Sinter Quality Research Articles

Intensive reduction of fuel consumption in the sintering process of double-layered fuel segregation with return fines embedding

Fuel combustion provides the essential energy required for the iron ore sintering process, this process results in tremendous carbon dioxide emissions. Therefore, it is vital to develop innovative strategies to reduce fossil fuel consumption by effectively utilizing the heat storage effect in packed beds. Herein, an innovative double-layered fuel segregation method with return fines embedded in the lower layer was proposed and validated, and a goal of intensively reducing fuel consumption by 16% was achieved. Specifically, the oxygen concentration in the flue gas decreased from 16.7% to 11.5%, whereas the carbon dioxide and carbon monoxide concentrations increased from 5.5% and 0.3% to 13.4% and 1.3%, respectively. Moreover, the tumbler and shatter indices increased by 1.7% and 3.2%, respectively, indicating an increase in the sinter quality. In addition to optimizing the parameters of the proposed technology, the mechanisms for intensifying fuel combustion by applying the proposed technology were elucidated. The narrow thicknesses of the combustion and over-wet zones were found to significantly contribute to the improved permeability of the sintering bed.

Effects of Recycling By-Products as Calcium Ferrites Added to the Sinter Mix on Sinter Quality and Emission of CO2, NO, and SO2

Effects of Recycling By-Products as Calcium Ferrites Added to the Sinter Mix on Sinter Quality and Emission of CO2, NO, and SO2

Effect of Al2O3 on Sintering Reaction of Calcium Ferrite

Calcium ferrite containing aluminum (CFA) has been widely used in blast furnace production because it is an important compound that affects the quality of sinter. The influence of Al2O3 on CFA preparation process was studied by the raw material of CaO-Fe2O3-Al2O3. Diffraction of x-rays (XRD), scanning electron microscope (SEM) and electrochemical impedance spectroscopy (EIS) analysis were used to analyze the phase, micro morphology and the reducibility of the products. The results showed that CaO tended to combine more with Fe2O3 to form calcium ferrite with the increase of Fe2O3, whereas CaO tended to combine more with Al2O3 to form calcium aluminate with the content of Al2O3 above 45%. The micro morphology of sintered samples had a stable sintering skeleton structure due to the existence of calcium ferrite. Calcium ferrite was distributed between different particles in flakes, whereas calcium aluminate was attached to the Al2O3 particle surface. The large amount of calcium aluminate inhibited the emergence of calcium ferrite, and it had an adverse impact on the reducibility of sinter and the preparation of CFA.

New understanding on formation mechanism of CaFe2O4 in Fe2O3 -Fe3O4-CaO-SiO2 system during sintering Process: Phase transformation and morphologies evolution

The complex calcium ferrite is the main binder phase of high basicity, high iron and low silicon sinter used in blast furnace (BF), and its formation amount and structure are important factors affecting sinter quality. This work research on the phase transformation and morphologies evolution of Fe2O3 -Fe3O4-CaO-SiO2 systems roasted 900 °C − 1200 °C in air atmosphere to understand the formation process of calcium ferrite. In CaO-Fe3O4 system, the prolonged roasting time and higher temperature promotes that CaFe5O7, CaFe3O5, and Ca2Fe2O5 gradually transformed into the stable existence of CaFe2O4. In CaO-Fe3O4 system, the higher temperature promotes that the combination of Fe3O4 and CaO formed the stable CaFe3O5 with orthorhombic structure. The replacement reaction between the newly formed CaFe3O5 phase and the unreacted CaO phase occur to form Ca2Fe2O5. In CaO-Fe3O4-SiO2 system, FeSiO3 can be combined with Fe3O4 to form Fe2SiO4 and Fe2O3. Under the action of high temperature, FeSiO3 and CaO undergo displacement reaction to form the unstable CaSiO3, the new formation of CaSiO3 can be easily combined with CaO to form the stable Ca2SiO4. With the further increase of temperature, the complex calcium ferrite is formed in calcium silicate layer. The final product complex calcium ferrite and calcium silicate exist at the same time. The formation of calcium silicate has an unfavorable effect on formation of complex calcium ferrite in the sintering process.

