A project report submitted to the Faculty of Engineering and the Built Environment,
University of the Witwatersrand, in partial fulfilment of the requirements for the degree
of Masters of Science in Engineering.
Predicting coke quality based on coal petrography, rheorogy and coke petrography
For most of the 20th century optical petrography has been the primary petrological and mineralogical tool used to characterize coal. The development of quantitative SEM-based techniques, e.g. QEMSCAN®, for coal began only about a decade ago. The application of these techniques for coal lagged behind other commodities, but they are currently being developed with the aim to provide ‘one complete analysis’ for coal. Quantitative SEM-based techniques are supplemented by quantitative X-ray diffraction (XRD). Recent indications are that these more modern techniques cannot replace the ‘standard’ petrographic and chemical evaluations, but rather complement them where and when required. The great advantage of quantitative SEM-based techniques is that they are very rapid, with the result that large volumes of samples can be processed on a routine basis. This is ideal for coal type identification, since theresults can be used in the creation of ‘intelligent’ composites. This can lead to the more speedy evaluation of coal deposits by reducing the number of samples on which detailed metallurgical and characterization test work is required, without an increase in the overall statistical error of the resource model. Coal petrography, however, remains important for the prediction of the coking characteristics of certain coals and coal products. As a consequence it is therefore important that any coal laboratory be able to produce data with confidence. This requires strict quality control and assurance protocols that adhere to international standards.
The world, and especially European iron and steel producers, need a paradigm change to be prepared for the future, to comply with environmental regulations, specifically on carbon footprint reduction, and to cope with raw material availabilities and final product qualities. There is a trend in the steelmaking industry, as part of the decarbonization of Europe’s economy and the perceived future for other countries worldwide, towards hydrogen (H2)-based iron reduction as a long-term substitute for carbon-based processes.
by F. Muscolino, A. Martinis, M. Ghiglione, P. Duarte
The gas-based direct reduction technology is the process used to convert iron ore, either in the formof pellets or lumps, into metallic iron by means of reducing gases and without the need of melting.
This technology was born in the early 50s in Mexico and has experienced increasing popularity due to the properties of the final product, commonly called Direct Reduced Iron (DRI), as virgin source for high quality steel production through electrical steelmaking, as an alternative to low residual scrap.
In addition, the reduced environmental footprint compared to the traditional integrated route (blast furnace coupled with basic oxygen furnace) makes the direct reduction the most promising alternative for iron production in countries where very restrictive regulations on emissions are applied, with, for example, the possibility to capture and commercialize the CO2
as by-product. The use of DRI can be also effective in decreasing emissions in existing plants.
Its addition directly in the BF/BOF burden allows to increase productivity
and to decrease emissions by reducing significantly coke and sinter consumption.
Latest installations of new direct reduction plants are returning remarkable results in term
of product quality and integration with steelmaking.
Research and development of new cokemaking process (SCOPE21) was conducted in Japan from 1994 to 2003 by the Japan Iron and Steel Federation (JISF). Pilot plant scale test of SCOPE21 process was conducted successfully and targets of the project were confirmed. SCOPE21-type new coke oven battery was constructed at Nippon Steel Oita works and the operation of new coke plant started in 2008. The coke production capacity is 1 million ton per year. At present, high quality coke has been produced in this process using high blending ratio (over 50%) of non- or slightly-caking coal.
The progression of fluidity loss due to oxidation emerges as a coal property that correlates with the CSR loss of the coke from weathered coal. Coal transportation and storage must be carried out under low relative humidity levels (< 20 %) to avoid coke quality deterioration. The by-products plant operation will be affected by the lower tar yield per tonne of coal and the higher phenol content of the tar when carbonising oxidised coals. The coke yield will be reduced when using coals oxidized at high temperatures (50°C) and under high relative humidity levels (90 %). Weathering usually… reduces coking pressure but in some cases coking pressure increases due to the faster drop in fluidity than in dilatation. The alternative stain and abrasion drum tests can determine the extent of coal oxidation but the stain test is not quantitative and the abrasion drum test is rather time-consuming. Pristine high fluidity coal can be added to weathered high rank coal to produce a blend with optimum fluidity. Blending oxidised low and high rank coals also improve the cold mechanical strength of the coke. Mild oxidation of low/medium rank coals improve coke quality and reduce the fluidity to optimum levels. Coal tar improves the JIS index of oxidised coals but impairs the CSR of high rank coals. Crushing and pre-heating of weathered coals cannot recover the coking properties. Higher bulk density of weathered coals leads to better coke quality but coking pressure also increases at high bulk densities.
EXTERNAL AUDIT REPORT IN FULLFILLMENT OF THE ENVIRONMENTAL AUTHORISATION FOR THE COKE OVEN CLEAN GAS AND WATER PROJECT
Report date: 11th March 2015
Zantow Environmental Consulting Services was contracted by ArcelorMittal to conduct an independent Compliance Audit. The methodology followed for conducting the compliance assessment audit is detailed described and also conclusion and recomandations.