Large-scale Blast Research Articles

Nonstationary Process Monitoring for Blast Furnaces Based on Consistent Trend Feature Analysis

Blast furnaces are the most crucial equipment in ironmaking processes. Stable operation of the blast furnace is a prerequisite for personnel safety and production efficiency. Therefore, early detection of abnormalities in blast furnaces is an important task for ironmaking processes. However, owing to the large fluctuations in the quality of raw materials, dynamic operating conditions, as well as the impact of the hot blast stoves switches, the measurements of blast furnace show severe nonstationary characteristics. All these factors make monitoring the blast furnace a challenging task. In this article, a nonstationary process monitoring method called consistent trend feature analysis (CTFA) is proposed, which can extract the trend-related features and discard perturbations in process data. The directions and amplitudes of the extracted trends are used for abnormality detection, and a local-learning-based method is proposed for determining a time-varying control limit. The detection performance of the proposed method is analyzed, with a sufficient condition and a necessary condition for the detectability given. The effectiveness of the proposed method is validated by the practical data collected from a large-scale blast furnace located in Liuzhou, China.

Assessing the explosion effect on rock mass pre-destruction

Introduction. Theoretical and empirical research into rock blasting proved that detonation wave propagation results in the development of destruction and pre-destruction zones around the explosive cavity. In the destruction zone, rock crushes. In the pre-destruction zone, stresses set up by the detonation wave are concentrated on rock mass structure defects, giving rise to new micro defects and the development of the existing ones. Rock fracturing and cavitation increase, lowering its strength properties; this is called rock pre-destruction. There are works devoted to the qualitative analysis of rock in the pre-destruction zone, but the problem requires elaboration to offer possibilities for practical application. Research aims to quantify rock mass pre-destruction to use the parameters of rock blasting by borehole charges under opencast mining in engineering calculations. Methods of research. To assess the degree of rock mass pre-destruction at a distance from the charge axis, a pre-destruction intensity coefficient is used. The destruction zone radius is determined by a well-known method. In the destruction zone, the value of the pre-destruction intensity coefficient is higher than one, i. e. there is discontinuity of the rock mass. Beyond the destruction zone, there is a pre-destruction zone where the value of the pre-destruction intensity coefficient is less than one. The pre-destruction zone boundary is at distances of the order of 200–250 charge radii. The pre-destruction intensity coefficient of a particular zone attained after all charges have been fired is determined by summing the pre-destruction intensity coefficient from every charge. According to the energy approach, rock strength can be assessed by the value of the specific drilling energy intensity. In order to determine the reduction value of the specific drilling energy intensity in a particular zone, it is essential to know the drilling specific energy capacity of this zone in the natural state, the pre-destruction intensity coefficient attained after a large-scale blast of borehole charges, and specific drilling energy intensity of completely disintegrated rock. The effect made by another borehole charge explosion on the rock mass is weaker due to its pre-destruction by previous blasts. So we propose the impact multiplicity coefficient that reflects the accumulation of pre-destruction in a particular zone under the sequence blasting of borehole charges. Results. The expected value of the specific drilling energy intensity has been calculated for the individual arbitrarily spaced wells within the pre-destruction zone of a particular rock mass zone. The calculation results were compared with the practical values measured during blasting preparation in the preset rock mass zone. Conclusions. The findings of this study have made it possible to quantify the impact of explosions on rock mass pre-destruction. The developed technique makes it possible to predict the value of drilling energy intensity in the pre-destruction zone and, as a result, establish the required specific energy intensity of detonation and hence the consumption of explosives. Thus, it becomes possible to reduce the consumption of explosives under the existing blasting scheme at the enterprise and model other charge initiation types to select the least expensive one.

