Retrograde Soluble Polymer Draw Solute Recovery in Forward Osmosis
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Solution Overview
Problem
Current forward osmosis desalination methods are inefficient in purifying contaminated water as they do not effectively separate solutes from water, relying on temperature-dependent solubility and requiring additional steps like distillation or semi-batch recovery, which are energy-intensive and complex.
Innovation Solution
A process using retrograde soluble polymer draw solutes that decrease solubility with temperature, allowing for phase separation and subsequent agglomeration, followed by filtration to produce purified water, with a system comprising a semipermeable membrane, heat exchangers, coalescers, and nanofilters to achieve efficient solute separation and recovery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If temperature-dependent solubility is used for solute separation, then solute separation is achieved, but additional energy-intensive steps like distillation are required
Solution Approach 1:
The patent utilizes the phase transition of retrograde soluble polymers from dissolved state to precipitated state by temperature increase. The draw solute undergoes phase separation at elevated temperatures, allowing gravitational separation without requiring distillation or other energy-intensive processes. This phase transition-based separation resolves the contradiction by achieving solute separation while minimizing energy consumption.
2Quantity of substance
If retrograde soluble polymer draw solutes are used, then phase separation is achieved, but complex equipment like nanofilters and coalescers are required
Solution Approach 1:
The patent segments the solute separation process into distinct functional zones: a draw side for phase separation and a feed side for water purification. By dividing the membrane module into these functional segments and using retrograde soluble polymers that naturally separate phases, the system achieves effective separation without requiring complex nanofilters or coalescers, thus reducing overall equipment complexity.
Solution Approach 2:
The retrograde soluble polymer acts as an intermediary substance that facilitates phase separation. These polymers undergo temperature-dependent phase transitions, serving as a mediator between the draw solution and the separation process. This intermediary mechanism enables gravitational separation without complex equipment, resolving the contradiction between phase separation effectiveness and equipment simplicity.
3Productivity
If continuous operation is implemented, then productivity is improved, but maintaining high water flux and recovery rates becomes challenging
Solution Approach 1:
The patent implements continuous operation by continuously circulating the draw solution through the membrane module and continuously removing precipitated polymer. The system maintains continuous water flux through the membrane while the draw solution is continuously regenerated via temperature-induced phase separation. This continuous circulation and separation process sustains high productivity without compromising water flux or recovery rates.
Solution Approach 2:
The patent utilizes parameter changes, specifically temperature variation, to maintain continuous operation with high water flux. By periodically or continuously adjusting the temperature of the draw solution, the system controls the phase separation of retrograde soluble polymers, ensuring continuous regeneration of the draw solution while maintaining high water flux and recovery rates throughout operation.
Data Source
AI summary
Improved systems and processes for forward osmosis water purification or desalination are herein disclosed. According to one embodiment a process for purifying contaminated water is provided wherein a contaminated feed solution stream comprising water and with a first osmotic pressure is passed through a semipermeable membrane to a draw side having a draw solution stream with a second osmotic pressure on a draw side of the semipermeable membrane. The diluted draw solution stream is heated, agglomerated and cooled to produce a cooled single phase water rich stream that is purified to produce a water product stream.