To study the combustion behavior of municipal solid waste(MSW)in blast furnace,the combustion process within the raceway was simulated using computational fluid dynamics.Based on the parameters of an actual blast furn...To study the combustion behavior of municipal solid waste(MSW)in blast furnace,the combustion process within the raceway was simulated using computational fluid dynamics.Based on the parameters of an actual blast furnace,a three-dimensional model including coal lance,blowpipe,tuyere,and raceway was established.The model was then used to compare the combustion characteristics of pulverized coal and MSW in the raceway and to investigate the effects of blast temperature and particle size on the combustion characteristics of MSW in the raceway.The results showed that MSW combusted more rapidly,achieving a maximum temperature of 3839 K in the raceway,comparing to 2974 K during pulverized coal injection.However,the average temperature during MSW injection was 1790 K,which was 73 K lower than that of pulverized coal injection.The maximum velocity during MSW injection was 120 m/s,lower than 188 m/s obtained during pulverized coal injection.MSW could be completely burned out in the middle of the raceway,while the burnout of pulverized coal at this position was only 50%.The combustion effect of MSW makes no difference when the blast temperature increased from 1273 to 1673 K,due to its excellent combustion characteristic.When the MSW particle size was increased from 0.074 to 2 mm,the burnout was 75%,which was still higher than that of pulverized coal injection with a particle size of 0.074 mm.However,injecting larger-sized fuel might increase the risk of tuyere wear.To ensure stable furnace conditions and great combustion,a blast temperature of 1473 K and a MSW particle size of about 1 mm will be better.展开更多
The two-dimensional steady-state discrete phase mathematical model is developed to analyze gas-particle flow and combustion characteristics of coal particles, as well as components concentration and temperature distri...The two-dimensional steady-state discrete phase mathematical model is developed to analyze gas-particle flow and combustion characteristics of coal particles, as well as components concentration and temperature distribu- tion of coal gas in the process of pulverized coal injection of blast furnace raceway. The results show that a great deal of coal gas discharges on the top of raceway away from the tuyere, and the residence time of coal particles in the re- gion of blowpipe and tuyere is 20 ms or so and 50 ms when it reaches raceway boundary. The pressure is the highest at the bottom of raceway and the maximal temperature is about 2 423 K. The char combustion is mainly carried out in the raceway and the maximum of char burn-out rate attains 3× 10-4 kg/s.展开更多
The properties of mixed coals were studied on the basis of known various properties of the injecting coals in the treatise.The structure of the injecting coals was optimized and put into practical application.It was f...The properties of mixed coals were studied on the basis of known various properties of the injecting coals in the treatise.The structure of the injecting coals was optimized and put into practical application.It was found that the ignition point was lowered with mixed coals,however,both combustibility and grindability were improved,and explosibility of the mixed coals were decreased as well.Hence,mixed coals injection not only can improve the amount of the injecting coals greatly,but also improve the economical and technical indexes of the blast furnace.展开更多
One of the effective methods of reducing coke consumption is pulverized coal injection. The most important problems encountered in this method are reduced permeability, unburned and high ash content. To select the bes...One of the effective methods of reducing coke consumption is pulverized coal injection. The most important problems encountered in this method are reduced permeability, unburned and high ash content. To select the best coal for injection, suitable tests can be used. Therefore, experiments such as proximate and ultimate analysis, Rock- Eval and combustion tests were performed on four kinds of coals from different mines, including Sarakhs, Sangrood, Karmozd, and Tabas. The results of proximate and ultimate analysis indicated that although the sulfur content and ash content of selected coals were a little high, they were suitable for coal injection. The results of combustion experiments and Rock-Eval tests showed that Karmozd coal was the best one to be injected into blast furnace. The result indicated that the mixing of coals could improve the combustion properties of pulverized coals.展开更多
