Decomposition Of Limestone Research Articles

Decomposition Behavior of Limestone Powder in Converter Flue Gas: Effect of Fe‐Oxide Dust on Calcium Ferrite Formation

To improve the utilization level and energy conversion efficiency of converter flue gas, a novel technology is proposed for the online production of slagging and dephosphorization agent by utilizing the waste heat of converter flue gas. Herein, the effects of Fe‐oxide dust in converter flue gas on the phase composition and microstructure of decomposed product and decomposition degree are investigated by high‐temperature drop tube furnace experiment and thermogravimetric experiment to clarify the influencing mechanism of Fe‐oxide dust on limestone powder decomposition. The results show that Ca2Fe2O5 is formed during limestone decomposition in the flue gas with Fe‐oxide dust, and the increase of Fe‐oxide dust content promotes the decomposition reaction of limestone powder and formation of calcium ferrite. With the Fe‐oxide dust content increasing from 10% to 30%, the decomposition degree increases from 80.1% to 96.2% and the proportion of Ca2Fe2O5 increases from 6.35% to 35.90%. Moreover, FeO in the dust reacts with both CaCO3 and CaO completely to form calcium ferrite with the presence of external oxygen gas in converter flue gas, whereas FeO has no significant effect on the decomposition of CaCO3 in an inert atmosphere and no Ca2Fe2O5 is formed.

First-principle modeling of parallel-flow regenerative kilns and their optimization with genetic algorithm and gradient-based method

We present a one-dimensional first-principle model for parallel-flow regenerative kilns that accounts for the most important effects. These include the kinetics and thermal effects of the limestone decomposition as well as the heat transfer between the gaseous and solid phases. The model consists of two coupled equation systems for the upper and lower part of the kiln. The results of the model are validated qualitatively and are used to train an artificial neural network that predicts the conversion and the temperature in the crossover channel. The artificial neural network performs very well with values of the root mean squared error that are two to three orders of magnitudes lower than the range covered within the data. Finally, we use a genetic algorithm to optimize the feed mass flows such that the conversion and the fuel efficiency are improved in a Pareto-optimal manner. The results are compared to those of a gradient-based optimization method, which shows the usefulness and validity of the approach with the genetic algorithm.

Valorization of Biomass and Industrial Wastes as Alternative Fuels for Sustainable Cement Production

The cement industry contributes around 7% of global anthropogenic carbon dioxide emissions, mainly from the combustion of fuels and limestone decomposition during clinker production. Using alternative fuels derived from wastes is a key strategy to reduce these emissions. However, alternative fuels vary in composition and heating value, so selecting appropriate ones is crucial to maintain clinker quality and manufacturing processes while minimizing environmental impact. This study evaluated various biomass and industrial wastes as potential alternative fuels, characterizing them based on proximate analysis, elemental and oxide composition, lower heating value, and bulk density. Sawdust, pecan nutshell, industrial hose waste, and plastic waste emerged as viable options as they met the suggested thresholds for heating value, chloride, moisture, and ash content. Industrial hose waste and plastic waste were most favorable with the highest heating values while meeting all the criteria. Conversely, wind blade waste, tire-derived fuel, and automotive shredder residue did not meet all the recommended criteria. Therefore, blending them with alternative and fossil fuels is necessary to preserve clinker quality and facilitate combustion. The findings of this research will serve as the basis for developing a computational model to optimize the blending of alternative fuels with fossil fuels for cement production.

