Multi-Stage Distillation for Forward Osmosis Draw Solution Recovery
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Solution Overview
Problem
Current seawater and brackish water desalination technologies face high energy costs, significant environmental impacts from brine discharge, and high long-term equipment replacement costs, with membrane performance ratios in ammonia-carbon dioxide forward osmosis (FO) processes limited by internal concentration polarization and inefficient heat use in single distillation column recovery processes.
Innovation Solution
Implementing a plurality of distillation columns in conjunction with higher temperature heat sources to improve heat efficiency and reduce energy consumption in the FO desalination process, where vaporized draw solution from one column is used as thermal energy for subsequent columns to enhance solute separation and solvent recovery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a single distillation column is used for solute recovery in FO processes, then the device complexity is low, but the heat efficiency is insufficient and energy consumption is high
Solution Approach 1:
The single distillation column is segmented into multiple columns operating at different temperature stages. The first column operates at higher temperature for initial vaporization, while subsequent columns operate at progressively lower temperatures to recover remaining solutes, thereby improving overall heat efficiency and reducing energy loss.
Solution Approach 2:
The distillation columns are arranged in a nested configuration where the vapor outlet of one column is connected to the vapor inlet of the next column. This nesting allows the vapor stream from one stage to be utilized in the next stage, maximizing heat recovery and minimizing energy loss.
2Use of energy by moving object
If higher temperature heat sources are used in multi-stage distillation, then energy consumption is reduced, but the device complexity increases
Solution Approach 1:
The system utilizes parameter changes by operating each distillation column at different temperature and pressure conditions. The first column uses higher temperature heat sources for efficient vaporization, while subsequent columns operate at progressively lower temperatures, optimizing energy utilization across stages and reducing overall energy consumption.
Solution Approach 2:
The multi-stage distillation system maintains continuous useful action by ensuring that vapor from one column continuously feeds into the next column. This continuous flow of vapor and liquid streams ensures that heat energy is continuously utilized across all stages, maximizing energy efficiency and reducing waste.
3Productivity
If multiple distillation columns are implemented, then heat efficiency improves by over 70%, but the device complexity and initial cost increase
Solution Approach 1:
The multi-stage distillation system operates with a degree of self-service where each column utilizes the vapor stream from the previous column as its heat source. This self-service mechanism reduces the need for external energy input at each stage, allowing the system to maintain high productivity and recovery rates while minimizing additional energy costs.
Solution Approach 2:
The system recovers and reuses vapor streams that would otherwise be discarded. Each column captures and utilizes the vapor from the previous column, ensuring that heat energy is recovered and reused across multiple stages. This recovery mechanism significantly improves heat efficiency and productivity while reducing waste.
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 the efficiency of heat use by over 70% compared to single distillation column systems, achieving higher water flux and recovery rates while minimizing brine discharge and reducing energy costs, thereby improving the overall economic viability of FO desalination.
Implementation Method 1
a first heat transfer means having an inlet coupled to a source of thermal energy and an outlet coupled to the first distillation column for introducing thermal energy to the first distillation column to cause at least a portion of the draw solution in the first distillation column to vaporize
Implementation Method 2
a second heat transfer means having an inlet coupled to the first outlet of the first distillation column for providing a source of thermal energy for the second distillation column
Implementation Method 3
Multi-stage column distillation (MSCD) method for osmotic solute recovery
Data Source
AI summary
A method and apparatus for separating draw solution solutes and product solvent from a draw solution using a plurality of distillation columns is disclosed. In one embodiment, the draw solution is used in a Forward Osmosis (FO) water desalination process. In this embodiment, the draw solution is directed to the plurality of distillation columns in parallel while the energy stream (heat) is directed to the plurality of distillation columns in series such that the efficiency of heat use is improved and in turn the cost of the heat is reduced.