Electrodialysis and Electrodeionization Desalination System

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Solution Overview

Problem

Conventional seawater desalination methods, such as reverse osmosis and thermal processes, face high energy consumption and capital costs, with existing electrodialysis and electrodeionization systems experiencing efficiency declines at lower total dissolved solids (TDS) levels due to concentration polarization and water splitting phenomena.

Innovation Solution

A combined electrodialysis and continuous electrodeionization system utilizing concentration differences to facilitate ion separation, with multiple stages of electrodialysis reducing TDS to 3,500-5,500 ppm followed by ion exchange softening and final desalination to less than 1,000 ppm using continuous electrodeionization, minimizing energy consumption by synergizing existing and novel technologies.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If conventional reverse osmosis systems are used for seawater desalination, then desalination can be achieved, but energy consumption is high (at least 2.5 kWh/m3)

Engineering Contradiction:

Improveenergy consumptionVSAvoiddesalination efficiency

Core Design Contradiction:

Use of energy by moving objectVSProductivity

Solution Approach 1:

The desalination process is divided into multiple stages: first electrodialysis stage, second electrodialysis stage, and final reverse osmosis stage. Each stage operates at optimized conditions for its specific TDS range, preventing energy waste from attempting single-stage desalination of high-salinity seawater

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The system changes operating parameters (electrical potential, flow rates) based on TDS concentration at each stage. Electrodialysis operates at low electrical potentials when TDS is high, then transitions to reverse osmosis at lower TDS where pressure-driven separation is more efficient

Inventive Principle:

Principle #35Parameter changes

2Use of energy by moving object

If electrodialysis systems are used for desalination, then lower energy consumption can be achieved, but efficiency declines at lower TDS levels due to concentration polarization and water splitting

Engineering Contradiction:

Improveenergy consumptionVSAvoiddesalination efficiency

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The system dynamically transitions between different desalination technologies based on TDS concentration. Electrodialysis is used dynamically at high TDS levels where it is most efficient, then the system switches to reverse osmosis at lower TDS levels to avoid efficiency decline from concentration polarization

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The multi-stage system maintains continuous useful action by ensuring each stage operates within its optimal efficiency range. The transition from electrodialysis to reverse osmosis ensures uninterrupted desalination while maintaining high efficiency throughout the entire process

Inventive Principle:

Principle #20Continuity of useful action

3Productivity

If thermal processes are used for desalination, then desalination can be achieved, but power consumption is high due to phase change requirements

Engineering Contradiction:

Improvedesalination capabilityVSAvoidpower consumption

Core Design Contradiction:

ProductivityVSUse of energy by moving object

Solution Approach 1:

The system replaces thermal phase-change processes with electrochemical and pressure-driven separation processes. Electrodialysis uses electrical fields to drive ion migration, and reverse osmosis uses pressure to drive water through membranes, eliminating the need for vaporization and condensation cycles

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

4Ease of manufacture

If reverse osmosis systems are used, then lower capital and operating costs can be achieved, but energy recovery devices are still required to meet energy targets

Engineering Contradiction:

Improvecapital and operating costsVSAvoidenergy consumption

Core Design Contradiction:

Ease of manufactureVSUse of energy by moving object

Solution Approach 1:

The system performs preliminary desalination through two electrodialysis stages that remove a significant portion of salts before reverse osmosis. This preliminary action reduces the energy burden on the reverse osmosis stage, eliminating or reducing the need for energy recovery devices while maintaining cost-effectiveness

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS10662085B2Low energy system and method of desalinating seawater

Publication Date: 2020.05.26 EVOQUA WATER TECHNOLOGIES LLC

AI summary

A low energy water treatment system and method is provided. The system has at least one electrodialysis device that produces partially treated water and a brine byproduct, a softener, and at least one electrodeionization device. The partially treated water stream can be softened by the softener to reduce the likelihood of scale formation and to reduce energy consumption in the electrodeionization device, which produces water having target properties. At least a portion of the energy used by the electrodeionization device can be generated by concentration differences between the brine and seawater streams introduced into compartments thereof. The brine stream can also be used to regenerate the softener.