Multiscale modeling of an entrained flow solar calciner for thermochemical energy storage via calcium looping

Calcium looping has been proposed as an alternative route addressing the intermittent nature of solar energy in terms of thermochemical energy storage, with the added benefit of CO2 capture. In this work, a multiscale approach aims to predict and optimize the performance of a pilot-scale solar calciner operating at realistic conditions, incorporating a diffusion–reaction model with multiphase flow considerations in a downer reactor. The model has been successfully validated with experimental data from the literature studying the effect of particle size on the observed rate, and with limestone decomposition experiments carried out in a lab -scale downer reactor. It was revealed that particles larger than 100 μm exhibit internal mass transport resistances, due to CO2 accumulation within the particle, whereas heat transport limitations are not expected in the operating conditions of interest. A reference scenario demonstrated 92 % limestone conversion at realistic operating conditions, feasible in concentrated solar power plants. The solar flux density on the reactor wall influences the efficiency of the system critically since heat loss to the environment leads to greater solar input. To tackle the low efficiency, a partially insulated, indirectly irradiated reactor was investigated: the efficiency increased from 8 % to 26 %, while integration in a Calcium-Looping system can further boost the efficiency to 34 %. This approach constitutes a basis for future scale-up considerations.

Decomposition mechanism of lumpy dolomite particles

Cylindrical cm-sized dolomite particles were decomposed using the two steps decomposition scheme. Several studies on dolomite decomposition have been done using µm- to mm-sized samples over the years. However, these sizes are too small for industrial kiln application and ignore the influence of important parameters, e.g. thermal conductivity, on the decomposition process. In this work, the decomposition behavior of lumpy dolomite particles in each step was investigated. Experimentally measured sample temperature and conversion profiles in steps 1 and 2 are respectively similar to those obtained for the decomposition of pure magnesite and limestone. To measure the core temperature and conversion is to essentially analyze the decomposition behavior. The thermophysical material properties of the decomposition product in each step as a function of temperature was estimated using the shrinking core model. Finite difference method was employed in solving the 1D heat equation describing the process. The reaction rate coefficient in step 1 is shown to have a weak temperature dependence, the thermal conductivity of the product, MgO∙CaCO3, slightly increases with temperature but the permeability is not dependent. In step 2, the reaction coefficient and MgO∙CaO thermal conductivity and pore diffusivity do not show a clear temperature dependence. Finally, the sensitivity of the material and transport properties on the decomposition process was studied under shaft kiln condition. Thermal conductivity is observed to have the highest influence on decomposition with a value of up to 60 % at 1400 °C and for 120 mm particles.

The Co-Processing Combustion Characteristics of Municipal Sludge within an Industrial Cement Decomposition Furnace via Computational Fluid Dynamics

Dealing with municipal sludge in an effective way is crucial for urban development and environmental protection. Co-processing the sludge by burning it in a decomposition furnace in the cement production line has been found to be a viable solution. This work aims to analyze the effects of the co-disposal of municipal sludge on the decomposition reactions and NOx emissions in the decomposing furnaces. Specifically, a practical 6000 t/d decomposition furnace was taken as the research object. To achieve this, ANSYS FLUENT with a UDF (user-defined function) was applied to establish a numerical model coupling the limestone decomposition reaction, fuel combustion, and NOx generation and reduction reactions. The flow, temperature, and component field distributions within the furnace with no sludge were firstly simulated with this model. Compared with site test results, the model was validated. Then, with sludge involved, the structure and operation parameters of the decomposition furnace for the co-disposal of municipal sludge were investigated by simulating the flow field, temperature field, and component field distributions. Parametric studies were carried out in three perspectives, i.e., sludge mixing ratio, preheating furnace arrangement height, and sludge particle size. The results show that all three aspects have great importance in the discomposing process. A set of preferable values, including a sludge mixing ratio of 10%, preheating furnace height of 21.5 m, and sludge particle diameter of 1.0 mm, was obtained, which resulted in a raw material decomposition rate of 89.9% and a NO volume fraction of 251 ppm at the furnace outlet.

