Roga Index Research Articles

Study of cellulose additive effect on the caking properties of coal

Purpose. The work aims to study the effect of cellulose on the caking properties of various types of coking coal used in coking blends. The change in caking abilities has been analyzed to achieve the aim using standard techniques. At the same time, the effect of biomass additives on the plastic properties of coal has been analyzed comprehensively; the optimal amount of additive for practical purposes has been determined. Methods. Multiple coal characteristics in the plastic stage have been studied using a dilatometric method, the enhanced swelling pressure method, the plastometric method, and the Roga index test. The first three methods make it possible to characterize the caking properties of coal; and the Roga index test characterizes its coking ability. Findings. It has been identified that the optimal amount of biomass additive to study the effect on the properties of coal in the plastic state is more than 5 wt. %. In the paper, experimental dependences of the 5 wt. % cellulose addition influence on the caking properties of four coal grades have been obtained. The results showed a slight decrease in caking properties in terms of swelling, swelling pressure, thickness of the plastic layer, and caking ability. Simultaneously, the most sensitive methods for assessing the effect of cellulose addition on the coal plastic properties are the dilatometric method as well as the enhanced method for the swelling pressure determination. Originality. A comprehensive study of the effect of pure cellulose as a component of lignocellulose biomass on the properties of different coal grades in the plastic state (i.e. caking prperteis) has been carried out. A slight change in the coal properties in the plastic state with adding 5 wt. % cellulose, decreasing caking properties, has been shown. An important, not previously reported, conclusion is that the cellulose additive does not have any noticeable effect on the physical properties of the coal charge owing to its loose structure. Practical implications. A slight change in the caking properties of coal has been established with the addition of 5 wt. % which is of practical importance for the preparation of coal blends, and the coke production in the cases of using additives of lignocellulosic biomass without losing its quality. Additionally, renewable additive use while obtaining fuels and reducing agents is an approach to mitigate the negative environmental impact.

Assessment of the Suitability of Coke Material for Proppants in the Hydraulic Fracturing of Coals.

To enhance the extraction of methane gas from coal beds, hydraulic fracturing technology is used. However, stimulation operations in soft rocks, such as coal beds, are associated with technical problems related mainly to the embedment phenomenon. Therefore, the concept of a novel coke-based proppant was introduced. The purpose of the study was to identify the source coke material for further processing to obtain a proppant. Twenty coke materials differing in type, grain size, and production method from five coking plants were tested. The values of the following parameters were determined for the initial coke: micum index 40; micum index 10; coke reactivity index; coke strength after reaction; and ash content. The coke was modified by crushing and mechanical classification, and the 3-1 mm class was obtained. This was enriched in heavy liquid with a density of 1.35 g/cm3. The crush resistance index and Roga index, which were selected as key strength parameters, and the ash content were determined for the lighter fraction. The most promising modified coke materials with the best strength properties were obtained from the coarse-grained (fraction 25-80 mm and greater) blast furnace and foundry coke. They had crush resistance index and Roga index values of at least 44% and at least 96%, respectively, and contained less than 9% ash. After assessing the suitability of coke material for proppants in the hydraulic fracturing of coal, further research will be needed to develop a technology to produce proppants with parameters compliant with the PN-EN ISO 13503-2:2010 standard.

A Study on Bio-Coke Production—The Influence of Bio-Components Addition on Coke-Making Blend Properties

Due to global warming, technologies reducing CO2 emissions in the metallurgical industry are being sought. One possibility is to use bio-coke as a substitute for classic coke made of 100% fossil coal. Bio-coke can be produced on the basis of coal with the addition of substances of biomass origin. Blends for the production of bio-coke should have appropriate coke-making properties to ensure the appropriate quality of bio-coke. The article presents the results of the research on the influence of the addition (up to 20%) of bio-components of different origins to the coke blend on its coke-making properties, i.e., Gieseler Fluidity, Arnu—Audibert Dilatation and Roga Index. The bio-components used in the research were raw and thermally processed waste biomass of different origins (forestry: beech and alder woodchips; sawmill: pine sawdust; and the food industry: hazelnut shells and olive kernels) and commercial charcoal. Studies have shown that both the amount of additive and the type of additive affect the obtained coking properties. There was a decrease in fluidity, dilatation and Roga Index values, with more favorable results obtained for the addition of carbonized biomass and for additives with a higher apparent density. A regressive mathematical model on the influence of the share of the additive and its properties (oxygen content and apparent density) on the percentage decrease in fluidity was also developed.

