Iron Ore Sintering Plant Research Articles

Mechanical and Flow Properties of Residue from Dry Desulfurization of Iron Ore Sinter Plant Off-Gas

Abstract In off-gas desulfurization in sinter plants, dry systems consisting of a sorption process for the separation of sulfur dioxide and a fabric filter for final dedusting are normally used. As a rule, hydrated lime is the base sorbent although sodium bicarbonate can be an alternative. Mechanical and flow properties of the residues produced are relevant for the design of handling and storage facilities for these materials. In this study the mechanical and flow properties of residues from three dry off-gas desulfurization systems were investigated. The particle size and the density of all three residues were very similar, but all other parameters measured differed depending on the sorbent used. Bulk density of the residues from lime-based desulfurization was higher and the flowability was better. This has to be taken into account when a change of the desulfurization reagent from Ca(OH)2 to NaHCO3 is considered. Generally, the flowability of the residues was poor at low consolidation stress and improved...

Iron and copper catalysis of PCDD/F formation.

The formation of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F) was explored during de novo tests designed to compare the catalytic activity of copper (II) chloride (CuCl2) with that of iron (III) oxide (Fe2O3) and to test some synergistic effect between these two catalytic compounds. Both copper chloride (CuCl2) and iron oxide (Fe2O3) were earlier proposed as catalysts to explain the PCDD/F emissions from, e.g. municipal solid waste incineration (MSWI). In addition, haematite (Fe2O3) is the main iron ore and could be responsible for the typical iron ore sintering plant fingerprint. A total of nine model fly ash (MFA) samples were prepared by mixing and grinding of sodium chloride (NaCl), activated carbon and a powder matrix of silica (SiO2) with the selected metal compound(s). The conditions of these de novo tests were 1 h in duration, 350 °C in a flow of synthetic combustion gas (10 vol.% oxygen in nitrogen). The effect of Fe-Cu catalyst concentration on yield and distribution pattern of PCDD/F was systematically explored; three strongly differing ratios of [Fe]:[Cu] were considered (1:1, 10:1 and 100:1) to study the potential interactions of Fe2O3 and CuCl2 suggested earlier. The results show some slight rise of PCDD/F formed with raising iron concentration from 0 to 10.1 wt% (no Cu added; 0.1 wt% Cu), as well as strong surging of both amount and average chlorination level of PCDD/F when rising amounts of copper (0 to 1.1 wt%) are introduced. The resulting fingerprints are compared with those from sintering and from MSWI.

Reducing polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F) emissions from a real-scale iron ore sinter plant by adjusting its sinter raw mix

This study was conducted in a real-scale iron ore sinter plant for reducing emissions of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) from the iron ore sintering process via the adjustment of its sinter raw mix. Based on operating condition of the selected plant, four experimental campaigns of Cref (currently used raw mix, served as the reference), CH (modified from Cref, with a 15% increase in hematite but 15% decrease in limonite), CH,EP (modified from CH, without electrostatic precipitator (EP) and blast furnace (BF) flue dusts), and CH,EP,W (modified from CH,EP, with a 0.5 wt% increase in water content) were chosen. For each experimental campaign, three replicate samples of PCDD/Fs were collected from the flue gases, and the sinter productivity and sinter strength were measured simultaneously. In comparison with Cref, the most significant reductions in PCDD/F and I-TEQ emissions was found in CH,EP (=68% and 76%, respectively), and the main reduction was found in PCDFs (54–76% decrease). CH could reduce emissions of PCDD/Fs and I-TEQ by 47% and 51%, respectively. But the addition of water contents (i.e., CH,EP,W) did not result in further reductions. Since sinter productivity and sinter strength of all experimental campaigns were quite similar, CH,EP could be a promising raw mix for reducing PCDD/F emissions from the sintering process.

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.

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.

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.

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.

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 %.

