Sinter Pot Tests Research Articles

Mathematical modeling of and parametric studies on flue gas recirculation iron ore sintering

A relatively more comprehensive 1D mathematical model, compared to previous models, is proposed for flue gas recirculation sintering (FGRS). The proposed model considers multiphase theory, eight major reactions significantly affected by the input gas conditions, and various heat transfer processes within/between different solid and gas phases. Characteristic size distributions of materials including coke, limestone and dolomite are used to correct the reaction rates of key sub-models, as well as specific kinetic parameters determined via thermogravimetric analysis instead of empirical values. Geometric changes caused by the reactive and melting factors are described in improved manners. This model is validated by contrasting the modeling results and the measured data from sinter pot tests. Parametric studies show FGRS technology can significantly enhance combustion characteristic within sinter bed, meaning to increase maximum temperature and melt fraction, improve the uneven distribution of heat. Therefore, the quality of sintered ore can be improved. However, the slightly reduced flame front speed deserves further attention. The velocity of input flue gas exerts the most significant effect, followed by O2 concentration, and then, temperature. The operating parameters of FGRS must be carefully determined. Three measures, which still require further investigations, can be proposed to optimize the process.

Modeling NOx emission of coke combustion in iron ore sintering process and its experimental validation

NOx emission of coke combustion in iron ore sintering was modeled by overall reaction rate equations of NOx formation and reduction. Incorporating into a previous sintering heat treatment model, overall NOx emission can be predicted and the simulated results were well agreed with four sinter pot tests under varying conditions which are similar to actual production. In sintering, NOx emission is significantly related to fuel combustion. Due to heat input by ignition and smaller airflow in the initial stage of sintering, the predicted NOx emission has a higher value of about 350ppm first then it decreases a little and keeps at a relatively constant level of about 300ppm until the burn-through point, and decreases rapidly as a result of the accomplishment of coke combustion. Simulation results indicate that fuel NOx is the main NOx emission in sintering while thermal NOx is rarely produced since the bed temperature is much lower than 1800K. The generated NOx could be reduced not only on the surface and in the pores of coke but also by CO around coke particles, about 50% and 10% of the generated NOx could be reduced by char and CO, respectively. Increasing coke rate and decreasing coke size promote NOx generation by accelerating the coke combustion. The reduction extent by char is greatly influenced by contact between NOx and char while the reduction extent by CO is mainly determined by the combustion atmosphere.

Mathematical modeling and combustion characteristic evaluation of a flue gas recirculation iron ore sintering process

Flue gas recirculation sintering (FGRS) technology has been applied for two decades with the aim of reducing pollutant emissions. Compared with the conventional sintering (CS), the changes of input gas conditions may influence the bed combustion process greatly. Mathematical models have been developed to predict sintering behavior quantitatively, but few of the previous work focused on FGRS process. In this study, a multiphase theory-based mathematical model is established. This model considers nine kinds of major physicochemical reactions, in which six modes of gaseous reactions make it more comprehensive and accurate to model FGRS process. Heat transfer within/between different solid and gas phases are modeled in better manners. Geometric changes caused by reactive-factors are modeled in simple terms. Sub-models are available to simulate the effects of the temperature, gas supply, composition and content of recirculated gas on combustion characteristics in the sintering bed. Good agreements between simulated and measured results have been obtained from contrasting to six sinter pot tests based on FGRS technology. Four combustion parameters are selected to evaluate quantitatively the advantages and potential problems of FGRS technology. Results show that the flatter maximum temperature (MaxT) profile for FGRS compared with that for CS implies a stronger tumble strength of the sintered ore. The broader MaxT and combustion zone thickness (CZT) curve indicate a higher degree of melt fraction, together with a lower FFS and productivity. To better investigation, further parameter simulation and process optimization of FGRS technology is necessary.