The combustion process of pulverized coal was investigated by non-isothermic integral thermogravimetry. The thermogravimetry curves were fitted by the Coats-Redferm approximation function, and kinetic parameters and c...The combustion process of pulverized coal was investigated by non-isothermic integral thermogravimetry. The thermogravimetry curves were fitted by the Coats-Redferm approximation function, and kinetic parameters and characteristic temperatures were obtained. The optimal mixing ratio and particle size can be ascertained. The characteristic temperature of pulverized coal can be obtained from the thermogravimetry curve, and the combustion of coal can be divided into homogeneous and heterogeneous combustion according to the differential thermal analysis curve. The activation energy of a single type of coal ranking from low to high is as follows： bituminous coal, meager-lean coal, and anthracite. In the first mixing method, with more low-price meager-lean coal B replacing high price anthracite A, the activation energy slightly decreases; with more bituminous coal replacing meager-lean coal, total tendency makes a declining of activation. In the later mixing method, with an increase in particle size, a declining activation energy can be seen in total tendency.展开更多
In order to improve the calorific value and the recovery yield of converter gas during the steelmaking process, a novel and thermodynamically admissible process was proposed. This method involved injecting pulverized ...In order to improve the calorific value and the recovery yield of converter gas during the steelmaking process, a novel and thermodynamically admissible process was proposed. This method involved injecting pulverized coal into the vaporization cooling flue of a converter, and the approach was developed based on an industrial 30 t converter. The effects of temperature, O2 content, and the volumetric ratio of CO to CO2 on the conversion of the mixed components of gas were analyzed using thermodynamic calculations. Furthermore, the effect of the injection rate on the quality and quantity of gas was investigated. The results show that the O2 and CO2 components of flue gas decrease as the injection rate increases, whereas the CO and H2 components synchronously increase. With the injection rate of 30 kg min-1, the 02 and CO2 components of the gas decreased by 64.12 and 41.19%, respectively, while the CO and H2 increased by 20.09 and 236.84%, respectively, and the recovery time of gas increased by 11.61%, compared to non-injection.展开更多
The combustion process of pulverized coal injected into blast furnace involves a lot of physical and chemical reactions. Based on the combustion behaviors of pulverized coal, the conception of coal effective calorific...The combustion process of pulverized coal injected into blast furnace involves a lot of physical and chemical reactions. Based on the combustion behaviors of pulverized coal, the conception of coal effective calorific value representing the actual thermal energy provided for blast furnace was proposed. A cost performance evaluation model of coal injection was built up for the optimal selection of various kinds of coal based on effective calorific value. The model contains two indicators: coal effective calorific value which has eight sub-indicators and coal injection cost which includes four sub-indicators. In addition, the calculation principle and application of cost performance evaluation model in a Chinese large-scale iron and steel company were comprehensively introduced. The evaluation results finally confirm that this novel model is of great significance to the optimal selection of blast furnace pulverized coal.展开更多
An updated approach to refining the core indicators of pulverized coal used for blast furnace injection based on principal component analysis is proposed in view of the disadvantages of the existing performance indica...An updated approach to refining the core indicators of pulverized coal used for blast furnace injection based on principal component analysis is proposed in view of the disadvantages of the existing performance indicator system of pulverized coal used in blast furnaces. This presented method takes into account all the performance indicators of pulverized coal injection, including calorific value, igniting point, combustibility, reactivity, flowability, grindability, etc. Four core indicators of pulverized coal injection are selected and studied by using principal component analysis, namely, comprehensive combustibility, comprehensive reactivity, comprehensive flowability, and comprehensive grindability. The newly established core index system is not only beneficial to narrowing down current evaluation indices but also effective to avoid previous overlapping problems among indicators by mutually independent index design. Furthermore, a comprehensive property indicator is introduced on the basis of the four core indicators, and the injection properties of pulverized coal can be overall evaluated.展开更多
The combustion characteristics of two kinds of unburned pulverized coal (UPC) made from bituminous coal and anthracite were investigated by thermogravimetric analysis under air. The reaction kinetics mechanisms betwee...The combustion characteristics of two kinds of unburned pulverized coal (UPC) made from bituminous coal and anthracite were investigated by thermogravimetric analysis under air. The reaction kinetics mechanisms between UPC and CO2 in an isothermal experiment in the temperature range 1000–1100°C were investigated. The combustion performance of unburned pulverized coal made from bituminous coal (BUPC) was better than that of unburned pulverized coal made from anthracite (AUPC). The combustion characteristic indexes (S) of BUPC and AUPC are 0.47 × 10^-6 and 0.34 × 10^-6 %2·min^-2·°C^-3, respectively, and the combustion reaction apparent activation energies are 91.94 and 102.63 kJ·mol^-1, respectively. The reaction mechanism of BUPC with CO2 is random nucleation and growth, and the apparent activation energy is 96.24 kJ·mol^-1. By contrast, the reaction mechanism of AUPC with CO2 follows the shrinkage spherical function model and the apparent activation energy is 133.55 kJ·mol^-1.展开更多
