Estimating coke fracture toughness using acoustic emissions and changes in coefficient of friction during scratch testing

Lomas, Hannah; Roest, Richard; Wells, Adam; Wu, Hui; Jiang, Zhengyi; Sakurovs, Richard; Stuart, R; North, Lauren; Thorley, Tizshauna; Mahoney, Merrick R.

doi:10.1016/j.fuel.2018.04.050

Cited by 8 publications

(18 citation statements)

References 30 publications

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“…(2) Responses of AE signals Previous research shows that under the effect of external load, the coal mass is damaged to thus lead to the initiation and expansion of cracks, consequently triggering numerous AE events [30]. Dislocation and slippage between particles in coal matrix can also induce the fracturing of bridge bonds between coal molecules, consequently generating AE phenomenon [33]. AE counts characterize the times of micro-cracking happening during damage and fracturing of the coal mass while the amplitude of the signals reflects the strength of micro-cracking.…”

Section: Test Results Of Multi-parameters During the Damage Of Gas-bementioning

confidence: 99%

Experimental Study on Electric Potential Response Characteristics of Gas-Bearing Coal During Deformation and Fracturing Process

Niu

Wang

et al. 2019

Processes

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Coal mass is deformed and fractured under stress to generate electrical potential (EP) signals. The mechanical properties of coal change with the adsorption of gas. To investigate the EP response characteristics of gas-bearing coal during deformation and fracture, a test system to monitor multi-parameters of gas-bearing coal under load was designed. The results showed that abundant EP signals were generated during the loading process and the EP response corresponded well with the stress change and crack expansion, and validated this with the results from acoustic emission (AE) and high-speed photography. The higher stress level and the greater the sudden stress change led to the greater EP abnormal response. With the increase of gas pressure, the confining action and erosion effect are promoted, causing the damage evolution impacted and failure characteristics changes. As a result, the EP response is similar while the characteristics were promoted. The EP response was generated due to the charge separation caused by the friction effect etc. during the damage and deformation of the coal. Furthermore, the main factors of the EP response were different under diverse loading stages. The presence of gas promoted the EP effect. When the failure of the coal occurred, EP value rapidly rose to a maximum, which could be considered as an anomalous characteristic for monitoring the stability and revealing failure of gas-bearing coal. The research results are beneficial for further investigating the damage-evolution process of gas-bearing coal.

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Section: Test Results Of Multi-parameters During the Damage Of Gas-bementioning

confidence: 99%

Experimental Study on Electric Potential Response Characteristics of Gas-Bearing Coal During Deformation and Fracturing Process

Niu

Wang

et al. 2019

Processes

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“…Cokes LRHV, LRHV 50:50 HRLV, and HRLV were produced in a 7 kg coke oven, whereas MRHV and MRLV were produced in a 400 kg coke oven. The laboratory-scale oven cokes were produced in a custom-built sole-heated oven − from blends of maceral concentrates, produced via the density-based separation of two coals (see section ). Table lists the key parent coal properties (i.e., the properties of the coals from which the cokes were made) for the pilot oven cokes produced from them, and coke strength indices, where measured.…”

Section: Methodsmentioning

confidence: 99%

“…This resulted in a dry bulk density of approximately 830 kg/m 3 , similar to that used by MacPhee et al The charge was compacted until a bed height of 50 mm was obtained. The formation of the bench-scale cokes using a sole-heated oven followed by annealing at 1000 °C in a muffle oven is detailed elsewhere, , and will also be described in our subsequent publication …”

Section: Methodsmentioning

confidence: 99%

Tribological Testing of Metallurgical Coke: Coefficient of Friction and Relation to Coal Properties

