Shell Downcomer Tray With Demister for High-Capacity Distillation
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Solution Overview
Problem
Existing vapor-liquid contacting devices in fractional distillation face challenges in achieving high capacity and efficiency, particularly in fractional distillation columns used for separating volatile chemicals like hydrocarbons, where improvements are sought in both capacity and efficiency.
Innovation Solution
A vapor-liquid contacting apparatus and process utilizing a half module with a downcomer and demister configuration that enhances liquid distribution and vapor-liquid separation, incorporating modular demister units and perforated decks for co-current contacting, which increases mass transfer efficiency and reduces the number of required modules.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional fractionation trays are used, then vapor-liquid contacting is achieved, but mass transfer efficiency and capacity are limited
Solution Approach 1:
The invention divides the vapor-liquid contacting function into separate functional zones: a downcomer zone for liquid discharge and a contacting zone for mass transfer. This segmentation allows each zone to be optimized independently, improving overall mass transfer efficiency while reducing the number of trays needed compared to conventional integrated trays.
Solution Approach 2:
The invention introduces a vertical dimension to the contacting process by using a downcomer that extends vertically to discharge liquid below the tray level, while vapor contacts liquid from above. This three-dimensional arrangement increases contacting efficiency without adding horizontal complexity, allowing better separation performance with fewer trays.
2Productivity
If multiple downcomer trays are used, then vapor and liquid capacities increase, but device complexity increases
Solution Approach 1:
The downcomer structure serves multiple functions simultaneously: it discharges liquid from the tray, provides a pathway for vapor-liquid contact, and acts as a support structure for the tray deck. This multi-functionality increases vapor and liquid capacities without proportionally increasing structural complexity, as the same elements perform multiple roles.
Solution Approach 2:
The invention merges the downcomer function with the tray support structure, where the downcomer is integrated into the tray assembly rather than being a separate component. This merging reduces the number of discrete parts and simplifies the overall structure while maintaining high vapor and liquid capacities through efficient flow paths.
3Stress or pressure
If structured packing is used, then pressure drop is reduced, but capacity is limited
Solution Approach 1:
The invention uses hydraulic principles in the downcomer design to control liquid flow and vapor-liquid interaction. The downcomer geometry and liquid discharge mechanisms utilize fluid dynamics to maintain low pressure drops while handling high liquid capacities, achieving both low pressure drop and high capacity simultaneously through optimized flow paths and discharge designs.
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 apparatus achieves higher mass transfer efficiency and capacity in fractional distillation columns by optimizing vapor-liquid contact through the downcomer and demister design, reducing module count and maintaining pressure drop, thereby enhancing separation efficiency and cost-effectiveness.
Implementation Method 1
a downcomer against a shell of a vessel for transporting and distributing liquid to a subjacent stage
Implementation Method 2
The downcomer is equipped with a demister at its outlet for vapor-liquid separation
Implementation Method 3
co-current mass transfer zone. A co-current contacting device can also achieve high mass transfer efficiency through the co-current contacting of fine liquid droplets with vapor
Implementation Method 4
The passage of the vapor through the liquid generates a layer of bubbles referred to as froth. The high surface area of the froth helps to quickly establish a compositional equilibrium between the vapor and liquid phases on the tray
Data Source
AI summary
A high capacity and high efficiency vapor-liquid contacting apparatus and process is useful in distillation columns and other vapor-liquid contacting processes. The apparatus is characterized by a half module comprising a downcomer against a shell of a vessel for transporting liquid to a subjacent stage which utilizes a demister to effect vapor-liquid separation at the downcomer outlet.