Slag Recovery Research Articles

Sustainable Green Industry Work: Recovery of Copper Slag with Mill Scale Leaching Reactant Optimized by Response Surface Methodology (RSM)

Sustainable Green Industry Work: Recovery of Copper Slag with Mill Scale Leaching Reactant Optimized by Response Surface Methodology (RSM)

Integration of CO2 sequestration with the resource recovery of red mud and carbide slag

Red mud and carbide slag, strongly alkaline solid wastes, are produced during the manufacturing of alumina and acetylene gas, respectively. Improper management of these wastes can pose significant environmental hazards. This study proposed a novel method for the collaborative treatment of red mud and carbide slag, enabling the recovery of constituent elements with CO2 sequestration. During the hydrochloric acid leaching process, Si was reclaimed as Si-rich residue, whereas Ti, Al, Ga, Fe, and Sc were stepwise recovered as Ti-rich product, Al/Ga-rich filtrate, and Fe/Sc-rich product via the subsequent hydrolysis, co-precipitation, and alkali leaching processes, respectively. Utilizing carbide slag to replace the energy-intensive NaOH for pH adjustment in the leaching solution resulted in a Ca2+ concentration of 21,922 mg/L in the filtrate after co-precipitation. Through further mineralization process, CO2 sequestration was achieved alongside the production of CaCO3 with the content reaching 98.5 % along with a whiteness of 94.4 %. Furthermore, by adjusting the experimental parameters in the mineralization process, controlled manipulation of the phase and morphology of the CaCO3 product could be achieved to meet various industry requirements. To summarize, the complete resource recovery of red mud and carbide slag was achieved in this study, demonstrating the promising potential in practical applications.

Process Optimization and Mechanism Study for Sulfur Recovery from High-Silica Phosphogypsum via Carbothermal Reduction Smelting.

Phosphogypsum produced from wet-processed phosphoric acid mainly consists of calcium sulfate dihydrate, which is an important sulfur resource. The traditional sulfuric acid and cement process based on phosphogypsum suffers from unstable cement quality owing to impurities such as phosphorus and fluorine and kiln ringing caused by the low-melting phase. This study investigated sulfur recovery and value-added utilization of liquid slag from high-silica phosphogypsum via carbothermal reduction smelting. A phosphogypsum ingredient (PGI) system was constructed by adding appropriate amounts of silica, alumina, magnesium oxides, and iron oxides to meet the production requirements of slag wool. Carbothermal reduction smelting experiments suggested that the temperature and C/S molar ratio significantly affected the desulfurization rate and phase structure of the slag. More than 97.44 wt % of sulfur could be recovered with a C/S molar ratio of 0.5-0.8 at 1300 °C or above in the molten state, and the molten slag was an amorphous magnesium-calcium-aluminosilicate. The PGI desulfurization mechanism is discussed based on the phase transformation and slag microstructure evolution.

Depletion of converter slags to waste in the Vanyukov furnace during pyrometallurgical copper production at JSC Almalyk MMC

The article shows the possibility of involving man-made formations in the pyrometallurgical production of copper in the form of slag and clinker-zinc production for the purpose of comprehensive extraction of non-ferrous and precious metals from them at Almalyk MMC JSC. Clinker, a technogenic waste from zinc production, contains a significant amount of reducing elements in the form of metallic iron and carbon, as well as gold in the amount of 2.3 g/t and silver 250 g/t. In research, clinker works as a reducer of magnetite contained in the converter slag during its depletion and in the process of depletion (reduction) of the converter slag, noble metals are extracted into matte, and then into blister copper up to 95-98%. Converter slags from copper production of Almalyk MMC JSC contain 2.0-3.5% copper, and they, as a circulating product, are depleted in a reverberatory furnace with copper extraction of 75%. To increase the yield of copper from converter slag in Vanyukov furnaces, it is necessary to first deplete the converter slag in reduction processes and then transfer it for processing. It was found that using clinker, a technogenic waste from zinc production with a particle size of +5 - -10 mm, the recovery of converter slag in a converter from magnetite to wustite using the developed technology in 10-15 minutes exceeded more than 50.0% (the amount of magnetite decreased from 21.9 % to 9.8%). As a result of processing recovered converter slags in the Vanyukov furnace, it was possible to reduce the copper content in converter slags of copper production from 2.2-3.5% to 0.58-0.72% in waste slag. To increase the yield of copper from converter slag in the reverberatory and Vanyukov furnaces, it is necessary to first deplete the converter slag in reduction processes and then transfer it for processing.