PCDDs/Fs Pollution from Metallurgical Processes in the Town of Sisak, Croatia

Abstract In order to calculate the emission of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans from metallurgical processes located in the town of Sisak, Croatia, this research has built on experiences from developed countries, where the emission factor values from individual metallurgical processes have been taken from the reference data and used for the estimate of the emission of these pollutions in the European countries. The calculation of the emission polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans from metallurgical processes located in the town of Sisak took into account annual outputs of sinter, pig iron, steel blooms and steel billets, as well as steel casts. The metallurgical processes installed in the town of Sisak between 1950 and 2010 emitted from Q1-TEQ =17 mg a-1 PCDDs/Fs in 2001 to Q1-TEQ =5823 mg a-1 in 1989, depending on the activity of these processes. Within the observed period, the largest source of PCDDs/Fs emission was the iron ore sintering plant. Within the observed timeframe, the town of Sisak did not experience any excessive air, soil or water pollution by polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans from the local metallurgical processes.

Life cycle assessment of steel production in Poland: a case study

Abstract The goal of this study is to perform a life cycle assessment (LCA) of steel production through the integrated steel production and electric arc furnace routes in Poland. The study defines the major sources of environmental impacts and proposes pollution prevention methods for the most pollutive steelmaking processes. The LCA methodology based on the ISO 14044 standard is used with SimaPro 7.3.3 software and the Ecoinvent database. The life cycle inventory shows data averaged from the existing steel plants in Poland, and the impact assessment results indicate that the production of pig iron in blast furnaces has the highest impact on greenhouse gas emissions and fossil fuel consumption in the national integrated steel production route, while the iron ore sintering process, which is the largest contributor to dust and gas emissions in the national iron and steel industry, uses the most minerals and depletes the most metal. Electricity consumption has the highest impact on greenhouse gas emissions and fossil fuel consumption in the national electric arc furnace route. Therefore, this article presents the results of an LCA of alternative fuel consumption in a national iron ore sinter plant. The study concludes that pollution prevention methods related to raw material substitutions in iron-making processes should be used to reduce environmental impacts in the iron and steel industry. The results of this study can be used as the first step in performing a full cradle-to-grave steel LCA that includes all phases of the steel life cycle.

Reduction of CO2 Emissions by Use of Pre-reduced Iron Ore as Sinter Raw Material

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.

Emission characterization of unintentionally produced persistent organic pollutants from iron ore sintering process in China

Emission of unintentionally produced persistent organic pollutants (Unintentional POPs), including polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), polychorinated biphenyls (PCBs), hexachlorobenzene (HxCBz) and pentachlorobenzene (PeCBz), were investigated in four typical iron ore sintering plants in China. The emission factors and annual mass releases of the Unintentional POPs were calculated. The results indicated that PCDFs contributed more than 60% to the overall toxic equivalent quantity (TEQ) values, while the contribution of the dl-PCBs is relatively low, and only in the range of 8–9%. The dominant congeners of PCDD/Fs and dl-PCBs contributing most to the total TEQ were 1,2,3,7,8-PeCDD, 2,3,4,7,8-PeCDF and PCB-126. With regard to the TEQ contributions, the most abundant homologues were PeCDFs and HxCDD/Fs, followed by PeCDDs and non-ortho dl-PCB, whereas HpCDD/Fs, OCDD/Fs and mono-ortho dl-PCBs almost made no contributions. Due to the massive use of recycled waste in the feeding materials, the average emission factor of PCDD/Fs and dl-PCBs of the four plants was 3.95μgWHO–TEQton−1. Based on the results, the annual release of PCDD/Fs and dl-PCBs in 2007–2009 were estimated to be 2070g, 2212g, and 2307gWHO–TEQ, respectively.

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.

