Metal Instabilities and its Effect on Cell Performance during Aluminium Smelting

2013 ◽  
Vol 828 ◽  
pp. 45-54 ◽  
Author(s):  
Anupam Agnihotri ◽  
Shail Umakant Pathak ◽  
Jyoti Mukhopadhyay
Keyword(s):  
Energy Consumption ◽  
Current Efficiency ◽  
Cell Voltage ◽  
Aluminum Electrolysis ◽  
Cell Performance ◽  
Consumption Pattern ◽  
Magnetic Current ◽  
Zero Current ◽  
Aluminium Smelting ◽  
Rolling Noise

The Hall-Heroult process for the production of aluminium is based on the electrochemical reduction of alumina (Al2O3) dissolved in a cryolite (Na3AlF6) based electrolyte. Instability in cell voltage is referred to as noise. Normal voltage noise is inevitable due to bubble evolution and it has little effect on performance parameters such as, current efficiency and power consumption. Metal rolling noise (wavy noise) is caused by the disturbances in cell magnetic field and it affects the cell current efficiency adversely. Investigating the causes of the cell instability in the aluminium smelting cells can lead to better cell performance. Understanding the variation in cell voltage is critical for cells, because magnitude of voltage determines the energy consumption pattern in the process and hence, any saving on voltage can save energy. Voltage affects the current efficiency of the cell and an optimum cell voltage leads to higher current efficiency without compromising on energy consumption. Magnetic, current distribution, heat loss and voltage at zero current measurements along with online current and voltage signal can help to identify the problems and their combined effects on the performance of the cells. In order to estimate the loss in current efficiency of the aluminum electrolysis cells due to metal instabilities, measurements were performed and data analyzed. The present paper analyses the effect of voltage fluctuations (noise) during metal instability along with cause of instability and its effect on current efficiency of the cell. Measurements carried out to estimate the deviations from the normal cell operations are also discussed.

scholarly journals Selective Recovery of Tellurium from the Tellurium-Bearing Sodium Carbonate Slag by Sodium Sulfide Leaching Followed by Cyclone Electrowinning

Metals ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1176
Author(s):  
Zhipeng Xu ◽  
Zoujiang Li ◽  
Dong Li ◽  
Xueyi Guo ◽  
Ying Yang ◽  
...  
Keyword(s):  
Energy Consumption ◽  
Current Efficiency ◽  
Sodium Carbonate ◽  
Flow Rate ◽  
Current Density ◽  
Sodium Sulfide ◽  
Cell Voltage ◽  
Promising Alternative ◽  
Selective Recovery ◽  
Solid Ratio

The rigorous environmental requirements promote the development of new processes with short and clean technical routes for recycling tellurium from tellurium-bearing sodium carbonate slag. In this paper, a novel process for selective recovery of tellurium from the sodium carbonate slag by sodium sulfide leaching, followed by cyclone electrowinning, was proposed. 88% of tellurium was selectively extracted in 40 g/L Na2S solution at 50 °C for 60 min with a liquid to solid ratio of 8:1 mL/g, while antimony, lead and bismuth were enriched in the leaching residue. Tellurium in the leach liquor was efficiently electrodeposited by cyclone electrowinning without purification. The effects of current density, temperature and flow rate of the electrolyte on current efficiency, tellurium recovery, cell voltage, energy consumption, surface morphology, and crystallographic orientations were systematically investigated. 91.81% of current efficiency and 95.47% of tellurium recovery were achieved at current density of 80 A/m2, electrolyte temperature of 45 °C and electrolyte flow rate of 400 L/h. The energy consumption was as low as 1.81 kWh/kg. A total of 99.38% purity of compact tellurium deposits were obtained. Therefore, the proposed process may serve as a promising alternative for recovering tellurium from tellurium-bearing sodium carbonate slag.

scholarly journals Control of Temperature and Aluminum Fluoride Concentration Based on Model Prediction in Aluminum Electrolysis

2014 ◽  
Vol 2014 ◽  
pp. 1-5 ◽  
Author(s):  
Zeng Shuiping ◽  
Wang Shasha ◽  
Qu Yaxing
Keyword(s):  
Energy Consumption ◽  
Fluoride Concentration ◽  
Cell Voltage ◽  
Aluminum Electrolysis ◽  
Aluminum Production ◽  
Aluminum Fluoride ◽  
Technical Parameters ◽  
Aluminum Company ◽  
External Conditions ◽  
Addition Rate

