Vacuum Distillation Columns for Aromatic Separation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for separating benzene and toluene from C8+ compounds in aromatic complexes require significant energy due to the need for recompression of low-pressure vapour used as a heat transfer fluid, which is inefficient and costly.
Innovation Solution
Operating certain distillation columns under vacuum conditions, allowing for direct exchange or generation of low-pressure steam without recompression, to reduce energy consumption and improve separation efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If low-pressure vapour is used as a heat transfer fluid in reboilers, then energy saving is achieved, but recompression is required for most columns which increases device complexity and energy consumption
Solution Approach 1:
The patent changes the operating pressure parameter of distillation columns from atmospheric or positive pressure to vacuum operation. This parameter change allows the columns to be heated by low-pressure vapour from other columns without requiring recompression, as the vacuum columns can accept heat input at lower temperatures and pressures. The pressure parameter transformation enables direct heat exchange between columns operating at different pressure levels.
Solution Approach 2:
Instead of using compressors to increase the pressure of low-pressure vapour to match column requirements, the patent inverts the approach by operating columns under vacuum so that their lower operating pressure matches the low-pressure vapour conditions. This inversion eliminates the need for mechanical compression while maintaining the heat transfer function.
2Loss of energy
If columns are operated under vacuum, then direct exchange of low-temperature energy is possible without recompression, but separation efficiency must be maintained
Solution Approach 1:
The patent applies parameter changes by operating distillation columns under vacuum conditions (reduced pressure), which lowers the boiling points of components and enables separation at lower temperatures. This parameter change allows direct heat exchange with vacuum columns using low-pressure vapour without recompression, reducing electrical consumption while maintaining separation efficiency through optimized vacuum operation.
Solution Approach 2:
The patent uses low-pressure vapour as an intermediary heat transfer medium between heat-producing columns and vacuum columns. This intermediary enables thermal energy transfer without requiring mechanical compression, as the vapour naturally condenses in the vacuum columns at lower pressures and temperatures, facilitating efficient heat exchange while maintaining separation performance.
3Use of energy by moving object
If recompression of low-pressure vapour is implemented, then heat transfer efficiency improves, but energy consumption increases
Solution Approach 1:
The patent changes the pressure parameter of the distillation columns to vacuum operation, which allows them to receive heat from low-pressure vapour without requiring compression. This parameter change eliminates the electrical energy consumption associated with compressors while maintaining effective heat transfer, as the vacuum columns can condense the low-pressure vapour directly at their operating conditions.
Solution Approach 2:
The patent replaces the mechanical compression system with a vacuum-based thermal exchange system. Instead of using mechanical compressors to increase vapour pressure for heat transfer, the system uses vacuum-operated columns that can accept and condense low-pressure vapour directly, substituting mechanical energy input with thermal energy transfer driven by pressure and temperature gradients.
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 approach reduces energy consumption by eliminating the need for recompression, achieving a 46% reduction in electrical consumption across the complex and maintaining high recovery rates of C8+ compounds while minimizing light compound content in top products.
Implementation Method 1
at least one of said distillation columns is operated under vacuum so that: the majority of the compounds comprising 7 carbon atoms or less are recovered in the top of the distillation column operated under vacuum, and the majority of the compounds comprising 8 carbon atoms or more are recovered in the product at the bottom of the distillation column operated under vacuum
Implementation Method 2
the reboiler of the distillation column operated under vacuum is operated at a temperature of less than 180° C.
Implementation Method 3
a low-temperature heat is introduced into the reboiler of the distillation column operated under vacuum, from low-temperature energy available in the separation device, either by direct exchange, or by means of the generation of steam used without recompression
Data Source
AI summary
The present invention relates to a process and a device for separating a feedstock comprising benzene, toluene and C8+ compounds, by means of at least one “reformate” distillation column (C1), one aromatics extraction unit (P1), one para-xylene separation unit (P2), one xylene isomerization unit (P3) and one transalkylation unit (P4), the effluents of said units being separated in the following distillation columns: purification column (C6), deheptanizer (C7) and toluene column (C10), in which at least one of said distillation columns is suitable for being operated under vacuum so that: the majority of the C7− compounds are recovered in the product at the top of the distillation column operated under vacuum, and the majority of the C8+ compounds are recovered in the product at the bottom of the distillation column operated under vacuum.