Extractive Distillation Heat Integration for Aromatics Separation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing extractive distillation processes for separating aromatic and non-aromatic hydrocarbons are inefficient and require high utility consumption, particularly due to concerns over maldistribution and high reboiler duty in the solvent recovery column.
Innovation Solution
Implementing a solvent side draw from the recovery column to the extractive distillation column, combined with a stab-in reboiler preheater and internal heat exchangers, reduces utility consumption by redistributing heat and minimizing solvent flow, thereby improving energy efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an external process-process heat exchanger followed by a utility exchanger is used in the extractive distillation column reboiler, then the separation effectiveness is maintained, but the utility consumption increases and the reboiler preheater duty is limited by percent vaporization concerns
Solution Approach 1:
The patent combines the process-process heat exchanger and utility exchanger into a single integrated reboiler preheater system. This merging eliminates the need for separate external heat exchange stages, allowing direct heating of the reboiler feed while maintaining separation effectiveness and reducing utility consumption by 5-9.2%.
Solution Approach 2:
The patent extracts the heat transfer function from external exchangers and relocates it to an internal heat exchanger within the column. This extraction of the heating function from external equipment and its integration into the column structure eliminates maldistribution concerns and reduces the need for utility heating while maintaining effective separation.
2Use of energy by stationary object
If a side draw flow scheme is implemented to return solvent to the extractive distillation column, then the duty requirement at the recovery column reboiler decreases, but the reboiler preheater mean temperature difference is reduced due to lower hot side solvent flow rates
Solution Approach 1:
The patent applies local quality by creating different temperature zones within the reboiler preheater. The internal heat exchanger provides localized heating at the point of greatest need, allowing the system to operate with lower overall solvent flow rates while maintaining adequate temperature differences for effective heat transfer in the critical zones.
Solution Approach 2:
The internal heat exchanger acts as an intermediary between the hot solvent stream and the reboiler feed. It mediates the heat transfer process by providing a controlled interface for thermal energy exchange, enabling efficient heat recovery even when the hot side solvent flow rate is reduced by the side draw configuration.
3Use of energy by moving object
If an internal heat exchanger such as a stab-in reboiler preheater is used, then utility consumption is reduced and vaporization concerns are minimized, but the equipment complexity increases
Solution Approach 1:
The patent implements the nested doll principle by placing the heat exchanger tubes inside the reboiler vessel. The internal heat exchanger is nested within the existing reboiler structure, allowing heat transfer to occur within the column footprint without requiring additional external equipment. This reduces utility consumption while avoiding the complexity of multiple separate exchangers.
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 decreases utility consumption by 5-9.2% and allows for smaller equipment, addressing inefficiencies in existing designs by optimizing heat transfer and reducing solvent mass flow.
Implementation Method 1
transferring heat, in a first heat transfer zone, from the fifth stream to the first separation zone
Implementation Method 2
transferring heat, in a second heat transfer zone, from the fourth stream to the feed stream
Implementation Method 3
Extractive distillation is a separation method used in chemical processing, especially for the recovery of aromatics from a mixed stream of aromatic and non-aromatic hydrocarbons
Data Source
AI summary
Processes and apparatuses for separating aromatic and non-aromatic hydrocarbons by extractive distillation. A solvent is mixed with the aromatic and non-aromatic hydrocarbons. A first separation column separates non-aromatic hydrocarbons from the solvent and the aromatic hydrocarbons. A second separation column separates the aromatic hydrocarbons and the solvent. A side draw stream from the second separation column is used to heat the feed stream to the first separation column. A bottom stream from the second separation may be used to heat the liquid in the first separation column. A stab-in reboiler may be used to transfer heat from the bottoms stream to the liquid in the first separation column.