Sinter Plant Research Articles

Electrochemical and Erosion Corrosion Aspect on Main Gas Pipe Line in Sinter Plant: for Raw Petroleum Coke as Trimming Fuel

Different corrosion mechanisms and their extent within a sinter plant gas pipeline were studied. The low temperature-high moisture at the charging side and high temperature-low moisture at the discharging side exist in the main gas pipeline. The waste gas velocity is maximum near charging side and minimum near discharging side. Aggressive conditions near the charging side resulted in faster corrosion than the discharging side. The electrochemical effect was predominant at the wall while erosion effect was significantly higher at the center of the pipe. The overall effect however turns out to be same at wall and center for a particular location of the pipeline. This has been attributed to the velocity effect of waste gases.The corrosion products were characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction XRD techniques. The low temperature-high moisture at the charging side promotes electrochemical reaction with formation of bigger goethite and hematite. Only, hematite was detected in between charging and discharging side where as different iron oxides and alkali compounds were detected near the discharging side.

Use of Raw Petroleum Coke in Sinter Plants

With the augmentation of sinter production in Jamshedpur works of Tata Steel, there was an acute shortage of coke breeze, the usual solid fuel for sintering. This required the use of alternate fuel for sinter making. Raw Petroleum Coke (RPC) was utilized in all three sinter plants of Tata Steel, Jamshedpur works since November 2005. RPC usage went as high as 50% of total carbonaceous fuel used for sinter making. A unique advantage of using RPC is its low ash (nearly 1.5%) compared to that of coke breeze with 22–25% ash. Thus it was possible to lower Al2O3 in sinter from 2.5 to 2.2% consistently. RPC is obtained as a by-product from the petroleum refinery. It is extremely fine in size having −0.25 mm nearly 60% and is highly reactive. RPC also contains volatile matter of about 6–7%, which has implications in suction system. Given the above conditions, it was really a challenge taken by the sinter making team of Tata Steel to adjust the process for using RPC to such a high extent without adversely affecting the quality productivity and equipment health. At some point of time deterioration in sinter quality, particularly in terms of RDI and certain loss in availability and productivity was observed. This paper is to share the experience of Tata Steel in using RPC for sinter making.

Optimization of Coke Breeze Segregation in Sintering Bed under High Pisolite Ore Ratio

Increased demand and the diminishing high grade resources have resulted in a shift to using low grade iron ore in Japanese steel mills. Especially, pisolite ore ratio is quite high. Therefore, decrease in sinter productivity became serious problem with increasing the amount of pisolite ore.To improve the sinter productivity, effective method at the charging device in sintering machine was investigated by laboratory experiments.The following results were obtained.1) It was expected that the holding time over 1200°C at the middle and bottom layer of the sintering bed decreased with high pisolite ore ratio. On the other hand, in order to preserve the sinter strength, it was suggested that the holding time over 1200°C in sintering must be extended under high pisolite ore ratio.2) There is the optimum coke segregation degree according to the pisolite ore ratio. It was decreased with increase of the pisolite ore ratio.3) To control the coke segregation in the sintering bed, Magnetic Braking Feeder (MBF) was introduced, and the operating conditions were investigated with the laboratory charging tests and sintering pot test.4) Based on the fundamental research, MBF has been applied to Keihin No. 1 sinter plant, and the productivity was improved by 4.2% under constant sinter strength.

Separation and Recovery of Potassium Chloride from Sintering Dust of Ironmaking Works

Sintering plant in iron and steel making company generates very fine metal-containing dusts which can present major environmental problems. This paper describes experimental work on a relatively simple and inexpensive process for recovering the potassium chloride and upgrading the iron level of dust from a Chinese plant, to produce saleable potassium chloride product and environmentally safe waste products for reuse. The dust contained about 10–20% potassium as potassium chloride, 20% iron as iron oxides, plus small quantities of lead, copper, cadmium, zinc and other materials. Individual particles of the dust were commonly aggregates of various shapes. Multi-stage countercurrent leaching was taken to completely remove potassium chloride in the ESP dust, but leave iron in the leach residual. With the help of sodium sulfide precipitation, the leached heavy metals were removed from the leaching solutions and a mixture solution which can be perceived as system KCl–NaCl–CaCl2–H2O was left. Then potassium chloride in the system can be separated and recovered by fractional crystallization. At last the mother liquor was returned to the leaching process as leaching agent together with new tap water. This proposed flow sheet was proved feasible through construction of the demonstration unit in the lab, and KCl product with a purity of 96.5% was obtained.