Nearsurface Air Layer Pollution with Micronic Dust Particles in Large-Scale Blasting in Open Pit Mining

Nearsurface Air Layer Pollution with Micronic Dust Particles in Large-Scale Blasting in Open Pit Mining

Model Predictive Control of Molten Iron and Slag Quality Indices in a Large-scale Ironmaking Blast Furnace using a Hybrid Dynamic Model*

The stable operation and the optimal thermal control of industrial blast furnaces are challenging due to the complexity of the multi-phase and multi-scale physical and chemical phenomena, the presence of fast and extremely slow dynamics with latency periods of more than 8 hours, the absence of direct measurements of key inner variables, and the occurrence of a wide range of unknown disturbances. Industrial blast furnaces are still operated in a semi-automated manner and the quality of the control depends on the skills and dedication of the operators. Model-based control schemes, operated either in closed-loop or as advisory systems, are an obvious option to achieve a smooth and energetically efficient operation of blast furnaces. This work proposes a hybrid dynamic model-based optimizing control scheme for achieving the desired operational objectives by tightly controlling the hot metal silicon content ([Si]) and the slag basicity (SB) at their desired set-points. These two variables are key product quality indices and indicators of the internal thermal status of the blast furnace process. Within the proposed framework, the optimizer regulates the fast dynamics of the blast furnace to counteract the unmeasured disturbances that are caused by the variations in the solid feed, subject to operational constraints. Simulation results on a large-scale industrial blast furnace demonstrate the potential of the proposed approach for an improved operation of the blast furnace process.

CFD analysis of large-scale hydrogen detonation and blast wave overpressure in partially confined spaces

The effect of confinement on the magnitude of overpressure due to a gaseous detonation of a hydrogen-air mixture was studied with the aid of numerical simulations. A simplified combustion reaction kinetic model applied along with computational fluid dynamics (CFD) allowed for the numerical simulation of large-scale detonations of hydrogen-air mixtures. The model was validated against experimental data reported in the literature for the case of a large-scale (300 m3) surface (unconfined space) detonation of a hydrogen-air mixture and the results of a hydrogen-air (confined space) detonation test performed in a 263 m3 tunnel facility. The predicted overpressure and detonation velocity was in agreement with the measurements in both unconfined and confined detonation cases. To verify the effect of confinement on the magnitude of the blast wave overpressure due to detonation of a combustible gas cloud, a series of CFD simulations of hydrogen detonations followed by propagation of a non-reactive blast wave in various geometries were carried out. The results were compared with the correlation applicable for unconfined detonations, which was also found to be applicable for partially confined detonations after the transformation of the distance from explosion centre to spherical blast wave equivalent radius.

A hybrid dynamic model for the prediction of molten iron and slag quality indices of a large-scale blast furnace

The stable, economically optimal, and environmental-friendly operation of blast furnaces is still a challenge. Blast furnaces consume huge amounts of energy and are among the biggest sources of CO2 in the metal industry. The operation of industrial blast furnaces is challenging because of their sheer size, multi-phase and multi-scale physics and chemistry, slow dynamics with response times of 8 hours and more, and the lack of direct measurements of most of the important inner variables. Model-based schemes are prime candidates for providing the missing information and improving the operation. However, only recently, such schemes have been applied successfully, and there is still a lot of room for improvements. The spatial extension, the lack of precise mechanistic knowledge about the chemical and physical phenomena, and the presence of unmeasured disturbances make the application of first-principle models to process operations extremely challenging. In this work, a hybrid dynamic model is developed for the prediction of the hot metal silicon content and the slag basicity in the blast furnace process. These two variables are the key indicators of the internal process conditions, and the ultimate goal of our work is to control them by a model-based scheme. The core relationships between the process variables are imposed by a first-principles-based steady-state model, and a parallel data-based model represents the process dynamics and compensates for the deficiencies of the mechanistic model. Validation results for real plant measurements of a world-scale blast furnace show that the hybrid model is more accurate than the rigorous model and a stand-alone data-based model in long-term predictions of the dynamic behavior of the process.

Model and application of hearth activity in a commercial blast furnace

ABSTRACT With the development of a large-scale blast furnace, hearth activity has an important impact on the longevity and efficiency. Based on the analysis of practical example of ShaSteel No. 3 blast furnace, the new hearth activity model was proposed and verified, namely, the slag-iron flow resistance coefficient. Besides, in the model, the prediction of the coke particle size in the hearth was used to predict the hearth activity. Furthermore, the slag-iron properties and coke properties were analysed to the influence degree on the resistance coefficient. The model has been applied to the hearth of ShaSteel No. 3 blast furnace, and it can timely respond to the internal state of hearth. Finally, the methods to activate hearth activity were explained, which not only has application value but also provides theoretical support for the evaluation of hearth activity in actual production.