Integrated carbon assessment for sludge-derived concrete: Modelling and a comparative study

Concrete, a cornerstone of modern construction, bears a significant responsibility for global carbon emissions due to its energy-intensive pyroprocessing processes and the direct carbon emissions associated with limestone decomposition. With increasing global of awareness environmental sustainability, the imperative to decarbonise concrete production is becoming evident. Recent research highlights the significance of producing eco-friendly "green" concrete by incorporating treated alum sludge, a by-product of drinking water treatment often discarded in landfills, within the framework of sustainable construction. This research endeavours to develop a comprehensive model for the integrated carbon assessment of sludge-derived concrete products. By conducting scenario and sensitivity analyses, the study explores the decarbonisation potentials and quantifies the impacts of diverse variables on carbon output across the entire lifecycle of concrete products. These variables encompass supply chain dynamics, cement replacement ratio, carbon intensity of local grid mix, and the utilization of alternative fuels. Findings reveal that in comparison to general purpose (GP) cement production, sludge treatment has the potential to achieve an impressive 83.48% reduction in carbon emissions. Moreover, a modest 10% substitution of cement with treated sludge would contribute to 9.07% overall carbon reduction. The transition to full renewable energy consumption holds the potential for a remarkable 41.97% carbon reduction, while the integration of photovoltaic (PV) electricity and biogas heating offers a substantial 30.57% carbon reduction in the manufacturing of sludge-derived concrete. Nonetheless, supply chain alterations demonstrate limited impacts, given the prevalence of locally sourced raw materials and the low embodied carbon contents of transportation-intensive ingredients such as sand and aggregate. Despite discernible progress achieved through cement substitution and renewable energy penetration, full carbon neutrality remains an elusive goal.

Reducing carbon emissions in cement production through solarization of the calcination process and thermochemical energy storage

The conceptual design of a novel cement production process has been developed during the SolCement research project. Fossil fuels used for limestone calcination are replaced by concentrated solar energy. Also, a Thermochemical energy Storage Reactor - TSR is used for transferring energy between daytime and nighttime operation. Additionally, the process enables energy recovery from waste gases and integration with carbon capture systems by isolating the rich carbon dioxide stream produced by the decomposition of limestone. A computational study simulates and compares a conventional with two different versions of the SolCement process (with and without the TSR). Simulations show that the use of a solar calciner operated at 1000 °C increases energy savings, while shifting the production capacity towards daytime improves the overall performance. The proposed scheme can lead to a 33 % reduction in fossil fuel consumption, but only a 9 % reduction in overall emissions, corresponding to 493 kg CO2/tonne clinker, since most of the carbon dioxide is produced due to limestone calcination. However, with storage and further utilization of the CO2 rich gaseous outlet stream, the predicted reduction of emissions may reach 82 %. The TSR provides 22 % of the energy required for preheating during the night operation, while simple Rankine cycles can recover from the otherwise rejected hot gas streams, 49 % and 40 % of the electrical energy required for compressing the produced carbon dioxide during daytime and nighttime operation, respectively. This results in 33 kg CO2-eq per tonne of clinker less, or an additional 0.6 % emissions reduction.

The Kinetic Mechanism of the Thermal Decomposition Reaction of Small Particles of Limestone at Steelmaking Temperatures

Converter blowing limestone powder making slag steelmaking process has the advantages of low carbon and high efficiency, and can realize the resource utilization of CO2 in the metallurgical process, which is in line with the development direction of green metallurgy. Based on a thermogravimetric-differential thermal analyzer, the kinetic mechanism of decomposition of small limestone at steelmaking temperatures was investigated by a modified double extrapolation method. The results showed that with a higher rate of heating, limestone decomposition lagged, and decomposition temperature increased. Furthermore, the smaller the limestone particle size, the lower the activation energy of decomposition. Compared with N2, air, and O2, small limestone powder used for converter blowing could complete more rapid decomposition, and the time required for decomposition shortened by about 1/3, although the decomposition temperature increased in the CO2. The limestone decomposition rate increased and then decreased at low to high CO2 partial pressures. With a limiting link, the inhibition was more significant under high CO2 partial pressure, but the reaction can be fully completed by 1000 °C. The decomposition type modeled was stochastic nucleation and subsequent growth. As the partial pressure of CO2 increased from 25% to 100%, the number of reaction stages, n, increased.

