Search Results (8)

Millions of tons of slag and clinker can be found in the dumps of enterprises across the Republic of Kazakhstan. The goal of this project is to create a technology that conserves energy in waste treatment. The novelty of the work is the discovery of a new phenomenon, which shows that in the melt layer, there are two reactions opposite in direction and intensity: slow reactions of the decomposition of complex components into simple molecules and rapid responses of the formation of complex components from simple molecules. The dominance of one of the two reactions affects the process’s fuel consumption. Using this phenomenon, a melting reactor was created, which will reduce specific fuel consumption by 3–4 times compared to a Waelz kiln. It is shown that using a new method of CO₂ decarbonization by zinc, it is possible to ensure the production of zinc sublimates and cast stone products and the full neutralization of CO₂. The lowest market potential only for Achisai dump clinker would be around USD 125,600,000 if the cost of commercial clinker sublimates is USD 800/t. The expected net profit would be USD 4,466,039/y. Full article

In the hydrometallurgical process of zinc production, the residue from the leaching stage is an important intermediate product and is treated in a Waelz kiln to recover valuable metals. To ensure optimal results during the Waelz kiln process, it is necessary to pre-treat the residues by drying them first due to their higher water content. This work studies the residue’s drying process using microwave technology. The study results indicate that microwave technology better removes the residue’s oxygen functional groups and moisture. The dehydration process’s effective diffusion coefficient increases as the microwave’s heating power, the initial moisture content, and the initial mass increase. The Page model is appropriate for imitating the drying process, and the activation energy of the drying process for the residues is −13.11217 g/W. These results indicate that microwave technology efficiently dries the residues from the leaching stage. Furthermore, this study provides a theoretical basis and experimental data for the industrial application of microwave drying. Full article

Waelz slag is an iron-containing waste generated during electric arc furnace (EAF) dust processing in a rotary kiln named the Waelz process. This study focuses on the reduction smelting of the Waelz slag to produce iron-based alloy. The thermodynamic simulation using FactSage 8.0 software was carried out to predict temperatures of the metal and slag obtained as well as their compositions. Based on the simulation results, reduction smelting experiments were performed on a laboratory scale using two approaches, with and without preliminary froth flotation of carbon, respectively. The experiments have confirmed the technological possibility of reduction smelting of the Waelz slag from EAF dust processing. The approach using preliminary flotation of carbon and reduction smelting at 1500 °C resulted in high-copper cast iron production, while the approach without flotation, where the Waelz slag was smelted at 1650 °C with the addition of SiO₂ flux, led to obtaining low-silicon ferrosilicon with high Cu content, as well as slag attractive for construction industry. Full article

The utilization of end-of-life batteries (including Zn-C and alkaline batteries) is one of the areas that need to be perfected in order to provide environmental and human safety as well as to contribute to closing the material loop, as described in the EU Green Deal. The presented study shows the environmental impacts of the two selected pyrometallurgical technologies (processing of the black mass from waste Zn-C and alkaline batteries as an additive to an existing process of the recycling of steelmaking dust and treatment of the black mass as the primary waste material, both processes performed in a Waelz kiln). The presented LCA-based study of the recycling of end-of-life Zn-C and alkaline batteries focused on terrestrial ecotoxicity can be a useful tool in the process of the development of a circular economy in Europe, as it provides a multi-disciplinary overview of the most important environmental loads associated with the described recycling technologies. Therefore, the goal of the presented study was to compare the environmental performance (utilizing LCA) of two different metallurgical processes of black mass utilization, i.e., the conventional method utilizing black mass as a co-substrate and the newly developed method utilizing black mass as a primary substrate. Full article

The prospects of processing blast furnace and steelmaking sludge using the Waelz process in a laboratory rotary kiln, is shown. The influence of different processing temperatures, furnace atmosphere and the type of reducing agents on the level of zinc reduction from sludges was analyzed. In general, the blast furnace sludge contains a high portion of iron (approx. 48 wt.%) and can be reused as a charge after satisfactory zinc reduction. It was found that N- atmosphere and a high content of the graphite or coke oven reducing agent in combination with high temperature can reduce the content of Zn in the sludge to 0.08 wt.% at 1200 °C for a mixture of steelmaking and blast furnace sludge. A significant reduction in the Zn content to 0.66 wt.% occurs at 1100 °C. The content and type of reducing agent plays an important role; graphite has shown a better reducing ability compared to coke oven dust. When nitrogen is used, zinc is reduced even without an additional reducing agent, since the carbon contained in the sludge is made use of for the reduction. In an air atmosphere, without the use of a reducing agent, there was no reduction in the Zn content. Full article

The recycling of zinc in the Waelz process is an important part of the efficient use of resources in the steel processing cycle. The pyro-metallurgical processing of zinc-containing wastes takes place in a Waelz rotary kiln. Various measured variables are available to monitor the process. The temperature of the kiln-shell is analyzed by an infrared kiln-shell-scanner. In this paper, methods are presented which eliminate external weather-related disturbances on the temperature measured by the kiln-shell-scanner using a weather model and which extend the monitoring of the regularly necessary melting process to remove accretions. For this purpose, an adapted sigmoid estimation is introduced for the melting process, which provides new information about the current process status and a forecast of the further development of the melting process. As an assistance system for the plant operator, this enables an efficient execution of the melting process and reduces downtimes. Full article

(1) Background: The importance of Zinc in today’s world can hardly be exaggerated—from anticorrosion properties, to its durability, aesthetic, and even medicinal uses—zinc is ever-present in our daily lives ever since its discovery in ancient times. The natural, essential, durable, and recyclable features of zinc make it a prized material with uses in many applications across a wide array of fields. The purpose of this study was to compare two life cycle impact assessments of zinc production by using two different main raw materials: (A) zinc concentrates (sulfide ore) and (B) Waelz oxides (obtained through recycling existing imperial smelting process furnace slags). The Waelz oxide scenario was based on a case study regarding the existing slag deposit located in Copsa Mica town, Sibiu county, Romania. (2) Methods: consequential life cycle impact assessment methods were applied to each built system, with real process data obtained from the case study enterprise. (3) Results: Overall, the use of slags in the Waelz kiln to produce zinc oxides for use in the production of zinc metal is beneficial to the environment in some areas (acidification, water, and terrestrial eutrophication), whereas in other areas it has a slightly larger impact (climate change, photochemical ozone formation, and ozone depletion). (4) Conclusions: The use of slags (considered a waste) is encouraged to produce zinc metal, where available. The results are not absolute, suggesting the further need for fine-tuning the input data and other process parameters. Full article

During the remelting of automobile scrap in the electric arc furnace steelmaking process, a dust is generated. This dust contains significant amounts of zinc, iron, and lead and in some cases, copper and nickel. However, the recovery of these metals is difficult, because of the complex chemical and physical characteristics of the dust. Numerous pyrometallurgical, hydrometallurgical and hybrid processes have been devised and tested for metal recovery, but only the Waelz rotary kiln process has achieved significant commercialisation. One potential process, which has received little attention in the literature, is the pyrometallurgical sulphation of the dust. In the present research, a high temperature thermodynamic model has been developed using HSC^® Chemistry 7.1, to investigate the sulphation of the dust. The effects of process parameters on the conversion of the various metals into sulphates were studied. At a temperature of 600 °C, almost one hundred percent of the zinc could be converted into zinc sulphate, while about ninety-five percent of the iron could be retained as hematite. In addition, several low cost, potential sulphating reagents were evaluated. Full article