Post-reaction Strength Research Articles

ПИТОМИЙ ЕЛЕКТРИЧНИЙ ОПІР ЯК ПОКАЗНИК УПОРЯДКУВАННЯ СТРУКТУРИ КОКСУ

The influence of the coking process temperature on the resistivity of coke was studied. Taking into account that the resistivity and post-reaction strength are affected by some common factors, such as temperature level and coke readiness, which indicates the orderliness of its structure, the relationship between these indicators was established. The analysis of dependencies and their statistical evaluation indicates that the studied relationships are characterized by high values of correlation coefficients (0.77–0.84) and determination (59.29–70.56 %).

Review of Recent Research on Coke Gasification in a Blast Furnace with Elevated Hydrogen Levels and Determination of the Coke’s Postreactive Strength CSR 2. Laboratory Research on Coke Gasification in the Presence of H2 and H2O

Review of Recent Research on Coke Gasification in a Blast Furnace with Elevated Hydrogen Levels and Determination of the Coke’s Postreactive Strength CSR 2. Laboratory Research on Coke Gasification in the Presence of H2 and H2O

Reliable exploration of the deposit as the first step in the process of forecasting the quality of commercial coal

The article presents the basics of the deposit exploration process carried out at Jastrzębska Spółka Węglowa, which aims to ensure a rational exploitation of resources while maintaining high product quality. It showcases the problems associated with the small mass of samples coming from the exploration wells, which make determining the key quality parameters of coke impossible and proposes solutions to assess the quality of coals in terms of producing coke with high parameters, as determined by the Nippon Steel Corporation (NSC) test, i.e. coke reactivity (CRI) and post-reaction strength (CSR). Jastrzębska Spółka Węglowa, in initiating the “Quality Program” in 2018, covering the processes of deposit modeling, production planning and scheduling, and commercial product quality monitoring, set the goal of improving production processes by enabling the control of the production planning process. Such efforts are aimed at enabling the dynamic adjustment of product quality to the changing business environment, particularly at a time of increased decarbonization efforts in the European steel industry. Knowing the quality of deposits is a milestone in the process of predicting the quality of a commercial product. The primary tools for exploration of the deposit are both surface and underground drilling and sampling of seam coal during ongoing access and mining operations. In addition, analysis of qualitative data, i.e. physicochemical parameters, coking parameters and petrographic analysis from previous mining operations is carried out for the purpose of assessing coal quality and its suitability for coking.

Ефективність використання коксу із заданими значеннями питомого електричного опору

DOI: 10.31081/1681-309X-2024-0-2-28-32 Specialty161, 051. U.D.C. 661.66.2:537.311/.312 EFFICIENCY OF COKE UTILISATION WITH SPECIFIED VALUES OF ELECTRICAL RESISTIVITY © V.V. Vladymirenko, N.M. Dyakova (National Technical University "Kharkiv Polytechnic Institute", 2, Kyrpychova str., Kharkiv, 61002, Ukraine), I.V. Shulga, Ph.D. in Technical Sciences, (State Enterprise “Ukrainian State Research Institute for Carbochemistry (UKHIN)”, 7 Vesnina str., Kharkiv, 61023, Ukraine) The article shows that ensuring the specified values of coke resistivity for different directions of its use allows achieving a positive effect in metallurgical production. It is noted that the resistivity of coke for modern blast furnaces using pulverised coal should be minimal. This is ensured by the proper final coking temperature, which makes it possible to obtain coke with the required level of readiness – the final temperature should be at least 1100 оС. This reduces not only the specific electrical resistance of coke, but also its reactivity. The post-reaction strength of the coke is also significantly increased. This makes it possible to reduce coke consumption for pig iron production and increase the productivity of blast furnaces. As a result, it can be achieved the generation of an additional profit of UAH 377.20 per ton of coke. The resistivity of ferroalloy coke, unlike blast furnace coke, should be as high as possible, which will increase the amount of heat generated in the electric circuit of ferroalloy furnaces and used for endothermic reduction reactions. Therefore, lower coke readiness and lower final coking temperatures are sufficient to produce ferroalloy coke. The use of such coke makes it possible to increase the productivity of electric furnaces for smelting ferroalloys and reduce the consumption of raw materials and electricity. According to the results presented in this article, the additional profit is 4741.37 UAH per ton of coke. The weighted average efficiency of the use of coke with given values of resistivity in the national economy, determined by the volume of coke use in various industries, is 464.48 UAH per ton of coke. Keywords: coal coke, electrical resistivity, post-reaction strength, blast furnace production, ferroalloy production, economic efficiency. Corresponding author I.V. Shulga, e-mail: ko@ukhin.org.ua

