Sinter Plant Research Articles

Continuous Measurement and Control of Sinter Mix Moisture for Decrease in Sintering Fluctuation

To decrease carbon dioxide emission in iron ore sintering process through reduction of carbon consumption as sintering agent, reduction of fluctuation in iron ore sintering was studied. Transition phenomena of the sintering fluctuation through a sintering plant were observed and studied using a frequency analysis.The sintering fluctuation was defined as the cyclic change in the exhaust gas temperatures at a certain wind-box. The observation of the wind box temperatures showed that the temperature changes of several minute cycles existed. To search for upstream causes, charging behavior of the sinter mix to pallet cars was observed using an index of “charging level”. Comparison of the charging level and the wind box temperature showed that the fluctuations of them were almost coincident in the occurring time and position. To search for further upstream causes, a near-infrared moisture meter was introduced to measure sinter mix moisture with high frequency. To investigate the relationship between the wind box temperature, the charging and the sinter mix moisture, a frequency analysis of the fluctuations of them was carried out. It showed that some frequency elements were almost coincident and that fluctuation transferred from the fluctuation in the sinter mix moisture to the sintering.Then, a test operation of more precise control of the sinter mix moisture using the near-infrared moisture meters in a sintering plant was carried out. It successfully reduced sintering fluctuation.

Reduction of Composite Pellet Containing Indonesia Lateritic Iron Ore as Raw Material for Producing TWDI

Blast furnace process is still an important process for producing pig iron. The process needs high grade iron ore and coke. The two materials can not be found easily. In addition blast furnace process needs cooking and sintering plant that produces polluted gases. Utilization of composite pellet for pig iron production can simplify process. The pellet is made of iron ore and coal. In addition the pellet can be made from other iron source and coal. This paper discusses the evolution of phase during reduction of composite pellet containing lateritic iron ore. Fresh iron ore and coal were ground to 140 mesh separately. They were mixed and pelletized. The quantity of coal added was varied from 0 %, 20 % and 29 % of pellet weight. Pellets were heated with 10 °C/minute to 1100 °C, 1200 °C, 1300 °C and 1350 °C in a tube furnace and temperature was held during 10 minutes. Heated pellets were analyzed with XRD equipment. XRD of reduced pellets showed that iron phase change with coal and temperature. Lack of coal during heating results the re-oxidation of iron phases. This process is due to replacement of reductive atmosphere by oxidative atmosphere.

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.

Non-linear State Estimator for the On-line Control of a Sinter Plant

This is a thermal control model that aims to increase sinter process stability and standardize control criteria using the position and temperature of the sintering point or BTP calculated by the model. The process computer sends to the instrumentation setpoints of return fines, strand speed and coke content. The model was successfully tested at the facilities of AM Asturias with contrasted improvements in productivity, cok consumption and quality stability.

Efficient and Clean Production Practice of Large-Scale Sintering Machine

Shougang Jingtang Iron and Steel plant has built the new generation sinter plant with two 500 m2 sintering machines at Caofeidian Port, the thought of Metallurgical Process Engineering was led into, and the ordering, coordinated, efficient, continuous production of sinter manufacturing processes were achieved. Whose overall design adopted advanced, proven process technology and large-scale equipments, which broke through long flow layout in traditional metallurgical projects and achieved short flow with compact arrangement. Widening side plate of sintering machine and annular cooler were used to create conditions for increasing production capacity, lowering energy consumption of unit production. According to the concept of recycling economy and energy saving, the high-temperature exhaust heat of annular cooler was recycled, the iron and carbon waste and waste water were dissolved, which gained sinter production energy conversion, by applying dense phase pneumatic dust conveying technology, the secondary pollution of dust was avoided, the concentration of SO2 emission was below 47 mg/Nm3 in the flue gas. Through adopting deep bed sintering, since producing in May 2009, the equipments ran smoothly with sintering bed depth reached 860 mm in sintering production, qualification rate of sinter ores reached 99.71%, drum index was 81.79%, and the energy consumption of process was 47.70 kgce/t, which attained first class domestically and internationally advanced level.

