DIB Column Tray Diameter Optimization for Isobutane Separation
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Solution Overview
Problem
DIB columns in paraffin isomerization processes face inefficiencies due to lower vapor velocities and increased weeping in the lower portion, leading to reduced purity of isobutane products, as they operate with lower reboiling duties compared to the upper portion.
Innovation Solution
A DIB column configuration with an internal swage in the lower portion and fractionation trays of varying diameters, where the lower trays have a smaller diameter and bubbling area than the upper trays, along with a heat pump compressor and reboilers, to manage vapor velocities and prevent weeping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If DIB columns operate with lower reboiling duties in the lower portion compared to the upper portion, then energy efficiency is improved, but vapor velocities decrease and weeping increases
Solution Approach 1:
The patent applies local quality by varying the diameter of fractionation trays along the column height. Lower trays have smaller diameters while upper trays have larger diameters, creating localized structural differences that optimize vapor-liquid contact in each section. This allows the lower portion to maintain adequate vapor velocities with reduced reboiling duty, while the upper portion has larger trays for efficient separation of the remaining vapor-liquid mixture.
2Loss of energy
If DIB columns operate with lower reboiling duties in the lower portion, then energy efficiency is improved, but separation efficiency deteriorates due to weeping
Solution Approach 1:
The patent implements local quality through non-uniform tray diameters that are optimized for their specific location in the column. The smaller diameter trays in the lower portion prevent weeping by maintaining higher linear vapor velocities despite lower total vapor flow, while larger diameter trays in the upper portion provide sufficient contact area for effective separation. This localized optimization resolves the contradiction between energy efficiency and separation efficiency.
Solution Approach 2:
The patent changes the geometric parameter of tray diameter along the column height to optimize performance. By reducing tray diameter in the lower portion where vapor flow is lower, the linear velocity of vapor is maintained at levels sufficient to prevent liquid from passing through tray holes (weeping). This parameter change allows the system to operate with lower reboiling duty while maintaining separation efficiency.
3Ease of manufacture
If fractionation trays have uniform diameter, then manufacturing simplicity is maintained, but vapor-liquid contacting efficiency decreases in the lower portion
Solution Approach 1:
The patent applies local quality by making fractionation trays with different diameters at different heights. Lower trays have smaller diameters optimized for the lower vapor flow rates and higher liquid loads in that section, while upper trays have larger diameters. This localized optimization improves vapor-liquid contacting efficiency in each section without requiring complex manufacturing, as each tray can be fabricated as a simple cylindrical component with its specific diameter.
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 configuration enhances vapor velocities and reduces weeping in the DIB column, improving the separation efficiency and purity of isobutane production by optimizing vapor-liquid contacting zones and reboiler duties.
Implementation Method 1
The DIB column is configured for fractionating the paraffin isomerization-zone effluent to form a branched C4 hydrocarbon-rich stream
Implementation Method 2
The heat pump compressor is configured to receive a vapor portion of the branched C4 hydrocarbon-rich stream and to form a compressed branched C4 hydrocarbon-rich stream
Implementation Method 3
The upper reboiler is configured to heat the liquid fraction to form a second reboiler outlet stream that is returned to the DIB column above the internal swage
Implementation Method 4
The upper reboiler comprises an upper heat exchanger that is in fluid communication with the heat pump compressor to receive the compressed branched C4 hydrocarbon-rich stream for indirect heat exchange with the liquid fraction
Data Source
AI summary
Embodiments of apparatuses and methods for separating a paraffin isomerization-zone effluent are provided. In one example, an apparatus comprises a DIB column configured for fractionating the paraffin isomerization-zone effluent to form a branched C4 hydrocarbon-rich stream. The DIB column comprises a vessel. The vessel comprises a cylindrical wall that extends vertically and that encloses an internal cylindrical volume having a lower portion extending to an upper portion. An internal swage is disposed in the lower portion of the internal cylindrical volume. A plurality of fractionation trays includes an upper fractionation tray that is disposed in the internal cylindrical volume above the internal swage and a lower fractionation tray that is disposed in the internal swage. The lower fractionation tray has a smaller diameter than the upper fractionation tray.