Preparation and properties of 0.79ZnAl2O4-0.21TiO2 microwave dielectric ceramics via digital light processing

0.79ZnAl 2 O 4 -0.21TiO 2 microwave dielectric ceramics are ideal materials for preparing 5 G lens antennas. However, conventional processing methods are difficult to meet the requirements of microwave devices for high precision and designed complicated structures. Additive manufacturing technologies provide opportunities for the fabrication of these devices. Herein, we fabricated 0.79ZnAl 2 O 4 -0.21TiO 2 ceramics by digital light processing (DLP). The slurry with 2 wt% dispersant content showed favorable dispersion effect and stability. The optimal penetration depth of 44.64 µm and critical energy dose of 3.04 mJ/cm 2 were obtained. After sintering , the 0.79ZnAl 2 O 4 -0.21TiO 2 ceramic only kept ZnAl 2 O 4 phase and TiO 2 phase. The relative density could reach 95.29%, which is comparable to that of dry-pressed sample. With the increase of sintering temperature , dielectric constant ( ε r ) and quality factor ( Q×f ) of 0.79ZnAl 2 O 4 -0.21TiO 2 ceramic increased first and then decreased. The sintered ceramic at 1550 °C exhibited excellent microwave dielectric properties ( ε r = 11.55, Q×f = 62,266 GHz, τ f = −0.64 ppm/°C). The results indicate that DLP is a promising technology to fabricate high-performance microwave dielectric ceramics with complex structures. • High-performance 0.79ZnAl 2 O 4 -0.21TiO 2 ceramics were fabricated by DLP technology. • The sintered ceramic only kept ZnAl 2 O 4 spinel phase and TiO 2 rutile phase. • The relative density (95.29%) could be comparable to that of dry-pressed sample. • The ceramic showed excellent microwave dielectric property ( ε r = 11.55, Q×f = 62,266 GHz).

Effects of protective materials on the sintering properties of Zn4Sb3

ABSTRACT High brittleness materials such as ceramics and semiconductors are prone to fracture during cooling. Improving the sintering quality of such materials has been a problem explored by industry and scientific research. Here, the high brittleness semiconductor Zn4Sb3 was prepared by hot-press sintering. It was found that adding protective aluminum sheets with a similar expansion coefficient of Zn4Sb3 can significantly improve the sintering success rate of Zn4Sb3. The density and compositional homogeneity of the Zn4Sb3 were also significantly improved by the addition. The finite element simulation found the greatest increase in density when the thickness ratio of the sintered sample to the aluminum sheet was 1:1. The increase in density is due to the reduced stress during the cooling process and more uniform stress distribution on the sample. The improvement in composition homogeneity is due to the higher thermal conductivity of the aluminum sheets, which results in a smaller temperature difference inside the sample. In addition, the protective effect of the aluminum sheets reduces the volatilization of Zn. Materials with similar melting points have similar thermal expansion coefficients. High-quality sintering of brittle materials will no longer be difficult as long as a suitable sample protection material is found.

Influence of Sinter Parameters on CO Emission in Iron Ore Sintering Process

Carbon monoxide is the major hazardous component in flue gas exhausting from the iron ore sintering. This study aims to reduce the CO emission by changing the sinter parameters by sintering pot tests; specifically, the sinter quality, CO concentration, and total emission in sintering flue gas were analyzed in detail. The sinter strength properties, including the shatter index and the tumble index, are analyzed by the sintering pot test and the sintering flue gas discussion. The results show that the CO emission can be suppressed by modifying the sinter parameters, such as carbon content, coke breeze and coal breeze ratio, water addition, and sintering negative pressure. The good sinter parameters with the lower CO emission are 2.8% carbon content and 7.5% water in the sintering mixture. A higher coke breeze to coal breeze ratio, or only coke breeze fuel in the sinter mixture, is beneficial for the lower CO emission with a negative fan pressure of −12 kPa.