Effects of carbon content on the sintering behavior of low-titanium vanadium-titanium magnetite

Low-titanium vanadium-titanium magnetite (LVT) sinter exhibits poor properties. Carbon content (ω (C)) can alter LVT sintering behavior as it affects the mineral phases in the LVT sinter by changing the sintering temperature and environment. In this work, the sintering behavior of LVT sinter mixture with varying ω (C)% of 2.8–4.4 was investigated by sintering pot test, x-ray diffraction (XRD), scanning electron microscopy (SEM) analyses, and a ternary phase diagram. The optimal ω (C)% was calculated. The results indicated that with increasing ω (C)%, the magnetite and perovskite increased and hematite decreased. The calcium ferrite and Calcium and Aluminum Silico-ferrite (SFCA) with good properties increased and then decreased and decomposed at a high ω (C)% value. The variation in the mineral content caused variation in the LVT sinter properties and the LVT sinter mineral structure required further optimization. For production, the ω (C)% should be maintained at 3.6 during LVT sintering under current conditions.

Effects of liquid infiltration characteristics of iron ores with a high proportion of limonite on sinter strength

Since the strength of unmelted nuclei ores and the bonding phase are constant under the same conditions of sintering parameters and ore-proportioning structure, sinter strength is largely determined by the bonding degree between unmelted nuclei ores and the bonding phase. The bonding degree is mainly dependent on the infiltration behavior of sintering liquid on nuclei ores. Infiltration tests were carried out using micro-sinter equipment in order to clarify the liquid infiltration characteristics of mixed ores with a high proportion of limonite. The effects of the infiltration area index of the original liquid (IAO), infiltration volume index of the secondary liquid (IVS) and sinter body bonding strength (SBS) on the tumbler index of the sinter (T ) are discussed using a laboratory sinter pot test. The results showed that T increased first and then decreased with an increasing IAO and IVS, but increased linearly with increasing SBS. In order to improve the sinter strength with a high proportion of limonite, the IAO and IVS should be controlled within 2.02–2.38 and 0.19–0.21, respectively. Meanwhile, sintering schemes with a high SBS should be chosen during ore-proportioning optimization.

Experimental Study on the Effect of Waste Gas Recovery on Iron Ore Sintering

The effects of different waste gas recovery sintering (WGRS) cases on iron ore sintering were determined through a sintering pot test and compared with conventional sintering (CS). Two key operational parameters were identified selectively, namely, the temperature and lean‐oxygen content of recycled gas. The chosen values of these parameters for the sintering pot test were close to those in industrial production conditions. The proportion of the sintering mixture was standardized by ensuring the generation of mass‐averaged particles with similar sizes. The changes in the sinter quality indices and in the process parameters under different WGRS cases were systematically analyzed to demonstrate the feasibility of replacing CS production with WGRS technology. The optimal temperature ranged from 200 °C to 250 °C, and the optimal oxygen content was 20%. Therefore, this work can guide the industrial application of WGRS in China considerably.

Evaluation of Sintering Behaviors of Saprolitic Nickeliferous Laterite Based on Quaternary Basicity

The sintering behaviors of saprolitic nickeliferous laterite with various quaternary basicities [(CaO + MgO)/(SiO2 + Al2O3) mass ratio] in a reductive atmosphere are investigated by simulative sintering and validated by sintering pot tests. The simulative sintering results show that the generation of diopside (CaMgSi2O6) with low melting point is the key reason for the decrease in characteristic fusion temperatures when the quaternary basicity increases from 0.5 to 0.8–1.0. Continuous increase of basicity leads to transformation of diopside (CaMgSi2O6) into akermanite (Ca2MgSi2O7), which adversely increases the characteristic fusion temperatures. These findings are confirmed by the sinter pot tests, which demonstrate that the sintering indexes including vertical sintering velocity (VSV), yield (Y), and productivity (P), can be improved by optimizing quaternary basicity. At basicity of 1.0, the VSV, Y, P, and ISO tumbling index reach 49.2 mm/min, 80.5%, 1.0 t/(h m2), and 66.5%, respectively.

