Sinter Mix Research Articles

Completion of the sintering process

The process of sintering is completed only on sinter machines with a cooling zone. The degree of completion of the process, characterized by the relative height of the melt zone during unloading of the sinter from other types of machines, which make up the absolute majority, is at the level of 60%. In practice, the “completion of the sintering process” is taken to mean the exit of the fuel combustion zone from the sintering bed. The heat exchange in the sintering bed is considered complete during process, because the temperatures of the exhaust gases and the material at the exit from the bed are close, and at 60% of the bed length they are represented by the dew point temperature. Due to this, the supply of heat from the cooled agglomeration sinter with air and the oxidation reaction of FeO to the fuel combustion zone, the high bed of the mix, the increased basicity of the sinter and the introduction of lime into the mix, the consumption of solid fuel is 40–45 kg/t of sinter with the amount of melt at the level of 60%. The expert system “Sinter’s Advisor” is simple and effective for control the sintering process. The most efficient and reliable for the necessary adjustment of the mix moisture content and solid fuel consumption are the current “advice” from the process itself. The technologist receives the first of them from the suction trends in the first vacuum chambers and in the ignition hearth, the bed surface temperature. For him to make a decision, the primary trends must be confirmed by the locations of the start of the exhaust gas temperature rise, then the maximum temperature. Fuel consumption control is effectively carried out according to the return fines balance. The process of sintering independently compensates for up to 40% of the negative impact of factors on the sintering rate, “regulating” the suction in the gas exhaust tract of the sinter machine. The use of a discrete version of “extreme control” is effective for the “Sinter's Advisor” system, in which the operating parameters of the sinter machine are processed, adjusted and set again for periods equal to the duration of the movement of the fuel combustion zone along the bed height. Installation of a thermal imager at the end of the sinter machine allows for continuous visual monitoring of the thermal level of the process, its uniformity across the bed width and not sintering mix, and to solve the control problem as a whole

Analysis of the sintering process of the sintering charge in a high layer. Report 1. Fuel combustion and dissociation of limestone

Communication 1 provides a brief overview of theoretical works on the creation of mathematical models of the sintering process, ranging from simplified balance models to the three-dimensional dynamic model. A modern three-dimensional mathematical model is adapted from industrial data on the agglomeration of a sinter mix in a bed 700 mm high with a bed of sinter at the sinter plant No. 5 of PJSC “MMK”. Changes in the device circuit diagram of sinter plan, the actual temperature of the mix, segregation of fuel along the height of the bed, the mode of intensive ignition of the mix in the ignition hearth with diffusion burners, the unevenness of the sintering process across the width of the pallets, additional heating of the bed after the hearth with air from a linear cooler, the actual degree of throttling of the vacuum chambers of the sinter machine, heat exchange in pallets are taken into account. The process of a combustion zone of solid fuel formation under the ignition hearth has been analyzed, and an increase in its height during the sintering process in a high bed has been established, that due to the segregation of mix and fuel along the height of the bed and the consumption of oxygen for the oxidation of FeO above this zone. The processes of limestone dissociation and melting of the mix zones formation and their development during the sintering process are considered

Batch Sintering of FeO·OH and Fe2O3 Blends: Chemical and Metallurgical Characterization

A sample of goethite iron ore sinter feed (G_SF) was employed as a raw material in a sintering bed. This sample partially replaced hematite sinter feed (H_SF), which is currently used as raw material in a sintering plant in the state of Minas Gerais, Brazil. This substitution did not adversely affect the chemical and metallurgical proprieties of the sinter mix product, provided that the utilization of G_SF was kept below 30% in weight. Despite the higher proportion of fines in G_SF, the presence of argillaceous minerals in the sample led to an improvement in the granulation index (GI) of the sinter mix product. The GI value increased from 68.4 to 82.7% for the experiments conducted without the presence of goethite ore and with 40% of goethite ore in the sintering mix, respectively. Consequently, the qualities of both the process and the produced sinter product were not compromised. The raw materials and the various sinters produced were characterized through X-ray fluorescence (XRF) and X-ray diffraction (XRD), as well as thermal gravimetric analysis (TGA). The XRD results were used to perform a quantitative assessment of the mineral phase using the Rietveld method (RM). This technique allowed for the determination of goethite content in the studied sample, which was 35.5%. Finally, the incorporation of G_SF in the sintering bed led to a 20% reduction in the cost of raw materials.

