Lump Coke Research Articles

Substituting natural gas with hydrogen: A case study on mass, energy, and emissions in electric arc furnace steelmaking

This study sets out to explore the use of hydrogen into steelmaking via the electric arc furnace route, weaving together technoeconomic analysis with a comprehensive carbon footprint assessment. Through a detailed examination, we scrutinize the financial prospects of integrating hydrogen within a scrap-based steel mill, using Liberty GFG's data for a case study. Based on the data, the steel plant's annual consumption is 1.2 million GJ/y of energy, primarily derived from natural gas, to produce 0.75 million tonnes of steel. We explore the potential of replacing this natural gas with 10-kilotonnes of hydrogen per year (1.35 t/h), considering the steel mill's capacity factor of 0.82. By employing sophisticated flowsheet-based calculations, we unravel the environmental implications of integrating hydrogen into the steelmaking process. The investigation reveals that the plant consumes 2.9 GJ per tonne of steel from natural gas, indicating a demand of 23.5 kilograms of hydrogen to completely supplant natural gas. This equates to 2.35 kilograms of hydrogen per tonne of steel for every 10% displacement of natural gas. At present, the comprehensive cost of employing hydrogen stands at US$ 144 per tonne of steel, predicated on a wind electricity price of US$ 38 per MWh. In contrast, utilising natural gas amounts to US$ 58 per tonne of steel. However, the horizon holds promise for a substantial reduction in hydrogen costs over the next decade, heralding a potential paradigm shift in its utilisation. The emission analysis shows that the plant produces greenhouse gas emissions of 735 kgCO2e/t steel, out of which 70% is due to the use of dominant fossil electricity and the rest 30% (223 kgCO2e/t steel) from other carbon sources such as natural gas, lump coke, coke fines, and diesel fuel. Modeling proposes that a complete substitution of grid electricity and natural gas would lead to process emissions totaling 104 kgCO2e/t steel. To achieve a net-zero emission target, a strategic shift is suggested: replacing lump coke and coke fines with biochar. This substitution not only eliminates lifecycle emissions but also paves the path towards realising a sustainable, carbon-neutral future.

A novel method of combined desulfurization and heat utilization of low-temperature flue gas from hot blast stove for blast furnace: Laboratory research and industrial application

To address the challenges of low waste heat utilization rates and high desulfurization costs, this study proposes a novel method for combined desulfurization and heat utilization of low-temperature flue gas. By utilizing the low-temperature flue gas from hot blast stoves to dry lump metallurgical coke, the method also achieves flue gas desulfurization during the lump coke drying process. During the drying process, the wet lump coke desulfurizes due to the reaction between water vapor in the lump coke and the SO2 and oxygen in the flue gas, resulting in the formation of sulfuric acid. Additionally, the coke powder generated by friction during the drying process of lump coke has a large specific surface area, enabling it to adsorb additional quantities of SO2 and enhance the desulfurization process. It's important to note that the lump coke itself does not exhibit adsorption properties towards SO2 during the drying process, and the gas is not retained within the lump coke. Industrial applications indicate the outlet flue gas temperature is reduced from 175 °C to 60 °C, and the concentration of SO2 in the outlet flue gas is reduced from 150 mg/m3 to 29 mg/m3.