et al. 2018

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Tribological testing and analysis of metallurgical-grade cokes were conducted to elucidate the nature of the surface of each coke and the influence of the surface on coke abrasion resistance. The coefficient of friction (COF) was contrasted between cokes of different coal origins. The results indicate that the COF increases with (i) parent coal vitrinite content and (ii) decreasing rank of the parent coal. The amount of ultrafine (i.e., <10 μm at the longest dimension) material produced by coke during continuous rotational tribological testing increased as the rank of the parent coal increased. Above a parent coal mean maximum vitrinite reflectance of 1.37%, the COF began to decrease slightly beyond the first 40–60 s of testing, which can be attributed to the anisotropic, graphitic ultrafines acting as a surface modifier or lubricant. This has implications for the abrasion resistance of coke under blast furnace conditions, in which graphitic ultrafines acting a lubricant would likely reduce the degradation rate of the coke. For the pilot oven coke from the blend examined, the COF at all stages of the experiment was approximately linear with blend composition. The exploratory study described in this paper indicates that the wear characteristics of inertinite maceral derived constituents (IMDC) and reactive maceral derived constituents (RMDC) are different and that the wear behavior of the RMDC is rank dependent, while that of the IMDC is less sensitive to the rank of the initial coal.

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“…This methodology reduces the subjectivity and high statistical variance of the previous manual point-counting method and facilitates the understanding of the correlation between coke petrography and coke mechanical properties. 13 The petrographic and tribological analyses of the coke sampled from BF tuyere level suggested that the wear mechanisms were different for the cokes at different locations in the BF. The abrasive wear and microcracking of bosh coke mainly took place in the relatively porous area of RMDCs and large inert particles; the adhesive and erosive wear was evident on the inert particles of bird's nest coke, especially at the inert interface with a high density of pores.…”

Section: Introductionmentioning

confidence: 99%

“…The advanced technique developed by Pearson Coal Petrography, Inc. provides an opportunity to automatically determine the optical parameters of coke and classify the different forms of carbon in the coke based on their optical parameters. This methodology reduces the subjectivity and high statistical variance of the previous manual point-counting method and facilitates the understanding of the correlation between coke petrography and coke mechanical properties . The petrographic and tribological analyses of the coke sampled from BF tuyere level suggested that the wear mechanisms were different for the cokes at different locations in the BF.…”

Section: Introductionmentioning

confidence: 99%

Petrographic Analysis of Cokes Reacted under Simulated Blast Furnace Conditions

Xing

2019

Energy Fuels

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Two cokes prepared from coals of different ranks were subjected to gasification and annealing under the simulated blast furnace (BF) conditions. The changes in coke petrography were studied using techniques and algorithms developed by Pearson Coal Petrography, Inc.; the coke microstrength was measured using ultramicro indentation. Gasification under the simulated BF conditions consumed both reactive maceral-derived components (RMDCs) and inert maceral-derived components (IMDCs) at the lump periphery; however, the degradation did not penetrate to the core of the coke lump during gasification. The annealing at 2000 °C after gasification further promoted the degradation of IMDCs and RMDCs located at the lump surface; the degradation penetrated toward the center of the coke lump during annealing. The consumption of the coke matrix in the lump core mainly concentrated on the IMDC microtexture, but the RMDC microtexture generally remained. Under the simulated BF gasification conditions, both bireflectance and maximum reflectance of cokes decreased; the more significant value decrease was determined on the coke made from higher rank coal. The inclusion of H2 into the gasification atmosphere caused lower bireflectance reduction for both cokes; however, this mitigation effect caused by the addition of H2 during gasification was overwritten by the subsequent high-temperature annealing, which returned similar bireflectance of cokes upon annealing after gasification in the different atmospheres. The annealing at 2000 °C after gasification significantly promoted the coke reflectance loss and enlarged the differences between the cokes from different coal precursors. Upon simulated BF gasification and annealing conditions, the degradation of coke microstrength and reflectance loss took place simultaneously as a result of the rearrangement of the coke microstructure and the change of coke morphology.

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Estimating coke fracture toughness using acoustic emissions and changes in coefficient of friction during scratch testing

Cited by 8 publications

References 30 publications

Experimental Study on Electric Potential Response Characteristics of Gas-Bearing Coal During Deformation and Fracturing Process

Experimental Study on Electric Potential Response Characteristics of Gas-Bearing Coal During Deformation and Fracturing Process

Tribological Testing of Metallurgical Coke: Coefficient of Friction and Relation to Coal Properties

Petrographic Analysis of Cokes Reacted under Simulated Blast Furnace Conditions

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