Combustion performance of pulverized coal(PC)in blast furnace(BF)process is regarded as a criteria parameter to assess the prop-er injection dosage of PC.In this paper,effects of two kinds of additives,Fe_(2)O_(3) and...Combustion performance of pulverized coal(PC)in blast furnace(BF)process is regarded as a criteria parameter to assess the prop-er injection dosage of PC.In this paper,effects of two kinds of additives,Fe_(2)O_(3) and CaO,on PC combustion were studied using the thermo-gravimetric method.The results demonstrate that both the Fe_(2)O_(3) and CaO can promote combustion performance index of PC including igni-tion index(C_(i)),burnout index(D_(b)),as well as comprehensive combustibility index(S_(n)).The S_(n) increases from 1.37×10^(−6) to 2.16×10^(−6)%2·min^(−2)·℃^(−3) as the Fe_(2)O_(3) proportion increases from 0 to 5.0wt%.Additionally,the combustion kinetics of PC was clarified using the Coats-Redfern method.The results show that the activation energy(E)of PC combustion decreases after adding the above additives.For instance,the E decreases from 56.54 to 35.75 kJ/mol when the Fe_(2)O_(3) proportion increases from 0 to 5.0wt%,which supports the improved combustion per-formance.Moreover,it is uneconomic to utilize pure Fe_(2)O_(3) and CaO in production.Based on economy analysis,we selected the iron-bearing dust(IBD)which contains much Fe_(2)O_(3) and CaO component to investigate,and got the same effects.Therefore,the IBD is a potential option for catalytic PC combustion in BF process.展开更多
The relationship between two-dimensional radiant image and three-dimensional radiant energy in blast furnace raceway was studied by numerical simulation of combustion process. Taking radiant image as radiant boundary ...The relationship between two-dimensional radiant image and three-dimensional radiant energy in blast furnace raceway was studied by numerical simulation of combustion process. Taking radiant image as radiant boundary for numerical simulation of combustion process, the uneven radiation parameter can be calculated. A method to examine three-dimensional temperature distribution in blast furnace raceway was put forward by radiant image processing. The numeral temperature field matching the real combustion can be obtained by proposed numeric image processing technique.展开更多
In order to establish correlativity between pulverized coal combustion in a blast furnace raceway and its radiant image, we investigated the relationships between two dimensional radiant images and three dimensional r...In order to establish correlativity between pulverized coal combustion in a blast furnace raceway and its radiant image, we investigated the relationships between two dimensional radiant images and three dimensional radiant energy in a blast furnace raceway, focusing on the correlativity of the numerical simulation of combustion processes with the connection of radiant images information and space temperature distribution. We calculated the uneven radiate characteristic parameterby taking radiant images as a kind of radiative boundary for numerical simulation of combustion processes, and put fonward a method to examine three-dimensional temperatures distribution in blast furnace raceway by radiant image processing. The numeral temperature fields matching the real combustion can be got by the numeric image processing technique.展开更多
The mechanism of microwave modification or： facilitating the combustion properties of pulverized coal （PC） was investigated. Experimental researches on granularity and functional group as well as combustion propert...The mechanism of microwave modification or： facilitating the combustion properties of pulverized coal （PC） was investigated. Experimental researches on granularity and functional group as well as combustion properties of PC before and after modification were carried out. Micromorphology observation indicated that the size of PC par- ticles was relatively small, which was in accordance with the results of granularity analysis of PC. FT-IR （Fourier- transform infrared） spectra of two PCs indicated that the proportion of the functional groups with high activity in- creased after microwave irradiation. Furthermore, no valid effect of microwave was found on carbon matrix except small variations in PC particle size, which only led to subtle improvement in combustion of residual coke. Activation energies of Yungang and Yangquan PCs in temperature zone between 450--650 ℃ were reduced by 12.00% and 10.13%, respectively, which meant that microwave modification might effectively facilitate the combustion proper- ties of PC. Nevertheless, decrease in activation energies of residual cokes was 3.560% and 3.67% respectively, which was subtle and can be regarded as the result of smaller particle size produced by microwave irradiation.展开更多
