Waste to Wealth Strategy: Preparation and Properties of Lightweight Al2O3-SiO2-Rich Castables Using Aluminum Dross Waste

Aluminum dross is a well-known industrial waste generated in the aluminium industry, and its recycling and reuse is still a worldwide issue. Herein, aluminum dross waste (ADW) was recycled to progressively replace the aggregate fraction of clay at 70, 75, 80, 85, and 90 wt% for the fabrication of Al2O3-SiO2-rich porous castable refractories. Their physical properties and mechanical behavior were assessed by the measurement of linear shrinkage rate, bulk density, apparent porosity, cold crushing strength, and thermal conductivity. The microstructure and phase evolutions were analyzed via scanning electron microscopy (SEM) and X-ray diffraction (XRD). The incorporation of 85 wt% of ADW allowed the development of a waste-containing conventional refractory castable with improved properties as compared to those of the other samples. The sustainable refractory castable exhibited decent thermal conductivity and physical and mechanical characteristics, and is suitable for application as reheating furnace lining. It is a “green” practice to partially replace the traditional raw materials with industrial waste in the manufacture of conventional refractory castables and provides environmental and economic benefits.

ROTARY FURNACE LINING TO REDUCE THERMAL STRESS

The aim of the study is to reduce the thermal stresses of the lining in the areas adjacent to the flare sintering zone of rotary kilns intended for the production of cement clinker. It is proposed to use a lining made of parallel rows of alternating chamotte and chromium-magnesite refractory products to reduce thermal stresses in the areas adjacent to the flare sintering zone by up to 20%, increase the service life of the lining by 1.1-1.2 times as a result of equalizing thermal stresses in the areas of the sintering zone. Optimization of the initial raw material mixture, in turn, made it possible to reduce the temperature of clinker formation and led to fuel savings.

Substantiation of refractory lining influence on the electric furnace efficiency for the production of ferronickel

Purpose. The purpose of the research is to substantiate the possibility of replacing existing MgO bricks with the MgO-C bricks due to their resistance to the slag aggressiveness of the electric furnace and the Si content in the resulting metal, which can have a positive effect on reducing the consumption of refractory materials. Methods. This research will be presented as the results of theoretical and experimental data determining the dependence of the electric furnace on the type of refractory material, walls construction, operating parameters and the electric furnace lining, that are expected to have a major impact on the cost output of production process. Findings. Based on the presented results, it has been revealed that MgO-C bricks are more effective in terms of preventing the furnace damage depending on refractory materials. Therefore, to optimize the production process, it is recommended to improve the composition of melted metal and slag, as well as to strengthen the control of the process parameters. Originality. Laboratory analyses are conducted in specialized laboratories, and the presented data have been obtained through the use of devices and equipment required for experimental research. Practical implications. The refractory materials are one of the main indicators of technical performance and production costs at NewCo Ferronickel in Kosovo. Therefore, the higher performance of the refractory lining will have a positive effect on the furnace durability and the quality of the final product.

Design and Construction of a Laboratory-Scale Direct-Current Electric Arc Furnace for Metallurgical and High-Titanium Slag Smelting Studies

A novel direct-current electric arc furnace (DC-EAF) was designed and constructed in this study for experimentally investigating high-titanium slag smelting, with an emphasis on addressing the issues of incomplete separation of metal and slag as well as poor insulation effects. The mechanical components (crucible, electrode, furnace lining, etc.) were designed and developed, and an embedded crucible design was adopted to promote metal-slag separation. The lining and bottom thicknesses of the furnace were determined via calculation using the heat balance equations, which improved the thermal insulation. To monitor the DC-EAF electrical parameters, suitable software was developed. For evaluating the performance of the furnace, a series of tests were run to determine the optimal coke addition under the conditions of constant temperature (1607 °C) and melting time (90 min). The results demonstrated that for 12 kg of titanium-containing metallized pellets, 4% coke was the most effective for enrichment of TiO2 in the high-titanium slag, with the TiO2 content reaching 93.34%. Moreover, the DC-EAF met the design requirements pertaining to lining thickness and facilitated metal-slag separation, showing satisfactory performance during experiments.

