Sinter Plant Research Articles

Mechanical properties of dust collected by dust separators in iron ore sinter plants

The flow-related mechanical properties of dusts from the de-dusting systems of several sinter plants were investigated. The mass median diameters of the dusts were in the range from approximately 3 to 100 µm. Also, the bulk density of the dusts varied in a wide range (approximately 400 to 2300 kg/m3). A good correlation between the bulk density and the mass median diameter for most of the dusts was found. In contrast, the angles of repose did not vary very much, only for the coarsest dust a significantly lower value was measured. The angles of internal friction as well as the wall friction angles were lower for coarse dust and higher for fine dust. The shear tests showed that both angles depend considerably on the stress level. At low stress, the angles decreased significantly with increasing values of stress, whereas at higher stress, the dependence was small or even disappeared. The only exception to this behaviour was shown by the finest dust. The flowability decreased with the particle size. The flowability categories suggested by the three flowability indicators were passable only for the coarser dusts. For the finer dusts, the flowability was overestimated by all flowability indicators.

Life Cycle Assessment of Iron Ore Sintering Process

Iron ore sintering is an energy-intensive process associated with emission of pollutants in iron and steel industry. In order to comprehensively evaluate the environmental impacts of sintering, a detailed life cycle assessment of a sintering plant was conducted. Life cycle inventory showed that, in the production of 1 t sinter ore, 241. 53 kg CO2, 22. 68 kg CO, 0. 294 kg SO2, 0.63 kg NOx, 1.18 μg dioxin and 0. 48 kg dust were discharged. Global warming potentials, acidification potentials, photochemical ozone creation potentials and human toxicity potentials were selected as four impact categories, and the evaluation index for the sintering plant was calculated as 3. 45 × 10−12. Finally, based on the environmental impact analysis, several measures of reducing environmental loadings of the sintering plant were provided, which included the utilization of denitrification equipment, recirculation of the hot waste gas and process improvement to reduce fuel consumption.

Searching the Possibility of Electricity Production with Waste Heat Recovery from Iron and Steel Factory Sinter Cooler by ORC

Accepted: 15.043.2015 Requirement of energy in the life of humanity has been increasing everyday more than one day before, but in the meantime energy sources have been running out rapidly. Efficient usage of energy is sufficiently important for industrial facilities to resist the competitive conditions in the market by the reduction in cost of energy consumption and unit product cost. In this regard, waste heat recovery potential during the ore cooling process at an iron and steel facility sinter plant by using ORC system was theoretically investigated. As a result, it is determined that about 10% of 9,527 kW waste power potential would be recovered to electricity in the industrial facility by the establishment of organic Rankine cycle (ORC). Environmentally, about 5001 tones CO2/year emission release by the combustion of coal to generate equal amount of electricity was eliminated by electricity generation by ORC. The payback period of the possible ORC system investment was foreseen about 2.4 years.

Iron ore sintering. Part 3: Automatic and control systems

The sintering process involves a large number of parameters, more than 500, each of which exerts a greater or lesser influence and needs to be controlled, within the possible limits, in order to optimise productivity, process stability, and standardise the composition and quality of the sinter produced. To comply with environmental legislation, a pollution control system must monitor the particle matter and gases generated and emitted into the atmosphere by the sinter plant. Automation and control systems are vital tools to assist plant operators in the monitoring of each stage of the sinter production process.

Development of AISI A2 Tool Steel Beater Head for an Impact Crusher in a Sinter Plant

Failure analysis of a tool steel (AISI A2) beater head of an impact crusher and development of suitable heat treatment process to improve its performance have been presented. The beater heads were failing prematurely by brittle fracture from its pin-hole locations. The investigation consisted of visual inspection, fractography, chemical analysis, characterization of microstructures using optical and scanning electron microscopes (SEM), EDS analysis, and determination of micro-hardness profile. Microstructural characterization using SEM and EDS analysis revealed significant amount of coarse continuous Cr-carbide networks in the martensite matrix. It increased hardness (64 HRC) as well as heterogeneity of the matrix as depicted by the micro-hardness profile, and decreased the toughness (3 J) since coarse carbide networks are very hard and brittle. The austenitizing temperature as well as tempering temperature of heat treatment was found lower at the manufacturer’s end. The new recommended heat treatment resulted in lower amount of discontinuous Cr-carbides along with significant amount of fine precipitates uniformly distributed throughout the matrix which led to an optimum combination of both hardness (59 HRC) and toughness (6.5 J) required for the application. The beater heads manufactured following the recommended heat treatment exhibited better performance (life increased by 4 times) compared to the earlier ones.

