot chamber (7); said separating section (3) comprises a collection chamber (16) in communication with outlet of the tubes (4) to receive the partially evaporated medium leaving the tubes; said separating section (3) is arranged to provide separation of vapour fraction and liquid fraction from the partially evaporated medium at least partially by gravity; the apparatus also comprises means for controlling the liquid level in the collection chamber and for a partial recycle of the non-evaporated liquid.