The temperature and the aluminum fluoride (AlF3) concentration of electrolyte greatly affect the current efficiency and energy consumption in aluminum electrolysis. This paper developed a new kind of algorithm to control the temperature and AlF3concentration of electrolyte for 300 kA prebake aluminum production cells by altering the setting cell voltage and the AlF3adding rate. One is liquidus model which can be used to calculate AlF3concentration of electrolyte by some technical parameters and target superheat and the other is the temperature models which can determine the required cell voltage by the technical parameters and target temperature. Consequently, the AlF3addition rate can be decided by the AlF3concentration. The temperature and AlF3concentration of electrolyte in the production are measured and the differences between the measurement and the corresponding calculation are used as feedback to correct the model. The coefficients in the model are also revised according to the external conditions. This system has been used in an aluminum company for 2 years. Both the temperature and the AlF3concentration of electrolyte can be controlled as required and the energy consumption of the aluminum production was much decreased.

scholarly journals Removal of Cadmium from Simulated Wastewaters Using a Fixed Bed Bio-electrochemical Reactor

2020 ◽  
Vol 26 (12) ◽  
pp. 110-130
Author(s):  
Duaa R. Saad ◽  
Ziad T. Alismaeel ◽  
Ali H. Abbar
Keyword(s):  
Energy Consumption ◽  
Current Efficiency ◽  
Removal Efficiency ◽  
Applied Voltage ◽  
Ph Value ◽  
Fixed Bed ◽  
Cell Voltage ◽  
Packed Bed ◽  
Electrochemical Reactor ◽  
Operating Conditions

In this research, the removal of cadmium (Cd) from simulated wastewater was investigated by using a fixed bed bio-electrochemical reactor. The effects of the main controlling factors on the performance of the removal process such as applied cell voltage, initial Cd concentration, pH of the catholyte, and the mesh number of the cathode were investigated. The results showed that the applied cell voltage had the main impact on the removal efficiency of cadmium where increasing the applied voltage led to higher removal efficiency. Meanwhile increasing the applied voltage was found to be given lower current efficiency and higher energy consumption.  No significant effect of initial Cd concentration on the removal efficiency of cadmium but increasing the initial concentration would be given higher current efficiency and lower energy consumption. The results established that using a pH value lower than three results in a sharp decrease in the removal efficiency as well as  using a pH value higher than seven results in decreasing the removal efficiency. Using a mesh number higher than 30 gave a lower removal efficiency. The best operating conditions were found to be an applied potential of 1.8 V, an initial Cd concentration of 125 ppm, and a pH of 7. Under these operating conditions with the using a stack of stainless with mesh number 30 as a packed bed cathode, a complete removal efficiency of Cd(100%)  was obtained at a current efficiency of 83.57% and energy consumption of 0.57 kWh/kg Cd.

A ALO-LSSVM Model for the Cell Voltage Optimization in Aluminum Electrolysis Process

2020 ◽  
Author(s):  
Chen-hua Xu ◽  
Jin-zhi Zhang ◽  
Ruo-jun Cheng ◽  
Rui Chen ◽  
Zhu-guang Luo ◽  
...  
Keyword(s):  
Cell Voltage ◽  
Aluminum Electrolysis ◽  
Electrolysis Process

Energy Consumption Pattern of Residential Buildings: Case Study of Residential Area in Batu Pahat, Johor

2020 ◽  
Vol 12 (9) ◽  
Author(s):  
Junaidah Jailani ◽  
◽  
Norsyalifa Mohamad ◽  
Muhammad Amirul Omar ◽  
Hauashdh Ali ◽  
...  
Keyword(s):  
Energy Consumption ◽  
Residential Buildings ◽  
Residential Area ◽  
Consumption Pattern ◽  
Air Conditioners ◽  
Residential Sector ◽  
Waste Energy ◽  
Main Factor ◽  
Energy Consumption Pattern

According to the National Energy Balance report released by the Energy Commission of Malaysia in 2016, the residential sector uses 21.6% of the total energy in Malaysia. Residents waste energy through inefficient energy consumption and a lack of awareness. Building occupants are considered the main factor that influences energy consumption in buildings, and to change energy consumption on an overall scale, it is crucial to change individual behaviour. Therefore, this study focused on analysing the energy consumption pattern and the behaviour of consumers towards energy consumption in their homes in the residential area of Batu Pahat, Johor. A self-administrated questionnaire approach was employed in this study. The findings of this study showed that the excessive use of air conditioners was a significant factor in the increasing electricity bills of homeowners as well as the inefficient use of electrical appliances. Also, this study determined the effect of awareness on consumer behaviour. This study recommends ways to help minimise energy consumption in the residential area.