Limestone hydrogenation combined with reverse water–gas shift reaction under fluidized and iso-thermal conditions using MFB-TGA-MS

The integrated CO2 capture and utilization (ICCU) in conjunction with the reverse water–gas shift (RWGS) reaction has emerged as a promising approach to achieve carbon neutrality. However, the scalability of CaCO3 hydrogenation in the context of large volumes of industrial flue gas is impeded by the limited understanding of its performance under fluidized and iso-thermal conditions. This study utilized micro-fluidized bed thermogravimetric analysis coupled with mass spectrometry (MFB-TGA-MS) and in-situ measurements to investigate limestone decomposition under H2 and Ar atmospheres. Results showed that H2 atmosphere increased the limestone decomposition rate by 5-fold (79.1% CO2 conversion and ∼100% CO selectivity at 710 °C) compared to Ar, with RWGS as the dominant route and self-catalytic activity of calcined CaO. Morphology evolution revealed finer pores and textures under H2 conditions. Meanwhile, apparent kinetic models analyzed experimental data and showed a reduction in activation energy from 178.5 kJ/mol (Ar) to 161.3 kJ/mol (H2). These findings support the effectiveness of ICCU-RWGS approaches for further commercialization.

Study on Carbon Emission Characteristics and Emission Reduction Measures of Lime Production—A Case of Enterprise in the Yangtze River Basin

A scientific carbon accounting system can help enterprises reduce carbon emissions. This study took an enterprise in the Yangtze River basin as a case study. The accounting classification of carbon emissions in the life cycle of lime production was assessed, and the composition of the sources of carbon emission was analyzed, covering mining explosives, fuel (diesel, coal), electricity and high-temperature limestone decomposition. Using the IPCC emission factor method, a carbon life cycle emission accounting model for lime production was established. We determined that the carbon dioxide equivalent from producing one ton of quicklime ranged from 1096.68 kg CO2 equiv. to 1176.96 kg CO2 equiv. from 2019 to 2021 in the studied case. The decomposition of limestone at a high temperature was the largest carbon emission source, accounting for 64% of the total carbon emission. Coal combustion was the second major source of carbon emissions, accounting for 31% of total carbon emissions. Based upon the main sources of carbon emission for lime production, carbon emission reduction should focus on CO2 capture technology and fuel optimization. Based on the error transfer method, we calculated that the overall uncertainty of the life cycle carbon emissions of quicklime from 2019 to 2021 are 2.13%, 2.07% and 2.09%, respectively. Using our analysis of carbon emissions, the carbon emission factor of producing one unit of quicklime in the lime enterprise in the Yangtze River basin was determined. Furthermore, this research into carbon emission reduction for lime production can provide a point of reference for the promotion of carbon neutrality in the same industry.

DEM-CFD coupled simulation of limestone calcination and fuel combustion in beam type lime shaft kiln

This paper presents the development and simulation analysis of a coupled DEM-CFD model of the gas–solid heat and mass transfer process in an industrial-scale beam lime shaft kiln, which uses Computational Fluid Dynamics (CFD) to simulate the combustion of gaseous fuels and the three-dimensional transport of mass, momentum and energy in the gas, and the Discrete Element Method (DEM) to simulate the movement of limestone particles and calcination reactions in the kiln are simulated using the Discrete Element Method. A beam lime kiln uses five burner beams staggered up and down to provide heat for the decomposition of limestone particles in the kiln, and natural gas is injected as fuel from the burners on the burner beams into the limestone bed of the kiln for combustion, while cooling air enters the kiln from the bottom air cap to cool the calcined products and then enters the calcination zone as secondary air to participate in the combustion. In this paper, a 250 m3 beam lime shaft kiln in normal production is used as the research object to simulate and analyze the data of temperature, gas and solidity field and limestone decomposition rate in the kiln. The simulation results show that the overall limestone calcination temperature in the kiln is low and the temperature distribution is uneven, and the decomposition degree of limestone near the kiln wall is higher than that in the center of the kiln. It's caused by the wall effect, the particle porosity is larger near wall, and combustion gas penetration is therefore enhanced in the vicinity. Meanwhile, the simulation results are in good agreement with the actual measured data, which verifies the reasonableness of the model for application in industrial-grade lime kiln.

