Recycling Of Dross Research Articles

Recovery and utilization of zinc dross for sacrificial anode cathodic protection of steel structures

Zinc dross is highly zinc-rich industrial waste produced during galvanization of steel. It is a byproduct of the reaction between molten zinc and loose iron particles in a molten zinc bath. Generally, 10–20% of galvanized zinc is converted into zinc dross. This work proposes a unique way of recycling of dross into a high value sustainable resource material leading to development of sacrificial anode used in cathodic protection of steel. The electrochemical behavior was studied in 3.5 wt% NaCl solution. The anode performance test was performed as per the standard DNV-RP-B401 in an artificial seawater solution. The performance parameters, (closed circuit potential (CCP), anode efficiency, and consumption rate) of the recovered zinc anode from dross, are close to the commercial zinc anodes. It satisfies the required anode criteria. Hence, the recovered zinc anode from dross could be used as a sacrificial anode for the cathodic protection of steel structures.

A hydrometallurgical perspective of aluminium dross recycling

To meet the objective of recovering aluminium from aluminium dross, it is essential to recycle it and save natural resources for posterity. Aluminium dross, a waste generated in an enormous quantity, is formed over the top surface of the molten bath when the surrounding oxygen comes into contact and forms a thick semi-solid layer of oxide. Pure metallic aluminium, which is entrapped within the oxides, is extracted using three different routes i.e., Pyrometallurgy, hydrometallurgy and hydrothermal. Metallic aluminium is recovered using the pyrometallurgical route by melting dross in a rotating furnace. In hydrometallurgy, chemical treatments of dross ensures the synthesis of a wide range of products. Newly developed technique like hydrothermal is used to produce zeolites, molecular sieves, and many other useful products. Apart from the solid products, gases like H2, NH3 and CH4 are produced by recycling dross when the Al-water reaction takes place in the presence of acids or alkalis. The present study comprises major aspects of dross recycling via the hydrometallurgical route.

Element Distribution in Oxygen-Enriched Bottom-Blown Smelting of High-Arsenic Copper Dross

An oxygen-enriched bottom-blown smelting process has been proposed to extract valuable metals and remove arsenic from high-arsenic copper dross. PbO, PbS, Cu2S, and Cu5As2 were the main components of the copper dross. Iron scrap, calcium carbonate, coke, and silica were added as flux in the smelting process. Mineralogical analysis revealed that the smelting products were ferrous calcium silicate slag, lead copper matte (PbS and Cu2S), speiss (Cu3As), crude lead (Pb), and dust. Approximately 35% of copper distributed to lead copper matte, while 56% of copper and 75% of arsenic reported to speiss. The Cu concentrated in economical products for further extraction reached 91%, 87% of Pb was directly recovered to crude lead, and the As removed to dust was 4–6%. The technology was first developed and applied in industry by Henan Yuguang Gold and Lead Group Co., LTD, providing an efficient approach and production experience for copper dross recycling.

The Integrated Fuzzy AHP and Goal Programing Model Based on LCA Results for Industrial Waste Management by Using the Nearest Weighted Approximation of FN: Aluminum Industry in Arak, Iran

The worldwide recycled aluminum generation is increasing quickly thanks to the environmental considerations and continuous growing of use demands. Aluminum dross recycling, as the secondary aluminum process, has been always considered as a problematic issue in the world. The aim of this work is to propose a methodical and easy procedure for the proposed system selection as the MCDM problem. Here, an evaluation method, integrated FAHP, is presented to evaluate aluminum waste management systems. Therefore, we drive weights of each pair comparison matrix by the use of the goal programming (GP) model. The functional unit includes aluminum dross and aluminum scrap, which is defined as 1000 kilograms. The model is confirmed in the case of aluminum waste management in Arak. For the proposed integrated fuzzy AHP model, five alternatives are investigated. The results showed that, according to the selected attributes, the best waste management alternative is the one involving the primary aluminum ingot 99.5% including 200 kg and the secondary aluminum 98% (scrap) including 800 kg, and beneficiation activities are implemented, duplicate aluminum dross is recycled in the plant, and finally it is landfilled.

Processing of Aluminum Dross: The Birth of a Closed Industrial Process

This is the history of a modern aluminum dross recycling company, from its beginnings in the last years of the twentieth century to the present day. The vision of the founders was to build a local recycling plant and take full responsibility for sensitive environmental issues by recycling aluminum dross locally rather than shipping it abroad. The paper tells the history of the company from the environmental perspective, and gives an overview of some of the challenges and the decisions that followed from this vision, for instance the selection of technology. The company developed a closed industrial process for the recycling of aluminum dross, and the paper discusses some of their laboratory experiments and industrial trials. An important milestone has now been reached as the process in its present form is recognized by the environmental authorities in the country. Furthermore, it seems realistic that in the near future the final product from this process will be comparable to the product delivered in the processing of salt cake in specialized chemical plants, but at a fraction of the cost.

