Swap De-scaling in Multistage Thermal Desalination
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Solution Overview
Problem
Multiple effect evaporation or flash desalination processes face reliability challenges due to scaling issues and high operational costs, particularly in Zero Liquid Discharge (ZLD) systems, which require frequent de-scaling and consume significant energy and resources.
Innovation Solution
A multistage desalination system that periodically swaps the concentration of saltwater between stages, using a controller to manage valving and salinity sensors to transition between normal and swapped modes, allowing for efficient de-scaling and reducing scaling buildup by altering the operating concentration of saltwater.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple effect evaporation or flash desalination processes operate at high concentrations to achieve Zero Liquid Discharge, then water treatment effectiveness is improved, but scaling buildup increases and reliability decreases
Solution Approach 1:
The system periodically swaps the saltwater concentration between effects, alternating between high concentration operation (for ZLD) and low concentration operation (for de-scaling). This periodic switching allows the system to achieve both effective water treatment and periodic cleaning of scaling deposits, resolving the contradiction between reliability and scaling buildup.
Solution Approach 2:
The system changes the concentration parameter of saltwater between different effects. By swapping which effect receives high concentration saltwater and which receives low concentration saltwater, the system can operate at high concentrations for treatment effectiveness while periodically providing low concentration conditions to prevent and remove scaling, thus improving reliability without compromising ZLD capability.
2Object-affected harmful factors
If ZLD processes operate at high concentrations to produce solids for landfill or secondary use, then environmental compliance is improved, but energy consumption increases
Solution Approach 1:
The system uses periodic concentration swapping to alternate between high energy consumption periods (when processing high concentration saltwater for ZLD compliance) and low energy consumption periods (when processing low concentration saltwater for de-scaling). Over time, this averages out the energy consumption while maintaining environmental compliance through regular ZLD operation.
Solution Approach 2:
The system changes the concentration parameter periodically, which directly affects energy consumption. By alternating between high and low concentration operation, the system can meet environmental compliance requirements for ZLD while reducing overall energy consumption compared to continuous high concentration operation.
3Productivity
If saturated operation is used to maximize desalination efficiency, then productivity is improved, but scaling and solids buildup increases causing performance degradation
Solution Approach 1:
The system periodically switches between saturated operation (for maximum desalination efficiency) and unsaturated operation (for de-scaling). This periodic action allows the system to maintain high productivity during saturated operation while preventing permanent scaling buildup through periodic unsaturated cleaning cycles, thus preserving performance stability.
Solution Approach 2:
Instead of continuously operating at saturation to maximize productivity, the system inverts the approach by periodically operating at low concentration to remove scaling. This inversion of the normal operating mode allows the system to maintain long-term productivity by preventing the harmful effects of continuous saturated operation.
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 the reliability and efficiency of desalination processes by reducing scaling issues and operational costs, while maintaining a stable temperature cascade, thereby improving plant performance and extending equipment lifespan.
Implementation Method 1
a first evaporation stage for evaporating a first saltwater at a first temperature
Implementation Method 2
a first condensation stage, fluidly coupled to the first evaporation stage, for condensing product water from vapor that evaporates from the saltwater in the first evaporation stage
Implementation Method 3
a second evaporation stage for evaporating a second saltwater at a second temperature
Implementation Method 4
a second condensation stage, fluidly coupled to the second evaporation stage, for condensing product water from vapor that evaporates from the saltwater in the second evaporation stage
Implementation Method 5
a heat exchanger thermally coupling the first condensation stage to the second evaporation stage for transferring heat from the first condensation stage to the second evaporation stage
Data Source
AI summary
A multistage thermal desalination system, together with its associated method of use, allows de-scaling of subsystems exposed to saturated saltwater by alternating the saturation stage of the process between two neighboring physical desalination stages. The desalination system is provided with at least one transfer conduit, at least one pump, and valving to permit saltwaters being desalinated by higher and lower stage desalination subsystems to be swapped. By replacing the saturated saltwater in a higher salt concentration desalination subsystem with lower salt concentration saltwater, the scaling in higher salt concentration desalination subsystem is reduced while the saturation load is placed on another of the desalination subsystems.