Forecasting of industrial coke quality at JSC EVRAZ NTMK based on data of passive industrial experiment. Report 1. Forecasting of CSR and CRI of industrial coke

A forecast of coke quality takes a special place in the coke production, since it enables to increase efficiency of management of batching process of various by composition and properties coals and production of coke of stably high and required quality with minimal costs. Description of a methodological approach to processing of passive industrial experiment data of blends coking at Coke production department of JSC EVRAZ NTMK presented by application selective (general) matrix. The matrix accounts various multilevel values of influence factor CSR and CRI of coke - a complex index of coking ability of blends K.п.к.Vo. It was shown that the proposed approach provides wide variations of response function (CSR/CRI) at symmetrical enough matrix, excluding predominance of any particular area of values of indices K.п.к.Vo and CSR/CRI. By applying the passive industrial experiment, based on processing of actual report data of industrial blends coking at the coke batteries No. 5-6 (wet quenching) and No. 9-10 (dry quenching) by selective matrix, mathematical models of forecast of quality of industrial coke by wet and dry quenching (CSR/CRI) were elaborated depending on coal charges properties (K.п.к.Vo) at the existing modes of their preparation and coking at the coke batteries No. 5-6 and 9-10. Verification of accuracy of the mathematical models of coke quality forecast at wet and dry quenching (CSR/CRI) processing a large actual material of industrial coking (62 coking operations in the coke batteries No. 5-6 and 58 coking operations in the coke batteries No. 9-10 showed accuracy good enough for practical application of forecasting indices CSR and CRI of industrial coke of wet and dry quenching.

A mathematical model of relation and origin of variation between CRI and CSR indexes

The aim of this work is both the mathematical relation and the value variation analysis between CRI and CSR indexes. For this aim the physical mathematical model is proposed on the basis of the ISO-test. The physical basis of the model is a material balance of a one piece of coke from the ISO sample. Results of calculating by the model are curves of CSR=f(CRI) which reproduces the regressions in analogy with CSR=a+b.CRI for most coke-producing countries. The model showed that a larger part of CSR=f(CRI) curve is linear and that a universal regression in analogy with CSR=a+b.CRI does not exist. As follows from the model, every piece of coke from the ISO sample has its own CSR=f(CRI) curve with a CRI and CSR point. Between pieces of coke, variations of CRI and CSR values can be explained by the open pore amount, the coke pores’ surface area, the statistical distribution of molecular oriented domains on the basis of Lc and the coke piece mass. In our results, pores with a geometrical orientation from the outside to the center of a coke piece and having a minimum length significantly influence on the coke quality according to CRI and CSR indexes.

The Concept of Optimal Compaction of the Charge in the Gravitation System Using the Grains Triangle for Cokemaking Process

Two isomorphic sets of grains, small and large, were analysed—without specifying their dimensions—under the acronym CMC (Curve of Maximum Compression) and taking into account the effects of segregation CMCS. The proposal is particularly valuable for optimal blend preparation in the gravity system in cokemaking. The main advantage of this work is the proposal of using the grains triangle, which limits the values calculated by the relations: bulk density-share of coarse/fine grains, for different levels of moisture content. Each system of changing shares of coarse grains is characterised by a constant C, but there is no need to determine it. Compliance of the calculated value with the experimentally determined value means that the given arbitrary grain set has reached its maximum density called the “locus”. The grains triangle practically covers the vast majority of laboratory and industrial test results, and geometrically or computationally indicates the ability of a given particle size distribution to reach maximum bulk density. This paper presents analysis of the results of tests on crushing, coal briquettes, and grinding coal blend in selected mechanical systems. Results of tests on coke quality (CRI, CSR) in connection with the grain size triangle are discussed.

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.

Stamp-Charged Coke-Making Technology—The Effect of Charge Density and the Addition of Semi-Soft Coals on the Structural, Textural and Quality Parameters of Coke

Coke is an integral component of the blast furnace charge; therefore, it plays an important role in the integrated steelmaking process. Achieving the required coke quality parameters by producers requires the use of a high proportion of the highest quality coking coals (hard coking coals) in the coking blends, which significantly increases the unit production costs. Approximately 75% of these costs are constituted by the cost of the coal blend’s preparation. There is a deficit in the best quality coking coals on the world market and their supply are characterized by large fluctuations in quality parameters. Therefore, from the point of view of the economics of coke production, it is advantageous to produce high-quality coke from a coke blend with the highest possible content of cheaper coals. The paper presents the results of the influence of coal charge bulk density and semi-soft coking coal content in the coking blend on the textural and structural parameters of coke, which determine its quality. Research has shown that the application of increased density influences the parameters of the texture and structure of the coke, which shape its quality parameters. The use of stamp-charging technology contributes to the improvement of the coke quality or enables the production of coke of a predetermined quality from blends containing cheaper semi-soft coals.

A comprehensive investigation of the reaction behaviorial features of coke with different CRIs in the simulated cohesive zone of a blast furnace

The reaction characteristics and mechanism of coke with different coke reactivity indices (CRIs) in the high-temperature zone of a blast furnace should be fully understood to correctly evaluate the coke quality and optimize ironmaking. In this work, low-CRI coke (coke A) and high-CRI coke (coke B) were charged into a thermogravimetric analyzer to separately study their microstructural changes, gasification characteristics, and reaction mechanism under simulated cohesive zone conditions in a blast furnace. The results show that both coke A and coke B underwent pyrolysis, polycondensation, and graphitization during the heat treatment. The pyrolysis, polycondensation, gasification speed, and dissolution speed rates of coke B were higher than those of coke A. Direct and indirect reduction between sinter and coke occurred in the cohesive zone and had different stages. The consumption rate of coke B was faster than that of coke A during the coke–sinter reduction. The carbon molecules of coke A must absorb more energy to break away from the skeleton than those of coke B.

Effects of Boron Carbide on Coking Behavior and Chemical Structure of High Volatile Coking Coal during Carbonization

Modified cokes with improved resistance to CO2 reaction were produced from a high volatile coking coal (HVC) and different concentrations of boron carbide (B4C) in a laboratory scale coking furnace. This paper focuses on modification mechanism about the influence of B4C on coking behavior and chemical structure during HVC carbonization. The former was studied by using a thermo-gravimetric analyzer. For the latter, four semi-cokes prepared from carbonization tests for HVC with or without B4C at 450 °C and 750 °C, respectively, were analyzed by using Fourier transform infrared spectrum and high-resolution transmission electron microscopy technologies. It was found that B4C will retard extensive condensation and crosslinking reactions by reducing the amount of active oxygen obtained from thermally produced free radicals and increase secondary cracking reactions, resulting in increasing size of aromatic layer and anisotropic degree in coke structure, which eventually improves the coke quality.