Coke Reactivity Index Research Articles

Post reactive strength and reactivity of metallurgical coke: infrared gas analyzer

ABSTRACT Coke reactivity index and coke strength after reaction traditionally evaluated by reacting coke with carbon dioxide in standard condition. Several testing standard/methods viz., American society for testing and materials, Japan Industrial Standard, Bureau of Indian Standards, and International Organization Standard exists, which are used worldwide to measure the hot strength of metallurgical coke. In the Indian operation of Iron and steel plants, coke strength after reaction is a vital coke quality parameter for assessing the relative strength of coke for the blast furnace-efficient operation. The mentioned testing methodology is lengthy and takes significant time (~7 h) to complete a single test. Consequently, it needs to develop a method for the coke reactivity index, predicting almost real-time data. A newly developed methodology by infrared gas analyzer was used for developed and validated with coke oven plant coke samples. Result confirmed that the predicted and measured coke CRI with the Nippon Steel Corporation method has a strong positive relationship (R2 = 0.92). The results also confirmed the interrelationship between the predicted and actual coke CSR. The developed model can provide a real-time coke reactivity index and estimate the coke CSR within 10 min of reaction time.

A New Type of Composite Coke Prepared from Steel Slag and Mixed Coal: Preparation Process and Microstructure

High‐reactivity coke is a kind of burden for a low‐carbon blast furnace. Herein, a new method of preparing steel slag composite coke (SCC) from steel slag and mixed coal is proposed. The effects of the raw material ratio and carbonization parameters on the compressive strength, coke reactivity index (CRI), and coke strength after reaction (CSR) are investigated, and also the phase structure and functional group are analyzed. In addition, because the main chemical composition of steel slag is CaO, the effects of the CaO component on the phase structure and functional groups are studied. The results show that with increasing steel slag ratio, the compressive strength of SCC tends to decrease. When increasing the steel slag ratio from 5% to 15%, the CRI tends to increase from 53.7% to 61.0%, and the CSR decreases from 38.6% to 6.2%. With increasing anthracite ratio, the compressive strength of SCC first increases and then decreases. With the carbonization temperature increasing, the Ca2SiO4 gradually fades away, Fe3O4 is gradually reduced to Fe, and the aromatic CC and stretching OH absorption zone is decreased. With the increasing of CaO content, Ca2Al2SiO7 tends to increase, and the intensity of the peak band (002) and peak band (100) is lowered.

Novel method for coke optical texture measurement and application on coke derived from different ranks of coking coal

AbstractThe optical texture of coke is undoubtedly one of the important factors that determined many properties of coke, but it still mostly depends on the skills and experience of manual analysis. In this paper, a novel automatic measurement method is proposed for coke optical texture. this method through two analyzer angle images(10° and 170°) under polarizing microscope to recognize isochromatic regions which occurs color changed between blue and red by image processing, then characterize the dimensional sizes of isochromatic regions and classify them into different anisotropic texture type. Two fitted ellipse methods are used to characterize the regions' dimensional sizes by the range of shape factorS, followed by classifying different types of anisotropic texture according to the long and short axes of fitted ellipse. An automatic image acquisition and analysis system is established based on the above method. Finally, eight coke samples derived from different ranks of coking coal were selected to test the proposed method. The result shows that it can effectively recognize different types of anisotropic texture and provide composition of different anisotropic texture type for each coke. Moreover, the anisotropic degree of coke shows a significant positive correlation with parent coal rank and a negative correlation with coke reactivity index (CRI).