Role of Water Structure-Making/Breaking Ions in the Cationic Flotation of Kaolinite: Implications for Iron Ore Processing

Australia is the largest exporter of iron ore in the world. The high Al content in Australian hematite/goethite ores is detrimental to blast furnace and sinter plant operations. Of the Al containing minerals in iron ore, kaolinite is a common gangue mineral frequently found in iron ore deposits. In iron ore flotation pulp, various ions exist and may inter- fere with the flotation performance when their concentration is high enough. In this work, the role of a water struc- ture-making ion, i.e. Na + , and a water structure-breaking ion, i.e. K + , in the flotation of kaolinite under reverse cationic flo- tation conditions, the most widely used flotation route of iron ore in the world, was studied in a series of laboratory batch flotation tests. It was found that K + , a water structure breaker, can better reduce the zeta potential of kaolinite and thus causes higher flotation recovery of the clay mineral, in comparison to Na + , a water structure maker. The different effects of the alkali metal cations on kaolinite flotation are attributed to the different aggregation degree of kaolinite particles in the presence of these cations.

Energy intensity development of the German iron and steel industry between 1991 and 2007

The iron and steel sector is the largest industrial CO2 emitter and energy consumer in the world. Energy efficiency is key to reduce energy consumption and GHG emissions. To understand future developments of energy use in the steel sector, it is worthwhile to analyze energy efficiency developments over the past two decades. This paper analyses the development of the specific energy consumption (SEC) (measured as primary energy use per unit of product) in the German steel sector between 1991 and 2007. We found that the total SEC declined by 0.4%/year. Of this 75%, or 0.3%/year, is due to a structural change towards more electric arc furnaces (EAF). Energy efficiency improvement accounts for about 25% of the observed change in SEC, or 0.1%/year. Energy efficiency improvements are found, especially in rolling (1.4%/year). The net SEC of blast furnaces decreased due to increased top gas recovery by 0.2%/year per tonne iron. Improvements in other processes were very limited or non-existent. In basic oxygen furnaces (BOF) net SEC increased due to a 60% decrease in BOF gas recovery between 1993 and 2007. In EAF and sinter plants the SEC remained constant or, respectively, even increased by 9% between 1991 and 2007 per tonne sinter.

Microstructural Evaluation of Clayey Ceramic Incorporated with Powder Waste from the Sintering Plant of a Steel-Making Industry

Steel making in integrated plants involves several stages from the feeds tock preparation, by sintering or pelleting of the iron ore, to the rolling of the steel sheets. In any of these stages wastes are generated and unless recycled or used as by product, they will cause serious environmental problems. Therefore, this work has as its objective to evaluate the effect of incorporation of 20 wt.% of the powder waste, particulate material, retained in the eletrostatic precipitator equipment of the sintering stage from an integrated steel making plant on the microstructure a clayey ceramic fired at 1050°C. The microstructure of the fired ceramics was evaluated by scanning electron microscopy, X-ray diffraction and mercury porosimetry. The results showed that in the investigated temperature the waste increased the porosity of the clayey ceramic as well as introduced defects in the microstructure of the ceramic.

Scaled-chrysophyte assemblage changes in the sediment records of lakes recovering from marked acidification and metal contamination near Wawa, Ontario, Canada

A remarkable example of point-source lake acidification and metal pollution, and subsequent recovery in limnological variables, has occurred in lakes near the former iron sintering plant at Wawa (Ontario, Canada). Surface water pH levels in some of these lakes have increased from 3 to 7 following local sulphur emission reductions with closure of industrial operations. Previous paleolimnological work documented striking successional changes in diatom species assemblages within dated sediment cores that could be related to past industrial activities. To gain additional insights into the chemical and biological recovery trajectories of the Wawa lakes, we used paleolimnological techniques to track euplanktonic scaled-chrysophyte (classes Chrysophyceae and Synurophyceae) species assemblage responses to historical water quality changes in five lakes. Coincident with the period of iron sintering from 1939 to 1998, striking successional changes were noted in the sedimentary profiles, with marked increases in the relative abundances of the acid- and metal-tolerant taxon Synura echinulata. The scaled chrysophyte changes pre-dated diatom responses, confirming the former’s status as reliable early warning indicators of lake acidification. Following closure of the sintering plant, species-specific chrysophyte responses to decreased emissions varied amongst the study lakes, perhaps reflecting differences in local bedrock geology and hydrological regime. Although some water chemistry variables may have recovered to near pre-industrial levels, similar to the diatom study, our data show that chrysophyte assemblages in the most recent sediments are now significantly different from pre-industrial assemblages.