Rheological Studies on Optimizing the Sinter Mix Granulation Mechanism to Sustain Productivity

Granulation of the sinter mix is an important step in the iron ore sintering process. This article presents the results of various studies conducted to understand the rheological aspects and methods implemented in industrial‐scale sinter plants to sustain productivity over the last decade. The intergranular bonding material in the mixing and nodulizing drum is characterized to understand its influence on the granulation. Calcined lime, when increased from 20 to 40 kg t−1 of sinter, increases the granulation index and helps in achieving higher productivity. Up to 20 kg t−1, calcined dolo increases productivity, beyond which a decline is noticed. Lignosulfonate and polymer binders in the range of 0.2%–0.7% in the sinter mix, respectively, increase the granulation of the microfines (0.25 and 0.5 mm size). When a magnetic field is applied to water, the granulation improves. Higher electrical conductivity and lower contact angle of the recycled water are found to improve the bonding of the particles. Zeta potentials of fly ash and bentonite solution in water are positive and negative in the cases of calcined lime and calcined dolo. It is suggested to use fly ash as a binder of microfines.

Improvement of technology and technique for the production of sinter at the SP EVRAZ KGOK. Report 1. Loading and ignition of the mix.

A brief literature review of theoretical and applied works on charging and ignition of sinter mix has been made. The review considers experimental data on the influence of the distribution of the particle size of the mix and the fuel content over the height and width of the bed, and its bulk density on the consumption of solid fuel, height and gas permeability, on the productivity of sinter machines and sinter strength. The problems of sinter mix ignition, the influ-ence of throttling of the first vacuum chambers of sinter machines on the quality of sinter and gas consumption for ignition are discussed. The results of industrial studies of mix loading and ignition modes on EVRAZ KGOK sinter ma-chines are presented, which provide an increase in the bed height, an increase in the cold strength of the sinter, and a decrease in natural gas consumption for mix ignition. As a result of increasing the rotational speed of the drum feeder, the discrete descent of the mix from the mix flow stabilizer was eliminated. It has been established that due to the ex-pansion of the sinter pallets and the negative slope of their sides, there is no need to form a mix bed profile variable in height and width. The operation of sinter machines with and without separation of the loading chute from the bed has been studied. The presence of critical fluctuations of the grain size composition of the mix and the content of fuel car-bon in it along the width and height of the bed for both options of operation, due to the mode of operation of the shuttle mix distributor and fluctuations the height of the bed in the intermediate hopper, has been established. The important role of the design and mass of the mix smoother has been experimentally confirmed. The design of the throttling device of the vacuum chambers legs with manual change of the free section only as it wears out has been developed and implemented. The rational free section of the legs of the vacuum chambers is determined, which provides a minimum suction (1–2 Pa) in the chamber of the ignition hearth, and equal to 10–12%. As a result of the introduction of new technical solutions, an increase in the cold strength of the sinter by 1.09%, a decrease in natural gas consumption by 29%, and an increase in the height of the sintered charge layer up to 30 mm were achieved without reducing the productivity of sinter machines

Co-firing of Green Pellets and Sinter Mix in Packed Bed

Co-firing of Green Pellets and Sinter Mix in Packed Bed

Study of the charge pelletizing process at MMK`s sinter plant No. 5

Theoretical and practical issues of the influence of the rotation speed, the angle of inclination, the diameter and length of the pelletizing drum of high productivity on the mode of movement of the sinter mix (waterfall or rolling), on the degree of its filling with the mix, its residence time and mass in the drum are considered. The influence of mix consumption and moisture on the quality of its pelletizing at the SP-5 sinter machine of MMK PJSC was studied. The influence of the drum rotation frequency on the parameters and performance of the sinter machine has been studied. To adapt the mathematical model of the movement of material in the drum pelletizer, the distribution of the mix along its length and along the chord was measured. The adapted model was used to analyze the operation parameters of the drum pelletizer (degree of filling, distribution along the length, residence time and mass of the mix in the drum) in the experimental and calculated modes. The reasons for the non-compliance of the design characteristics of the operation of the drum pelletizer with the requirements for the implementation of the "rolling mode" for pelletizing the mix are established. The angle of inclination and the rotational speed of the drum pelletizer were determined on a mathematical model to form this mode. Reducing the rotational speed of the drum to achieve the rolling mode to 4.4 min–1 will also provide an increase in the service life of its drive by 1.5–2.0 times. A rational place for installing a drum pelletizer in the scheme of the apparatus chain is substantiated, depending on the type of iron ore raw materials (ore or concentrate). It is shown that when the drum pelletizer is set at zero, it is not possible to heat the mix with steam to the required temperature, and the installation of a 60 m3 bunker instead of an small intermediate bunker leads to the destruction of the mix granules as a result of falling from a great height and makes it difficult to control the layer level in this bunker.

