Applying fundamental data to reduce the carbon dioxide footprint of aluminum smelters

Abstract

Overview Aluminum: Cast Shop and AlloysHow would you… …describe the overall signifi cance of this paper? By applying fundamental understanding of the reactivity of anodes, the solubility of alumina, and cell dynamics to modifying control and operating parameters in aluminum smelters, you not only improve energy effi ciency but also bring about substantial reductions in greenhouse gas emissions. By comparing the fundamentals against control and work practices of potlines producing 1.9 million tonnes of aluminum annually a reduction in the greenhouse gas footprint of 1.98 million tonnes /annum resulted. …describe this work to a materials science and engineering professional with no experience in your technical specialty?Modifi ed alumina feeding routines were successfully developed for operating smelters that resulted in better control and greater stability of the metal pad through avoiding accumulation of undissolved material. Simultaneously, knowledge of the dynamics of cell operating variables was applied to reduce incorrect reaction to chemistry and temperature swings. The result was not only improved energy effi ciency but major reductions in anode effect frequencies, and hence the greenhouse gas footprint of the eight smelter pot lines. …describe this work to a layperson?The control philosophy and work practices of some aluminum smelting potlines were examined against information pertaining to greenhouse gas emission. Considerable changes were found to be possible despite the hardware and design constraints of each potline. The result has been an average reduction of 950 kg of carbon dioxide equivalents per tonne of aluminum produced.The aluminum smelting process is a strong emitter of CO 2 with three major contributions: that arising from electrical energy generation and its utilization, the process conversion contribution linked with anode consumption and anode production, and the greenhouse gas equivalents of the intermittent perfl uorocarbon (PFC) emissions. Fundamental studies of alumina solubility, the electrochemical mechanism for triggering the onset of PFC emissions, and the importance of both mixing and current density on the speed of termination of anode effects, help defi ne better paths for process operation. In conjunction with advising prebake aluminum smelters on process optimization, the authors have successfully tested the differences in theory and practice, and applied fundamentals in the operating environment to change some of the installed control strategies, termination mechanisms, and work practices. These changes have improved performance and reduced the CO 2 footprint. The overall process reductions achieved exceed 2.24 million tonnes of CO 2 equivalents per year in smelters producing less than 3 million tonnes of aluminum per year.

Electrolyte Melt Compositions for Low Temperature Molten Carbonate Thermocells

“…As an integral part of the reaction process, the CO 2 gas emission is unavoidable but could be reduced. [6][7] Empowering the molten carbonate thermocells to operate below 450 °C will permit the access to avail the dual sources of waste heat and CO -rich off-gases from the industrial aluminum production cells. The lattice structure and ionic arrangement of the molten salts will change during the solid to liquid phase transition due to the dissociation of anion-cation pairs.…”

“…5 As an integral part of the reaction process, the CO 2 gas emission is unavoidable but could be reduced. 6,7 Empowering the molten carbonate thermocells to operate below 450 °C will permit the access to avail the dual sources of waste heat and CO 2 -rich off-gases from the industrial aluminum production cells.…”

“…Dissolved Al 2 O 3 reacts with the consumable carbon anodes to produce aluminum metal along with CO 2 gas: Nearly 50% of the input energy is lost as waste heat to the surroundings . As an integral part of the reaction process, the CO 2 gas emission is unavoidable but could be reduced. , Empowering the molten carbonate thermocells to operate below 450 °C will permit the access to avail the dual sources of waste heat and CO 2 -rich off-gases from the industrial aluminum production cells.…”

Matrix-Based Model of the Carbon Footprint Analysis for Thermal Power Generation in China

“…The UNEP/SETAC Life Cycle Initiative launched a project group on carbon footprint. The Japanese Ministry of Economy, Trade and Industry (METI) launched a carbon footprint trial project [5] and some other projects or researches in carbon footprint [6][7][8][9][10] . All these promotion try to serve an increasing market demand for "climate change relevant" information along supply chains and towards consumers.…”