Influencing factor of sinter body strength and its effects on iron ore sintering indexes

Sinter body strength, which reflects the strength of sinter, plays an important role in the improvement of sinter. In this study, the sinter body strengths of iron ores were measured using a microsintering method. The relationship between the chemical composition and sinter body strength was discussed. Moreover, sinter-pot tests were performed. The effects of sinter body strength on the sintering indexes were then elucidated, and the bottom limit of sinter body strength of blending ores was confirmed. In the results, the compressive strengths (CSs) of iron ores are observed to decrease with the increasing of the contents of loss on ignition (LOI), SiO2, and Al2O3; however, LOI of less than 3wt% does not substantially influence the CSs of fine ores. In the case of similar mineral composition, the porosity, in particular, the ratio between the number of large pores and the total number of pores, strongly influences the sinter body strength. With an increase of the blending-ore CSs used in sinter-pot tests, the yield, productivity, and tumbler strength increase, and the solid fuel consumption decreases. The CSs of the blending ores only slightly affect the sintering time. The CS bottom limit of the blending ores is 310 N. When the CSs of the blending ores increase by 10%, the yield, productivity, and tumbler index increase by 1.9%, 2.8%, and 2.0%, respectively, and the solid fuel consumption decreases by 1.9%.

Effect of basicity on sintering behavior of low-titanium vanadium–titanium magnetite

Basicity has an important effect on the sinter quality, especially for low-titanium vanadium–titanium sinter. The effect of basicity on sintering behavior of low-titanium vanadium–titanium mixture, and the transference and distribution of element in sintering process were researched by sinter pot test, mineralogical analysis, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) analysis. The results show that CaO preferentially reacts with TiO2, generating pervoskite, so that the total liquid phase content of the sinter is low. There is an increase in the perovskite concentration of the sinter with the basicity ranging from 1.9:1 to 2.7:1. With increasing the basicity, the calcium ferrite content increases slightly and then rises rapidly, while the silicate content decreases and the metallurgical property of the sinter is improved. As for the distribution of these elements in the sinter, Ti occurs mainly in perovskite, V occurs mainly in silicate, and Fe occurs mainly in magnetite and hematite. The most abundant occurrence of Ca and Si occurs in silicate and perovskite. With increasing the basicity, the contents of Al and Mg increase in calcium ferrite, while they decrease in other minerals.

Vanadium–titanium magnetite ore blend optimization for sinter strength based on iron ore basic sintering characteristics

Vanadium titanium magnetite (V–Ti) ore is one kind of important polymetallic minerals in China and the mainstream route of comprehensive utilization process is blast furnace (BF)→basic oxygen furnace (BOF). V–Ti sinter is one of the main burdens employed for BF and poor tumbler strength (TI) limits its efficiency. In order to optimize the V–Ti blends for sinter TI, the basic sintering characteristics (BSCs) of 5 kinds of V–Ti ores, 2 ordinary ores and 3 groups of optimization V–Ti blends were studied. In addition, the sinter pot tests were conducted to obtain the TI of the produced sinter. The influencing factors on assimilation temperature (AT), the relations between the 4 characteristics of BSCs, and the factors influencing the V–Ti sinter TI were analyzed. The results showed that the BSCs of 5 kinds of V–Ti ores DB, HW, YT, JL and FH were good except liquid phase fluidity characteristic index (LF). The key reason why V–Ti sinter had a poor TI was the low LF, which caused the sinter with a large-pore structure. Therefore, the matching ores for optimization V–Ti blends should have a high LF. In addition, self-strength of the bonding phase (BS) and crystal intensity (CI) had an important impact on TI when the melt formed was sufficient and meanwhile the melt had a high LF. Moreover, the proper AT was the prior factor for the melt generation. In addition, the optimization V–Ti blends had good BSCs. The sinter TI with 7% NF ore addition could meet the production requirements for its TI was higher than 65%. Totally, the method of V–Ti magnetite ore blend optimization for sinter strength based on iron ore basic sintering characteristics was useful.