Scaled-chrysophyte assemblage changes in the sediment records of lakes recovering from marked acidification and metal contamination near Wawa, Ontario, Canada

A remarkable example of point-source lake acidification and metal pollution, and subsequent recovery in limnological variables, has occurred in lakes near the former iron sintering plant at Wawa (Ontario, Canada). Surface water pH levels in some of these lakes have increased from 3 to 7 following local sulphur emission reductions with closure of industrial operations. Previous paleolimnological work documented striking successional changes in diatom species assemblages within dated sediment cores that could be related to past industrial activities. To gain additional insights into the chemical and biological recovery trajectories of the Wawa lakes, we used paleolimnological techniques to track euplanktonic scaled-chrysophyte (classes Chrysophyceae and Synurophyceae) species assemblage responses to historical water quality changes in five lakes. Coincident with the period of iron sintering from 1939 to 1998, striking successional changes were noted in the sedimentary profiles, with marked increases in the relative abundances of the acid- and metal-tolerant taxon Synura echinulata . The scaled chrysophyte changes pre-dated diatom responses, confirming the former’s status as reliable early warning indicators of lake acidification. Following closure of the sintering plant, species-specific chrysophyte responses to decreased emissions varied amongst the study lakes, perhaps reflecting differences in local bedrock geology and hydrological regime. Although some water chemistry variables may have recovered to near pre-industrial levels, similar to the diatom study, our data show that chrysophyte assemblages in the most recent sediments are now significantly different from pre-industrial assemblages.

Concentration of organic micropollutants in the atmosphere of Trieste, Italy

PCDD/Fs, PCBs, and PAHs, ubiquitous environmental pollutants which are part of the POPs, are mainly produced by anthropogenic activities as well as by natural processes. Occurrences of these pollutants in different sites in Trieste are presented. PCDD/Fs distribution and their possible emission sources are discussed. Air samples were collected in different sites near the industrial area, in the city center, and in a background area, using a high-volume sampler equipped with a quartz fiber filter and a PUF. Each sampling lasted a week. The concentrations of the organochlorinated pollutants are consistent with literature data (ΣPCDD/Fs and Σdl-PCBs were 5-38 fg TEQ/Nm(3) and 4-31 fg TEQ/Nm(3), respectively), and an apparent seasonal trend was found with slightly higher concentrations in the winter and lower levels in both summer campaigns. Moreover, the isomer profile of each sampling campaign was compared to the fingerprint of a sintering plant, a cement plant, and an incinerator, the main industrial activities in Trieste. The organic micropollutants were detected in levels consistent with literature data. The results show that the pollutants are uniformally distributed in the atmosphere of Trieste. PCDD/F fingerprints in each site remained almost identical during summer and winter, confirming the yearly prevalence of the emissions from the nearby sintering plant.

Atmospheric emission of polychlorinated naphthalenes from iron ore sintering processes

Iron ore sintering processes constitute significant sources of dioxins, and studies have confirmed a close correlation between polychlorinated naphthalenes (PCNs) and dioxin formation. Thus, iron ore sintering processes are thought to be a potential source of PCNs, although intensive investigations on PCN emissions from sintering processes have not been carried out. Therefore, the aim of the present study was to qualify and quantify PCN emissions from nine sintering plants operating on different industrial scales. PCN concentrations ranged from 3 to 983ngm−3 (0.4–23.3pgTEQPCNm−3) and emission factors ranged from 14 to 1749μgt−1 (0.5–41.5ngTEQPCNt−1), with a geometric mean of 84μgt−1 (2.1ngTEQPCNt−1). The estimated annual emission of PCNs from sintering processes in China was 1390mg TEQPCN. These figures will assist in the development of a PCN emissions inventory. Regarding emission characteristics, PCNs mainly comprised low-chlorinated homologs. The ratios of several characteristic PCN congeners were also measured and compared with those from other sources. Taken together, these results may provide useful information for identifying the sources of PCNs produced by iron ore sintering processes.