An investigation of the global uptake of CO2 by lime from 1930 to 2020

Abstract. A substantial amount of CO2 is released into the atmosphere from the process of the high-temperature decomposition of limestone to produce lime. However, during the lifecycle of lime production, the alkaline components of lime will continuously absorb CO2 from the atmosphere during use and waste disposal. Here, we adopt an analytical model describing the carbonation process to obtain regional and global estimates of carbon uptake from 1930 to 2020 using lime lifecycle use-based material data. The results reveal that the global uptake of CO2 by lime increased from 9.16 Mt C yr−1 (95 % confidence interval, CI: 1.84–18.76 Mt C) in 1930 to 34.84 Mt C yr−1 (95 % CI: 23.50–49.81 Mt C) in 2020. Cumulatively, approximately 1444.70 Mt C (95 % CI: 1016.24–1961.05 Mt C) was sequestered by lime produced between 1930 and 2020, corresponding to 38.83 % of the process emissions during the same period, mainly contributed from the utilization stage (76.21 % of the total uptake). We also fitted the missing lime output data of China from 1930 to 2001, thus compensating for the lack of China's lime production (cumulative 7023.30 Mt) and underestimation of its carbon uptake (467.85 Mt C) in the international data. Since 1930, lime-based materials in China have accounted for the largest proportion (about 63.95 %) of the global total. Our results provide data to support including lime carbon uptake into global carbon budgets and scientific proof for further research of the potential of lime-containing materials in carbon capture and storage. The data utilized in the present study can be accessed at https://doi.org/10.5281/zenodo.7896106 (Ma et al., 2023).

Role of self-disintegrating effect produced by decomposition of limestone core on accelerating dissolution of lime in CaO–SiO2–FeOx slag

ABSTRACT The dissolution behaviours of lime, limestone and lime sample with limestone core-lime shell structure in CaO–SiO2–FeOx slag were investigated. The results show that dissolution of lime slows down once 2CaO·SiO2 layer is formed at slag/lime interface. Self-disintegrating effect produced by decomposition of limestone core can accelerate dissolution, but dissolution rate firstly increases, and then decreases with the CaCO3 content of samples increasing. Limestone must decompose to form lime before dissolution, and too much CO2 generated by decomposition of limestone bearing 98.9 wt% CaCO3 blocks the contact between molten slag and lime layer. Thus, limestone hardly dissolves after 60s contacted with molten slag. For lime sample with core–shell structure, the surface of sample is lime layer that can be directly dissolved in molten slag. Meanwhile, self-disintegrating effect produced by decomposition of limestone core enhances slag penetration, and accelerate dissolution. The optimum CaCO3 content in lime sample is 22.7 wt%.

Electrochemical Cement Clinker Precursor Production at Low Voltages

Cement production is carbon intensive today because fossil fuels are used to heat high-temperature kilns, and because CO2 is released as a byproduct of limestone (CaCO3) decomposition. Electrochemical reactors can decarbonize cement production by using electricity instead of heat to convert CaCO3 into Ca(OH)2, a cement clinker precusor, while releasing the CO2 byproduct as a pure stream. Herein, we report a “cement electrolyzer” that electrolytically converts limestone into Ca(OH)2 at a cell voltage of 1.8 V at 100 mA cm–2. This new benchmark improves upon the previous record of 4.2 V by oxidizing the H2 byproduct from the cathode compartment into protons for CaCO3 decomposition. A techno-economic model shows that this use of H2 decreases the cost of cement production by $36/tcement compared to the use of H2 as a kiln fuel. This work describes an energy-efficient cement electrolyzer and advances the feasibility of electrochemical cement production.