An important index to evaluate the process efficiency of coal preparation is the mineral liberation degree of pulverized coal,which is greatly influenced by the particle size and shape distribution acquired by image s...An important index to evaluate the process efficiency of coal preparation is the mineral liberation degree of pulverized coal,which is greatly influenced by the particle size and shape distribution acquired by image segmentation.However,the agglomeration effect of fine powders and the edge effect of granular images caused by scanning electron microscopy greatly affect the precision of particle image segmentation.In this study,we propose a novel image segmentation method derived from mask regional convolutional neural network based on deep learning for recognizing fine coal powders.Firstly,an atrous convolution is introduced into our network to learn the image feature of multi-sized powders,which can reduce the missing segmentation of small-sized agglomerated particles.Then,a new mask loss function combing focal loss and dice coefficient is used to overcome the false segmentation caused by the edge effect.The final comparative experimental results show that our method achieves the best results of 94.43%and 91.44%on AP50 and AP75 respectively among the comparison algorithms.In addition,in order to provide an effective method for particle size analysis of coal particles,we study the particle size distribution of coal powders based on the proposed image segmentation method and obtain a good curve relationship between cumulative mass fraction and particle size.展开更多
Substantial semi-coke has been produced through the industrialized low-temperature pyrolysis process,which has great potential as an alternative fuel for pulverized coal injection(PCI)and iron ore sintering.X-ray diff...Substantial semi-coke has been produced through the industrialized low-temperature pyrolysis process,which has great potential as an alternative fuel for pulverized coal injection(PCI)and iron ore sintering.X-ray diffraction,Raman spectroscope,and thermal analysis were used to compare the carbon chemical structure and combustion reactivity of semi-coke,pulverized coal,and coke breeze.The results show that the average volatile matter content in 46 types of semi-cokes is 8.94 wt.%.The fluctuation range of the characteristic parameters of the semi-coke chemical structure is d_(002)=(0.352–0.379)nm and A_(D1)/A_(G)=(2.51–7.92),while the fluctuation range of the characteristic parameters of pulverized coal is d_(002)=(0.348–0.373)nm and A_(D1)/A_(G)=(1.71–9.03)(where d_(002)means the interlayer spacing between the aromatic planes,and A_(D1)/A_(G)is an index that characterizes the degree of disorder of the char structure through the area ratio of the defect peak band D1 to the perfect graphite peak band G);the overlap between these ranges is relatively high.Contrarily,the fluctuation range of the characteristic parameters of coke breeze is d_(002)=(0.343–0.350)nm and A_(D1)/A_(G)=(0.75–2.51),which is markedly different from that of semi-coke.Semi-coke combustion reactivity is close to that of pulverized coal,but considerably better than that of coke breeze.In terms of chemical structure and combustion reactivity,semi-coke can be used as an alternative fuel for PCI;however,when used for sintering alternative fuel,matching of the heat supply and demand in the later sintering stage must be scrupulously analyzed.展开更多
Aiming at the optimization of the operation condition, a general numerical method for calculating pulverized coal combustion in a full scale furnace fired tangentially at four corners is adopted. “ k ε ” turbulence...Aiming at the optimization of the operation condition, a general numerical method for calculating pulverized coal combustion in a full scale furnace fired tangentially at four corners is adopted. “ k ε ” turbulence model is used for the gas phases and a stochastic approach based on the Lagrangian technique is used for particle phases. Two competing reactions model for the coal devolatilization and PDF (the probability density function) method for the combustion of the gas phases are employed. In the numerical simulations, assuming the air distribution of second port level is of pagoda, waist drum and uniform type. The results show that pagoda type air distribution is advantageous to ignition and smooth combustion of pulverized coal, and suitable to inferior coal combustion in practice. In the present furnace, the igniting distance at 1st and 3rd corner is longer than that at 2nd and 4th corner. The results from numerical calculations are in good agreement with those of observed in practice.展开更多
The efficiency of coal combustion is an important factor for the blast furnace process.The influence of low xO/xC on coal combustion performance under nitrogen free blast furnace condition was researched through the s...The efficiency of coal combustion is an important factor for the blast furnace process.The influence of low xO/xC on coal combustion performance under nitrogen free blast furnace condition was researched through the self-developed pulverized coal burning device.The results show that the coal combustion rate reduces with xO/xC decreasing,and the combustion rate of bituminous coal is higher than that of anthracite.The coal combustion rate ascends with the rise of volatile matter,but when volatile matter of pulverized coal is more than 18%,the combustion rates will not increase correspondingly.Small amount of CaCO3 and CO2 additions can promote coal combustion,and the effect of CaCO3 is more apparent,which can increase the pulverized coal combustion rate by 15%-18% or so.展开更多