Model of Iron Ore Sintering Based on Melt and Mineral Formation

A model of iron ore sintering was built with consideration of fuel combustion, catalysis of sinter mixture as well as formation of melt and mineral, which was verified via sintering pot tests and showed a good fit to the experimental results. The effect of bed depth on temperature was reflected by the residence time in high-temperature zone, rather than the top value of the temperature, which was weakened by melt formation as well as hematite decomposition. Moreover, the effect of bed depth, fuel content and distribution on sintering process was different, which was reflected by temperature profiles and the rule of calcium ferrite formation. The formation of melt as well as magnetite was a process which was decided by kinetic factors, while the formation of calcium ferrite was related to fuel blending conditions, which is determined by thermodynamics when the fuel ratio inside sinter granules is low or fuel content is high, otherwise, it is determined by kinetics.

Influence of Basicity on High-Chromium Vanadium-Titanium Magnetite Sinter Properties, Productivity, and Mineralogy

The effect of basicity on high-chromium vanadium-titanium magnetite (V-Ti-Cr) sintering was studied via sintering pot tests. The sinter rate, yield, and productivity were calculated before determining sinter strength (TI) and reduction degradation index (RDI). Furthermore, the effect of basicity on V-Ti-Cr sinter mineralogy was clarified using metallographic microscopy, x-ray diffraction, and scanning electron microscopy-energy-dispersive x-ray spectroscopy. The results indicate that increasing basicity quickly increases the sintering rate from 25.4 mm min−1 to 28.9 mm min−1, yield from 75.3% to 87.2%, TI from 55.4% to 64.8%, and productivity from 1.83 t (m2 h)−1 to 1.94 t (m2 h)−1 before experiencing a slight drop. The V-Ti-Cr sinter shows complex mineral composition, with main mineral phases such as magnetite, hematite, silicate (dicalcium silicate, Ca-Fe olivine, glass), calcium and aluminum silico-ferrite (SFCA/SFCAI) and perovskite. Perovskite is notable because it lowers the V-Ti sinter strength and RDI. The well intergrowths between magnetite and SFCA/SFCAI, and the decrease in perovskite and secondary skeletal hematite are the key for improving TI and RDI. Finally, a comprehensive index was calculated, and the optimal V-Ti-Cr sinter basicity also for industrial application was 2.55.

Influence of Coke Combustion on NOx Emission during Iron Ore Sintering

This paper explores NOx emission during iron ore sintering on a pilot-scale pot. A novel technique of using a three-layered bed structure was adopted to study the role of coke level, properties and combustion behavior on NOx emission. In addition, the lime content of the mix was also altered to understand the effect of the melt formation process. Thirteen sinter pot tests were employed to analyze the influence of coke combustion on NOx emission. As the flame front descended down the pot, NOx emission decreased because of increasing bed temperatures. For this reason, it is to be expected that increasing coke rate will result in higher sinter bed temperature and lower conversion of coke-N to NOx. However, overall NOx emission is little changed because more coke means higher N availability. Increasing basicity (CaO/SiO2) from 1.9 to 2.4 in raw mix results in the decrease of NOx emission, about 5%. Increasing coke size may result in the decrease or increase of NOx emission. Placing coke particles on the outside of granules can lower NOx emission in the middle and bottom layers, by 4–15%. NOx emission in the iron ore sinter process is determined by the conversion of coke-N to NOx and nitrogen source in sinter mix. The atmosphere around coke particles is very important for NOx reduction, and NOx emission will increase by around 15% when oxygen increases by 1 vol.%. During iron ore sintering, temperature has great influence on NOx emission, with levels decreasing by 15–25% for a 100 K temperature increase.

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.

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.

