Research article Cell voltage and chlorine current efficiency of aqueous HCl electrolysis: artificial neural network modeling M. Abbasian 1 * and A. Sattari 2 1 Department of Basic Science, Payame Noor University, PO Box: 19395-3697, Tehran, Iran 2 Chemistry and Petrochemicals Division, Fertilizer and Inorganic Research Department, Research Institute of Petroleum Industry, Tehran 1485733111, Iran Received 15 December 2011; Revised 14 April 2012; Accepted 16 April 2012 ABSTRACT: Artificial neural network (ANN) models were developed for the prediction of cell voltage and chlorine current efficiency (ChCE) of HCl electrolysis process. Results of 53 distinct experiments were used for ANN simulations; from which 40 data (75%) were used to train the networks and 13 data (25%) were used to test them. The predicted cell voltages and chlorine current efficiencies were found to be very close to the measured values with root mean square error of 0.087 and 1.726, R 2 of 0.897 and 0.903, T values of 0.885 and 0.887 and average deviations of only 3.45 and 7.18%, respectively. Sensitivity analysis of the developed models showed that among five operating factors, the current density and the anolyte concentration had the highest and the least contributions to the cell voltage, respectively. On the other hand, the ChCE was mostly affected by the oxygen flow rate; meanwhile, the anolyte flow rate had the lowest effect on the ChCE. © 2012 Curtin University of Technology and John Wiley & Sons, Ltd. Keywords: artificial neural network; HCl electrolysis; membrane electrode assembly; Nafion membrane INTRODUCTION Background of the HCl electrolysis process Aqueous solutions of hydrogen chloride (hydrochloric acid) are by-products in many operations, especially where organic hydrocarbon compounds are oxidizingly chlorinated with chlorine. Chlorine is used due to its high reactivity for production of chlorine containing intermediates, e.g. phosgene or chlorinated aliphatic or aromatic compounds. Hydrogen chloride can be a direct by-product of chlorination, e.g. of substitution reactions, but mostly it is generated in subsequent production steps while removing chlorine atoms in order to attain chlorine-free final products. Especially in this case, hydrochloric acid is formed as a by- product. There is a commercial and economic interest in recovering chlorine from these hydrochloric acids and using it for further chlorinations. [1,2] Chlorine can be recovered, for example, electrolytically in an electrochemical cell consisting essentially of an anode space featuring an anode, a cathode space featuring a cathode and an ion exchange membrane separating the two spaces from each other. [3] Current density of an electrochemical cell is related to the reaction rate. Higher current densities provide higher reaction rates, allowing for smaller reactors, and there- fore lower investment. Cell voltage is related to energy requirements for the process. Lower cell voltage requires less energy and therefore lower operating costs. Option- ally, oxygen or a reducible metal ion can be fed to the cathode in order to lower the operating cell voltage. This would result in lower power consumption and therefore lower operating costs. In this study, pure oxygen was selected as the reducing agent. [4] The anode should comprise a corrosion-resistant substrate and an electrochemically active coating. The corrosion resistant substrate is graphite or titanium, titanium alloys, niobium or tantalum. The electroche- mically active coating used is the result of a standard activation with mixtures of oxides of ruthenium, iridium and titanium. The Dimensionally Stable Anode (DSA W ) was used in this study as anode that is a commercially available anode developed based on these materials and shows the lowest over potential for chlorine gas production. [5] The cathode should comprise a carbon-based gas diffusion cathode having a coating of a platinum group metal or a corresponding oxide. The long-term stability of the gas diffusion cathode is low, presumably because loss of contact occurs between the carbon-based gas diffusion elec- trode and the necessary current distribution elec- trode, which rests on the gas diffusion cathode. A *Correspondence to: M. Abbasian, Department of Basic Science, Payame Noor University, PO Box: 19395-3697, Tehran, Iran. E-mail: m_abbasian20@yahoo.com, m_abbasian@pnu.ac.ir © 2012 Curtin University of Technology and John Wiley & Sons, Ltd. Curtin University is a trademark of Curtin University of Technology ASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING Asia-Pac. J. Chem. Eng. (2012) Published online in Wiley Online Library (wileyonlinelibrary.com) DOI: 10.1002/apj.1660