Pyrolysis chars have potential as fuels for pulverized coal injection(PCI);however,their proper and efficient utilization requires evaluation of char combustion kinetics.The combustion characteristics of two chars(F-c...Pyrolysis chars have potential as fuels for pulverized coal injection(PCI);however,their proper and efficient utilization requires evaluation of char combustion kinetics.The combustion characteristics of two chars(F-char and M-char)and two pulverized coals(H-PCI and P-PCI)were analyzed herein using thermogravimetric analysis–mass spectrometry.The apparent activation energy(Ea)of the sample under non-isothermal combustion conditions was obtained using the Flynn–Wall–Ozawa and Kissinger–Akahira–Sunose methods,and the reaction mechanism for the fuels was established using the Malek method.Additionally,changes in the microscopic pore structure and carbon chemical structure of the fuels at different stages of combustion were characterized using N2 adsorption and X-ray diffraction to analyze the relationship between microstructural evolution and Ea.The results suggested that Ea of the sample first rapidly decreased and then became stabilized during combustion.Compared with pulverized coals,the two chars presented more developed micro-scopic pore structure,less-ordered carbon chemical structure and lower Ea during reaction.During combustion,the stacking height of the aromatic layer first decreased and then increased,whereas the specific surface area first increased and then decreased.The volatile content significantly influenced Ea only during the initial stage of combustion.During the middle stage,Ea was controlled more by the microscopic pore structure and the carbon chemical structure,and those influences disappeared in the later stage.The transition point of the structures affecting Ea occurred at a combustion rate between 52.9%and 72.0%.In general,the microscopic pore structure and the carbon chemical structure influenced kinetic parameters more than the volatile content.展开更多
The imbibition ability of extinguishant is an important factor influencing the extinguishing effect for smoldering fire in pulverized coals. The coal particle size, bulk compactness, and aqueous solution properties si...The imbibition ability of extinguishant is an important factor influencing the extinguishing effect for smoldering fire in pulverized coals. The coal particle size, bulk compactness, and aqueous solution properties significantly affect the imbibition ability of extinguishment. This work aims to reveal the influence of the properties of pulverized coals and aqueous solution on the imbibition ability of extinguishant for smoldering fire through experiments and capillary theories. The imbibition height and rate were adopted to evaluate the imbibition ability of extinguishment. The results showed that a relatively small bulk compactness and a fine coal particle size negatively influenced the extinguishing process dominantly because of its high surface energy and low wettability. An additive was used to adjust the properties of aqueous solution. The liquid with a larger surface tension, a smaller contact angle, and a lower viscosity induced a better imbibition ability of extinguishment.展开更多
基金supported by the National Natural Science Foundation of China(Nos.51804024 and 52474342)the Fundamental Research Funds for the Central Universities(No.FRF-IC-20-09)the State Key Laboratory of Advanced Metallurgy of University of Science and Technology Beijing(No.41621002).
文摘To study the combustion behavior of municipal solid waste(MSW)in blast furnace,the combustion process within the raceway was simulated using computational fluid dynamics.Based on the parameters of an actual blast furnace,a three-dimensional model including coal lance,blowpipe,tuyere,and raceway was established.The model was then used to compare the combustion characteristics of pulverized coal and MSW in the raceway and to investigate the effects of blast temperature and particle size on the combustion characteristics of MSW in the raceway.The results showed that MSW combusted more rapidly,achieving a maximum temperature of 3839 K in the raceway,comparing to 2974 K during pulverized coal injection.However,the average temperature during MSW injection was 1790 K,which was 73 K lower than that of pulverized coal injection.The maximum velocity during MSW injection was 120 m/s,lower than 188 m/s obtained during pulverized coal injection.MSW could be completely burned out in the middle of the raceway,while the burnout of pulverized coal at this position was only 50%.The combustion effect of MSW makes no difference when the blast temperature increased from 1273 to 1673 K,due to its excellent combustion characteristic.When the MSW particle size was increased from 0.074 to 2 mm,the burnout was 75%,which was still higher than that of pulverized coal injection with a particle size of 0.074 mm.However,injecting larger-sized fuel might increase the risk of tuyere wear.To ensure stable furnace conditions and great combustion,a blast temperature of 1473 K and a MSW particle size of about 1 mm will be better.