Combining organizational and product life cycle perspective to explore the environmental benefits of steel slag recovery practices

Sustainability in steel production is considered a global challenge which needs to be faced with coordinated actions. The aim of this study is to assess the environmental improvements of a steel mill in a circular economy perspective, through the Organizational Life Cycle Assessment (O-LCA) and the Product Life Cycle Assessment (P-LCA) methodologies. This study explores to what extent the improvements and the efforts to recover the steel slag can be detected using an organization perspective and making a comparison with the more traditional product perspective.The results obtained show that the case in which the steel slag is recovered has lower impacts than the case in which it is landfilled through both O-LCA and P-LCA applications and that the percentage variations are similar for 8 categories out of 10 demonstrating that for our case study, O-LCA and P-LCA can detect the efforts to recover slag similarly. Two categories, namely ADP-minerals&metals and EP-freshwater, are affected by the greater amount of metal and mineral raw materials needed if the slag is not treated and by the steel slag landfill disposal more significantly. What the results tell us is that the variations obtained for this study in the P-LCA application are greater than those obtained in O-LCA application, due to two methodological aspects, namely the application of allocation procedures and the choice of the system boundaries. Finally, it emerges that O-LCA methodology can detect environmental improvements of circularity practices, but the reduction of the impacts is less clear than P-LCA application. What is transferable is that O-LCA and P-LCA methodologies are not interchangeable to quantify the environmental benefits and address the efforts to improve a process in terms of circularity.

Thermodynamic analysis and experimental verification of the green and efficient recycling of waste sulfur slag by airtight sulfuration-vacuum distillation

Recovering valuable resources from waste sulfur slag is profoundly significant in terms of making profit and encouraging sustainable development within the tin industry. Sulfur slag is a hazardous waste, and a substantial amount of tin and cuprous sulfide is present in waste sulfur slag. However, tin and cuprous sulfide readily react to form stable metal compounds, which creates a barrier for effective sulfur slag recovery. The separation of copper-tin is essential for the efficient recovery and reuse of sulfur slag. In this paper, the physical composition and structural characteristics of the microstructure of sulfur slag were systematically characterized and confirmed. Thermodynamic calculations were then carried out to analyze the sulfuration reaction mechanism of tin and cuprous sulfide during the airtight sulfuration process and to study the volatilization of stannous sulfide and the decomposition properties of copper sulfide under vacuum conditions. Thermodynamic analysis showed that the products of tin and cuprous sulfide after being sulfided were SnS, SnS2, Sn2S3 and CuS, but they decomposed and existed in the form of SnS and Cu2S. According to the difference of saturated vapor pressure, SnS and Cu2S can be separated under the vacuum condition with high temperature. Finally, experiments were conducted to verify the reliability of the thermodynamic analysis, with good agreement between the two. The extraction purities of stannous sulfide and cuprous sulfide reached 97.87 % and 97.70 %, respectively. The direct yield of tin and copper were 99.66 % and 99.27 %, respectively. The separation efficiency of tin and copper was 99.81 %. The results confirmed that the airtight sulfuration-vacuum distillation method is a feasible alternative for high-value metal resource recovery and reuse from waste sulfur slag. This research contributes to the understanding of the recovery of metal resources from sulfur slag with the airtight sulfuration-vacuum distillation process, showing that it is a significant competitive alternative to existing sulfur slag recovery methods.

Multifunctional computational models to predict the long‐term compressive strength of concrete incorporated with waste steel slag

AbstractTo preserve the environment and natural resources, steel slag recovery conserves natural resources and makes landfill space available. Steel slag as a waste material has been partially substituted for fine (sand) and coarse aggregate in concrete (gravel). Compressive strength (CS) is the most significant mechanical attribute for all forms of concrete composites. To save time, energy, and money, it is essential to create accurate models for forecasting the CS of normal concrete (NC). In addition, it offers essential information for organizing the building work and details the ideal time to remove the formwork. In total, 338 data points were gathered, processed, and modeled in total. During the modeling approach, the most influential elements impacting the compressive strength (CS) of concrete with steel slag replacement were addressed. According to the modeling method, the most effective parameter which affects the compressive strength of normal concrete is the curing time. This research employed a Multi Logistic Regression model (MLR), an Artificial Neural Network (ANN), a Full Quadratic model (FQ), an M5P‐tree model, and an Interaction model to predict the compressive strength of normal strength concrete (CS ranged from 10 to 55 MPa) with steel slag aggregate replacement. According to data from the literature, the steel slag concentration enhanced the compressive strength. Based on evaluations with statistical tools like the objective (OBJ) function, the scatter index, and the Taylar diagram, the ANN model with the lowest root mean square error did better at predicting compressive strength than the other models.

