Sinter Basicity Research Articles

Influence of Vanadium–Titanium Sinter Basicity on Cohesive Dripping Properties of Blast Furnace Comprehensive Burden

Vanadium–titanium ore possesses significant mining and utilization value. The basicity of vanadium–titanium sinter has a direct impact on the formation, location, thickness, permeability, and heat exchange of the cohesive zone in the blast furnace. This paper investigated the influence of increasing the basicity of the sinter on the comprehensive burden’s cohesive dripping properties in the blast furnace, while keeping the final slag basicity constant. This study was conducted through cohesive dripping property experiments. The findings indicated that as the sinter basicity in the comprehensive burden structure increased and the corresponding increase in the proportion of pellets occurred, the softening performance of the comprehensive burden improved, the cohesive zone became thinner, the lower edge of the cohesive zone shifted upward, and the softening melting properties became better in general. With an increase in the sinter basicity, the dripping difference pressure of the comprehensive burden decreased, and the dripping rate firstly increased and then decreased. An increase in the sinter basicity of the comprehensive burden structure promoted V reduction, and the V element yield and Cr element yield of the sinter were both increased; the optimal sinter basicity was 2.5, and the corresponding pellet proportion was 42%.

ОСОБЕННОСТИ РАБОТЫ ДОМЕННОЙ ПЕЧИ НА АГЛОМЕРАТЕ РАЗНОЙ ОСНОВНОСТИ

The paper shows the peculiarities of blast furnace performance when different types of iron ore material are used. It is noted that the main types of iron ore raw materials are sinter and pellets, their advantages and disadvantages are given. The influence of increased pellet consumption on blast furnace smelting is indicated. The influence of sinter basicity on its strength and recoverability is noted. The results of calculating the indicators and the operation mode of the blast furnace at increased sinter basicity and an increased ratio between its consumption and pellets are presented.

A Study of the Structure and Physicochemical Properties of the Mixed Basicity Iron Ore Sinter

To study the influence of sinter basicity on the microstructure, phase composition, and physicochemical and metallurgical properties, samples of agglomerates with different basicities were sintered and investigated. A comprehensive study of the structure, composition, chemical, and metallurgical properties of the sinter was conducted, and the optimum values for these properties were determined. The results of the mineralogical transformations that occurred during the sintering process are also presented. The magnetite contained in the concentrate partially dissolves in the silicate component and flux during agglomeration, forming a complex silicate SFCA with the general formula M14O20 (M–Ca, Si, Al, and Mg), which is the binder of the ore phases of the agglomerate. The proportion of ferrosilicates of calcium and aluminum in the sinter depends on the basicity of the sinter charge, and the morphology of the SFCA phase depends on the cooling rate of the sinter. The more CaO in the sinter charge, the more SFCA phase is formed in the sinter, and slow cooling results in the growth of large lamellar and dendritic SFCA phases.

Research on the Quality Improvement and Consumption Reduction of Iron Ore Agglomeration Based on Optimization

In order to increase agglomeration production and improve its quality while reducing energy consumption, a new intelligent blending method has been established at Ansteel to optimize its sinter blends. The statistical model of the ore blending results shows that (1) a blending ratio of 47.2% Ore A and 52.8% Ore C corresponded to the best sinter yield of 72.44%. (2) From the viewpoint of sinter reducibility, sinter basicity should not be less than 1.98 when the proportion of Ore A in the blend is more than 35%. Due to the low mixing efficiency of disc pelletizers, Ansteel has therefore gone through a massive technical transformation at Sinter Plant 3 to replace its 16 existing disc pelletizers with one drum granulator. Since the installation of the drum granulator, the standard deviation has decreased from 1.517 to 0.7332 for total Fe (T.Fe) and from 0.146 to 0.0956 for basicity. In the case of the drum granulator, the standard deviation for sinter T.Fe and basicity were 0.6926 and 0.05449, respectively, as compared to 0.8902 and 0.2033 for the disc pelletizers. In addition, a single lattice method is proposed to optimize the particle-size distribution of the coke breeze to further improve sinter quality and reduce fuel consumption. The lattice method indicated that the optimum coke breeze to achieve maximum sinter tumble strength should consist of approximately 57.20%: −1 mm, 25.63%: 1–3 mm, 11.17%: 3–5 mm, and 6.00%: >5 mm particles. Given the international trend of increasing bed depth, Ansteel has successfully achieved a bed height of 1050 mm or more under its blend conditions, which typically contain 75% concentrates. Finally, some new iron ore agglomerations research is discussed.