Influence of biocoke on iron ore sintering performance and strength properties of sinter

Purpose. The research purpose is to substantiate the use of biocoke as a fuel in the iron ore sintering, as well as its influence on the performance and properties of the resulting sinter. To completely replace conventional coke breeze, biocoke is produced using 5 wt.% biomass wood pellets at different carbonization temperatures of 950 or 1100°C. Further, the influence of biocoke on the sintering process and the sinter quality is studied at a high proportion of biomass pellets of 10, 15, 30, 45 wt.% and a carbonization temperature of 950°C. Methods. Carbonization is performed in shaft-type electric furnaces to produce laboratory coke or biocoke. Afterward, the sintering of iron ores is conducted on a sinter plant. To assess the sintering process and the quality of the resulting sinter, the filtration rate is determined on a laboratory sinter plant using a vane anemometer designed to measure the directional flow average velocity under industrial conditions. The sinter reducibility is studied using a vertical heating furnace to assess the effect of coke and biocoke on the sinter’s physical-chemical properties. Findings. It has been determined that biocoke, carbonized at a temperature of 950°C, has good prospects and potential for a shift to a sustainable process of iron ore sintering. Originality. It has been proven that biocoke with a biomass pellet ratio of up to 15 wt.%, obtained at a temperature of 950°C, does not affect the parameters characterizing the sintering process. The sinter strength indicators correspond to the use of 100 wt.% conventional coke breeze. Biocoke used with a high proportion of biomass pellets of 30 and 45 wt.% causes a deterioration in the sinter quality. Practical implications. The results of using biocoke with the addition of 5-15 wt.% biomass pellets and at a temperature of 950°C are within the standard deviation, which makes it possible to use biocoke with 15 wt.% biomass pellets instead of industrial coke breeze.

Liquid Formation in Sinters and Its Correlation with Softening Behaviour

Modern blast furnaces with extensive operational volume demand better-quality iron agglomerates as feed for stable operation. Sinter is the principal feed used in blast furnaces across Asia. Liquid generated during the sintering process plays an essential role in the coalescence of the sinter blend and in sinter quality. Therefore, an estimation of liquid properties at peak bed conditions during sintering helps manage sintering liquid behaviour, leading to better control of final sinter properties. In this study, three different iron sinters were reheated to sinter bed conditions, followed by quenching. Electron probe X-ray microanalysis (EPMA) was used to identify the resultant phases and quantify their chemical compositions. The impact of sinter bulk compositions was analysed, especially on sintering liquid properties. Furthermore, experiments were conducted to study the softening and melting behaviour of the sinters, and the cohesive range of the sinters was identified. Finally, the effect of the sinter bulk compositions on sintering liquid properties and softening behaviour is detailed.

Forecasting of iron ore sintering quality index: A latent variable method with deep inner structure

Accurate and real-time estimation of iron ore sintering quality index is essential for the stability of the production process. However, the sintering process data is generally characterized by high dimensionality, collinearity, nonlinearity, and dynamic features, which seriously hinder the modeling performance. To cope with the complex properties mentioned above, an effective fusion of recurrent neural network with the gated recurrent unit and partial least squares (GRU-PLS) is introduced for ferrous oxide (FeO) prediction of the finished sinter. The proposed GRU-PLS model takes the advantage of conventional latent variable method but incorporates the deep inner structure between each pair of latent variables that captures the nonlinear and dynamic information simultaneously. The modeling performance of the proposed model is evaluated by the actual data collected from the iron ore sintering process in a large iron and steel group in South China. The results show the lowest prediction error of the GRU-PLS model in comparison with other counterparts. More specifically, the rootmean-square error of the GRU-PLS model is decreased by 35.29% in comparison with that for the recurrent neural network with the gated recurrent unit.

Study on Influencing Factors of High-Temperature Basic Characteristics of Iron Ore Powder and Optimization of Ore Blending.

