The Experts below are selected from a list of 246 Experts worldwide ranked by ideXlab platform
Hao Zhou - One of the best experts on this subject based on the ideXlab platform.
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effect of Coke Rate and basicity on computed tomography measured pore parameters and effective thermal conductivity of iron ore sinter
Journal of materials research and technology, 2019Co-Authors: Mingxi Zhou, Hao Zhou, Jianuo XuAbstract:Abstract During iron ore sintering structural transformation occurs as liquid melt is formed in flame front. This study aimed to compare differences in X-ray computed tomography (XCT) measured pore parameters, and examine relationships between pore parameters and sinter effective thermal conductivity based on actual structure. Nine sinter samples (three Coke Rates multiply three basicity levels) were carefully prepared from pilot-scale sinter pot tests and scanned by XCT with the resolution ratio of 40 μm. The results demonstRate that higher Coke Rate and basicity promote melt formation during sintering, transforming sinter from particulate structure to melt-bonded structure. Under the tested conditions, sinter porosity is in the range of 36.3% ∼56.3% and its effective thermal conductivity decreases from 1.276 W/mK to 0.597 W/mK correspondingly. The anisotropic porous structure of sinter leads to different heat conduction and complicated temperature field in three spatial directions. Of all the XCT-measured pore parameters, porosity and number of +1 mm pores generally decrease with the increasing basicity at the same Coke Rate. The sinter effective thermal conductivity could be negatively correlated to porosity and number of +1 mm pores while there are no clear correlations with parameters including mean pore area and area of the largest pore. The statistic analysis confirms that pores in sinter could be divided into different groups to distinguish their behavior. The pores larger than 1 mm, namely macropores, contribute more than 90% to the total pore volume and set up the main orientation of pore network, determining the sinter thermal behavior predominantly.
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Experimental investigation on the flame front resistance of gas channel growth with melt formation in iron ore sinter beds
Proceedings of the Combustion Institute, 2019Co-Authors: Hao Zhou, Mingxi Zhou, Pengnan Ma, Ming ChengAbstract:The resistance of the flame front within the solid bed constitutes a fundamental and crucial area in porous bed combustion as the flame front propagation is highly related to the productivity and product quality. This paper focuses on the iron ore sintering, a thermal agglomeration process in steel mills. The results from a detailed experimental study of the pilot-scale pot tests under the conditions of a wide range of fuel Rate are presented. The primary objective is to provide better understanding of the growth of gas channels relating to melt formation in the flame front and its resistance to flow. The sintering bed was divided into several zones based on the temperature profile and component distribution. Even though there is a continuous one-to-one replacement of humidified zone with porous sintered zone, a constant air flow Rate during sintering could be obtained, indicating the ∼100 mm high-temperature zone has a controlling effect on sintering bed permeability. The specific pressure drop value in high-temperature zone increases from ∼3 kPa in upper bed to ∼7 kPa in bottom bed, which varies with the bed temperature and structure properties. Both the green bed and sintered bed were scanned by X-ray computed tomography, the reconstruction and image analysis showed that the sintered bed has large gas channels and many more closed pores due to solid-melt-gas coalescence. More melt is geneRated when the heat is accumulated along the bed or input higher Coke content, showing a propensity to suppress the gas channel growth and amplify the mismatch of gas transportation along the bed. Higher Coke Rate leads to a higher resistance in flame front, resulting in a slower flame front speed. These results are aimed to provide quantitative validation for improvements of a numerical sintering model in a future work.
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modeling nox emission of Coke combustion in iron ore sintering process and its experimental validation
Fuel, 2016Co-Authors: Hao Zhou, Mingxi Zhou, Ming Cheng, Jianzhong ChenAbstract:Abstract NOx emission of Coke combustion in iron ore sintering was modeled by overall reaction Rate equations of NOx formation and reduction. Incorporating into a previous sintering heat treatment model, overall NOx emission can be predicted and the simulated results were well agreed with four sinter pot tests under varying conditions which are similar to actual production. In sintering, NOx emission is significantly related to fuel combustion. Due to heat input by ignition and smaller airflow in the initial stage of sintering, the predicted NOx emission has a higher value of about 350 ppm first then it decreases a little and keeps at a relatively constant level of about 300 ppm until the burn-through point, and decreases rapidly as a result of the accomplishment of Coke combustion. Simulation results indicate that fuel NOx is the main NOx emission in sintering while thermal NOx is rarely produced since the bed temperature is much lower than 1800 K. The geneRated NOx could be reduced not only on the surface and in the pores of Coke but also by CO around Coke particles, about 50% and 10% of the geneRated NOx could be reduced by char and CO, respectively. Increasing Coke Rate and decreasing Coke size promote NOx generation by accelerating the Coke combustion. The reduction extent by char is greatly influenced by contact between NOx and char while the reduction extent by CO is mainly determined by the combustion atmosphere.
