Non-coking Coal Research Articles

Influence of the prime hard coking coal in stamp charge cokemaking: true or false

The production of hot metal through the blast furnace route is stilled the most cost-effective and highly productive process and probably remains the coming decades besides developed many alternative ironmaking technologies. In the recent past, the working volume of the blast furnace has been increased drastically to increase the blast furnace productivity. This means the blast furnace performance is more correlated to specific productivity which measures the efficiency in terms of ton hot metal. These modern blast furnaces favour high quality of coke, i.e. high coke CSR and M40 value, high iron content sinter and pellets. These high quality of input raw materials increased blast furnace efficiency and productivity. Generally, cokemakers increases the ratio of prime hard coking coal in the coal blend to achieve the high quality of coke. This increase in prime hard coking coal is not desirable for coke oven batteries because it creates high oven wall pressure and high coke cost and also not suitable for raw material security. The present investigation highlights few cases which clearly show that the high quality of coke (coke CSR: 69–71) may be easily produced with the optimal proportion of prime hard coking coal in the blend if the selection of coals is proper. Results confirmed that upto 30% primary hard coking coal with 15% non-coking coal in the coal blend produce an excellent quality of coke which naturally requires a careful selection on the blend component. The optimum composite coking potential (CCP) value of 4.6–4.9 is the ideal value for producing coke CSR in the range of 69–71 in recovery stamp charge cokemaking process in the real-time plant operation. Therefore, it is necessary to select the right coals for the coal blend based on the adopted cokemaking technologies to conserve the reserve of prime hard coking coal, oven health and cost-effectiveness.

Use of organic polymers for improvement of coking potential of poor coking coal

ABSTRACT As the reserve of prime coking coal is low, there is a good amount of research going on worldwide to improve the coking potential of non-coking coal. Researchers have revealed the importance of hydrogen generation/transfer to improve the coking potential of coal. Based on this hypothesis, in this paper, the authors have tried to improve the coking potential of non-coking coal by adding different polymers. The polymers are derived from formaldehyde and phenol derivatives. Coking potential has been tested through conventional tests like crucible swelling number. Thermogravimetric mass spectroscopy (TG-MS) has been used to get an idea of plasticity and hydrogen generation in the plastic zone. High-temperature microscopy has also been used to evaluate the swelling of coal. Results indicate that the addition of polymers in a small percentage has an effect on hydrogen generation in the plastic zone, and thus, it can improve the coking potential of non-coking coal.

Difference in structural chemistry of non-coking and coking coal using acid treatment demineralization technique

ABSTRACT Recently, the structural information about non-coking and coking coal has attracted pronounced interest for sustainable utilization of poor coking coal in different industries specifically for steel industry like Tata Steel. In the present work, demineralization techniques via acid treatment (HCl-HF) are effective to remove mineral phase from coal. The difference in carbon chemistry of non-coking (CDPCI), weakly coking (Curragh SS), and prime coking coals (Illawarra and Jamadoba) has been studying through advanced characterization methods like petrography, TGA-DTG, FTIR spectroscopy, X-ray diffraction, Raman, 13C solid-state NMR, FESEM, and TEM. These advanced characterization techniques offer comparative structural information of different coal through the distribution of individual coal maceral and mineral grains with their rank (petrographic study), functional group study along aliphatic-aromatic structural relationship measurement (FTIR), crystalline/graphitic nature of carbon (XRD & Raman) with oxygenated carbon skeletal structural information (Solid State 13C NMR), aromatic-aliphatic cross-linking behavior (FESEM) and their orientation toward lattice fringe structure (TEM).

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.

Numerical investigation of the combustion process for design and non-design coal in T-shaped boilers with swirl burners

In this paper, we present the results of a numerical investigation into the combustion process in a boiler furnace chamber with swirl burners using design coal (non-coking coal) and substitute coal (coking coal). The paper describes the development of a three-dimensional combustion model for coal burning in a boiler furnace chamber. The utility boiler operates on high-ash non-coking coal with an ash content of 41.94%. Due to the high ash content in the design coal, most of it is released into the atmosphere, which negatively affects the environment and the surrounding area. We suggest that this coal by a different coal with a lower ash content. It was found that during the combustion of substitute coal at the level of burner, the temperature in the entire cross section increases by 200 K, due to more intense fuel burnout at the outer boundary of the burner torches. It is found that the substitute coal may be burned in the boiler furnace chamber and can provide reliable operation if the swirl burner angle is set at 50° for the secondary air and at 45° for the fuel-air mixture.