Reduction smelting of ore-coal iron ore raw materials without carburization

Dedicated to grandfather and father Tleugabulov Suleiman Mustafievich and Tleugabulov Boris SuleimanovichWith the traditional method of processing cast iron into steel, a sufficiently large amount of finely dispersed iron-containing waste is formed at each stage, which represents secondary raw material resources. The use of them in small quantities as part of the agglomeration charge has no practical importance. Therefore, the development of technology for their mass metallurgical processing is a problematic task of a global scale. This present work is devoted to the solution of this problem. The processes of direct reduction of metals by solid carbon on the basis of new theoretical positions of dissociation-adsorption mechanism (DAM) open the way to effective processing of dispersed metal-containing industrial waste – converter and blast furnace sludge. Converter sludge represents a significant part of metal-containing industrial waste with a high concentration of iron. When organizing the process of charge preparation from the dispersed components of the charge (ore part and coal) and their uniform mixing, a developed contact surface is achieved. Unlike coke metallurgy, which is based on the preparation and use of a charge consisting of a lumped ore part and lump coke. When such a charge is loaded into the furnace, the chemical reaction between metal oxides and solid carbon is practically unable to proceed in a solid-phase state due to the limited contact surface between them. The pelletizing of a finely dispersed mixture will allow to obtain a mono-charge and to realize the process of reducing melting of the monocharge. In this work, the technology of one-stage reduction smelting of prepared ore-coal raw materials has been developed and proposed. At the same time, it is possible not only to dispose of the generated waste of metallurgical production (converter sludge), but also to recover the metal without its excessive carburization. In doing so, the final product of this processing scheme is naturally - alloyed steel without loss of valuable elements during the oxidation period.

Potential of Alternative Organic Binders in Briquetting and Enhancing Residue Recycling in the Steel Industry

Steel production generates various types of residues that cannot be directly recycled in the production process without pre-treatment and agglomeration. In the present study, recipes were designed to develop briquettes in a blast furnace (BF) with the partial replacement of cement with alternative commercial organic binders, including molasses–lime, bitumen, keracoal, carboxymethyl cellulose, and wood tar. The briquettes were produced using a technical-scale vibrating machine and the mechanical strength was evaluated using drop test and standard tumbler index results. The reduction behaviour was investigated by thermogravimetric analysis (TGA) coupled with QMS. A heat and mass balance model (MASMOD) was used to evaluate the potential of developed briquettes to reduce the energy consumption and CO2 emissions from the BF. Although cement was superior in developing mechanical strength, bitumen was the best among the other alternative organic binders and provided sufficient strength to the briquettes at 2.0% addition, which corresponded to 18.2% replacement of total cement. The briquettes containing bitumen possessed a higher reduction rate and lower activation energy compared to cement. The MASMOD calculation demonstrated that the developed briquettes have the potential to provide annual savings of 15,000–45,000 tons of lump coke, 4500–19,500 tons of CO2 emissions, and 5000–20,000 tons of limestone in Swedish BFs.

Effect of Changes in Mechanical Properties of Coke Matrix Caused by CO<sub>2</sub> or H<sub>2</sub>O Gasification Reaction on the Strength of Lump Coke

In this study, we evaluated the effect of the CO2 or H2O gasification reaction on the mechanical property of the coke matrix by measuring the elastic modulus of the coke matrix before and after the gasification reaction. We also investigated the effect of the distribution of the elastic modulus in the coke matrix on the strength of the lump coke by conducting the fracture analysis for the coke model with porosity of 0–0.4 in which the distribution of the elastic modulus obtained by the experiment was reflected. The nanoindentation measurements of the elastic modulus of the coke matrix before and after the gasification reaction implied that the distribution of the elastic modulus in the coke matrix differs depending on the gasification agent. In the case of the CO2 gasification reaction, both the coke matrices with high and low elastic moduli were consumed by the gasification. On the other hand, in the case of the H2O gasification reaction, only the coke with an elastic modulus of over 30 GPa before the reaction was consumed by the gasification reaction. Also, the numerical results showed that the distribution of the elastic modulus in the coke matrix affects the strength of the coke model with low porosity whereas the one did not affect that with high porosity.