Mingxi Zhou - One of the best experts on this subject based on the ideXlab platform.
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effect of Coke Rate and basicity on computed tomography measured pore parameters and effective thermal conductivity of iron ore sinter
Journal of materials research and technology, 2019Co-Authors: Mingxi Zhou, Hao Zhou, Jianuo XuAbstract:Abstract During iron ore sintering structural transformation occurs as liquid melt is formed in flame front. This study aimed to compare differences in X-ray computed tomography (XCT) measured pore parameters, and examine relationships between pore parameters and sinter effective thermal conductivity based on actual structure. Nine sinter samples (three Coke Rates multiply three basicity levels) were carefully prepared from pilot-scale sinter pot tests and scanned by XCT with the resolution ratio of 40 μm. The results demonstRate that higher Coke Rate and basicity promote melt formation during sintering, transforming sinter from particulate structure to melt-bonded structure. Under the tested conditions, sinter porosity is in the range of 36.3% ∼56.3% and its effective thermal conductivity decreases from 1.276 W/mK to 0.597 W/mK correspondingly. The anisotropic porous structure of sinter leads to different heat conduction and complicated temperature field in three spatial directions. Of all the XCT-measured pore parameters, porosity and number of +1 mm pores generally decrease with the increasing basicity at the same Coke Rate. The sinter effective thermal conductivity could be negatively correlated to porosity and number of +1 mm pores while there are no clear correlations with parameters including mean pore area and area of the largest pore. The statistic analysis confirms that pores in sinter could be divided into different groups to distinguish their behavior. The pores larger than 1 mm, namely macropores, contribute more than 90% to the total pore volume and set up the main orientation of pore network, determining the sinter thermal behavior predominantly.
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Experimental investigation on the flame front resistance of gas channel growth with melt formation in iron ore sinter beds
Proceedings of the Combustion Institute, 2019Co-Authors: Hao Zhou, Mingxi Zhou, Pengnan Ma, Ming ChengAbstract:The resistance of the flame front within the solid bed constitutes a fundamental and crucial area in porous bed combustion as the flame front propagation is highly related to the productivity and product quality. This paper focuses on the iron ore sintering, a thermal agglomeration process in steel mills. The results from a detailed experimental study of the pilot-scale pot tests under the conditions of a wide range of fuel Rate are presented. The primary objective is to provide better understanding of the growth of gas channels relating to melt formation in the flame front and its resistance to flow. The sintering bed was divided into several zones based on the temperature profile and component distribution. Even though there is a continuous one-to-one replacement of humidified zone with porous sintered zone, a constant air flow Rate during sintering could be obtained, indicating the ∼100 mm high-temperature zone has a controlling effect on sintering bed permeability. The specific pressure drop value in high-temperature zone increases from ∼3 kPa in upper bed to ∼7 kPa in bottom bed, which varies with the bed temperature and structure properties. Both the green bed and sintered bed were scanned by X-ray computed tomography, the reconstruction and image analysis showed that the sintered bed has large gas channels and many more closed pores due to solid-melt-gas coalescence. More melt is geneRated when the heat is accumulated along the bed or input higher Coke content, showing a propensity to suppress the gas channel growth and amplify the mismatch of gas transportation along the bed. Higher Coke Rate leads to a higher resistance in flame front, resulting in a slower flame front speed. These results are aimed to provide quantitative validation for improvements of a numerical sintering model in a future work.