Formation of Metallurgical Coke within Minutes through Coal Densification and Microwave Energy

This paper shows how feedstock densification gives rise to a step change in the time required to create a metallurgical grade coke using microwave energy. Five densified coking and noncoking coals ...

Microwave-assisted and analytical pyrolysis of coking and non-coking coals: Comparison of tar and char compositions

Pyrolysis conditions and mechanism greatly influence the quality of tar and char from coal, which eventually determine their further usage. This work investigates the pyrolysis of three coking coals and a non-coking high ash Indian coal via microwave-assisted and conventional heating, and the influence of heating rate, coal type, and heating mechanism on product yields and tar composition. Microwave pyrolysis experiments were conducted in a home-built microwave reactor, and analytical pyrolysis experiments were conducted in a Pyroprobe® interfaced with gas chromatograph-mass spectrometer (Py-GC/MS). The tar yields from microwave pyrolysis of coking coals were similar (∼7 wt.%), while it was slightly high from high ash Indian coal (∼11 wt.%). Char yields from both microwave and analytical pyrolysis were similar (78 ± 1.5 wt.%). Microwave pyrolysis tars were rich in naphthalene derivatives and polyaromatics with more than 45% selectivity, while analytical pyrolysis tar was rich in monoaromatics (>30%). There was no significant variation in the selectivities of other organic fractions. High selectivity of polyaromatics in microwave pyrolysis tar is due to the generation of localized hotspots, which led to excessive cracking of primary pyrolysis vapors. The higher heating value (HHV) of microwave pyrolysis tar was 32–33 MJ kg−1, while that of analytical pyrolysis tar was higher (35–36 MJ kg−1), which is attributed to the presence of more monoaromatics in the latter. Hydrogen and methane were the major components in the gaseous fraction. Coal chars were characterized using different techniques, and they were rich in carbon (≈80 wt.%) with high energy content (29 MJ kg−1).

Structural characterization of coking component of an Indian coking coal

Coking coal is used for coke making owing to its inherent swelling and thermoplastic properties. Non-coking coal on the other hand lacks these coking properties and hence coke making from non-coking coal is a challenging task. In the present study, we isolated the “coking component” present in an Indian coking coal by density separation followed by solvent extraction method and elucidated its chemical structure using XRD, Raman, XPS, FT-IR, NMR and mass spectrometry techniques. The coking component was found to have turbostatic graphitic structure similar to that of expandable graphite. Finally, we synthetically induced coking properties in four non-coking coals of Indian origin using expandable graphite and molasses following a simple heat treatment process. The resultant modified coal produced G1-G2 grade coke in low temperature Gray King (LTGK) assay.

Utilization of low-grade BHQ iron ore by reduction roasting followed by magnetic separation for the production of magnetite-based pellet feed

Due to the depletion of high-grade iron ores and their simultaneous demand, the utilization of low-grade iron ores such as banded hematite quartzite (BHQ) has become a topic of research interest around the globe, particularly in India. These low-grade iron ores are reckoned to be the future feedstock for iron and steel making industries. However, one of the major challenges is to remove associated gangue impurities from such low-grade iron ores by the conventional beneficiation techniques prior to its industrial applications. The reduction roasting process is one of the potential alternatives to overcome such challenges. Herein, we have presented the feasibility study using reduction roasting process on one of the Indian low-grade BHQ iron ore for the preparation of magnetite concentrate-based pellet feed materials. To establish the methodology of the reduction roasting process, different experimental parameters such as roasting temperature, reductant dosage, roasting time and fixed carbon were optimized for obtaining the maximum recovery, yield, and grade of the magnetite products. In the present study, Indian non-coking coals were used as reductant due to its large availability in the country. Using one of the non-coking coals as reductant, the optimum condition were found to be as, roasting temperature: 1100 °C, roasting time: 5 min, and head sample to reductant ratio: 10:6. Under these conditions, maximum grade and recovery of final magnetite concentrates were found to be 66.42 and 93.53%, respectively. It is expected that the large-scale development of reduction roasting process would lead to effective utilization of low and lean grade iron ore resources for the production pellet feed materials in the Indian context and simultaneously conserve the natural magnetite ores for future generation.

