Thermodynamic modeling of zinc recovery from ferrous metallurgy sludge

Ferrous metallurgy enterprises continuously fill dumps with steelmaking and blast furnace sludge with high zinc content. Sludge occupying significant territories of enterprises is not involved in production and harms the environment. Since zinc leads to the formation of deposits in the blast furnace, manufacturers cannot involve this sludge in sinter processing. In addition, working with sludge can lead to problems such as decrease in iron content in the sinter, decrease in productivity of sintering machines, and increase in fluctuations in the sinter chemical composition. At the same time, zinc-containing sludge can become a valuable secondary product. Zinc remains a scarce metal, which encourages the development of technologies for processing zinc-containing materials. Extraction of zinc from sludge is difficult because it is not in oxide, but in sulfate or sulfide forms. In this paper, the possibilities of zinc extraction from sludge using the FactSage software package are evaluated. The authors present results of thermodynamic calculations of the possibility of zinc extraction from four types of sludge from two Russian ferrous metallurgical plants - EVRAZ NTMK and MECHEL. The data of chemical and phase analyses of this sludge are considered, as well as simulated graphs of zinc extraction dependencies from them. The graphs were built on basis of the received data from FactSage package. Addition of the reducing agent to the sludge varied, as well as temperature of the process. In addition, the possibility of abandoning carbon as a reducing agent was evaluated. To save the reducing agent, an optimal mixture of the company's sludge was selected, in which coke consumption can be minimized. © 2022 National University of Science and Technology MISIS. All rights reserved

Reducing the carbonitride formation risk with increasing titanium dioxide content in the blast furnaces charge of JSC EVRAZ NTMK

Analyse of the blast furnace charge chemical content changing with the JSC EVRAZ NTMK raw materials base alteration was carried out. That expected change would result in TiO2 content increasing in the blast furnace slags. That increasing would lead to carbonitride formation in the upper levels of the blast furnace, which reduce technical parameters of the blast furnace operation by reducing effective volume of the furnace and derange regular charge moving. Possible ways of that problem solving was shown. It was proposed the complex technology, that affect 3 technological stages: agglomeration, blast furnace process and out-of-furnace treatment of steel. Converting of TiO2 into CaO•TiO2 allows to delay carbonitride formation due to increasing required temperature for that process. In that case, carbonitride formation would move to the tuyere zone of blast furnace, where it increase lining durability. The proposed technology was industrially tested, and the main idea was proved. Few problems were found during industrial tests, but theoretical solving of them was proposed. © Published under licence by IOP Publishing Ltd

The possibility evaluation of zinc sulphate forms extraction from sludge of PJSC EVRAZ NTMK with following metalloflux obtaining

EVRAZ NTMK JSC has significant amount of blast furnace sludges, that accumulated in dumps. Chemical and phase analysis of that sludges was carried out. It has shown significant amount of zinc sulphate, which prevents such sludge utilization in a blast furnace. Moreover, zinc sulphate requires a high temperature unit for recycling by common schemes. The possibility of zinc sulphate conversation into oxidized zinc with simultaneous metallized residue obtaining under the common for Waelz process temperatures was confirmed in laboratory. The obtained during laboratory experiments metallized residue is suitable for using in blast furnace as charge addition. The results of a thermodynamic analysis of the zinc sulphate conversion to oxide and the physicochemical basis for the extraction of such zinc forms are presented. Theoretical calculations and laboratory experiments confirmed that sludges with zinc sulphate could be suitable materials for blast furnace. But, sludges of different processes allow to obtain fired briquettes with different physical properties. © Published under licence by IOP Publishing Ltd.The reported study was funded by RFBR according to the research project 18-29-24064\18

THE POSSIBILITY OF SILICATE PRODUCT AND PIG IRON OBTAINING FROM THE SLAG TECHNOGENIC FORMATIONS

The work reviews the possibility of using EAF and ladle furnace slags to obtain pig iron and Portland clinkerduring the electric-arc melting

Changes in phase composition of soderites of the bakal deposit at heating

The article presents the results of a study of formation mechanism of magnesia-ferrite when heated siderites of the Bakal deposit with different iron oxide content in an inert and oxidizing atmosphere. It was established that in the case of firing in an inert atmosphere, the decomposition of siderite with high iron content begins at a lower temperature and the enthalpy of such decomposition is less. This effect can be explained by the different phase composition of the samples. The main phases formed under conditions of oxidative firing are hematite and magnesia-ferrite. The amount of hematite and magnesia-ferrite produced in the samples with different iron oxide content during firing in an oxidizing atmosphere is different. Siderite with high content of iron oxides contains more hematite in the firing products than magnesia-ferrite, and siderite with a low content of iron oxides contains more magnesia-ferrite in the firing products than hematite. Formed under conditions of oxidative firing magnesia-ferrites are solid solutions and differ in the degree of substitution of iron and magnesium ions. In siderites with high content of iron oxides, the degree of substitution of magnesium ions with iron ions is greater than in samples with a low content of iron oxides. Since the siderites of the Bakal deposit are poor ore formations, the considerable amount of magnesia-ferrite formed in them during firing makes it difficult to separate silicate and iron-oxide firing products by traditional enrichment methods. Wustite in the products of oxidative firing is not detected, because under these conditions it is in a metastable state and in the presence of a weakly oxidizing atmosphere is converted into magnetite. The scientific novelty is the explanation of the mechanism of siderite decomposition and the description of products of such decomposition. Understanding of the mechanism of decomposition of siderite from the Bakal deposit made it possible to develop the technology of reductive firing of siderite to facilitate separation of its products, and which consists in the regulation of the phase composition of silicate products of reductive firing, ensuring the collapse of magnesia-ferrite and output of iron oxide in a separate phase. The developed technology can be used to provide high-quality enrichment of siderite from the Bakal deposit. © 2018, National University of Science and Technology MISIS. All rights reserved