RO Membrane Permeate Flow Restrictors for Pressure Uniformity
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Solution Overview
Problem
Reverse osmosis systems face inefficiencies in permeate production due to varying osmotic pressures along membrane arrays, leading to uneven net driving pressures and reduced permeate recovery, as well as issues with polarization and fouling caused by uneven flow velocities.
Innovation Solution
The implementation of a multi-element membrane array with connectors that include flow restrictors to regulate permeate pressure, maintaining a consistent net driving pressure across elements by progressively reducing permeate pressure downstream, and using adjustable orifice plugs to optimize fluid flow through each connector.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional membrane arrays without flow restrictors are used, then the system structure is simple, but permeate pressure varies significantly across elements leading to uneven net driving pressure and reduced permeate recovery
Solution Approach 1:
The membrane array is segmented into multiple elements with individual flow restrictors in each permeate line. This segmentation allows independent control of permeate flow for each element, enabling uniform net driving pressure distribution across all elements and improving overall permeate recovery
Solution Approach 2:
Flow restrictors are installed locally in each permeate line at different positions along the membrane array. Each restrictor is specifically sized to compensate for the local osmotic pressure conditions at that position, creating locally optimized flow conditions that result in uniform permeate production across the entire array
2Productivity
If uniform permeate pressure is maintained across all elements, then net driving pressure becomes uneven due to varying osmotic pressures, but if no pressure control is applied, then permeate production becomes uneven
Solution Approach 1:
The flow restrictors are designed with specific flow coefficients that change along the array position. Restrictors at downstream positions have higher flow coefficients to compensate for higher osmotic pressures, while upstream restrictors have lower coefficients. This parameter variation ensures uniform net driving pressure and permeate production across all elements
3Productivity
If high permeate flow is allowed through all elements, then permeate recovery increases, but polarization and fouling increase due to uneven flow velocities
Solution Approach 1:
The flow restrictors create a feedback mechanism where the permeate flow rate through each element is automatically regulated by the local osmotic pressure conditions and the restrictor characteristics. This feedback control maintains optimal flow velocities that prevent polarization and fouling while maximizing permeate recovery
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 ensures uniform permeate production across the membrane array, enhances permeate recovery, and reduces fouling by maintaining optimal flux rates and pressure distribution, thereby improving the overall efficiency of the reverse osmosis process.
Implementation Method 1
Each of the plurality of connectors includes one of a plurality of flow restrictors. Each of the plurality of flow restrictors is sized to further restrict permeate flow into a subsequent permeate pipe
Implementation Method 2
The desalination reverse osmosis membranes receive feed fluid from brackish or sea water and extract fresh water therefrom. Fresh water is extracted or separated when the pressure of the feed fluid exceeds the osmotic pressure of the fluid which allows permeate or product fluid to cross the semi-permeable reverse osmosis membrane
Implementation Method 3
The pressure required to produce fresh water is proportional to the concentration of the total dissolved solids (TDS) in the feed solution within the reverse osmosis housing. For typical ocean water, the concentration is about 35,000 parts per million (ppm) and the corresponding osmotic pressure is about 450 pounds per square inch (psi)
Data Source
AI summary
A reverse osmosis system includes a multi-element membrane array having membrane elements disposed in series. Permeate pipes receive permeate from respective membrane elements. The connectors coupling the permeate pipes have a flow restrictor. The restrictors have an effective area that increases in subsequent connectors. The body has an outer wall and an orifice plug within a longitudinal passage. The orifice plug is separated from the body. Each orifice plug has a carrier body with a plug passage therethrough. Each carrier body has an orifice plate having an orifice disposed within the plug passage and a spring disposed within the carrier body resisting movement of the orifice plate, whereby movement of the orifice plate changes an amount of fluid flowing through each connector. Each spring in subsequent connectors provides a reduced amount of spring force for resisting movement of the orifice plate.