Permeability Of Sinter Bed Research Articles

Vibration Sensor in Multiphase Flow Measurement

The solid waste generated in the steel industry are predominantly recycled via the agglomeration making route. In recent times, the amount of fines percentage has increased in sinter making, thereby affecting the bed permeability which eventually affects sinter quality. Hence, sinter bed permeability is to be monitored continuously. Currently the conventional infrared based velocity measurement is being used for this purpose. The permeability is being calculated based on the flow velocity of flue gases. The current paper is focused on the development of low cost novel vibration sensor for flow measurement to monitor permeability. The measurements are showing with good accuracy (96%) in comparison with the conventional technique. The design and development along with the results are discussed in detail in this paper.

Effect of Mixing Pre-heated Water on Granulation and Iron Ore Sinter Properties

Granulation of sinter feed mix is one of the most important factors in determining the permeability of sinter bed and sinter properties like sinter yield, tumbler index, etc. To improve the granulation of sinter feed mix, various technologies like two-stage granulation process, coating granulation process, wet vertical ball mill and use of magnetic water have been reported. In this paper, effect of pre-heated water (30, 60 and 90 °C) on granulation fitness of sinter feed mix was studied using a laboratory mixing drum. Sinter properties were investigated using pot sinter experiments. It was observed that with addition of pre-heated water, granulation fitness i.e., Balling index (BI) and Granulation index (GI) has increased, indicating that wetting of sinter feed mix has improved significantly. Treatment of sinter feed mix with pre-heated water reduces the surface tension of water and improves slaking of lime. This enables improved binding of the small size faction (− 0.25 mm), leading to stronger green ball which results in reduced fine generation during charging to the sinter bed. This further leads to the improvement in bed permeability and sinter properties. Enhanced hydration of lime and improved dispersion of water thus achieved have benefitted granulation fitness (GI increases by 5.3% and BI increases by 9.7%). Sinter yield increases by 2.1% and tumbler index by 1.6%. The results suggest that the proposed methodology is effective in improving the granulation fitness of sinter feed mix and sinter properties.

Quality and productivity enhancement of sintering process using correlation-based online permeability by infrared-based flow measurement technique

ABSTRACT Sinter is the most preferred metallic burden for modern-day blast furnaces. It is produced by agglomeration of iron ore fines in sinter machine. Sintering process depends on airflow through the sinter bed under high suction. The airflow through the sinter bed is measured by sinter bed permeability and has direct correlation with sinter productivity. Permeability can be determined by different ways. Among these methods, permeability detection by measuring the airflow through granular sinter bed by placing the instrument in the static wind box is very well known. But there is a challenge due to multiphase and turbulent conditions in the wind box.Infrared-based flow measurement technique has been used to measure flow. Therefore, this flow has been used to get permeability in the form of JPU (Japanese Permeability Unit). Productivity increases by 4% in spite of decrease in mean particle size of iron ore by 3.4% for a fixed time duration.

Study on the Manufacturing of Ultra-Fine Ore Briquettes for Charging in a Sintering Machine

In ironmaking, the optimal size of the iron ore charged into a blast furnace is generally 10-30 mm. Oversized ores, which have a smaller reaction surface area, are crushed, while undersized ores, which decrease permeability, undergo a sizing process before being charged into the blast furnace. Recently, however, iron ore has been micronized, and there is less high-quality iron ore. Also, in accordance with the Paris climate change accord, the Republic of Korea must reduce CO2 gas emissions by about 39% before 2030 to conserve the environment. In response, steelmakers have researched a sinter-briquette complex firing process which employs a method of charging where the raw materials are sintered together with briquettes made of ultra-fine ore. Extra heat is needed to sinter the briquettes. If the briquettes are broken during transporting and charging, the sinter bed permeability decreases, which decreases productivity. In this study, briquettes were made by changing manufacturing conditions such as moisture content, feeding speed, and size, and were simulated by changing the pocket depth in a numerical analysis. Consequently, it was determined that the compressive strength of the briquette was highest when moisture in the briquette was 6 wt%, in proportion to feeding speed and large particle size. Briquette density was in inverse proportion to pocket depth, and when the depth was over 15 mm, the briquette was broken in the pocket.