Effects of solution loss degree, reaction temperature, and high temperature heating on the thermal properties of metallurgical cokes

In this work, the thermal properties of nineteen metallurgical cokes were measured using the conventional NSC method and three proposed methods to investigate the effects of solution loss degree, reaction temperature, and high temperature heating on the thermal properties. It was found that the linear negative correlations between the index representing coke strength after reaction and the index representing coke reactivity in the proposed methods similar to blast furnace conditions were significantly lower than that of coke strength after reaction (CSR) and coke reactivity index (CRI) in the NSC method. These results contradict the conventional viewpoint that the lower the coke reactivity, the higher the coke strength (CSRBF) after reaction in blast furnace. Compared with coke reactivity, coke strength after reaction was more susceptible to the differences in solution loss degree and reaction temperature. Therefore, the CSR index in the NSC method may lead to a large misjudgment of the quality of some cokes. The initial reaction temperature Ti was relatively independent of coke reactivity and strength after reaction, and is a new index to characterize the thermal properties of coke. The significant decrease in the thermal strength of some cokes indicated that high temperature heating was an important factor in the characterization of coke thermal properties. This paper provides a reference for the comprehensive understanding and evaluation of the thermal properties of coke, and at the same time, lays a foundation for subsequent studies.

Application Study of Sigmoid Regularization Method in Coke Quality Prediction

Coke is an indispensable and vital flue for blast furnace smelting, during which it plays a key role as a reducing agent, heat source, and support skeleton. Models of prediction of coke quality based on ANN are established to map the functional relationship between quality parameters Mt, Ad, Vdaf, St,d, and caking property (X, Y, and G) of mixed coal and quality parameters Ad, St,d, coke reactivity index (CRI), and coke strength after reaction (CSR) of coke. A regularized network training method based on Sigmoid function is designed considering that redundancy of network structure may lead to the learning of undesired noise, in which weights having little impact on performance and leading to overfitting are removed in terms of computational complexity and training errors. The cascade forward neural network with validation is found to be the most suitable one for coke quality prediction, with errors around 5%, followed by feedforward neural network structure and radial basis neural networks. The cascade forward neural network may play a guiding role during the coke production.

Microstructural evolution of metallurgical coke: Evidence from Raman spectroscopy

Raman spectroscopy traces the microstructural evolution of carbonaceous matter (CM) during artificial heating. Thermo-chemical reactivity and strength of blast furnace coke at 1100 °C is dependent on the graphitization state of the feed coke. A standard coke reactivity index (CRI) sample is composed of lumps, showing a high microstructural variability. The frequency distribution of the D-STA parameter estimated by the “Interactive Fitting of Raman Spectra” (IFORS) software suggests a positive correlation between degree of CM organization and CRI. Samples from the tuyere region of an operating blast furnace evidence graphitization of CM at temperatures higher than 1900 °C. IFORS parameters, calibrated by x-ray diffraction-based lattice dimensions and transmission electron microscopy data constrain a temperature gradient decreasing from the raceway to the deadman zone. The gradient controls a continuous variation of the petrographic coke texture. As an application, the IFORS method is able to map the graphitization zones in the hearth of a working blast furnace.

Effect of Microlithotype Maceral Distribution on Coke Quality

The coking behavior of coal is an important facet in utilization of coal in metallurgy and in other industries. The carbonization behavior of coal mainly depends on coal rank, petrographic composition, ultimate composition and rheology of coal. Coal petrography has become very useful technique for establishment between formulation of coal blend composition and coke quality prediction. It is generally established that blend containing optimal reactives produces the coke of maximum strength. The coking properties of coal not depend only on the macerals composition, but also on the way in which the macerals are distributed among one another, forming preferential associations called microlithotypes. The measurements of relative proportion of microlithotypes are called microlithotype analysis. In present work, distribution of macerals (microlithotype) in coal samples were studied and correlated with the coke quality. Beneficiation by wet method were carried out (only indigenous coal) by washing media of specific gravity 1.30 to 1.40 to achieve <10% ash level. Coal microlithotypes plays an important role on coke quality. Bi-maceral and tri-macerals microlithotype distribution (vitrinertite and duroclarite and clarodurite) in coal samples act as a vital role for coke quality. Inter-growth of internite within vitrinite macerals has also significant role on coke quality. Therefore, the combined analysis of maceral and microlithotype distribution is important for coke quality. Distribution of bi-maceral and tri- maceral in coal improved coke quality (M40 and M10 indices). The microlithotype distribution measurement by petrography analysis gave considerable correlations with M40, M10, Coke Reactivity Index (CRI) and Coke Strength after Reaction (CSR) parameters. It gave details the adaptability of Indian coke quality in favor of macerals assemblages in coal.

