Membrane Separation Stage Segmentation for Deionization Conductivity
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Solution Overview
Problem
Conventional water treatment methods for producing ultrapure water are complex, particularly in the deionization stage, where high ionic conductivity in concentrate chambers is often achieved by adding neutral salts or recirculating concentrate, and the permeate from membrane separation stages cannot be directly transferred due to high electrical conductivity.
Innovation Solution
The method separates the water flow into a concentrate flow and multiple permeate flows of different electrical conductivity in the membrane separation stage, with the low-salt permeate fed to the diluate side and high-salt permeate to the concentrate side of the deionization device, using a combination of reverse osmosis and nanofiltration modules to generate permeate streams for efficient deionization without additional salt addition or recirculation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional deionization methods are used with single-stage membrane separation, then the process is simpler, but additional equipment is required for salt addition and recirculation to maintain adequate conductivity in concentrate chambers
Solution Approach 1:
The permeate stream from membrane separation is segmented into multiple streams with different electrical conductivities by using multiple membrane modules with different rejection characteristics. These segmented streams are then selectively fed to different chambers (diluate chamber and concentrate chamber) to eliminate the need for additional salt addition equipment and recirculation systems.
Solution Approach 2:
Different portions of the permeate stream are assigned different qualities (electrical conductivities) based on their source membrane module characteristics. The low-salt permeate is directed to the diluate chamber while high-salt permeate is directed to the concentrate chamber, allowing each chamber to receive appropriately quality-matched feed without requiring external conductivity adjustment equipment.
2Productivity
If permeate from membrane separation is directly transferred to deionization, then the process is more efficient, but the high electrical conductivity of the permeate prevents direct transfer
Solution Approach 1:
The single permeate stream is segmented into multiple streams with different electrical conductivities. This segmentation allows the system to utilize the entire permeate flow productively - the low-conductivity portion can be directly transferred to the deionization unit's diluate chamber, maximizing water yield while ensuring transfer feasibility.
Solution Approach 2:
The electrical conductivity parameter of the permeate stream is varied across different membrane modules due to their different rejection characteristics. By exploiting this parameter variation, the system transforms the previously problematic high-conductivity permeate into a useful resource that can be fed to the concentrate chamber, thereby enabling direct transfer of all permeate without compromising deionization efficiency.
3Adaptability or versatility
If multiple membrane modules with different rejection characteristics are used, then permeate streams of different conductivity are generated, but the membrane separation device structure becomes more complex
Solution Approach 1:
Multiple membrane modules with different rejection characteristics are merged into a single integrated membrane separation device housed in one pressure vessel. This combining approach enables the generation of multiple permeate streams with different conductivities while avoiding the complexity of multiple separate devices, as all modules share common infrastructure (pressure vessel, inlet, and outlet connections).
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 simplifies the deionization stage by maintaining adequate conductivity in concentrate chambers without additional equipment, increasing water yield by recycling concentrate and allowing for the same pressure housing construction of the membrane separation device, while generating permeate streams with varying conductivity for effective deionization.
Implementation Method 1
a first stage in which raw water is softened and/or partially desalinated
Implementation Method 2
Suitable membrane separation methods include reverse osmosis and nanofiltration, possibly in combination
Implementation Method 3
a third stage in which the water is ultimately and essentially completely deionized, for example, by electrodeionization
Data Source
Figure 1
AI summary
What is described is a multistage process for treating water, in which a water stream is purified in a membrane separation stage and a deionization unit which is connected downstream thereof and has at least one concentrate chamber and at least one diluent chamber, wherein the water stream is separated in the membrane separation apparatus into a concentrate stream and at least two permeate streams of different electrical conductivity, and wherein at least the permeate stream with the highest electrical conductivity is fed at least partly into the at the one concentrate chamber and at least the permeate stream with the lowest electrical conductivity at least partly into the at least one diluent chamber of the downstream deionization unit. Additionally described is a membrane separation apparatus which is configured such that at least two permeate streams with different electrical conductivities can be obtained therein, as is a water treatment plant comprising at least one such membrane separation apparatus and at least one deionization unit with at least one concentrate chamber and at least one diluent chamber.