A Comprehensive Review of Characterization Methods for Metallurgical Coke Structures

The structure of coke affects its reactivity and strength, which directly influences its performance in the blast furnace. This review divides coke structures into chemical structure, physical structure, and optical texture according to their relevant characteristics. The focuses of this review are the current characterization methods and research status of the coke structures. The chemical structures (element composition and functional group) can be characterized by elemental analysis, Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy (Raman), X-ray photoelectron spectroscopy (XPS), and nuclear magnetic resonance imaging technology (13C NMR). The physical structures (pore structure and micro-crystallite structure) can be characterized by image method, X-ray CT imaging technique, mercury intrusion method, nitrogen gas adsorption method, X-ray diffraction method (XRD), and high-resolution transmission electron microscopy (HRTEM). The optical textures are usually divided and counted by a polarizing microscope. In the end, this review provides an idea of the construction of a coke molecular structural model, based on the above characterization. With the coke model, the evolution principles of the coke can be calculated and simulated. Hence, the coke performance can be predicted and optimized.

Evaluation of the ecological and geochemical state of surface water in Donbas

The article covers evaluation of the ecological and geochemical state of surface water and bottom sediments in Donbas, as well as their pollution resulting from spatio-temporal changes of natural and anthropogenic factors. It was established that chemogenic pollution occurs due to penetration of polluting elements into surface water as a result of filtration leaks from sedimentation tanks and water discharges made by enterprises of coal, chemical, metallurgical, coke-chemical and petrochemical industries. Increased concentrations of biogenic elements (mineral forms of nitrogen and iron) were recorded in the water of the Siverskyi Donets and the Luhan Rivers. The most significant deterioration of groundwater quality because of high content of sulfates and chlorides is observed within the watersheds of the Luhan River's valley. Measurement results of the metals content indicated an increased content of copper and manganese. Some values even exceed the average annual concentrations specified by the existing normative values. In general, the results of the pollutants content analysis in the river basins under study did not reveal significant changes in the content of heavy metals during the period of military actions as compared to the results of government monitoring by 2014. The obtained experimental data indicate that vanadium, chromium and copper dominate in bottom sediments of all the studied objects. The greatest accumulation of heavy metals is observed in the Bakhmutka River and the Kryvyi Torets River. The research established that copper and plumbum in the bottom sediment samples taken from the Kryvyi Torets exceed the background values by 4-5 times. Zinc and vanadium exceed the background content values by 10 and 4 times, respectively. The same indicators are slightly lower in the Volyntsevske Reservoir and this fact is associated with more intense processes of water exchange and certain peculiarities of bottom sediments granulometric composition. Concentration of zinc is 3 times as much as the background level, vanadium and manganese – twice as much. Heavy metals in the bottom sediments of the studied water bodies are characterized by uneven distribution. Vanadium and copper dominate in the content of bottom sediments. Concentrations of zinc, vanadium and nickel at certain objects also exceed their regional background content values. Titanium was detected in minimum quantities.

Particle Size Distribution Models for Metallurgical Coke Grinding Products

Six different particle size distribution (Gates–Gaudin–Schuhmann (GGS), Rosin–Rammler (RR), Lognormal, Normal, Gamma, and Swebrec) models were compared under different metallurgical coke grinding conditions (ball size and grinding time). Adjusted R2, Akaike information criterion (AIC), and the root mean of square error (RMSE) were employed as comparison criteria. Swebrec and RR presented superior comparison criteria with the higher goodness-of-fit and the lower AIC and RMSE, containing the minimum variance values among data. The worst model fitting was GGS, with the poorest comparison criteria and a wider results variation. The undulation Swebrec parameter was ball size and grinding time-dependent, considering greater b values (b > 3) at longer grinding times. The RR α parameter does not exhibit a defined tendency related to grinding conditions, while the k parameter presents smaller values at longer grinding times. Both models depend on metallurgical coke grinding conditions and are hence an indication of the grinding behaviour. Finally, oversize and ultrafine particles are found with ball sizes of 4.0 cm according to grinding time. The ball size of 2.54 cm shows slight changes in particle median diameter over time, while 3.0 cm ball size requires more grinding time to reduce metallurgical coke particles.

Elaboration of indices complex and additional criterion of coals and charges quality evaluation for production and prediction of required and high quality coke

Coal raw material base of coking is the main factor characterizing the quality of coke. Therefore, it is very important to know technological properties and peculiarities of coals behavior in a charge during coking process for coals charge batching and coke quality control. One of the priority directions in study coals and charges is petrographic and reflectogram analysis, which enable to obtain data related to evaluation genuine (one-valued) technological properties of coals, coal blends and charges at production of coke of required quality. Using a broad material of study, including the one carried out by the authors of the article, a wide range of application of reflectogram analysis of coals, coals blends and charges in the coking production was shown. It was demonstrated also that application of the analysis enabled to exclude the problem of “twins”, to define the degree of genetic coals recoverability and coals grades or types relation in the mixtures for the coking. Based on the elaborated by the authors reflectogram criteria of charges for coking, a strategy of coals batching was proposed, which ensures production of metallurgical coke of required and high quality and safe running of coke ovens. Based on wide experimental studies of plastic-tough properties of coal charges, porosity of coke, its X-ray structure characteristics, strength and reaction ability, theoretical ideas were formed about mechanism of interaction in a charge of petrographically nonuniform coals comprising it during coking process, by using the proposed by the authors indices of coals nonuniformity. The indices of coals, comprising the charge, nonuniformity, differ by metamorphism degree (σR) and petrographic composition (σСК), explaining regularities of forming of quality of coke from the charge with participation of petrographically nonuniform coals. The package of the factors noted by the authors, revealed in the process of the study of coals, coals blends and charges, as well as quality of coke obtained from them, enabled to elaborate a complex index of charges coking ability (К.п.к.Vo), which enables to considerably simplify the mathematical model of coke quality prediction and to increase its reliability. Mathematical models of coke quality prediction were verified and implemented at several plants of Russia.