Membrane Augmented Distillation for Solvent Dehydration
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Solution Overview
Problem
Current processes for producing high-purity dehydrated solvents, such as ethanol, are energy-intensive and costly, particularly in the dehydration of solvents miscible with water, as they require significant energy and large membrane areas.
Innovation Solution
A process integrating distillation, vapor compression, and two membrane separation steps, where the rectified vapor is compressed and then subjected to selective membrane separation to enrich the solvent, with the permeate streams being recycled to recover latent heat and optimize membrane efficiency, reducing energy consumption and membrane area requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional distillation and molecular sieve drying are used to produce high-purity dehydrated solvents, then high purity product is achieved, but energy consumption is extremely high
Solution Approach 1:
The patent changes the physical state parameter of the solvent from liquid to vapor phase, enabling membrane separation instead of conventional liquid-phase drying methods. This phase change allows the use of selective vapor permeation membranes that can separate alcohol from water vapor, achieving high purity with lower energy consumption by operating at lower temperatures without molecular sieves
Solution Approach 2:
The patent replaces the mechanical molecular sieve drying system with a membrane-based vapor separation system. Instead of using physical adsorption in molecular sieves, the invention uses selective vapor permeation through membranes, substituting one separation mechanism with another that operates more efficiently at lower energy input
2Use of energy by moving object
If membrane separation is used to treat overhead stream from column, then energy efficiency is improved, but large membrane area is required
Solution Approach 1:
The patent applies preliminary concentration of the solvent in the overhead stream from the distillation column before subjecting it to membrane separation. By pre-concentrating the alcohol vapor in the overhead stream, the subsequent membrane separation step requires less membrane area to achieve the desired purity, as the separation burden is reduced
Solution Approach 2:
The patent divides the separation process into two distinct stages: first, distillation to concentrate the solvent in the overhead stream; second, membrane separation to achieve final dehydration. This segmentation allows each process to operate in its optimal range, reducing the overall membrane area required compared to using membrane separation alone on dilute 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 integrated process achieves high-purity solvent production with reduced energy consumption and costs by leveraging vapor compression and membrane separation to control energy usage and membrane area, while also recovering latent heat, thereby enhancing overall process efficiency.
Implementation Method 1
compressing at least a portion of the rectified vapor stream to form a compressed overhead vapor stream
Implementation Method 2
passing at least a portion of the compressed overhead vapor stream at a first feed pressure across the first feed side of the membrane; maintaining a first permeate pressure on the first permeate side that is lower than the first feed pressure
Implementation Method 3
recovering latent heat of condensation from the first permeate stream by returning the first permeate stream as a vapor to the stripping section
Data Source
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AI summary
Processes for removing water from organic solvents, such as ethanol. The processes include distillation to form a rectified overhead vapor, compression of the rectified vapor, and treatment of the compressed vapor by two sequential membrane separation steps.