Experimental study and extreme gradient boosting (XGBoost) based prediction of caking ability of coal blends

The caking ability sets coking coals apart from other coals. In the industry, the practice of blending coals with different physicochemical parameters is often used to obtain the fuel with the desired properties. Caking ability is a non-additive parameter, which means that it cannot be calculated from the weighted average of the components of the blend. In this study, a model for predicting the caking ability of coal in blends was developed, based on the XGBoost regressor machine learning method. Experiments involving blending eight coals in five different proportions were carried out to obtain a training dataset. The coals were selected to reflect the widest possible range of types and caking ability levels. The Roga Index (RI) was chosen as a measure of caking ability. The experiments proved the non-additivity of caking ability of coal in blends, in particular for low-rank coals and good quality coking coals. The Feature Importance and Partial Dependence Plots techniques were used to determine the impact of model input parameters on the predicted value. Our study demonstrated that the carbon, moisture, volatile matter and vitrinite contents had the greatest impact on predicted RI. The prediction efficiency of the model was R2 = 0.95, confirming the effectiveness of the method used.

Laboratory-Scale Tests for the Utilization of High Ash Non-Coking coal in Coke-Making Process

India has vast coal resources all over the country; however, the presence of high ash content makes them invulnerable for industrial usage. To compensate for the rapid depletion of high-quality coking coals and to compensate for the demand for coal in iron and steel sectors, coal cleaning or beneficiation and blending techniques have come into limelight for the usage of low-quality coal. In this paper, laboratory-scale experiments were performed on the utilization of Indian high ash non-coking coal (NCC) and imported semi-coking coal (SCC) for the coke preparation. At first, washability characteristics of Indian high ash coal were investigated by using jigging, spiral concentration, and sink and float density separation methods. The optimum cut-off density NCC and SCC coals were blended and sent for the caking properties analysis. Proximate and ultimate analysis, vitrinite reflectance, crucible swelling number, and caking index or roga index have been taken as the measure for the caking ability of coal blends.

Properties of Kuznets Basin gas coal

Six samples of G coal characterized by different vitrinite reflection coefficient (R o,r = 0.64–0.74%) are investigated. With increase in R o,r , the plastic-layer thickness y increases from 7 to 17 mm, the free-swelling index SI from 0.5 to 3.5, and the Roga index RI from 1 to 21. The temperature range of plasticity expands from 34 to 94°C. The results clarify the difference in clinkering properties of the gas coal.

Evaluation the Value of Some Petrographic, Physico-Chemical and Geochemical Indicators of Quality of Coal in Paralic Series of the Upper Silesian Coal Basin and Attempt to Find a Correlation Between Them

Abstract A total of 56 coal seam samples (from active and closed coal mines) representing USCB Paralic Series, were tested. It was determined that the tested coal has low content of mineral matter (especially in Hruśov Beds) as well as of Ag, As, Ba, Cd, Co, Cr, Cu, Mo, Ni, Rb, Sb, Sn, Sr, V and Zn. Only Mn and Pb content in coal is higher than in coal from other deposits around the world. There are differences in the values of physical and chemical, petrographic and geochemical indices of coal quality, between the northern and the south-western part of the USCB and in the profile of the Paralic Series. Thanks to the revealed correlations between the indices of coal quality, significant differences in the role mineral and organic substance play in concentrating some of the trace elements in the tested coal, were determined. Moreover, it was observed that an increase in the rank of coal (expressed with an increase in the value of R0 or/and Qsdaf or/and Cdaf), accompanies a decrease in the content of oxides of main elements in coal ash as well as sulfur and other trace elements in coal. The dependence was observed both in lateral and stratigraphic differences in the rank of coal. Mutual dependences between the indices of the rank of coal (R0, Cdaf, Qsdaf, Vdaf) in the northern and south-western area of the research and in Poruba Beds and Jaklovec Beds, were confirmed. It was determined that an increase in the value of Roga Index (RI) is accompanied by an increase in P2O5 content in ash of coal from the south-western part of the research area. It is probably a result of concurrence of a regional positive anomaly in the rank of coal and high P2O5 content in coal seams in the south-western part of the USCB. The observed increase in the value of RI, accompanying a decrease in the content of sulfate minerals, Cr and Ni in coal and Na2O in coal ash; results from the role the carbonisation process plays in distributing main and trace elements in the mineral matter of coal.

