Influence of coal fluidity on coal blend and coke quality

Abstract

The blast furnace coke quality depends on the characteristics of coal blend, precarbonisation techniques adopted such as stamping, vibrocompaction etc., and coking conditions. Of the above, coal blend plays a significant role in the production of quality coke. Furthermore, the quality of the blend depends on the quality of individual coals and their interaction making up the blend. Coal, being a highly heterogeneous material, requires special care for determination of its properties and blending of individual coals for coke making. Coal fluidity is one such important coking property which highly influences the coke quality. The hard coking coals having good fluidity, which yield good coke, however are not only very expensive, but also are limited in reserves. Unlike, other properties, coal loses its fluidity on weathering, i.e. oxidation in presence of air on long storage in the yard, and the fluidity value changes on blending with different coals. To understand the effect of coal fluidity on coal blending and there by the coke quality, studies have been conducted using the industrial scale coals and coal blends. An empirical relation has been developed between actual blend fluidity and calculated fluidity using logarithmic weighted average from fluidity of individual coals. Blending of non-coking coals above 20% with the hard coking coals used in this research decreases the blend fluidity and impairs the coke quality. It was seen that the coals lose their fluidity on weathering, and the value becomes less than half after a two months of storage at site. Weathering appears to be more rapid in case of semisoft than hard coking coals. The present paper discusses the influence of coal fluidity on coal blend fluidity and changes on weathering.     

加入添加剂提高焦炭质量工业试验

在焦炉上进行加入添加剂提高焦炭质量试验，添加剂为沥青，粉焦及两者的混合物。加入沥青粘地剂有利于稳定煤质，提高焦炭质量，特别是有利于提高焦炭Ｍ１０。当配有较强粘结性时，加入粉焦有利焦炭质量提高；当煤质粘结性差时，同时加入沥青和粉焦可改善焦炭质量。     

在配煤中添加煤粉改性剂对焦炭质量的影响

在南钢40kg实验焦炉开展配加非炼焦煤炼焦实验,研究了在配煤中添加煤粉改性剂(zzz)对配合煤、焦炭质量的影响。采取不同配量的改性剂添加方案进行配煤炼焦实验,通过实验确定出最佳配煤方案:非炼焦煤配加量达到15%(粒度小于3mm),煤粉改性剂添加量为0.10%。最佳配煤方案中添加改性剂与未添加改性剂炼出的焦炭质量相比,灰分、硫分基本保持不变,抗碎强度M40增加14.35%,耐磨强度M10下降6.00%,反应性降低5.5%,反应后强度提高5.93%,实验结果表明:焦炭冷态强度与热态性能指标均接近于南钢生产配煤焦炭质量。     

煤岩配煤在湘钢焦化厂的应用

论述了湘钢目前利用煤岩学数据指标判定进厂煤质情况,指导煤场分堆,优化配煤结构.同时在保证焦炭质量稳定的前提下,配入少量低灰的气煤,有效地提高了焦炭质量.     

山西炼焦煤资源状况分析与太钢炼焦配煤结构的对策

对山西省炼焦煤资源和目前焦化行业发展形势进行了简要分析,追溯了太钢焦化厂的配煤历史,结合焦炭质量变化情况,对太钢炼焦配煤结构提出了改进建议。     

焦炭热性质加和性在配煤研究中的应用

结合配西加煤实验,提出了配煤所涉煤种对应的焦炭热性质(反应性/反应后强度)具有加和性的观点,在对方案中所涉及的变化煤种对应的焦炭热性质数据进行假定与修正的基础上,结合各方案中煤种比例,对各方案进行比较及计算得出了计算值与实验值一致的结果,从而证实煤种对应的焦炭热性质在配煤中具有加和性。该结论可以为生产中设计配煤方案提供便利,从而指导配煤炼焦生产,稳定和提高焦炭质量。     

山西炼焦煤资源状况分析与太钢炼焦配煤结构的对策

时山西省炼焦煤资源和目前焦化行业发展形势进行了简要分析。追溯了太钢焦化厂的配煤历史,结合焦炭质量变化情况。对太钢炼焦配煤结构提出了改进建议。     

稳定和改善焦炭质量的途径

从焦炭在高炉内的劣化原因着手,结合装炉煤灰分、粘结性、焦炭显微结构方面的影响因素,分析影响酒钢焦炭强度的因素,提出稳定和改善焦炭质量的途径.     

