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.     

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.     

Influence of coal weathering on coke quality

Abstract

In previous weathering studies carried out at the Instituto Nacional del Carbón (INCAR) on a typical complex coal blend composed of 13 different coals and used by the Spanish steel industry, it was concluded that, with regard to coke quality, no significant changes occurred over a storage period of 10 months, whereas after this date impairment was observed. However, the behaviours of selected individual coals, which were components of this coking blend, were rather different. Coke quality improved, was impaired or did not change in some cases, as a result of weathering over a period of ~6 months. In certain cases, slight weathering improved the quality not only of cokes from high volatile or high fluidity coals but also of those from medium and low volatile coals. Hence, the behaviour of an industrial coal blend in conditions of slight weathering can be influenced by the compensating effects of the behaviours of individual coals.     

煤气返回炼焦过程焦炭脱硫探索试验

根据有关文献所述的试验室试验结果推论,煤气部分返回炼焦过程可以进行焦炭脱硫.为了解这一方法是否可行,采用两个高硫单种煤和一个生产配煤,在20 kg试验焦炉中进行了探索试验.在结焦后期,从焦饼中心部位通入焦炉煤气,进行煤气返回炼焦过程焦炭脱硫试验.为掌握煤气返回炉内的时机及煤气流量改变对结果的影响,共进行了11次试验.结果表明,在室式炼焦过程中,煤气返回炼焦过程没有脱硫效果,相反,焦炭冷强度和热性能都有不同程度劣化.     

提高首钢京唐公司焦炉煤气产率的措施

研究了首钢京唐公司常用介休焦煤、屯兰焦煤、马兰肥煤和霍州肥煤4 种炼焦产物的分布。结果表明,屯兰焦煤和介休焦煤虽然同属于焦煤,但屯兰焦煤的焦炉煤气产率高于介休焦煤,炼焦后所得焦炭的冷强度略差,热强度基本不变;配煤过程中提高霍州肥煤的配入比例可提高焦炉煤气产率,但霍州肥煤炼焦后所得焦炭的热强度劣于马兰肥煤。另外,炼焦过程中能够提高焦炉煤气产率的炼焦煤往往会导致焦炭的强度降低,为此在配煤过程中对煤种的选择要综合考虑焦炉煤气产率和焦炭质量之间的平衡。     

Potential of semi-soft coals as replacement for hard coals in stamp charging blend

Abstract

In India the use of appropriate imported coals to supplement the inherent deficiencies of indigenous coals for cokemaking is in vogue. Stamp charging is very efficacious for inferior coking coals and has enabled Tata Steel to produce coke of international quality. It has been found to offer scope for the utilisation of less expensive imported semi-soft coals to replace expensive imported hard coals. Extensive tests were carried out to assess the blending potential of semi-soft coals for cokemaking by stamp charging in a 7 kg mini-oven, and a 600 kg pilot oven in the laboratory. This was followed by commercial scale trials. The test results clearly indicated that hard coals can be replaced with 30–35% of semi-soft coals in the stamp charging blend at Tata Steel without any compromise of coke strength. Semi-soft coals are now in regular use in all Tata's stamp charged batteries.     

鞍钢鲅鱼圈煤岩配煤技术的开发与应用

针对鞍钢鲅鱼圈所处中国东北部港口的独特地理位置特点,建立了适合鞍钢鲅鱼圈的煤岩配煤方法,分析了鞍钢鲅鱼圈配煤方案工程应用中各煤种用煤特点,考察了工程应用配煤方案的煤岩特征,并对应用煤岩配煤方案所得焦炭质量进行了分析,论述了鞍钢鲅鱼圈开展煤岩配煤技术为企业所创造的经济效益。结果显示,鞍钢鲅鱼圈通过煤岩配煤技术的研究开发与应用,使炼焦用煤结构从以肥煤为主向以进口炼焦煤为主、国产劣质炼焦煤为辅的低成本炼焦用煤结构转变,在满足大型高炉用焦质量要求的前提下,不断优化配煤方案,逐步提高焦炭质量,使焦炭的反应性从27.36%下降到24.95%,反应后强度从62.20%提高到65.37%以上。     