Molecular oriented domains (MOD) and their effect on technological parameters within the structure of cokes produced from binary and ternary coal blends

The aim of this work was to characterize molecular oriented domains in the cokes produced from binary and ternary blends of three bituminous Polish coals of varying carbon content: 82.7, 86.2 and 88.7wt.% and, consequently, of different caking propensities of the Roga Index equal to 24, 63 and 77, respectively. The coals were collected from the Krupiński, Szczygłowice and Zofiówka mines, located in the Upper Silesian Coal Basin, Poland. They are commonly used in Polish coke‐making industry. The samples were studied using transmission electron microscopy (TEM) with the 002 dark field mode (002DF). As a result of these studies, an average area (SMOD) of molecular oriented domains (MOD) was determined for each sample. Values of the SMOD parameter are discussed in relation to the composition of the blends. A distinct relationship between the Zofiówka coal content in a blend and the microtexture ordering degree of the cokes was found: the higher the Zofiówka coal content in a blend, the higher the SMOD value. Values of SMOD were related to the other structural parameters, i.e., to the average height of graphite-like crystallites, Lc, and to the percentage contribution of ordered structures, obtained using XRD and Raman spectroscopy, respectively. The cokes containing 30–50% of the Zofiówka coal in a blend were found to have very well-ordered structures characterized by parameters close to those of the coke from the single Zofiówka coal reaching, dependently on a given factor, up to 80–99% of the values obtained for the coke from this strongly-caking coal. Values of SMOD were also related to the technological indices of the cokes studied. Generally, the highly organized microtexture of the coal blend cokes was found to affect the CRI index: the lower is the value of SMOD in the coke, the higher its CRI.

Correlation between the Roga index and the free-swelling index of coal

Literature data on the properties of fractions of different density obtained by liquid centrifuging of metamorphic coal reveal the relation between the Roga index RI and the free-swelling index SI, which describe different aspects of clinkering. A correlation is obtained between RI and SI, whose characteristics depend on the metamorphic stage of the coal. The results suggest that RI should be replaced by SI in dividing coal with a plastic-layer thickness y < 6 mm (D, SS, and TS coal) into subgroups, within the framework of the unified coal classification (State Standard GOST 25543-88).

The Physical Parameters of Different Rank Coals Related To Their Degree of Cross-Linking and the Caking Ability

Physical parameters such as true density, porosity, ultrasonic velocity, dynamic elastic modulus, spin concentration, widths of the Lorentzian EPR lines, and maximum optical reflectance were determined for 15 coals of a wide rank and of a wide caking ability. Coals were characterized by carbon content ranging from 83.1 to 94.9 wt % C and by the Roga Index (RI) in the range of 0−76. Single monolithic blocks of these coals were applied for production of the single-coal cokes in the Jenkner's retort furnace. The same physical properties as for coals were also studied for cokes. The physical parameters studied were discussed in relation to the degree of cross-linking and the caking ability of coals. Cokes were found to be characterized by the higher degree of cross-linking than those of initial coals, except for the cokes from the lowest rank coals. The Roga Index was found inversely proportional to the degree of cross-linking of coals. The lowest cross-linked coals exhibited the highest RI values. Optical reflectance was found independent of the degree of cross-linking, unlike the EPR parameters. Both spin concentration and the width of the EPR lines determined in coals decreased with increasing molecular weight per cross-linked unit (Mc). It was found that cokes produced from coals with RI values between 40 and 55 were characterized by elastically isotropic structure.

Elastic and Optical Anisotropy of the Single-Coal Monolithic High-Temperature (HT) Carbonization Products Obtained on a Laboratory Scale

The aim of the present study was to investigate the directional dependences of the elastic and optical properties of monolithic single-coal high-temperature (HT) carbonization products obtained on a laboratory scale (with very slow heating rate) from coals of different caking propensity. Sixteen monolithic HT carbonization products, mainly cokes, were produced in the Jenkner retort furnace using 16 various types of coals of varying rank (from 83.1 wt % carbon to 98.3 wt % carbon) with a Roga index (RI) in the range of 0−76. Coals were carbonized in the form of monolithic blocks. The physical parameters such as true density, porosity, ultrasonic velocity, and dynamic elastic moduli, as well as optical reflectance parameters (Rmax, Rmin, Ram), were determined for the resultant products. The elastic and optical properties of the HT carbonization products were related to their porosity and the rank of the parent coals. It was determined that the HT carbonization products exhibit the different directional prop...