In order to explore the reasonable ore blending of low-silicon magnetite in sintering, it I necessary to realize the efficient utilization of low-silicon ore, further reduce cost, and increase yield. In this study, based on the high-temperature basic characteristics of iron ore powder used in the experiment, sinter pot tests were carried out with different low-silicon ore ratios, and the microstructure of the sinter was observed by scanning electron microscopy (SEM) and energy spectrum analysis (EDS) to determine the optimal matching law of low-silicon ore. The result showed that SiO2, Al2O3, and burning loss in iron ore powder composition were positively correlated with its assimilation, whereas MgO and basicity R2 were negatively correlated with the assimilation of iron ore powder. When the ratio of low-silicon ore was not more than 35%, increasing the ratio of hematite improved the liquid production and increased the production of acicular calcium ferrite. Therefore, the optimization of ore blending based on assimilation can improve the quality of sinter and strengthen the sintering process. This study has certain reference significance for the industrial production of low-silica sintering.

Mechanical properties and degradation of laser sintered structures of PLA microspheres obtained by dual beam laser sintering method

This paper discusses the influence of process parameters on the degradation and the mechanical properties of laser-sintered polylactide (PLA) microspheres obtained using the novel dual beam laser sintering method (DBLS). DBLS is a technique developed by our team that is a modification of standard polymer laser sintering (pLS), with the potential to reduce polymer degradation during the process. The PLA microspheres were produced using the standard emulsion-solvent evaporation method. The laser sintering process was carried out in a wide range of process parameters to obtain samples with various degrees of sintering. Next a number of tests were conducted to assess the physicochemical properties of these samples, including visualization techniques (SEM, digital microscopy and photography), gel permeation chromatogrphy (GPC), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), dynamic mechanical thermal analysis (DMTA) and static compression tests. The work shows that for different sets of process parameters, it is possible to obtain a product with similar mechanical properties, but at the same time with a completely different degree of polymer degradation. Hence, the hypothesis that when assessing the sinter quality one should take into account not only the mechanical properties of the detail, but also the degree of polymer degradation, which is of great importance, for example, in biomedical applications. It has also been shown that the DBLS method has a potential to reduce the degree of degradation of the sintered polymers and the post-process material outside the sintering zone.

Additive Enhances Iron Ore Reducibility and Pig Iron Productivity

The reducibility of iron ore with coke is an important parameter in a blast furnace process which significantly affects the production of pig iron. When iron ore and coke mixed with developed high energetic additive in blast furnace it promotes low temperature iron ore reduction and leads to coke saving. Results of proximate analysis values for moisture, ash, volatile matter and fixed carbon content were 15.28%, 16.62%, 1.02% 67.07% and 14.15%, 15.29%, 0.48% and 70.07% respectively with and without additive. Additive increased metallization of iron (Fe) content from 48.61% to 51.89% and decreased the ferrous oxide (FeO) from 12.26% to 9.28%. Additive reduced the CaO, SiO 2 , Al 2 O 3 and MgO by 10.90%, 8.31%, 2.79%, and 1.47% respectively which showed improvement of quality of sinter and further reduction of the pig iron sulphur content from 0.22 to 0.08% which reflected improvement in metal product quality. Additive increased the slag chemical composition of CaO, SiO 2 , MgO, Al 2 O 3 and MnO by 4.79%, 2.62%, 7.35%, 2.82 % and 19.56% respectively and decreased the FeO by 32.23%. Additive reduced the consumption of coke by 700 kg and increased production by 2% resulting saving of coke by 91 kg per ton of pig iron production. Additive increased reducibility, quality and productivity of pig iron with decrease in batch maturing period. Further it exhibited better performance in sintering process and reduced the un-agglomerated material. This paper describes the effect of additive used in the blast furnace process during industrial pig iron production.

Prediction of Air Leakage Rate of Sintering Furnace Based on BP Neural Network Optimized by PSO

Aiming at the difficulty of air leakage detection in the sintering process of the sintering furnace, especially the problems of high detection cost and poor timeliness of detection results when traditional methods are used for detection, we propose an air leakage rate prediction algorithm. Firstly, we use the particle swarm optimization algorithm to optimize the initial parameters of the neural network based on back propagation and get the best set of initial parameters through continuous search. Secondly, the optimized parameters are substituted into the neural network to train them with training data, and the trained parameters are obtained. Finally, the air leakage rate of the test set data is predicted by using the trained parameters. Compared with traditional calculation methods such as gas analysis and calorimetry, the proposed method can greatly simplify the detection process, shorten the detection time, and control the error within 5%, allowing the user to deal with the air leakage problem more timely and improve the overall sintering quality.