基金Item Sponsored by National Natural Science Foundation of China and Shanghai Baosteel Group Co Ltd United Research Foundation(50374085)
文摘The two-dimensional steady-state discrete phase mathematical model is developed to analyze gas-particle flow and combustion characteristics of coal particles, as well as components concentration and temperature distribu- tion of coal gas in the process of pulverized coal injection of blast furnace raceway. The results show that a great deal of coal gas discharges on the top of raceway away from the tuyere, and the residence time of coal particles in the re- gion of blowpipe and tuyere is 20 ms or so and 50 ms when it reaches raceway boundary. The pressure is the highest at the bottom of raceway and the maximal temperature is about 2 423 K. The char combustion is mainly carried out in the raceway and the maximum of char burn-out rate attains 3× 10-4 kg/s.
文摘The properties of mixed coals were studied on the basis of known various properties of the injecting coals in the treatise.The structure of the injecting coals was optimized and put into practical application.It was found that the ignition point was lowered with mixed coals,however,both combustibility and grindability were improved,and explosibility of the mixed coals were decreased as well.Hence,mixed coals injection not only can improve the amount of the injecting coals greatly,but also improve the economical and technical indexes of the blast furnace.
文摘One of the effective methods of reducing coke consumption is pulverized coal injection. The most important problems encountered in this method are reduced permeability, unburned and high ash content. To select the best coal for injection, suitable tests can be used. Therefore, experiments such as proximate and ultimate analysis, Rock- Eval and combustion tests were performed on four kinds of coals from different mines, including Sarakhs, Sangrood, Karmozd, and Tabas. The results of proximate and ultimate analysis indicated that although the sulfur content and ash content of selected coals were a little high, they were suitable for coal injection. The results of combustion experiments and Rock-Eval tests showed that Karmozd coal was the best one to be injected into blast furnace. The result indicated that the mixing of coals could improve the combustion properties of pulverized coals.
基金Item Sponsored by National Key Technology Research and Development Programin 11th Five-Year Plan of China(2008BAB32B05)
文摘The combustion process of pulverized coal was investigated by non-isothermic integral thermogravimetry. The thermogravimetry curves were fitted by the Coats-Redferm approximation function, and kinetic parameters and characteristic temperatures were obtained. The optimal mixing ratio and particle size can be ascertained. The characteristic temperature of pulverized coal can be obtained from the thermogravimetry curve, and the combustion of coal can be divided into homogeneous and heterogeneous combustion according to the differential thermal analysis curve. The activation energy of a single type of coal ranking from low to high is as follows： bituminous coal, meager-lean coal, and anthracite. In the first mixing method, with more low-price meager-lean coal B replacing high price anthracite A, the activation energy slightly decreases; with more bituminous coal replacing meager-lean coal, total tendency makes a declining of activation. In the later mixing method, with an increase in particle size, a declining activation energy can be seen in total tendency.
文摘In order to improve the calorific value and the recovery yield of converter gas during the steelmaking process, a novel and thermodynamically admissible process was proposed. This method involved injecting pulverized coal into the vaporization cooling flue of a converter, and the approach was developed based on an industrial 30 t converter. The effects of temperature, O2 content, and the volumetric ratio of CO to CO2 on the conversion of the mixed components of gas were analyzed using thermodynamic calculations. Furthermore, the effect of the injection rate on the quality and quantity of gas was investigated. The results show that the O2 and CO2 components of flue gas decrease as the injection rate increases, whereas the CO and H2 components synchronously increase. With the injection rate of 30 kg min-1, the 02 and CO2 components of the gas decreased by 64.12 and 41.19%, respectively, while the CO and H2 increased by 20.09 and 236.84%, respectively, and the recovery time of gas increased by 11.61%, compared to non-injection.
