IDENTIFICATION OF DENDRITIC CATHODE FORMATION PROBLEM IN ELECTROREFINING PLANT AND ITS MINIMIZATION EFFORTS

• Main Author: PRANATA KUSUMAH (nim : 12506019), PRIYANDI
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/23712
• Institution: Institut Teknologi Bandung

PT. Timah Tbk. Is second largest tin producer in the wolrld after China. Their main commodity is a tin metal with Sn content of 99.99% or better known with a trademark of Banka Fournine. Banka Fournine was produced from refinery process using electrorefining path. Electrorefining process have advantages that able to separate almost all impurities in one stage of process furthermore the tin metal produced has a high purity in this case attain 99,99% purity. One of the problems that electrorefining process was faced is formation of <br /> <br /> <br /> <br /> <br /> dendritic cathode which triggered short circuit. Short circuit resulting drop in current efficiency and increased electrical energy consumption per weight unit of the purified Sn product and high anode scrap to be melted down again. Cathode uneven growth or dendritic can trap electrolytes and impurities that can degrade the purity of the product. <br /> <br /> <br /> <br /> <br /> This study aimed to identify the problems that led to the formation of dendritic cathode and short circuit in order for improvement in the process. Observations and measurement at site have been carried out to determine current eficiency, cell voltage and energy consumption in the electrorefining plant (ER) Muntok, PT. Timah <br /> <br /> <br /> <br /> <br /> Tbk. and its correlation with the formation of dendritic cathode and short circuit. seasurements have been performed on four electrolytic bath for 2 anode periods and 6 periods of cathode harvest time. A series of electrolysis in a lab-scale experiments have been conducted to study the effect of additive concentration and concentration ratio, ie gelatin, eugenol and thiourea on the formation of dendritic cathode and short circuit. The addition of additive carried out at once into the electrolysis cell as was done in the ER <br /> <br /> <br /> <br /> <br /> plant, Muntok compared with the addition of continuously into the electrolysis cell. To understand the effect of additive addition to cathodic polarization behavior, curves polarization measurements have been carried out with potentiostat at various concentrations and the ratio of the concentration of gelatin and eugenol. <br /> <br /> <br /> <br /> <br /> Observations and measurements at the site on period 4 - 8 - 2010 to 17-9-2010 on the bath electrolysis C3, C4, D3, and D4 showed that the average weight per Sn deposition is quite variable in the interval of 50-100 kg per bath electrolysis per cathode harvest period. <br /> <br /> <br /> <br /> <br /> Current efficiency measured about 58-77% with an average total for the four electrolytic bath during 6 cathode harvest period = 66.15%. Relatively low current efficiency is correlated with the number of short circuit due to dendrite growth observed in electrolysis <br /> <br /> <br /> <br /> <br /> bath. Average cell voltage is measured quite varied in the range of 121 mV to 200 mV which correlated with the consumption of electrical energy between 0.080 kWh / kg of Sn to 0.160 kWh / kg Sn. The results of electrolysis in laboratory experiments showed that the <br /> <br /> <br /> <br /> <br /> concentration of gelatin and eugenol and the ratio determine the resulting morphology of Sn deposition. The experimental results showed that the ratio of gelatin and eugenol which minimizes the formation of short dendrites are 1.5: 1 to 2: 1. The addition of additive <br /> <br /> <br /> <br /> <br /> continuously give better morphology of Sn deposits than if the addition is done once at the beginning of the process. Measurement of polarization curves with a potentiostat showed that the addition of gelatin and eugenol from 1-6 grams / liter give the effect of cathodic polarization on the cathode.