Multi-Stage Reverse Osmosis Solvent Recovery
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Solution Overview
Problem
Conventional reverse osmosis processes for solvent recovery from dilute solutions face challenges such as low recovery ratios and membrane scaling due to high pressure requirements, leading to increased energy consumption and environmental impact.
Innovation Solution
A method involving a series of reverse osmosis units with low rejection membranes and a final high rejection membrane, where the concentrate from each unit is recycled back to the permeate side to maintain a small solute concentration differential, reducing pressure gradients and energy consumption, and incorporating additional processes like forward osmosis, nanofiltration, and electrodialysis for enhanced solvent recovery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If higher pressure is applied across the membrane to increase recovery ratio, then solvent recovery efficiency is improved, but membrane scaling and energy consumption increase
Solution Approach 1:
The system divides the reverse osmosis process into multiple stages with progressively higher rejection membranes. Each stage operates at optimized pressure levels, avoiding the need for single-stage high-pressure operation. This segmentation allows the system to achieve high overall recovery ratios while maintaining lower energy consumption at each individual stage.
Solution Approach 2:
The patent changes the rejection parameter of membranes across different stages, using low rejection membranes in early stages and high rejection membranes in later stages. This parameter change allows the system to operate at lower pressures in initial stages, reducing energy consumption while still achieving high overall recovery through the multi-stage process.
2Productivity
If higher pressure is applied across the membrane to increase recovery ratio, then solvent recovery efficiency is improved, but membrane scaling increases
Solution Approach 1:
By segmenting the RO process into multiple stages with progressively higher rejection membranes, the system avoids concentrated solute buildup at high pressure in a single stage. Each stage operates at moderate pressure with appropriate rejection characteristics, preventing the conditions that lead to membrane scaling while achieving high overall recovery.
Solution Approach 2:
Different stages of the system use membranes with locally optimized rejection properties matched to their specific operating conditions. Early stages use low rejection membranes suitable for lower pressure operation, while later stages use high rejection membranes at higher pressures. This local quality optimization prevents scaling in each specific stage while maintaining high overall recovery.
3Manufacturing precision
If high rejection membranes are used to achieve high solute concentration, then purification efficiency is improved, but pressure requirements and power consumption increase
Solution Approach 1:
The purification process is segmented into multiple stages, with high rejection membranes concentrated in the final stages where they are most effective. Earlier stages use lower rejection membranes that operate at lower pressures, reducing overall power consumption while still achieving the desired high purification efficiency in the final product.
Solution Approach 2:
The system performs preliminary concentration and purification in early stages using low rejection membranes at lower pressures, preparing the feed for subsequent high rejection stages. This preliminary action reduces the burden on high rejection membranes, allowing them to operate more efficiently at lower pressures and reducing overall power consumption.
4Quantity of substance
If conventional reverse osmosis is used for dilute solution concentration, then solvent recovery is achieved, but recovery ratio remains low
Solution Approach 1:
The system changes the rejection parameter of membranes across multiple stages, starting with low rejection membranes that are effective for dilute solutions and progressing to high rejection membranes for concentrated solutions. This parameter change strategy enables the system to achieve high recovery ratios from dilute feeds by optimizing membrane selection for each concentration stage.
Solution Approach 2:
Each stage of the multi-stage RO system uses membranes with locally optimized rejection properties matched to the feed concentration and operating pressure of that specific stage. This local quality optimization ensures maximum efficiency at each stage, enabling high overall recovery ratios from dilute solutions that would be difficult to achieve with uniform membrane selection.
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 increases solvent recovery efficiency, reduces energy requirements, and minimizes environmental impact by achieving higher solute concentration with lower pressure and power consumption, while also allowing for the use of less expensive, more porous membranes.
Implementation Method 1
One of the most common technologies used in solvent purification and concentrating dilute solutions is that of reverse osmosis (RO), where a solvent is forced through a permeable membrane from a region of high solute concentration to a region of low solute concentration by applying a pressure greater than osmotic pressure.
Implementation Method 2
where a solvent is forced through a permeable membrane from a region of high solute concentration to a region of low solute concentration by applying a pressure greater than osmotic pressure
Data Source
AI summary
The method of solvent recovery includes using a plurality of solvent recovery units to recover solvent from a dilute solution. The solvent recovery units can include a plurality of reverse osmosis or forward osmosis membrane systems arranged in series. For reverse osmosis, at least some of the concentrate in a last reverse osmosis unit of the series is recycled back to the permeate of that unit to provide a mixed permeate. The mixed permeate is then passed successively to the permeate side of each preceding reverse osmosis unit in the series. For forward osmosis, a draw solution is passed sequentially from the permeate side of each unit to the permeate side of the preceding unit. The draw solution may be prepared by concentrating part of the concentrate stream by evaporation and recycling it back as a draw solution.