Structural response of simple partially-clad steel frames to long-duration blast loading

Typically defined as having a positive phase duration in excess of 100 ms, long duration blast events generate significant impulse and dynamic pressures fundamentally exerting damaging drag loads on steel frames. Large scale blast waves have the capability to completely engulf entire buildings resulting in considerable damage to a multitude of structural members. Most literature investigating steel structural response to long duration events considers only isolated column elements, which neglects frame interaction effects. Isolated column response is dependent upon applied blast pressures and section strength, both of which vary with orientation. Isolated column studies often assume cladding is removed instantly upon blast wave arrival. Despite current guidelines, some systems are not frangible or designed to break away instantly resulting in an undesirable partial cladding removal that can increase load on critical elements. Importantly this study investigates the structural response of two partially-clad simple steel frames to long duration blast at two angles of orientation. Results are compared to understand the effect on frame response and correlated with equivalent isolated column damage to determine the effects of frame interaction and partial cladding removal.

Population Genomic Analysis of Listeria monocytogenes From Food Reveals Substrate-Specific Genome Variation.

Listeria monocytogenes is the major causative agent of the foodborne illness listeriosis. Listeriosis presents as flu-like symptoms in healthy individuals, and can be fatal for children, elderly, pregnant women, and immunocompromised individuals. Estimates suggest that L. monocytogenes results in ∼1,600 illnesses and ∼260 deaths annually in the United States. L. monocytogenes can survive and persist in a variety of harsh environments, including conditions encountered in production of fermented dairy products such as cheese. For instance, microbial growth is often limited in soft cheese fermentation because of harsh pH, water content, and salt concentrations. However, L. monocytogenes has caused a number of deadly listeriosis outbreaks through the contamination of cheese. The purpose of this study was to understand if genetically distinct populations of L. monocytogenes are associated with particular foods, including cheese and dairy. To address this goal, we analyzed the population genetic structure of 504 L. monocytogenes strains isolated from food with publicly available genome assemblies. We identified 10 genetically distinct populations spanning L. monocytogenes lineages 1, II, and III and serotypes 1/2a, 1/2b, 1/2c, 4b, and 4c. We observed an overrepresentation of isolates from specific populations with cheese (population 2), fruit/vegetable (population 2), seafood (populations 5, 8 and 9) and meat (population 10). We used the Large Scale Blast Score Ratio pipeline and Roary to identify genes unique to population 1 and population 2 in comparison with all other populations, and screened for the presence of antimicrobial resistance genes and virulence genes across all isolates. We identified > 40 genes that were present at high frequency in population 1 and population 2 and absent in most other isolates. Many of these genes encoded for transcription factors, and cell surface anchored proteins. Additionally, we found that the virulence genes aut and ami were entirely or partially deleted in population 2. These results indicate that some L. monocytogenes populations may exhibit associations with particular foods, including cheese, and that gene content may contribute to this pattern.

Beirut explosion 2020: A case study for a large-scale urban blast simulation

In the face of continued global urbanization, cities are challenged to satisfy increasing standards in terms of quality of life, environmental conditions, safety, security, health, economic growth and mobility. The concept of “smart cities” aims at utilising advanced technologies, artificial intelligence and high computational capacity to increase their resilience and improve the services provided to the citizens. Computation-based numerical simulations have been essentially used to estimate the effects of explosion events in urban environments in terms of both structural damage and human casualties. These provide urban planners and decision makers with valuable information for vulnerability assessment and aid developing prevention or mitigation solutions. In this article, we present a framework to generate a 3D large-scale urbanistic finite element model, where the desired geospatial data are extracted from the open-source world map OpenStreetMap. The model is used to simulate blast wave propagation effects in a wide urban area taking into account the reflections at building surfaces via a sophisticated Fluid-Structure interaction technique integrated in the EUROPLEXUS explicit finite element method software. The explosion in the Port of Beirut in Lebanon, which took place on the 4th of August 2020, was remarkable for the large amount of explosive material causing considerable damage to surrounding structures and a high number of deaths and injured. Such characteristics make the event suitable for assessing the performance of the proposed computational approach in a widely exposed (by the blast wave) urban zone.

