Extractive Distillation Column for Ethanol Dehydration
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current methods for producing anhydrous ethanol from fermentation broth are energy-intensive, particularly in concentrating ethanol beyond the azeotropic composition, which poses economic impediments for using ethanol as a gasoline blending stock or engine fuel.
Innovation Solution
An improved extractive distillation process with reduced liquid reflux in the extractive distillation column, utilizing high-boiling solvents that preferentially extract water or ethanol, allowing for partial ethanol recovery in a post-distillation column or recycling to a pre-distillation column, thereby reducing energy input and solvent entrainment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional distillation is used to concentrate ethanol to azeotropic composition, then ethanol concentration is improved, but energy consumption increases significantly
Solution Approach 1:
A high-boiling solvent is introduced as an intermediary substance into the distillation column. This solvent selectively interacts with water through hydrogen bonding, forming solvent-water complexes that preferentially move to the liquid phase. This mediator enables water removal and ethanol concentration without requiring the high energy input of conventional distillation, achieving azeotropic composition at lower energy costs
Solution Approach 2:
The invention changes the physical-chemical parameters of the separation system by introducing a solvent with specific properties (high boiling point, selective water affinity). This parameter change modifies the vapor-liquid equilibrium relationships, allowing ethanol to be concentrated to azeotropic composition at lower temperatures and energy consumption compared to conventional distillation
2Manufacturing precision
If extractive distillation with high liquid reflux is used, then separation efficiency is improved, but energy consumption increases
Solution Approach 1:
The high-boiling solvent acts as a mediator that enhances the separation efficiency by selectively binding water molecules. This solvent-mediated mechanism achieves effective water-ethanol separation without requiring high liquid reflux ratios, thereby maintaining good separation efficiency while significantly reducing the energy consumption associated with heating and circulating large volumes of liquid reflux
Solution Approach 2:
The invention changes the operational parameters by reducing the liquid reflux ratio while maintaining separation efficiency through the solvent's selective water affinity. This parameter change from high reflux to low reflux operation, enabled by the extractive solvent, directly reduces the energy input required for the distillation process
3Quantity of substance
If azeotropic distillation is used to break the ethanol-water azeotrope, then anhydrous ethanol production is improved, but pre-concentration energy requirements increase
Solution Approach 1:
The high-boiling solvent serves as an intermediary that directly breaks the ethanol-water azeotrope through selective water complexation. This eliminates the need for energy-intensive pre-concentration to near-azeotropic composition, as the solvent enables water removal and anhydrous ethanol production from lower concentration feeds, significantly reducing pre-concentration energy requirements
Solution Approach 2:
The solvent is introduced into the distillation column at a position above the feed entry point, performing preliminary water extraction action before the vapor-liquid equilibrium stages. This preliminary action by the solvent prepares the vapor phase for efficient ethanol recovery, reducing the overall energy requirement for achieving anhydrous ethanol from dilute fermentation broth
4Manufacturing precision
If molecular sieve adsorption is used for dehydration, then ethanol purification is improved, but operating costs and complexity increase
Solution Approach 1:
The high-boiling solvent acts as a continuous-phase intermediary that selectively extracts water from the ethanol stream through hydrogen bonding. This continuous extractive distillation approach using a solvent mediator achieves high ethanol purification without the complex batch-wise adsorption-desorption cycles of molecular sieves, reducing device complexity and operating costs while maintaining purification effectiveness
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 process significantly reduces energy requirements and operational costs, achieving high-purity anhydrous ethanol production with minimal solvent contamination, making it more economically viable for ethanol use in gasoline blending.
Implementation Method 1
introducing a high-boiling water selective solvent into an upper portion of the EDC to contact the aqueous feedstock under extractive distillation conditions to produce a liquid bottoms stream that comprises water and high-boiling water selective solvent
Implementation Method 2
introducing an aqueous feedstock comprising ethanol and water into a middle portion of an extractive distillation column (EDC)
Implementation Method 3
feeding at least a portion of the liquid bottoms stream of the EDC into a solvent recovery column (SRC) to remove water therefrom and to yield a lean high-boiling water selective solvent stream
Data Source
AI summary
An energy-efficient extractive distillation process for producing anhydrous ethanol from aqueous/ethanol feeds containing any range of ethanol employs an extractive distillation column (EDC) that operates under no or greatly reduced liquid reflux conditions. The EDC can be incorporated into an integrated process for producing anhydrous ethanol used for gasoline blending from fermentation broth. By using a high-boiling extractive distillation solvent, no solvent is entrained by the vapor phase to the EDC overhead stream, even under no liquid reflux conditions. The energy requirement and severity of the EDC can be further improved by limiting ethanol recovery in the EDC. In this partial ethanol recovery design, ethanol which remains in the aqueous stream from the EDC is recovered in a post-distillation column or the aqueous stream is recycled to a front-end pre-distillation column where the ethanol is readily recovered since the VLE curve for ethanol/water is extremely favorable for distillation.