Attempts to replace nut coke with semi-coke for blast furnace ironmaking

Low coke rate for blast furnace operation has been required in response to the rising cost of coking coals. To extend the utilisation of coal resources, semi-coke has been introduced to blast furnace ironmaking process in recent years, however, there are still many issues unclear about the effect of semi-coke on ironmaking process. In this study, the possibilities of using semi-coke as alternative fuel for nut coke were studied. The characteristics of semi-coke including mechanical strength, high-temperature strength/reactivity, carbon gasification as well as direct reduction were studied and compared with small size metallurgical cokes (nut cokes). The results showed that semi-coke has higher CRI values, especially at higher temperatures and in a mix-charging pattern. Semi-coke was found to have a higher gasification reaction rate and depleted at lower temperatures. The reduction results showed that with participating of semi-coke the reaction starts at lower temperatures. In addition, the study suggested that semi-coke exhibits the advantages of low ash and sulphur contents, although it has lower mechanical strength, it would protect the lump coke by shifting the carbon gasification to itself, therefore, mixing semi-coke would benefit the blast furnace operation and lower the coke rate.

Effect of Coke Breeze on Fissure Formation of Coke

It is known that mixing the particle of inert material such as coke breeze to blending coal increases the mean size of lump coke. The size of lump coke is changed by the fissure formation, and it is assumed that the shape of lump coke is also changed by this mechanism. Therefore, the fissure formaiton of coke was investigated using the Gaudin-Meloy-Harris size distribution function. The coke blended with the coke breeze had larger grain size compared to the coke without mix of the coke breeze. In addition, the α value, which is the characteristic value of the Gaudin-Meloy-Harris size distribution function, reduced, suggesting that the shape of lump coke after breaking may be distorted. Therefore, as a result of analyzing coke fissures, it became clear that a change occurred in the fissure formation of the coke. The simulation results showed that the voidage of the coke packed layer was increased by increasing the coke grain size or distorting the shape of lump coke. It suggests that the coke produced from coal with coke breeze may increase the voids in the blast furnace.

Influence of draff as coking additive on the quality of lump coke using non-baking coals

For the production of high-strength lump coke from non-baking coals the processing, agglomeration and gentle coking of the agglomerates are essential steps. In previous studies the influence of the processing regime and the briquetting and coking parameters were systematically analysed.The current investigations combined the intensive processing of German and Indonesian brown coals in a twin-screw extruder and a swing mill with the addition of 5 wt% draff as a coking additive. Briquetting the mixture of coal and draff leads to an increasing briquette compressive strength. This binding capability of the draff is probably caused by the denaturation of protein during the processing in the twin-screw extruder and the swing mill. The produced coke as well offers a high mechanical strength. During the coking process the protein and cellulose material could be partially converted to solid bridges between the particles causing a higher coke compressive strength.

РАЗРАБОТКА ТЕХНОЛОГИЧЕСКОГО РЕГЛАМЕНТА НАУГЛЕРОЖИВАНИЯ ЧУГУНА В 30-т КОВШЕ. ЧАСТЬ 1

The results of numerical simulation of the carbonization of low-carbon iron as a by-product of the production of titanium slag for the designed unit ladle-furnace (LF) installation as applied to the conditions of PJSC Zaporizhzhya Titanium-Magnesium Combine are presented. The technological regulations have been developed and a numerical study has been carried out on the carburization of metal in a 30-ton ladle at the LF. For the production of commercial pig iron, associated iron-containing waste is used. The purpose of the work is to identify factors of the influence of out-of-furnace processing on technology optimization. A numerical simulation was performed of the carburization technology of liquid low-carbon (up to 2% carbon) cast iron with lump (fraction up to 50 mm) graphite and coke introduced onto the surface of a ladle bath (excluding slag cover). The material and energy balances of the process were carried out, the properties of carburizing materials were studied, and the diffusion coefficient of carbon in a liquid metal was estimated. The results of studies of the hydrodynamic and thermal conditions in the bucket bath of the LF are estimated from the contour diagrams of the flow rates and temperature fields for different flow rates of argon supplied through the bottom and submerged tuyeres. The optimal fractions of carbon-containing materials were determined. It has been shown that treatment on LF with lump graphite requires a shorter duration (≈ 45%) compared with lump coke. To accelerate the process of diffusion dissolution of carbon, it is necessary to periodically (every 3 portions of 70 kg of graphite and coke) heat the melt to a temperature of 1520-1530 ° C. Injection of powdered graphite and coke contributes to a more efficient absorption of carbon and a decrease in the duration of the process (≈ by 1/3). Research continues in the direction of using flux-cored wire for carburizing cast iron at LF.