Microtextural analysis of coke from single and binary blend and its impact on coke quality

Coke microtexture and microstructure is a function of feed coal composition and carbonisation process. If the process remains constant, the composition plays a vital role in developing the microtexture and microstructure which also reflects the coke quality. Knowledge of the influence of coal composition and characteristics on coke quality is a must for formulating a coal blend for coke making. To better understand how the coal transforms into coke requires the ability to correlate the microtextural and microstructural features to coal properties. Petrography is an important tool for comparing the feed coal and corresponding coke. In the present study, cokes manufactured from single coals and two-component blends under similar coking conditions were studied under the microscope to provide valuable information to coke makers. Not only the rank and quantification of macerals but also the association of macerals and minerals play an important role. Also the size and type of inertinite affect the coke quality. Micro-cracking, crack lengths and fissures identify the zone of weakness, whereas microtexture of cell walls suggests the strength-controlling parameters of coke. Pictorial concept followed in the present study is given below:     

鞍钢配型煤炼焦工业炉孔试验

为满足高炉大型化和氧煤大喷吹对焦炭质量提出了更高的要求，进行了鞍钢配型煤炼焦的工业试验，结果表明：（１）在现有生产配煤条件下，配型煤焦炭Ｍ４０提高２．０个百分点，Ｍ１０改善１．２个百分点；（２）在现有生产配煤中多配１２％高挥发分弱粘结性煤的情况下，配型煤焦炭的Ｍ４０提高１．７个百分点，Ｍ１０改善了１．０个百分点（３）提出的鞍钢配型煤工艺流程，可充分利用鞍钢现有设备及设施，比宝钢流程更为简化。     

配入活性添加物炼焦新技术的开发

根据活性添加物的物理、化学特性及反应机理,研究了各种活性添加物对改善炼焦煤粘结性、增加炼焦过程结焦性的作用与效果,开发了有效的活性添加物,可扩大炼焦煤资源,节约优质炼焦煤,降低配煤成本,提高焦炭强度。     

高膨胀澳洲焦煤的配煤炼焦试验研究

澳洲某矿焦煤具有较高的粘结性和丰富的胶质体,国内大多焦化企业将其作为优质焦煤配用。经煤质分析发现,该矿点焦煤流动度低,仅256ddpm,膨胀度高,坩埚自由膨胀序数(CSN)达9,已达到肥煤指标,煤质非常特殊,配用不当,不仅容易产生大量泡焦,而且对炉墙破坏较大,但其单种煤成焦反应后强度高,可替代少量优质焦煤,配用时需控制配合煤的膨胀度。     

优化6m焦炉配煤方案,提高焦炭质量

济钢的两座6m焦炉投产初期焦炭强度波动,为此,以20kg小焦炉试验、岩相检测、焦炭反应性和反应后强度检测为主要试验手段,对新汶、官庄、圣佛、阳泉曲、新坡、两度、卜村等10多个煤种作了70余炉配煤炼焦试验,优化了配煤,完善了6m焦炉的用煤结构。     

白煤在配煤炼焦中的应用

 在2 kg试验焦炉开展配白煤炼焦试验,研究了煤粉改性剂（zzz）对配合煤、焦炭质量的影响。确定出白煤的最佳配加粒度、最佳配加量以及zzz的最佳配加量。通过试验确定出最佳配煤方案：白煤配加量达到8%（粒度小于3 mm）,zzz量配加0.10%。由最佳试验方案炼得焦炭的冷态强度M40、M10和热态性质CRI、CSR都可以达到南钢生产焦炭质量的水平。试验方案在南钢40 kg试验焦炉中进行也取得了很好的效果。     