Revision of country specific NCVs and CEFs for all coal categories in Indian context and its impact on estimation of CO2 emission from coal combustion activities

This paper highlighted the need for periodic change in country specific NCVs and CEFs of solid fuels. Accepted India specific NCV/CEF values of coking coal, non-coking coal and lignite were worked out during the India’s Initial National Communication’2004 taking 1994 as the base year. Those values continued to be in use in CO2 estimations done by sectoral/national/international agencies and also in estimations related to India’s Second National Communication’2012 to UNFCCC. In present investigation fresh estimations taking base year as 2007 were done considering large numbers of relevant post 2006 coal-quality data for each Indian coal category and as a result NCV of non-coking and coking coal diminished by 6.6% and 2.1% respectively. The changes happened due to cumulative effect of slow changing quality of coking, non-coking coals and their grade-wise production pattern over the years. Using new NCV-CEF values, reduction of CO2 emission by 53.4 Tg, solid fuel (coal and lignite) emission by 5.4%, total fossil fuel emission by 3.8%, sectoral emissions by 2.7%–5.9% were observed. The relevance of new NCV-CEF values were examined in present context and the new values should be used for accurate estimation of CO2, which indicates energy efficiency and clean use of coals.

Water catalyzed pyrolysis of oxygen functional groups of coal: A density functional theory investigation

The pyrolysis mechanism of carboxylic and hydroxyl groups which are present in the coal has been investigated with the help of density functional theory calculations. The role of water in the pyrolysis reaction mechanisms has also been investigated by the calculation of activation energy barriers. The activation energy barriers for the water mediated reactions are less when compared to thermal pyrolysis process. The results show the significant decrease in the energy barriers for decarboxylation reactions than the hydroxyl groups in the presence of water. Therefore, water can significantly decrease the oxygen content in the non-coking coals with high content of carboxylic groups.

Understanding the unusual fluidity characteristics of high ash Indian bituminous coals

High-temperature rheometry and 1H nuclear magnetic resonance (NMR) are two complementary techniques that have been used to investigate fluidity development quantitatively in the <53 μm and 53–212 μm size fractions of high ash Indian non-coking coals and imported non-coking, medium coking and good coking coals. It was found for the 53–212 μm size fraction of the Indian bituminous coal with higher ash content (30 wt%) that, despite its high complex viscosity (>105 Pa·s), the maximum concentration of fluid H was quite similar to that of the good coking coal (40%). This Indian non-coking coal developed fluid H with the highest mobility (T2L > 150 μs) in the coal series, regardless of the particle size fraction studied. The probable explanation for this abnormal behavior is that the mineral matter prevents bulk movement in the sample but the local mobility of the fluid phase is still high on the nanometer scale. Blending the two Indian non-coking coals with the highly fluid medium coking coal gave higher viscosities (i.e. lower fluidity) than predicted by the polymer blend rule, probably again due to the high mineral matter restricting bulk flow. This negative effect was less pronounced with the higher ash coal suggesting that the high mobility of the fluid entities in this coal might prevent the destruction of fluid entities evolving from the medium coking coal. Partial demineralization of the high ash Indian non-coking coal to 17 wt% through a sink-float method did not decrease the complex viscosity of this coal but reduced the maximum mobility of the fluid H to levels observed with the lower ash content (20 wt%) Indian coal. Therefore, this reduction in mobility could be directly related to the mineral matter in the Indian non-coking coal.