Characteristics of fly ash from the dry flue gas desulfurization system for iron ore sintering plants

The characteristics of fly ash from the flue gas desulfurization (FGD) system are important for its reuse and are mainly depend on the desulfurization process. The physical and chemical properties of DSF ash, which refers to fly ash from the dry FGD system for the iron ore sintering process, were investigated. Its mineralogical contents were determined by X-ray diffraction and thermogravimetry analysis, and its micro-morphology was studied by scanning electric micrograph analysis. The results show that DSF ash has a higher CaO and SO3 content, and the main sulfur form is sulfite, with only a part of it oxidized to sulfate. The major minerals present in DSF ash are hannebachite, anhydrite, calcite and portlandite; a minor constituent is calcium chloride. The particles of DSF ash are irregular, fragmentary and small, and hannebachite grows on their surfaces. Particle size is affected by the FGD process, and the ash size from the maximized emission reduction of the sintering–FGD process is lower than that from the circulating fluidized bed–FGD process. The particle size distribution of DSF ash follows the Rosin–Rammler–Bennet equation.

Dramatic diatom species assemblage responses in lakes recovering from acidification and metal contamination near Wawa, Ontario, Canada: a paleolimnological perspective

Several lakes near Wawa (Ontario, Canada) present a rare opportunity for studying rapid chemical and biological recovery from acidification and metal contamination. Surface water pH levels in some of these lakes have increased from 3 to 7 following local sulphur emission reductions and closure of an iron ore sintering plant. We used paleolimnological techniques to track diatom community responses to historical water quality changes in five lakes. Pre-industrial diatom assemblages recorded in lake sediments were dominated by species typical of circumneutral pH levels and were characterized by minimal species compositional change. Following the onset of sintering in 1939, there was a striking shift towards acid- and metal-tolerant Eunotia -dominated species assemblages, sometimes consisting of high quantities of teratological Eunotia valves. Recent dramatic water quality improvements, following first reductions in and then cessation of emissions, were accompanied by decreases in the relative abundance of benthic acid- and metal-tolerant species in the sediment record. However, diatom recovery trajectories did not entirely progress towards predisturbance communities, as the contemporaneous increase in relative abundance of other species was restricted to a few groups. Moreover, diatom responses were not synchronous among cores, with recovery rates influenced by local bedrock and the hydrological regime of each lake.

Correcting the gas and particle partitioning of PCDD/F congeners in the flue gas of an iron ore sinter plant

This study was aimed at developing an approach for correcting the gas and particle partitioning of PCDD/F congeners for samples collected from the flue gas of an iron ore sinter plant. An iron ore sinter plant equipped with an electrostatic precipitator (EP) and a selective catalytic reduction (SCR) was selected. Flue gas samples were collected at EP inlet, EP outlet and SCR outlet. Both particle- and gas-phase PCDD/Fs were analyzed for each collected sample. PCDD/F contents in EP ashes (EPash) were also analyzed and used to correct the gas and particle partitioning of PCDD/F congeners of the collected flue gas samples. Results show that PCDD/Fs in the flue gas were dominated by the gas-phase. Before correction, the removal efficiencies for the gas- and particle-phase PCDD/Fs for EP were −58.1% and 64.3%, respectively, and SCR were 39.4% and 83.9%, respectively. The above results were conflict with the expected results for both EP and SCR indicating the need for correcting the gas and particle partitioning of PCDD/F congeners for all collected flue gas samples. After correction, the removal efficiencies become more reasonable for EP (=4.22% and 97.7%, respectively), and SCR (=54.7% and 62.0%, respectively). The above results confirm the effectiveness of the approach developed by this study.

Assessment of Exposure to PCDD/F, PCB, and PAH at a Basic Oxygen Steelmaking (BOS) and an Iron Ore Sintering Plant in the UK

