Evaluation of the Air Leakage Flowrate in Sintering Processes

Iron ore sintering is a pre-treatment technology by which orefines are converted into porous and permeable sin-ters,which are the used in blast furnaces.This process can be adversely affected by air leakage phenomena of various types.As experimental measurements are relatively difficult and often scarcely reliable,here a theoretical model based on typicalfluid-dynamic concepts and relationships is elaborated.Through the analysis of two extreme cases,namely,those in which leakage is due to a small hole or a full rupture,a generalized hole-bed mod-el is introduced,which for thefirst time also includes a complete bed permeability equation and can deal with different leakage position conditions.The results show that the model can evaluate the influence of leakage on the system at one time and be used to calculate theflowrate and pressure drop.Notably,the obtained results are within a 15%deviation with respect to available experiment values,used for comparison.

Application of Intra-Particle Combustion Model for Iron Ore Sintering Bed

In order to quantitatively predict the behavior of the material in the packed bed, a single particle model is developed to describe the combustion and sintering process inside an individual particle composed of multiple solid material fines, including iron ore, coke and limestone, and is applied to the combustion modeling of an iron ore sintering. Byanalyzing three typical fuel distribution cases using the developed single particle combustion model, the effects of temperature and oxygen concentration gradient inside the particle on heat and mass transfer and the combustion behavior of the iron ore sintering process areinvestigated. Considering the various combustion rates which are highly dependent on the fuel distribution methods, correction factor for single particle model is also introduced and systematically analyzed. The aim of this research is to supplement particle technology to conventional approach and it is found that the oxygen concentration gradient inside the particle is significantly affected from the mixing method thereby changing the completion times of sintering process.

A comparison of the microstructure-dependent corrosion of dual-structured Mg-Li alloys fabricated by powder consolidation methods:Laser powder bed fusion vs pulse plasma sintering

In this study, powder metallurgy methods were used to fabricate Mg-7.5Li-3Al-Zn alloys from repowdered extruded alloys. Extruded alloys were powdered using ultrasonic atomization, and then laser powder bed fusion(LPBF) and pulse plasma sintering(PPS) were used to consolidate the bulk materials. A comparison of the properties of the fabricated alloys with those of a conventionally extruded one was carried out using methods that characterized the microstructure and corrosion resistance. When compared to their conventionally extruded counterpart, LPBF and PPS materials exhibited refined microstructures with low enrichment in Al Li and coarse Al, Zn, Mn precipitates. The main drawback of the LPBF alloy, printed for the needs of this study, was its porosity, which had a negative effect on its corrosion. The presence of unrecrystallized particle boundaries in the PPS alloy was also unbeneficial with regard to corrosion. The advantage of the LPBF and PPS processes was the ability to change the proportion of α(Mg) to β(Li), which when the complete consolidation of the material is achievable, may increase the corrosion resistance of dual-structured Mg-Li alloys. The results show that powder metallurgy routes have a wide potential to be used for the manufacture of Mg-Li based alloys.

Super-high bed sintering for iron ores:problems ascertainment

Super-high bed sintering process is an important development direction of iron ore sintering for its lower emission and higher yield.However,there is a lack of deep understanding of the uneven quality of super-high bed sintering products,and the deterioration of reduction disintegration performance,the thickening of hearth layer and the reduction in energy-saving effect are perplexing enterprises and researchers.To ascertain the problems of super-high bed sintering,ten sintering machines with the areas of 265,280,360,550 and 660 m^(2)and bed depth above 900 mm were sampled and analyzed.The results showed that problems were mainly shown in the unevenness of chemical composition,macrostructure,mechanical strength and metallurgical performance.The chemical composition exhibits severe segregation in both horizontal and vertical directions,with basicity segregation reaching as high as 0.81.The uneven macrostructure of sinter is reflected in a 10%difference in porosity and mechanical strength increase in 16%–19%along the vertical direction.The reducibility and reduction disintegration performance gradually deteriorate along the bed depth,with a difference of 10.5%in reducibility and 7.3%in RDI−0.5 mm(reduction disintegration index of sinter with size smaller than 0.5 mm).

Super-high bed sintering for iron ores:behaviors,causes and solutions of horizontal segregation on strand

Horizontal segregation has been a constraint to the development and application of super-high bed sintering.To eliminate the horizontal segregation of super-high bed sintering,several typical sintering machines were sampled and analyzed,and theoretical calculation was made to compare the bed depth and their differences in different areas within the mixture bin.Then,solutions were proposed and applied to a 265 m^(2) sintering machine.The results showed that the horizontal seg-regation of the 265 m^(2) sintering machine was dominated by particles larger than 8 mm with horizontal segregation degree of 0.48,while 360 and 550 m^(2) sintering machines were affected by 5-8 mm and 1-3 mm particles with horizontal segregation degree of 0.27 and 0.31,respectively.Causes analysis indicated the different segregation distribution results from the matching of the bed depth of each area within the mixture bin.Finally,the horizontal segregation degree not larger than 0.06 was achieved by optimizing the time parameters and the division of three zones on the 265 m^(2) sintering machine.