Simulation of Coke Quality Indicators Using Artificial Neural Network

The article shows the application of a neural network for modeling coke quality indicators Coke Reactivity Index (CRI) and Coke Strength after Reaction (CSR). Two optimization methods were used to train the neural network. The influence of the number of neurons on the simulation results was studied. The difference between experimental and calculated data on average does not exceed 2 %. The conclusion is made about the prospects of using a neural network to predict the values of CRI and CSR of coke.&#x0D; Keywords: artificial neural network, coke, coke reactivity index, coke strength after reaction

The effect of alkali on the reaction kinetics and strength of blast furnace coke

Coke is the main reductant for iron making in blast furnace. The reactivity and strength of coke play a very important role in selection of coke as reductant in blast furnace. The reactivity and strength of coke are inversely related to each other. It is very important to find a coke with good combination of strength as well as reactivity. Alkali elements present in coke increase the reactivity of coke on one hand while reducing the strength on the other hand. It is very important to study the effect of alkali on coke to understand its behaviour in the blast furnace. This work has been done to find out the effect of alkali elements on the coke reactivity index (CRI), coke strength after reaction (CSR) and the abrasion value (AV) of coke samples. The isothermal kinetic study has been carried out to get a better understanding of the influence of alkali on the reaction mechanism of coke during bouduard reaction.

A kinetic model approach for predicting coke reactivity index from coal and coal blend properties

ABSTRACT A novel method has been developed to estimate coke reactivity index (CRI) from coal properties through a kinetic approach. The model was derived from mass balance with a kinetic model of batch reactor CRI test. The parameters of kinetic model were optimized using non-linear least squared method. Three main properties of coals, i.e., Fe2O3 content, volatile matter, and coal rank were selected to predict the CRI. The predicted CRI value was in a good agreement with the CRI data. The standard error was less than 5. Coke strength after reaction (CSR) was predicted using linear regression of the CSR and CRI data. The estimated CSR was in good agreement with the CSR data. The sensitivity analysis of coal properties to CRI was also performed using the developed kinetic model. The model was successfully applied for coal blending to predict CRI of the produced coke with standard error 3.7. This model can explain well the catalytic effect of coal and coal blend properties to coke reactivity during the CRI test.

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.

Effect of coal moisture content on coke’s quality and yields of products during coal carbonization

The coal with low moisture during carbonization could not only increase the yield of coke, but also promote the coke quality and reduce the energy consumption. In this paper, the influence of the moisture in the blend coal (1.8%–10.13%) on the product yields and coke quality during coal carbonization were investigated. The results show that the coke yield is increased from 75.90% to 77.16%, and the coke qualities such as coke strength after reaction with CO2 (CSR), coke reactivity index (CRI), fragmentation index (M25) and abrasion index (M10)) are also improved when the moisture of the blend coal decreases from 10.13% to 1.80 % in a bench scale reactor. Due to the secondary reaction, tar become lighter when the moisture is decreased. In order to further prove the above results, the blend coal with 1.8% and 9%–10% (common moisture used in coke plant) moisture is carbonized in a coke oven with 6 m height, the results show that CRI are 23.4% and 27.3%, CRS are 67.1% and 62.2% under 1.8% and 9%–10% moisture of blend coal. Moreover, the variation of the moisture in blend coal has a limited influence on dust emission at the ascension pipe and the charging car.