Influence of briquetting and coking parameters on the lump coke production using non-caking coals

In terms of transforming the energetic usage to the material usage of low-rank coals, the production of lump coke is a promising perspective. Therefore, two essential steps are necessary: Firstly, the processing and agglomeration of the non-caking coal is highly important, since they do not offer any baking capacity and thus the reachable quality of the coke is mainly set by the briquette quality. Secondly, to obtain high quality cokes the briquettes need to be coked using a well-adapted heating regime to ensure the gentle degassing of volatile matter with a minimum weakening of the briquette structure. The brown coal high temperature technology (BHT technology) developed in 1952 by Rammler and Bilkenroth was a milestone in coal conversion for brown coal but the coke strength was limited at that time. In current systematic studies, the lump coke quality of Lusatian brown coal and Indonesian brown coal was investigated varying the processing, briquetting and heating regime in laboratory scale. Those investigations should lead to a new processing and agglomeration technology to create lump coke from non-caking coals. The experiments varying the processing parameters of the coal showed that the briquetting of pre-granulated coal or pellets from a modified flat die press achieve the highest increase in briquette and coke quality. In the second step, the heating regime during pyrolysis was investigated. The results show, that the highest coke quality may be achieved using the Vollmaier regime. However, a single-stage heating regime with a heating rate of 2.85Kmin−1 shows promising results as well.

A Particle-Resolved CFD Model of the Combustion and Gasification Processes of Coke

With the aim of optimizing the processes near the tuyeres of a coke-fired cupola furnace, a mathematical model based on computational fluid dynamics was developed that takes into account the combustion and gasification processes of lump coke at the particle scale. Basic fluid mechanics equations were used for the modeling and were supplemented by additional transport properties. The main task was to define the equations with appropriate constants as well as specific sources and sinks that correspond to individual processes. To assure the accuracy of the calculated physics, the model was developed by simulating each single subprocess separately and comparing the simulation results with either well-known submodels or experimental results. Furthermore, the detailed flow around the particles was enhanced with mass and heat transfer, which requires the dynamic boundary layer to be resolved. Due to the high computational effort, the latter was one of the major challenges of this project. After the initial setup, the model was assessed using the simple geometry of a column of spheres as an example. The computed results showed the expected response to the boundary conditions and good agreement with experimental data from the literature.

Fissure formation in coke. 3: Coke size distribution and statistical analysis

A model of coke stabilization, based on a fundamental model of fissuring during carbonisation is used to demonstrate the applicability of the fissuring model to actual coke size distributions. The results indicate that the degree of stabilization is important in determining the size distribution. A modified form of the Weibull distribution is shown to provide a better representation of the whole coke size distribution compared to the Rosin–Rammler distribution, which is generally only fitted to the lump coke. A statistical analysis of a large number of experiments in a pilot scale coke oven shows reasonably good prediction of the coke mean size, based on parameters related to blend rank, amount of low rank coal, fluidity and ash. However, the prediction of measures of the spread of the size distribution is more problematic. The fissuring model, the size distribution representation and the statistical analysis together provide a comprehensive capability for understanding and predicting the mean size and distribution of coke lumps produced during carbonisation.