Впровадження технології трамбування на діючих коксових батареях

DOI: 10.31081/1681-309X-2024-0-2-14-28 Specialty 161. U.D.C. 662.74.2 IMPLEMENTATION OF TAMPING TECHNOLOGY AT OPERATING COKE OVEN BATTERIES © S.O. Kravchenko, Ph.D. in Technical Sciences (STATE ENTERPRISE "STATE INSTITUTE FOR DESIGNING ENTERPRISES OF COKE OVEN AND BY-PRODUCT PLANTS'' (SE "GIPROKOKS''), 61002, 60 Sumska str., Kharkiv, Ukraine), D.V. Miroshnychenko, Doctor of Technical Sciences (National Technical University "Kharkiv Polytechnic Institute", 2, Kyrpychova str., Kharkiv, 61002, Ukraine), V.V. Koval, Ph.D. in Technical Sciences (STATE ENTERPRISE “UKRAINIAN STATE RESEARCH INSTITUTE FOR CARBOCHEMISTRY (UKHIN)”, 7 Vesnina str., Kharkiv, 61023, Ukraine), M.O. Solovyov, Ph.D. in Technical Sciences, S.Y. Abdullin, S.G. Grankin (SE "GIPROKOKS'') The article is devoted to verification of ensuring the appropriate economy and efficiency of coke production while reducing the level of consumption of scarce raw materials in order to optimise production in the current conditions of a coke-chemical enterprise. It is shown that the production of blast furnace coke using the technology of tamping the coal charge allows the use of a large amount of cheap gas coal without reducing the quality of the resulting blast furnace coke. However, despite the fact that this coking technology has been in use for a long time, the literature data on the impact of increasing the loading density on coke quality parameters is insufficient, contradictory and outdated. This article describes the main technical solutions for the conversion of an existing coke oven battery from the bulk coking chamber loading technology to the tamped coal cake loading technology and presents the results for the reconstructed coke oven battery. This project was developed and implemented by SE “GIPROKOKS” and HuDe. The economic and technological indicators of coke quality as a result of the conversion of the existing coke oven battery to the technology of loading a tamped coal cake were considered and compared with the parameters of its operation using the technology of bulk loading of coking chambers. It is shown that during the control period of observations (19 months) of the enterprise's operation, the mechanical strength of M25 coke increased on average from 85.2 to 87.4 %; post-reaction strength CSR – from 48.9 to 53.9 %; at the same time, the abrasion index M10 decreased from 8.0 to 5.9 %, and the reactivity CRI – from 38.0 to 37.2 %, respectively, when working using the tamping technology compared to the bulk method. In addition, the coke obtained by using the charge tamping method is characterised by lower values of ash and total sulphur content. Keywords: coke oven battery, charging, bulk (gravity) method, tamping technology, coal cake, coke properties. Corresponding author S.O. Kravchenko, e-mail: sa_kravchenko@giprokoks.com

Effect of coal tar pitch on highly reactive coke properties and microstructure

ABSTRACT Highly reactive and high-strength cokes are important for developing and producing hydrogen-rich blast furnaces. The work aimed to produce cokes with high reactivity and high post-reaction strength. The coal tar pitch (CP) was added to improve the post-reaction strength of cokes on the premise of adding alkali metals or alkaline earth metals to improve the reactivity of cokes. The chemical reactivity index of coke samples generally decreases by about 1%, while the post reaction strength of coke samples shows a significant improvement after the addition of coal tar pitch, with coke rich in CaO increasing by about 6% and coke rich in K2CO3 and Na2CO3 increasing by about 3% after adding the CP. Besides, the structural strength and micro strength of coke samples from the composite CP were improved. The microstructure analysis of the coke samples before and after the composite CP showed that the addition of the CP could weaken the originally developed pore structure of the coke samples and reduce the surface area of the gasification reaction of coke samples. Therefore, the gasification reaction of coke samples was inhibited. Moreover, the CP reduced the damage of alkali or alkaline earth metals to the dense aromatic-ring structure in the carbon matrix during the carbonization process of coking coal. It increased the amount of qualitative carbon in the coke samples and the order of carbon microcrystals. The effect of the CP on coke samples varied due to differences in coking coal and catalyst types.