Variation in Iron Ore Sinter Mineralogy with Changes in Basicity

The target basicity of iron ore sinter is set by blast furnace slag composition requirements, and therefore varies with the proportion of acid burden such as lump iron ore and pellets. Increasing the lump proportion of the burden will increase the target sinter basicity. The mineralogy of sinter produced with a range of basicity between 1.0 and 3.0 was analysed using optical point counting under reflected light microscopy. Sinter from BlueScope Steel’s industrial sinter strand was analysed over a 30-year period, during which time a wide range of iron ore fines blends were utilised and several significant process modifications made. These data were compared with the mineralogy of sinters produced in a pilot-scale sinter pot, a laboratory-scale milli-pot, and small-scale sinter analogues. The mineralogy of the sinters from all scales followed a predictable trend with basicity, generally following the diagram proposed by Bagnall. At a basicity of 1.0, high temperatures were required to produce sinter with adequate strength, resulting in bonding phases dominated by magnetite and glass. Increasing basicity to 2.0 decreased the required sintering temperature and changed the mineralogy to a majority of hematite and SFCA. Further increases in basicity to 3.0 further decreased the required sintering temperature and increased the SFCA and dicalcium silicate content.

TO THE QUESTION OF SINTER BINDER FORMATION AND IMPROVEMENT OF THE SINTER STRENGTH

The higher share of unfluxed pellets in blast furnace burden determines the increase of sinter basicity (CaO/SiO2) up to 1.7‒2.2 units. Study of the microstructure formation peculiarities of such sinters is an urgent challenge. Recently, the mining enterprises have been increasing the iron content in the concentrate and use concentrate grades with iron content of 68‒70% in sintering. In this regard, it is interesting to study the microstructure of sinters with high iron content and the influence of mineral composition of the binder on the sinter strength. The schemes of formation of mineral composition of sinter with low basicity and high SiO2 content and with high basicity and low SiO2 content are given. The role of hedenbergite, ferrites and alumoferrites in the formation of the melt and the formation of the sinter structure is shown. It has been established that the structure of sinter with a basicity of 1.8 units and iron content of 57.1% consists of phases of partially oxidized magnetite, calcium monosilicate and glass of variable composition. In 1.8 basicity sinter with iron content of 59.4% the structure consists of phases of magnetite, calcium ferrite and glass of variable composition. The large amount of glass and pores in the binder does not allow the sinter hardening to be fully realized. The increase in strength is achieved by increasing the basicity of the sinter up to 2.1 units. The crystal structure of ferritic binder is needleshaped, which provides high strength of sinter. The amount of glass is reduced and it fills the gaps between the crystals of ferrite isolated from ore grains.

EFFECT OF BASICITY ON COMPLEX METALLURGICAL PROPERTIES OF SINTER

Metallurgical properties of sinter have a significant influence on its basicity. The dependence of cold and hot strength, softening point, reducibility and other physical and chemical properties of sinter on basicity was established by studies of many domestic and foreign scientists. However, taking into account essential increase of iron content in concentrate during decrease in silica content as a result of modernization of production in JSC Stoilensky GOK, the estimation of basicity influence on complex properties of sinter produced with the silica usage is actual. The results of laboratory research at Novolipetsk Iron and Steel Works with the purpose of study of sinter basicity influence on sintering process indexes, strength and high-temperature properties, including filterability of smelting products through the coke baffle are presented. The sinters of different basicity were produced in the laboratory conditions by sintering based on concentrate of Stoilensky GOK with iron content 68,0 %. The basicity of the charge CaO/SiO2 was varied in the range of 1.2‒2.0 units in steps of 0.2 units. In the process of research we selected the optimum rate of solid fuel for each charge from the condition of maximum vertical speed of sintering and sintering strength of sinter. It was found that increasing the basicity of sintering material leads to increasing cold and hot strength, narrowing interval of plastic-viscous state. The maximum vertical sintering rate and maximum specific capacity are reached at basicity 1.6. At basicity of 1.4 the minimum strength of sinter was obtained. It was established, that the sinter reducibility sharply increases at basicity of 1.6 units. With increase in basicity the temperature softening-melting interval (TSMI) of sinter decreases, which characterizes the cohesion zone. The widest TSMI is in sinter with basicity of 1.2, the narrowest – with basicity of 2.0. With increasing basicity of sinter the characteristics of the melt flow through the coke packing increases. The mixture of 55% of sinter with 2.0 basicity and 45% of unfluxed pellets from Stoilensky GOK had the best flow characteristics of the melt products and slag.

