COREX process is one of the earliest industrialized smelting reduction ironmaking technology.A numerical simulation model based on discrete element method ( DEM ) has been developed to analyze the burden distribution ...COREX process is one of the earliest industrialized smelting reduction ironmaking technology.A numerical simulation model based on discrete element method ( DEM ) has been developed to analyze the burden distribution in the melter gasifier of COREX process.The DEM considering the collisions between particles can directly reproduce the charging process.The burden trajectory , the location and the burden surface profile are analyzed in melter gasifier with a mixing charging of coal and direct reduction iron ( DRI ) at the same time.Considering the porosity of packed bed has an important effect on the gas flow distribution of melter gasifier , a method to calculate porosity has been proposed.The distribution of DRI and coal and the porosity in the radial direction are given under different charging patterns , which is necessary to judge the gas flow distribution and provide base data for further researching the melter gasifier for the next work in the future.The research results can be used to guide the operation of adjusting charging and provide important basis for optimizing the charging patterns in order to obtain the reasonable gas distribution.展开更多
Based on the principle of discrete element method （DEM）, a 2D slot model of a COREX melter gasifier was established to analyze the influence of cohesive zone shape on solid flow, including mass distribution, velocit...Based on the principle of discrete element method （DEM）, a 2D slot model of a COREX melter gasifier was established to analyze the influence of cohesive zone shape on solid flow, including mass distribution, velocity distribution, normal force distribution and porosity distribution at a microscopic level. The results show that the co- hesive zone shape almost does not affect the particle movement in the upper shaft and deadman shape. The particles in the lower central bottom experience large normal force to support the particles above them, while particles around the raceway and in the fast flow zone exhibit weak force network. The porosity distribution was also examined under three kinds of cohesive zones. Like the velocity distribution, the whole packed bed can be divided into four main re- gions. With the increase of cohesive zone position, the low porosity region located in the root of cohesive zone increa- ses. And the porosity distribution becomes asymmetric in the case of biased cohesive zone.展开更多
The temperature distribution of COREX melter gasifier was studied by using a two-dimensional 1/30 scale thermal dynamic model.A set of operating conditions,such as radial distribution of direct reduction iron（DRI） t...The temperature distribution of COREX melter gasifier was studied by using a two-dimensional 1/30 scale thermal dynamic model.A set of operating conditions,such as radial distribution of direct reduction iron（DRI） to lump coal and coke volume ratio,coke charging location,coke charging amount and coke size,were taken into account.The results show that the temperature near the wall region decreases with the decrease of the radial distribution of DRI to lump coal and coke volume ratio.The temperature with central coke charging is higher than that without central coke column.Furthermore,the temperature significantly increases with the increase of central coke charging amount.With the increase of intermediate coke charging amount,the temperature near the wall region decreases while the temperature in the intermediate region increases.The temperature increases with the increase of coke size whether charging central coke or intermediate coke.展开更多
Flow behavior was observed in a simplified model cavity of a multiphase High Level Liquid Waste (HLLW) reprocessing glass melter. Electrodes were set to generate Joule-heating flow in the cavity. A chaotic flow occurr...Flow behavior was observed in a simplified model cavity of a multiphase High Level Liquid Waste (HLLW) reprocessing glass melter. Electrodes were set to generate Joule-heating flow in the cavity. A chaotic flow occurred because the lower part of the cavity was heated while the top surface of the cavity was cooled. Downflow and upflow occurred alternately in cavities. The shape of the cavity was a sloping bottom cavity, which was similar in shape to the real glass melter. To know the flow behavior in the cavity, 1-D flow behavior and 2-D flow behavior were measured in an experiment and simulated by an original CFD code. In the sloping bottom cavity, chaotic flow occurred in the upper part of the cavity. In the case of the sloping bottom cavity which had the same set of electrodes as the glass melter, the effect of the downflow near the electrodes decreased. The same phenomena could be predicted in the melter. The experimental results were also used to validate the CFD code, which will be helpful for developing a multiphase Joule-heating flow predicting.展开更多
