Performance evaluation of diaphragm electrolysis cell for alkali production

Abstract

Seawater desalination technology is important for solving water shortage problems. RO desalination is the most frequently used process for obtaining fresh water from salt water. Electrolysis is also one way of reusing the enriched brine. Alkali-activated products can be made by producing NaOH after electrolysis. There are three kinds of brine electrolysis methods including diaphragm, membrane, and mercury methods. This study was conducted using a 200 mL electrolysis diaphragm cell. Tedlar bags were used in order to gather gases such as Cl₂, O₂, and H₂. The head was less than 10 mm when a diaphragm with a 10 μm pore size was used. The data in this study was collected to analyze the relationships between concentration, chloride removal, and current density (CD). Our results showed that pore size influenced the head at the anode. Chloride removal was not high even when a high CD was applied. When the CD was 200 mA/cm², the maximum NaOH concentration was 1.85%. However, the NaOH concentration was just 1.5% at 100 mA/cm². The correlation coefficient was also more than 0.99 at a 200 mA/cm² CD. The applied high CD at the diaphragm cell was unstable because it caused high temperature. The high CD caused the head of the reactor to be higher. Thus, the diaphragm cell could not be operated anymore. The sensitivity analysis results showed that control of the flow rate was more efficient than control of the CD.

Keywords:

• Alkali production
• Chlor-alkali
• Diaphragm
• Electrolysis
• Enrichment brine

Acknowledgment

This research was supported by a grant (code 15IFIP-B065893-03) from the Industrial Facilities and Infrastructure Research Program funded by Ministry of Land, Infrastructure and Transport of Korean government.

Notes

Presented at 2015 Academic Workshop for Desalination Technology held in the Institute for Far Eastern Studies Seoul, Korea, 23 October 2015