Cross-flow Heat Exchanger Modules for SNOX Gas Separation
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Solution Overview
Problem
Existing gas-gas heat exchangers in SNOX/WSA systems suffer from partial mixing of gases, leading to reduced sulfur dioxide removal efficiency from 98% to 94%, due to their construction and operation, which affects the overall performance of the system.
Innovation Solution
A cross-flow heat exchanger with a plate-type design, featuring modules with orthogonal plate arrangements and serpentine paths for gases, ensuring counter-current flow and minimizing gas mixing through insulated heating and cooling spaces, along with a bypass system to manage flow rates and reduce corrosion risks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If Ljungström gas-gas heat exchanger is used, then investment cost is reduced and ease of cleaning is improved, but gas mixing occurs and sulfur dioxide removal efficiency deteriorates from 98% to 94%
Solution Approach 1:
The heat exchanger is divided into multiple independent modules (first module, second module, third module) arranged in series. Each module contains separate heating and cooling spaces with plate structures, allowing the system to process large gas flows while preventing mixing through physical segmentation. This modular design maintains the efficiency required for sulfur dioxide removal while enabling easier maintenance and cleaning of individual modules.
Solution Approach 2:
Insulating walls are introduced as intermediary elements between the heating spaces and cooling spaces to prevent direct contact and mixing of the two gas streams. These insulating partitions act as mediators that allow heat transfer while maintaining complete separation of the flue gases containing SO2 and the clean air stream, thus preserving the 98% removal efficiency.
2Power
If large dimensions heat exchanger is used to accommodate high flow rates, then heat exchange duty is improved, but device complexity and space requirements increase
Solution Approach 1:
The heat exchanger utilizes a three-dimensional modular arrangement where multiple modules are stacked or arranged in series along the gas flow path. Each module contains compact plate structures with heating and cooling spaces arranged in alternating layers. This dimensional organization allows the system to achieve high heat exchange duty (50 Gcal/hour) while maintaining a more compact overall footprint compared to traditional large-scale exchangers.
Solution Approach 2:
By segmenting the heat exchange function into multiple identical modules, the system can scale capacity by adding modules rather than increasing the size of a single complex unit. Each module handles a portion of the total flow rate (1 MNm3/hour), and the modular design simplifies manufacturing, installation, and maintenance while achieving the required heat exchange duty.
3Power
If counter-current cross-flow configuration is used, then heat transfer efficiency is improved, but pressure loss may increase
Solution Approach 1:
The counter-current cross-flow heat exchange is implemented in segmented modules rather than as a single large chamber. Each module contains plate structures that create alternating heating and cooling spaces, allowing the gases to flow in opposite directions through adjacent passages. This segmented approach maintains efficient heat transfer while reducing overall pressure loss by distributing the flow resistance across multiple smaller sections with optimized path lengths.
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
Maintains high sulfur dioxide removal efficiency, reduces corrosion risks, and facilitates easier maintenance by allowing independent operation and replacement of modules, while avoiding condensation issues and maintaining system performance even under low load conditions.
Implementation Method 1
a first gas to be heated and cooling a second gas to be cooled, moving along paths which are mutually inclined, and preferably perpendicular
Implementation Method 2
The plates are arranged in each module so that the heating faces of two side-by-side plates are mutually opposite, thus delimiting a heating space. Similarly, the two cooling faces of two side-by-side plates delimit a cooling space therebetween
Implementation Method 3
Within each module, the heating and the cooling spaces are separated by insulating walls
Data Source
AI summary
A counter-current cross-flow heat exchanger for heating a first gas and cooling a second gas, includes modules in fluid communication with one another, each module being positioned on a plane, the planes mutually overlapping. Conduits allow entry and exit of the first and second gases into and out of the exchanger. Each module has heat exchange plates, with heating and cooling faces. The plates are orthogonal to the module plane and parallel to define alternating heating and cooling spaces. The first gas crosses each heating space with a direction substantially parallel to the plane of each module and the second gas crosses each cooling space with a direction substantially orthogonal to the plane of each module. The cooling spaces between adjacent modules are in direct fluid communication. The heating spaces between adjacent modules are in fluid communication with one another by conduits/conveyors, creating a serpentine path.