炼铁用生物质焦的制备及其性能

采用两种不同的升温制度对生物质进行碳化,碳化温度选为300、400、500、600和700℃,保温时间分别为30、60和90 min.利用扫描电镜及热重分析仪对所得生物质焦的成分、微观结构及燃烧性能等进行分析,并研究了制备条件对生物质焦的产率及与CO₂反应性的影响.结果表明,生物质焦具有与煤不同的典型管状或片状结构,其N、S、灰分、碱金属含量及燃烧性能优于煤炭,适合用作炼铁过程的还原剂和发热剂,以替代部分煤粉和焦炭.综合考虑,炼铁用生物质焦的最佳制备条件是,采用恒温加热模式将生物质加热至500℃进行碳化,并保温30 min.      

灰成分及光学组织对焦炭热性能的影响

根据唐钢现有配煤方案为基准,选取其中有代表性的焦炭为研究对象,研究灰成分及光学组织对焦炭热性能的影响。研究结果表明,焦炭灰成分变化对矿物质催化指数影响较大,焦炭的反应性随MCI(矿物质催化指数)的增加呈升高趋势,而焦炭的反应后强度随MCI的增加而降低;焦炭光学组织与各向异性指数的关系密切,焦炭的反应性随OTI(光学各向异性指数)的增加呈降低趋势,而焦炭的反应后强度随OTI的增加而升高。合理控制焦炭灰成分和光学组织的工艺参数对改善高炉内焦炭反应性和反应后强度有重要意义。     

Effect of coke reactivity and nut coke on blast furnace operation

Abstract

Two measures for coke saving and increase in blast furnace efficiency related to coke characteristics – reactivity and size – are discussed in this paper. Modern blast furnace operation with low coke rate and high injection rate causes a change in coke quality requirements. A discussion has arisen recently about highly reactive coke. Here, a theoretical analysis of influence of coke reactivity on the thermal reserve zone, direct reduction and carbon consumption in the blast furnace has been undertaken. Experiments have been performed using non-standard test scenarios that simulate coke behaviour under real blast furnace operating conditions. Coke reactivity and microstructure have also been investigated under the impact of alkali and pulverised coal ash and char. Operation of many blast furnaces has proved the possibility of coke saving and increase in productivity when using small-sized coke (so-called nut coke) mixed with the burden, but the reasons for this phenomenon, and consequently the limit for nut coke consumption, are still not very clear. An analytical method and cold model simulations have been used to quantify the change in shaft permeability and furnace productivity when using nut coke.     

兰炭和喷吹煤组成与结构特征对可磨性的影响

 低变质煤低温热解产物兰炭(半焦)用于高炉喷吹,可降低焦比,节约炼铁成本;但多数兰炭可磨性差,限制了其使用。以神木两种典型兰炭和两种喷吹煤为研究对象,分析比较了其破碎特征,采用XRF和XRD检测了兰炭和喷吹煤灰分中物相组成,采用SEM和氮气吸附法研究了兰炭和喷吹煤的破碎形貌和微观结构。结果表明,喷吹煤的可磨性高于兰炭,烟煤可磨性最优;钙、硅含量与可磨性之间存在协同和抑制作用,即钙含量越多,可磨性越高,且钙元素主要以CaO形式存在,硅的作用则相反;喷吹煤表面致密平整,而兰炭表面孔隙结构发达。在球磨过程中,喷吹煤以体积粉碎为主,而兰炭则以表面粉碎为主,粉碎方式不同是两者可磨性差异大的主要原因。     

熔融气化炉内块煤裂解特性的差异化分析

为了研究块煤在熔融气化炉内高温结构演变和降解机制,采用扫描电镜和光学显微镜观察了COREX熔融气化炉风口焦和实验室自制半焦的形貌和显微结构,并结合不同试样的高温反应特性,确定了不同风口焦试样的来源。结果表明,风口焦中兴隆庄块煤形成试样含有较多的中粒和粗粒镶嵌结构,表面呈孔状结构;大同块煤形成试样中类丝炭较多,表面呈层状结构。根据结果提出应考虑灰分对煤焦高温强度的影响,在测量风口焦试样的反应性及反应后强度时应考虑灰分含量进行折算,并确定了以灰分的基准含量为13%进行折算为最佳条件。     

CFD Modelling and Analysis of Pulverized Coal Injection in Blast Furnace: An Overview