Application of Orthogonal Array Tests Method to Optimize Operating Conditions for Iron Ore Sintering

The objective of this study was to determine optimal operation parameters for increasing iron ore sinter productivity (SP) and sinter strength (SS) during sintering process by using the orthogonal array test method, and examine their emissions. Three operating parameters, including the water content (Wc; range=6.0–7.0 mass%), suction pressure (Ps; range=1000–1400 mmH2O), and bed height (Hb; rang=500–600 mm) were selected for conducting experiments in a pilot-scale sinter pot to simulate various sintering operating conditions of a real scale-sinter plant. We found the resultant optimal combination (Wc=7.0 mass%, Ps=1400 mmH2O, and Hb=500 mm) could increase SP up to 20.2% in comparison with the current operating condition of a real-scale sinter plant (Wc=6.5 mass%, Ps=1200 mmH2O, and Hb=550 mm). The results of the ANOVA analysis indicates that Wc and Ps were the two significant parameters (p<0.05) accounting for 50.3% and 36.7% of the total contribution of the three selected parameters, respectively. The SS of the resultant optimal combination shows no significant difference (only increased 2.2%) as compared with the current operating condition of the selected real-scale sinter plant. By examining the emissions of SOx, NOx, and particulate matters, the values obtained from the optimal combination were quite comparable to those of the current operating condition. The above results further confirm the applicability of the obtained optimal combination for the real-scale sinter production.

Method for Estimation of Na&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;O and K&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;O in Ores, Fluxes, Coal and Coke Ash by Inductively Coupled Plasma-Atomic Emission Spectroscopy

A method for the estimation of Na2O and K2O in the feed materials of sinter plants and blast furnaces, intermediate products like sinter, slag generated in steel plants, using Inductively Coupled Plasma Emission spectrometer is developed. Superiority of this method compared to the conventional techniques with respect to accuracy and repeatability is illustrated. Validation of this method is ascertained by carrying out tests with certified reference materials.

Effect of High-phosphorous Iron Ore Distribution in Quasi-particle on Melt Fluidity and Sinter Bed Permeability during Sintering

The effect of high P Brockman ore on the melt fluidity was investigated to make clear the mechanism for the deterioration of permeability of sinter bed during sintering.Blending high-P ore, characterized by the high porosity and fine size distribution, decreased melt fluidity by the absorption of melt into porous high P Brockman ore. As a result, the pressure drop of sinter bed increased during sintering by the suppression of pore growth, and the sinter productivity decreased.To improve the sinter productivity using high-P Brockman ore, JFE Steel has developed an advanced granulation process characterized by segregating high-P Brockman ore at the center of quasi-particle, which was coated by coke breeze and limestone. It is important to select the suitable coating thickness of dense hematite ore around porous iron ore for preventing from the melt absorption into iron ore. This process controls the excess melting reaction between iron ore and limestone, owing to the segregation of high-P ore within the quasi-particles.The commercial plant trials showed that the desirable melt fluidity, resulting from the segregation of high-P ore in a quasi-particle, enhanced the permeability of sinter bed at Fukuyama No. 4 Sinter Plant of JFE Steel. The application of new granulation process remarkably improved both the productivity and reducibility of sinter products, in spite of the recent inferior ore conditions.

Influence of Process Changes on PCDD/Fs Produced in an Iron Ore Sintering Plant

This study investigated the influence of different charge typologies and additives on the PCDD/Fs amount produced and on the congener profiles in an iron ore sintering plant. Many tests were carried out combining different typologies of charge (iron materials) and solid fuel (“coke breeze” or “anthracite”) with or without the use of urea. The PCDD/Fs produced ranged from 1.2 to 22.7 μg I-TEQ/ton of agglomerate, whereas the PCDD/Fs released to the ambient air ranged from 0.10 to 1.92 ng I-TEQ/Nm3 because of cleaning in an electrostatic precipitator (ESP) and a Wetfine scrubber (WS). A more homogeneous charge with a higher amount of fine particles charge appeared to produce a lower PCDD/Fs concentration due to a better combustion but this hypothesis needs further investigations on charges having different dimension particles. Only a synergitic action of urea and anthracite was able to reduce the high PCDD/Fs content due to the bad combustion of the more inhomogeneous charge with a lower amount of fine particles. The congener profile was a typical combustion process fingerprint because the PCDFs predominated, the highly chlorinated congeners (HeptaCDD and OctaCDD) prevailed in PCDDs, whereas in PCDFs the profile was more varied; 1,2,3,4,6,7,8-HeptaCDF was the main contributor to the total concentration while 2,3,4,7,8-PentaCDF was the main contributor to the I-TEQ concentration. Whereas all the parameters under scrutiny influenced strongly the amount of PCDD/Fs produced, they affected only slightly the fingerprint of PCDD/Fs. In all cases studied, the reduction obtained using urea, anthracite, or the more homogeneous charge with a higher amount of fine particles was slightly greater on the higher chlorinated congeners in respect to the lower ones.

