Hollow Fiber Membrane Element with Double-Layer Structure for Forward Osmosis
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Solution Overview
Problem
In forward osmosis water treatment, the existing hollow fiber membrane modules face challenges in enhancing water recovery rates while minimizing scale adhesion to membranes when the draw solution flows outside and the feed solution flows inside, leading to increased energy requirements and costs due to the need for higher feed solution flow rates to prevent scale formation.
Innovation Solution
A hollow fiber membrane element with a double-layer structure, where the first layer has a lower permeability coefficient than the second layer, is designed to reduce the minimum feed solution flow rate required, incorporating a core tube with a plurality of pores and hollow fiber membranes spirally wound in a crisscross fashion, with resin walls securing both ends, to minimize scale adhesion and enhance water recovery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the feed solution flow rate is increased to prevent scale formation, then scale adhesion is reduced, but the water recovery rate decreases and energy consumption increases
Solution Approach 1:
The patent applies local quality by creating different flow conditions in different regions of the hollow fiber membrane. The spiral winding configuration generates varying flow velocities along the membrane surface, with higher velocity near the inlet and lower velocity toward the outlet. This localized flow variation prevents scale formation in high-risk areas without requiring uniformly high flow rates throughout, thereby reducing overall energy consumption while still preventing scale adhesion.
Solution Approach 2:
The patent employs dynamics by utilizing the natural flow dynamics of the feed solution as it moves through the hollow fiber membranes. The spiral winding creates a dynamic flow pattern where the flow rate and velocity change along the length of the membrane element. This dynamic flow configuration automatically provides higher shear stress at the inlet where scale formation is most likely, without requiring constant high-energy input throughout the entire system.
2Object-affected harmful factors
If the feed solution flow rate is increased to prevent scale formation, then scale adhesion is reduced, but the water recovery rate decreases
Solution Approach 1:
The spiral winding configuration creates local variations in flow characteristics along the membrane surface. By concentrating higher flow velocities in regions most susceptible to scale formation (near the inlet), the system effectively prevents scale adhesion in these critical zones without requiring uniformly high flow rates across the entire membrane area, thus maintaining higher overall water recovery rates.
Solution Approach 2:
The dynamic flow pattern generated by spiral winding allows the system to adapt flow distribution to the actual scale formation risks at different locations. The naturally decreasing flow rate along the membrane length matches the decreasing scale formation risk, optimizing both scale prevention and water recovery efficiency without unnecessary energy expenditure.
3Object-affected harmful factors
If the draw solution is flowed outside the hollow fiber membranes, then scale adhesion is reduced, but the draw solution becomes diluted and requires higher flow rates to maintain concentration
Solution Approach 1:
The patent applies local quality by positioning the draw solution flow path outside the hollow fiber membranes, creating a localized high-concentration environment at the membrane surface where scale formation is most likely. This external draw solution configuration maintains high osmotic pressure gradients at the critical interface without requiring the draw solution to traverse the entire membrane length, thereby preventing dilution while still reducing scale adhesion.
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 configuration reduces the likelihood of scale adhesion, lowers the minimum feed solution flow rate, and enhances the water recovery rate, thereby reducing capital and operating expenses while maintaining efficient water treatment.
Implementation Method 1
Forward osmosis water treatment is a known technique which uses the forward osmosis phenomenon to recover fresh water from a treatment-target liquid (a feed solution) such as sea water, river water, or wastewater. Forward osmosis is a phenomenon in which water contained in a feed solution (FS), which has a lower concentration, permeates through a membrane to move toward a draw solution (DS), which has a higher concentration (a higher osmotic pressure).
Implementation Method 2
a core tube comprising a side face having a plurality of pores
Data Source
AI summary
A hollow fiber membrane element, comprising: a core tube comprising a side face having a plurality of pores; and a hollow fiber membrane group consisting of a plurality of hollow fiber membranes disposed around the core tube, the hollow fiber membrane element being a both open-ended type hollow fiber membrane element in which both ends of the core tube and the plurality of hollow fiber membranes are open. The hollow fiber membrane group includes a first hollow fiber membrane layer composed of a plurality of first hollow fiber membranes disposed so as to surround the core tube and a second hollow fiber membrane layer composed of a plurality of second hollow fiber membranes disposed so as to surround the first hollow fiber membrane layer, and a permeability coefficient of the plurality of first hollow fiber membranes is smaller than a permeability coefficient of the plurality of second hollow fiber membranes.