A STUDY OF THE DEGRADEATION AND REGENERATION OF CATION EXCHANGE MEMBRANES IN CHLOR-ALKALI CELLS
Hisham Mohamed Tawfik El Azhary;
Abstract
This investigation is performed on the cation exchange membranes used for chlor alkali production and focuses on the membrane performance and degradation under severe operating conditions. Five different types of membranes were tested. The experiments were carried out at different operation conditions and their effect on the membrane performance was studied. The membrane performance is usually expressed in terms of three parameters, namely, cell potential, current efficiency and power consumption. Such parameters indicate the membrane condition and give an indication of the need for membrane replacement.
The study is divided into three parts, the first part covers the operation under normal operating conditions; all operating parameters were within the allowable ranges, the second part covers the operation where degrees of contamination were brought up to non- allowable ranges and the third part covers attempts to recover the normal membrane performance after degradation by membrane regeneration.
During normal operation the major parameters that affect the performance were adjusted at the design values and the rest of the parameters were adjusted within the allowable range to allow monitoring of cell performance.
During operation under severe conditions the feed brine solution was contaminated using different methods. Brine contamination was carried out by adding high levels of (Mg, Ca, Sr and Ba) salts to study the effect of brine impurities on the membrane performance. Brine contamination methods were carried out in three different ways, namely; Continuous contamination where the brine fed to the laboratory cell was always contaminated during each run, Single spike (dose) contamination where the contaminating solution was injected once into the laboratory cell during each run, and Double spike contamination, where the contaminating solution was injected twice into the laboratory cell. The behaviour of performance was recorded in each case analyzed and discussed.
A trail to recover the collapsed membrane performance was done by the regeneration of the cation exchange membranes under investigation using dilute
0.02N HCl acid at 70° C for 8 hours. In some cases the recovered voltage drop was around !50 mv which represents (up to 77.9% of the deteriorated voltage drop) which means the recovery of I and a half year of operation under standard conditions. Current efficiency deterioration is irreversible under severe degrees of contamination, but it was observed that some cases gave positive results of current efficiency recovery. The recovered current efficiency was around (0.5 - I%) which represents (up to 80% of the deteriorated current efficiency ) which means the recovery of 6 month up to I year of operation under standard conditions.
The results were confirmed by the measurements of the scanning electron microscope (SEM) that have clarified the effect ofregeneration of the membrane by using the dilute hydrochloric acid. •
The study is divided into three parts, the first part covers the operation under normal operating conditions; all operating parameters were within the allowable ranges, the second part covers the operation where degrees of contamination were brought up to non- allowable ranges and the third part covers attempts to recover the normal membrane performance after degradation by membrane regeneration.
During normal operation the major parameters that affect the performance were adjusted at the design values and the rest of the parameters were adjusted within the allowable range to allow monitoring of cell performance.
During operation under severe conditions the feed brine solution was contaminated using different methods. Brine contamination was carried out by adding high levels of (Mg, Ca, Sr and Ba) salts to study the effect of brine impurities on the membrane performance. Brine contamination methods were carried out in three different ways, namely; Continuous contamination where the brine fed to the laboratory cell was always contaminated during each run, Single spike (dose) contamination where the contaminating solution was injected once into the laboratory cell during each run, and Double spike contamination, where the contaminating solution was injected twice into the laboratory cell. The behaviour of performance was recorded in each case analyzed and discussed.
A trail to recover the collapsed membrane performance was done by the regeneration of the cation exchange membranes under investigation using dilute
0.02N HCl acid at 70° C for 8 hours. In some cases the recovered voltage drop was around !50 mv which represents (up to 77.9% of the deteriorated voltage drop) which means the recovery of I and a half year of operation under standard conditions. Current efficiency deterioration is irreversible under severe degrees of contamination, but it was observed that some cases gave positive results of current efficiency recovery. The recovered current efficiency was around (0.5 - I%) which represents (up to 80% of the deteriorated current efficiency ) which means the recovery of 6 month up to I year of operation under standard conditions.
The results were confirmed by the measurements of the scanning electron microscope (SEM) that have clarified the effect ofregeneration of the membrane by using the dilute hydrochloric acid. •
Other data
| Title | A STUDY OF THE DEGRADEATION AND REGENERATION OF CATION EXCHANGE MEMBRANES IN CHLOR-ALKALI CELLS | Other Titles | دراسة عن استهلاك وتنشيط الأغشية للمبادل الكاتيوني في خلايا الكلور - صودا | Authors | Hisham Mohamed Tawfik El Azhary | Issue Date | 2003 |
Recommend this item
Similar Items from Core Recommender Database
Items in Ain Shams Scholar are protected by copyright, with all rights reserved, unless otherwise indicated.