Prediction of CRI and CSR of cokes by two-step correction models for stamp-charged coals – Statistical analysis

A new approach for the prediction of Coke Reactivity Index (CRI) and Coke Strength after Reaction with CO2 (CSR) was proposed. For this purpose, 41 coking coals (40 USCB and 1 Appalachian coals) and 36 coal blends were studied. Cokes were carbonized using a pilot-scale coke oven by a stamp charging. Coals and coal blends were characterized by 14 properties and cokes by CRI and CSR indexes. Experimentally determined CRI and CSR indexes of cokes (type II) did not fit well with their calculated values from regression equations based on different coal blend properties (R < ca. 0.370). The similar discrepancy was also observed if experimentally determined coke indexes were compared with weighted averages of CRI¯ and CSR¯ (R < ca. 0.390). With the view of low reliability, herein, the prediction of CRI and CSR values of 36 cokes (type II) was based on 2 newly proposed two-step models. In model 1, the first step consists of preliminary calculation (estimation) of CRI/CSR indexes using modified regression equations originally calculated for the prediction of cokes (type I) carbonized from unblended coking coals; in model 2 calculation of CRI/CSR values (type II) in the first step is carried out using calculated weighted averages of CRI¯ and CSR¯ from type I cokes. In both models, estimated CRI/CSR values were corrected using calculated correction coefficients from regression equations based on coal blend properties. If compared with a traditional one-step procedure, the results document that this novel (two-step) approach provides much better prediction of the coke characteristics.

Study on the Influence Factor of Coke Pulverization Rate and Its Effect on Operating Index of Large Blast Furnace

The carbon dissolving reaction is the main factor for the deterioration of coke in the blast furnace. Therefore, in order to investigate the effect of coke deterioration on the permeability of blast furnace, the Coke Pulverization Rate (CPR) which represented the degree of Matrix carbon loss after carbon dissolution was put forward in this paper. The results showed that the CPR increases with the increase of volatile of coal blending, ash content of coke, M10 and coke reactivity index (CRI), while decreases with the rising of M40 and coke strength after reactivity (CSR). Analysis of the production data of 5BF blast furnace of Meishan Steel showed that under the conditions of coke ash (Ad) 87%, CRI 66%, the CPR would be less than 23%, which is conductive to ensure stable permeability large blast furnace.

Caking Ability Tests for Coal Blends in Process to Utilize the Indian Origin Coals

The idea of this paper is to properly utilize Indian low-rank coking coal (semi-coking coal) with the blending of high-rank imported coals and to reduce the overall cost of coke making. The blending of the coals has been done in two phases. Effect of blending mass ratio on the swelling index and plasticity parameters has been studied. The effect of maceral content, vitrinite reflectance, and volatile matter content on the caking ability of coals has been studied. Blended sample analysis shows that there is an abrupt drop in the fluidity of the samples compared to the original coals; there is no proper relation between the fluidity and swelling index of the coal blends. Phase 1 coal blends show better results compared to phase 2 samples. Crucible swelling number values for blend 1 and blend 3 from phase 1 are 6 and 4.5, respectively. To validate the swelling number, coke strength after reaction (CSR) and coke reactivity index (CRI) tests have been done for blend 1 and blend 3 coals from phase 1. CSR, CRI for blend 1 and blend 3 samples are 22.18, 71.30 and 23.79, 70.75, respectively.

Study on the Influence of Coal Blending with Waste Rubber on Coke Quality

In order to investigate the influence of coal blending with waste rubber on coke quality, the pyrolysis performance of rubber powder was analyzed, and the coking experiment of coal blending was carried out in 70 kg test coke oven. The experimental results showed that the pyrolysis range of waste rubber was similar to that of blended coal by analyzing the pyrolysis characteristics of waste rubber. The ash content (Ad), coke reactivity index (CRI) and coke strength after reactivity (CSR) would decrease, while the sulfur content (St, d) of coke would increase with the increasing of coal blending ratio of waste rubber. The specific surface area of coke increased from 1.5m2/g to 3.5m2/g, the Lc of coke microcrystalline structure and the degree of graphitization decreased gradually with increasing the ratio of waste rubber from 0% to 6% in coal blending. The optical structure of coke showed that the fine-grained mosaic structure increased and the degree of anisotropy of coke (OTI) decreased.