Determination of thermal histories of coke in blast furnace through X-ray analysis

A study has been undertaken to identify the source of coke fines sampled from the deadman area of the blast furnace. Using measurements of the coke crystallite dimension LC, it was established that some of the fines found in the deadman area of a blast furnace were not simply the degradation products of the lump coke in this area. The LC was measured using standard X-ray analysis techniques. The coke fines had a higher LC than the coke lump and therefore have experienced a higher maximum temperature than the associated coke lump. This finding has been interpreted as at least some of the coke fines found in the deadman area (lower temperature region) have been blown there from the raceway by the high velocity hot blast.

Co-Carbonization of Two Anthracites with a Fat Coal or Two Pitches

The blends of two anthracite powders (YQ and JC) with a fat coal (C4) or a petroleum pitch (PP) or a coal tar pitch (CTP) in different proportions were co-carbonized at 3°C/min up to 1000°C in an experimental 1 Kg coke oven. Coke yield, coke particulate size, coke micro-strength and coke cracking strength were measured respectively. Coke optical textures were watched under a microscope. The results show that as anthracite proportion increases, coke yields of all blends improve; > 0.8 mm lump coke yields of blends with CTP or PP decline slightly, blends with C4 drop heavily; coke micro-strengths do not change sharply, and coke cracking strength of blends with C4 or PP decrease more than blends with CTP. C4 produces fine-grained mosaics, and two anthracites are mainly fusinite and fragments, PP is coarse-grained mosaics, and CTP is chiefly flow or domain textures. Independent optical textures were observed in cokes. There exist evident borders between the two contact optical textures which were produced by different components, and a few phenomena that domain or flow textures penetrating into fusinite appeared in the blends. It seems that CTP is the best adhesives for blending with anthracites for producing high quality cokes.

未燃チャーと微粉コークスの高炉内挙動の同時解析

A mathematical model of blast furnace operation, which is able to estimate the behaviors of the unburned char and the fine coke simultaneously, has been developed. The model based on the multi-fluid theory treats dynamic powders that are moving entrained by the gas stream as individual phases and static powders as solid components. The former takes conservation equations of momentum, thermal energy, chemical species and continuity. The latter takes only mass balance equations of chemical species, and shares fields of flow and temperature with the other solid components, such as lump coke, sinter, and so on. In the simulations, the unburned char is derived from the pulverized coal injected from the tuyere, and there is no difference in model treatment between the unburned char and the pulverized coal. The fine coke is generated uniformly in the raceway region from the coke particles, and the generation rate is determined by a kinetic treatment. The simulation of the blast furnace operation by this model revealed that the unburned char and the fine coke having different diameters and densities show different flow patterns especially in the cohesive zone and deadman. Consequently these two powders formed different areas of accumulation and reactions while large amount of powders were deposited in the deadman zone regardless of difference in flow patterns.

Numerical Analysis on Behavior of Unburned Char and Fine Coke in Blast Furnace

A mathematical model of blast furnace operation, which is able to estimate the behaviors of the unburned char and the fine coke simultaneously, has been developed. The model based on the multi-fluid theory treats dynamic powders that are moving entrained by the gas stream as individual phases and static powders as solid components. The former takes conservation equations of momentum, thermal energy, chemical species and continuity. The latter takes only mass balance equations of chemical species, and shares fields of flow and temperature with the other solid components, such as lump coke, sinter, and so on. In the simulations, the unburned char is derived from the pulverized coal injected from the tuyere, and there is no difference in model treatment between the unburned char and the pulverized coal. The fine coke is generated uniformly in the raceway region from the coke particles, and the generation rate is determined by a kinetic treatment. The simulation of the blast furnace operation by this model revealed that the unburned char and the fine coke having different diameters and densities show different flow patterns especially in the cohesive zone and deadman. Consequently these two powders formed different areas of accumulation and reactions while large amount of powders were deposited in the deadman zone regardless of difference in flow patterns.