炼焦煤灰分对其结焦性的影响规律

 炼焦煤灰分是决定其价格的重要因素,为比较同一矿点煤种灰分对结焦性质的影响规律,对各炼焦煤进行黏结性、煤岩特征、灰分等分析并进行40 kg试验焦炉炼焦试验分析。研究表明,不同煤种炼焦煤灰分降低对黏结性改善幅度不同,黏结性较好的炼焦煤当其灰分降低时,黏结性改善不明显;黏结性较差的炼焦煤当灰分降低时,其黏结性改善较为明显;且不同煤种炼焦煤灰分降低时灰组成变化规律不同。不同煤种炼焦煤灰分降低时所炼焦炭其强度变化程度不同,黏结性较好的炼焦煤,当其灰分降低,所炼焦炭强度变化幅度不大;黏结性较差的炼焦煤,当其灰分降低时,所炼焦炭强度改善较大。     

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。     

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。     

加拿大焦煤和国内几种常用焦煤的结焦性差异

 研究了加拿大焦煤和国内常用主焦煤的结焦性差异,有利于国内焦化企业很好地利用加拿大炼焦煤,优化配煤生产。对加拿大煤和国内常用焦煤进行常规煤质分析和煤岩特征分析,探寻了二者黏结性存在差异的原因,并利用40 kg小焦炉进行加拿大焦煤替代国内优质焦煤实验。研究表明：与国内主焦煤相比,加拿大焦煤的单一性较好,灰分较低,变质程度较低;加拿大煤的基氏流动度lgMF和奥亚膨胀度[b]值较低,均质镜质组较少,且镜质组中含有较多裂纹和气孔,造成加拿大焦煤在成焦过程中熔融阶段流动性较小,膨胀压力较小;加拿大焦煤替代国内优质炼焦煤进行配煤炼焦,可以稳定焦炭质量。     

风选调湿技术对炼焦煤焦化性能的影响

采用炼焦煤风选调湿技术,对混合煤进行了风选分级,并通过煤样分析、堆密度试验和40 kg焦炉炼焦试验,分析了风选调湿分级粉碎后粒度分布与湿度对焦化性能的影响。对炼焦煤样按分级粉碎与不分级粉碎处理,并在此基础上进行选择性筛分和细度调整,按6种粒度分布进行对比试验。结果表明,采用分级粉碎焦炭的抗碎强度M40提高1.9%～5.8%,耐磨强度M10改善0.1%～0.3%;煤样的粉碎细度从73.0%提高到84.0%,焦炭的抗碎强度提高2.4%～4.1%,焦炭的耐磨强度改善0.5%～0.7%;筛除部分小于1 mm颗粒的煤样堆密度提高,焦炭的耐磨强度改善。煤样的堆密度随着煤样水分的增加而逐渐减小,当煤样水分大于8%时逐渐趋于稳定。给出了堆密度与煤样水分的非线性回归方程,进行了中位径、煤样水分对堆密度影响的双因素方差分析。研究结果有利于风选调湿技术的工程优化设计改进。     

炼焦煤的煤岩特征对其结焦性质的影响

 随着煤岩测定技术的进步,炼焦煤的煤岩性质已在炼焦配煤中得到广泛应用。通过对多种单种煤和配合煤的煤岩特征以及对应的40 kg试验焦炉所炼焦炭的性质进行分析和比较,结果表明：单煤种的R0max在1.3%～15%间,所炼制焦炭的冷态机械强度（M40和M10）最好,其热性质（反应性CRI和反应后强度CSR）也较好;配合煤反射率分布图特征越接近正态分布,则所炼制的焦炭冷态机械强度（M40、M10）就较好,配合煤反射率分布图特征偏离正态分布越远,其焦炭热性质越差;40 kg试验焦炉所得焦炭的反应性CRI高,其反应后强度CSR较低,存在负相关线形关系。     