Strengthening granulation behavior of specularite concentrates based on matching of characteristics of iron ores in sintering process

Specularite concentrates have advantages of high ferrous grade, less harmful impurities and low price. However, the small size and poor granulation behavior of specularite concentrates consequently deteriorate the permeability of sinter bed and reduce the productivity of sinter, resulting in un-effective utilization in sintering process. The granulation experiments were carried out when specularite concentrates matched with five kinds of fine or coarse ores, and the effects of surface property and wettability of fine or coarse ores on granulation behavior of specularite concentrates were investigated. Then, the optimized ore blending recipes were proposed to strengthen the granulation behavior of specularite concentrates. The results indicated that the growth index increased with increasing the specific surface area of fine ores and had a positive linear correlation with the circularity degree of coarse ores, whereas negative correlations exist between the growth index and the contact angle of fine or coarse ores. Compared with the scheme of blended ores containing 15 mass% specularite concentrates, the growth index increased by approximately 22% in the case of using Ore-A and Ore-E with greater surface property and higher wettability to replace all of Ore-B and half of Ore-D, respectively. Furthermore, the vertical sintering speed and the productivity of sinter improved by approximately 23% and 20%, respectively.

Preparation of Iron Ore Micro-pellets and Their Effect on Sinter Bed Permeability

At present around 6–7% of iron ore slimes, out of total production, are being generated and accumulated at iron ore mine sites of National Mineral Development Corporation Limited, India. The accumulated slimes of finer size and relatively inferior grade should be utilized in an economical way for sustainable mining. These slimes can be agglomerated into micro-pellets for subsequent use in sinter making through hybrid pellet sintering method. However, the micro-pellets of sufficient size and strength are required for hybrid sinter making. The green properties of the micro-pellets depend upon various parameters such as surface area, moisture, binder, etc. In this study, iron ore slimes were beneficiated through gravity, and magnetic separation and concentrate of grade 65% Fe (Total) was obtained. Since the concentrate obtained had low surface area (700–900 cm2/grams) rendering it unsuitable for micro-pellet making, it was further subjected to grinding in a ball mill. The requirement of surface area for producing an optimum quality of green micro-pellets was established. The resultant micro-pellets were further used in studying sinter bed properties. The effect of moisture and size of micro-pellets on permeability of sinter bed were examined. The results confirmed that the addition of micro-pellets to the sinter mix improved the permeability of the sinter bed. The sinter bed with highest permeability of JPU 25.25 and void fraction of 36.27% was achieved with micro-pellets of size 3–6 mm at 7% moisture level. Mean granule size of sinter mix was also studied with respect to moisture content and size of the micro-pellets.

Effect of pre-briquetting on the granulation of sinter mixture containing high proportion of specularite concentrate

Specularite concentrate assays high iron grade and little impurities, but has been blended in sinter mixtures only with lower ratio because of its poor granulating performance. Nearly all of existing methods for improving granulation of sinter mixtures comprising specularite concentrate all need finely grinding of it, which means higher energy consumption and production cost. In this paper, granulating characteristics of specularite concentrate were investigated and the pre-briquetting process was employed to improve granulation of sintering mixture containing specularite concentrate. The experimental results show that granulating efficiency was debased obviously when the ratio of specularite fines in sinter blends exceeded 24%. Most specularite particles distributed in the fine granules of −1 mm and adversely affected the permeability of sinter bed. In granulation with specularite concentrate pre-briquetted, the average granule size and permeability of sinter bed increased by 11.17% and 12.69% respectively when the sinter blend contained 36% of specularite concentrate, compared with that in traditional granulation. The pre-briquetting process made the specularite concentrate into independent quasi particles preliminarily, thus changed granulation model and distribution of specularite particles in sinter bed and improved the granulation of sinter mixture containing high ratio of specularite concentrate.

The Relationship between Sinter Mix Composition and Flame Front Properties by a Novel Experimental Approach

ABSTRACTThis study explores a new technique for iron ore sintering to assess some flame front properties in a laboratory test, such as the flame front speed, combustion zone duration time, combustion zone thickness, combustion rate, and study the relationship between sinter mix composition and flame front properties. Results agree with those obtained by other researchers using embedded thermocouples and also predictions from a numerical sintering model well. When flame front moves forward, combustion zone duration time (DTCZ) and thickness increases. DTCZ increases from 1.65 min at the top interface to 1.80 min at the bottom interface. Combustion zone thickness is closely related with flame front speed. Melt in the iron ore sintering process has a large influence on flame front parameters, which affects oxygen diffusion on the coke surface, sinter bed permeability, and the heat transfer. Coke combustion rate is closely related with flame front speed and single coke particle burn-out time.