Вплив сировинних та технологічних факторів на сорбційні властивості доменного коксу.

The influence of raw material factors (component composition of batches, petrographic characteristics, indicators of proximate and plastometric analyses, granulometric composition) and technological factors (coking period, process temperature) on the sorption properties of the carbonized product (coke) has been studied. Based on the research results, it is shown that such characteristics of coke as low humidity and ash, minimal yield of volatile matters, developed pore system and low cost make its use as a sorbent promising and economically justified. Standardized methods for studying the technological properties of coal and coal blends (particle size distribution, technical analysis, petrographic analysis), as well as special methods for determining the sorption capacity (for alkali and acid) and adsorption activity (for iodine and methyl blue) were used in the study. The qualitative characteristics of coke were studied using physical, mechanical and thermochemical methods to investigate standardized indicators: particle size distribution, fractility (M25), abrasion (M10), reactivity (CRI), and post-reaction strength (CSR). Mathematical statistics methods were used to analyze the influence of raw material factors on the characteristics of coke sorbent. The conducted research made it possible to establish the dependence of the sorption characteristics of coke on the structural features and nature of coal raw materials (yield of volatile matters, vitrinite content) and the structure and degree of readiness of coke (yield of volatile matters coke). The obtained dependences for predicting the alkali and acid sorption capacity and iodine adsorption activity, taking into account the vitrinite content and the volatile matter yield of the charge, are characterised by high correlation coefficients r (0.912 and 0.927 and 0.937, respectively), so they can be recommended for predicting these indicators. Keywords: carbon adsorbents, coke sorbent, sorption capacity, adsorption activity, activation. Corresponding author: D.V. Miroshnichenko, e-mail: dvmir79@gmail.com

Експериментальне дослідження залежності питомого електричного опору коксу від кінцевої температури

The dependence of the resistivity on the final coking temperature was studied on cokes obtained from the charge of one of the leading coke plants in Ukraine in a laboratory furnace designed by SE "UKHIN" with electric heating. The increase in the final temperature naturally contributes to an increase in coke readiness and the degree of orderliness of its structure. This is manifested in an increase in coke strength (increased resistance to grinding forces and post-reaction strength, reduced abrasion), increased coke density and porosity, reduced reactivity, volatile substance yield and specific electrical resistance. The increase in the final temperature contributes to the deepening of thermochemical polycondensation processes of coke formation, which causes the loss of additional low-molecular weight products, resulting in a slight decrease in the yield of gross coke and its sulphur content with a simultaneous increase in ash content. The previously theoretically substantiated hypothesis about the exponential nature of the dependence of the decrease in the specific electric coke with an increase in the final coking temperature was experimentally confirmed. Processing of the obtained experimental data made it possible to determine the numerical characteristics of this dependence, which makes it possible to determine the rational level of final coking temperatures when producing coke for various applications. In particular, to produce coke with a resistivity not exceeding 0.1 ohm∙cm, the final coking temperature should not be less than 957 oC. This is in line with the practice of coke production. To produce blast furnace coke with a lower resistivity, a higher temperature is required, while to produce ferroalloy coke with a higher resistivity, on the contrary, a lower temperature level is sufficient. Keywords: coal coke, electrical resistivity, final coking temperature, coke readiness, blast furnace coke, ferroalloy coke. Corresponding author I.V. Shulga, e-mail: ko@ukhin.org.ua

THE ESTIMATION OF THE EFFECT OF COKE, OBTAINED WITH PARTICIPATION OF VOLUME-MODIFYING ADDITIVES, ON THE TECHNICAL AND ECONOMIC INDICATORS OF BLUST FURNACE SMELTING