A three-dimensional semicircle cold model of COREX melter gasifier(MG)was established,and the effects of coke charging pattern on burden movement were investigated by adopting this model.The burden flow pattern of pac...A three-dimensional semicircle cold model of COREX melter gasifier(MG)was established,and the effects of coke charging pattern on burden movement were investigated by adopting this model.The burden flow pattern of packed bed was measured with different coke charging amounts,coke charging positions,and coke sizes.The results show that the solid flow pattern presents a change from straight line type to reverse U type and finally to W type in MG with traditional coke charging,while the burden flow pattern experiences the change from straight line type to W type with platform and finally W type under center coke charging,and the solid flow pattern presents a change from straight line type to W type with platform and finally W type under intermediate coke charging.The difference demonstrates that coke charging pattern affects the uniform descending in MG to some degree.The burden in the coke charging zone keeps a straight line descending.No matter what kind of coke charging pattern is adopted,the burden residence time is shortened with the increase in coke charging amount,and the vertex of deadman decreases obviously,which is conducive to the renewal of the deadman.The appropriate coke charging amount and coke size should be well controlled at 8.7%and 5 mm,respectively.The results are useful not only in developing further understanding of solid flow in MG but also in verifying different mathematical models,particularly the coupled discrete element method with computational fluid dynamics simulation which has been increasingly used in the literature.展开更多
In order to understand the failure mechanism of magnesia-alumina spinel crown of glass melters,a discussion on the stability of Mg-Al-spinel crown of glass melters was given in this paper.The discussion focused on the...In order to understand the failure mechanism of magnesia-alumina spinel crown of glass melters,a discussion on the stability of Mg-Al-spinel crown of glass melters was given in this paper.The discussion focused on the weight balance in the crown arch made of spinel or silica bricks,the creep of spinel crown bricks at high temperatures,the thermal stress distribution in crown bricks as well as at brick joints,and the displacement behavior of crown arch during heat-up of glass melter.It is believed that the tangential stress in spinel crown is much higher than that in silica crown due to the large differenee in their densities,and that the thermal stresses in the crown brick result in opening of a part of the brickto-brick joints at the cold side of the crown,and increase of the tangential stress needed for balancing the weight of the crown.Both defect migration in lattice or along grain boundary and viscous flow in glass phase at grain boundary contribute to the creep of crown bricks at high temperatures.The creep of the matrix of spinel brick is more significant than that of coarse grains because impurities,such as silica and calcia,are concentrated in it.For keeping the crown stable during heat-up period it is important to adjust properly the horizontal positions of each skew brick as temperature increasing based on correctly evaluating the thermal expansion according to the thermal expansion coefficient of the crown brick.展开更多
Tuyere coke probing was conducted at the Baosteel Corex Plant in order to gain a better understanding of the structure of the char bed in the melter gasifier （ MG ）. After screening, the specimens were observed by a...Tuyere coke probing was conducted at the Baosteel Corex Plant in order to gain a better understanding of the structure of the char bed in the melter gasifier （ MG ）. After screening, the specimens were observed by an optical microscope to determine the mechanism of the char bed formation. X-ray diffraction （XRD） was used to clarify the degree of graphitization and infer thermal history of coke. The results show that the amount of powder coming from lump coal in the burden is much more than that from coke. Based on this, measures for improving the char bed＇ s permeability are proposed.展开更多
Metallization degree of DRI（R;） reduces with rising oxidization degree of reduction gas（r;） and oxidization degree of reduction gas rises with falling metallization degree of DRI.This is a vicious circle exists in...Metallization degree of DRI（R;） reduces with rising oxidization degree of reduction gas（r;） and oxidization degree of reduction gas rises with falling metallization degree of DRI.This is a vicious circle exists in present operation of C3000.Fuel consumption（r;） in Corex increases with falling R;and decreases with rising r;. However,r;obviously increases with the integrated change of R;and r;.To increase R;and decrease r;,an analysis on energy consumption and its distribution was deployed in this paper.According to the results,proposal was tabled based on decreasing char bed height.展开更多
