Batch Pressure-Driven Membrane Separation with Variable Reservoir
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Solution Overview
Problem
Current reverse osmosis (RO) desalination processes face inefficiencies in energy consumption and membrane fouling, particularly in batch and semi-batch systems, which limit their ability to achieve high recovery rates and maintain permeate quality due to entropy generation and discrete cycle modeling.
Innovation Solution
Implementing a time-variant batch pressure-driven membrane separation system with a variable-volume reservoir and pressure recovery device, where the feed is continuously recirculated and pressure is increased over time to counteract osmotic pressure, reducing mixing of streams and minimizing fouling through osmotic backwashing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If continuous RO is used to maintain permeate quality, then consistent separation performance is achieved, but energy consumption increases due to pressure being set above maximum osmotic pressure throughout
Solution Approach 1:
The patent implements dynamic pressure adjustment in batch RO systems, where pressure is increased over time to counteract increasing osmotic pressure as feed is concentrated. This temporal variation in operating pressure allows the system to maintain effective separation while operating closer to instantaneous osmotic pressure rather than continuously above maximum osmotic pressure, thereby reducing energy consumption while preserving permeate quality
Solution Approach 2:
The batch RO process operates in cyclic batches with periodic pressure increases, allowing the system to reset between cycles by refilling with fresh feed. This periodic operation enables the system to maintain high recovery rates while managing energy consumption through controlled pressure variation over time rather than continuous high-pressure operation
2Productivity
If CCRO mixes brine with incoming feed continuously to achieve high recovery, then recovery rate increases, but entropy generation increases and efficiency decreases
Solution Approach 1:
The patent extracts the brine mixing function from the continuous feed stream in batch RO systems. Instead of continuously mixing brine with incoming feed as in CCRO, the batch system concentrates feed to high recovery rates and then completely refills with fresh feed between batches. This separation of concentration and refilling operations eliminates continuous entropy-generating mixing while maintaining high recovery rates
Solution Approach 2:
The batch RO system maintains continuous useful action through rapid cycling between concentration and refilling phases. The system operates continuously by immediately refilling with fresh feed after reaching target recovery, eliminating idle time while avoiding the entropy-generating continuous mixing of CCRO. This approach sustains high productivity without the efficiency penalties of brine-feed mixing
3Use of energy by moving object
If batch RO recirculates brine without fresh feed to achieve high recovery, then energy efficiency improves, but permeate quality maintenance becomes difficult
Solution Approach 1:
The batch RO system employs periodic refilling with fresh feed between concentration cycles to reset the system state. This periodic action prevents the progressive quality degradation that would occur with continuous brine recirculation alone, while maintaining energy efficiency during the concentration phase. The system achieves both goals by separating the concentration operation (energy-efficient brine recirculation) from the quality reset operation (periodic fresh feed addition)
4Productivity
If pressure is increased over time in batch RO to counteract osmotic pressure, then recovery rate increases, but system complexity increases with variable-volume reservoir and pressure recovery device
Solution Approach 1:
The patent merges the pressure recovery function with the reservoir system in batch RO. The variable-volume reservoir and pressure recovery device are integrated into a unified system where the reservoir itself facilitates pressure management during batch operation. This integration reduces overall system complexity by combining multiple functions into a coordinated subsystem rather than adding separate independent components
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 enhances energy efficiency, reduces capital costs, and achieves higher recovery rates with lower fouling resistance, enabling more effective desalination and concentration processes while minimizing environmental impact.
Implementation Method 1
wherein the membrane passes at least partially purified solvent (permeate) as filtrate to a permeate (downstream) side of the membrane while diverting at least a portion of the impurity in a retentate on the retentate (upstream) side of the membrane
Implementation Method 2
Batch reverse osmosis technologies are configurations that vary their salinity over time by recycling brine
Implementation Method 3
the pressure applied to the feed in the reservoir is increased to balance against an increasing difference in osmotic pressure across the membrane as the feed increases in osmotic pressure
Implementation Method 4
minimizing fouling through osmotic backwashing
Data Source
AI summary
A feed of at least one of (a) a source liquid including a solvent with a dissolved impurity and (b) a retentate of the source liquid is pumped in a substantially closed loop through a liquid-separation module. The liquid-separation module includes a membrane that passes at least partially purified solvent to a permeate side of the membrane while diverting the impurity in a retentate on the retentate side of the membrane. The purified solvent is extracted from the permeate side of the membrane; and the retentate from the liquid-separation module is pumped to or through a pressurized reservoir with a variable volume for the feed component and recirculated as a component of the feed. Over time, the volume for the feed is reduced and the pressure applied to the feed in the reservoir is increased to balance against an increasing difference in osmotic pressure across the membrane.