Membrane-Augmented Distillation for Low-Energy Solvent Dehydration
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Solution Overview
Problem
Conventional processes for producing high-purity dehydrated solvents, such as ethanol, are energy-intensive and costly, especially when dealing with low concentrations of solvents, where energy consumption exceeds the energy content of the product.
Innovation Solution
A process involving two distillation steps operated at different pressures, followed by one or two membrane separation steps, with heat recovery and recirculation of streams to optimize energy efficiency and reduce capital costs, utilizing membranes selective for water over solvents to enhance solvent dehydration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional distillation processes are used to produce high-purity dehydrated solvents from low-concentration aqueous mixtures, then the desired purity level is achieved, but energy consumption becomes excessively high
Solution Approach 1:
The process segments the separation task into two distinct stages: a distillation column for initial concentration and a membrane separation unit for final dehydration. This division allows each unit to operate optimally within its specific function, with the distillation column handling the bulk water removal and the membrane unit achieving the final high-purity separation, thereby reducing the overall energy burden compared to using distillation alone for the entire purification range
Solution Approach 2:
The membrane separation step operates at different pressure parameters than conventional distillation, using pressure-driven permeation rather than thermal energy. By changing the separation mechanism from thermal (distillation) to pressure-driven (membrane), the process achieves effective dehydration with significantly lower energy consumption, especially for the final stages of purification
2Manufacturing precision
If multiple distillation columns are used in series to separate organic/water mixtures, then separation efficiency is improved, but capital costs and process complexity increase
Solution Approach 1:
The process merges thermal separation (distillation) with membrane separation in a hybrid system. Instead of using multiple distillation columns which would require multiple reboilers, condensers, and control systems, the invention combines one distillation column with a membrane separation unit, reducing the number of complex thermal processing stages while achieving equivalent or superior separation efficiency
Solution Approach 2:
The membrane separation unit replaces what would otherwise require additional mechanical distillation columns. The membrane process uses pressure-driven permeation through selective membranes rather than thermal cycles, eliminating the need for additional reboilers, condensers, and associated mechanical complexity while achieving effective dehydration
3Use of energy by moving object
If membrane separation is used alone to treat overhead streams, then energy consumption is reduced, but achieving high purity levels becomes difficult
Solution Approach 1:
The distillation column performs a preliminary concentration action before the membrane separation step. By pre-concentrating the solvent in the distillation column, the feed to the membrane unit has a higher initial concentration, which makes the membrane separation more effective and easier to achieve the final high-purity target. This preliminary thermal processing reduces the burden on the membrane system
4Manufacturing precision
If low-concentration solvent feeds are processed through conventional dehydration processes, then high-purity product is achieved, but energy consumption exceeds the energy content of the product
Solution Approach 1:
The process segments the energy-intensive dehydration task into a low-energy distillation stage for initial concentration and a pressure-driven membrane stage for final dehydration. This segmentation allows the membrane unit to handle the most energy-sensitive final purification steps without the high thermal energy input required by conventional distillation, making the overall process energy consumption lower than the energy content of the produced solvent
Solution Approach 2:
The membrane separation operates under pressure parameters rather than high thermal parameters. By changing from thermal energy input to pressure-driven separation for the critical dehydration steps, the process achieves effective separation with energy consumption that is a small fraction of what would be required by conventional thermal processes, especially for low-concentration feeds
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 significantly reduces energy consumption and costs while achieving high-purity solvent production, particularly effective for low-concentration solvent streams, by integrating distillation and membrane separation to enhance energy efficiency and control capital expenditures.
Implementation Method 1
the membrane being selective in favor of water over solvent
Implementation Method 2
providing a membrane having a feed side and a permeate side, the membrane being selective in favor of water over solvent
Implementation Method 3
subjecting at least a first portion of the mixture to a first distillation step
Implementation Method 4
passing a first feed stream of the mixture, at a first pressure, into a first distillation column having a first reboiler system
Implementation Method 5
condensing at least a portion of the compressed overhead vapor stream to form a condensed overhead stream
Data Source
AI summary
Disclosed herein are processes for removing water from organic solvents, such as ethanol. The processes include distillation in two columns operated at sequentially higher pressure, followed by treatment of the overhead vapor by one or two membrane separation steps.