Seismic effects induced by large-scale blasts in isotropic and structurally complex pit wall rock masses

Seismic effects induced by large-scale blasts in isotropic and structurally complex pit wall rock masses

Geomechanical behavior of jointed rock mass in the large-scale blast impact zone

The review of literature sources has allowed determining the mechanism of seismic blasts waves in jointed rock mass. The author presents the theoretical formulas for calculating stresses, relative strains and displacement velocities induced in rock mass by large-scale blasts. The formulas take into account the detonation characteristics of explosives, the borehole diameter, the length of explosive charges, the number of simultaneously blasted charges per groups and the factor of explosion energy redistribution to rock throw. Moreover, the formulas include the properties of rocks between the blasting point and a guarded object, and on the exposed surface of a guarded object. The compressive stresses, relative strains and displacement velocities in rocks are calculated from the formulas. The theoretically found change in the displacement velocity versus distance agrees with the field measurement data obtained in an open pit mine of Polyus company. The formulas of stresses and relative strains were used to define seismic impact exerted by large-scale blasts on the barrier of dry dock No. 1. Based on the calculated results, the recommendations are developed on reduction of seismic impact of blasts during dredging in the dock. The research findings are applicable to developing blasting regulations toward reduction in seismic impact of large-scale explosions on exposed surfaces in rock mass, as well as on the ground surface structures and buildings.

Seismic safety of large-scale blasting in natural stone quarries

In actual practice, reduction of seismic impact of blasts down to safe level is based on standard technical documentation as well as on recommendations developed by research institutions and specialized agencies. Chiefly, these regulations are concerned with limitation of explosive mass. In the meanwhile, blasting efficiency is governed by strength of rock, various degrees of rock mass fracturing and watering, as well as by different seismic stability of close-spaced facilities, which requires application of different kinds of explosives. This article presents a case-study of seismically safe blasting design and justification for Mikashevichi granite quarry based on the PPV prediction in the basement of guarded objects. The quarry zoning is accomplished by the criterion of allowable explosive mass per one delay interval. The probabilistic PPV prediction method is described. The residential and industrial facilities within the seismic impact zone of blasting in Mikashevichi quarry can experience adverse effect of seismic waves during mining advance, which requires introduction of differentiated limitation of allowable explosive mass per one delay interval. The probabilistic approach to blasting pattern design with regard to theoretical distribution of seismicity coefficients ensures the seismic safety of blasting. The developed chart of seismically safe explosive charges per delay interval ensures integrated safety of all guarded objects at the natural stone quarry, with allowance for closer spaced blasting operations and subsequent mining advance.

Effect of Stress Anisotropy on the Efficiency of Large-Scale Destress Blasting

Large-scale panel destressing is a rockburst control technique that is used to create a stress shadow in the ore pillar to be mined. The technique aims to reduce the pillar burst proneness by deviating the major induced principal stresses away from the concerned zone of interest. The destress panels, situated in the pillar hanging wall, are choke-blasted with high explosive energy density, and the blast-induced damage in the panel is accompanied by stress dissipation and stiffness reduction due to fragmentation in the panel. These two effects are traditionally modeled holistically with stiffness and stress reduction factors α and β, respectively, applied to the destressed zone. This paper focuses on the interpretation of Phase 3 destress blasting results at Copper Cliff Mine (CCM) where a stress increase (rather than decrease) was detected in the ore pillar crown, while a stress decrease was recorded in the ore pillar sill (as expected). It is hypothesized that high mining-induced stress anisotropy in the pillar crown caused blast-induced fractures to propagate in the orientation of the major principal stress, a condition that would hinder the destressing effect in that orientation. To verify the hypothesis, a series of panel anisotropic rock fragmentation and stress dissipation factors are iteratively tested in a 3-dimensional back analysis of the Phase 3 destress blast. The analysis takes into consideration the stope extraction schedule per the mine plan to better replicate the mining-induced stress condition in the panel and the ore pillar. The results show good agreement with stress measurements taken in situ using borehole stress cells installed in the ore pillar prior to destressing. The paper discusses the implications of preferential fracture propagation orientation and how it might affect the efficiency of destress blasting.