Monitoring of connection between adjacent wells in hydraulic treatment of coal beds

The caking properties of nine bituminous coals were measured after their soluble parts were extracted with mixed solvents. The extraction yields of the soluble components could be arbitrarily controlled up to ≈60 wt% at room temperature by varying the composition of the mixed solvents. The variations of the crucible swelling number (CSN) and Roga index with the extraction yield were classified into four patterns. Pattern 1: both CSN and Roga index decrease rapidly with extraction yield; i.e. all the soluble parts act as ‘caking components’. Pattern 2: CSN and Roga index remain constant for ≈10 wt% of extraction yield, followed by rapid decreases. Pattern 3 (Shin-Yubari coal): CSN is invariant with extraction yield; even after low molecular weight materials are extracted, caking components may be produced from the residue during heat treatment. Pattern 4 (Zao Zhuang coal): CSN increases with extraction yield up to 28% and then begins to decrease. The presence of a maximum CSN, and the observations for Gieseler fluidity, suggest that there is an optimum fluidity for swelling character. Soxhlet extraction with chloroform revealed that the chloroform soluble substances, which have often been regarded as ‘caking components’, in fact form only a fraction of the caking components.

96/01276 Manufacture of high-quality coke for blast furnaces

The caking ability sets coking coals apart from other coals. In the industry, the practice of blending coals with different physicochemical parameters is often used to obtain the fuel with the desired properties. Caking ability is a non-additive parameter, which means that it cannot be calculated from the weighted average of the components of the blend. In this study, a model for predicting the caking ability of coal in blends was developed, based on the XGBoost regressor machine learning method. Experiments involving blending eight coals in five different proportions were carried out to obtain a training dataset. The coals were selected to reflect the widest possible range of types and caking ability levels. The Roga Index (RI) was chosen as a measure of caking ability. The experiments proved the non-additivity of caking ability of coal in blends, in particular for low-rank coals and good quality coking coals. The Feature Importance and Partial Dependence Plots techniques were used to determine the impact of model input parameters on the predicted value. Our study demonstrated that the carbon, moisture, volatile matter and vitrinite contents had the greatest impact on predicted RI. The prediction efficiency of the model was R2 = 0.95, confirming the effectiveness of the method used.

The influence of extraction with organic solvents on coking properties of raw and reduced coals

The dilatometric properties and Roga index of two orthocoking coals, subject to extraction with n-pentane, methylene chloride and chloroform, were determined in order to investigate the influence of low-molecular weight substances on coking properties of the coals. With increasing extraction yield, their dilatation and agglomerating capacity were observed to decrease, whereas their softening point was shifted towards higher temperatures. The effect of reduction by potassium in liquid ammonia on dilatometric properties of coals, as well as on their agglomerating capacity, was also studied. This reduction was found to cause a significant increase in coal dilatation, a decrease in softening temperature of the coals, and an insignificant increase in their agglomeration capacity. The extracts obtained from raw and reduced coals are characterized and their role as well as the role of the reduction process in the phenomenon of coal plasticity is discussed.

Effect of petroleum residue addition on the carbonization of non-coking coals

The effect on the carbonization process of the addition of petroleum vacuum residue to brown and bituminous coals was studied. The Roga index increased by no more than a few units. The coke yield increased in the lower-temperature range but decreased in the higher-temperature range. The positions of the minima in the DTA curves were shifted.