Effects of Recycling By-Products as Calcium Ferrites Added to the Sinter Mix on Sinter Quality and Emission of CO2, NO, and SO2

Effects of Recycling By-Products as Calcium Ferrites Added to the Sinter Mix on Sinter Quality and Emission of CO2, NO, and SO2

Technology and Equipment for Sintering of Iron-Ore Materials by Adding Brown Iron Ores as Pulp during Sinter Mix Pelletizing at Ural Steel, JSC

The article deals with issues of sintering process design and equipment selection for conditioning of pulp containing brown iron-ore additives and its further supplying to the pulp and supplying to the drum pelletizer shall include a ball mill; inclined close-type screw conveyor; vertical mixer; hydraulic tank; double-phase spray nozzles; controlling, guiding, instrumentation and auxiliary equipment of hydraulic systems.

Specifics of Spectroscopic Features of Yb3+‐Doped Lu2O3 Laser Transparent Ceramics

Some specifics of spectroscopic and laser properties of Yb3+ dopant are shown in Yb3+‐doped Lu2O3 cubic sesquioxide transparent ceramics, a very important laser material, fabricated by Akio Ikesue using the method based on solid‐state mixing of oxides and sintering by hot isostatic pressing (HIP) technique. For instance, despite the simplicity of Yb3+ electronic configuration, it is emphasized that a lot of precautions need to be considered during the evaluation and the assignment of Yb3+ experimental data in this sample and also in all Yb3+‐doped materials. First, we focus our discussion on the position of 2F7/2 (ground state) and 2F5/2 (excited state) Stark levels of the most populated C2 symmetry site, and on the presence of the magnetic dipole transitions from the C3i (S6) inversion symmetry site. Then, we point out the strong influence of the self‐trapping and the self‐quenching processes on the measurement of the 2F5/2(5) upper level decay time which needs the pin‐hole method. Finally, we comment on the spectrum of the tuneable laser emission behaviour near 1033 nm with respect to the losses of the laser cavity without the laser emission near 1080 nm, as observed in other laser materials.

Improving the sinter productivity with increased specular iron ore in sinter blend

Specular iron ores are medium grade iron ores suitable for the use in agglomeration process. However, due to their hard texture, undesirable particle size and shape, poor assimilation performance and low reactivity at high temperature, its uses in agglomeration is very limited and restricted to almost 3-10% at most of the plants. In the present study, the effect of specular iron ore on sintering performance and sinter qualities are examined. It was observed that an increased proportion of specular iron ore in sinter blend showed poor sintering performance in both laboratory scale studies and plant scale trials. In the present work, the effect of blending of specular iron ore with goethite iron ore in sinter mix on sintering performance was examined and an optimum iron ore blend ratio for sustainable performance and quality was proposed. To increase the specular iron ore usage in sintering, goethitic iron ore up to 30% was introduced in sinter blend to overcome the deteriorating nature of specular iron ore. The goethite iron ore contains chemically bonded water which gets removed at higher temperatures (300-500?C) during sintering. The evaporated water gets cooled at lower bed and condenses which retards the air flow during sintering process and thus the combustion zone stays for longer time allowing better melt assimilation and sinter qualities. The poor melt assimilation of specularite is thus countered in presence of goethite iron ore. Having better reactive and hydrophilic nature of goethite iron ore, nullifying or reducing the ill effect of poor reactive and hydrophobic characteristics of specular iron ore during granulation and sintering process. Therefore, the blended specular and goethite iron ore resulted in improved sintering rate and consequently improved sinter productivity. The present work proposed usage of up to 30% of specular iron ore when blended with goethite iron ore in sinter making.

Influence of particles size distribution on the carbon content throughout sinter bed height

By the previous studies it was established that the character of solid fuel distribution throughout the bed height considerably effects the sintering machines productivity and the sinter quality. The purpose of the study was assessment of solid fuel distribution in the agglomerated burden throughout the height of bed at sintering machine. Sinter mix samples were taken from three sections of the bed: 150 mm - top part, 150 mm - middle part and 170 mm - bottom part at the sintering machines of NLMK. After screening the samples, particle size distribution was determined, as well as carbon content throughout the bed height and in the particles of different sizes. It was found that all solid fuel, irrespective of the size, gets balled into sinter mix granules, fine fuel (fraction -0.63 mm) was almost evenly distributed over the granules of different sizes, while coarse fuel (+3 mm) is mainly picked up by large granules. Solid fuel of -3 mm +0.63 mm fraction is mostly balled into 3-5 mm granules. Such nature of solid fuel distribution in the granules of the pelletized mix results in suboptimal distribution of fuel throughout the bed height at sintering machines No. 1, 2, despite satisfactory size segregation of the mix: it changes from low content in the top part to a higher content at the bottom of the bed. At sintering machines No. 3, 4 where there was no size segregation of the mix, fuel distribution throughout the bed height changes from optimal to non-optimal (low content in the top part). To optimize solid fuel distribution throughout the bed height with both good and poor segregation of the mix, it is necessary to reduce the content of 0-0.5 mm particles fraction in coke breeze.