In order to understand the complicated phenomena of pulverized coal injection (PCI) process in blast furnace (BF), several mathematical models have been developed by the UNSW and BSR cooperation. These models are featuring from coal combustion in a pilot‐scale test rig, to coal combustion in a real BF, and then to coal/coke combustion in a real BF, respectively. This paper reviews these PCI models in aspects of model developments and model applicability. The model development is firstly discussed in terms of model formulation, their new features and geometry/regions considered. The model applicability is then discussed in terms of main findings followed by the model evaluation on their advantages and limitations. It is indicated that the three PCI models are all able to describe PCI operation qualitatively. The model of coal/coke combustion in a real BF is more reliable for simulating in‐furnace phenomena of PCI operation qualitatively and quantitatively. Such model gives a more reliable burnout prediction over the raceway surface, which could better represent the amount of unburnt char entering the coke bed. These models are useful for understanding the flow‐thermo‐chemical behaviours and then optimising the PCI operation in practice.     

煤焦还原分解烧结烟气脱硫石膏的试验

 针对烟气脱硫石膏综合利用问题,提出了利用煤焦还原分解石膏制备CaO和SO2的新方法。采用FactSage 6.1计算了煤焦与脱硫石膏的高温反应特性,并利用热重分析仪在理论上分析了煤焦还原分解石膏行为的可行性。通过管式电阻炉试验进一步研究了温度、煤焦添加量、保温时间对石膏分解率和固态产物影响以及气体SO2释放规律。试验结果表明,升高温度、增加煤焦添加量和保温时间均能提高石膏的分解率;煤焦质量分数从5%增加到20%,CaO和SO2的质量分数先升高后下降,而CaS的质量分数一直增大;在煤焦量为11%时,CaO和SO2的质量分数达到最大值,CaO和SO2成分的变化规律主要受CaS和CaSO4相对含量的影响。采用煤焦还原分解石膏的方法,可为石膏综合利用提供理论指导。     

关于大量喷煤高炉的某些理论问题的思考

讨论了与高炉大量喷煤有关的某些理论问题,主要是高炉下部透气性和原料质量、热补偿和理论燃烧温度等。考虑到风口区煤粉的燃烧率及实际发生的化学反应,提出了计算理论燃烧温度的一种新方法。从保证未燃煤粉在高炉内完全消耗的角度提出了高炉的喷煤极限。     

Influence of carbon structure and mineral association of coals on their combustion characteristics for pulverized coal injection (PCI) application

The influence of carbon structure and mineral matter of three pulverized coals on their char characteristics including reactivity was studied under a range of combustion conditions in a drop tube furnce (DTF) and thermogravimetric (TGA) furnace for PCI application. Physical and chemical properties of coals and their combustion derivatives were characterized by automated reflectogram, X-ray diffraction, scanning electron microscope, and BET N₂ adsorption. The QEMSCAN technique was used to characterize the heterogeneous nature of minerals of discrete coal particles. The TGA char reactivity was related to the proportion of coal particles displaying strong association of calcium/sulfur phases with carbon matrix to highlight the catalytic influence of minerals on char reactivity at low temperatures. The study suggested that during DTF combustion tests at 1200 °C, char reaction rates might have been catalyzed by coal minerals, particularly due to illite and its association with carbon. Under the same combustion conditions, most of the coal minerals did not transform significantly to slag phases. Coal burnout was found to improve significantly in a combustion temperature range of 1200 °C to 1500 °C. The improvement of coal burnout with temperature appeared to be influenced by coal properties, particularly as a function of the chemical nature of minerals, as well as the degree of associations with other minerals. The study implies that coals with similar mineral compositions might not necessarily reflect similar combustion behavior due to the differences in their associations with other phases. The study highlighted the significance of the characterization of the heterogeneity of coal particles including mineral associations for a comprehensive and reliable assessment of the combustion performance of PCI in an operating blast furnace. QEMSCAN is a trademark of Intellection Pty Ltd., Milton, Queensland, Australia.     