By analyzing the thermal and burden structure conditions inside the melter-gasifier of COREX process,the advantage and disadvantage of PCI into the melter-gasifier are clarified.The influence of PCI on the running con...By analyzing the thermal and burden structure conditions inside the melter-gasifier of COREX process,the advantage and disadvantage of PCI into the melter-gasifier are clarified.The influence of PCI on the running condition inside the furnace is analyzed based on the information from production operation and mathematical and physical simulations,and measures to tackle with the problems arising from PCI are proposed.The main results are as follows.①Due to the unfavorable conditions for coking of coal in the melter-gasifier,coking of charged lumpy coal to get semicoke with good size and strength can hardly be expected.To maintain the permeability of the burden column,a packed bed similar to blast furnace is necessary.Therefore,a little more coke with PCI in place of most of the lumpy coal may improve the running of the reactor.This can also make the lumpy coal selection easier.②Overall heat balance analysis of the melter-gasifier shows that PCI has no effect on the thermal condition of the furnace as a whole.Local heat balance analysis,however,shows that the heath of the melter-gasifier is in a critical state of low heat supply.PCI into the hearth will deteriorate the thermal condition.To avoid the cooling of the hearth zone by PCI,more oxygen can be blown to the hearth zone,i.e.increase the oxygen supply to the hearth and decrease accordingly the oxygen supply to the freeboard.More oxygen supply to the hearth seems to bring out the issue of an increase in fuel rate and/or thereby the smelting intensity.Detailed analysis of the physical chemical processes concluded that PCI with more corresponding oxygen supply will not lead to the increase of fuel rate.③Comparing with blast furnace,the raceway volume of COREX melter-gasifier is about only 1/10～1/5 of that of corresponding-size blast furnace.This small raceway is not favorable for PCI.To enlarge the raceway to get more favorable condition for PCI,less tuyeres with more oxygen supply of each tuyere is proposed.④Comparing with lumpy coal feeding into the furnace top,PCI into the hearth will increase the heat consumption in the lower part and decrease the heat consumption in the upper part of the furnace,leading to an increase in freeboard temperature,as well as a heat insufficiency of the hearth zone.In addition to more oxygen supply to the hearth,a more active hearth for better heat transfer is thus also indispensible to maintain its thermal condition.This can be realized by greater raceway size and the consequent better central gas flow.⑤PCI from the primary tuyeres into the hearth can increase the gas volume from the raceway.It can also decrease the coal fines from the lumpy coal charged from the furnace top.These are all favorable to improve the central gas flow,and thereby improve the running of the furnace.⑥Comparing with blast furnace,COREX process is capable to easily control the direct reduction ratio of the overall reduction process,and thus,total fuel rate lower than blast furnace is attainable if the pursuance of coke-less operation is not overemphasized.展开更多
基金Item Sponsored by Fundamental Research Funds for Central Universities of China ( N090402021 )
文摘COREX process is one of the earliest industrialized smelting reduction ironmaking technology.A numerical simulation model based on discrete element method ( DEM ) has been developed to analyze the burden distribution in the melter gasifier of COREX process.The DEM considering the collisions between particles can directly reproduce the charging process.The burden trajectory , the location and the burden surface profile are analyzed in melter gasifier with a mixing charging of coal and direct reduction iron ( DRI ) at the same time.Considering the porosity of packed bed has an important effect on the gas flow distribution of melter gasifier , a method to calculate porosity has been proposed.The distribution of DRI and coal and the porosity in the radial direction are given under different charging patterns , which is necessary to judge the gas flow distribution and provide base data for further researching the melter gasifier for the next work in the future.The research results can be used to guide the operation of adjusting charging and provide important basis for optimizing the charging patterns in order to obtain the reasonable gas distribution.
基金Item Sponsored by the Fundamental Research Funds for the Central Universities of China(N090402021)
文摘Based on the principle of discrete element method （DEM）, a 2D slot model of a COREX melter gasifier was established to analyze the influence of cohesive zone shape on solid flow, including mass distribution, velocity distribution, normal force distribution and porosity distribution at a microscopic level. The results show that the co- hesive zone shape almost does not affect the particle movement in the upper shaft and deadman shape. The particles in the lower central bottom experience large normal force to support the particles above them, while particles around the raceway and in the fast flow zone exhibit weak force network. The porosity distribution was also examined under three kinds of cohesive zones. Like the velocity distribution, the whole packed bed can be divided into four main re- gions. With the increase of cohesive zone position, the low porosity region located in the root of cohesive zone increa- ses. And the porosity distribution becomes asymmetric in the case of biased cohesive zone.