Influence of coke rate on thermal treatment of waste selective catalytic reduction (SCR) catalyst during iron ore sintering

Waste selective catalytic reduction (SCR) catalyst as a hazardous waste has a significant impact on the environment and human health. In present study, a novel technology for thermal treatment of waste SCR catalyst was proposed by adding it to sinter mix for iron ore sintering. The influences of coke rate on the flame front propagation, sinter microstructure, and sinter quality during sintering co-processing the waste SCR catalyst process were studied. In situ tests results indicated the maximum sintering bed temperature increased at higher coke rate, indicating more liquid phase generated and higher airflow resistance. The sintering time was longer and the calculated flame front speed dropped at higher coke rate. Sinter microstructure results found the coalescence and reshaping of bubbles were more fully with increasing coke rate. The porosity dropped from 35.28% to 25.66%, the pore average diameter of large pores decreased from 383.76 μm to 311.43 μm. With increasing coke rate, the sinter indexes of tumbler index, productivity, and yield, increased from 33.2%, 9.2 t·m−2·d−1, 28.9% to 58.0%, 36.0 t·m−2·d−1, 68.9%, respectively. Finally, a comprehensive index was introduced to systematically assess the influence of coke rate on sinter quality, which rose from 100 to 200 when coke rate was increased from 3.5% (mass) to 5.5% (mass).

Modified coke breeze distribution in iron ore sintering - a novel technique of reducing energy consumption and improving quality

In normal sintering of iron ore, there is a wide difference in temperature of the sinter bed between top and bottom; i.e. the flame front temperature of the sinter bed gradually increases towards the bottom because the lower part gets longer time for drying and preheating by exit gas. Therefore, the top part may have insufficient fusion and the bottom is excessively fused. Thus, sinter quality may become inhomogeneous and the coke breeze requirement becomes higher than the actual thermal requirement. If it is charged in multiple layers; e.g. higher amount of coke at the top and a lower amount of coke at the bottom, heat will be homogeneously distributed and the actual coke requirement would be lower than the existing. However, no study has been done so far on this. Therefore, the current study explores the possibility of reducing energy consumption in iron ore sintering by reducing the coke ratio from top to bottom without deteriorating the sinter property. 12% reduction in coke breeze rate has been found and the sinter quality has been improved by the use of a triple layer of sinter mix with a lower coke rate towards the bottom. Further, when 5-vol% of oxygen has been enriched in suction gas along with using a triple layer of sinter mix, up to an 18-wt% reduction in coke breeze has been found.

A sustainable reduction roasting technology to upgrade the ferruginous manganese ores

Reduction roasting of manganese ores is a known process; however, it is not yet commercialized mainly due to various techno-economic issues. The current research work presents results of a large-scale plant trial performed at a commercial Direct Reduced Iron making plant to upgrade low-grade ferruginous manganese ores (Mn: 25–32%, Mn/Fe: ∼1). Trials were carried out using a lot of 2000 of tons low grades ferruginous manganese ores of three different types. Experiments were designed to test 3 levels of two different variables for each type of ore. Raw material feed rate (3, 4.5, and 6tph) and feed coal proportion (25, 29,33% of ore) were the prime process variables. Process settings were identified and fixed to limit the occurrence of undesired chemical reactions to restrict the formation of complex MnxFe3-xO4 phases and dilution of reducing atmosphere. Ores were crushed into 0–15 mm size, reduce-roasted at 950 °C in a rotary kiln, crushed into <3 mm size, and passed through a magnetic separator. The technology can enhance the Mn content of the ores by > 15 units (Mn: 30%→46%) and can bring down the Fe content by > 15 units (Fe: 27%→12%) in the produced ore concentrate. The developed process could achieve product yield ∼50% and Mn Recovery>70%. The Mn-rich concentrate was successfully converted into extrusion briquettes and consumed in a submerged arc furnace for ferroalloy making. The iron-rich by-product was successfully used as a sinter mix for steelmaking process. Techno-economic evaluation and sensitivity analysis have also been carried out. Studies indicated that roasting of ferruginous manganese ores at a commercial Direct Reduced Iron plant is an adaptable and sustainable solution to upgrade the low-grade Mn resources in the dynamic global Mn ore market.