Efficient double-layer sintering of titanomagnetite concentrate

The traditional titanomagnetite sintering process consumes high fuel and produces weak-strength sinter. In this study, double-layer sintering was used to solve above problems. The theoretical analysis and sintering pot test results showed that sintering of feed bed constituted by two different-basicity layers could improve mineralization and permeability. By using the double layer structure of sintering bed and controlling the basicities of lower and upper layer (2.5 and 1.5, respectively), the yield, productivity, and reduction disintegration index (RDI+3.15) were 67.32%, 1.65 t m2 h−1, 49.68% respectively, which were improved 33.12%, 1.74%, and 9.27%, respectively than those obtained by the traditional sintering process. Meanwhile, 1.69 kg t−1 of solid fuel consumption and nearly 10% of electricity and gas consumption for sintering were saved. It was demonstrated that using different basicities for upper and lower layer of sintering bed would promote formation of silica-ferrite of calcium and aluminum (SFCA) with simultaneous reduction of perovskite, improving the sinter quality.

Numerical simulation of iron ore sintering process with coke oven gas injection and oxygen enrichment

Abstract Oxygen enrichment is believed to improve productivity and reduce fuel consumption, while gas fuel injection is assumed to improve the product yield and quality in iron ore sintering process. It is important to understand the mutual effect of oxygen enrichment and gas fuel injection for combined usage of these two techniques. A mathematical model is developed to simulate the sintering process with coke oven gas (COG) injection and oxygen enrichment, particularly focusing on predicting the quality and yield of sinter production, as well as NO x emission. The model is validated by comparing the model predictions with sintering pot test data, and numerical simulations are carried out to investigate the mutual effect of oxygen enrichment and COG injection. The results show that, compared with the conventional sintering process, with 0.5% COG injection and 30% oxygen enrichment, the mean melt quantity index (MQI) is increased by 4.1% and the mean cooling rate (CR) is decreased by 62.5%, showing that the sinter quality is improved significantly. The sinter yield is increased by 44.5%, whereas the NO x emission is increased by 8.3%. With the increase of oxygen enrichment from 21% to 30%, the sinter yield increases prominently first and then decreases a little, attaining its maximum at 30% of oxygen concentration. In addition, increasing oxygen concentration will increase the conversion rate of coke-N to NO x . Therefore, excessive oxygen enrichment is not only bad for sinter strength and yield, but also increases NO x emission.

A Model Study on Raw Material Chemical Composition to Predict Sinter Quality Based on GA-RNN.

The quality control process for sintered ore is cumbersome and time- and money-consuming. When the assay results come out and the ratios are found to be faulty, the ratios cannot be changed in time, which will produce sintered ore of substandard quality, resulting in a waste of resources and environmental pollution. For the problem of lagging sinter detection results, Long Short-Term Memory and Genetic Algorithm-Recurrent Neural Networks prediction algorithms were used for comparative analysis, and the article used GA-RNN quality prediction model for prediction. Through correlation analysis, the chemical composition of the sintered raw material was determined as the input parameter and the physical and metallurgical properties of the sintered ore were determined as the output parameters, thus successfully establishing a GA-RNN-based sinter quality prediction model. Based on 150 sets of original data, 105 sets of data were selected as the training sample set and 45 sets of data were selected as the test sample set. The results obtained were compared to the real value with an average prediction error of 1.24% for the drum index, 0.92% for the low-temperature reduction chalking index (RDI), 0.95% for the reduction index (RI), 0.40% for the load softening temperature T10%, and 0.43% for the load softening temperature T40%, with all within the running time thresholds. The study of this model enables the prediction of the quality of sintered ore prior to sintering, thus improving the yield of sintered ore, increasing corporate efficiency, saving energy, and reducing environmental pollution.

