Forward Osmosis Draw Agent Recovery via Vapour-Liquid Separator
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Solution Overview
Problem
Existing forward osmosis processes require significant external energy input, particularly for compressing recovered draw agents, leading to energy inefficiencies and increased operational costs.
Innovation Solution
A method and apparatus that recover draw agents by separating and condensing draw agent vapour using a vapour-liquid separator, eliminating the need for compressors and maintaining elevated fluid pressure within the draw agent circuit, allowing for direct recirculation of the draw agent without recompression.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a compressor is used to repressurise the DME after depressurisation, then the draw agent can be recovered and reused, but energy consumption increases and device complexity increases
Solution Approach 1:
The invention changes the pressure parameter of the draw solution to maintain elevated pressure throughout the system, eliminating the need for compression. By keeping the draw solution under constant pressure from the membrane module outlet through the separator and back to the membrane module inlet, the system avoids energy-intensive compression while still achieving effective draw agent recovery and reuse.
Solution Approach 2:
The invention replaces the mechanical compressor system with a pressure-maintaining flow path. Instead of using a compressor to repressurise the draw agent after depressurisation, the system uses a continuously pressurised flow path that maintains elevated pressure through the separator and recirculation line, substituting mechanical compression with a simpler pressure-maintenance approach.
2Ease of operation
If the draw solution fluid circuit is split into high pressure and low pressure portions, then the draw agent recovery function can be performed, but energy is lost due to incomplete pressure exchange efficiency
Solution Approach 1:
The invention merges the high-pressure draw solution flow path with the recirculation system by maintaining elevated pressure throughout the entire circuit. The draw solution exits the membrane module at elevated pressure, passes through the separator without pressure loss, and returns to the membrane module inlet still under pressure, creating a unified high-pressure loop that eliminates energy loss from pressure exchange.
3Use of energy by moving object
If a vapour-liquid separator is used to separate draw agent vapour and solvent, then draw agent recovery is achieved without compressor, but additional equipment is required
Solution Approach 1:
The invention utilizes phase transitions of the draw agent to enable separation without compression. By maintaining elevated pressure and temperature conditions, the draw agent remains in a supercritical or gaseous state that allows it to be separated from the liquid solvent in the vapour-liquid separator, then condensed and recirculated. This phase-based separation avoids the need for compressors while achieving effective draw agent 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 enhances energy efficiency by avoiding the need for compressor-driven recompression, reducing energy consumption, and optimizing the reuse of draw agents in the forward osmosis process, thereby improving the overall efficiency and sustainability of water purification and desalination processes.
Implementation Method 1
using the vapour-liquid separator to separate draw agent vapour and solvent
Implementation Method 2
condensing draw agent vapour
Implementation Method 3
Forward osmosis utilises a semi-permeable membrane positioned between feed water containing dissolved solutes, for example waste-water or sea-water, and a draw solution
Data Source
AI summary
A method of recovering draw agent utilised in a forward osmosis membrane cell, the method comprising the steps of passing diluted draw agent to a vapour-liquid separator; using the vapour-liquid separator to separate draw agent vapour and solvent; and condensing draw agent vapour.