Mathematical modeling and simulation in Matlab/Simulink of processes from iron ore sintering plants

This work presents the mathematic models of the basic processes from an iron ore processing plant. Based on the mathematic models, using the Matlab/Simulink platform, it was achieved the simulation of the dosing process and simulation of the sintering process. The achieved mathematic model allows the determination of the material flows in the charge at their chemical composition variation, or at the variation of the reference values of the parameters S, I, r0, c0. Further the simulation, there are obtained the time-variations of the optimal speed for the sintering machine at different distributions of iron ore's temperatures on the sintering band.

Particle size distributions and health-related exposures of polychlorinated dibenzo- p-dioxins and dibenzofurans (PCDD/Fs) of sinter plant workers

This study measured particle size distributions of polychlorinated dibenzo- p-dioxins and dibenzofurans (PCDD/Fs) in two workplace atmospheres of the sintering grate and rough roll shredder in a sintering plant, and to assess their workers’ health-related exposures. We found that the PCDD/F concentration of the sintering grate (site A = 14.47 pg m −3) was lower than that of the rough roll shredder (site B = 17.20 pg m −3). Particle size distributions of PCDD/Fs were in the form of the unimodal with the mass median aerodynamic diameter (MMAD) of 4.74 μm and 5.23 μm, and geometric standard deviation ( σ g) of 3.15 and 2.15 for the site A and B, respectively. The above results suggest that the workplace of the site A had a less fraction of coarse particles than that of the site B. The estimated PCDD/F concentrations of the inhalable fraction (11.0 pg m −3) and thoracic fraction (8.89 pg m −3) of the site A were lower than those of the site B (12.4 and 9.39 pg m −3, respectively). But to the contrary the estimated respirable fraction of the site A (5.05 pg m −3) was slightly higher than that of the site B (4.93 pg m −3). Our results clearly indicate the importance to conduct particle size segregating samplings for assessing human PCDD/F exposures.

Polycyclic Aromatic Hydrocarbon Emission Profiles and Removal Efficiency by Electrostatic Precipitator and Wetfine Scrubber in an Iron Ore Sintering Plant

A monitoring campaign of polychlorinated dibenzo-p-dioxins and dibenzofurans, polyaromatic hydrocarbons (PAHs), and polychlorinated biphenyl was carried out in an Italian iron ore sintering plant by sampling the combustion gases at the electrostatic precipitator (ESP) outlet, at the Wetfine scrubber (WS) outlet, and by collecting the ESP dust. Few data are available on these micropollutants produced in iron ore sintering plants, particularly from Italian plants. This study investigates the PAH emission profiles and the removal efficiency of ESPs and WS. PAHs were determined at the stack, ESP outlet flue gases, and in ESP dust to characterize the emission profiles and the performance of the ESP and the WS for reducing PAH emission. The 11 PAHs monitored are listed in the Italian legislative decree 152/2006. The mean total PAH sum concentration in the stack flue gases is 3.96 μg/N · m3, in ESP outlet flue gases is 9.73 μg/N · m3, and in ESP dust is 0.53 μg/g. Regarding the emission profiles, the most abundant compound is benzo(b)fluoranthene, which has a relative low BaP toxic equivalency factors (TEF) value, followed by dibenzo(a,l)pyrene, which has a very high BaP(TEF) value. The emission profiles in ESP dust and in the flue gases after the ESP show some changes, whereas the fingerprint in ESP and stack flue gases is very similar. The removal efficiency of the ESP and of WS on the total PAH concentration is 5.2 and 59.5%, respectively.

Application of a Peat as an Additive to Prepare Ferrous Gas-Cleaning Sludge for Sintering

The purpose of the research is to increase consumption of iron-bearing gas cleaning sludge to the sintering mix in order to utilize both fresh and stored wastes. Utilizing of iron-bearing sludge produced by gas cleaning facilities of integrated steelmaking plants is an urgent problem. In Ukraine, steelmaking industry produces over 10 million tons of such wastes a year. With Fe content of 35–55% sludge is valuable by chemical composition but its application as component of a burden to produce sinter is challenged with high moisture content and tendency to self-aggregation. Activated peat has been applied as high absorbency additive to sludge. Moisture capacity of a peat ensures absorption of water by this material from the sludge within the whole range of moisture content. Treatment of dehydrated sludge with the peat allows the obtaining of a mixture with mechanical properties comparable to those of other sintering mix components. Preparation of sludge produced by wet gas cleaning systems of blast furnaces, sintering plant, BOF (basic oxygen furnace), and open-hearth furnaces while mixing with peat during formation of piles has been experimentally investigated. Increasing of sinter yield ratio and plant productivity in the industrial conditions has been observed.