Leaching of the residue from the dry off-gas de-dusting and desulfurization process of an iron ore sinter plant

The residue from a second-stage dry sinter plant off-gas cleaning process contains both the fine dust from the sinter plant and the sorbent used. Recycling of the material that is usually handled by landfills to the sinter plant feed is not possible because of its chloride content. Leaching of the chlorides allow the recycling of remaining solids. The saline leachate produced contains some heavy metals and must be treated before it is discharged into the sea. In laboratory experiments, leaching tests with the subsequent treatment of the leachate were conducted. After the process was optimized, all heavy-metal concentrations were below the permissible values. The optimum treatment conditions for heavy-metal precipitation were observed to be the filtration of the suspended solids followed by the dosing of liquid with lime milk (pH 10) and the subsequent precipitation using sodium sulfide.

Practical and Theoretical Research on the Sintering Process

The Novolipetsk Metallurgical Combine (NLMK) has collaborated with leading scientific-research institutes and scientists in the area of sinter production for decades. The combine’s sinter plant has been used to conduct many factory tests, and the results of those tests have helped refine and advance the theory of the main processes which take place during the sintering of iron-ore-bearing materials. The theoretical gains have in turn facilitated the introduction of a number of effective technologies. 1. Charging of the mix onto the sintering machine. During the 1980s and 1990s, several foreign sinter plants that sinter coarse-grained charges began to abandon the practice of two-layer charging that had been used on the sintering machines at the NLMK and the West-Siberian, Cherepovets, and Karaganda metallurgical combines. The change from twolayer charging brought about marked increases in sinter production, which led to study of the effect of different factors on the performance of the sintering machines at the NLMK with the use of two-layer and one-layer charging [1, 2]. This was the first such study for sinter plants that operate on iron-ore concentrates. The factory tests established the following [1]: 1) the unit gasdynamic resistance of the bottom third of the lower layer of a two-layer charge is 1.8 times greater than that of the middle third and 4 times greater than that of the top third. Thus, the factor which limits sintering rate is not the boundary layer (although it makes its own negative “contribution”), as was stated in [2]. Instead, the limiting factor in this case is the lowest part of the bottom layer; bulk density in this part is greater and the high-temperature range is broader than in the overlying parts of the layer; 2) the average gas-pressure gradient in the lower half of the bottom layer of the charge is about 70% of the total resistance of the layer; 3) the transition to one-layer charging increases the sintering rate by 10%, which confirms that there is a net improvement in the gasdynamic structure of the layer; and 4) the content of the ‐5-mm fraction in the skip sinter rose by 0.2 abs.%.

Utilization and Improvement of the Adsorption Method for Sampling PCDD/Fs from a Sinter Plant

ABSTRACTIn this work, the Adsorption Method for Sampling (AMESA) is developed to collect long-term samples of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) from stacks. However, the variation of in duration might affect the analytical results due to the memory effect in the AMESA. This research is one of the very few reports of using AMESA in sinter plants. Eight long-term AMESA (LA) samples were collected, followed by 16 parallel short-term AMESA (SA) and manual (SM) samples. The LA reports good correlations (R = 0.82–0.83) between PCDD/F emissions and the recovery feedstock, which can be further used for emission reduction. However, the breakthrough effects of the highly chlorinated PCDD/Fs is in the range of 6–14% in LA samples, and these are further improved by increasing the glass wool and adsorbent (with higher specific surface area, lower pore size, and higher polarity) packing, and finally reduced to 5.17%. For the short-term sampling, a maximum difference of 170% occurred between SA and SM, if the sampling strategy suddenly changed from LA to SA. The PCDD/F memory effect remained for the first 8 SA samples, with the dominant 1,2,3,4,6,7,8-HpCDD and OCDD. Therefore, five post-washings for the AMESA system took place to successfully reduce the PCDD/F residual mass to > 0.2% of a normal LA. Unfortunately, these residuals were still equal to 51.4% of a normal SA. Therefore, it is not suggested that AMESA replace the current manual sampling method without any modification. According to this study, both the breakthrough and memory effects could be inhibited. Finally, a new inspection system, including both AMESA and short-term samples, is then proposed for improving the PCDD/F control strategy in Taiwan.

Sinter Production at the Novolipetsk Metallurgical Combine: Traditions, Innovations, Growth

The Novolipetsk Metallurgical Plant was built in the 1930s and made foundry iron for machine-building plants, but during the 1960s and 1970s it became a metallurgical combine having the most modern and largest sinter plant and blast furnaces in the USSR. Equipment modernization and improvements to the technologies that are used increased the productivity of the sinter plant by 25%. The productivity of the combine’s blast furnaces has increased 20% thanks to an improvement to the quality of the coke and sinter during 2013–2014, and the new blast furnace Rossiyanka, built in 2011, is setting a new record for productivity – 87–89 tons/m2 per day.

