Fissure formation in coke. 1: The mechanism of fissuring

Pilot scale coke oven experiments, in which carbonisation has been arrested after 2 and 4 h, have been used to identify key aspects of the initial formation and propagation of fissuring in coke. The experiments show that the primary fissure network is formed within the first few hours of coking and the fissures propagate towards the centre of the oven as coking progresses. They also show that some of the initially formed fissures stop propagating, thus increasing the effective fissure spacing as coking continues. A model for the propagation of regular crack arrays has been used to identify the cause of the initial formation of the fissure network, evaluate the fissure spacing and explain the fissure coarsening effect. The coarsening is shown to be due to an instability, in the form of every second fissure stopping. The formation of lateral fissures is shown to be due to tensile stress formation near the tips of stopped fissures and also to increased shrinkage due to a maximum in the coke contraction coefficient at around 700 °C.     

Fissure formation in coke. 3: Coke size distribution and statistical analysis

A model of coke stabilization, based on a fundamental model of fissuring during carbonisation is used to demonstrate the applicability of the fissuring model to actual coke size distributions. The results indicate that the degree of stabilization is important in determining the size distribution. A modified form of the Weibull distribution is shown to provide a better representation of the whole coke size distribution compared to the Rosin-Rammler distribution, which is generally only fitted to the lump coke. A statistical analysis of a large number of experiments in a pilot scale coke oven shows reasonably good prediction of the coke mean size, based on parameters related to blend rank, amount of low rank coal, fluidity and ash. However, the prediction of measures of the spread of the size distribution is more problematic. The fissuring model, the size distribution representation and the statistical analysis together provide a comprehensive capability for understanding and predicting the mean size and distribution of coke lumps produced during carbonisation.     

焦炭气孔率对焦炭热性能的影响

通过研究40kg试验焦炉单种煤焦炭、配合煤焦炭及工业焦炉焦炭的气孔结构及焦炭热性能,得出气孔率对焦炭热性能的影响。焦炭气孔率对焦炭热性能有较大影响,随着气孔率的增加,CRI增加,CSR降低;工业焦炉焦炭气孔率与焦炭热强度之间关系密切,气孔率每增加1％,CRI增加0．48％,CSR降低1．46％。用气孔率预测焦炭热性能,对指导焦炭生产、控制焦炭热性能具有指导意义。     

Basic study on separate charge of coal and waste plastics in coke oven chamber

Nippon Steel Corporation started to operate a waste plastic recycling process using coke ovens at Nagoya and Kimitsu Works in 2000 and at Yawata and Muroran Works in 2002. Now the total capacity is 120,000 tons per year and the recycling process is operating smoothly. In this process, coals and added plastics are carbonized and changed into coke, tar, oil and coke oven gas in a coke oven chamber. At present, upper limit of the addition rate of waste plastics to blended coals is 1% so that the plastic addition does not affect coke strength. However, the amount of waste plastics in Japan is as much as about 10 million tons per year and there is a real need for increasing the amount of waste plastics treated by the waste plastic recycling process using coke ovens. We investigated a method of increasing the addition rate of waste plastics without affecting coke strength by charging coal and plastic separately in a coke oven chamber. In the case of the same plastic addition rate, charging the plastic in the bottom or the top part of the coke oven chamber can decrease the deterioration of coke strength compared with charging a homogeneous mixture of coal and plastic. Charging the plastic in the bottom decreases the coke strength to a greater extent than charging the plastic in the top. This is because the decomposition of the plastic charged in the bottom decreases the bulk density of the upper coal layer. The results suggest that charging the coal and waste plastics separately increases the amount of waste plastics treated in the waste plastic recycling process using coke ovens. In order to commercialize this method, further studies are necessary concerning the charging method, device and the effect of this method on the coke oven operation.     