Study of iron content in iron ore concentrate increasing effect on sintering process indices and on metallurgical properties of sinter

Effectiveness of blast furnaces operation in many respects depends on metallurgical properties of agglomerate, in particular, iron content in the sinter and its basicity. At the same time, it is accepted that usage of iron ore concentrates with iron content more than 66–67% for sinter production results in decreasing of its strength. As a result of the planned modernization of the technological sections of the concentration plant JSC “Stoilensky GOK”, iron content in the concentrate will be increased to 68–70%. It makes it actual to accomplish comprehensive studies of metallurgical properties of the sinter while increasing iron content in the raw material. Results of the study of sinter properties presented, the sinter being obtained with utilization of iron concentrate with iron content 66.6 % (base), 68.0 and 69.2 % (exp. 1 and exp. 2 correspondently). The iron ore mixture for all the stages was the same and consisted of iron ore concentrate – 78.3%, sintering ore – 8.0%, lime – 5.5% and sintering additives (sludge, dust, scale) – 8.2%. The sintering mixtures composition for all the study stages differed only by fluxes and iron ore mixture consumption. 18 test sintering operations at three values of basicity 1.6, 1.8 and 2.0 units were accomplished. It was established that increase of iron content in the concentrate and basicity of the sinter results in improving of the sintering process indices, increase of the vertical sintering rate, sintering machines productivity, recovery and the sinter cold strength. Increase of the sinter basicity and its production with increased content of iron results in improving RDI indices at low temperature reducing. Results of the study of porosity indices and metallurgical properties of the sinter presented, in particular the collapsibility during reducing and temperature interval softening-melting presented. The advisability of concentrate with increased iron content utilization in the iron ore mixture shown.

Prediction and Optimization of Internal Return Fines Generation in Iron Ore Sintering Using Machine Learning

Prior to dispatch of sinter to the blast furnace for hot metal production, the sinter product from the sinter cooler is screened to remove smaller/finer particles. The undersize so generated is called internal return fines, which are generally recirculated into the sintering machine. A very high level of internal return fines generation limits the use of virgin ore for sintering which may hamper sinter productivity. Recently, the sinter plant at Tata Steel’s Kalinganagar works has faced issues of high internal return fines generation. As the sinter plant begins to increase its productivity levels, it becomes critical to control the generation of internal return fines to allow fresh material consumption. Limited literature is available on factors affecting the internal return fines generation in sinter plant. Given the current computational capabilities, a machine learning model was developed to ascertain the factors affecting the internal return fines generation. The development of the machine learning model and the optimization carried out based on model output is described in this work. The key parameters affecting the internal return fines generation were the sintering rate, sinter basicity, charge density and temperature in the ignition hood. In Kalinganagar, the increase in ignition hood temperature was limited by the furnace refractory condition. Further, the sinter basicity is determined by the percentage of sinter in blast furnace burden. Incorporating these constraints, the model was used to optimize the process parameters to generate the lowest possible return fines. The understanding generated from this machine learning framework has resulted in a reduction of 2-3% in internal return fines generation, which implied higher net sinter production.

Full-Scale Experimental Test Production of High-Basicity Sinter in the Enakievo Metallurgical Plant Sinter Shop

We describe the results for full-scale experimental test production of high-basicity sinter (basicity 2.0–5.0) at the Enakievo Metallurgical Plant Sinter Shop. As sinter basicity increased from 2.0 to 5.0, the iron content of the sinter decreased from 53.05% to 32.24%, and the ferrous oxide concentration decreased from 17.55% to 9.29%. However, the strength specifications of the sinter were improved: The concentration of 0–5-mm fines decreased from 19.32% to 15.89%, and the yield of +5 mm size class in a drum test increased from 65.9% to 72.3% through optimization of the sintering process parameters. The use of high basicity sinter in blast-furnace smelting reduced the specific consumption of lime in the blast-furnace charge from 233.9 kg/metric ton of cast iron (at sinter basicity 2.0) to 103.5 kg/metric ton (at basicity 4.5) and, correspondingly, the specific feed rate for coke during castiron production decreased from 538.1 kg/metric ton to 476.6 kg/metric ton.