The article deals with the effect of the coke resistance index CSR (Coke Strength after Reaction) on the technical and economic indicators of the blast furnace process. It is shown that in the production of metallurgical coke using volume-modifying additives in the amount of 0.25% by weight of the coal load, its strength improves, in particular, index CSR. As a volume-modifying additives, α-Al2O3 electrocorundum and α-SiC carborundum with a particle size of <45 μm and vibromilenum α-SiC carborundum with a particle size <12 μm were used.
 Due to the introduction of fine powders of electrocorundum and carborundum into the coal charge, the maximum increase in the coke post-reaction strength index (CSR) by 7.6% was obtained.
 The influence of changes in individual indicators of coke quality on its consumption and productivity of the blast furnace was assessed in accordance with the guidance document of the metallurgical division of Metinvest Holding LLC. This document contains a detailed methodology for use in analyzing fluctuations in specific coke consumption and throughput of blast furnaces influenced by changes in blast furnace process parameters (by factor analysis). This technique is based on quantitative relationships between changing parameters (factors) and specific coke consumption (blast furnace productivity).
 There has been made an expert technical and economic assessment of the feasibility of introducing 0.25% fine powdered α-Al2O3 and α-SiC powders into the mixture from the point of view of blast-furnace production with pulverized fuel injection technology. The results show that, despite the increase in the cost of coke with the introduction of volume-modifying additives into the mixture, a reduction in the cost of iron can be achieved due to the expected reduction in the specific consumption of coke due to an increase in its post-reaction strength.

Коксування трамбованих вугільних шихт. Вміст газового вугілля ≥40 %.

COKING OF RAMMED COAL CHARGES. GAS COAL CONTENT ≥ 40% N.V. Mukina (Coke-chemical production of PJSC “ArcelorMittal Kryvyi Rih", 50095, Kryvyi Rih, Krivorozhstal st., 1, Ukraine), D.V. Miroshnichenko, Doctor of Technical Sciences (National Technical University "Kharkiv Polytechnic Institute", 61002, Kharkov, Kirpichev str., 2, Ukraine) Preliminary studies have shown that an increase in the sintering ability, determined by both plastometric and petrographic methods, and the coking capacity of a charge with a gas coal content of ≤ 40% leads to an improvement in the mechanical strength of blast-furnace coke. Graphical and mathematical dependencies have been developed to predict the mechanical and post-reaction strength indicators, as well as the reactivity of blast-furnace coke obtained from a rammed charge with a gas coal content of ≤ 40%. This paper presents similar studies, however, using coal mixtures characterized by the content of coal of the gas group ≥40%. The coal concentrates of the operating coke-chemical production, which are part of the coal charge for tamping, were studied. The initial samples were studied using a set of standardized methods with the determination of data from technical, petrographic and granulometric analysis, as well as the chemical composition of the ash. In addition, in the samples taken, the value of the Hardgrave’s grind ability coefficient and the expansion pressure in the tamped form were determined. Laboratory coking of coal charges was carried out in a five-kilogram laboratory furnace. The tamped cake was made in a separate collapsible matrix. Based on the results of experimental coking, it was found that the mechanical strength of coke obtained from coal charges, characterized by an increased (more than 40%) content of gas group coal, is most affected by the degree of metamorphism (Vdaf, R0) and expansion pressure (P10). Mathematical and graphical dependences have been developed to predict the mechanical (P25, I10) and post-reaction strength (CSR), as well as the reactivity (CRI) of coke obtained from coal blends characterized by an increased content of gas group coal. Keywords: coal, rammer, coke, mechanical strength, reactivity. Corresponding author D. V. Miroshnichenko, e-mail: dvmir79@gmail.com

Сировинна база коксування КХВ ПАТ «АРСЕЛОРМІТТАЛ КРИВИЙ РІГ» у період з 2017 по 2021 рік.

