Cleaner Production Assessment of the Aluminium Industry

Cleaner Production (CP) practices comprised environmental strategy perpetually applied in the production, processes, and services to bolster efficiency, safety, and environmental friendliness. Combining with the mindset of sustainable stocks and resources, this exercise of cleaner production provides advantages of minimum toxic wastes and residues. In this study, we prioritize this practice to be applied in the aluminum industry, of which cleaner production action has not yet been employed. This study aimed to assess the application of cleaner production in the aluminum industry. The method used is assessing cleaner production using the criteria of raw materials, production processes, water and wastewater, energy use, good housekeeping, solid waste and gas, human resources, and environmental performance. The assessment results of the cleaner production application indicate that the Mandiri industry type is generally at level 2 with a frequency of 13 industries. In general, SMAR’S is at level 3 with a frequency of 11 industries, and in the BLK industry, it is at level 2 with 11 industries. These results can be used as a recommendation for the government to increase cleaner production in the Jombang Regency.

Hydrogen-Rich Gas Produced by the Chemical Neutralization of Reactive By-Products from the Screening Processes of the Secondary Aluminum Industry

In the framework of the industry of secondary aluminum, the chemical neutralization of highly reactive materials that come from the pre-treatment screening processes of scraps (beverage cans and domestic appliances) was investigated through experiments in aqueous alkaline solutions. Metallic aluminum-rich by-products are classified, according to EU law, as dangerous waste, as they can potentially develop flammable gases capable of forming explosive mixtures with air. In this way they cannot be disposed of in landfills for non-hazardous wastes if chemical neutralization is not planned and performed beforehand. In this way, these experiments were mainly aimed at unraveling the oxidation rate and at quantifying the production of hydrogen-rich gases from the reactions of the metallic aluminum-rich by-products in a water-rich alkaline (liquid or vapor) environment. Reactions were carried out in a stainless-steel batch mini-reactor with metering and sampling valves, with the resulting gases analyzed by gas-chromatography (GC). The experimental setup was planned to avoid the following issues: (i) the corrosion of the reactor by the alkaline solution and (ii) the permeability of the system to hydrogen (i.e., possible leaks of H2), related to the fast kinetics and short duration of the reactions (which may hinder a pile-up-effect) between the solid by-products and the liquid. The procedure was defined by a controlled interaction process between metals and liquid, using NaOH to increase reaction rates. The experimental runs performed in the mini-reactor proved to be effective for eliminating the reactive metallic aluminum, reaching a maximum hydrogen production of 96% of the total gases produced in the experiments. The relations between gas generation (up to 55 bar of H2 in the experiments, which lasted for four days) and each specific parameter variation are discussed. All the obtained results can be transferred and applied to (i) the possible industrialization of the method for the chemical neutralization of these dangerous by-products, increasing sustainability and workplace safety, (ii) the use of the resulting hydrogen as a source of energy for the furnaces of the secondary aluminum industry itself, and (iii) new technological materials (e.g., “foamed geopolymers”), by using hydrogen as a foaming agent, coupled with aluminosilicate materials, during geopolymeric reactions.

The application of MFA for rural industrial symbiosis assessment

One of proposed strategies to solve current environmental challenges includes the industrial symbiosis. However, proper evaluation methods are required to measure the potential benefits of industrial symbiosis, one of those includes the material flow analysis (MFA). MFA develops a unified database and a Step-by-Step process starting from the input, process, and output process to clarify the distribution of waste and the recycling process in the aluminum industry. The aluminum industry is regarded as an energy-intensive and high-pollution industry. The development of industrial symbiosis in the aluminum industry has significantly reduced environmental pressures and facilitated green development and green industry. Home industries that process aluminum slag raw materials require high energy thereby generating high waste during the production process. The applied method includes material flow analysis (MFA). The MFA results indicated that the production elements of the aluminum slag industry consist of 11 elements ranging from raw materials, fuel, clean water, human resources, capital, production processes, production equipment, housekeeping, products produced, waste to waste utilization. Approximately 44% of the industry sold waste to other industries, 42% of the waste was reprocessed, and 14% of the aluminum industry stockpiles production was in the form of waste in open spaces. The industrial symbiosis in the aluminum industry was an open cycle, indicating that the symbiosis produces waste, which had not been fully utilized; but in fact, the waste had potential as a source of raw materials, energy, and materials in other industrial processes.

Increasing the Durability of Trimming Dies Used to Clean Anodes in the Aluminum Industry

Increasing the durability of trimming dies used to clean anodes is a very important goal in order to reduce the costs involved in obtaining aluminum. The research focused both on choosing an optimal material for the execution of trimming dies and on the application of technologies for plating active areas and, at the same time, on optimizing the geometric shape of the active area of the trimming die. In order to choose an optimal material from which to make the trimming dies, it was taken into account that they are usually made of X210Cr12 steel. In the stage of choosing an optimal material for the execution of the trimming dies, five steels were taken into account, namely: K105, K107, K110, K360, and K460. Analyses of the metallographic structure of the passage area were performed between the metal deposited by welding and the base material, demonstrating the fact that hot welding plating allows obtaining a more homogeneous metallographic structure compared to cold welding plating. The choice of new material was not a solution to increase the durability of the trimming die. Change in the trimming die geometry determined a reduction in deformations of about 13.8 times and of the equivalent stresses of about 7 times compared to those obtained in the case of the old trimming die. In addition, the durability of the trimming die with the new construction shape increases approximately three times compared to the trimming die with the old geometric shape. This demonstrates that the solution to increasing the durability of the trimming die is to adopt an optimal geometry of the active part at the expense of choosing an optimal material.

Compaction of Cohesive Granular Material: Application to Carbon Paste

Carbon-like materials such as the anode and the ramming paste play a crucial role in the efficiency of the Hall–Héroult process. The mechanical behavior of these materials during forming processes is complex and still ill-understood. This work aimed to investigate experimentally the mechanical behavior of a carbon paste used in the aluminum industry under different loading conditions. For this purpose, experiments consisting of (1) relaxation tests at different compaction levels, (2) quasi-static cyclic tests at several amplitudes, (3) monotonic compaction tests at varied strain rates, and (4) vibrocompaction tests at different frequencies were carried out. The obtained results highlight some fundamental aspects of the carbon paste behavior such as the strain rate’s effect on the paste compressibility, the hardening-softening behavior under cyclic loadings, the effect of cycling amplitude on the stress state and the paste densification, and the frequency effect on the vibrocompaction process. These results pave the way for the development of reliable rheological models for the modeling and the numerical simulation of carbon pastes forming processes.