Ore blending ratio optimisation for sintering based on iron ore properties and cost

The iron ore blend for sintering depends to a great extent on ore properties. It is hard to determine the final sinter reducibility from the reducibility and ratio of single iron ores in a mixture. For production cost reduction, optimised blending ratios were designed according to ore prices and properties (microstructure, crystal water decomposition, assimilation ability, liquid phase fluidity), ensuring nearly identical chemical composition as the mixture used in actual sintering. Sinter pot tests were conducted to determine the optimum mix. The results indicate that properties of iron ores vary greatly, which should be considered for the design of ore blending ratio. The total content of the two Australian ores tested should not exceed 45%. The cost of sintering process could be further reduced together with an improvement of economic and technical indices, only by ratio adjustment of present ores.

Characteristics of the Sierra Leone High Alumina Iron Ore and Utilization in Sintering

The characteristics of the Sierra Leone iron ore were studied at laboratory scale by chemical analysis, XRD, SEM-EDS and TG-DSC methods. The Sierra Leone iron ore was a kind of limonite, which was mainly consisted of hematite, goethite and gibbsite. The iron ore lost its crystal water at a fast speed ranging from 200°C to 400°C and the total content of the crystal water was about 8.2 wt.%. The initial melt formation temperature of the iron ore with CaO was stably kept at around 1209°C and the amount of liquid increased with the increasing of CaO content. Its melt formation temperature is higher than Australian limonite. The sintering pot test showed that the yield of sinter decreases from 78.37wt.% to 73.36wt.% and the drum index decreases from 60.5wt.% to 49.63wt.% when the blending ratio of Sierra Leone iron ore increases from 7wt.% to 27.3wt.%.

Study of iron ore sinter when fine ore is replaced with coarse ore, using infrared furnace and sinter pot tests

The effect of replacing fine iron ore by coarse iron ore in the sinter mixture on sinter properties was studied using an infrared furnace and sinter pot tests. A two-level full factorial design was used for the identification of parameters that significantly influence the formation of sinter phases under laboratory conditions, using an infrared furnace. Coarse ore fraction was identified as the most significant parameter that influences sintering, and the formation of sinter phases. This study proved that sinter with high quality physical and metallurgical properties, as well as suitable production parameters, can be produced by adding coarse ore to the sinter mixture. Increased coarse ore fraction in the sinter mixture resulted in a decrease in the porosity of the sinter and accompanying reduction in reducibility. The amount of coarse ore that can therefore be added to the sinter mixture is determined by the required degree of reduction.

Influence of La<sub>2</sub>O<sub>3</sub> on NO<sub>x</sub> Emission in Iron Ore Sintering

NOx emission in coke combustion with and without La2O3 was investigated in a fixed bed quartz reactor. The effects of La2O3 loading and lanthanum oxide particle size on NOx emission were discussed. NOx emission was also studied by sintering pot tests with lanthanum oxide modified coke as sintering fuel. The results showed that lanthanum oxide was catalytically active in promoting not only coke combustion but also NOx reduction. In coke combustion experiments, NOx and CO emission decreased with increasing lanthanum oxide loading up to 2.0wt% and decreasing lanthanum oxide particle size (28~150μm).

Load reduction sintering for increasing productivity and decreasing fuel consumption

The technical and economical indexes and the physical properties of load reduction sintering processes with the supporting stands of installation at different height levels (300, 350, and 400 mm) in a sintering bed were studied under the same conditions of raw material, bed height, and sintering parameters. Sintering pot tests with different bed heights and fuel ratios of the mixture with or without supporting stands were performed to decrease the fuel consumption. The airflow rate through the sintering bed was measured with an anemoscope fixed on the bed surface to reveal the effects of supporting stands. The utilization of load reduction sintering can improve the permeability of the sintering bed, and the airflow rate through the sintering bed is increased. When the stand height is half of the sintering bed, the productivity increases by 27.9%, and the drum index slightly decreases. Keeping at the same productivity level with normal sintering, the utilization of load reduction sintering can decrease the solid fuel consumption by 9.2%.