Electrical conductivity, microstructures, chemical compositions, and systematic multivariable models to evaluate the effect of waste slag smelting (pyrometallurgical) on the compressive strength of concrete.

Concrete is a composite material widely used in construction. Waste slagsmelting(pyrometallurgical) (steel slag (SS)) is a molten liquid melt of silicates and oxides created as a by-product of steel production. It is a complex solution of silicates and oxides. Steel slag recovery conserves natural resources and frees up landfill space. Steel slag has been used in concrete to replace fine and coarse particles (gravel). Three hundred thirty-eight data points were collected, analyzed, and modeled. It was determined which factors influenced the compressive strength of concrete with steel slag replacement in the modeling phase. Water/cement ratio was 0.3-0.872, steel slag content 0-1196kg/m3, fine aggregate content 175.5-1285kg/m3, and coarse aggregate content (natural aggregate) 0-1253.75kg/m3. In addition, 134 data were collected regarding the electrical conductivity of concrete to analyze and model the effect of SS on electrical conductivity. The correlation between compressive strength and electrical conductivity was also observed. This research used a linear regression (LR) model, a nonlinear regression (NLR) model, an artificial neural network (ANN), a full quadratic model (FQ), and an M5P tree model to anticipate the compressive strength of normal strength concrete with steel slag aggregate substitution. For predicting the electrical conductivity, the ANN model was performed. The compressive strength of the steel slag was raised based on data from the literature. Statistical techniques like the dispersion index and Taylor diagram showed that the ANN model with the lowest RMSE predicted compressive strength better than the other models.

Electrical resistivity-Compressive strength predictions for normal strength concrete with waste steel slag as a coarse aggregate replacement using various analytical models

Concrete is a composite material that is highly used in construction fields. Steel slag (SS) is a molten liquidmelt of silicates and oxides, is a by-product of the steel-making process, and solidifies upon cooling. It is a complex solution of Silicates and Oxides. From an environmental standpoint and to save the environment and natural resources, steel slag recovery conserves natural resources and frees up space in landfills. Steel slag as waste materials has been used in concrete as a partial replacement with fine (sand) and coarse aggregate (gravel). A total of 338 data points were collected, analyzed, and modeled. The most effective factors affecting the compressive strength (CS) of concrete incorporated with steel slag replacement were considered during the modeling process. The cement content was ranged from 237.35 to 550 kg/m3, curing time 1–180 days, water/cement ratio ranged between 0.3 and 0.872, steel slag content varied between 0 – 1196 kg/m3, fine aggregate content ranged between 175.5 – 1285 kg/m3 and coarse aggregate content (natural aggregate) varied between 0 – 1253.75 kg/m3. Furthermore, 58 data were collected to analyze and model the effect of steel slag on the electrical resistivity (ER) of normal concrete. An Artificial Neural Network (ANN), a Multi Logistic Regression model (MLR), a Full Quadratic model (FQ), and an M5P-tree model were employed in this study to forecast the compressive strength of normal strength concrete (CS ranged between 10 and 55 MPa) with steel slag aggregate replacement, and Full quadratic model was applied to predict the ER of normal concrete (ER varied between 23.98 and 1440 Ω.m). Finally, the correlation between compressive strength and electrical resistivity was investigated through different models. Based on data from the literature, the steel slag content was increased the compressive strength and lowered the ER of concrete. According to statistical tool assessments such as objective function (OBJ), scatter index. Taylar diagram, the ANN model with the lowest root mean square error (RMSE) performed better than the other models in predicting the compressive strength. FQ model as a reliable mathematical model can be applied to forecast the ER of normal concrete due to the high coefficient of determination R2 is 0.91.