Caking properties of coal residues after extraction with mixed solvents

The caking properties of nine bituminous coals were measured after their soluble parts were extracted with mixed solvents. The extraction yields of the soluble components could be arbitrarily controlled up to ≈60 wt% at room temperature by varying the composition of the mixed solvents. The variations of the crucible swelling number (CSN) and Roga index with the extraction yield were classified into four patterns. Pattern 1: both CSN and Roga index decrease rapidly with extraction yield; i.e. all the soluble parts act as ‘caking components’. Pattern 2: CSN and Roga index remain constant for ≈10 wt% of extraction yield, followed by rapid decreases. Pattern 3 (Shin-Yubari coal): CSN is invariant with extraction yield; even after low molecular weight materials are extracted, caking components may be produced from the residue during heat treatment. Pattern 4 (Zao Zhuang coal): CSN increases with extraction yield up to 28% and then begins to decrease. The presence of a maximum CSN, and the observations for Gieseler fluidity, suggest that there is an optimum fluidity for swelling character. Soxhlet extraction with chloroform revealed that the chloroform soluble substances, which have often been regarded as ‘caking components’, in fact form only a fraction of the caking components.

Significance and application of the caking index of coal — Ten years' review

The Caking Index, G, has been widely popularized and applied in coal geological exploration, production and utilization departments in China. This index was established after improving the Roga Index, an international method used for determining the caking power of bituminous coal. It has become one of the main indices to classify bituminous coals in the new classification of Chinese coals. The value of G characterizes the content of active component of coal, and is considered as a measure of the degree of reduction of coal. The method using a plot of the volatile matter content ( V, d.a.f.) vs. G can predict the coke strength and permits selection of the best economic coal blending ratios. The additive property of G values and the interchangeability of coal types in coal blending for coking are discussed.

溶媒抽出後の残さ炭の粘結性

Caking property, such as Roga index and crucible swelling number, of the residual coals from the extractions was measured. The extractions were done using 1: 1 mixtures of carbon disulfide with pyridine, N, N-dimethylacetamide, and N-methyl-2-pyrrolidone, respectively. The following results were obtained.1) Roga indexes of residual coals from the extraction with the mixture were higher than those for the Soxhlet extraction with pyridine, in similar extraction yield. This may be attributed to a slight oxidation in Soxhlet extraction, since careful air removal from the Soxhlet apparatus gave similar high Roga indexes with those for the extractions with the mixture.2) In the extractions of Shin-yubari and Zao Zhuang coals with the mixtures Roga indexes of both residual coals decreased with increasing extraction yields. Zao Zhuang coal showed pronounced decrease in Roga index than Shin-yubari coal. This indicates that both coals are different from each other in chemical structures, molecular weight distributions, and degrees of cross-linking, although they have similar carbon content (%)

乾式脱硫脱硝用活性コークスの製造に関する研究

Since the dry process for the simultaneous removal of SOx and NOx in the flue gas requires the coke of high mechanical strength, catalytic and adsorption abilities, its preparative procedure was studied . Such a coke has been successfully prepared through the consecutive steps which are fluidized coking of coal into semi-coke, formed coking of semi-coke with coal and soft pitch, and the activation with steam. The optimum conditions for the respective steps were studied to reveal the following conclusions.1) The optimum temperature of fluidized coking was between 480-500 t, semi-coke of highest surface area being obtained.2) Control of the mechanical strength of the active coke can be carried out using the Roga index of the blends.3) The carbonization temperature influenced the strength and reactivity of the coke in a contrary manner, 800°C appearing optimum.4) The activation increased to surface area but reduced the strength of the active coke. The treatment at 900°C for 40 min gave temporarily the best result.SOx adsorption and the catalytic activity for NOx reduction.

Effects of phenol on the properties of pitch produced thermally from the petroleum vacuum residue

A petroleum vacuum residue was thermally treated at 430 °C, with continuous addition of phenol to either the vapour phase or the liquid phase of the reacting system. Addition of phenol to the vapour phase increased the yield of the cracked oil and the fixed carbon of the residual pitch. When phenol was charged to the liquid phase, the yield of the oil remained unchanged, but the amount of the benzeneinsoluble matter in the pitch decreased, probably owing to the inhibition by phenol of the polymerization-condensation reactions of aromatic compounds. In both additions the cracked oil had a higher boiling point than that produced without phenol. Substitution of phenol with methyl groups increased the extent of cracking and coking properties (Roga Index) of the pitch. The effective order of phenol and its derivatives is: Phenol < m-Cresol < o-Cresol < p-Cresol < 2, 4-Dimethylphenol < 2, 6-Dimethylphenol < 2, 4, 6-Trimethylphenol Polyhydric phenol, e.g. catechol, and naphthol also enhanced the cracking reactivity of the residue.