RAW MATERIAL BASE FOR COKING OF THE COKING PRODUCTION OF PJSC "ARCELORMITTAL KRYVYI RIH" IN THE PERIOD FROM 2017 TO 2021 © N.V. Mukina (Coke-chemical production of PJSC "ArcelorMittal Kryvyi Rih", 50095, Dnepropetrovsk region, Kryvyi Rih, Krivorozhstal st., 1, Ukraine), D.V. Miroshnichenko, Doctor of Technical Sciences (NTU "Kharkiv Polytechnic Institute", 61002, Kharkiv, st. Kirpicheva, 2, Ukraine) The article presents the data on coal components that were used in the charge for coking coke oven batteries №№1-4 (bulk coal charge) and №№ 5, 6 (tamped coal charge) of the coke-chemical production of PJSC "ArcelorMittal Kryvyi Rih" in the period from 2017 to 2021, as well as averaged information on some quality indicators of the produced coke. In general, the coal raw material base of the enterprise for the last five years has been of a stable inter-basin nature with a predominance of coals from the USA, Kazakhstan, and the Russian Federation. It is shown that, as the tamping technology suggests, moisture content, bulk density and content of classes less than 0.16 and less than 3.0 mm in coal charges supplied to the coal waste plant. №№ 5, 6 are significantly higher than the values of similar indicators of coal charges supplied to the numbers 1-4. Along with this, due to the use of coals of a certain quality, ash content, total sulfur content and the thickness of the plastic layer in coal charges supplied to the coal bunker №№ 1-4, is slightly higher than similar indicators of coal charges supplied to the boiler №№ 5, 6. In total, during 2017-2021, the composition and quality indicators of the coal charge for the production of coke at the boiler plant №№ 1-4 practically did not change, while in the coal charge for the production of coke on coke oven batteries №№ 5, 6 there is a decrease in the share of highly volatile coals with a simultaneous increase in the content of medium-volatile and low-volatile components. The given values of the quality indicators of the obtained blast-furnace coke indicate that the use of tamping technology makes it possible to obtain blast-furnace coke of a higher quality than by using a traditional technology. In particular, the coke obtained at the oven batteries №№ 5, 6 are characterized by lower values of ash content, total sulfur content and abrasion (M10) with higher values of mechanical strength in terms of M25 and post-reaction strength (CSR). Keywords: coal, inter-basin raw material base, coking, charge tamping, coke quality. Corresponding author N.V. Mukina, е-mail: Natalia.Mukina@arcelormittal.com

Evolution Characteristics and Influence Mechanism of Binder Addition on Metallurgical Properties of Iron Carbon Agglomerates

Utilization of iron carbon agglomerates (ICA) is considered to be an innovative technology to realize low carbon blast furnace (BF) ironmaking. The preparation of ICA with utilization of polyvinyl alcohol (PVA) and coal tar pitch (CTP) as binders was proposed in this study. The influence mechanisms of binder addition on the metallurgical properties of ICA were revealed. The results show that adding PVA is beneficial to improving the compressive strength of briquettes due to the chemical adsorption between the binder and the material particles. However, with the increase of PVA addition ratio from 0 to 1.0 pct, the compressive strength of ICA decreases from 2854 N to 2601 N. Meanwhile, the addition of PVA has no effect on the carbon crystallites structure of ICA and the reactivity of ICA present few changes, which are all at about 60 pct with the increase of PVA addition ratio from 0 to 1.0 pct. In addition, as the addition of CTP increases from 0 to 7 pct, the microstructure of ICA becomes dense and less porous, which can improve the compressive strength of ICA from 1639 to 3168 N. Although the reactivity of ICA is slightly reduced from 65.6 to 58.1 pct due to the development of carbon crystallites structure, it is still much higher than that of conventional metallurgical coke (30 to 35 pct). Meanwhile, the post-reaction strength is improved from 11.9 to 19.6 pct. However, as the addition amount of CTP exceeds 7 pct, the beneficial effects of CTP addition are attenuated. CTP is more suitable to be the binder of ICA, and the appropriate ratio of CTP is 7 pct.

Effects of microscopic characteristics on post-reaction strength of coke

ABSTRACT The thermal properties of coke are important for coking production and blast furnace operation. At present, the Coke Reactivity Index (CRI) and Coke Strength after Reaction (CSR) indices are used as key indicators for evaluating these thermal properties. Furthermore, the strength after a certain percentage of carbon loss has been used as a supplementary indicator. The aim of the present study was to elucidate the connection between microscopic characteristics and the post-reaction strength of coke. The pore structures of different industrial cokes were examined via optical microscopy. The indicators extracted from pore-wall distribution curves exhibited a strong correlation with the coke post-reaction strength. Using multiple linear regression analysis, we modeled the effects of ternary factors on this strength. The model may provide a new means of coal blending aimed at improving the quality of coke.