An assessment was carried out at a UK integrated steelworks to investigate the exposure of workers via inhalation to dioxins [polychlorinated dibenzo-p-dioxins (PCDD/F)], polychlorinated biphenyls (PCBs), and polycyclic aromatic hydrocarbons (PAH) including benzo[a]pyrene (B[a]P). Investigations focused on a basic oxygen steelmaking (BOS) plant and an iron ore sintering plant. The highest concentrations of PCDD/F and dioxin-like PCB were found at the BOS vessels and sinter strand area at the BOS and sinter plant, respectively. A risk assessment was carried out by comparing the daily intake of PCDD/F and PCB via inhalation with the recommended tolerable daily intake (TDI) proposed by the World Health Organisation (WHO). For the most exposed category of worker in this study (i.e. sinter plant workers inside the strand area), the estimated daily intake via inhalation was estimated to be 0.25 pg WHO-toxic equivalent concentrations (TEQ) kg(-1) body weight (bw). Considering that the average UK adult exposure to PCDD/F from the diet is 1.8 pg WHO-TEQ kg(-1) bw day(-1), the results indicated that the estimated daily intake of PCDD/F and PCB via inhalation for sinter plant workers would not result in the recommended range of the TDI (1-4 pg WHO-TEQ kg(-1) bw day(-1)) being exceeded. Cancer risks for a 40-year occupational exposure period were determined by multiplying the estimated intake by the inhalation cancer potency factor for 2,3,7,8-tetrachlorodibenzo-p-dioxin. For the most exposed category of worker, cancer risks from exposure to PCDD/F and PCB ranged from 2.5 × 10(-6) to 5.2 × 10(-5). Under most regulatory programmes, excess cancer risks between 1.0 × 10(-6) and 1.0 × 10(-4) indicate an acceptable range of cancer risk, suggesting a limited risk from PCDD/F and PCB exposure for workers in the sinter plant. With regard to PAH, B[a]P concentrations were typically <10 ng m(-3) at all locations at both the sinter plant and the BOS plant. In several cases, particularly at the sinter plant, B[a]P concentrations were well below or only marginally above the target value of 1 ng m(-3) specified in ambient air by the European Commission in the fourth 'Daughter' Directive of the Air Quality Framework Directive suggesting a very low risk of exposure for workers. For PAH, excess cancer risks ranged from 2.4 × 10(-6) to 7.3 × 10(-6) for BOS plant workers and from for 5.3 × 10(-7) to 1.5 × 10(-5) for sinter plant workers, well within the acceptable range proposed by the US EPA.

Improved distribution of fuel particles in iron ore sintering process

One of the recent areas of progress for better energy utilisation in iron ore sintering process is the distribution pattern of the fuel inside a macroparticle, which is formed with fine particles of iron ore, coke and limestone. Operational parameters for large scale industrial facilities, such as iron ore sintering plant, are commonly selected through a series of elaborate tests. The results of field experience in process improvement are introduced, and a theoretical modelling study is proposed to supplement the experimental based approach with fundamental physics based arguments, which enables predictive computation beyond the limited region of tests and adjustment. A single fuel particle model and a one-dimensional bed combustion model of solid particles are utilised, and the thermal process of combustion and heat transfer is found to be a dominant consideration in the discussions of productivity in the sintering process.

Solutions for containing dioxin emissions from iron ore sintering at Italian plant

The paper presents the results of a recent test campaign at an existing iron ore sintering plant in order to evaluate solutions to limit releases to air of dioxins. The solutions included primary containment measures (process integrated measures aimed at limiting the formation of pollutants) and secondary containment measures (end‐of‐pipe measures aimed at removing the pollutants produced), and the measurement campaign was planned to determine the operating conditions capable of complying with the legislation in force. The main aspects of the campaign are reported and the running conditions tested are defined. The results confirmed the need to integrate both types of containment measures in order to achieve the aims of the study.

NaCIO2(s)와 탄소 분산형 촉매를 이용한 저온에서의 NOx및 SO2동시 제거

NO oxidation is an important prerequisite step to assist the selective catalytic reduction (SCR) at low temperatures (). Therefore, we conducted the lab- and bench-scales experiments appling the sodium chlorite powder () for the oxidation of NO to and the carbon-based catalyst for the reduction of and ; the lab- and bench-scales experiments were conducted in laboratory and iron-ore sintering plant, respectively. In the lab-scale experiment, known concentrations of (200 ppm), (75 ppm), (10%) and (400 ppm) in 2.6 L/min were introduced into a packed-bed reactor containing , then gases produced by the reaction with were fed into the carbon-based catalyst (space velocity