Electrolyser chlor-alkali

Mr W C Meadowcroft E I DuPont de Nemours Co Inc, Nafion Customer Service Lab, DuPont Fayetteville Works, 22828 NC 87 Highway West, Fayetteville, NC 28306, USA High Current Density Operation of Chlor-alkali Electrolysers - The Standard for the New Millennium. E-mail william.c.meadowcroft usa.dupont.com... 

High Current Density Operation of Chlor-Alkali Electrolysers - the Standard for the New Millennium... 

Among the cation permeable membranes, the perfluorinated membranes which have been developed as separators for fuel cells and chlor-alkali electrolysers show the characteristic features of superselectivity, very high thermal stability and chemical resistance, which are not obtained by the other classes of polymeric ion permeable membranes. Three commercial forms of cation permeable perfluorinated membranes have been proposed ... 

For chlor-alkali electrolysers, a biiayer perfluorinated membrane is produced by Du Pont de Nemours. One layer is perfluorosulphonic, the other is perfl uorocarboxylic. 

Mr K A Stanley ICI Chlor Chemicals, The Heath, Runcorn, Cheshire, WA7 4QF, UK. Practical Operating Differences in Converting a Diaphragm Cell Chlor-Alkali Plant to a Membrane Electrolyser Plant. E-mail keith stanley ici.com... 

Owing to the fact that nearly all the heat generated by this type of electrolyser has to be dissipated via the anolyte flow, for the full industrial-scale demonstration electrolyser with an element size 2.5 m2 it was decided to use the bubble jet system [3], which was successfully tested previously with the chlor-alkali method. For FIC1 electrolysis, which from the material side is optimised to an approximate operation temperature of 60°C, an intense vertical temperature-profile flattening is essential to reduce the external flow rates and to allow rather low anode-side inlet temperatures. The intensive vertical mixing with the bubble jet proved to be suitable for this purpose. 

Iacopetti, L. (1998) Membrane electrolyser operating at high current density. In Modern Chlor-Alkali Technology, Vol. 7 (ed. S. Sealey), pp. 85-94. Society of Chemical Industry, London and Royal Society of Chemistry, Cambridge. 

EMOS has to date been mostly used in chlorate manufacture, but R2 in Montreal, Canada has recently installed its system on an FM-21 1500-type cell chlor-alkali production facility. This is presently a pilot installation, with only six cells currently being monitored. This installation has led to the monitoring of cell currents rather than cell voltages owing to the monopolar design of these electrolysers. It is too soon to make detailed conclusions about this installation as it has only been fully operational since January 2000. 

Kvaerner Chemetics have developed a novel, patented process [1] for the removal of multivalent anions from concentrated brine solutions. The prime market for this process is the removal of sodium sulphate from chlor-alkali and sodium chlorate brine systems. The sulphate ion in a brine solution can have a detrimental effect on ion-exchange membranes used in the production of chlorine and sodium hydroxide consequently tight limits are imposed on the concentration of sulphate ions in brine. As brine is continuously recycled from the electrolysers back to the saturation area, progressively more and more sulphate ions are dissolved and build up quickly in concentration to exceed the allowable process limits. A number of processes have been designed to remove sulphate ions from brine. Most of these methods are either high in capital or operating cost [2] or have large effluent flows. 

Practical Operating Differences in Converting a Diaphragm Cell Chlor-Alkali Plant to a Membrane Electrolyser Plant... 

Advances during the past 20 years in membrane, electrolyser, electrode, and brine purification technologies have substantially raised the performance levels and efficiency of chlor-alkali production by ion-exchange membrane electrolysis, bringing commercial operations with a unit power consumption of 2000-2050 kWh per ton of NaOH or lower at 4 kA m-2 current density with a membrane life of four years or longer. 

The ML32NCH electrolyser equipped with the Aciplex F-4401 membrane has been in commercial operation at 6 kA m-2 for approximately one year at Asahi Chemical s chlor-alkali plant. As shown in Figs 17.16 and 17.17, the electrolyser has achieved a cell voltage of 3.17 V and a current efficiency of 96%, while operating at 6kA m-2. This operation is continuing the present plan is to investigate the performance of the ML32NCH at a current density of 8 kA m-2. 

Several years ago, ICI ETB looked at the total market for chlor-alkali membrane technology and considered how to develop an electrolyser that would extend its product and market range. A detailed analysis was carried out and many chlor-alkali producers were consulted. As a result of this work ICI ETB has developed an electrolyser called BiChlor. 

With the development of a chemically extremely stable cation-exchange membrane based on sulfonated poly-tetra-fluor-ethylene by Du Pont in the late 60 s the chlor-alkali ne membrane electrolysers were introduced [8],... 

Girvan, I.J.M., Brereton, C. and Crawford, A.L. (1989) FM21 electrolysers - their application to a range of operations in chlor-alkali plants, in Modem Chlor-Alkali Technology, vol. 4 (eds N.M. Prout and J.S. Moorhouse), Elsevier Apphed Science. 

Fig. 3.19 Chlor-alkali cell room based on FM21 SP electrolysers. (Courtesy ICI Chemicals and Polymers Ltd.)... 

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