Предельные параметры буровзрывных работ при отбойке руды глубокими скважинами в камерах шахты им. Губкина АО «Комбината КМАруда»

The main objective of the paper is to determine the ultimate parameters of drilling and blasting operations and to develop recommendations for execution of large-scale blasting of ferruginous quartzite in the mine of ‘Kombinat KMAruda’ JSC

Blast wave interaction with structures: an application of exploding wire experiments

The purpose of this research study is to build upon prior shock dynamics research to create an improved experimental setup that can be used to better understand the interaction of shock waves with structures. Large-scale blast wave experiments pose a risk to the individuals running the experiments, the surroundings, and the institution funding them. In contrast, small-scale blast experiments are able to decrease the danger and amount of funding needed associated with each experiment while producing valuable data. Simulations of blast wave–structure interaction may, on the other hand, result in extensive computational times and results that need verification. The exploding wire setup used in this research study has been optimized to consistently produce results at a run-time of less than 100 s per experiment. The adaptable exploding wire setup has a discharge voltage range of 10–40 kV. The configuration includes three main components: the driver, the experimental apparatus, and an ultrahigh-speed imaging system. The original makeup of the exploding wire apparatus allows for flexible adjustments of specifications such as initial detonation, shock wave origin, and magnitude in two and three dimensions. A recent advancement in algorithm tracking has allowed for automated detection of the individual shock fronts. In this instance, the exploding wire apparatus was adapted to simulate city-scale explosions in two dimensions, and the results were compared with numerical simulations.

Underwater blast loading of partially submerged sandwich composite materials in relation to air blast loading response

The research presented in this paper focusses on the underwater blast resilience of a hybrid composite sandwich panel, consisting of both glass-fibre and carbon-fibre. The hybrid fibres were selected to optimise strength and stiffness during blast loading by promoting fibre interactions. In the blast experiment, the aim was to capture full-field panel deflection during large-scale underwater blast using high-speed 3D Digital Image Correlation (DIC). The composite sandwich panel was partially submerged and subjected to a 1 kg PE7 charge at 1 m stand-off. The charge was aligned with the centre of the panel at a depth of 275 mm and mimicked the effect of a near-field subsurface mine. The DIC deflection data shows that the horizontal cross-section of the panel deforms in a parabolic shape until excessive deflection causes core shear cracking. The panel then forms the commonly observed “bathtub” deformation shape. DIC data highlighted the expected differences in initial conditions compared to air-blast experiments, including the pre-strains caused by the mass of water (hydrostatic pressure). Furthermore, water depth was shown to significantly influence panel deflection, strain and hence damage sustained under these conditions. Panel deformations and damage after blast was progressively more severe in regions deeper underwater, as pressures were higher and decayed slower compared to regions near the free surface.An identical hybrid composite sandwich panel was subjected to air blast; one panel underwent two 8 kg PE7 charges in succession at 8 m stand-off. DIC was also implemented to record the panel deformations during air blast. The air and underwater blast tests represent two different regimes of blast loading: one far-field in air and one near-field underwater. The difference in deflection development, caused by the differing fluid mediums and stand-off distances, is apparent from the full-field results. During underwater blast the panel underwent peak pressure loading of approximately 52.6 MPa whilst during air blast the panel was subjected to 67.7 kPa followed by 68.9 kPa peak pressure loads in succession. The two experiments demonstrate the response of the same hybrid composite sandwich panel under two differing blast regimes.The post-blast damage and strength of the hybrid panels following air and underwater blasts were evaluated. Post-blast testing revealed that the underwater blast causes significantly more damage compared to air blast, particularly debonding between the skins and core. The air blast panel sustains no visible rear skin/core debonding, whereas 13 regions of rear-face debonds are identified on the underwater blast panel. Sustaining no front-skin breakage was advantageous for retaining a high proportion of the compressive modulus for this hybrid layup following underwater blast. Damage mechanisms were interrelated. Determining the most detrimental type is not straightforward in real explosive and non-idealised experiments, however debonding was understandably shown to be significant. A further study to isolate failure modes and improve in situ instrumentation is ongoing.

Comparative genomic analysis provides insight into the phylogeny and virulence of atypical enteropathogenic Escherichia coli strains from Brazil.