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modeling nox emission of Coke combustion in iron ore sintering process and its experimental validation
Fuel, 2016Co-Authors: Hao Zhou, Mingxi Zhou, Ming Cheng, Jianzhong ChenAbstract:Abstract NOx emission of Coke combustion in iron ore sintering was modeled by overall reaction Rate equations of NOx formation and reduction. Incorporating into a previous sintering heat treatment model, overall NOx emission can be predicted and the simulated results were well agreed with four sinter pot tests under varying conditions which are similar to actual production. In sintering, NOx emission is significantly related to fuel combustion. Due to heat input by ignition and smaller airflow in the initial stage of sintering, the predicted NOx emission has a higher value of about 350 ppm first then it decreases a little and keeps at a relatively constant level of about 300 ppm until the burn-through point, and decreases rapidly as a result of the accomplishment of Coke combustion. Simulation results indicate that fuel NOx is the main NOx emission in sintering while thermal NOx is rarely produced since the bed temperature is much lower than 1800 K. The geneRated NOx could be reduced not only on the surface and in the pores of Coke but also by CO around Coke particles, about 50% and 10% of the geneRated NOx could be reduced by char and CO, respectively. Increasing Coke Rate and decreasing Coke size promote NOx generation by accelerating the Coke combustion. The reduction extent by char is greatly influenced by contact between NOx and char while the reduction extent by CO is mainly determined by the combustion atmosphere.
R Godiin - One of the best experts on this subject based on the ideXlab platform.
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assessment of industrial operation at low Coke Rate and coal injection in excess of 200 kg thm
Europace, 2002Co-Authors: D Sert, R GodiinAbstract:This project, which proceeded at CORUS IJmuiden BF Nr. 6 and BF Nr. 7, and at SOLLAC Dunkerque BF Nr. 4, aimed at significantly decrease the Coke Rate down to levels in the range of 275 kg/thm, by significantly increasingthe coal injection Rate. But despite some improvement in the Coke and coal Rate ratios, the search of safe operation on one side, and some technological problems on the other side, did not enable to reach this initial objective. Despite this situation, different studies have been done in the course of the project, which conclusions seem interesting when looking for high coal Rate operation. These studies were mainly dealing with : - the comparison of the burden at both plants; - the way to promote the coal combustion; - the evaluation of the thermo-chemical conditions of the shaft at coal Rates around 180 kg/thm; - the monitoring of the evolution of the hearth conditions in time at high coal injection practice; - the blast furnace process at high coal injection Rate; - the evaluation of different factors affecting the pressure drop and the permeability of IJmuiden BF Nr. 6, mainly. Coal Rate, temperature, and burden quality effects have been more specifically investigated. The main outcomes of these investigations, discussed and shared by CORUS IJmuiden, IRSID and SOLLAC at joined meetings, are summarised below. The comparison of the Coke quality at both plants enabled to evaluate the differences in Coke strength measured due to the applied test method at each plant, and also to compare the average size of the Coke at the charging level of the different furnaces by means of the so-called "C1-C2 test". The maximum calculated difference for this parameter is 9 mm. Linked with the high coal injection practice and the Coke quality, the results of radioactive tracers experiments performed on Dunkerque BF Nr. 4 in the field of the ECSC project "Wear of the blast furnace hearth" have also demonstRated that it was possible to improve the permeability of the hearth of the furnace by improving the Coke quality, as measured by the 140 index. The comparison of the ferrous burden showed that in the aggregate, the difference in average reducibility could not explain a Coke Rate difference greater than 3 to 4 kg/thm. It became then clear that the differences between the operating points of the two plants were not due to the quality of the ferrous burden, but more likely to the difference in productivity levels, and probably also to the central operation needed at IJmuiden to produce the required amount of hot metal, due to shaft pressure drop limitations. The behaviour of the ferrous burden within the furnace could be assessed at an already significant coal Rate of 180 kg/thm at Dunkerque BF Nr. 4, by means of two Multi-Points Vertical Probing trials. They showed that the intermediate reducibility of Dunkerque sinter avoided adverse effect linked to the degradation of the burden under reducing conditions. It also made clear that the stable operation of the furnace has been obtained by sharply decreasing the specific gas consumption at the wall side, almost leading to the disappearance of the thermal reserve zone in this area. Moreover, it seems possible that without aiming at it, an ore free layer had been obtained in the very centre of the furnace, which also should have contributed to the stability of Dunkerque BF Nr. 4 operation.