Effect of Ca-Fe oxides additives on NOx reduction in iron ore sintering

As the emission control regulations get stricter, the NOx reduction in the sintering process becomes an important environmental concern owing to its role in the formation of photochemical smog and acid rain. The NOx emissions from the sintering machine account for 48% of total amount from the iron and steel industry. Thus, it is essential to reduce NOx emissions from the sintering machine, for the achievement of clean production of sinter. Ca-Fe oxides, serving as the main binding phase in the sinter, are therefore used as additives into the sintering mixture to reduce NOx emissions. The results show that the NOx reduction ratio achieves 27.76% with 8% Ca-Fe oxides additives since the Ca-Fe oxides can advance the ignition and inhibit the nitrogen oxidation compared with the conventional condition. Meanwhile, the existence of Ca-Fe oxides was beneficial to the sinter quality since they were typical low melting point compounds. The optimal mass fraction of Ca-Fe oxides additives should be less than 8% since the permeability of sintering bed was significantly decreased with a further increase of the Ca-Fe oxides fines, inhibiting the mineralization reaction of sintering mixture. Additionally, the appropriate particle size can be obtained when mixing an equal amount of Ca-Fe oxides additives of −0. 5 mm and 0. 5−3. 0 mm in size.

Relationship Between Iron Ore Granulation Mechanisms, Granule Shapes, and Sinter Bed Permeability

ABSTRACTThe shape and size of granules are the basic factors that influence the packing structure and permeability of granular materials. This paper focuses on granulation mechanisms and the shapes (sphericities) of granules produced during the granulation of different feeds of iron ore for sinter production, using X-ray microtomography. Granule structures revealed that four mechanisms governed the formation of the granules namely autolayering, coalescence, adhesion of micropellets and two-stage layering. The addition of iron ore in the form of concentrate and micropellets to the sinter mixture enhances the mean sphericity of the granules while decreasing the sinter bed voidage and permeability.

Influence of beneficiated sinter grade iron ore fines size on sinter productivity and quality

The iron ore sinter structure and its physical and metallurgical properties mainly depend on the raw material chemistry, size, size distribution and sintering process parameters. Pot grate sintering studies have been carried out on iron ore fines of different sizes like –3 mm (mean size 1.46 mm), –6 mm (Mean size 1.95 mm), –8 mm (mean size 2.20 mm), and –10 mm (mean size 2.63 mm) to study the influence of iron ore fines feed size on granulation, sinter bed permeability, sinter mineralogy, sinter physical and metallurgical properties. The experimental iron ore fines consist of –150micron size 14.5 to 15.2% and coarser size was maintained from 10 to 3 mm size. The results showed that sinter with mean particle size 2.20 mm (–8 mm size) showed higher productivity due to better granulation and sinter bed permeability and good physical (strength) and metallurgical (RDI and reducibility) properties due to the formation of high strength acicular SFCA phase with fine porosity. The sinter with iron ore fines mean particle size 2.63 mm showed physical and metallurgical properties within the acceptable range, which is required for blast furnace operation. Sinter with mean particle size 1.49 and 1.95 showed poor sinter strength, RDI and productivity due to poor sinter granulation and sinter bed permeability. Iron ore fines size less than 6 mm and 3 mm was not suitable for sinter making to achieve better granulation and sinter properties.

Effect of concentrate and micropellet additions on iron ore sinter bed permeability

With the depletion of high-grade lump iron ore, concentrates have been identified as an alternative material for sinter making. In this study, the effect of concentrate and micropellet additions on the permeability of the sinter mixture was investigated. Permeability was measured on sinter mixtures containing 10–40% concentrate or micropellets at various moisture contents. The results confirmed that the addition of concentrates to the sinter mix decreases the maximum permeability of the sinter bed. Incorporation of micropellets into the sinter mix reduced the permeability less than concentrate addition. The maximum permeability of sinter mixes containing concentrate is reached at the same moisture content as the sinter mixture without concentrate addition. For sinter mixes containing micropellets, additional water must be added to obtain maximum permeability. Granule size, void fraction and angle of repose were also investigated to evaluate their effects on the permeability of the sinter bed.

Effect of H2O(g) Content in Circulating Flue Gas on Iron Ore Sintering with Flue Gas Recirculation

The influence of H2O(g) content in circulating flue gas on sintering was studied by simulating the flue gas circulating sintering. The results show that the burning speed of solid fuel and the heat transfer rate during sintering process are improved when the H2O (g) content increases from 0 to 6%, which accelerates the sintering speed. However, when the H2O (g) content exceeds 6%, the over-wet zone in sinter bed is thickened, which deteriorates the permeability of sintering bed. In addition, the magnetite content in sinter increases, while the acicular calcium ferrite content decreases. Accordingly, the sinter yield and tumble index decrease with excessive H2O (g) content. To guarantee the yield and quality of sinter, the favourable H2O (g) content in circulating flue gas should be controlled to be less than 6%.