Optimization of blast furnace charge by complex of metallurgical properties

To provide high indices of blast furnace process, it is necessary to meet hard requirements to metallurgical properties of iron ore raw materials and coke. Absence of equipment for their evaluation at steel-works stipulates the actuality of studies of dependence of lump raw materials metallurgical properties (meltability, hardness, reducibility) on chemical composition, optimal sinter basicity selection and relation sinter/pellets in BF charge. As a result of the studies optimal sinter basicity and relation between fluxed sinter and nonfluxed pellets in the BF charge having optimal complex of metallurgical properties, determined. Increase of the sinter basicity will result in improving cold and hot strength indices. The hot strength indices of nonfluxed pellets are higher comparing with those of sinter, but the wearability index is lower. Influence of BF charge composition on reducibility, temperature interval of softening-melting (TISM) studied. The nonfluxed pellets have a wide interval of softening-melting, and due to low temperature of softening can expand the TISM of the BF charge, which consists of sinter and pellets. The sinter having basicity 1.8 found to be optimal for BF heat due to complex of metallurgical properties. Increase of manganese and aluminum oxides content in the sinter with 1.8 basicity had a positive input in its viscoplastic properties. To improve the blast furnace operation the charge should be used, having 60% of sinter with basicity 1.8 and 40% of nonfluxed pellets of KMA ores.

Impact of Sinter Basicity and Alumina on Softening Melting Behavior in Blast Furnace

Softening–melting (SM) experiments have been carried out by using sinter basicity (CaO/SiO2) 1.74 to 2.09 and alumina content 2.90 to 3.39%. The objective of the work is to find the relation between sinter basicity and alumina on SM temperature range, so that we can improve the furnace performance. The increase in basicity of sinter from 1.74 to 2.09 at alumina 2.90 decreases softening start temperature and increases melting finish temperature. Thus, there is a rise in the SM temperature range from 192 to 245 degree Celsius (°C) which increases the gas flow resistance and reduces the permeability across the cohesive zone and deteriorating furnace performance, whereas on the other hand, with an increase in basicity from 1.74 to 2.09 at alumina 3.39, it decreases both softening start temperature and melting finish temperature. Thus, there is a decrease in the SM temperature range from 230 to 220 °C, which shows slight improvement in gas flow resistance.

Some basic properties of granules from ore blends consisting of ultrafine magnetite and hematite ores

Some basic properties of granules, including the granule size distribution, packed-bed permeability, and chemical composition of the adhering layer, were investigated in this study for four iron ore blends consisting of 5wt%, 25wt%, and 45wt% ultrafine magnetite and 25wt% ultrafine hematite concentrates. The effects of varying the sinter basicity (CaO/SiO2 mass ratio = 1.4 to 2.2) and adding ultrafine concentrates on the variation of the adhering-layer composition and granule microstructure were studied. Moreover, the effect of adhering-layer compositional changes on sintering reactions was discussed in combination with pot sintering results of ore blends. Increasing sinter basicity led to an increase in the basicities of both the adhering layer and the fine part of the sinter mix, which were higher than the overall sinter basicity. When the sinter chemistry was fixed and fine Si-bearing materials (e.g., quartz sand) were used, increasing the amount of ultrafine ores in the ore blends tended to reduce the adhering-layer basicity and increase the SiO2 content in both the adhering layer and the fine part of the sinter mix, which will induce the formation of low-strength bonding phases and the deterioration of sinter strength. The adhering-layer composition in granules can be estimated in advance from the compositions of the −1 mm fractions of the raw materials.