The effect of briquette composition on coking pressure generation

A coal normally used in coking blends was employed to study the effect of briquettes on coking pressure. The study is focused primarily on two parameters i) bulk density which increases with the use of briquettes and ii) the composition of the briquettes containing materials which have contrary effects on coking pressure. Four briquettes with different compositions were prepared, two of them containing biomass. A non-coking coal and coal tar as binder were included in the composition of all four briquettes. The permeability of the plastic phase to gas flow was studied for blends of coking coal with individual briquette components and for blends of coking coal with 15 wt% of the four briquettes. The coking pressure was measured in a movable wall oven and the mechanical strength, coke reactivity and post-reaction strength of the cokes were assessed by means of standard tests, JIS, CRI/CSR. It was found that all four briquettes produced lower coking pressure than that generated by the coking coal regardless of the increase in bulk density while the cokes retained their quality up to 15 wt% briquette addition.

Influence of Iron Ore Addition on Metallurgical Reaction Behavior of Iron Coke Hot Briquette

Utilization of iron coke hot briquette (ICHB) has been considered to be one effective countermeasure to achieve low-carbon blast furnace. Before its actual application, a series of extensive fundamental investigations on the ICHB are required. In this study, the influence of iron ore addition on the metallurgical reaction behavior of ICHB made from carbonizing coal–iron ore composite agglomeration were investigated based on Chinese raw material conditions, and the corresponding mechanisms were revealed. The results show that the addition of iron ore concentrate leads to the degradation of the compressive strength and drum strength of ICHB, but they are maintained at a relatively high level. Furthermore, by increasing the addition ratio of iron ore from 0 to 20 pct, the density of ICHB is enhanced from 1413 to 1637 kg/m3, and the porosity is increased from 8.03 to 12.84 pct, and the optical texture index (OTI) is reduced from 58.1 to 25.3. The phase composition of ICHB mainly consists of C, Fe, SiO2, Fe3O4, and FeO after the addition of the iron ore concentrate. Moreover, the reactivity of ICHB is accelerated from 46.74 to 69.54 pct due to the catalytic effects of metallic iron and iron oxide, which worked as oxygen transfer carriers, while the post-reaction strength is reduced from 74.08 to 36.81 pct. In addition, the starting temperature of the ICHB gasification reaction is decreased remarkably from 919 °C to 839 °C. The activation energy (Ea) for the gasification reaction under nonisothermal conditions is reduced from 312.78 to 249.83 kJ/mol, and the preexponential factor (A) shows a decreasing trend as well. Simultaneously, Ea and A display the kinetic compensation effect and present a good linear relationship.

Investigation on Gasification Reaction Behavior and Kinetic Analysis of Iron Coke Hot Briquette under Isothermal Conditions

Gasification reaction behavior of iron coke as well as kinetic parameters is extremely important for its quality evaluation and practical application in an actual blast furnace. However, there are few researches on the gasification behavior of iron coke, especially for iron coke hot briquette (ICHB) prepared by hot briquetting process. In this paper, the gasification reaction behavior of ICHB is experimentally investigated under isothermal conditions. Meanwhile, the kinetic analysis for the gasification process of ICHB and the related mechanism are carried out. The results demonstrate that the increase of the reaction temperature causes the significant rise of the carbon conversion rate and the reaction rate of ICHB, while the post‐reaction strength is evidently decreased. The size degradation of ICHB after reaction is increasingly serious as the reaction temperature goes up, and more pores as well as cracks are generated inside the gasified ICHB. During the gasification, the reduction of iron oxide, the oxidization of metal iron, and the generation reaction of fayalite are concomitantly occurred. The most probable mechanism function is confirmed. Based on this model, the activation energy and pre‐exponential factor are conducted, which are 144.77 kJ mol−1 and 999.37 min−1, respectively.

Research on the Post-reaction Strength of Iron Coke Hot Briquette Under Different Conditions