Investigation on the application of by-product steam in iron ore sintering: performance and function mechanism.

The combustion-supporting effect of steam to coke breeze in sintering has the potential to improve sinter quality and reduce pollutants emissions. The results show that increasing the by-product steam injection concentration (0.32-0.47vol%) and prolonging the injection time (5min) within a proper range (10-15min) can improve sinter quality. 2.13kgce/t-sinter of the fuel consumption was decreased by reducing coke breeze usage from 5.60 to 5.45% under the recommended parameters, with 15.16% decrease of CO in sintering waste gas. By comparing experimental data with thermodynamic calculations, although the reaction between CO and steam can reduce CO emission and generate H2, steam tends to react with coke breeze to generate H2 and CO (react at 674℃), and OH radical produced by H2 which can reduce the activation energy of CO oxidation reaction is the key to reducing pollutant emissions. The potential economic benefit of steam injection technology was calculated based on a 360m2 sintering machine (the annual sinter output is 3.2million tons), excluding the equipment modification and steam injection cost of $300,000; a profit of $737491.2 per year or 0.23 dollars per ton sinter can be achieved. Therefore, low-carbon and cleaner iron ore sintering production can be realized through applying by-product steam.

Laser sintering of Al2O3‐based green ceramics prepared by different pre‐sintering temperatures

AbstractAl2O3‐based green ceramics are prepared by isostatic cold pressing technology. The prepared green ceramics are pre‐sintered at the temperature from room temperature to 1100°C, and then Al2O3 ceramics are prepared by laser sintering. The effects of pre‐sintering temperatures and laser parameters on mechanical properties and the sintering quality are analyzed. The results show that good crystallinity of Al2O3 particles is obtained at a higher pre‐sintering temperature. The flexural strength and density of green ceramics increase with the temperature of heat treatment. The flexural strength decreases slightly at ∼200°C due to the paraffin binder disintegration. The pre‐sintering temperature and laser processing parameters have a significant influence on the sintering quality. With the increase of laser power and laser frequency, dynamic grain growth occurs, and then grains are refined. The majority of plate‐like grains are transformed into long cylindrical‐like grains in the severe densification process. However, porous flocculation microstructures are generated on the samples pre‐sintered at 1100°C after laser sintering, which is due to the material gasification in atmospheric environment during sintering by infrared laser. More uniform microstructure and better sintering quality of samples pre‐sintered at 500°C can be achieved after laser sintering with a relatively narrower grain size distribution.

Simulation model for the selection of technological parameters to obtain a sinter with high consumer properties based on the committee method

To control the quality characteristics of the agglomerate, a simulation model based on the committee method has been proposed. A generalized model of committee structures is presented in the form of a linear programming problem with partially integer variables. The model has been tested on real data. The minimum number of informative features is determined, in the space of which it is possible to construct a decision rule that separates agglomerate areas with high consumer characteristics from areas with satisfactory quality indicators. A high-quality agglomerate had to simultaneously meet the specified limits in terms of yield and strength. As a result of the calculations, a decision rule was built in the form of a seniority committee of five members in the space of 43 features. Geometrically, this is a convex region obtained from a hyperparallelepiped when it is truncated by five hyperplanes. This decision rule can be easily programmed with simple tools and integrated into the sinter quality control system. The practical importance lies in reducing the yield of structural fines during the destruction of the sinter cake, i.e., increasing the yield of a suitable agglomerate while keeping the technological parameters within the convex region.Contributors to the preparation of the article: A. A. Eliseev, Raw Material Research Manager of PJSC Severstal, aaeliseev@severstal.com, Yu. A. Malygin, Director of Ferrox Ltd., y.malygin@ferrox.org,N. P. Chernavin, Assistant of the Dept. of Big Data Analytics and Video Analysis Methods of Ural Federal University, ch_k@mail.ru, F. P. Chernavin, Cand. Econ., Associate Professor of the Dept. of Controlled Systems Modeling of Ural Federal University, chernavin_fedor@mail.ru.