BackgroundAtypical enteropathogenic Escherichia coli (aEPEC) are one of the most frequent intestinal E. coli pathotypes isolated from diarrheal patients in Brazil. Isolates of aEPEC contain the locus of enterocyte effacement, but lack the genes of the bundle-forming pilus of typical EPEC, and the Shiga toxin of enterohemorrhagic E. coli (EHEC). The objective of this study was to evaluate the phylogeny and the gene content of Brazilian aEPEC genomes compared to a global aEPEC collection.MethodologySingle nucleotide polymorphism (SNP)-based phylogenomic analysis was used to compare 106 sequenced Brazilian aEPEC with 221 aEPEC obtained from other geographic origins. Additionally, Large-Scale BLAST Score Ratio was used to determine the shared versus unique gene content of the aEPEC studied.Principal FindingsPhylogenomic analysis demonstrated the 106 Brazilian aEPEC were present in phylogroups B1 (47.2%, 50/106), B2 (23.6%, 25/106), A (22.6%, 24/106), and E (6.6%, 7/106). Identification of EPEC and EHEC phylogenomic lineages demonstrated that 42.5% (45/106) of the Brazilian aEPEC were in four of the previously defined lineages: EPEC10 (17.9%, 19/106), EPEC9 (10.4%, 11/106), EHEC2 (7.5%, 8/106) and EPEC7 (6.6%, 7/106). Interestingly, an additional 28.3% (30/106) of the Brazilian aEPEC were identified in five novel lineages: EPEC11 (14.2%, 15/106), EPEC12 (4.7%, 5/106), EPEC13 (1.9%, 2/106), EPEC14 (5.7%, 6/106) and EPEC15 (1.9%, 2/106). We identified 246 genes that were more frequent among the aEPEC isolates from Brazil compared to the global aEPEC collection, including espG2, espT and espC (P<0.001). Moreover, the nleF gene was more frequently identified among Brazilian aEPEC isolates obtained from diarrheagenic patients when compared to healthy subjects (69.7% vs 41.2%, P<0.05).ConclusionThe current study demonstrates significant genomic diversity among aEPEC from Brazil, with the identification of Brazilian aEPEC isolates to five novel EPEC lineages. The greater prevalence of some virulence genes among Brazilian aEPEC genomes could be important to the specific virulence strategies used by aEPEC in Brazil to cause diarrheal disease.

Investigating the seismic impact made by the underground large-scale blast on the secure facilities of Kyshtym GOK when caving the floor pillar

Introduction. Within the mining claim boundaries of Kyshtym GOK the underground large-scale blast was made to cave in the floor pillar with the maximum explosive weight of 963 kg at the spacing stage. The Institute of Mining UB RAS has received a task to study the seismic impact of the underground large-scale blast on the secure facilities of Kyshtym underground mine industrial site located in the close proximity to the sites of blast works. Research aim is to determine the seismic stability of grounds at the sites of the secure facilities and the permissible values of vibration velocities for Kyshtym GOK buildings. It is also necessary to determine the permissible distances from the blast to the secure facilities for 5 engineering-geological elements on the basis of physical and mechanical properties of rock. Research methodology. On the basis of the initial data, according to the method of IM UB RAS, ground seismic stability calculations have been made at the sites of the facilities to determine the permissible values of vibration velocities for Kyshtym GOK buildings. A multivariate calculation of permissible distances from the blast to the secure facilities for 5 engineering-geological elements (EGE) has also been made depending on the explosive weight at the spacing stage, the coefficient of ground conditions and the permissible velocity of seismic vibrations. Results. The actual velocities of earthquake vibrations were determined by the results of experimental measurements using Minimate Plus and URAN seismic recorders, the values of which did not exceed the permissible velocities of ground motion in the base of buildings. Summary. As a result of comparing calculated values and experimental measurements, the recommendations have been given to establish the limitation of the explosive weight at the spacing stage to the level of minimum hazardous values during the large-scale blasts in the underground mine.

Coke Size Degradation and Its Reactivity Across the Tuyere Regions in a Large-Scale Blast Furnace of Hyundai Steel

It has been well recognized that coke samples can be effectively taken out of working blast furnaces using a drilling machine at the tuyere level. The core represents samples with different temperature profiles at various tuyere regions of a large blast furnace. The average coke size at the tuyere level is known to be about 50 pct smaller than the charged cokes. Using fixed bed reactor and XRD techniques, the cokes sampled were studied for CO2 reactivity and crystallinity, respectively. The apparent reaction rate of coke rapidly increases in the raceway zone, followed by a decrease as the samples are taken at deeper sites in the furnace where the Fe2O3 and CaO contents are high in the bosh and raceway zones in the high temperature regions. In this study, samples extracted at the tuyere level of a large blast furnace were examined to characterize the coke size degradation and the effect of coke graphitization on the reactivity and fines generation at various locations around the tuyere level.