Development of novel method for quantitative determination of carbon chemical reactivity

AbstractThe coke reactivity index (CRI) measurement determined with the ASTM standard is affected by both the chemical and physical properties of the coke. The contribution made by each of these factors to the measurement result cannot be easily distinguished and quantified. A new thermogravimetric analysis (TGA) technique was developed to provide further information about the chemical behaviour of the coke to facilitate an improved interpretation of the CRI measurement. The development of the technique takes into consideration the potential change in reaction rate controlling mechanism in TGA equipment. It makes use of the shrinking core model to identify the reaction rate control regime and to extract reaction rate parameters from experimental measurement. A rigorous data processing procedure was developed to ensure consistent interpretation of the measurement data while repeatability was established through measurement repetition. The sensitivity of common variable factors between different TGA apparatus on measurement results was also examined. It was demonstrated that the measurement results of this new technique are highly repeatable and reproducible.

Particular Oxydation Features of Various Mechanical Strength Cokes

Lump solid fuel is one of the most important charge material components in layered cupola units. It determines layer gas permeability, conditions development for heat exchange with gasses in it, heat generation process rate and intensity. In present-day conditions of material shaft melting charge materials of boosted fractional makeup are used, as well as oxygen, carbon and hydrogen enriched air. In the circumstances the issue of ensuring the best gas dynamic conditions become particularly vital, both for the furnace low and high temperature zones, at the charge component oxidation and recovery processes development. Under conditions of continuous charge component movement in the layered unit workspace they are subjected to abrasive action of charge components with the result, which may be described by mechanical properties based on mass yield of certain fractions after disruption in a closed drum М10 and М40. Coke lump behavior at relatively high temperature (below 1100°С) in the presence of complete fuel combustion products СО2 and Н2О may be implicitly evaluated by coke strength after reaction (CSR) and coke reactivity index (CRI). When studying, particular combustion features of coal coke in conditions close to shaft cupola unit operation data of the total differential scanning calorimetry (DSC) curve were used. Temperature ranges of intensive heat generation were determined from the beginning of active coke sample oxidation to completion of the burnout period, as well as apparent heating capacity and coke combustion thermal effect.

Use of thermogravimetric analyzer and high temperature furnace as an alternative to the coke reactivity index test and study on effect of binders in metallurgical coke making

Use of thermogravimetric analyzer and high temperature furnace as an alternative to the coke reactivity index test and study on effect of binders in metallurgical coke making

VOC and PAH characterization of petroleum coke at maximum thermal decomposition temperature

ABSTRACTIn steel industry, hard coal is proceeded in coke ovens to produce metallurgical coke. In this process, some additives such as petroleum coke (petcoke) are used for optimizing operational cost. For the determination of addition ratio of petcoke, it is important not to disrupt coke quality, especially with respect to coke reactivity index and coke strength after reaction, while another important point is emission quality. In this study, petcoke gas (PCG) emitted from the thermal decomposition of petcoke at the maximum thermal decomposition temperature is characterized for volatile organic compounds (VOCs) and polyaromatic hydrocarbons (PAHs) and the results are assessed in comparison to the coke oven gas (COG). First, the petcoke sample is heated for gasification by using thermal gravimetric analyzer-DTA device. The gas in the temperature range of 490–510°C, where the highest gasification acceleration occurs, is taken from the funnel and transferred to GC-MS device by using a headspace gas sampler unit. The total VOC concentration in PCG and COG is found to be 121.76 ppm and 5,774.76 ppm, respectively, while the total PAH concentrations are 0.625 and 0.495 ppm, respectively. The results show that using petcoke in coal blend seems to be a more environment-friendly process with respect to a significant decrease in VOC emissions.