Ethanol Dewatering via Mechanical Recompression and Evaporation
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Solution Overview
Problem
Current methods for dewatering ethanol-water mixtures, such as distillation, multi-component distillation, extractive distillation, molecular sieves, and pervaporation, are energy-intensive and costly, with high energy consumption and chemical usage, and do not efficiently achieve low-energy separation under industrial conditions.
Innovation Solution
A method involving evaporation, distillation, compression, heat exchanging, and vapour permeation or molecular sieve processes, where the ethanol-water mixture is split into reflux and evaporator feed flows, with mechanical recompression of the combined discharge flows to achieve low-energy separation, using the retentate as an energy source and minimizing external energy input.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional distillation is used to reduce water content below azeotropic point, then ethanol purity is improved, but energy consumption increases significantly
Solution Approach 1:
The process segments the feed stream into two partial feed flows: one charged to a distillation column and another to an evaporator. This segmentation allows different separation mechanisms to work in parallel, reducing the energy burden on any single unit and enabling more efficient overall water removal below azeotropic composition.
Solution Approach 2:
The invention utilizes phase transitions in multiple forms: evaporation of the second partial feed flow, condensation of vapour from both distillation column and evaporator, and subsequent re-evaporation in the distillation column. These phase transitions are strategically employed to separate ethanol from water while recovering and reusing thermal energy throughout the process.
2Manufacturing precision
If multi-component distillation or extractive distillation is used to achieve low water content, then separation efficiency is improved, but chemical usage and complexity increase
Solution Approach 1:
The invention extracts and removes water from the ethanol-water mixture through a combination of distillation and evaporation processes, achieving separation without requiring additional chemical extraction agents. This physical separation approach simplifies the process compared to extractive distillation while maintaining high water removal efficiency.
3Manufacturing precision
If molecular sieve or vapour permeation is used for dewatering, then separation is achieved, but operational availability decreases due to batch operation and membrane lifetime issues
Solution Approach 1:
The invention employs continuous distillation and evaporation processes rather than batch operations. The distillation column and evaporator operate continuously with steady feed streams, ensuring uninterrupted ethanol production and significantly improving operational availability compared to batch molecular sieve processes.
4Use of energy by moving object
If pervaporation is used for dewatering, then energy consumption is reduced, but membrane robustness and lifetime are compromised
Solution Approach 1:
The invention introduces a distillation column as an intermediary process between the evaporator and final product delivery. This intermediary handles the harsh separation conditions, protecting any downstream components and allowing the evaporator to operate under more benign conditions, thereby extending component lifetime while maintaining low energy consumption.
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 method significantly reduces energy consumption by utilizing mechanical recompression and heat recovery, achieving high operational availability and cost-efficiency in industrial-scale ethanol dewatering, with minimal external energy input and low water content in the retentate.
Implementation Method 1
an evaporator as an evaporator feed flow, leaving the top of the evaporator as an evaporator discharge flow
Implementation Method 2
a distillation column as a reflux flow while another partial feed flow being fed to an evaporator
Implementation Method 3
which in a mechanical compressor unit is compressed to a compressed combined flow
Implementation Method 4
the compressed combined flow that enters a dewatering unit to be split in a water-rich permeate flow and a substantially water free retentate flow
Implementation Method 5
vapour permeation or molecular sieve
Implementation Method 6
the permeate flow subsequently being condensed in a condenser at an underpressure generated by a vacuum system
Implementation Method 7
being charged as a feed flow to the distillation column receiving external thermal energy via a heat exchanger
Data Source
Figure 1
Figure 2
AI summary
Method for dewatering a mixture of mostly ethanol and water which is split into a first partial feed flow (3) that is directed to a distillation column (32) as a reflux flow while a second partial feed flow (4) is directed to an evaporator unit (31) as an evaporator inlet flow and leaves the top of the evaporator unit as an evaporator outlet flow (6). A top discharge flow (7) from distillation column (32) is returned and combined with the evaporator outlet flow (6) to a combined flow (8) at an overpressure and which in a compressor unit (33) is compressed to a combined, compressed flow (10) which enters a dewatering unit (34) in which it is split into a water-rich permeate flow (14) and a retentate flow (11) in the form of substantially water free ethanol. The permeate flow (14) is condensed in a condenser (39) at an underpressure whereafter permeate flow (15) is pressurized by a pump (42) to a flow (16) which is fed to distillation column (32), which is supplied with external thermal energy by a heat exchanger (36), and there split into a water rich bottom discharge flow (18) and an ethanol-rich top discharge flow (7). The retentate flow (11) is used an energy source in a retentate heat exchanger (37) of evaporator unit (31) before leaving as a product flow (12).