New Porous Material Made from Industrial and Municipal Waste for Building Application

The aim of this study was to find a new method for usage of the hazardous waste coming from recycling industry. Two hazardous wastes – aluminium recycling final dross or non-metallic product (NMP) and lead – silica glass (LSG) were investigated. It is generally considered that NMP is a process waste and subject to disposal after residual metal has been recovered from primary dross. NMP is impurities which are removed from the molten metal in dross recycling process and it could be defined as a hazardous waste product in aluminium recycling industry. LSG comes from fluorescence lamp recycling plant and could be classified as hazardous waste due to high amount of lead in the composition and re-melting problems. The new alkali activated material, which can be defined as porous building material, was created. Composition of this material consisted of aluminium recycling waste, recycled fluorescent lamp LSG, sintered kaolin clay as well as commercially available alkali flakes (NaOH) and liquid glass (Na2SiO3 + nH2O). Physical and mechanical properties of the obtained material were tested. Density of the obtained material was from (460 – 550) kg/m 3 and the total porosity was from 82 % – 83 %. The compressive strength of the material was in range from 1.1 MPa to 2.3 MPa. The thermal conductivity was determined. The pore microstructure was investigated and the mineralogical composition of porous material was determined.

Recycling of lead solder dross, Generated from PCB manufacturing

The main purpose of this work is to analyze lead solder dross, a waste product from manufacturing of printed circuit boards by wave soldering, and to develop an effective and environmentally sound technology for its recycling. A methodology for determination of the content and chemical composition of the metal and oxide phases of the dross is developed. Two methods for recycling of lead solder dross were examined—carbothermal reduction and recycling using boron-containing substances. The influence of various factors on the metal yield was studied and the optimal parameters of the recycling process are defined. The comparison between them under the same parameters-temperature and retention time, showed that recycling of dross with a mixture of borax and boric acid in a 1:2 ratio provides higher metal yield (93%). The recycling of this hazardous waste under developed technology gets glassy slag and solder, which after correction of the chemical composition can be used again for production of PCB.

Process of aluminum dross recycling and life cycle assessment for Al-Si alloys and brown fused alumina

In 2008, around 596 000 t of aluminum dross was generated from secondary aluminum industry in China; however, it was not sufficiently recycled yet. Approximately 95% of the Al dross was land filled without innocent treatment. The purpose of this work is to investigate Al dross recycling by environmentally efficient and friendly methods. Two methods of Al dross recycling which could utilize Al dross efficiently were presented. High-quality aluminum-silicon alloys and brown fused alumina (BFA) were produced successfully by recycling Al dross. Then, life cycle assessment (LCA) was performed to evaluate environmental impact of two methods of Al dross recycling process. The results show that the two methods are reasonable and the average recovery rate of Al dross is up to 98%. As the LCA results indicate, they have some advantages such as less natural resource consumption and pollutant emissions, which efficiently relieves the burden on the environment in electrolytic aluminum and secondary aluminum industry.

Comparison of salt-free aluminum dross treatment processes

Dross is an unavoidable by-product of the aluminum production. It forms at the surface of the molten metal as the latter reacts with the furnace atmosphere. Depending on the process, it contains, on average, about 50% free aluminum metal dispersed in an oxide layer. Since the aluminum production is highly energy-intensive, dross recycling is very attractive from both the energy and the economic standpoints. The conventional recycling process using salt rotary furnaces is thermally inefficient and environmentally non-acceptable because of the production of salt slags. Several salt-free dross treatment processes have been proposed in the last few years, their operation, energy consumption and metal yield will be described in detail and compared in the present paper.

Dross treatment in a rotary arc furnace with graphite electrodes

Aluminum baths are always covered with a layer of dross resulting from the aluminum surface oxidation. This dross represents 1–10% of the melt and may contain up to 75wt.% aluminum. Since aluminum production is highly energy intensive, dross recycling is very attractive from both energy and economic standpoints. The conventional recycling process using salt rotary furnaces is thermally inefficient and environmentally unacceptable because of the production of salt slags. Hydro-Quebec has developed a new technology using a rotary arc furnace with graphite electrodes. This process provides aluminum recovery rates of 80–90%, using a highly energy efficient, environmentally sound production method.

Recycling of metals from waste with thermal plasma

Environmental regulations and quality demands require clean and efficient processes for recovery of materials from scrap and waste. Thermal plasma is a heat source for recovering metals pyrometallurgicaly. High energy density, high temperatures and flexibility in the plasma gases employed are the basic advantages of plasma. Plasma methods are gaining importance for scrap melting of reactive and refractory metals and alloys, aluminum containing wastes, steel plant wastes and recovery of metals from spent catalysts. In the paper, some metal-containing wastes in different scrap and waste categories, related problems, goals and recycling furnace concepts will be presented and discussed: titanium scrap consolidation and refining (Plasma Cold Hearth Furnace), aluminum dross recycling (Plasma Rotating Hearth Furnace), MMC's, spent catalyst recycling and dust treatment. The paper also summarizes recent developments and some future aspects of plasma metal recovery from scrap and waste.