Study of blast furnace heat filterability through coke filling

Increase of gas permeability of burden materials column lower part is one of the way of blast furnace heat intensification. Filterability of intermediate slag through coke filling determines the gas permeability of the lower zone and the blast furnace heat running. To study the filterability a methodology was elaborated and implemented, which enabled to estimate reliably the iron ore raw materials behavior in the blast furnace at high temperatures. By laboratory studies influence on the filterability of BF slag melt was determined, when MgO, MnO and CaO adding to the burden, depending on the oxides mineralogical composition. The positive influence of magnesium oxide on the slag filterability has an extreme character, at that the sinter basicity has a considerable influence. The mineral form of magnesium-containing additives introduced into the burden substantially influenced the filterability on heat products in blast furnace. Replace ofsiderite and dolomite by other magnesium-containing materials facilitates to improving of slag filterability through coke filling. Additional input of manganese in the form of manganese limestone or manganese-containing ferritic-calcium flux is an effective mean to improve filterability of sinter smelting products through coke filling. Transfer to hot metal smelting from fluxed pellets and sinter will facilitate heat products filterabilityincrease thanks to close physical andchemical properties of BF burden components in respect of smelting and slag filtering through coke filling.

Study on the sintering melting characteristics of Meishan concentrate and its influencing factors

ABSTRACTThe melting characteristics of iron ore plays an important role in the process of sintering and mineralization. The softening and melting process of Meishan concentrate, the main mineral in the sintering of Meishan Iron and Steel Company, and four typical imported iron ores were observed through a visual micro-sintering test device. The results show that the Meishan concentrate has a relatively gentle liquid-phase velocity, good liquid-phase temperature control property, and relatively good safety. In addition, with the increase in alkalinity, its melting characteristics become worse. When combined with OA, its melting characteristics became worse, and with OD ore, its melting characteristics had improved in our study. Therefore, based on the principle of optimizing the complementary ore blending, in order to ensure the good temperature control and safety of the Meishan concentrate in the liquid phase of the sintering process, the appropriate sinter basicity and the appropriate type of iron ores should be selected.

Influence of basicity and temperature on bonding phase strength, microstructure, and mineralogy of high-chromium vanadium–titanium magnetite

To develop a smelting process for the comprehensive utilization of high-chromium vanadium−titanium magnetite (HCVTM), the micro-sinter test was applied to investigate the influence of basicity and temperature on the HCVTM sinters. The bonding phase strength (BS) was tested via an electronic universal testing machine. The phase transformations of the HCVTM sinters were detected via X-ray diffraction (XRD), whereas the structure and mineralogy of the HCVTM sinters under different temperatures and basicities were detected via scanning electron microscopy in combination with energy-dispersive spectroscopy (SEM–EDS). Our results demonstrate that the BS of the HCVTM sinters exhibits a slightly increasing tendency with an increase in temperature when the basicity is 2.4 and within the range of 2.8–4.0. Many cracks, small size crystals, and dependent phase structures are generated by increasing the sinter basicity. The BS is lower than 4000 N when the basicity is 2.2 and 2.8. When the temperature is in the range of 1280–1300°C, the BS exceeds 4000 N with the basicity of 2.0, 2.4, and 3.4–4.0. The pore size of the HCVTM sinters increases with the increase of the temperature. The perovskite decreases, whereas the silicate phase increases with basicity higher than 3.2. This study provides theoretical and technical foundations for the effective production of HCVTM sinters.

Exergy Analysis and Optimization of Sintering Process

Iron ore sintering is an important and large energy‐consumption segment in the iron and steel industry. It is thus essential to save energy in the sintering process considering both quality and quantity. This paper takes exergy loss minimization as an optimization objective, and a sintering optimization model is established based on material balance and exergy balance. Optimized results are obtained by solving constrained multidimensional nonlinear programming problems. Two types of sintering processes, in which solid fuels consist of coke and coke/coal powder, are calculated and analyzed. The effects of fuel ratio, fuel preheat temperature, and sinter basicity on exergy losses are also studied. The results show that the exergy losses obtained from optimizations for two types of solid fuels decrease by 5.0% and 8.1%, respectively. Exergy loss has a negative correlation with the coal ratio and fuel preheat temperature and a positive correlation with the coke ratio and sinter basicity. Exergy efficiencies increase from 29.7% to 35.0% and 35.5%, for each optimization. The research in this paper is highly significant to exploring of the sintering process, guiding steel production, and reducing energy consumption.