Reducibility mill scale industrial waste via coke breeze at 850-950ºC

Mill scale is a very attractive industrial waste due to its elevated iron content (about = 69.33% Fe) besides being suiTab. for direct recycling to the blast furnace via sintering plant. In this paper the characteristics of raw materials and the briquettes produced from this mill scale were studied by different methods of analyses. The produced briquettes were reduced with different amounts of coke breeze at varying temperatures, and the reduction kinetics was determined. The activation energy of this reaction ? 61.5 kJ/mole for reduction of mill scale with coke breeze in the form of briquettes with 2% molasses where the chemical reaction interface model is applicable.

事前還元鉱石の焼結原料としての使用によるCO2排出削減

In order to reduce CO2 emissions at an ironmaking process, it is an effective measure to decrease a bonding agent rate at an iron ore sinter plant. In this study, effect of using a pre-reduced iron ore as a part of a sinter raw material on a sintering process was investigated mainly from a viewpoint of decreasing a bonding agent rate.Two brands of pisolitic iron ores were reduced up to wustite at 1173 K with reducing gas of which an oxidation degree was 55%. The pre-reduced iron ore was stable against reoxidation in the atmosphere and through a cyclic wet and dry treatment.Two brands of pisolitic iron ores and a Marra Mamba iron ore were pre-reduced and then used in a sinter pot test. A use of the pre-reduced iron ore was effective in decreasing a bonding agent rate at a given productivity. The reoxidation heat of the pre-reduced iron ore was estimated to be less than the combustion heat of the bonding agent being saved by use of the pre-reduced iron ore. The reoxidation heat is more effective in the sintering process than the combustion heat. The decrease of the bonding agent resulted in reduction of NOx emissions.A mass and heat balance shows that a use of a pre-reduced iron ore as a sinter raw material enables reduction of CO2 emissions not only at an ironmaking process but also at a whole integrated steel works.

The study of the amount of heat release in the sinter charge layer

Based on the data on the chemical composition of charge at the sinter plant MK Zaporizhstal (Ukraine), dependencies, allowing to determine the amount of released and absorbed heat energy per unit volume of the sintered charge by the layer height from the average diameter of the material particles were obtained in the paper. Equations, allowing to calculate the amount of heat energy, released and absorbed per unit volume of the charge as a result of the combustion of the fuel particles and exo- and endothermic reactions, proceeding therein are presented. The results allow a close approach to the problem of the optimization of the thermal regime of the agglocharge sintering process on the author's model, based on finite element method, which takes into account the internal heat release per unit volume, as well as determination of polydisperse charge layer formation laws for rational distribution of fuels and chemical components by the height of the agglomerated layer.

Exergy and Its Efficiency Calculations in Ferrochrome Production

Ferrochrome production is a high energy intensive process consuming around 3000 to 3500 kWh/t of electrical energy. Ferrochrome is produced by smelting of different grades of chromite ore with coke and fluxing agents such as lime, dolomite, and quartz in a submerged arc furnace (SAF). Apart from the production of ferrochrome, co-products that are produced during the process include carbon monoxide rich off-gas and slag. The slag is cooled with high pressure jet water which results in the formation of slag granules. In the present practice, off-gas generated from the SAF is used for ladle preheating, as fuel in sinter plant, while the remaining is unutilized. Approximately 34 to 40 pct of heat from off-gas is utilized, while the remaining 60 to 66 pct of the off-gas can be utilized for generating electricity by gas combustion turbine. The concept of exergy is applied to monitor the existing process and to understand the feasibility of modification. In the present study, comparison of exergy efficiency for existing process and two adapted case studies has been performed, involving utilization of off-gas for sintering and power generation and waste heat utilization from dry slag granulation. It is observed that there was considerable increase in exergy efficiency for waste heat utilization by dry granulation case study when compared with other two case studies.

Application of air classification for improved recycling of sinter plant dust

In sinter plants the dust collected from the off-gas is recycled back to the feed material as long as the chloride content of this dust in below the plant-specific limits. To avoid an up-cycling of chloride in the system in many sinter plants the dust from the last field of the electrostatic precipitator is excluded from recycling since the chloride concentration is higher in the dust collected in the rear fields of the electrostatic precipitator. In this study the application of air classification is investigated to raise the dust recycling rate and/or to increase the chloride discharge. Samples from each field of the four field electrostatic precipitator of an iron ore sinter plant were classified and analyzed. The mass-recovery – chloride-removal functions for various classification variants were calculated by using approximation functions for the mass and the chloride content of the particle classes produced. The results show that in comparison with the actual situation where about 20% of the sintering dust which contains about 30% of the chloride is excluded from recycling, by applying air classification the recycling rate could be increased to about 95%, retaining the same chloride discharge rate. In the case of the expected extraction of potassium from sintering dust in the future, air classification could also be used to increase the potassium chloride concentration of the input material.