Characterisation of volatile organic compounds and polycyclic aromatic hydrocarbons in the ambient air of steelworks

Investigations have been undertaken at two integrated steelworks in the UK to characterise airborne organic micro-pollutants and to assess the contribution of iron ore sintering and coke making operations on the air quality. Concentrations of volatile organic compounds (VOCs), namely benzene, toluene and p-xylene, were measured continuously within the boundary of a coking plant using for the first time differential optical absorption spectrometry (DOAS) between 2004 and 2006. Concentrations were obtained along two monitoring paths surrounding the coke plant and the average benzene concentration measured along both paths over the campaign was 28 μg m −3. Highest benzene concentrations were associated with winds downwind of the coke oven batteries. Concentrations of polycyclic aromatic hydrocarbons (PAHs) in ambient air were measured during 27 consecutive days in 2005 at three different locations on an integrated steelworks. PAH profiles were determined for each sampling point and compared to coke oven and sinter plant emission profiles showing an impact from the steelworks. The mean benzo [ a] pyrene concentration determined in the immediate vicinity of the coke ovens downwind from the battery was 19 ng m −3, whereas for the two other sites average benzo [ a] pyrene concentrations were much lower (around 1 ng m −3). Data were analysed using principal components analysis (PCA) and results showed that coke making and iron ore sintering were responsible for most of the variation in the PAH concentrations in the vicinity of the investigated plant.

Project to increase sinter machine productivity aiming at attending the ArcelorMittal Tubarão expansion plan for 7.5 million tons/year

In order to increase their production of steel plates to 7.5 million tons/year, ArcelorMittal Tubarão faced the challenge to increase sinter plant productivity from 34.00 t/d/m2 to 42.00 t/d/m2. This was achieved in June 2006 through three main actuators: raw materials, stabilization and optimization of the current equipment and implementation of new technologies.

Granulometric optimisation of raw materials for ISF continuous segregation system in Usiminas' sintering plants

This paper describes the improvement in the operational results obtained in the sintering unit of Usiminas' Steel Works, located at Ipatinga, one of the integrated steel plants in Brazil, after incorporation of intensified sifting feeder in the sintering circuit. Beneficial results came about after extensive investigations involving alterations to particle sizes of the feed material comprising of different types of iron ore, limestone, solid fuels and other additives such as serpentinite. The present work describes the methodology developed for sampling, including variations in the particle sizes of the feed mix, and their effect on the operational results of the sinter plant in respect of productivity and quality of sinter produced. The beneficial effect of serpentinite additions has been confirmed.

Investigations into dioxin emissions at Italian iron ore sintering plant

The paper presents the results of tests performed on an existing iron ore sintering plant to evaluate the limiting capability of dioxins releases to air and of measures and technologies adopted. These measures and technologies are in line with the best available techniques as stated in the Integrated Pollution Prevention and Control Directive 96/61/EC, so a measurement campaign was planned to determine the operating conditions capable of complying with the legislation in force. In this paper, the authors define the running conditions tested and the manner in which the testing campaign was performed. The results are presented and analysed in the light of the aims of the study.

A seasonality study of polychlorinated dibenzo- p-dioxins and dibenzofurans in ambient air in Kaohsiung (Taiwan) clustered with metallurgical industries

As a comprehensive monitoring survey on polychlorinated dibenzo- p-dioxins and dibenzofurans (PCDD/Fs) in Kaohsiung, 40 ambient air samples taken from 10 locations in four seasons were studied. PCDD/F concentrations at 0.312–4.58 pg N m −3 and I-TEQ values, ranging from 0.0319 to 0.256 pg N m −3 were determined for these samples, which were comparable to those of other urban cities. However, unlike studies on some other urban cities, the ambient air in Kaohsiung did not exhibit regular seasonality in PCDD/F concentrations. All samples were predominated, in common, by congeners OCDD, 1,2,3,4,6,7,8-HpCDF, 1,2,3,4,6,7,8-HpCDD, OCDF and 2,3,4,7,8-PeCDF. The congener profiles of the samples generally did not display any seasonal trend, either. The insignificant seasonality and constancy of congener profiles with time were attributed to the constant influence by emission sources in a metal-producing center, thereby resulting in high atmospheric dioxin levels in the nearby district. Principal component analyses identified that dioxin emissions in ambient air of the city originated from electric arc furnaces (EAFs) and sinter plants in the center. Concentration isopleth analyses assessing pollution sources and ambient air of the district also confirmed that its atmosphere was affected largely by the EAFs and sinter plants.