Transient simulation of heat and mass transfer in a parallel flow regenerative lime kiln with pulverized coal injection

Quicklime, which is an essential raw material in various industries, is primarily produced by thermally calcinating limestone in kilns. Among the various kiln designs, parallel flow regenerative (PFR) kilns with pulverized coal combustion are the predominant technology. The performance of the PFR kilns is determined by the interactions between the gas, limestone, quicklime, and coal particles inside the chamber. Additionally, the two chambers in the PFR kiln alternate after a short period during the operation. Consequently, the transfer behaviors between the various phases inside the chamber are in a transient state. A three-dimensional transient multiphase model was created to investigate the transient multiphase behavior. The entire operation cycle, which consists of calcination and regeneration processes, was simulated using a coupling method. The predicted CO2 concentration in the exhaust gas was compared with the industrial measurement data, and good agreement was obtained, with an error of less than 6%. Furthermore, variations in the gas and limestone temperatures and limestone concentrations with residence time during each period were obtained. During the calcination period, the gas temperature field stabilized after 100 s. After stabilization, the zone where intensive limestone decomposition occurred was located in the range 0–5 m from the lance tip. The maximum gas temperature in the calcination process was 1845 K, which was approximately 700 K higher than that of a PFR kiln fueled with natural gas. CO2 gradually accumulated in the middle part of the chamber; the average concentration of CO2 in the off-gas was 27.7%. In the regeneration period, the transfer process stabilization required 400 s. Furthermore, the maximum gas temperature was higher than that of a PFR kiln fueled with natural gas, with a difference of approximately 90 K. Contrary to the calcination period, CO2 accumulated in the peripheral region at the end of regeneration. The total CO2 emission is 1.2024 t CO2/t product for the investigated coal-fueled PFR kiln. These transient transfer characteristics, during the PFR operation, could aid the optimization of coal utilization and control of CO2 emissions in the future.

Research Progress of Low-Carbon Cementitious Materials Based on Synergistic Industrial Wastes

Cementitious material based on synergistic industrial wastes can be used as a new product for low-carbon transformation. It can aid in resource recycling and suitable consumption and utilisation of various industrial wastes. The proposed material can reduce a large amount of CO2 emitted during calcination in cement production and the decomposition of raw limestone. In addition, the material exhibits high durability and high resistance to corrosion in the marine environment that can further reduce CO2 emissions over the lifecycle of the carbon footprint of the building. Currently, many similar chemical kinetic processes and mineralogical reaction processes of particle migration and rebinding exist in the hydration and hardening reactions, service processes and durability evolution of different industrial waste cementitious systems for low-carbon production. The theoretical basis of preparing various low-carbon cementitious materials (LCCMs) with industrial waste systems is discussed herein, including the two theories of ‘complex salt effect’ and ‘isomorphic effect from tetrahedral coordination of silicon-oxygen’. Further research on LCCM is based on the theoretical foundation of ‘passive hydration kinetics’. Furthermore, this study presents the CO2 reduction potential of LCCM prepared using industrial wastes and provides future research directions in this regard.