G Harp - One of the best experts on this subject based on the ideXlab platform.
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assessing the internal state of the raceway dead man part of the blast furnace at low Coke Rate
Europace, 2002Co-Authors: P Negro, R R Wilmers, D S Gatherhood, E Beppler, G HarpAbstract:The principal aims of this project were to study the blast furnace hearth and raceway behaviours in case of low Coke and high coal Rates operations. The different partners of this project have used their own possibilitiesand devices installed on several industrial blast furnaces. Using the tuyere Coke sampling devices, it has been established that : - with coal injection Rates ranging from 50 to 200 kg/thm, significant differences were apparent in the drill core structures. In the cases of lower coal injection Rates, the drill cores incorpoRated lower levels of Coke fines and iron/slag and were much less compacted than those achieved in cases of high coal injection Rates. With high coal injection, the fines content increases just behind the bird nest ; - with high coal injection the raceway length becomes lower showing that the permeability of the dead man boundary becomes also lower ; - the fines sampled along the coal along the tuyere radius when using different Coke qualities did not show any accumulation of unburnt coal in the dead man or at the outer shell of the dead man. However, the fines are made of three carbon phases with different level of organisation as graphite and Coke. The graphite content in the fines was higher with high coal injection Rates, near the raceway and in the smaller fraction. Nevertheless, the origin of the graphite fines is till now uncertain ; - the study of the unburnt char by sampling dust and gas at different positions along the height at the wall and the radius at the top of the furnace when using different Coke qualities showed very different results : - the Coke contents in dust rise in the blast furnace from top to bottom in accordance with the increasing thermochemical demand on the Coke, when using feed Coke with low CSR values. In the case of using Coke with high CSR values there is no increase in the Cake content in the dust, i.e. this Coke shows a lower degradation mainly in the lower part of the furnace. This has been also confirmed by calculation of the Coke degradation inside the blast furnace issued from Coke core borings results. More over, hot strength measurements on Coke from the tuyere level show higher values with higher CSR values of feed Coke in the raceway, in the transition zone and in the dead man. This fact is of great importance because the stress on Coke is not finished in the tuyere level ; - in the case of centre Coke charging operations, the maximum C c o a l contents in the dust appear in the lower furnace area and in the upper shaft. Both maximum contents are attributable to transverse flows from the furnace centre, where the highest concentrations of unburnt coal particles are measured. The trials with feed Coke with a higher hot strength show lower C c o a l contents in the dust despite of higher coal Rates. This means a more uniform gas flow when charging Cokes with high CSR values.
Jianuo Xu - One of the best experts on this subject based on the ideXlab platform.
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effect of Coke Rate and basicity on computed tomography measured pore parameters and effective thermal conductivity of iron ore sinter
Journal of materials research and technology, 2019Co-Authors: Mingxi Zhou, Hao Zhou, Jianuo XuAbstract:Abstract During iron ore sintering structural transformation occurs as liquid melt is formed in flame front. This study aimed to compare differences in X-ray computed tomography (XCT) measured pore parameters, and examine relationships between pore parameters and sinter effective thermal conductivity based on actual structure. Nine sinter samples (three Coke Rates multiply three basicity levels) were carefully prepared from pilot-scale sinter pot tests and scanned by XCT with the resolution ratio of 40 μm. The results demonstRate that higher Coke Rate and basicity promote melt formation during sintering, transforming sinter from particulate structure to melt-bonded structure. Under the tested conditions, sinter porosity is in the range of 36.3% ∼56.3% and its effective thermal conductivity decreases from 1.276 W/mK to 0.597 W/mK correspondingly. The anisotropic porous structure of sinter leads to different heat conduction and complicated temperature field in three spatial directions. Of all the XCT-measured pore parameters, porosity and number of +1 mm pores generally decrease with the increasing basicity at the same Coke Rate. The sinter effective thermal conductivity could be negatively correlated to porosity and number of +1 mm pores while there are no clear correlations with parameters including mean pore area and area of the largest pore. The statistic analysis confirms that pores in sinter could be divided into different groups to distinguish their behavior. The pores larger than 1 mm, namely macropores, contribute more than 90% to the total pore volume and set up the main orientation of pore network, determining the sinter thermal behavior predominantly.