scholarly journals Energy consumption pattern and renewable energy alternatives in Madi Kalyanpur, Chitwan, Nepal

2016 ◽  
Vol 4 ◽  
pp. 47-52
Author(s):  
Sumitra Poudel ◽  
Narayan Prassad Chaulagain ◽  
Manoj Aryal
Keyword(s):  
Energy Consumption ◽  
Greenhouse Gases ◽  
Alternative Energy ◽  
Greenhouse Gas Emission ◽  
Economic Benefits ◽  
Consumption Pattern ◽  
Liquefied Petroleum Gas ◽  
Fuel Wood ◽  
Co2 Equivalent ◽  
Energy Consumption Pattern

Energy consumption pattern and greenhouse gases emission are interrelated. The unsustainable use of biomass and widespread use of commercial energy are of the major sources of greenhouse gas emission. The alternative to kerosene for lighting is solar home system (SHS), which is one of the potential renewable technologies for rural electrification. The present study has analyzed household energy consumption pattern and greenhouse gases emission from energy consumption practices as well as environmental and economic benefits of SHS in Madi Kalyanpur Village Development Committee of Chitwan district. For the purpose, the primary data were collected through household questionnaire survey, key informant interview (KII) and focus group discussion (FGD). The analysis has shown that 22% of household use all types of energy, i.e. fuel-wood, LPG (liquefied petroleum gas), biogas and SHS as the sources of energy. Thirty-five percent households use fuel-wood, LPG and SHS, 24% use fuel-wood, biogas and SHS, 1% used LPG and SHS, 5% use biogas and SHS, 4% use LPG, biogas and SHS and 9% use fuel-wood and SHS as a source of energy. Almost all people have been using SHS for the lighting purpose. The average annual greenhouse gases emission per household from fuel-wood and liquefied petroleum gas consumption was 7.89 ton and 0.17 ton of CO2 equivalent respectively. Typically, a 40 Wp SHS reduced the consumption of kerosene by 42 liter annually for lighting that displaced 0.11 ton of CO2 equivalent per household per year. The simple payback period for typically 40 Wp SHS was found to be nine years with no subsidy, seven years with subsidy from Alternative Energy Promotion Centre and two years with Indian Government Grant. Similarly, the benefit-cost ratios were found to be 3.1, 3.5 and 4.6 for the systems with no subsidy, with AEPC subsidy and with Indian Grant, respectively.

scholarly journals The Effect of Cell Compression and Cathode Pressure on Hydrogen Crossover in PEM Water Electrolysis

2021 ◽  
Author(s):  
Agate Martin ◽  
Patrick Trinke ◽  
Markus Stähler ◽  
Andrea Stähler ◽  
Fabian Scheepers ◽  
...  
Keyword(s):  
Mass Transport ◽  
Cell Voltage ◽  
Water Electrolysis ◽  
Material Design ◽  
Operating Conditions ◽  
Cell Performance ◽  
Membrane Electrode ◽  
Current Densities ◽  
Hydrogen Crossover ◽  
The Impact

Abstract Hydrogen crossover poses a crucial issue for polymer electrolyte membrane (PEM) water electrolysers in terms of safe operation and efficiency losses, especially at increased hydrogen pressures. Besides the impact of external operating conditions, the structural properties of the materials also influence the mass transport within the cell. In this study, we provide an analysis of the effect of elevated cathode pressures (up to 15 bar) in addition to increased compression of the membrane electrode assembly on hydrogen crossover and the cell performance, using thin Nafion 212 membranes and current densities up to 3.6 A cm-2. It is shown that a higher compression leads to increased mass transport overpotentials, although the overall cell performance is improved due to the decreased ohmic losses. The mass transport limitations also become visible in enhanced anodic hydrogen contents with increasing compression at high current densities. Moreover, increases in cathode pressure are amplifying the compression effect on hydrogen crossover and mass transport losses. The results indicate that the cell voltage should not be the only criterion for optimizing the system design, but that the material design has to be considered for the reduction of hydrogen crossover in PEM water electrolysis.

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