Nanofiltration Membrane for Seawater Scale Prevention
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Solution Overview
Problem
Scale formation, particularly non-alkaline scale caused by calcium and magnesium sulfate precipitation, hampers the efficiency and increases energy and maintenance costs in thermal desalination processes like Multi-Stage Flash Distillation, which are not effectively addressed by existing methods.
Innovation Solution
A nanofiltration membrane system with a molecular weight cut-off value greater than 300 Dalton, integrated into a forward osmosis process with a pressure-assisted configuration, is used to separate seawater from a draw solution, achieving high rejection rates of magnesium and calcium sulfate ions and reducing scale formation in thermal desalination units.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional forward osmosis membranes are used, then ion rejection is achieved, but water flux is low and cost is high
Solution Approach 1:
The patent changes the key parameter of membrane molecular weight cut-off from typical FO membrane values (300-1000 Dalton) to a specific range (500-1000 Dalton), which optimizes the balance between water flux and ion rejection. This parameter change enables the nanofiltration membrane to achieve both high water flux and effective rejection of magnesium and calcium sulfate ions that cause scale formation.
Solution Approach 2:
The patent employs a composite membrane structure consisting of a nanofiltration active layer on a porous support layer. This composite design combines the selective ion rejection properties of nanofiltration materials with the mechanical strength and water permeability of the support structure, achieving both high water flux and effective scale ion rejection simultaneously.
2Use of energy by stationary object
If scale formation is not addressed, then thermal desalination process operates, but energy consumption and maintenance cost increase
Solution Approach 1:
The patent applies preliminary action by removing scale-forming ions (magnesium and calcium sulfate) from the feed water before the thermal desalination process begins. The nanofiltration membrane pre-treats the seawater to reject these ions, preventing scale formation on heat transfer surfaces during subsequent thermal processing, thereby avoiding increased energy consumption and maintenance costs.
Solution Approach 2:
The patent implements preliminary anti-action by using the nanofiltration membrane to proactively counteract scale formation. The membrane selectively rejects magnesium and calcium sulfate ions that would otherwise precipitate and form scales on thermal processing equipment, thereby preventing the harmful effects of scale before they occur.
3Productivity
If nanofiltration membrane with higher molecular weight cut-off is used, then water flux increases, but ion rejection may decrease
Solution Approach 1:
The patent optimizes the molecular weight cut-off parameter to a specific range (500-1000 Dalton) that balances water flux and ion rejection. This precise parameter selection allows the membrane to maintain sufficient water permeability while effectively rejecting scale-forming ions with specific sizes, achieving both high productivity and effective ion removal.
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
The nanofiltration membrane system significantly enhances water flux and ion rejection, reducing energy consumption and maintenance costs by effectively addressing scale issues in thermal desalination processes, while being more cost-effective than traditional forward osmosis membranes.
Implementation Method 1
a nanofiltration membrane system with a molecular weight cut-off value greater than 300 Dalton, integrated into a forward osmosis process
Implementation Method 2
The membrane has an active layer and a support layer provided on the active layer, and the membrane includes a nanofiltration membrane
Data Source
AI summary
A method, apparatus and system for seawater treatment are provided. The apparatus for seawater treatment includes a first chamber that is in fluid communication with a feed solution, a second chamber that is in fluid communication with a draw solution, and a membrane that separates the first chamber from the second chamber. The membrane has an active layer and a support layer provided on the active layer, and the membrane includes a nanofiltration membrane.