Direct Solvent Contact Crystallization for Zero-Liquid Discharge Desalination
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Solution Overview
Problem
Conventional zero-liquid discharge (ZLD) desalination processes are energy-intensive due to thermodynamic limits and require high energy for the final stages of salt crystallization, while solvent-based methods face challenges in efficiently separating water from salt solutions without incurring energy penalties.
Innovation Solution
The direct solvent contact crystallization (DSCC) process involves a three-stage method where water is selectively absorbed into a solvent, then separated using a recovery agent, allowing for efficient water recovery with minimal heat penalty and energy use, replacing the energy-intensive portions of traditional ZLD treatment trains.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If conventional thermal separation processes are used to separate water from salt solutions, then water can be recovered, but energy consumption is high due to thermodynamic limits and large heat penalty for phase change
Solution Approach 1:
The patent introduces a solvent as an intermediary substance that selectively binds to water in the brine solution, forming a solvent-water complex. This mediator enables water separation from salt without direct thermal heating, avoiding the large heat penalty of conventional evaporation. The solvent acts as a bridge that facilitates water extraction through molecular interactions rather than thermal energy input.
Solution Approach 2:
The patent changes the separation mechanism from thermal-based to chemistry-based by utilizing temperature-swing solvent extraction (TSSE). Instead of maintaining high temperatures for evaporation, the system uses temperature cycles to control solvent-water binding and release. The solvent binds water at lower temperatures and releases it at higher temperatures, enabling separation with much smaller heat input compared to conventional evaporation.
2Use of energy by moving object
If solvent-based methods are used to extract water from brine, then energy penalty is reduced, but efficient separation of water from salt solutions remains challenging
Solution Approach 1:
The patent employs a specifically designed solvent as an intermediary that selectively interacts with water molecules through hydrogen bonding and other molecular forces. This solvent mediates the separation process by forming a complex with water that excludes salt ions, achieving reliable water-salt separation. The solvent's molecular structure is optimized to preferentially bind water over salt, ensuring high separation efficiency.
Solution Approach 2:
The patent utilizes temperature as a control parameter to regulate the solvent-water-salt equilibrium. By cycling the temperature, the system transitions between states where the solvent preferentially binds water (at lower temperatures) and where water is released (at higher temperatures). This parameter change enables controlled, efficient separation that maintains reliability while reducing energy input compared to constant high-temperature evaporation.
3Productivity
If multi-stage processes are implemented to treat brine to ZLD, then water recovery is achieved, but the later stages require much of the total energy for the process
Solution Approach 1:
The patent introduces a solvent intermediary that enables water extraction from concentrated brine without requiring the high-energy thermal processes typical of later-stage ZLD treatment. The solvent selectively binds water even from highly concentrated salt solutions, allowing water recovery from stages that would otherwise require intensive heating. This mediator effect reduces the energy burden across all treatment stages.
Solution Approach 2:
The patent applies temperature-swing extraction throughout the multi-stage process, replacing conventional thermal evaporation with a chemistry-based separation mechanism. By using temperature cycles to control solvent-water binding rather than maintaining high temperatures, the system achieves water recovery in all stages with significantly reduced energy input, particularly in the later stages where conventional processes are most energy-intensive.
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
DSCC processes achieve efficient water recovery from brines with reduced energy consumption by utilizing a solvent and recovery agent, effectively treating naturally concentrated or pre-concentrated brines to produce freshwater and solid salts, outperforming conventional thermal separation processes.
Implementation Method 1
water is selectively absorbed from brine into a non-volatile solvent system
Implementation Method 2
a volatile hydrophobic recovery agent is added to the solvent-water mixture, releasing the freshwater product
Implementation Method 3
the solvent-recovery agent mixture is transferred to separation process, where the pure solvent and recovery agent can be recovered
Data Source
AI summary
Provided are direct solvent contact crystallization devices and methods. A direct solvent contact crystallization device can comprises a first liquid-liquid separator comprising an inlet stream comprising 10-35 wt. % salt and a first outlet stream comprising water and a solvent; a second liquid-liquid separator comprising an inlet stream comprising the first outlet stream of the first liquid-liquid separator and a first outlet stream comprising 95 wt. % or greater water; and a separation unit comprising an inlet stream comprising a second outlet stream of the second liquid-liquid separator, a first outlet stream comprising the solvent, and a second outlet stream comprising a recovery agent, wherein the inlet stream of the first liquid-liquid separator comprises the first outlet stream of the separation unit, and the inlet stream of the second liquid-liquid separator comprises the second outlet stream of the separation unit.