Prediction of carbonisation time in byproduct recovery coke ovens through gooseneck temperature measurement

Precise prediction of the end of carbonisation possesses intangible benefits in the coke making process. The coke ovens in Tata Steel measure the raw gas temperature (at the gooseneck arrangement in the oven top) to identify the end of coking. Based on the gooseneck temperature profile, the carbonisation time is divided into active carbonisation time (ACT) and soaking time. As the soaking time is varied between 45?min and 1.5?h as per the need, the current study focusses on developing a mathematical model to predict the ACT given the coal blend properties and the operating conditions of the oven. Different statistical methods ranging from linear regression to artificial neural network (ANN) have been used to arrive at a robust model. Piece-wise linear regression and ANN have been found to out-perform the other statistical techniques. However, the ANN model is preferred in terms of the predictability of unseen data.     

Coal pyrolysis and kinetic model for non-recovery coke ovens

Abstract

In heat recovery non-recovery coke ovens, the volatile gases generated are burnt, and the heat generated is used for cokemaking. The extra heat, along with the flue gases, is utilised in boilers for power generation. JSW Steel has 1·2 Mtpa non-recovery coke ovens to meet the coke requirement of blast furnaces. Until now, very limited work has been carried out on heat distribution in non-recovery coke ovens. In this work, the heat distribution in non-recovery coke ovens is studied to determine the variables influencing the flue gas temperature and thereby power generation. A mathematical model has been developed to predict the power generation using functional group, depolymerisation, vaporisation and cross-linking for non-recovery coke ovens at JSW Steel. Gas generation, heat generation, power generation and total heat distribution are calculated using the model. The present paper details the study on heat distribution, thereby various factors affecting the power generation, and also quantifies the effect of coal quality in particular volatile matter on gas generation, flue gas temperature and power generation.     

Pilot scale simulation of cokemaking in integrated steelworks

Abstract

Pilot scale coke ovens are widely used to produce coke samples for characterisation and also to assess the coking behaviour of coal blends. The Newcastle Technology Centre of BHP Billiton has built a sophisticated 400 kg oven, which can produce cokes under a range of carefully controlled bulk densities and heating rates. A freely movable heating wall allows the thrust generated at this wall at the different stages of coking oven to be determined. This paper describes comparative work carried out to determine a laboratory stabilisation technique for laboratory cokes. The strength of stabilised cokes are characterised using a number of tumble tests, and correlations between different drum sizes are also given since a major constraint in laboratory testing is the limitation in the mass of sample available. Typical oven wall pressure results, and results obtained from embedded temperature and pressure probes in the charge during coking, are also presented.     

加废塑料配煤炼焦的产品产率和性能研究

在炼焦配合煤中添加一定的废塑料，利用自制的小焦炉炼焦，对所得的焦炭和焦油产率、焦炭粒度、焦炭Ⅰ转鼓强度和焦炭灰分等进行了分析。实验表明，在炼焦配煤中添加适当的废塑料可以使焦油产率、焦炭产率、焦炭强度和焦炭粒度等有不同程度的提高。     

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:     

Use of resin-bearing wastes from coke and coal chemicals production at the Novokuznetsk Metallurgical Combine

The coke and coal chemicals plant at the Novokuznetsk Metallurgical Combine is making trial use of a technology that recycles waste products in “tar ponds.” Specialists from the ékomash company have installed a recycling unit in one area of the plant’s dump, the unit including an inclined conveyor with a steam heater and a receiving hopper. The coal preparation shop receives the wastes in a heated bin, where a screw mixes the wastes with part of the charge for the coking ovens. The mixture subsequently travels along a moving conveyor belt together with the rest of the charge materials. The addition of up to 2% resin-bearing waste materials to the coal charge has not had any significant effect on the strength properties of the coke. __________ Translated from Metallurg, No. 4, pp. 49–50, April, 2007.     