OCC工艺在宽幅焦炉上的研究与应用

根据宽幅焦炉的热工特点,在焦炉加热优化串级调控系统中（简称OCC工艺）．采用焦炉煤气加热单侧控制,用煤气主管压力进行炉温反馈调节,及与机、焦侧分烟道吸力相联动,实现焦炉加热全自动控制。实践证明,系统应用后焦炉炉温稳定、能耗降低、焦炭质量显著提高。     

捣固炼焦对焦炭质量的影响

利用40kg试验焦炉进行顶装与捣固炼焦试验,对比分析发现,捣固炼焦工艺可以明显改善焦炭的冷态强度,提高焦炭抗碎强度,改善耐磨强度,还可提高焦炭的反应后强度,但对焦炭的反应性影响不大,可以使焦炭粒度组成更加均匀化。     

The effect of plastic size on coke quality and coking pressure in the co-carbonization of coal/plastic in coke oven

In the recycling process of waste plastics using coke ovens, coals and added plastics are carbonized and changed into coke, tar, oil and coke oven gas in a coke oven chamber. In this study, the effect of added plastic size on coke quality and the effect of plastic addition on coking pressure was investigated. In the case of a plastic addition rate of 2%, the coke strength reached a minimum at the particle size of 10 mm for polyethylene (PE) and 3 mm for polystyrene (PS). The mechanism was attributed to the weak coke structure formed on the interface between plastic and coal. The result indicates that large or small plastic particles are favorable in order to add waste plastics to blended coals for coke making without affecting coke strength . Furthermore, it was also shown that a 1% addition of large size agglomerated waste plastics to blended coals did not increase coking pressure. Based on this fundamental study, and considering the ease of handling plastics, we have determined that the size of waste plastic used in a commercial-scale recycling process of waste plastics using coke ovens is about 25 mm. Nippon Steel Corporation started to operate a waste plastic recycling process using coke ovens at Nagoya and Kimitsu works in 2000 and at Yawata and Muroran works in 2002. Now the total capacity is 120,000 tons per year as of 2003 and this process is operating smoothly.     

炼焦工艺条件对焦炭反应性和反应后强度的影响

通过40 kg焦炉炼焦实验,研究了加热速率、焦饼终温、焖炉时间、入炉煤堆密度及入炉煤细度等对焦炭的CRI(焦炭反应性)、CSR(反应后强度)的影响。结果表明:为保证焦炭成熟和获得较低的CRI值,较高的CSR值,焦饼终温应控制在1000～1050℃范围内。炼焦时焖炉时间应控制在3 h以上。提高入炉煤堆密度,可显著改善焦炭的热性质。入炉煤细度控制在90%左右时,CRI、CSR值较佳。提高加热速率,特别是粘结阶段的升温速率,有利于改善焦炭的热性质。     

鞍钢鲅鱼圈7m焦炉焦炭质量评述

鞍钢鲅鱼圈7m焦炉是国内首座开工建设的大型化焦炉,经过1年多的运行,现焦炉运行稳定,焦炭各项质量指标均达到国内焦化行业的先进水平,其焦炭强度指标很好地满足了4000m,大容积高炉的生产要求。文中详述了7m焦炉投产后配煤的优化管理、改善焦炭质量以及保证干熄焦稳定运行的一系列措施。     

关于捣固炼焦焦饼收缩度的探讨

分析了捣固炼焦与顶装炼焦的焦饼收缩度差异性及其影响因素,探讨了低挥发分配煤在捣固炼焦设计和生产等方面的问题,并提出了下列措施:适当降低加热水平;设定合理的结焦时间;设计可调煤饼宽度的装煤车;根据配合煤Vdaf和X值调整煤饼宽度、高度及采用XD值指导生产,以保证煤饼与炉墙有足够的间隙和适宜的空间温度。     

The strength of industrial cokes. 5. Influence of coke breeze in a coal charge on tensile strength of coke

The purpose of this study was to determine the influence of different proportions and different particle sizes of coke breeze in a coke-oven charge on the tensile strength of the coke. The diametrical-compression test was used to determine the tensile strength of the coke produced in a 10-t test oven and the results obtained were considered in relation to the composition of the oven charge, the coke micum indices and to parameters describing the coke texture. It was established that breeze additions caused measurable but nonsystematic changes in the coke tensile strength and that decreasing the breeze particle size generally increased the coke tensile strength. These changes could not however be directly related to changes observed in the density, porosity, pore-wall thickness or mean pore size of the cokes. The previously established relations between micum indices and the tensile strength of foundry cokes were also found to be inapplicable. The conclusion was drawn that the behaviour described is associated with some, at present unestablished, factor of the blend composition, one possibility being the relative proportions and compatibility of the ‘binder’ and inert material acting through their influence on those aspects of the coke microstructure which control the coke breakage.     

