Aromatics Recovery Column Side Draw for Lower-Reboiler Distillation
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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.
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
1Use of energy by stationary object
If an external process-process heat exchanger followed by a utility exchanger is used in the extractive distillation column reboiler, then heat transfer can be achieved, but utility consumption increases and maldistribution concerns arise
Solution Approach 1:
A heat transfer medium circulates through both the external heat exchanger and the internal stab-in heat exchanger, serving as an intermediary to transfer heat from the process stream to the reboiler while avoiding direct contact between the process stream and the heat source, thereby eliminating maldistribution concerns
Solution Approach 2:
The patent replaces the conventional direct-fire or simple heat exchanger system with a dual-exchanger system incorporating a heat transfer medium circulation loop, substituting a more complex mechanical arrangement to achieve better operational reliability and eliminate maldistribution issues
2Ease of operation
If the reboiler preheater duty is limited by percent vaporization to the utility reboiler, then maldistribution concerns are reduced, but utility consumption increases
Solution Approach 1:
The patent combines the function of the preheater and the reboiler into a unified system where both operations are performed through the same heat transfer medium circulation loop, merging two separate heat transfer functions into one integrated system to reduce overall utility consumption
Solution Approach 2:
The heat transfer medium circulation loop serves multiple functions simultaneously: it acts as the preheater medium, the reboiler heat source, and the heat transfer intermediary, providing multi-functionality that reduces the need for separate utility systems
3Use of energy by stationary object
If a stab-in reboiler preheater is used, then utility consumption decreases and MTD improves, but device complexity increases
Solution Approach 1:
The stab-in heat exchanger is nested within the reboiler assembly, with the heat transfer medium tubes inserted directly into the reboiler chamber, creating a nested configuration where one heat transfer system is embedded within another to improve thermal efficiency while containing complexity within a compact structure
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 process achieves a 5-9.2% reduction in utility consumption and allows for smaller equipment by optimizing heat transfer and reducing solvent-to-feed ratios, addressing inefficiencies in existing methods.
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.