Method for liquid-vapor contacting in a mass transfer column using multiple pass, parallel flow downcomer trays
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Solution Overview
Problem
Conventional mass transfer columns face limitations in high-capacity vapor-liquid contacting, particularly in high-pressure distillation systems, where the efficiency of mass transfer is hindered by inadequate liquid handling capacity and flow configuration, leading to issues like flooding and reduced mass transfer efficiencies.
Innovation Solution
A multiple pass downcomer tray design featuring an annular tray with multiple mass transfer decks, central and peripheral downcomers, liquid channel structures, weirs, and bubble forming structures, which promotes a serpentine liquid flow path and parallel flow arrangement across successive trays, enhancing liquid-vapor interaction and mass transfer efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional single pass or two pass trays are used, then the tray structure is simple, but the liquid handling capacity is insufficient and flooding occurs at high liquid rates
Solution Approach 1:
The tray is divided into multiple pass sections (typically 3-5 passes) with multiple downcomers distributed across the tray width. Liquid is distributed into multiple streams that flow in opposite directions across adjacent passes, increasing liquid handling capacity while maintaining manageable flow rates per downcomer
Solution Approach 2:
The invention transitions from single-direction liquid flow to multi-directional flow patterns by implementing opposite flow directions in adjacent passes. This dimensional change in flow configuration allows parallel liquid streams to coexist without interfering with each other, significantly increasing overall liquid capacity
2Productivity
If liquid flow rate is increased to handle high-capacity distillation, then productivity improves, but mass transfer efficiency decreases due to inadequate liquid-vapor contact time
Solution Approach 1:
The multiple pass configuration ensures continuous liquid flow across the entire tray surface through multiple sequential passes. Liquid that does not immediately contact vapor in one pass continues to flow through subsequent passes, ensuring complete utilization of vapor-liquid contact opportunities and maintaining high mass transfer efficiency at increased flow rates
Solution Approach 2:
By segmenting the liquid flow into multiple passes with opposite directions in adjacent passes, the invention creates multiple independent mass transfer zones. This segmentation allows high overall liquid capacity while maintaining adequate contact time in each localized zone, preventing the efficiency loss that would occur with a single high-velocity flow path
3Quantity of substance
If downcomer area is increased to handle higher liquid rates, then liquid capacity improves, but the active area for vapor-liquid contact is reduced
Solution Approach 1:
The total downcomer capacity is segmented into multiple smaller downcomers distributed across the tray. This segmentation allows the liquid handling capacity to be distributed across multiple locations, reducing the area required by each individual downcomer while maintaining the total liquid discharge capacity needed for high-capacity operation
Solution Approach 2:
The multiple downcomers serve dual functions: they collectively provide the total liquid discharge capacity needed for high liquid rates, and their distributed configuration minimizes the total area occupied by downcomers compared to a single large downcomer, thereby preserving maximum active tray area for vapor-liquid contact
4Reliability
If parallel flow arrangement is implemented across successive trays, then mass transfer efficiency improves due to uniform driving forces, but the tray configuration becomes more complex
Solution Approach 1:
The invention implements parallel flow arrangement by inverting the flow direction in adjacent passes - while liquid flows in one direction in one pass, it flows in the opposite direction in the adjacent pass. This inversion creates parallel flow patterns across successive trays, ensuring uniform mass transfer driving forces throughout the column while using a systematic design approach
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 design significantly improves mass transfer efficiency by optimizing liquid flow paths, reducing weir loading, and maintaining uniform driving forces across the column, thereby enhancing the overall performance of high-capacity vapor-liquid contacting operations.
Implementation Method 1
vapor bubbling through the apertures in the tray deck
Implementation Method 2
The vapor and liquid interaction on the tray desirably causes a froth to build up on the tray
Implementation Method 3
Downcomers are conventionally provided in combination with the vapor-liquid contacting trays to provide a passage through which liquid is discharged from one tray to an underlying tray
Data Source
AI summary
A multiple pass, parallel flow downcomer tray for a mass transfer column and method for liquid-vapor contacting in a mass transfer column is provided. The multiple pass, parallel flow downcomer tray has at least four mass transfer decks configured to provide contact between an ascending vapor passing upward through apertures on the tray surface and a traversing liquid on the tray surface. The tray further includes a central downcomers disposed near a central axis of the tray and two or more peripheral downcomers disposed near the edge of the tray and spaced apart from the central axis, wherein at least two of the four mass transfer decks are configured to discharge the traversing liquid into the peripheral downcomers and two of the four mass transfer decks are configured to discharge the traversing liquid into the central downcomer.