基金Item Sponsored by Fundamental Research Funds for Central Universities of China(090402021)
文摘The temperature distribution of COREX melter gasifier was studied by using a two-dimensional 1/30 scale thermal dynamic model.A set of operating conditions,such as radial distribution of direct reduction iron（DRI） to lump coal and coke volume ratio,coke charging location,coke charging amount and coke size,were taken into account.The results show that the temperature near the wall region decreases with the decrease of the radial distribution of DRI to lump coal and coke volume ratio.The temperature with central coke charging is higher than that without central coke column.Furthermore,the temperature significantly increases with the increase of central coke charging amount.With the increase of intermediate coke charging amount,the temperature near the wall region decreases while the temperature in the intermediate region increases.The temperature increases with the increase of coke size whether charging central coke or intermediate coke.
文摘Flow behavior was observed in a simplified model cavity of a multiphase High Level Liquid Waste (HLLW) reprocessing glass melter. Electrodes were set to generate Joule-heating flow in the cavity. A chaotic flow occurred because the lower part of the cavity was heated while the top surface of the cavity was cooled. Downflow and upflow occurred alternately in cavities. The shape of the cavity was a sloping bottom cavity, which was similar in shape to the real glass melter. To know the flow behavior in the cavity, 1-D flow behavior and 2-D flow behavior were measured in an experiment and simulated by an original CFD code. In the sloping bottom cavity, chaotic flow occurred in the upper part of the cavity. In the case of the sloping bottom cavity which had the same set of electrodes as the glass melter, the effect of the downflow near the electrodes decreased. The same phenomena could be predicted in the melter. The experimental results were also used to validate the CFD code, which will be helpful for developing a multiphase Joule-heating flow predicting.
基金This project was supported by Scientific Research Fund of Hebei College of Industry and Technology and also supported by the Natural Science Foundation of Hebei Province(E2017417008).
文摘A three-dimensional semicircle cold model of COREX melter gasifier(MG)was established,and the effects of coke charging pattern on burden movement were investigated by adopting this model.The burden flow pattern of packed bed was measured with different coke charging amounts,coke charging positions,and coke sizes.The results show that the solid flow pattern presents a change from straight line type to reverse U type and finally to W type in MG with traditional coke charging,while the burden flow pattern experiences the change from straight line type to W type with platform and finally W type under center coke charging,and the solid flow pattern presents a change from straight line type to W type with platform and finally W type under intermediate coke charging.The difference demonstrates that coke charging pattern affects the uniform descending in MG to some degree.The burden in the coke charging zone keeps a straight line descending.No matter what kind of coke charging pattern is adopted,the burden residence time is shortened with the increase in coke charging amount,and the vertex of deadman decreases obviously,which is conducive to the renewal of the deadman.The appropriate coke charging amount and coke size should be well controlled at 8.7%and 5 mm,respectively.The results are useful not only in developing further understanding of solid flow in MG but also in verifying different mathematical models,particularly the coupled discrete element method with computational fluid dynamics simulation which has been increasingly used in the literature.
文摘In order to understand the failure mechanism of magnesia-alumina spinel crown of glass melters,a discussion on the stability of Mg-Al-spinel crown of glass melters was given in this paper.The discussion focused on the weight balance in the crown arch made of spinel or silica bricks,the creep of spinel crown bricks at high temperatures,the thermal stress distribution in crown bricks as well as at brick joints,and the displacement behavior of crown arch during heat-up of glass melter.It is believed that the tangential stress in spinel crown is much higher than that in silica crown due to the large differenee in their densities,and that the thermal stresses in the crown brick result in opening of a part of the brickto-brick joints at the cold side of the crown,and increase of the tangential stress needed for balancing the weight of the crown.Both defect migration in lattice or along grain boundary and viscous flow in glass phase at grain boundary contribute to the creep of crown bricks at high temperatures.The creep of the matrix of spinel brick is more significant than that of coarse grains because impurities,such as silica and calcia,are concentrated in it.For keeping the crown stable during heat-up period it is important to adjust properly the horizontal positions of each skew brick as temperature increasing based on correctly evaluating the thermal expansion according to the thermal expansion coefficient of the crown brick.