Effect of Crusher Type and Crusher Discharge Setting On Washability Characteristics of Coal

Natural resources have been serving the life of many civilizations, among these coals are of prime importance. Coal is the most important and abundant fossil fuel in India. It accounts for 55% of the country’s energy need. Coal will continue as the mainstay fuel for power generation. Previous researches has been made about the coal feed size and coal type had great influence on the crushing performance of the same jaw crusher and amount of fines generated from a particular coal depends not only upon coal friability but also on crusher type. Therefore, it necessitates crushing and grinding the coal for downstream process. In this paper the effect of crusher type and crusher discharge setting on washability characteristics of same crushed non-coking coal has been studied. Thus four different crushers were investigated at variable parameters like discharge settings, different capacities and feed openings. The experimental work conducted for all crushers with same feed size and HGI (Hardgrove Grindability Index). Based on the investigation the results indicate that the four crushers which has been involved for the experimental work shows that the variation in not only the product size distribution and also reduction ratio. Maximum breakage has been occurred at coarsest size fraction of irrespective of crusher type and discharge setting.

Utilisation of low-grade raw materials for preparation of reactive catalysed-coke for blast furnace application

ABSTRACTIn this work, a method for producing highly reactive catalysed coke from medium and non-coking coal using low-grade iron ore fines as a catalyst through two different alternate routes, namely carbonisation in a stamp charge coke oven and carbonisation in a horizontal tube furnace was attempted. Phenolic resin and petroleum pitch were individually experimented as a binding material to get adequate strength. Effect of process parameters such as coal-to-iron ratio, briquetting load, binder quantity and coking to non-coking coal ratio on the coke properties such as reactivity and mechanical strength was investigated. The SEM and petrography analysis of catalysed coke were used to study the microstructure and its effects on reactivity.

Chemical Beneficiation of High-Ash Indian Noncoking Coal by Alkali Leaching under Low-Frequency Ultrasonication

Coal mined from the Talcher region of Odisha, India is known to be high-ash, surface-oxidized, and noncoking in nature. It is quite challenging to beneficiate such low-grade coal by physical or physicochemical processes due to its oxidized nature and the presence of complex ash forming mineral matter in its matrix. Chemical beneficiation is one of the alternative process to such problems. However, this chemical process consumes more chemicals, treatment time, and energy, which limits its application further. Therefore, an attempt has been made to chemically beneficiate this coal cost-effectively with optimum chemicals, treatment time, and energy. In the present study, an application of ultrasound at low frequency on alkali-acid leaching is employed to investigate on the demineralization of high-ash Indian noncoking coal. The raw coal properties such as fixed carbon content, CHNS content, Hardgrove grindability index, ash fusion temperature, and gross calorific value (GCV) were investigated before the expe...

Enrichment of reactive macerals in coal: its characterization and utilization in coke making

Macerals in coal are of different types: reactive and inert. These macerals are differ in their physical and chemical properties. Column flotation method has been used to separate the reactive macerals in a non-coking coal. The enriched coal is then characterized in order to understand the changes in the coking potential by different techniques. It is then used in making of metallurgical coke by proper blending with other coals. Enriched coal enhance the properties of metallurgical coke. This shows a path of utilization of non-coking coal in metallurgical coke making.

Experimental determination of the strength and reactivity of lumpy and briquetted chars from non-coking coals under melter-gasifier conditions

ABSTRACTWith the advent of alternative smelting-reduction processes of ironmaking like COREX® and FINEX®, the demand for non-coking coals as a major raw material has increased. In these processes, char is formed from non-coking coals inside the melter-gasifier (MG) by pyrolysis. This char, either in lumpy or briquetted form, is the major reductant and fuel of the smelting-reduction process. Just like the coke in blast furnace, the char should also have certain chemical and mechanical properties suitable for operational requirements of the MG. However, there is a lack of systematic works related to the properties of chars from non-coking coals for ironmaking. This work aims to define a standardised testing method to determine the reactive and mechanical properties of lumpy and briquetted chars comparable to existing ISO norms. It also demonstrates the effect of different operational conditions on char properties. The testing method described in this work should be useful to the industry personnel to evaluate the quality of chars from non-coking coals for their usage in the MG.