A Novel Approach for Utilization of Ultra-Fines Iron Ore in Sintering Process

The current study presents a novel approach for the utilization of ultra-fines iron ore (−0.2 mm) in sintering process through its conversion into mini-pellets (4–9 mm). The mini-pellets were composed of ultra-fine iron ore and calcium hydrate while coke fines were used as a coating layer. One part of mini-pellets was cured with CO2 to improve the strength of green pellets while another part was kept uncured. The trails were carried out in sinter pot after adjusting the operating parameters. The utilization of 30% cured mini-pellets was accompanied by the constant highest temperature (≈1400 °C) in combustion zone. On the contrary, the sinter prepared using 30% uncured mini-pellets showed the highest temperature (≈1471 °C) at the beginning of sintering process followed by a gradual decreasing in the temperature. The permeability of sinter bed was improved by using cured mini-pellets in the sinter mixture. The sinter indices including the product yield, tumbler index and fuel consumption are measured. Reflected light microscopy, scanning electron microscopy, and X-ray diffraction analysis were used to characterize the microstructure and the developed phases.

An Innovative Magnetic Charging Chute to Improve Productivity of Sinter Machine at Rourkela Steel Plant

Sintering is a process in sinter machine for agglomeration of iron ore and other raw material fines into a compact porous mass, i.e., sinter, used in Blast Furnaces as an iron bearing input charge material for hot metal production. ‘Permeability’ of sinter-bed on sinter machine i.e., the porosity in sinter-bed of charged materials, facilitates atmospheric air passes from the top to bottom across the depth of sinter-bed, when suction created from the bottom of the bed, for efficient heat carry over from top to bottom of the bed for complete burning of charged materials for effective sintering process controls the productivity of the sinter machine. The level of ‘permeability’ in sinter-bed is depending upon the effectiveness of ‘charging chute’ in size-wise ‘segregation’ of charge materials across the depth in sinter-bed, achieved due to differences in the sliding velocities of particles during charging into the moving sinter-bed. The permeability achieved by the earlier conventional ‘charging chute’ was limited due to its design and positional constraints in sinter machine. Improving the productivity of sinter machine, through increased permeability of sinter bed is successfully achieved through implementation of an innovatively designed and developed, “Magnetic Charging Chute” at Sinter Plant no. 2 of Rourkela Steel Plant. The induced magnetic force on the charged materials while the charge materials dropping down through the charge chute has improved the permeability of sinter bed through an unique method of segregating the para-magnetic materials and the finer materials of the charge materials to top layer of sinter bed along with improved size-wise segregation of charge materials. This has increased the productivity of the sinter machine by 3% and also reduced the solid fuel consumption i.e., coke breeze in input charge materials by 1kg/t of sinter.

Improvement of Permeability of Sintering Bed by Adding Dry Particles to Granulated Raw Materials

In order to increase the permeability of the sintering bed for sinter ore productivity, RF-MEBIOS (Return Fine - Mosaic Embedding Iron Ore Sintering) process, in which return fine as dry particle is added to granulated raw materials and then they are charged into a sintering machine, is proposed.In this paper, the pot suction tests and the direct shear tests were carried out to confirm the reason of increasing permeability of the sintering bed by addition of dry particle. As a result, it is proven that the increasing of permeability is caused by two major phenomena. One is by increasing the pseudo-particle size at granulation and the other is by decreasing the bulk density of the sintering bed after charging. The former is achieved by higher moisture content in the raw materials at granulation. The latter is achieved by higher friction in the packed bed composed of dry and wet particle compounds. Therefore, the voids are easy to remain in the sintering bed when the materials are charged into the sinter machine. The influence of the dry particle brand on permeability is not so strong, but larger dry particles make the permeability higher. Also, when the wet particles are added after granulation, the permeability decreased at the same moisture content condition of the packed bed.