Recycling Waste Plastics in EAF Steelmaking: Carbon/Slag Interactions of HDPE‐Coke Blends

Due to the inherent limitations of current methods of plastic waste disposal, there have been concerted efforts worldwide towards developing alternative, environment friendly and economic recycling processes. With an aim to recycle waste plastics in EAF steelmaking, carbon/slag interactions for a number of blends made of metallurgical coke and HDPE (high density polyethylene) and an EAF slag (34.8 mass‐% Fe₂O₃) have been investigated at 1550°C using a sessile drop arrangement. The rate of gas generation showed an increase with increasing HDPE concentration, reaching a maximum for blend #3 (with appr. 30 % HDPE) and decreasing thereafter. Among all the blends investigated, blend #3 showed significantly higher levels of slag foaming as compared to metallurgical coke. HDPE‐coke blends also showed better wetting compared to metallurgical coke with contact angles in some cases improving from 140° to 70° after 10 minutes of contact. These results have been discussed in terms of ash and sulphur contents of carbonaceous residues and dynamic changes in slag composition. Industrial trials on blend #3 showed a good agreement with laboratory results. This work opens novel avenues for the utilisation of plastics wastes as a valuable carbon resource in EAF steelmaking.     

20 kg焦炉废塑料配煤炼焦的研究

在炼焦煤中配入一定量的废塑料，利用20kg焦炉进行炼焦实验，分析所得焦炭的产率、冷态和热态强度。实验结果表明，其焦炭的产率均比未加废塑料的要高（除添加0．5％聚乙烯（PE）外）；焦炭的抗碎强度（M30）整体呈下降趋势，耐磨性强度（M10）整体降低；焦炭的反应性（CRD出现整体升高趋势，相应的反应后强度（CSR）呈整体降低趋势。     

“十二五”我国焦化工业的发展

"十一五"我国焦化行业快速发展,但也面临着前所未有的严峻形势。我国与国外焦化发达国家还存在差距:大型焦炉比例低;采用节能减排技术措施少;产能结构性过剩,行业集中度偏低等,是中国焦化工业发展的瓶颈。为使我国从焦炭生产大国变成焦化技术强国,"十二五"应该开发和推广低NOX排放的大型顶装焦炉、大型捣固炼焦、干熄焦、焦炉烟道气余热回收利用、高效节能的脱硫脱氰技术;研发焦炉荒煤气余热回收利用、焦炉煤气综合利用和新型焦化污水深度处理技术;建设和发展大型煤焦油加工和大型苯加氢装置。     

Combustion control system for coke ovens embedded with auto positioning systems

A good grade coke produces highest thermal energy and it is highly efficient in hot metal reduction. In order to concentrate the carbon in coke, the coke making process involves carbonisation of coal to high temperature (1100°C) in an oxygen-free atmosphere. There is always a need to efficiently automate the coke oven operations as much as possible. In order to improve the level of control and management of coke oven, the research on intelligent control system is carried out. In modern advanced control system of coke oven, the control scheme of combination of feedback and feed-forward merged with management is widely utilised. The integrated management and control system of coke oven is introduced systematically, including the production plan and scheduling management (dynamic scheduling) and heating control system (mathematical modelling) i.e. evaluating battery temperature, intelligent combustion control system and the pressure control of gas collector of coke oven battery.     

废塑料配煤炼焦试验

在炼焦煤中配入一定量的废塑料,利用20kg试验焦炉做炼焦试验,对所得焦炭产率、冷态和热态强度进行了分析。试验表明：除添加0．5％聚乙烯（PE）炼焦未使焦炭产率增加外,添加废塑料后,焦炭的产率均比未加废塑料的高;添加废塑料后焦炭的抗碎强度（M40）整体出现下降趋势．耐磨强度（M10）整体也是降低的;添加废塑料后焦炭的反应性（CRI）整体出现升高趋势,相应的反应后强度（CSR）成整体降低趋势。     