Immobilization of iron rich steel industry waste and products characterization

The steel industry produces large amount of wastes, some of which are today used in other industrial sectors; iron oxide rich wastes are difficult to recycle and vitrification is one of the most efficient techniques to stabilize them and produce materials suitable for new applications. The waste considered in this study comes from the purification of fumes captured by hoods during agglomeration process in the sinter plant. These dusts have been vitrified on a laboratory scale by the addition of glass cullet coming from diversified harvest of municipal waste, varying the glass/dust ratio from 80:20 to 50:50. The as produced materials have been characterized by means of XRD analysis and SEM images, and leaching tests have been carried out to evaluate their chemical stability. The electrical and magnetic properties of these iron rich materials have been evaluated too. The resistivity of the samples produced with 45% and 50% of waste are 20 and 1.5×103Ωm respectively, considerably lower than the common soda-lime glass resistivity value (1012Ωm). Moreover the materials show a ferromagnetic behaviour; the Curie Temperature of the materials lies in the range from T=395°C to T=533°C, confirming the presence of magnetite/maghemite phases.

Residues from single-stage dry de-dusting and desulphurization of sinter plant off-gas: enabling partial recirculation by air classification

In iron ore sinter plants, the process off-gas is de-dusted by electrostatic precipitators which are installed upstream of the fan. For further reduction of emissions, a second cleaning stage can be installed. This stage usually comprises a sorption process for removal of acid gases and polychlorinated dibenzo(p)dioxins and furans, followed by a fabric filter. The residue from the first de-dusting stage can be recirculated to the sintering process. The residue from the second cleaning stage has to be disposed of in landfill sites. A new single-stage off-gas cleaning concept for sinter plants comprises an entrained flow sorption process and a fabric filter, installed upstream of the fan. In this way, the investment costs for the off-gas cleaning system can be reduced significantly. However, it would become necessary to dispose of most of the residue. In this work, air classification of a residue equivalent to that of a single-stage off-gas cleaning unit was investigated with the aim of producing a fraction of this residue with reduced sulphur and chloride concentrations which can then be recycled. The results confirm that air classification is a suitable process. In order to maintain raw mixture targets for chlorine or to avoid chlorine enrichment in the raw feed, the recommended dust recycling rate is 66 % with air classification which is an improvement over the allowed rates without air classification of 42 %.

Advanced monitoring system of sinter plant

A correct management of the sinter plant is crucial for the productivity of an integrated steelwork, as the sinter quality has a direct and considerable impact of the blast furnace productivity and efficiency. To this aim, it is of utmost importance to continuously monitor the sintering process in order to preserve its stability as well as the homogeneity of the combustion along the entire length of the sinter bed. In particular, the permeability of the sinter mix once it lays on the strand is a crucial factor to monitor in the different areas of the bed together with the temperature distribution on the final part of the strand, just before the material discharge in the crusher. The charging gates, on the other hand, are the most natural mean to affect permeability itself, as their opening levels affect the distribution of the material on the strand. Here an innovative monitoring system is presented, which have been installed and tested at ILVA Taranto Works and integrates a series of measuring devices distributed on different zones of the machine. All the information collected by the sensing system is jointly exploited in order to obtain a clear and updated picture of the ongoing process, by providing a valuable support to plant engineers and technicians managing the sinter machine both for standard operations and for programming maintenance interventions.

Development of Methods and Technologies at the Sinter Plant

are presented from the implementation of several technical and technological measures aimed at making sinter production at EZRAZ ZSMK more efficient. The measures have elevated the technical-economic indices of the sinter plant, increased sinter output, reduced sintering-machine downtime, and improved the sinter's quality characteristics.

Laboratory iron ore sintering studies. 1. Process simulation and airflow rate

Iron ore sintering is the most popular process used to produce a suitable feed for the blast furnace. With changing iron ore supplies and composition, steel mills have to continually adjust the blended ore mix composition to the sinter plant. To help decision making in this area, and also obtain increased understanding of the process to allow improvements in sintering operations, laboratory-scale sinter pot tests are conducted. The use of a pot for routine testing and for research is discussed. When used as a research tool, the experimental approach used to simulate a plant will have to be modified to facilitate the interpretation of results. Airflow rate through a bed is a critical parameter and this paper highlights the important relationship between post- and pre-ignition airflow rates and also the effect of changing bed suction and coke level in the sinter mix.

Rebuilding the Sinter-Plant Gas Aspiration and Cleaning Systems at the Magnitogorsk Metallurgical Combine

A brief analysis is made of the systems currently used for aspiration, dust collection, and cleaning of gases exhausted from the front parts of the sintering machines in sinter plant No. 3 and the rear parts of the sintering machines in sinter plant No. 4 at the Magnitogorsk Metallurgical Combine. An evaluation of the performance of these systems shows that they need to be rebuilt. Recommendations are given for the design of upgraded aspiration and gas-cleaning systems, and it is shown that the upgrade can be performed without reducing the present volume of sinter production.