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.

A pilot study for determining the optimal operation condition for simultaneously controlling the emissions of PCDD/Fs and PAHs from the iron ore sintering process

In this study, the cost-benefit analysis technique was developed and incorporated into the Taguchi experimental design to determine the optimal operation combination for the purpose of providing a technique solution for controlling both emissions of PCDD/Fs and PAHs, and increasing both the sinter productivity (SP) and sinter strength (SS) simultaneously. Four operating parameters, including the water content, suction pressure, bed height, and type of hearth layer, were selected and all experimental campaigns were conducted on a pilot-scale sinter pot to simulate various sintering operating conditions of a real-scale sinter plant. The resultant optimal combination could reduce the total carcinogenic emissions arising from both emissions of PCDD/Fs and PAHs by 49.8%, and increase the sinter benefit associated with the increase in both SP and SS by 10.1%, as in comparison with the operation condition currently used in the real plant. The ANOVA results indicate that the suction pressure was the most dominant parameter in determining the optimal operation combination. The above result was theoretically plausible since the higher suction pressure provided more oxygen contents leading to the decrease in both PCDD/F and PAH emissions. But it should be noted that the results obtained from the present study were based on pilot scale experiments, conducting confirmation tests in a real scale plant are still necessary in the future.

An Investigation on the Cracking of Pallet Side Walls at a Sinter Plant

A failure analysis on the cracking of pallet side walls of a sintering machine in an integrated steel plant is presented. The pallets moving at a constant speed carry the base mix for sintering and enter an ignition hood furnace (temperature ≈ 1150°C) at a regular interval of time. The pallet side walls of a sintering machine are therefore subjected to continuous thermal cycling. The material of the pallet side wall is spheroidal graphite (SG) cast iron. Ten cracked side walls are collected and analyzed. The failure investigation involves field visit, visual observation of the cracked side walls, fractography, chemical analysis, microstructural characterization, tensile and impact tests. Most of the cracks are observed between the bolt–hole locations of the lower side walls; bolt–hole locations act as obstructions to thermal movement of the casting. The chemical analysis shows higher level of sulfur while the materials must be of higher purity for SG iron. Fractography shows predominantly intergranular fracture. Examinations of microstructures at the cross sections of the samples show the presence of primarily intergranular cracks. Matrix structure reveals pearlite along with ferrite surrounding the embedded graphite nodules. The amount of pearlite in the matrix is measured around 30–35% whereas predominantly ferrite matrix is desirable at the elevated temperature application. Determinations of tensile and impact properties exhibit low values of elongation (10%) and impact energy (7 J), respectively, indicating poor toughness properties of the casting. The presence of pearlite and lower amount of graphite nodules deteriorate the thermal conductivity of the casting, thereby generating more thermal stress. The analyses show that the pallet side walls start cracking under cyclic high thermal stress due to embrittlement because of improper material.

Optimisation of FeO in iron ore sinter at JSW Steel Limited

Coke breeze is the most common fuel used in sintering, and its usage depends on the alumina content and fineness of the sinter mix. The coke breeze consumption in the JSW Steel Limited sinter plant was high compared to many other sinter plants in the world, and as there was a local shortage, optimisation in the sinter plants was necessary. FeO is an indicator of the thermal state of the sintering process and is employed as a quality control tool at many plants. Laboratory pot sinters were made, and the variation in FeO was affected by varying the amount of coke breeze in the green mix from 55 to 85 kg t−1 of sinter. The produced sinters were evaluated with respect to productivity, strength (tumbler index), reduction degradation index (RDI), reducibility and microstructural phases in the FeO range between 6·2 and 14·8%. It was found that the sinter with FeO range of 8·60–9·88% showed higher productivity and higher strength with desired RDI of ⩽27% and reducibility of >60%. Analysis of plant data has revealed that the sinter with FeO of 8·5–10·0% showed higher productivity, higher strength and lower RDI.

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.

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.

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.