焦炉能耗分析与余热利用技术

焦化产业作为高能耗、高污染产业,具有巨大的节能减排潜力。以焦炉物料平衡和热平衡计算为基础,计算焦炉的热效率,对焦炉的能耗进行分析。采用回收焦炭显热的干熄焦技术、荒煤气余热利用技术和以焦炉废气余热为热源的煤调湿技术,以充分利用焦炉支出热,达到节约能源、改善环境、提高经济效益、降低炼焦耗热量和提高焦炉生产能力的目的。     

Utilisation of low-grade raw materials for preparation of reactive catalysed-coke for blast furnace application

In this work, a method for producing highly reactive catalysed coke from medium and non-coking coal using low-grade iron ore fines as a catalyst through two different alternate routes, namely carbonisation in a stamp charge coke oven and carbonisation in a horizontal tube furnace was attempted. Phenolic resin and petroleum pitch were individually experimented as a binding material to get adequate strength. Effect of process parameters such as coal-to-iron ratio, briquetting load, binder quantity and coking to non-coking coal ratio on the coke properties such as reactivity and mechanical strength was investigated. The SEM and petrography analysis of catalysed coke were used to study the microstructure and its effects on reactivity.     

Recycling Rubber Tyres and Waste Plastics in EAF Steelmaking

Electric Arc Furnace (EAF) steelmaking uses different carbon based materials as foaming agents. Depending on cost and availability, anthracite and metallurgical coke are among the conventional injecting materials. Considering the energy and green house gas emissions requirements, alternative carbon sources are put on the spot to replace, at least partially, the conventional materials, i.e. waste materials such as rubber and high density polyethylene (HDPE) plastics may react with gas and slag phases resulting in devolatilization, combustion and iron oxide reduction reactions. The addition of waste tyres and waste plastics in EAF steelmaking has been studied in detail by our groups at UNSW and OneSteel is developing a method for EAFs to use blends of different proportions of rubber/HDPE plastics and coke as a slag foaming agent. Initially, laboratory investigations were carried out to establish the feasibility of carbon and polymer blends as foaming agents. The enhanced slag foaming performance compared to coke was found to be in good accordance with the results obtained in the laboratory indicating an increased slag volume when using polymeric blends. Following the successful installation of materials handling systems at both plants, the use of a rubber and coke blend is no longer considered a trial and is instead standard practice.     

炼铁过程使用木炭和生物质以及废塑料减少CO2的排放

根据实验室研究,提出了两种可应用于钢铁行业降低CO2排放的方法:利用可再生的生物质或木炭以及利用可回收的含氢废旧塑料。该方法可通过以下两个途径实现:①风口喷吹;②混入入炉炉料,例如:通过混入炼焦煤而进入焦炭,在生产用于高炉或直接还原的球团原料中添加含碳原料和塑料。为考察现代高炉风口喷吹木炭的益处,重点研究了木炭在风口回旋区的气化行为和在风口回旋区外的二次反应。采用实验室装置及其相应的检测设备,研究了几种木头在不同炭化条件下所得到的木炭的转化效率。研究结果表明,对于风口喷吹,所测试木炭的燃烧行为都不逊于矿物质煤;在模拟的高炉炉身条件下,木炭的熔损反应速率高于试验所用的矿物质煤。使用塔姆曼炉试验装置及检测仪研究了可用于直接还原和高炉的冷固结含碳、废塑料和木炭球团的还原和体积变化行为。使用该种球团可抑制和减小还原膨胀,甚至出现体积收缩。球团的自还原行为受还原气的量、气氛和操作条件的影响。采用电阻炉进一步研究了固结废塑料(聚乙烯和垃圾衍生燃料)的氧化铁的还原行为。     