The utilization of iron coke hot briquette (ICHB) prepared by carbonizing iron ore–coal composite agglomerate made from hot-pressing the mixture of iron ore and blended coal has been considered to be an effective countermeasure to improve blast furnace ironmaking reaction efficiency and to reduce carbon emissions. The strength of ICHB after gasification reaction is overestimated by the Chinese National Standard (GB/T 4000/2008, equivalent to the Nippon Steel Corporation method) and should be evaluated by different methods. In this study, the post-reaction strength of ICHB with the addition of different ratios of iron ore under various conditions was experimentally investigated to illuminate the degradation mechanism of ICHB reacted with CO2. The results showed that, with increasing the iron ore addition ratio from 0% to 20%, the reactivity of ICHB reacted with CO2 at 1100°C for 2 h is remarkably increased, due to the catalytic effect of metallic iron in ICHB, while the post-reaction strength is distinctly decreased. Furthermore, stopping at the weight loss ratio of 20%, the strengths of ICHB after reaction at 1100°C under a CO2 atmosphere and a CO2/CO=1/1 atmosphere are clearly reduced, from 89.74% to 75.93% and from 85.24% to 73.65%, respectively. Meanwhile, the post-reaction strength of ICHB under CO2 is greater than that obtained under CO2/CO=1/1 atmosphere, since there is more time for the reaction gas to diffuse from the exterior to the interior of the ICHB under the latter condition. Additionally, the post-reaction strength of ICHB decreases with increasing weight loss ratio regardless of the reaction gas composition; however, it can be maintained at a high level.

Effects of coal and iron ore blending on metallurgical properties of iron coke hot briquette

Utilization of iron coke hot briquette (ICHB), prepared by carbonizing coal-iron ore composite agglomerate, is considered as an effective countermeasure to achieve low carbon emission blast furnace (BF) ironmaking. ICHB shows high reactivity and thereby presents low post-reaction strength, which could have serious impact on the permeability of BF. In this paper, the effects of coal and iron ore blending on the metallurgical properties of ICHB were experimentally investigated and related mechanism were revealed based on Chinese raw material and fuel conditions. The results showed that with increasing coal B addition ratio, the compressive strength of ICHB is slightly improved. The gasification reaction ratio of ICHB is gradually decreased while the post-reaction strength is increased. Furthermore, with increasing coal C ratio, the compressive strength of ICHB tends to slightly increase firstly and then mildly decrease. The reaction ratio of ICHB is decreased firstly and then increased while the post-reaction strength and the crystallite size (Lc) tend to be enhanced initially and then reduced. Additionally, with increasing the addition ratio of iron ore from 0 to 20%, the compressive strength of ICHB is reduced from 5602 N to 4594 N while the porosity of ICHB is increased. The reaction ratio of ICHB is accelerated from 48.22% to 75.02% while the post-reaction strength is reduced from 74.08% to 26.84%. In terms of coal blending and iron ore blending, the reasonable preparation parameters of ICHB are conducted, namely 55% coal A, 10% coal C, 20% coal D, and 15% iron ore. Under the conditions, the compressive strength, the reaction ratio, and the post-reaction strength of ICHB are 4861 N, 63.00%, and 46.45%, respectively.

Optimal preparation of oxidized coal

The oxidation index is an important characteristic of coal and coal batch, indicating the change in coking properties on oxidation. The coke obtained from coal batch containing poorly clinkering oxidized coal has a higher content of isotropic carbon and a lower content of anisotropic carbon. That explains its increased reactivity and impaired mechanical and postreactive strength. The oxidation on storage is greatest for small coal classes (<0.5 mm). Preliminary removal of <0.5 mm oxidized coal markedly improves the reactivity and also the mechanical and postreactive strength. A method of preparing oxidized coal for coking is proposed: finer grinding (until the content of the ≤1 mm class is 100%). That considerably reduces the influence of the oxidized coal on the quality of the coke produced.

Effect of pore structure and matrix reactivity on coke reactivity and post-reaction strength

Metallurgical coke accounts for a significant portion of the costs associated with blast furnace operations. The coke reactivity index (CRI) and coke strength after reaction (CSR), determined via the Nippon Steel Corporation test, are the most popular indexes for estimating the high-temperature properties of coke. Multiple factors affect the coke solution-loss reaction, and the CRI and CSR depend on the composition and structure of the coke. The pore structure is one of the most important factors affecting this reaction. The effect of the pore structure on the coke reactivity was determined by quantitatively evaluating the CRI and CSR of 10 types of coke. In each case, the corresponding structure was determined via image analysis. Furthermore, the initial reaction rate of the coke matrix was determined via thermogravimetric analysis of the fine grains. Mathematical models, quantitatively describing the CRI and CSR, were formulated via multiple linear regression, and the fit of the results to the experimental data was verified via the regression coefficient and a significance test. The models indicated that pores with sizes of 60–120 µm have a strong positive impact on CRI. In the case of invariant CRI, the high reactivity of the matrix has a positive impact on the post-reaction strength of the coke.