捣固炼焦值得关注的几个问题

叙述了捣同炼焦配煤与焦炭质量的关系及捣固强度与配煤的关联性.指出:焦炭质量的基础是配煤质量,不会因煤准备和炼焦工艺等有根本性的改变;捣固炼焦可多用低变质程度,高挥发分气煤类的炼焦煤生产出一定质量的焦炭;捣同炼焦配煤适当增加黏结性配煤比例可提高焦炭质量,但用接近顶装焦炉的配煤进行捣固炼焦将丧失其优势并引发问题.捣固焦炉的...     

焦炉长结焦时间状态下的管理与维护

在焦炉不能维持正常生产时,一般采用延长结焦时间的方法降低生产能力.介绍了焦炉在长结焦时间状态下,从规范出炉操作入手,做好炉温调控、压力调控、炉体维护等工作.分析了焦炉长结焦时间状态下的控制措施与控制经验,对K均、K安、炼焦耗热量等工艺指标及炭化室高向加热等问题提出了建议.     

Transformations of pyrite during formation of metallurgical coke

The desulfurization of pyrite during the coking process leads to the formation of phases of varying size, shape and composition. The phases are represented mostly by Fe and S-bearing associations, which can be divided into two categories: those represented only by of Fe-S phases (three varieties), and aggregates containing both sulfides and almost pure iron. There are also Fe-O and Fe-S-O phases, which were probably formed after the coke was pushed from the coke oven. It is suggested that the formation of Fe and S-bearing associations can cause the appearance of cracks and cavities in the coke matrix, which, together with the pressure of the released SO₂ gas, will detract from the strength of the coke. Large grains of pyrite can create weaker spots than do smaller ones, and the incomplete decomposition of pyrite will cause migration of the remaining part of the sulfur to the blast furnace, affecting the reactions there. This may be more common in cokes of relatively low porosity and small pore size and in those made from coals with large pyrite grains.     

焦炉自动加热系统的基础研究

本文以焦炉供热平衡为基础，建立了焦炉自动加热前馈供热模型，以期为焦炉加热自动控制提供理论和设计基础。     

中国焦炉的大型化之路

回顾了中国焦炉大型化的发展历史,分析了焦炉大型化的优势,重点介绍了中国目前大型化焦炉的主力炉型JN60型焦炉、7.63m焦炉、JNX70和JNX3-70型焦炉、以及5.5m和6.25m捣固焦炉。并指出了选择炉型时应着重考虑的几个因素。     

The strength of industrial cokes. 6. Further studies of the influence of coke breeze in a coal charge on tensile strength of coke

The objective of this investigation was to ascertain if there was any pattern in the dependence of the tensile strength of coke on the proportion and particle size of coke-breeze in an oven charge and to establish if it was possible to interpret the changes in tensile strength in terms of coke structural features. Using a small-scale oven in order to obtain the optimum in close control of the charge preparation and carbonization conditions, cokes were prepared from each of two coking coals blended with coke breeze. The tensile strength of these cokes was determined by the diametrical-compression test and some details of their porous nature were determined from density measurements, mercury porosimetry and optical microscopy. The results clearly demonstrate that the tensile strength of coke is, in general, systematically reduced with increasing breeze content of the oven charge, the more coarsely ground breeze leading to a greater reduction of the tensile strength at any level of breeze addition. But very finely ground breeze at relatively low levels of addition can lead to an improvement in the tensile strength. These changes correlate with variations in the apparent density and the total porosity and possibly also with the average pore size.     

焦炉加热自动控制系统数学模型的述评

介绍了世界各国焦炉加热自动控制系统中所采用的目标火道温度、结焦终点判定、焦炉供热量、烟道吸力等数学模型。给出了焦炉传热模型获得的数学模型。     

不同炼焦方式对焦炭质量的影响

采用国内有代表性的焦炉进行配煤炼焦试验,探讨不同炼焦方式对焦炭质量的影响,结果表明,捣固、配型煤、配沥青炼焦均能改善焦炭质量。当入炉煤的挥发分较高、黏结性偏低时,焦炭质量改善的效果较为显著;采用捣固炼焦比配型煤、配沥青炼焦更能有效地改善焦炭的反应性和反应后强度。     

炼焦煤质量与焦炉加热制度对焦炭热性质的影响

随着高炉冶炼强度及喷煤比的不断提高,炼铁生产对焦炭质量提出了更高的要求。焦炭的反应性和反应后强度是考核焦炭质量的重要指标,影响焦炭反应性和反应后强度的因素很多,本文根据梅山的生产数据,从炼焦煤的质量和焦炉加热制度2个方面对焦炭反应性及反应后强度的影响进行了分析。