文摘Tuyere coke probing was conducted at the Baosteel Corex Plant in order to gain a better understanding of the structure of the char bed in the melter gasifier （ MG ）. After screening, the specimens were observed by an optical microscope to determine the mechanism of the char bed formation. X-ray diffraction （XRD） was used to clarify the degree of graphitization and infer thermal history of coke. The results show that the amount of powder coming from lump coal in the burden is much more than that from coke. Based on this, measures for improving the char bed＇ s permeability are proposed.
文摘Metallization degree of DRI（R;） reduces with rising oxidization degree of reduction gas（r;） and oxidization degree of reduction gas rises with falling metallization degree of DRI.This is a vicious circle exists in present operation of C3000.Fuel consumption（r;） in Corex increases with falling R;and decreases with rising r;. However,r;obviously increases with the integrated change of R;and r;.To increase R;and decrease r;,an analysis on energy consumption and its distribution was deployed in this paper.According to the results,proposal was tabled based on decreasing char bed height.
文摘By analyzing the thermal and burden structure conditions inside the melter-gasifier of COREX process,the advantage and disadvantage of PCI into the melter-gasifier are clarified.The influence of PCI on the running condition inside the furnace is analyzed based on the information from production operation and mathematical and physical simulations,and measures to tackle with the problems arising from PCI are proposed.The main results are as follows.①Due to the unfavorable conditions for coking of coal in the melter-gasifier,coking of charged lumpy coal to get semicoke with good size and strength can hardly be expected.To maintain the permeability of the burden column,a packed bed similar to blast furnace is necessary.Therefore,a little more coke with PCI in place of most of the lumpy coal may improve the running of the reactor.This can also make the lumpy coal selection easier.②Overall heat balance analysis of the melter-gasifier shows that PCI has no effect on the thermal condition of the furnace as a whole.Local heat balance analysis,however,shows that the heath of the melter-gasifier is in a critical state of low heat supply.PCI into the hearth will deteriorate the thermal condition.To avoid the cooling of the hearth zone by PCI,more oxygen can be blown to the hearth zone,i.e.increase the oxygen supply to the hearth and decrease accordingly the oxygen supply to the freeboard.More oxygen supply to the hearth seems to bring out the issue of an increase in fuel rate and/or thereby the smelting intensity.Detailed analysis of the physical chemical processes concluded that PCI with more corresponding oxygen supply will not lead to the increase of fuel rate.③Comparing with blast furnace,the raceway volume of COREX melter-gasifier is about only 1/10～1/5 of that of corresponding-size blast furnace.This small raceway is not favorable for PCI.To enlarge the raceway to get more favorable condition for PCI,less tuyeres with more oxygen supply of each tuyere is proposed.④Comparing with lumpy coal feeding into the furnace top,PCI into the hearth will increase the heat consumption in the lower part and decrease the heat consumption in the upper part of the furnace,leading to an increase in freeboard temperature,as well as a heat insufficiency of the hearth zone.In addition to more oxygen supply to the hearth,a more active hearth for better heat transfer is thus also indispensible to maintain its thermal condition.This can be realized by greater raceway size and the consequent better central gas flow.⑤PCI from the primary tuyeres into the hearth can increase the gas volume from the raceway.It can also decrease the coal fines from the lumpy coal charged from the furnace top.These are all favorable to improve the central gas flow,and thereby improve the running of the furnace.⑥Comparing with blast furnace,COREX process is capable to easily control the direct reduction ratio of the overall reduction process,and thus,total fuel rate lower than blast furnace is attainable if the pursuance of coke-less operation is not overemphasized.
