A numerical model has been developed, based on an implicit finite difference technique, for the solution of a set of coupled non-linear partial differential equations (based on the Nemst-Planck equation), and linear and non-linear algebraic equations. These equations govern the mass transport and homogeneous chemical reactions in a simplified membrane chlor-alkali cell anolyte compartment. Membrane chlor-alkali cells are used for the industrial production of chlorine and sodium hydroxide, by electrolysis of brine. The model has been developed in an attempt to gain insight into the very localised chemistry which occurs in the hydrodynamic boundary layers within the electrolyser; chemistry which is strongly suspected to have a significant influence on the bulk chemistry, particularly on the homogeneous reactions leading to loss of chlorine through the formation of thermodynamically stable unwanted by-products such as the chlorate ion. These effects are very difficult to measure experimentally, making modelling the most attractive option. A set of experiments have been performed on laboratory scale electrolysers, in an attempt to characterise the cell chemistry, and produce data for model validation. Results are presented from the model demonstrating that the numerical approach adopted produces stable and physically plausible results under a range of operating conditions. It also demonstrates that the chemistry in both the anode and membrane hydrodynamic boundary layers differs significantly from that in the bulk. The experimental work has provided valuable insight into the mechanism of the loss reactions. Results of the experimental work are also compared with the results of the modelling.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:250666 |
| Date | January 2001 |
| Creators | Leah, Robert Timothy |
| Contributors | Brandon, Nigel ; Vesovic, Velisa |
| Publisher | Imperial College London |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/10044/1/63785 |
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