加拿大泰科焦煤煤质研究

通过对加拿大泰科焦煤和八矿焦煤的性质的研究,包括单种煤性质研究和配合煤成焦后的性质研究,发现泰科煤虽然单种煤成焦性能比较好,但是在配合煤中只能部分取代国内优质主焦煤;利用泰科煤低灰、低硫的特点适当配入,可以降低焦炭的灰分和硫含量。     

不同变质程度煤焦炭光学组织与冷热性能

 为研究煤的变质程度对焦炭光学组织的影响以及焦炭光学组织和冷热性能的关系,对30余种炼焦煤的镜质体最大反射率以及成焦后焦炭的光学组织和冷热性能进行测试。结果表明,焦炭的光学组织随炼焦煤的变质程度呈现规律性变化,镶嵌结构体积分数随镜质体最大反射率变化可分为快速增加、平稳和缓慢下降3 个阶段;∑ISO 体积分数随镜质体最大反射率的变化趋势与之相反。焦炭的冷热性能和光学组织体积分数之间可以建立回归方程,焦炭的反应性随着∑ISO体积分数的增加而升高,而反应后强度随镶嵌结构体积分数的增加而升高。回归方程用于指导炼焦生产后,经济效益显著。     

宝钢煤岩配煤方法的研究

在总结国内外煤岩配煤方法的基础上,确定了宝钢煤岩配煤的基本思想,并进行了试验设计。选择宝钢常用的炼焦煤,进行了21批单种煤改变惰性物含量的炼焦试验;参照生产配煤,改变配煤的强粘比和惰性物含量,进行了9批配煤炼焦试验,共获取有效数据357组。在理论分析与实际相结合的基础上,确定了宝钢煤岩配煤的参数;用试验获得的数据,进行数学分析获得宝钢焦炭强度预测模型,确定了宝钢煤岩配煤的方法。     

气煤替代1/3焦煤的配煤方案优化试验

为扩大炼焦煤资源、降低焦化企业配煤成本,通过坩埚焦试验和40 kg小焦炉试验考察了 3种气煤(分别记为QM1、QM2和QM3)替代某焦化企业工业配煤方案中1/3焦煤的可行性,并采用镜质体反射率分布图对气煤的适宜配入比例进行了优化.结果表明,在原生产配煤方案中,当气煤替换比为8％时,焦炭冷态强度变化较小,但其热态强度均有...     

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...     

COREX炉内块煤裂化成焦的热态强度

通过对COREX所用2种块煤在不同条件下所成半焦的显微结构、热态强度进行观察,分析了影响块煤成焦质量的内在因素。比较2种块煤所成半焦的组成结构及性能差异后,发现兴隆庄煤成焦结构要优于大同煤,但兴隆庄原煤组织反应性较高,故在前期其煤成焦强度低于大同煤,直至成焦结构较多时,才高于大同煤。通过对COREX风口焦及实验室自制半焦的微观形貌和性能进行对比,确定了风口焦的来源,风口前兴隆庄煤形成焦炭的表面呈现出较浅的孔洞,其热态强度明显高于大同煤形成的焦炭。     

熔融气化炉内块煤成焦后粉化现象的相关研究

采用200 kg级炼焦炉对熔融气化炉主要使用的2种块煤进行了不同时间的半焦裂解试验,比较了2种块煤成焦后的粒度分布和强度变化,发现B煤在炼焦炉内粉化严重,随结焦时间的延长其粒度降解度一直在升高,而A煤降解度在达到最大值后开始下降.对比了2种块煤生成半焦的矿相微观结构,A煤生成的半焦主要以镶嵌结构和各向同性结构为主,而B煤生成的半焦主要以类丝炭和各向同性结构为主;2种半焦均含有未成焦煤.通过分析熔融气化炉内取出的风口试样中不同粒度的含碳物质其矿相微观结构,认为在炉缸内6.3 mm的颗粒由2种块煤裂解成焦后的粉化现象所引起,且B煤的粉化是主要因素.