用1／3焦煤替代肥煤炼焦探索

介绍了肥煤和1／3焦煤的煤岩特性,指出可用适量质量相近的1／3焦煤代替稀缺肥煤进行炼焦,既能保证焦炭质量,又能降低配煤成本,实现节约优质炼焦煤之目的。     

添加无烟煤对焦炭微晶和气孔结构的影响

根据焦炭的XRD谱图及SCHERRER'S 公式研究了添加无烟煤炼焦后焦炭的微晶结构参数的变化.试验结果表明:添加无烟煤可以促进焦炭中微晶的发展,使焦炭微晶结构参数La、Lc和石墨化度增大.利用氮气吸附方法分析了焦炭气孔结构的变化,结果发现:添加无烟煤炼焦后焦炭的微孔体积、比表面积和平均孔径都有显著的降低.根据FHH模型计算了焦炭的分形维数.结果表明:在焦炭中存在分形结构,添加无烟煤炼焦后焦炭的分形维数降低,焦炭表面变光滑.     

一种特征煤代替肥煤的配煤炼焦试验

在对特征煤基础特性分析的基础上,用特征煤替代部分肥煤和气煤进行了40 kg小焦炉及4.3 m顶装焦炉炼焦试验,结果表明,特征煤代替肥煤配量控制在20%以内,焦炭质量变化不大,热态强度略有改善,在常规顶装焦炉上用10%～15%的特征煤代替肥煤炼焦是可行的。增配10%特征煤、相应减少肥煤配量8%、气煤2%,可生产出高强度一级冶金焦（M40=84.3%、M10=7.2%,CRI=23.5%、CSR=69.7%）,降低配煤成本19.1元/t。     

结焦时间对冶金焦热态性能的影响

焦炭的质量主要取决于配合煤质量和炼焦操作。配合煤质量和炼焦加热温度对焦炭质量的影响已有详尽论述，但结焦时间对焦炭质量的影响还没有深入的研究。塔塔钢厂的实验表明．焖炉可提高焦炭的平均尺寸和焦炭结构的致密性。焦炭经重大的结构变化．使其各向同性结构减少．粗粒和细粒镶嵌结构的数量增加。孔径减小。随着结焦时间的延长，焦炭的热态性能。即焦炭反应性（CRI）和反应后强度（CSR），均得到提高。     

Importance of Mineralogical Data for Influencing Properties of Coke: a Reference on Si02 Polymorphs

SiO₂ occurs in coking coals as pure quartz and also in complex aluminosilicates. At coking temperatures, pure SiO₂ has several polymorphs (α‐ and β‐quartz and β‐tridymite) and transformations from one to another are accompanied by volume changes in the mineral matter that can lead to the formation of cavities and cracks in a coke matrix. These can weaken the coke physical strength and lead to a higher circulation of gases within the pieces. The grain size of the primary quartz crystals in a coal blend is also important for the estimation of coke strength: the larger the crystals that occur in a coal, the larger the cavities and cracks that will ensue (weaker coke). The occurrence of any given SiO₂ polymorph indicates the temperature of its formation and can be used to correlate other changes in coke‐forming compounds with certain temperatures. A high amount of free quartz in a coal blend can be considered a negative factor for coking. For a better understanding of the influence of bulk SiO₂ on coke quality, mineralogical (phase) analysis and quartz grain size measurements on coking coals can be helpful. Under the blast furnace conditions, SiO₂ polymorphs have no substantial influence on the coke physical strength.     

Effect of Indian Medium Coking Coal on Coke Quality in Non-recovery Stamp Charged Coke Oven

The maximum possibility of utilizing the Indian coking coals and inferior grade coking coal for producing metallurgical coke through non-recovery stamp charging technology was investigated.Indian indigenous coals contained low percent of vitrinite(50%)and higher content of ash(15%)compared to imported coking coal.Therefore,the selection of appropriate proportion of different types of coals was a major challenge for coke makers.Coal blend selection criterion based on a single coefficient,named as composite coking potential(CCP),was developed.The use of increased proportion of semi-soft coal(crucible swelling number of 2.5)and high ash(≥15%)indigenous coal in the range of 20%-35%and 20%-65%respectively in the blends resulted in good quality of coke.Plant data of a non-recovery coke oven were used for developing and validating the model.The results showed that the coke strength after reaction(CSR)varied in the range of 63.7%-67.7%and the M40value was between 81.8and 89.3in both the cases.