Cross-Current Osmotically Assisted Reverse Osmosis for High Solute Concentration
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Solution Overview
Problem
Existing reverse osmosis processes are complex, energy-intensive, and often require high operational pressures, making them inefficient for purifying liquids with high and low solute concentrations.
Innovation Solution
The implementation of a partially cascading cross-current reverse osmosis system, which includes an initial osmotically assisted reverse osmosis stage, an intermediate section with multiple osmotically assisted reverse osmosis stages, and a final reverse osmosis stage, allows for reduced osmotic pressure differential, efficient purification of high-solute concentration solutions, and operation at lower pressures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If higher driving pressure is applied to achieve increased solvent separation, then separation efficiency is improved, but operational feasibility deteriorates due to pressure limitations of osmotic membranes
Solution Approach 1:
The reverse osmosis system is divided into multiple stages with progressively increasing operating pressures. Each stage operates at a manageable pressure level that does not exceed membrane limitations, while the cumulative effect of multiple stages achieves the high solvent separation efficiency that would require excessive pressure in a single stage.
2Productivity
If multiple interstage pumps, valves, bypasses and plumbing are used to mix streams of similar concentrations, then process efficiency is improved, but system complexity increases
Solution Approach 1:
The patent combines the concentrate stream from one reverse osmosis stage with the feed stream of the next stage, creating a integrated flow path that eliminates the need for separate mixing systems with multiple pumps, valves, and bypasses. This merging approach maintains process efficiency by ensuring proper concentration gradients while significantly reducing system complexity.
3Manufacturing precision
If traditional reverse osmosis processes are used for purifying liquids with high solute concentrations, then purification capability is achieved, but energy consumption increases
Solution Approach 1:
The system changes the operating parameters of reverse osmosis by using multiple stages with progressively increasing pressures and by optimizing the concentration gradients between stages. This allows efficient purification of high-solute concentration liquids while reducing overall energy consumption compared to traditional single-stage or high-pressure reverse osmosis processes.
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 system achieves similar separation efficiencies to conventional arrangements while reducing energy consumption and operational complexity, enabling the purification of liquids with high solute concentrations at lower pressures.
Implementation Method 1
An osmotic membrane is semi-permeable barrier which allows smaller molecules (usually solvent molecules such as water) to pass through while blocking the passage of relatively larger molecules or ions (e.g. solutes dissolved in the solvent)
Implementation Method 2
Reverse osmosis ('RO') is the process of applying pressure to the side of the osmotic membrane containing the higher solute concentration in excess of the osmotic pressure, which serves to drive the osmotic process in reverse, i.e. drives solvent through the osmotic membrane to the side with a lower solute concentration
Data Source
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AI summary
Systems and processes for purifying and concentrating a liquid feed stream are disclosed. In the systems, the concentrated liquid output from the high pressure side of a reverse osmosis stage is used as the draw solution in the low pressure side of the reverse osmosis stage in a configuration called osmotically assisted reverse osmosis. This reduces the osmotic pressure differential across the membrane, permitting high solute concentrations to be obtained, hastening the purification of the liquid. Reduced system pressures are also obtained by arranging multiple osmotically assisted reverse osmosis stages in a cross-current arrangement. Overall system energy consumption is reduced compared to conventional thermal processes for high concentration streams.