An experimental comparison: Horizontal evaluation of valuable metal extraction and arsenic emission characteristics of tailings from different copper smelting slag recovery processes

This study comprehensively investigated arsenic's enrichment, distribution, and characteristics in tailings. XRD and SEM-EDS characterized the phase and morphology of tailings from various smelting processes. At the same time, the embedding characteristics of arsenic in the ore phase were analyzed by EPMA. The differences between arsenic's leading ore phase carriers in different recovery processes were found. It was discussed that this phenomenon would be related to the element-binding ability and the precipitation priority of the ore phase. The occurrence state of arsenic was discussed by sequential chemical extraction experiments. The proportion of leachable arsenic is higher than the low-risk limit, whatever which smelting method is adopted, which leads to high environmental risk. In the experiment of comparing the leaching toxicity of tailings by different leaching methods, the arsenic concentration in the leaching solution of tailings recovered by the flotation method exceeds the specified safety range. Although the tailings after reduction smelting did not show high leaching toxicity, a large number of accumulations also would not represent absolute safety.

Recovery of Titania Slag and Iron from Semi-molten State Reduced Ilmenite Concentrate: Liberation Characteristics and Magnetic Separation

Recovery of Titania Slag and Iron from Semi-molten State Reduced Ilmenite Concentrate: Liberation Characteristics and Magnetic Separation

Research progress on granulation process of iron and steel slag

Efficient utilization of iron and steel slag is one of the important measures to achieve peak carbon emissions and carbon neutrality in the iron and steel industry. Improving the recycling rate of iron and steel slag has become an urgent problem to be solved by scholars and enterprises at home and abroad. Therefore, it is of great significance to continuously optimize the recycling process of iron and steel slag and waste heat recovery technology. By comparing and analyzing the advantages and disadvantages of different granulation processes for iron and steel slag, the disadvantages of using dry or wet granulation processes alone for iron and steel slag are pointed out in this paper. Then, a combined granulation process mode combining dry and wet processes is proposed to improve the processing efficiency of molten slag. The increase in resource conversion rate and the quality of granulated slag after primary granulating of iron and steel slag contribute to reducing the amount of slag to be treated secondarily. Furthermore, the energy consumption and pollutant emissions of slag secondary treatment will be decreased as well. It is intended to provide a reference for slag treatment technology and slag utilization rate expansion in iron and steel enterprises.

Techno-economic analysis of a novel full-chain blast furnace slag utilization system

As the main solid waste in the iron and steel industry, the waste heat recovery and comprehensive utilization of blast furnace slag had great significance for energy conservation and sustainable development. This paper proposed a novel full-chain blast furnace slag utilization system to solve the problem of waste heat recovery and high value-added production. Cascade recovery of slag waste heat was realized by using coal gasification reaction and the waste heat recovery ratio reached 73.61%. Meanwhile, two kinds of high value-added products of X-type zeolite and hydrotalcite-like compounds were synthesized simultaneously by using the beneficial components of blast furnace slag after fully recovering waste heat. Ultimately, the economic feasibility of the system was analyzed from two aspects of investment and profit. Under the reasonable economic assumptions, payback period of the project was 0.14 years, 10-year net present value was $ 326493.98 million, return on investment and internal rate of return were 737.74% and 312.82%, respectively. Through sensitivity analysis, the project could still be profitable in the production year under the condition that the sensitive factors of the system fluctuated within 40%. With great economic benefit and anti-risk ability, the novel full-chain blast furnace slag utilization system had potential in energy saving and emission reduction of iron and the iron and steel industry and the prospect of large-scale application.

Carbon Resource Recovery and Recycle of Fine Slag from Coal Water Slurry Gasification

Carbon Resource Recovery and Recycle of Fine Slag from Coal Water Slurry Gasification

Thermal-chemical conversion of sewage sludge based on waste heat cascade recovery of copper slag: Mass and energy analysis

Thermo-chemical conversion method can transform sewage sludge (abbreviated as SS) to bio-char with hydrogen-rich gas and has good prospects for development. In this research, copper slag was used as heat carrier and provide energy for conversion process of SS. A method of carbonization-activation waste heat cascade recovery technology system was designed. In this technology process, multi-stage endothermic chemical reactions absorb sensible heat from hot copper slag particles. Syngas, activated carbon (abbreviated as AC) and char are produced from SS. Mass and energy balance of this system were evaluated. The results showed that waste heat recovery efficiency and byproducts' additional value were improved by this method comparing with traditional water quenched method. Increasing heat quantity of carbonization process can improve system's energy recovery ratio. In theory, under the optimal condition (T2 = 700 °C, T3 = 200 °C), waste heat recovery ratio and exergy recovery ratio reach 90.8% and 94.9%, respectively.

