Multi-Stage Nanofiltration System for Solute Recovery
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Solution Overview
Problem
Nanofiltration systems with a single type of membrane experience low permeate recovery and require undesirable operating conditions when dealing with high concentrations of solutes, such as sulfate, necessitating high pressures to achieve desired concentration levels in retentate for zero liquid discharge processes.
Innovation Solution
A multi-stage nanofiltration system is implemented, where downstream stages are more permissive to solutes than upstream stages, allowing for increased solute permeation and reducing the need for high pressures, by using nanofiltration stages in series with varying permeability, each stage being more permeable to the solute than the previous one.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single type of nanofiltration membrane is used, then the system structure is simple, but the permeate recovery is low and high operating pressure is required
Solution Approach 1:
The nanofiltration system is divided into multiple stages, each with membranes of different permeability characteristics. The first stage uses a less permissive membrane for initial concentration, while subsequent stages use progressively more permissive membranes, allowing each stage to operate optimally and achieve high overall recovery without excessive pressure requirements.
Solution Approach 2:
Different membrane types are assigned to different stages based on local requirements. Upstream stages handle high-concentration feed with less permissive membranes, while downstream stages handle concentrated retentate with more permissive membranes, optimizing performance at each location in the system.
2Ease of manufacture
If a single type of nanofiltration membrane is used, then the membrane selection is simple, but high operating pressure is required to achieve desired concentration
Solution Approach 1:
The concentration process is segmented into multiple stages with progressively more permissive membranes. This segmentation allows the system to achieve high retentate concentration through cumulative effect rather than requiring a single high-pressure stage, reducing peak pressure requirements while maintaining manufacturing simplicity.
Solution Approach 2:
The system changes the permeability parameter of membranes across stages. By using a series of membranes with increasing permeability from upstream to downstream, the system achieves the desired concentration effect through parameter variation rather than increasing pressure, simplifying the overall pressure management while maintaining effective concentration.
3Productivity
If downstream stages are more permissive to solute than upstream stages, then solute recovery is enhanced and operational pressure is reduced, but the system complexity increases
Solution Approach 1:
The system is segmented into multiple nanofiltration stages arranged in series, with each stage containing membranes of specific permeability. This segmentation enables enhanced solute recovery through cumulative concentration while distributing the complexity across manageable modular units rather than a single complex system.
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 enhances solute recovery and reduces operational pressures, achieving higher concentration of solutes in retentate while maintaining energy efficiency and simplifying the process, as demonstrated by modeled and tested systems with specific solutes like sulfate and ferrous sulfate.
Implementation Method 1
Nanofiltration uses membranes with nanometer-sized pores. Nanofiltration membranes have pore sizes that are smaller than microfiltration and ultrafiltration membranes, but larger reverse osmosis membranes. Nanofiltration membranes may have pores with pore sizes from 1-10 nanometers.
Implementation Method 2
Membrane separation processes concentrate a solute in an aqueous solution by the application of a positive pressure to one side of a filtration membrane.
Data Source
AI summary
A multistage nanofiltration (NF) system for filtering a solute from a feed solution where a downstream NF stage is more permissive to the solute than an upstream NF stage. In some examples. the nanofiltration system includes a plurality of nanofiltration stages in series, where each nanofiltration stage is more permissive to the solute than the nanofiltration stage that is immediately upstream.