Raceway Design for the Innovative Blast Furnace

This study tries to design the combustion zone in the highly efficient blast furnace for aiming at great reduction of energy consumption and environmental loads by use of raceway mathematical model. The model treats strictly the discontinuous movement of lump coke particles inside and around raceway, and it considers heat exchange with gas and chemical reactions with gas. In this study, first, the verification of the model is performed. Next, the controllability of raceway by blast conditions is investigated. Finally, the raceway in the top gas recycling process is evaluated in terms of the suitability as combustion zone of the novel blast furnace and of the possibility of its realization. The gas recycling process has the characteristic of blowing top gas without CO 2 , pure oxygen and plastics from tuyere. The results obtained in this work are as follows. 1) Raceway mathematical model has the sufficient ability to represent the characteristics of raceway in all cokes operation and PCI operation. 2) The shape and size of raceway and gas temperature in raceway can be controlled by blast temperature and gas compositions. In addition, nitrogen enrichment in blast is effective to form the uniform and low temperature combustion zone. Raceway in top gas recycling process becomes larger, gas temperature in and around raceway is lower and volumetric flow rate of bosh gas is less than conventional process. Therefore, raceway conditions in the recycling process enable high productivity and high efficiency.

Coke product quality control using feedback from a hydrogen density detection device

The tensile strength of coke was studied to obtain a better understanding of coke strength and its relation to coal properties. The tensile strength was examined by considering coke as a porous material with two influential factors, namely, the matrix strength and the porous structure, which were estimated from the measured tensile strength and porosity. The coke carbon matrix was evaluated in the light of the structure of the coke carbon estimated using X-ray diffraction on the basis of the concept of graphitic and non-graphitic carbon. It was found that the coke matrix strength becomes stronger as the coke carbon structure approaches that of non-graphitic carbon. The porous structure was governed by the coking properties, in this case, the maximum fluidity and the swelling number. As regards the factors governing the coke porous structure, determined by means of image analysis and optical microscopy, it was demonstrated that a poor porous structure was associated with a wide pore size distribution caused mainly by a high proportion of the pores of length < 20 μm, and a rough surface of the pore periphery, which provides potential stress concentration points. The strength anisotropy, which is considered to affect the route of a crack path in lump coke, was also related to pore orientation and the quality of the porous structure.

コークスの剪断応力による粉化挙動解析

To clarify the generation behavior of fine coke by shear stress in the lower part of blast furnace, coke degradation behavior was investigated using the shear stress tester. Furthermore the theory of tribology was applied to estimate the resistance of wear. The main results obtained are as follows;1) The generation rate of coke fine was basically proportional to sliding distance. Shear conditions (shear rate and vertical stress) had a great effect on coke deterioration behavior.2) The coke fine ratio increased rapidly with the vertical pressure or the decrease of coke strength. It was assumed that plastic deformation of coke surface layer resulted in the expand of real contact area among lump coke.3) The wear resistance of coke could be described by the specific wear rate and breaking energy which were approximately 0.1kJ-1 and 200 kJ/kg respectively for normal metallurgical coke.

Transient Mathematical Model of Blast Furnace Based on Multi-fluid Concept, with Application to High PCI Operation.

The ironmaking blast furnace is a counter current chemical reactor whose main purpose is to produce hot metal (pig iron) from iron oxides. In the furnace, five phases: gas, lump solids (iron ore, sinter, pellets and coke), liquids (pig iron and molten slag) and powders (tuyere injectants: pulverized coal, coke fines or dust from the lump coke) interact with one another. In order to evaluate productivity, energy efficiency and transient phenomena occurring in the blast furnace, a comprehensive two-dimensional transient mathematical model has been developed. The model was composed of conservation equations of mass, momentum, chemical species and thermal energy for all phases mentioned above. This model includes phase transformations and chemical reactions such as melting of pig iron and slag components, moisture evaporation, reduction of iron oxides, solution loss, coke and pulverized coal combustion, silica reduction and gas phase reactions. With this model, the transient behavior of the blast furnace process has been successfully predicted for different injection rates of pulverized coal.