An integrated approach for production of stainless steel master alloy from a low grade chromite concentrate

As an alternative process, the production of stainless steel master alloys in blast furnace (BF) exhibits high economic efficiency and great potential to use low-grade chromite resources. To produce desirable sinter products required by the blast furnace smelting process, sintering tests of ore mixtures made from a low grade South African chromite concentrate (Cr2O3/FeO = 1.99) and Chinese magnetite concentrate were performed in a sinter pot in terms of various sintering parameters including coke dosage, mix moisture, sinter basicity and proportion of magnetite concentrate, etc. An integrated process comprising “high pressure grinding rollers (HPGR) pretreatment, pelletizing, coke coating, pre-drying and non-fluxed sintering” steps was proposed based on the pellet-sintering technique. The quality of Cr-bearing sinters was evaluated. The results show that high quality Cr-bearing sinters can be obtained through the proposed process. Addition of 40% or more magnetite concentrate in ore blends promises to yield desirable sinters of proper chemical composition and good metallurgical properties required by the blast furnace smelting process. The smelting performance of the Cr-bearing sinter made from the 40% chromite and 60% magnetite mixture was assessed under simulated blast furnace smelting conditions. It is feasible to use the Cr-bearing sinters in blast furnace for stainless steel master alloy production. A stainless steel master alloy containing 71.75% Fe, 19.52% Cr and 7.84% C with phosphorus and sulfur contents (<0.015%) is obtained at Fe and Cr recovery rates of 92.55% and 87.53%, respectively, when smelting at 1550 °C for 60 min with slag compositions (10% Al2O3, 10% MgO and R2 = 1.0). The bonding mechanism of Cr-bearing sinters and the formation mechanism of liquid phase were further revealed by X-ray diffraction analysis (XRD), scanning electron microscopy (SEM) and energy-dispersive spectrometer (EDS). Both slag bonding (10 to 20% silicate) and solid bonding (recrystallization of spinel phase) contribute to the consolidation of the Cr-bearing sinters. Increasing the basicity of sinter made from 100% chromite concentrate or addition of magnetite concentrate in the ore blend at natural basicity lead to the formation of low-strength slag bonds, which generally reduces the sinter strength.

Environmental and Technological Aspects of Converter Slag Utilization in Sintering and Blast-Furnace Production

The paper presents calculation results for predictive conditions of blast furnace operation with the use of converter slag in the iron ore portion of the blast furnace burden. It shows that addition of converter slag in the sinter and blast-furnace burden without correction of the operating conditions is not reasonable as it significantly worsens parameters of blast furnace operation. Long-term operation of blast furnaces with addition of converter slag in the burden will be accompanied by gradual accumulation of phosphorus in metal and will lead to increasing problems regarding phosphorus removal at the converter production stage. The use of converter slag makes it possible to increase the consumption of non-fluxed pellets without changing the sinter basicity and improve parameters of blast-furnace smelting. The problem of efficient and continuous use of converter slag in blast furnaces can be solved by the complex analysis of this problem: evaluation of economic feasibility of its use as a fluxing agent; feasibility study of this issue for the “blast-furnace production – converter production” complex; analysis of environmental problems during operation at the factory and in the region.

Effect of Converter Slag Consumption on Blast Furnace Operating Indices

Results are provided for calculation of the predicted blast furnace operating regime using converter slag in the iron-ore part of the charge without implementing additional measures with the aim of evaluating its effect on process indices. Introduction into a blast furnace charge of fractionated converter slag may be performed in order to increase slag magnesia content and to use it as a basic for flux for increasing the proportion of pellets in a charge of an individual furnace without changing the prescribed sinter basicity for the whole workshop. An increase is provided in gas permeability of the dry part of a charge for a furnace with a limited upper zone in the case of distortion of its profile. Charging converter slag into a blast furnace gives rise to an increase in iron phosphorus content. Prolonged use of converter slag in all blast furnaces gives rise to accumulation of phosphorus in metal, and consequently to resolution of the problem of removing phosphorous during converter treatment. The choice of the ratio of charge components may be made by maintaining the iron content in a fluxed charge at a level relating to specifications of the technology and the task of providing an economic furnace regime. Solution of the question of the expediency of using converter slag in blast furnaces is possible with comprehensive analysis of the problem: evaluation of the economic expediency of its use as a fluxing additive; economic development of this question for a blast furnace – converter production complex; choice of a furnace operating regime in accordance with its operating conditions; analysis of the ecological problems of the operation of an enterprise and a region.