Effect of Mineral on Metallurgical Coke Solution Loss Reaction in Blast Furnace

Thecokesolutionlossreactionisoneofthemostimportanteffectsresultingincokepulverizinginblastfurnace .Thefactorswhichaffectreactionincludecokeporestructure ,micro crystalstructureonporewall ,thecontentandconstituentofminer als ,etc .Amongthesefactors ,theconstituentofmineralsisemphasizedallovertheworldinrecentyears .Buttheemphasisofmoststudieswasputontheeffectofalkalimetals (K ,Na)oncokesolutionlossreactionandtheeffectofotherelementswassel domreported[1-5] .Theeffectofthirteenmineralsoncokesolut…     

一种X煤在首钢的应用实践

针对当前优质炼焦煤资源越来越少,而高炉生产对焦炭质量指标要求越来越高的情况下,对具有低灰、高硫特点的X煤进行了系统的炼焦试验研究。结果发现,在炼焦生产中合理配加5%～8%的X煤不会造成焦炭硫分升高的不利影响,焦炭灰分下降明显,强度保持稳定。该研究成果成功应用于首钢炼焦生产,焦炭各项指标均达标,这不仅扩大了炼焦煤的使用范围,而且在资源使用方面为公司焦炭灰分的降低提供了支持。     

重新认识高炉用焦炭与CO2的反应性

简要介绍了现行焦炭反应性试验方法的来源,主要表达焦炭在高炉内进入风口回旋区前抗CO2,气化能力以及反应后的抗粉化能力,是一种规范性试验方法。回顾了国内外对焦炭反应性的认识和变化,20世纪认为反应性表达焦炭在高炉抗CO2,的气化能力,反应性高反应后强度低对高炉生产不利。进入21世纪,新日铁提出反应性只是表达了焦炭的活性,认为提高反应性可以提高高炉反应效率,对高炉生产有利,不同时期认识水平不同认知也会完全相反。通过CO2,含量和反应温度对焦炭反应性影响试验和高炉碳平衡计算,分析了喷吹煤粉高炉内焦炭的行为．确定了焦炭进入风口回旋区前的反应失重率。提出现行国家标准“焦炭反应性及反应后强度试验方法”的反应性表达的是焦炭与CO2,反应的活性,高炉内焦炭反应失重率控制因素是矿石的还原性能和未燃煤粉率,与焦炭实验室测定的反应性无关。     

喷吹煤对焦炭热性能影响的研究

分析了安钢喷吹煤粉的反应性以及影响其反应性的因素。通过未燃煤粉、焦炭的共同反应试验,研究了高炉喷吹煤粉对焦炭热性能的影响。结果表明:未燃煤粉可减少焦炭的熔损反应,提高焦炭的反应后强度。     

优化配煤结构 降低配煤成本 改善焦炭质量

论述了近年来鞍钢进行的优化配煤结构的科研工作。以焦炭在高炉中劣化过程的研究为依据,转变对焦炭质量指标和配煤技术的认识。在配煤中,多配多价格较低的瘦煤和低灰、低硫的１／３焦煤;减少价格较高的强粘结性焦煤和肥煤的比例,使配煤原料成本大幅度降低,焦炭灰分下降。鞍钢１９９９年焦炭质量达到历史最好水平。同时炼铁高炉主要技术经济指标也达到历史最高水平。     

用于高炉喷吹的低阶煤梯级转化半焦的燃烧性能

 采用固定床热解装置制备神木长焰煤与凤眼莲和冶金工业固体废弃物热解终温分别为450和550 ℃的共热解半焦;利用管式沉降炉模拟高炉喷吹条件研究共热解半焦的燃烧性能,并考察了热解终温和共热解物质对半焦燃烧性能的影响。研究表明：高炉瓦斯泥和冷轧氧化铁红的加入起到催化煤热解的作用,其中高炉瓦斯泥的催化热解效果最优,挥发分析出的增幅为18.4%;煤与冷轧氧化铁红在热解终温550 ℃时共热解半焦的燃烬度最佳为98%,与550 ℃时的原煤半焦的燃烬度相比,提高了22.5%;SEM扫描电镜结果显示,煤与冷轧氧化铁红共热解半焦与原煤半焦相比,半焦表面产生了更多的裂纹;除煤与轧钢氧化铁皮及煤与高炉瓦斯泥共热解半焦外,试验所制备的其他共热解半焦的各项性能均符合中国喷吹用煤指标。     

焦肥煤配比对顶装和捣固焦性能的影响

为了解顶装焦和捣固焦在性能指标上的差异,利用300 kg试验焦炉研究了不同焦肥煤配比对顶装焦和捣固焦性能的影响规律。研究发现,焦肥煤配比由30%提高到60%,捣固炼焦可以改善焦炭冷热强度,且改善作用逐渐减弱;焦炭镶嵌结构体积分数逐渐升高,而同性结构体积分数逐渐降低;焦炭平均孔径逐渐升高,气孔率逐渐降低。焦炭的反应后强度随镶嵌结构体积分数的增大呈现升高趋势,而反应性随各向同性总和ΣISO体积分数的升高而升高。相同配煤结构情况下,捣固焦平均孔径偏低,气孔壁厚度增加,气孔率低约20%。     