Redesigning exhaust-gas recirculation systems in sintering

The recirculation of hot gases (air from the sinter coolers or the cooling zone, sintering waste gases) permits energy conservation and environmental protection in sinter production. A benefit of gas recirculation is the reduced atmospheric emission of harmful materials (CO, CO 2 , H 2 S, SO 2 ) and dust. One common method of hot-gas recirculation is to return some of the waste gases from the flue to the bed over the length of the sintering machine. The gases are sent to the cover through special distributors: tubes, slots, etc. The basic measure of the efficiency of this technology is the degree of recirculation r , equal to the ratio of the bulk flow rate of recirculating gases to the cover and the total flow rate of gases through the exhaust pump. The dependence of the sintering productivity on r was studied in [1]. At first, the productivity increases with increase in r to 15%, reaching a maximum (102%) with respect to sintering in the absence of circulation, and then declines to 93% when r = 45%. The sintering productivity, estimated in terms of the sintering time, depends on the composition of the recirculating gases (the concentration of oxygen and water vapor) and also on their temperature, according to [2, 3]. These parameters, in turn, depend on r . On introducing such technology at Nippon Steel sintering plant 3 (Tobata, Japan), the degree of recirculation was chosen so as to maintain a waste-gas temperature eliminating acidic corrosion of the electrofilters: r = 25% [2]. The maximum r at which no moisture accumulates in the gases and sintering is possible is 35.5%, according to [4]. The maximum r may also be determined on the basis of the gas balance of the sintering machine’s vacuum system. The bulk gas flow rate through the exhaust unit V exh may be expressed in terms of the bulk flow rate of gases drawn through the surface of the cake V ca (nm 3 /s) where γ takes account of the increment in gases in the bed on sintering; χ takes account of the proportion of leaks through imperfections of the sintering machine V exh V caγχβt, = and its gas channel; β t is the temperature coefficient of bulk expansion of the gases. Then, in accordance with the definition adopted, the degree of recirculation r , %, may be written in the form Hence, the dependence of r on the gas-dynamic parameters of the sintering machine is obvious. Existing methods are based on a technological approach to calculating the maximum permissible r but take no account of the implementation of the technology: the design of the equipment; the sealing of the cover; or the method of delivering gases to the cover. Experience shows that these factors determine the maximum possible r with no loss of gases through existing imperfections and apertures of the cover and hence with safe operation of the sintering equipment. These aspects of the equipment are taken into account in a new model of heat and mass transfer in the cover. The model is based on analysis of the gas balance of the cover under the action of the pressure difference created by the exhaust fan and under the action of gravitational forces.

Crushing hot sinter with the use of cantilevered grates

The sinter plant operated by the Cherepovets Metallurgical Combine Severstal’ is using cantilevered grates to crush the hot sinter. The use of such grates solves the problem of improving the durability of the crushing machines and results in a substantial monetary savings.

Polychlorinated dibenzo- p-dioxin and dibenzofuran emissions from an industrial park clustered with metallurgical industries

Emissions of polychlorinated dibenzo- p-dioxins and dibenzofurans (PCDD/Fs) from an industrial park operated as Taiwan's center of metallurgical industries were investigated. The characteristics of mean PCDD/F I-TEQ concentrations, congener profiles and emission factors of each source were studied over samples of stack flue gases of individual sources. Different characteristics of congener profiles and large variations of emission factors of secondary aluminum smelters (ALSs) were observed. The mean emission factors of electric arc furnaces were comparable to those for ALSs and much greater than those of municipal solid waste incinerators and sinter plants, but still less than that of clinical waste incinerators. Annual PCDD/F emission contribution of each source was estimated, raising critical concerns over the overall PCDD/F emissions from metallurgical processes. The metallurgical industries altogether contributed ∼98.1% of the total annual emissions, while waste incinerators only 1.9%. The contributions by sinter plants and metallurgical industries to the total annual emissions of the Park were much higher than the corresponding national averages of Taiwan. The combined dioxin emissions from the entire metallurgical processes and their controls should be seriously envisaged by industrial parks devoted to metal productions.