Advances in selective laser sintering of polymers

Polymers are widely used materials in aerospace,automotive,construction,medical devices and pharmaceuticals.Polymers are being promoted rapidly due to their ease of manufacturing and improved material properties.Research on polymer processing technology should be paid more attention to due to the increasing demand for polymer applications.Selective laser sintering(SLS)uses a laser to sinter powdered materials(typical polyamide),and it is one of the critical additive manufacturing(AM)techniques of polymer.It irradiates the laser beam on the defined areas by a computer-aided design three-dimensional(3D)model to bind the material together to create a designed 3D solid structure.SLS has many advantages,such as no support structures and excellent mechanical properties resembling injection moulded parts compared with other AM methods.However,the ability of SLS to process polymers is still affected by some defects,such as the porous structure and limited available types of SLS polymers.Therefore,this article reviews the current state-of-the-art SLS of polymers,including the fundamental principles in this technique,the SLS developments of typical polymers,and the essential process parameters in SLS.Furthermore,the applications of SLS are focused,and the conclusions and perspectives are discussed.

Study on an Integrated Sintered Metal Screen Moving Granular Bed Filter

A new gas clean-up process called 'integrated sintered metal screen moving granular bed' (ISMSMGB) for the integrated gasification combined cycle (IGCC) and pressured fluidized bed combustion (PFBC) was developed on the basis of a sintered metal candle filter and a cross-flow moving granular bed filter. This is a combination of the surface and deep bed filtering processes. A set of facilities was established and a series of cold model tests were carried out. The dust removal efficiency and the pressure drop of the filter were measured and analyzed. The results show that this process features the advantages of the moving bed for high capacity as well as high inlet dust load and the surface filter for high efficiency. Meanwhile, the granules moving downward cleans the cake on the screen surface, so that the system is operated at steady state.

Research on optimizing ore matching technology for 550 m^2 sintering machine

The sinter quality is important for its performance in a blast furnace,and optimizing ore matching is a main way to ensure the quality and yield of sinter ore and to reduce the cost of ore matching.The research on optimizing ore matching for a 550 m2sintering machine in Shougang Jingtang was carried out in this paper. Firstly,based on the condition of iron ore resourse in Shougang,sintering properties of various ores,especially the high temperature properties were researched,and basic structure of ore matching was determined according to the mutual complementary properties of assimilation and liquid phase fluidity among Australia ore,Brazilian ore and domestic concentrates,that was Australian ore(50%-60%) + Brazilian ore(40%-30%) + domestic concentrates(about 10%).Secondly,9 groups of ore matching schemes were designed and sintering pot tests were carried out,and then the starting scheme of the 550 m2sintering machine was obtained:ore from southern Brazil (20%) +ore from northern Brazil(10%) + semi-limonite(20%) + limonite ore(35%) + domestic concentrates (15%).Thirdly,experiment of optimizing parameters of optimizing basicity,lime ratio,water addition and bed depth were carried out,and 9 groups of ore matching schemes were designed.The results showed that parameters fit for Jingtang currently are as follows:binary basicity is 1.9 - 1.95,lime ratio and water addition is 5%and 7.0% respectively;sintering bed should increase to 800 mm gradually.At last,Jingtang sintering plant was put into production successfully and yields stably,with the bed depth of 800 mm and advanced sintering indexes.

超高料层双层烧结富氧强化及烟气排放行为研究

针对超高料层双层烧结矿强度低的问题,采用富氧方法强化双层烧结。研究富氧浓度和燃料用量对烧结矿产质量的影响,分析普通双层烧结和富氧强化双层烧结的烧结矿主要矿物组成和微观结构,研究两者烧结烟气中O_(2)、CO_(2)和CO的排放行为。研究结果表明:富氧方法能明显强化超高料层双层烧结,大幅度提高烧结矿成品率和转鼓强度;二次点火后对料层进行富氧,氧气体积分数为25%,烧结矿成品率、转鼓强度、利用系数和固体燃耗分别为69.06%、66.40%、2.09t/(m^(2)∙h)和53.79kg/t,与普通双层烧结指标相比,成品率、转鼓强度和利用系数分别提高4.11%、7.73%、0.18t/(m^(2)∙h),固体燃耗降低3.23kg/t;富氧使烧结矿中磁铁矿氧化充分,铁酸钙大量生成,烧结矿结构均质、紧密;富氧增大烧结烟气O_(2)质量分数,可有效解决下部料层缺氧问题,提高燃料燃烧效率,减少CO排放量。