Thermal and mass spectrometer analysis (TG - DTG - MS) of different oAPI gravity crude oils from new oil fields in Turkey

In this research, thermal analysis and kinetics of four different crude oil samples (oAPI range of 21.1–34.1) from different new oil fields of Turkey were studied using thermogravimetry (TG-DTG) coupled with a quadruple mass spectrometer (MS). Mixtures of crude oils and limestone matrix are prepared to give a composition of 15 % wt. crude oil in the matrix and the ramped temperature experiments are performed at different heating rates (10, 20 and 30 °C/min) under air atmosphere. In TG-DTG analysis three different reaction regions were observed, known as low temperature oxidation (LTO), fuel deposition (FD), high temperature oxidation (HTO) and finally limestone decomposition, respectively. In MS analysis, combustion products of different crude oils on the basis of both relative intensities and relevancy was monitored simultaneously. Finally, two different model free kinetic methods known as Ozawa-Flynn-Wall (OFW) and Kissinger-Akahira-Sunose (KAS) were used to determine the activation energy of the crude oil samples. It was observed that the activation energy values are varied between 189.47 and 290.41 kJ/mol (OFW method) and 181.75–288.37 kJ/mol (KAS method) in HTO region, respectively.

A novel gas removal method for the removal of C2H2 in calcium carbide slag slurry by fine bubbles combined with air purging: performance, mechanism, and in situ bubble imaging analysis

About 60% of carbon emissions in the cement industry come from the decomposition of limestone. As a key low-carbon technology of raw material substitution, calcium carbide slag (CCS, low-carbon calcareous material) can replace limestone to produce cement, desulfurizer, and other products, which can achieve carbon emission reduction and the upcycling of CCS. However, the release of residual C2H2 in CCS brings safety and environmental risks, which seriously restricts the upcycling of CCS. In this study, a novel gas removal method of fine bubbles (FBs) degassing was proposed for the removal of C2H2 in solid CCS particles, and an advanced in situ bubble imaging technology was used to investigate the performance and mechanism of C2H2 removal. The results indicated that approximately 70% of C2H2 (encapsulated C2H2) in CCS was difficult to remove by drying or slurrying. Under the optimal condition, the C2H2 removal efficiency was approximately 61.0%, and the amount of C2H2 released from the CCS slurry decreased by 92.9%. In the process of FBs degassing, large CCS particles in the CCS slurry were broken up into fine particles via the erosion mechanism, thus promoting the reaction of the encapsulated calcium carbide with water to produce C2H2. The generated C2H2 was dissolved in the slurry and could be quickly removed by FBs (<500 μm) with a fast mass transfer rate under the slight negative pressure. This work provides a novel gas removal method for effectively removing C2H2 in CCS and avoiding security and environmental risks, provides technical support for the upcycling of CCS, and provides a reference for the separation of other similar multiphase systems (e.g., gas–liquid/gas–liquid–solid, oil-liquid/oil-liquid–solid).

Analysis of the use of magnesium-containing additives in the charge of iron flux in order to reduce CO2 emissions

The growing requirements for the quality of finished steel products oblige to obtain steel with a low content of harmful impurities, especially sulfur. The main charge for steel production in the conditions of JSC EVRAZ NTMK is vanadium iron, the external desulfurization of which leads to large losses of valuable vanadium. Therefore, the smelting of iron with a low sulfur content is an urgent task. The main way to reduce sulfur in iron is to increase the basicity of the slag (B2), but MgO is the best desulfurizer. The paper evaluates the effectiveness of the use of various magnesium-containing materials in the conditions of the blast-furnace stage of JSC EVRAZ NTMK, taking into account CO2 emissions. The possibility of replacing limestone in the iron flux charge with dolomite, as well as with steel converter slag, is considered. Both materials will increase the proportion of MgO in blast-furnace slag, however, the use of dolomite is accompanied by a two-fold increase in CO2 emissions compared to limestone. Converter steel slag (CSS) does not contain carbonates, thus eliminating the formation of CO2 during the limestone decomposition. An additional advantage of CSS is its high content of valuable vanadium and manganese. The effect of an increase in MgO in slag on its melting point is considered. It has been established that an increase in the proportion of MgO to 14% will not cause difficulties in the processing of blast-furnace smelting products and will reduce the sulfur content in iron and the formation of titanium carbides and carbonitrides.