Effects of Cr2O3 Content on Microstructure and Mechanical Properties of Al2O3 Matrix Composites

Al2O3-Cr2O3 refractories are completely substitution solid solutions and can effectively resist slag erosion when used as an industrial furnace lining. In order to provide suitable chromium corundum refractory with excellent slag resistance and mechanical properties for smelting reduction ironmaking, Al2O3-Cr2O3 samples with different mass percentages (0, 10, 20, 30, 40 wt.%) of Cr2O3 were prepared by a normal pressure sintering process to study its sintering properties, mechanical properties, thermal shock resistance, and microstructure. The results of densification behavior showed that the introduction of Cr2O3 deteriorates the compactness, the relative density and volume shrinkage rate of the composite material decrease with the increase of the Cr2O3 content, and the apparent porosity increases accordingly. In terms of mechanical properties, the hardness, compressive strength, and flexural strength of Al2O3-Cr2O3 material decrease gradually with the increase of Cr2O3. After 10 and 20 thermal shock cycles, the flexural strengths of the samples all decreased. With the increase of Cr2O3 in these samples, the loss rate of flexural strength gradually increased. Considering the slag resistance and mechanical properties of the composite material, the Al2O3-Cr2O3 composite refractory with Cr2O3 content of 20–30% can meet the requirements of smelting reduction iron making kiln lining.

Deep Learning for the Prediction of Temperature Time Series in the Lining of an Electric Arc Furnace for Structural Health Monitoring at Cerro Matoso (CMSA)

Cerro Matoso SA (CMSA) is located in Montelibano, Colombia. It is one of the biggest producers of ferronickel in the world. The structural health monitoring process performed in the electric arc furnaces at CMSA is of great importance in the maintenance and control of ferronickel production. The control of thermal and dimensional conditions of the electric furnace aims to detect and prevent failures that may affect its physical integrity. A network of thermocouples distributed radially and at different heights from the furnace wall, are responsible for monitoring the temperatures in the electric furnace lining. In order to optimize the operation of the electric furnace, it is important to predict the temperature at some points. However, this can be difficult due the number of variables which it depends on. To predict the temperature behavior in the electric furnace lining, a deep learning model for time series prediction has been developed. Long Short Term Memory (LSTM), Gated Recurrent Unit (GRU), and other combinations were tested. GRU characterized by its multivariate and multi output type had the lowest square error. A study of the best input variables for the model that influence the temperature behavior is also carried out. Some of the input variables are the power, current, impedance, calcine chemistry, temperature history, among others. The methodology to tune the parameters of the GRU deep learning model is described. Results show an excellent behavior for predicting the temperatures 6 h into the future with root mean square errors of 3%. This model will be integrated to a software that obtains data for a time window from the Distributed Control System (DCS) to feed the model. In addition, this software will have a graphical user interface used by the operators furnace in the control room. Results of this work will improve the process of structural control and health monitoring at CMSA.

Effects of Grog Additions on Some Refractory Properties of Raw (Abusoro) Kaolin Clay Deposit for Furnace Lining

The influence of the weight of grog on some refractory properties of raw Abusoro clay samples found in Abusoro Village, Ondo State, Nigeria was evaluated. These samples were presented for refractory tests (apparent porosity, linear shrinkage, refractoriness, bulk density and cold crushing strength). The weights of the grog were varied from 20-40 wt. % in the blend. The chemical and microstructural examinations of the untreated alumino-silicate Abusoro clay samples indicated that they are abundant in silica, SiO2 (62.74wt. %) and alumina, Al2O3 (31.42wt. %). Other minor compounds found are Fe2O3 (1.43%), K2O (0.30%) with no trace amounts of MgO (0.00); therefore, they are regarded as alumino-silicate. Particular observation is made on MgO with zero amounts and the total of K2O + Na2O + MgO which are less than 2% in the clay samples. These results signify that the clay possesses high viability for manufacturing of refractory bricks, pulp and paper, ceramics, fertilizers, paint and cement. The performance evaluations of the refractory bricks measured indicated acceptable and satisfactory results vis-à-vis standard refractory properties for refractory fireclay bricks. However, the apparent porosity (43.2%) and CCS (21.21MPa) obtained for Abusoro clay sample at 30% weight of grog may as well be suitable for insulating refractory applications. The high apparent porosity could be an indication of high content of silicon oxide in the raw clay.

Study of gas consumption patterns for sheet glass enterprises

A study of the gas consumption modes of the subgroup “Enterprises of construction industry and architecture” of the regional gas supply system, as well as the production of sheet glass, which forms gas consumption in the subgroup by 94%, was carried out. The field type “daily gas consumption outside temperature” is set for the subgroup and the plant for production of sheet glass. This is a field with a weak dependence on the growth of daily gas consumption when outside temperature decreases and without an obvious stratification into temperature regions determined by the state of the heating system (“on” or “off”) and a significant vertical spread of daily gas flow at the same values of outside temperature. Additional factors affecting gas consumption were searched. The created database of 14 technological indicators over a seven-year period allowed to identify factors forming daily and annual gas consumption regimes using correlation-regression analysis. The importance of the “time worked by the line” factor and its contribution to the formation of the annual volume of gas consumption was assessed. Invention proposes a simplified method of estimating the rate of aging of furnace lining and wear of enclosing structures on the basis of a single-factor model of gas consumption from productivity by comparing the daily average annual values of specific gas consumption for sheet glass production with the same volume of output.