烧结主抽风机出口烟道振动分析及控制措施

近年来,不少烧结厂主抽风机出口到脱硫入口之间的烟道出现了振动问题。针对此问题,本文分析了烧结机风箱支管不同的布置形式对大烟道中废气温度、压力及流量的影响,分析了主抽风机出口至脱硫入口之间烟道布置形式对烟道内气流的影响,分析了风机在其性能曲线的非稳定区运行对风流系统的影响,并结合某些烧结机现场调试数据进行了具体的分析及研究。结果表明,主抽风机与脱硫脱硝之间的烟道设计形式,高负压、低风量的烧结操作模式等均可造成主抽风机出口烟道振动。通过优化烟道设计形式、使烧结生产在合适的工况条件下进行可减轻或消除主抽风机出口烟道的振动。

黏结剂喷射成形技术研究进展

黏结剂喷射成形是一种基于粉末床的增材制造技术,通过液态黏结剂的沉积以选择性地连接粉末颗粒,实现近净成形,最后通过烧结进行固结。该技术因为工艺简单、材料适应性广、成形效率高、批量化生产潜力大而受到关注。本文对黏结剂喷射成形的工艺流程进行了概述,总结了影响黏结剂喷射成形过程的因素。粉末特性、铺粉方式、黏结剂种类及其与粉床的相互作用是控制生坯密度、尺寸精度的关键。烧结及熔渗是主要的后处理方式,借助助烧剂、分步烧结工艺、超固相线液相烧结等方式可实现更高程度的致密化。黏结剂喷射成形已在铸造、医疗器械、3C行业等得到了广泛的应用,通过进一步优化黏结剂体系、全流程自动化设备和提升致密化及后处理技术可推动黏结剂喷射成形技术的大规模产业化。

生物质合成灰的烧结熔融特性和矿物转变规律实验研究

【目的】研究生物质在流化床燃烧过程的结焦问题,分析钾盐形式和含量对生物质灰烧结熔融特性的影响。【方法】借助扫描电子显微镜耦合能谱仪、X射线衍射仪、X射线荧光分析仪和FactSage热力学计算软件,通过实验分析了生物质合成灰的烧结熔融特性和矿物转变规律。【结果】在流化床的典型运行温度750~950℃范围内,合成灰的烧结熔融程度随温度以及钾盐质量分数的增加而加剧。此外,钾盐形式不同,其对生物质合成灰的烧结熔融特性的影响也有显著差异:钾盐为K_(2)CO_(3)时,合成灰中液相比例最高可达34.36%,合成灰由此发生严重烧结;钾盐为KCl时,大部分K和Cl元素在750~850℃逃逸,合成灰的烧结程度较K_(2)CO_(3)有所减弱;钾盐为K2SO4时,合成灰中液相含量最少,烧结熔融程度也最弱。【结论】改变钾盐的存在形式并控制床温,有望缓解生物质在流化床燃烧过程的结焦问题。

超厚料层烧结过程固体燃料的分布规律

铁矿烧结以固体燃料作为主要热量来源,其热量高效利用对于烧结节能减排具有重要意义。本文聚焦超厚料层烧结条件下固体燃料在料层中的分布特性,系统解析其在泥辊宽度方向以及料层高度方向的分布规律。结果表明:沿泥辊宽度方向,整体混合料粒度中间偏细、两侧略粗,而含碳量则为中间偏高、两侧略低;布料之后,台车宽度方向混合料粒度组成和含碳量与泥辊对应位置处的混合料规律一致;在料层高度方向上,自上而下混合料粒度整体呈增大趋势,含碳量则逐渐减小,由于泥辊与九辊布料的偏析程度有限,在部分高度处粒度与含碳量会出现波动;利用台车高度方向混合料的粒度组成和泥辊下料处各粒级的含碳量计算出沿料层高度方向的燃料分布,与实际规律基本一致。研究结果可为超厚料层烧结过程固体燃料的优化分布提供指导。

High Speed Sintering:Assessing the Influence of Energy Input on Microstructure and Mechanical Properties of Polyether Block Amide(PEBA)Parts

High speed sintering,a new powder-bed fusion additive manufacturing technology,utilizes infrared lights(IR)to intensely heat and melt polymer powders.The presence of defects such as porosity,which is associated with particle coalescence,is highly dependdent on the level of energy input.This study investigate the influcence of energy input on porosity and its subsequent effects on the mechanical properties and microstructures of PEBA parts.The parts were manufactured with a variety of lamp powers,resulting in a range of energy input levels spanning from low to high.Subsequebtly,they underwent testing using Archimedes’method,followed by tensile testing.The porosity,mechanical characteristics,and energy input exhibit a strong correlation;inadequate energy input was the primary cause of pore formation.Using the reduced IR light power resulted in the following outcomes:porosity,ultimate tensile strength,and elongation of 1.37%,7.6 MPa,and 194.2%,respectively.When the energy input was further increased,the porosity was reduced to as low as 0.05%and the ultimate tensile strength and elongation were increased to their peak values of 233.8%and 9.1 MPa,respectively.