Thermoplastic development of coking and non-coking maceral concentrates and molecular weight distribution of their pyrolysis products

A suit of nitrogen-dried maceral concentrates derived from a coking coal and a non-coking coal was investigated to reveal the impact of varying coal main organic constituent, the vitrinite, on their thermoplasticity and pyrolysis products. The thermoplastic development of maceral concentrates during pyrolysis was evaluated via their thermo-swelling and dynamic volatile release. These measurements were then linked to molecular weight distributions of vaporised tars and tetrahydrofuran (THF) extracts obtained from heat-treated samples. Regardless of the vitrinite content, only coking macerals agglomerated during pyrolysis while non-coking macerals retained their powdered structure. This result indicated that although concentrating the vitrinite could alter the extent of coal thermoplasticity, such process could not grant or remove thermoplasticity from a maceral concentrate. This was reflected in the similar molecular weight distribution of solvent extracts produced between the parent coals and their concentrates. In specific, coking concentrates generated extractable materials with a relatively more complex structure, consisting of a bimodal molecular weight distribution with 12–14Da repeating structures at <600Da and 24Da reoccurring units between 600 and ∼1500Da. Solvent extracts isolated from non-coking concentrates, on the other hand, possessed a unimodal molecular weight distribution with only 12–14Da repeating structures extending to ∼800Da. The absence of high-range molecular weight materials (the 24Da repeating units) in non-coking coal and its concentrates was speculated to play a vital role to their inability to exhibit thermoplastic behaviour during pyrolysis.

Economical and Energy Efficiency of Iron and Steel Industry Reindustrialisation in Russia Based on Implementation of Breakthrough Energy-Saving Technologies

Estimates were given of economical and energy efficiency of breakthrough energy-saving technologies, which increase competitive advantages and provide energy efficiency of production while reducing negative impact on the environment through reduction of emissions of harmful substances and greenhouse gases in the atmosphere. Among these technologies, preference is given to the following: pulverized coal fuel, blast-furnace gas recycling, gasification of non-coking coal in bubble-type gas-generators, iron-ore concentrate briquetting with steam coal with further use of ore-coal briquettes in electric furnace steel making. Implementation of these technologies at iron and steel works will significantly reduce the energy intensity of production through reduction of expensive coking coal consumption by means of their substitution by less expensive non-coking (steam) coal, and natural gas substitution by own secondary energy resource, which is the reducing gas. As the result, plants will get an opportunity to become self-sufficient in energy-resources and free themselves entirely from expensive purchased energy resources (natural gas, electric power, and partially coking coals), and cross over to low-carbon development.

ENERGY VALUE IN BIOMASS AND PLASTIC COMPONENTS OF MUNICIPAL SOLID WASTE

Burning potencies of constituents of municipal solid waste (MSW) indicate energy value stored in them. A significant portion of biodegradable as well as non-biodegradable waste is still80 not recycled and most of them are either burnt or dumped in the landfills. The scope of this work is to study the energy value of selected biomass (dry garden leaves) and two plastic materials, low density polyethylene (LDPE) and polystyrene (PS), collected from an educational campus in Varanasi, India. Cow dung which is still used as domestic fuel in dry cake form in many parts of the country, has also been included. Two pellet batches of biomass, one each of Ashoka (Saraca Asoca) tree leaves and Cow dung, two pellet batches of plastic, one each of low density polyethylene (LDPE) and polystyrene (PS); and twelve biomass-plastic blended pellets have been prepared and tested. Proximate analyses and higher heating values (HHVs) were measured and compared with the gross calorific values (GCVs) of various grades of Indian non-coking thermal coals. The results indicate that on blending of biomass materials with plastics in 1:1 ratio, the HHV of mix exceed GCV of grade A non-coking coal. A 2:1 ratio gives material with heating values higher than grade C coal. Other tested mix proportions also produced heating values exceeding D grade coal. Thus, it appears feasible to produce secondary fuel using components of MSW for domestic consumptions. This is a non-conventional and renewable source of energy. This may partly reduce the dependence on fossil fuel (like coal) and provide an alternate reuse pathway for such materials. Article DOI: https://dx.doi.org/10.20319/mijst.2017.32.8092 This work is licensed under the Creative Commons Attribution-Non-commercial 4.0 International License. To view a copy of this license, visit http://creativecommons.org/licenses/by-nc/4.0/ or send a letter to Creative Commons, PO Box 1866, Mountain View, CA 94042, USA.