Techno-Economic Analysis of a Novel Full-Chain Blast Furnace Slag Utilization System

As the main solid waste in the iron and steel industry, the waste heat recovery and comprehensive utilization of blast furnace slag had great significance for energy conservation and sustainable development. This paper proposed a novel full-chain blast furnace slag utilization system to solve the problem of waste heat recovery and high value-added production. Cascade recovery of slag waste heat was realized by using coal gasification reaction and the waste heat recovery ratio reached 73.61%. Meanwhile, two kinds of high value-added products of X-type zeolite and hydrotalcite-like compounds were synthesized simultaneously by using the beneficial components of blast furnace slag after fully recovering waste heat. Ultimately, the economic feasibility of the system was analyzed from two aspects of investment and profit. Under the reasonable economic assumptions, payback period of the project was 0.14 years, 10-year net present value was $ 326493.98 million, return on investment and internal rate of return were 737.74% and 312.82%, respectively. The sensitive factors of the system fluctuated within 40% through sensitivity analysis. The project could still be profitable in the production year. With great economic benefit and anti-risk ability, the novel full-chain blast furnace slag utilization system had potential in energy saving and emission reduction.

An Experimental Comparison: Horizontal Evaluation of Valuable Metal Extraction and Arsenic Emission Characteristics of Tailings from Different Copper Smelting Slag Recovery Processes

An Experimental Comparison: Horizontal Evaluation of Valuable Metal Extraction and Arsenic Emission Characteristics of Tailings from Different Copper Smelting Slag Recovery Processes

Experimental investigation on granulation characteristics and waste heat recovery of molten slag in gas quenching dry granulation technique

The gas quenching dry slag granulation technique is one of the most promising slag treatment methods due to realize efficient waste heat recovery as well as high value-added resource utilization. To better understand the granulation characteristics and to achieve high waste heat recovery efficiency in the gas quenching granulation technique, high temperature experiments were performed with different airflow velocity and different molten slag mass flow rate. Particle average diameter, particle size distributions, and fiber mass fraction were in-depth studied for the granulation characteristics. The results indicated that the average diameter decreased with increasing airflow velocity and with decreasing the mass flow rate. The dimensionless diameter empirical formula was presented according to the experimental data. The particle size distributions were mainly concentrated in 1–3 mm. The fiber mass fraction decreased with increasing airflow velocity, but it increased when the airflow velocity exceeds 550 m·s−1 at lower mass flow rate. The higher waste heat recovery rate can be obtained with smaller particle diameter and lower fiber mass fraction. The maximum of waste heat recovery rate can reach 59.55% with the airflow velocity of 550 m·s−1 at the mass flow rates of 4.2 kg·s−1, which is the most ideal working condition.

Efficiency improvements of the CO-H2 mixed gas utilization related to the molten copper slag reducing modification

Molten reduction to release the value metals are the necessary step in the copper slag recovery process. How to effectively choose and utilize the reducing agents has an extremely important significance. In the research, molten reductions with the CO-H2-Ar mixed gases are investigated. De-oxidation amounts and de-oxidation rates maintain stability first and then decrease with the increase of CO/H2 ratios. They are all much higher than those of pure CO or H2 due to the water-gas shift reaction. The magnetite phase decreased gradually with the decrease of CO/H2 ratios, and some pure ferrous phase can generate in the slag as the ratios are less than 1:1. Otherwise, the apparent rate constants, the reaction orders and the activation energies for the various CO/H2 ratios are also measured. The results illustrate that the reaction process will vary with the variety of mixed gas compositions.

Simulation of primary breakup of molten slag in the gas quenching dry granulation process

Gas quenching dry slag granulation process is an energy-saving environmental protection method for waste utilization and waste heat recovery of molten slag, and the molten slag is broken up by supersonic airflow into droplets in this process. This paper performed the numerical investigations on the breakup behavior of slag by the coupled level-set and volume of fluid (CLSVOF) methodology and gain a deep insight into the breakup mechanism of the primary breakup and influence of gas Weber number (We) and liquid Reynolds number (Re) on the primary breakup. The results indicated that the primary breakup include flat film breakup and spherical cap film breakup, the both are typical perforation breakup; Aerodynamic force cause K-H (Kelvin Helmholtz) instability, K-H surface waves are the root cause of film breakup; The wavelength and the film thickness decrease with increasing We which is conducive to reducing the ligament diameter; The wavelength and the film thickness decrease first and then increase with increasing Re which is optimum in the range of 1068–1280; The empirical formula of the ligament diameter is obtained. The ligament diameter decrease with increasing airflow velocity and slag density and increase with increasing slag mass flow rate and slag viscosity.