Électrodialyse bipolaire (EDBP)

Pour la récupération des courants de saumure afin de produire des produits acides ou caustiques
L'électrodialyse bipolaire utilise les bases de l'électrodialyse en y ajoutant une membrane bipolaire qui fractionne l'eau en H+ et en OH- à l'intérieur de la colonne d'électrodialyse. This allows the removed salts to be converted in their acid and/or base products.

Le BPED de Veolia peut être utilisé dans de nombreuses applications, telles que la production d'acides organiques, l'ajustement du pH dans les boissons ou l'utilisation de saumures industrielles pour générer des sous-produits acides et caustiques à valeur ajoutée.

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Aperçu
Fonctionnement

Aperçu

Veolia's BPED stacks use the same concepts as standard electrodialysis, with the addition of a so-called bipolar membrane that allows water to be split in H+ and OH- ions. By assembling membranes and spacers in specific configurations, the stacks can be used to:

3C-BPED:
- Split non-organic salts and produce separate acid and base streams.
2C-BPED:
- Split organic salts to product the organic acid and a base stream (e.g. potassium lactate (La) splitting to KOH and HLa).
- pH modification of (up or down)

Caractéristiques de la colonne

Up to 400 cells of membranes with application-specific membranes
Total active membrane area of up to 128 m2 per stack
Colonne à double entrée pour garantir une pression et un flux constants.
Robust stack design that is capable of Clean-in-Place (CIP) and can also be easily removed and disassembled for cleaning, maintenance, and component replacement if needed.
Les pièces de rechange peuvent aisément être stockées sur le site.
Works with Veolia’s proprietary ion exchange membranes that offer specific benefits per applications:
- AR119TP: acid-blocking membrane for chloride applications
- AR118TP: acid-blocking membrane for sulfate applications

Under typical operating conditions of 375 A/m2, a 200C 3C-BPED stack can convert about 45.7 kg/h of NaCl, but can also be used to convert other inorganic salts (Na2SO4, LiCl, Li2SO4, KCl, K2SO4). The strength of the acid and base can be tuned between 0.5N and 2N.

Fonctionnement

Bipolar Electrodialysis introduces a BP membrane in the stack that splits water in H+ and OH- when the voltage is applied.

As with standard electrodialysis (Figure 1) , the voltage also moves the ions from the salt feed stream through the cation exchange and anion exchange membranes. Contrary to standard ED though, the cations and anions are not entering the same water stream, but in separate stream on each side of the BP membrane, thus combining with the H+ and OH- to form their conjugated acid and base. This is called 3-compartment BPED, or 3C-BPED.

In a 2-compartment BPED (2C-BPED) configuration, one of the monopolar membrane is left out of the equation, meaning the applied voltage will only move either anions or cations away from the salt feed solution, replacing them by OH- or H+ ions respectively:

BPED principle

Figure 1: Standard Electrodialysis Process Diagram

2C-BPED-C (Figure 2):

In this case, the cation exchange membrane is kept and the anion exchange membrane is removed from the stack.
When the voltage is applied, the cations move through the cation exchange membrane and combine with the OH- generated in the BP membrane, forming a separate base stream.
The H+ from the BP membrane enters the salt feed stream and decreases the pH.
This is typically used for organic salt splitting, generating an organic acid and a base stream that can be reused in the upstream process.

BP2-C principle

Figure 2: 2C-BPED-C Process Diagram

2C-BPED-A (Figure 3):

In this case, the anion exchange membrane is kept and the cation exchange membrane is removed from the stack.
When the voltage is applied, the anions move through the anion exchange membrane and combine with the H+ generated in the BP membrane, forming a separate acid stream.
The OH- from the BP membrane enters the salt feed stream and increases the pH.
This is typically used for pH control of stream like wine and fruit juice, or ammonium nitrate splitting.

BP2-A principle

Figure 3: 2C-BPED-A Process Diagram

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