Desulphurisation of high sulphur coal to improve industrial utilisation

Abstract

Coal from northeastern India is considered to be a very good quality coking coal owing to its low ash content (<8%). It has an excellent caking property, and after carbonisation it can provide a very good CSR (coke strength, after reaction with CO₂). On the other hand, its metallurgical application is not so encouraging as a result of its high sulphur content (3-7%). Normally the acceptable sulphur content in metallurgical coke is 0·7% maximum. About 90% of the sulphur is present in organic form, and the remaining 10% as pyrites and sulphates. Removal of sulphur from the organic types is somewhat complicated as it cannot be done by any physical process such as benificiation or flotation, whereas sulphur in pyrites and sulphates can be removed by physical means. With a view to lowering the sulphur content of the coal, desulphurisation studies were carried out at elevated temperatures ranging from 400 to 950°C under the flow of various reducing gases such as coke oven gas, water gas, steam and pure hydrogen. The retention time at each temperature of experimentation was usually varied at 15, 30 and 45 min. It was observed that the sulphur content in the coal was decreased in every experiment with the various reducing gases. The extent of sulphur removal in treatment of the coal with coke oven gas was up to 78·1%, that with steam 83·1% and that with water gas 85·7%. The minimum sulphur content found in desulphurised coal was 0·86%, which could not be used for metallurgical purposes unblended. In the case of experiments with steam, a severe loss of carbon (15-20%) was observed because of reaction with the steam, whereas no such losses were observed in experiments with the other two reducing gases. Hydrogen lowered the sulphur content at a faster rate in comparison with the other gases, but could not increase the degree of reduction. The present study may help to establish the technoeconomic feasibility of the processes; however, large scale experimental studies are required for confirmation. I&S/1721     

煤与废塑料共焦化试验研究

对单种煤与废塑料共焦化过程的配合性进行研究。首先进行了煤与PE、PP、PET、PS和脱氯PVC 5种塑料混合物热解过程的热重分析,在此基础上完成了煤与上述5种废塑料的20 kg试验焦炉的共焦化试验,考察了不同种类废塑料对焦炭冷、热强度的影响。研究结果表明:煤和不同种类废塑料发生热解反应的温度区间及热解失重速率的温度分布曲线对共焦化后的焦炭强度有直接影响,表现为煤阶较高的烟煤与废塑料共焦化后焦炭强度下降,5种废塑料中PS和PET与煤在共焦化过程中的配合效果不如其他3种废塑料。     

焦炭市场形势分析

根据国内外焦炭的生产情况，分析了焦炭市场形势，指出虽然目前焦炭市场趋于紧张，炼焦能力和炼焦煤供应蠢足不了国内焦炭量需求，但不要盲目地建设大批低水平的焦炉。要冷静地看待国内外焦炭市场鬃俏的形势，建设焦炉时应注意考虑与钢铁厂的配套、原材料的供应、产品的销售、焦炉煤气的充分利用以及环保等问题，建设一批大型的符合环保要求的焦炉是需要的，但目前在建的焦炉比较多，可以预测，过一段时间由于市场竞争要关掉一批焦炉。     

废塑料与煤粉热解特性的研究

分别将4种废塑料和煤粉置于非氧化性气氛中研究其热解特性。研究结果表明,在氮气中废塑料的裂解过程主要分为三个阶段:缓慢裂解—急速裂解—缓慢裂解至结束,煤粉的裂解过程比较平缓;最大裂解速度对应的温度,废塑料平均超过400℃,煤粉为900℃;终了裂解量,不同品种废塑料为85%～100%,而煤粉仅22%,两者差异极大;废塑料的完全裂解表观活化能是煤粉的6～10倍。     

利用焦化工艺处理废塑料试验研究

利用200kg焦炉试验,研究利用焦化工艺处理废塑料的产物特性。研究结果表明：2％添加剂能够部分消除添加废塑料对焦炭质量的负面影响,对焦炭耐磨强度的改善作用明显,对抗碎强度、反应性和反应后强度的改善作用在废塑料添加配比达到4％时基本消失;此外,废塑料、添加剂与首钢炼焦配煤按比例1：2：97混合共焦化能够显提高冶金焦炭和焦油的质量,提高焦炉煤气的热值,具有显的工业应用前景。