Effect of Utilization of Metallic Fe Particles as an Agglomeration Agent on the Permeability of Sintering Bed

Effect of Utilization of Metallic Fe Particles as an Agglomeration Agent on the Permeability of Sintering Bed

Recycling of steel plant mill scale via iron ore sintering plant

During the processing of steel in steel mills, iron oxides will form on the surface of the metal. These oxides, known as mill scale, occur during continuous casting, reheating and hot rolling operations. Mill scale is a valuable metallurgical raw material since it contains 65–70% iron. JSW Steel Ltd is a 7 Mtpa integrated steel plant and generates 270 t of mill scale per day. Most of the materials of steel plant wastes are recycled through sinter making in most of the countries. Because of its physical, chemical and mineralogical properties, it can be used as a raw material in a process like sintering. The mill scale contains high amounts of Fe and low amounts of silica and alumina. Thus, recycling it through the sintering process helps in the saving of raw materials like iron ore and limestone. This paper presents preliminary findings of a study that investigates the potential for recycling steel mill scale in the sintering process. Experiments were conducted using the mill scale in sinter making from 0 to 70 kg/t of sinter. The total Fe and FeO contents of the sinter increased with the increase in mill scale addition. The sinter productivity decreased with the increase in mill scale addition due to a decrease in sinter bed permeability. The sinter strength and sinter mean size initially increased and reaches a maximum at mill scale addition of 40–50 kg/t of sinter and afterwards declines with the increase in mill scale addition. Sinter reduction degradation index and reducibility decreased with the increase in mill scale addition due to the increase in FeO content. Except sinter productivity, other desired sinter properties can be obtained with the use of 40–50 kg mill scale per tonne of sinter.

Influence of Iron Ore Fines Feed Size on Microstructure, Productivity and Quality of Iron Ore Sinter

The sinter structure and its characteristics mainly depend on the raw material chemistry, size, size distribution and the sintering process parameters. In sintering process heat is supplied by coke breeze in the sinter mix to raise the bed temperature to achieve partial fusion and diffusion bonding. Airflow rate and flame front speed in sintering process has been found to guide the performance of the sinter plant and these parameters mainly depends on the sinter bed permeability. The flame front speed (bed permeability) has been considered as one of the important operating parameter and it depends on several factors; the feed size of the sinter being one of the most important parameter among them. Since iron ore proportion is at higher side in the sinter mix, its size fraction is very important. JSW Steel sinter plant receives iron ore fines of –10 mm size from Bellary – Hospet region which consist of 3 to 9% bigger than 10 mm and 30 to 35% smaller than 0.15 mm size fraction. It is well known that larger particles favour diffusion bonding and smaller particles favour slag bonding in sintering process. Accordingly, the study of the assimilation characteristics of different size range iron ore has an important role to control the reactions in the sinter bed and to obtain the target mineral structure. Too much variation in coarser and finer particle size range in sinter mix, the behavior of these +10 mm and –0.15 mm particles have been a subject of investigation and it is necessary to understand the role of iron ore particle size on sinter microstructure, sinter strength, sinter RDI, and productivity. In present work pot grate sintering experiments have been carried out in laboratory with different level iron ore size (mean particle size from 1.22 to 3.95 mm) to understand the influence of iron ore mean particle size on mineralogy, productivity, physical and metallurgical properties of the sinter. Sinter productivity increased with increase in iron ore mean particle size due to increased flame front speed (FFS) and improved bed permeability with lower sintering time. Sinter with iron ore mean particle size of 2.59 mm (Classifier fines) yielded better sinter strength with lower fines (–5 mm) and lower RDI. Higher sinter strength is due to effective distribution of acicular silico ferrites of calcium and alumina (SFCA) phases. The improvement in sinter RDI is due to the change in proportion of magnetite and hematite phase with flame front speed.

Influence of limestone particle size on iron ore sinter properties and productivity

AbstractIron ore fluxed sinter is the main ferrous burden of Jindal south west steel limited (JSWSL) blast furnaces. In sinter plant fluxes including limestone and dolomite are added to improve the sinter properties of iron ore and to provide an appropriate slag composition of the blast furnace. The raw material grain size affects the sinter process considerably because the sinter productivity and quality are strongly dependent on the green permeability of the bed, which is determined by the particle size distribution of the raw materials, the granulation effectiveness and by the sintering process itself. It is well‐known that in fluxed sinter, the size of limestone affects productivity and physical and metallurgical properties of the sinter. It is therefore necessary to understand the role of limestone particle size on sinter properties and productivity. In the present work laboratory sintering experiments have been carried out with different levels of limestone mean particle size (from 0.14 to 1.83mm) to understand the influence of limestone particle size on mineralogy, productivity, physical and metallurgical properties of the sinter. Sinter productivity increased with increasing limestone mean particle size due to improved sinter bed permeability. Sinter with limestone mean particle size of 1.25 to 1.52 mm yielded better sinter strength and lower RDI compared to sinter with smaller or larger limestone mean particle size. Higher sinter strength is due to better and uniform distribution of limestone particles, and better bed permeability enabled easy assimilation and effective distribution of calcium ferrite phases. The improvement in sinter RDI is due to change in mineralogy of the sinter compared to coarser and finer limestone mean particle size.