Modification of Wet Granulation Process During Iron Ore Sintering

Sintering is the most extensively used and economic agglomeration process to prepare iron ore fines for blast furnace use. Granulation is the most critical factor controlling iron ore sintering process, as it improves sinter mix permeability. Currently, sinter plants are receiving significant proportion (up to 40%) of − 150 μm micro-fines in iron ore fines, which makes sintering difficult. The presence of moisture increases the specific volume of air required for sintering and it benefits the heat transfer during sintering. The present study was done in laboratory to understand the effect of water addition in two stages during granulation on sintering process. Pot sintering experiments were carried out to study the variation in process parameters for split water addition and normal method. For all experimental data, statistical analysis was done. There is no difference in value of process parameters with respect to normal method and split water method except in peak exhaust gas temperature; it was found more in case of split water addition which means a condition conducive for increased speed of sinter machine. Sinter produced with higher micro-fines by split water method is more homogenous as compared to normal method.

Cold Briquetting of DRI Fines for Use in Steel Making Process

DRI fines, generated during its manufacture and handling, generate high content of fines in the size fraction less than 2 mm. It has iron content above 80%. It is difficult to directly use such iron-rich material in the primary steel making process, without agglomeration. At JSW Steel Vijayanagar, around 50 to 70 tons per day of DRI fines with < 2 mm size fraction get generated. The fines are used in base sinter mix or it may be agglomerated suitably to use it as a coolant in the primary steel making process. Since the fines are extremely reactive, they are susceptible to oxidation if it is not agglomerated as soon as it is generated. The present study brings out the development of an agglomeration process for the DRI fines to a dense metallized briquette, for use as a coolant in basic oxygen furnace. Initially, the conditions for briquetting such as use of binder, hardener, lime, dust, moisture, briquetting and curing conditions were established in a 10 kg batch size. This was followed by industrial-scale processing, at 500 kg batch size. The physical and chemical characteristics of the fines and briquettes were assessed at different stages. The cold compressive strength of the cured briquette was found to be a function of moisture content. The handling parameters in the production condition, for long-term pile-up of briquettes against oxidation, were brought out. The successful use of the briquettes in basic oxygen process was demonstrated.

Flame front progress in gas assisted iron ore sintering

The present paper is focused on the control of heat release and on the propagation of the flame front in an iron ore sinter bed. Small scale sinter experiments are performed in cylindrical packings of the sinter mix which are ignited at the bed surface and vertically passed by the suction gas. The heat front propagation is found to be closely linked to the consumption of the fuel mix in the sinter bed. Based on this findings, a dual fuel approach is explored whereas front propagation of the solid fuel combustion (coke breeze) is supported by pulsed injection of a secondary gaseous fuel. A non-stationary, one dimensional model is established to analyse the heat wave travelling in the sinter bed. The model setup describes a local thermal non-equilibrium between the sinter bed being defined as porous medium and the permeating gas. The model is based on the balance equations for the mass and heat transports caused by the solid and gaseous fuel combustion. Model calculations support the experimental findings and demonstrate that satisfying sinter peak temperature levels and locally focused energy release are ensured by combined solid fuel burnout and high temperature gas combustion. During some lab-scale sintering tests, coke breeze content was reduced in the sinter feed mixture, and secondary fuel gas was supplied in pulsed mode to compensate the missing energy demand. The flame front speed as well as properties related to the sinter quality such as the tumble and shatter strength were determined, with the later index showing more sensitive results. The investigations demonstrate that pulsed methane injection can increase the flame front speed compared to the pure coke case with 5.1 wt% coke. , the pulsed gaseous fuel combustion can nearly compensate the strength loss for a moderately coke reduced rawmix with a coke content of 3.5 wt%.

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.

Improvement of Agglomeration Technology by a Sinter Mix Preheating

A series of industrial experiments was carried out on the sinter machine No. 1 of the sinter department of JSC "Ural Steel". The dynamics of the sinter mix temperature during the technological stages of its preparation from pelleting to loading on pallets was studied, depending on a water temperature change during pelletizing. It was defined that for the winter working of the sinter department of JSC "Ural Steel" the water temperature increases, which supplied the pelletizer to moistening, for every 10 ° C, facilitates an increase in the temperature of the sinter mix on the pallets by 1.5-2.0 °C. Therefore, for stable sinter mix production with a temperature of more than 55 ° C, it is necessary to use water supplied to the pelletizer for moistening, with a temperature of at least 85°C. To implement the proposed technology, it is necessary to equip the sinter machines with water-heating recuperative heater, installed above the sintering machine behind the ignition hood and using heat, radiated from the surface of the sinter.