H. P. Tiwari

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 metalurgical coke through non Grecovery 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 diferent types of coals was a major chalenge for coke makers. Coal blend selection criterion based on a single coeficient, named as composite coking potential (CCP), was develG oped. The use of increased proportion of semisoft coal (crucible sweling 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 nonGrecovery 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 M40 value was between 81.8 and 89.3 in both the cases.

A review of coke making by-products

Existing energy resources are struggling to cope with the current energy requirements. It is therefore, necessary to increase energy efficiency and reduce greenhouse gases emissions in integrated steel industries. The yield of coking by-products is one of the key ways to achieve these goals. This review article is focused on history of the by-products such as coal tar, coal tar pitch, ammonia, hydrogen sulphide, pyridine, hydrogen cynide and carbon based material. Different technology for removal of mentioned by-products are briefly described according to technology development at different stage. Yield and quality of coking byproducts, its impacts on carbonization processes and factors such as volatile matter, rank of coal, reactive macerals, elemental constituents, and temperature were also investigated.

Effect of Heating Rate on Coke Quality and Productivity in Nonrecovery Coke Making

The productivity and coke quality of a nonrecovery oven depends on coal blend, operating parameters, and heating rate. A numerical methodology has been proposed for predicting temperatures of the intermediate points with the help of measured temperature in the coke oven. The model was validated with an actual temperature profile of five industrial ovens. The developed model can predict the temperature profile of the oven for a given set of operating conditions. The heating rate under normal operation was found to be in the range of 0.64–1.17°C/min. The effect of temperature variation inside the oven was also correlated with the coke quality and productivity.

A comparative study of by-products yield from coke making processes in a Jenkner apparatus

Physico-chemical characteristics or the industrial behaviour of any coal is directly controlled by its organic micro-components (macerals). The yields of by-products during carbonization of coal are affected by organo micro-components of different coals and operating parameters, such as, charging technologies, carbonization temperature, particle size, bulk density, etc. In the present investigation, the effects of volatile matters (16.61–36.00%), Ro, avg. (0.80–1.36%), exinite (0.5–4.5%), hydrogen (4.34–5.29%) and nitrogen (1.60–2.18%) content of coal on yield of by-products, such as, coke oven gas, coal tar, ammonia, and hydrogen sulphide were studied. The studies revealed that there is a significant difference of the yield of by-products for the two different charging technologies. The coke oven gas, coal tar and ammonia yield was lower in stamp charging process as compared to top charging process, whereas, hydrogen sulphide yield followed a reverse trend.

An approach to maximize the use of non-coking coal in non-recovery coke making

The preservation of metallurgical coal and coke cost reduction are gaining much importance in iron and steel industry. The effort is being made worldwide to increase the use of inferior grade coking coal/non-coking coal in coke making. The objective of this study was to maximize the use of non-coking coal in the coal blend without deteriorating the coke quality in non-recovery coke oven. The selection criterion of coal/coal blend was based on a coefficient, named as composite coking potential model. The study confirms the existence of a relationship between the composite coking potential and the hot strength of coke. The study reveals that upto 35% non-coking coal in coal blend is possible to produce desired quality of coke with coke CSR ≥ 65.

Producing high coke strength after reactivity in stamp charged coke making

In recent years, blast furnaces of larger volume have come into use and the requirements for coke strength have become increasingly severe. The dissections of Nippon Steel Corporation blast furnaces have revealed considerable changes in coke properties in the lower furnace regions. With increased use of Pulverized Coal Injection, improved hot coke strength will be required for efficient and consistent performance in the furnace. The present study revealed that the CSR of coke produced by stamped charged coke making process is mainly influenced by the properties of coal like petrography, coal ash chemistry and rheology. In stamp charging condition, to produce coke with high CSR value, it is necessary to select coals with appropriate ash chemistry, petrographic properties and rheological properties must be maintained. The coal blends which improve the coke CSR beyond a certain limit generate high oven wall pressure. The investigation results show that for producing greater than seventy CSR, coal basicity, fluidity temperature range and inertinite value must be less than 0.2, minimum 90°C and 32 volume % respectively.

Heat recovery stamp charged coke making: An experience in operational excellence

The coal blend quality and process control of coke making technologies is an important lever to produce quality coke with optimal cost. Apart from impacting cost, this improves the CO2 footprint. This is facilitated by proper selection of coke making technologies and coal/coal blend. Each technology has its own advantage and limitation based on its design criteria. Recently, Tata Steel introduced Asia largest single location 1.6 mtpa of heat recovery coke plant for the first time. This paper briefly described the operational philosophy evolved in heat recovery coke plant to produce desired quality coke at comparatively lower cost through operational excellence. The reduction of imported prime hard coking coal in coal blend up to 30% without affecting coke quality adversly and understanding the operational processes and finally mastering heat recovery coke making technology was also part of this paper.

Effects of binder on recovery stamp charged coke making process

The optimum stability of coal cake is essential for producing good quality of coke in stamp charged coke making process. A suitable binder named as ‘X7’ was identified to improve the stability of coal cake, oven throughput, coke quality and reduce specific energy consumption for stamp charged coke making process. Laboratory results show that addition of ‘X7’ in coal blend up to 0.10–0.50 percentage, improved the mechanical strength of coal cake by 3.0–5.0 percentage. Six hundred kg pilot plant trials show that addition of binder in the base coal blend improved coke quality in terms of CSR, M40 and AMS significantly. Coke plant trials also show that ‘X7’ addition (0.10%) in base coal blend improved coke quality in terms of CSR (1.25 point), M40 (0.9 point) and AMS (1.70 mm). Addition of ‘X7’ increased Coke End Temperature up to 24°C during plant trials. The increased in temperature saved energy approximately 11 000 Gcal and reduce CO2 emission by at least 10 000 T/Annum.

Industrial perspective of the cokemaking technologies

Abstract The operational efficiency of a coke plant depends on three vital aspects: first, the produced coke should meet the quality standards required for the use of modern blast furnaces; second, the environmental consideration; and third, the cost of the coke. This has become progressively important due to the cost competitiveness of the iron and steel industry, which has become the key to survival. Therefore, the production of coke with optimal cost by adequate selection of cokemaking technology and the optimization of coal blend cost and operating parameters are the most important tasks for cokemakers. This chapter describes an overview of cokemaking technologies, fundamental aspects of carbonization, coal-blending practice in cokemaking with practical experience, and the influence of operating parameters and environmental regulations. A brief review of conventional by-product coke ovens is also part of this chapter.

Potential Use of High Ash Indian Medium Coking Coal in Stamp Charged Coke Making

ABSTRACT To produce low-cost hot metal, Tata Steel always had to deal with trilemma, that is, cost-quality-mining life to achieve maximum benefit in the steel business. Tata Steel used approximately 50–60% Indian medium captive coking coal having 15–16% clean coal ash in the stamp charged coal blend. Keeping in view, consumption, and preservation of the Indian medium coking coal by modulating clean coal ash without deteriorating the coke quality was the subject of the study. The study revealed that 55% captive Indian medium coking coal up to 19.10% clean coal ash in coal blend could be used to produce coke CSR ≥65. It also reduces the coal blend cost with added benefits of the increase in the captive mine life. This paper described in detail, the effect of variation of ash percentage of captive medium coking coal in the blend on the lateral expansion and hot strength of coke especially of coke CSR.