超厚料层烧结水碳结构优化研究

为保证料层厚度由600 mm提高至1000 mm后,烧结生产稳定顺行,通过烧结杯实验,研究了料层厚度及水碳结构对料层透气性和烧结矿质量的影响。优化后烧结产能及质量得到改善,垂烧速度、转鼓指数和整体利用系数由15.2 mm/min、65.0%和1.23 t/(m^(2)·h)提高至22.3 mm/min、68.9%和1.54 t/(m^(2)·h)。确认了现场烧结原料结构下的最佳配水量为7.5%,同时不降低固体燃料用量,为超厚料层烧结稳定生产提供了数据指导。

凌钢1^(#)烧结机提高烧结矿转鼓强度生产实践

介绍了2021年以来凌钢第二炼铁厂1^(#)烧结机为了提高烧结矿转鼓强度而进行的系列生产实践。结果表明,采用厚料层烧结、实行生产参数标准化控制、强化热风烧结作用、提高混合料布料精度、提高机前混合料温度等措施可有效提高烧结矿转鼓强度,满足高炉的生产需要。

基于烧结工序的半干法烧结废气脱硫脱硝工艺节能减排研究

传统的烧结废气治理方法往往能耗较高,不仅增加了企业的生产成本,还加剧了能源资源的紧张局面。对此,基于传统半干法脱硫脱硝技术进行改进,提出一种半干法循环流化床脱硫除尘与中低温选择性催化还原技术结合的综合技术。经实验分析表明:该研究技术下节约的电力约是改进前半干法工艺的2.47倍,是湿法脱硫+SCR脱硝技术的1.97倍;基于研究技术的烧结废气处理工艺耗气量最低,平均每天耗气量约为0.34 m^(3)/t,改进前的半干法工艺技术的平均每天耗气量为0.74 m^(3)/t,湿法脱硫+SCR脱硝技术下平均每天耗气量为0.72 m^(3)/t。由此得出,改进后的半干法工艺可以达到烧结废气处理中节约能耗的效果。

超高料层烧结工艺下优化料层透气性生产实践

传统烧结料层厚度因料层透气性被限制在750~800 mm,从而影响了烧结矿的生产效率。在不影响烧结矿质量的前提下,改善料层透气性,有效提高烧结料层厚度已成为进一步提高烧结矿生产效率的重要途径。涟钢360 m 2烧结机,通过加强制粒性能,优化原料结构,改进生石灰下料设备,优化圆筒混合机扬料角钢方式等措施,强化制粒,改善了烧结料层的透气性。相比于料层厚度700~750 mm烧结,料层厚度950~1000 mm超高料层条件下,烧结矿的转鼓强度逐步提高至79.23%,利用系数稳定在1.50 t/(m^(2)*h)以上,固体燃耗稳定在51.48 kg/t,返矿配比降低至21.52%,为超高料层烧结(1000 mm)提高烧结矿生产效率提供了参考。

选择性激光烧结中铺粉过程离散元模拟

铺粉过程是选择性面激光烧结中重要的工艺过程之一,为研究铺粉过程中不同工艺参数对粉末床铺粉质量的影响,研究并设计了一种辊子-刮板式的铺粉结构,以PES为烧结粉末材料,通过EDEM软件对铺粉过程进行离散元仿真。模拟分析了辊子-刮板的移动速度V和刮板端部倾斜角度α对粉末床铺粉质量的影响。结果表明:辊子-刮板的移动速度V越大,铺粉质量越差;刮板端部倾斜角度α对粉末床铺粉质量影响很小。

Investigation on the evolution characteristics of bed porous structure during iron ore sintering

To better understand the evolution characteristics of bed porous structure during iron ore sintering,X-ray computed tomography scanning technology was used to analyze the pore parameters in different areas of the sintering bed.A pore skeleton structure model was established to study the characteristics of the airflow channels in different zones.The absolute permeability of different areas was calculated through simulation,and the corresponding streamline and pressure drop distribution were analyzed.The results show that the porosity of raw material zone,high-temperature zone,and sintered zone increases gradually,which are 37.69%,46.41%,and 55.57%,respectively.The absolute permeability calculation results of the raw material zone and sintered zones are 792.49μm^(2) and 20560.80μm^(2),while the tortuosity is 1.77 and 1.45,respectively.Compared with the raw material zone,the flow streamline in the sintered zone is thicker and denser,the airflow resistance and the pressure drop are minor.