配加大剂量气煤改质炼焦

 为了降低焦炭成本、减少主焦煤、增加低价气煤在配合煤中的用量,以2种气煤、2种肥煤、2种焦煤、1种瘦煤和1种自主研发的煤粉改质剂为原料,在2 kg实验室炼焦炉上开展了大比例气煤改质炼焦试验。试验结果表明,当主焦煤配比低于50%,气煤配比达到35%时,所炼制焦炭的质量指标将急剧恶化,其反应性(CRI)大于36%,反应后强度(CSR)低于50%,不能满足中、大型高炉顺行需求;但在改质剂的作用下,使用气煤逐步替代主焦煤炼焦时,所炼制改质焦炭的热态强度指标均得到显著改善,尽管配合煤中气煤配比提升到45%,主焦煤配比降到40%,仍能生产CRI小于30%,CSR大于58%的改质焦炭。结合SEM、XRD和Raman检测分析焦炭微观层面的差异,结果表明,在炼焦配合煤中添加大剂量气煤,会增加焦炭气孔的数量和尺寸以及无定型碳含量,同时降低焦炭微晶单元的体积和致密度,导致焦炭反应性增加,反应后强度降低;添加改质剂后,上述现象在改质焦炭中可得到显著改善,并且高比例气煤添加下所炼制改质焦炭微观结构和组分的分布可达到高比例主焦煤配加下所炼制生产焦炭的水平。最后,通过工业性试验验证了在改质剂的作用下向炼焦配合煤中添加45%气煤生产优质冶金焦炭是可行的,找到了一种节约主焦煤、降低炼焦配煤成本的新方法。     

CHARACTERISTICS OF INDIAN NON-COKING COALS AND IRON ORE REDUCTION BY THEIR CHARS FOR DIRECTLY REDUCED IRON PRODUCTION

Studies on the chemical and physical properties (proximate analysis, sulphur content, reactivity, iron ore reduction potential, caking index, and ash fusion temperatures) of coals, procured from 16 different mines in Orissa, India, were undertaken for their judicial selection in Indian sponge iron plants. These coals were found to have low sulphur (range of 0.40–0.66%) and a moderate-to-high ash (range: 22–53%) contents. The results indicated that there were no caking characteristics in any of the coals except Basundhara. The majority of the studied coal ashes were found to have higher fusion temperatures (ST: 1349–1547°C; HT: 1500–1663°C; and FT: 1510–1701°C). An increase in the fixed carbon content in the coal char, in general, led to a decrease in its reactivity toward CO₂. The majority of the chars exhibited significantly higher reactivities (>4.0 cc of CO/g·sec). Further reduction studies in coal chars at 900°C indicated an increase in the degree of reduction of fired hematite iron ore pellets with an increase of char reactivity and reduction time. The authors recommend using the majority of the studied coals as such and some of them (Lakhanpur, Samleshwari, Orient OC–4, and Dhera coals) after blending or beneficiation.     

武钢高炉经济性喷煤研究

为了使武钢高炉达到经济性喷煤的目标,通过煤资源调查,掌握了适合武钢喷吹用煤的煤源情况;通过对高炉大煤比条件下的风口理论燃烧温度进行计算,分析了影响高炉喷煤的主要因素;通过对武钢高炉炉尘中的残碳量及其来源进行分析,发现目前操作条件下炉尘中源自煤粉的碳量占总碳量的10%左右,此结果已用于研究未燃煤粉在炉内的利用状况及评估高炉喷吹煤粉的燃烧情况;通过对高炉操作指标进行统计分析,发现煤比在160~170 kg/t时,高炉燃料比较低。实践结果表明,上述经济性喷煤技术在5号高炉应用后,在煤比仅略增加0.8 kg/t的情况下,焦比降低了9.7 kg/t。     

炼焦工艺对干煤和湿煤成焦质量的影响

为了更好地优化炼焦工艺,有效地改善配合煤炼焦的成焦质量,系统性地分析了炼焦工艺及干煤和湿煤炼焦对焦炭强度与反应性的影响.采用5 kg试验焦炉对多种工况下的干煤(水分低于3％)和湿煤(水分高于6％)分别进行炼焦试验.通过研究装炉煤的水分、干基堆密度以及装炉温度对干煤和湿煤成焦强度及焦炭反应性(CRI)的影响,并结合干煤和...