基金Project(51134008)supported by the National Natural Science Foundation of ChinaProject(2012CB720401)supported by the National Basic Research Program of China
文摘The combustion process of pulverized coal injected into blast furnace involves a lot of physical and chemical reactions. Based on the combustion behaviors of pulverized coal, the conception of coal effective calorific value representing the actual thermal energy provided for blast furnace was proposed. A cost performance evaluation model of coal injection was built up for the optimal selection of various kinds of coal based on effective calorific value. The model contains two indicators: coal effective calorific value which has eight sub-indicators and coal injection cost which includes four sub-indicators. In addition, the calculation principle and application of cost performance evaluation model in a Chinese large-scale iron and steel company were comprehensively introduced. The evaluation results finally confirm that this novel model is of great significance to the optimal selection of blast furnace pulverized coal.
基金financially supported by the Young Talent Cultivation Fund in Universities (No. FRF-TP-12-020A)the National Natural Science Foundation of China (Nos. 51204013 and 51174023)
文摘An updated approach to refining the core indicators of pulverized coal used for blast furnace injection based on principal component analysis is proposed in view of the disadvantages of the existing performance indicator system of pulverized coal used in blast furnaces. This presented method takes into account all the performance indicators of pulverized coal injection, including calorific value, igniting point, combustibility, reactivity, flowability, grindability, etc. Four core indicators of pulverized coal injection are selected and studied by using principal component analysis, namely, comprehensive combustibility, comprehensive reactivity, comprehensive flowability, and comprehensive grindability. The newly established core index system is not only beneficial to narrowing down current evaluation indices but also effective to avoid previous overlapping problems among indicators by mutually independent index design. Furthermore, a comprehensive property indicator is introduced on the basis of the four core indicators, and the injection properties of pulverized coal can be overall evaluated.
基金financially supported by the National Natural Science Foundation of China (Nos. 51874080, 51604069, and 51774071)the Fundamental Research Funds for the Central Universities, China (No. N162504004)
文摘The combustion characteristics of two kinds of unburned pulverized coal (UPC) made from bituminous coal and anthracite were investigated by thermogravimetric analysis under air. The reaction kinetics mechanisms between UPC and CO2 in an isothermal experiment in the temperature range 1000–1100°C were investigated. The combustion performance of unburned pulverized coal made from bituminous coal (BUPC) was better than that of unburned pulverized coal made from anthracite (AUPC). The combustion characteristic indexes (S) of BUPC and AUPC are 0.47 × 10^-6 and 0.34 × 10^-6 %2·min^-2·°C^-3, respectively, and the combustion reaction apparent activation energies are 91.94 and 102.63 kJ·mol^-1, respectively. The reaction mechanism of BUPC with CO2 is random nucleation and growth, and the apparent activation energy is 96.24 kJ·mol^-1. By contrast, the reaction mechanism of AUPC with CO2 follows the shrinkage spherical function model and the apparent activation energy is 133.55 kJ·mol^-1.
基金supported by the National Natural Science Foundation of China(Nos.52074086,51974073,52074072,52074074)the Fundamental Research Funds for the Central Universities,China(No.N2225039)the Liaoning Provincial Natural Science Foundation of China(No.2019-MS-132)。
文摘Combustion performance of pulverized coal(PC)in blast furnace(BF)process is regarded as a criteria parameter to assess the prop-er injection dosage of PC.In this paper,effects of two kinds of additives,Fe_(2)O_(3) and CaO,on PC combustion were studied using the thermo-gravimetric method.The results demonstrate that both the Fe_(2)O_(3) and CaO can promote combustion performance index of PC including igni-tion index(C_(i)),burnout index(D_(b)),as well as comprehensive combustibility index(S_(n)).The S_(n) increases from 1.37×10^(−6) to 2.16×10^(−6)%2·min^(−2)·℃^(−3) as the Fe_(2)O_(3) proportion increases from 0 to 5.0wt%.Additionally,the combustion kinetics of PC was clarified using the Coats-Redfern method.The results show that the activation energy(E)of PC combustion decreases after adding the above additives.For instance,the E decreases from 56.54 to 35.75 kJ/mol when the Fe_(2)O_(3) proportion increases from 0 to 5.0wt%,which supports the improved combustion per-formance.Moreover,it is uneconomic to utilize pure Fe_(2)O_(3) and CaO in production.Based on economy analysis,we selected the iron-bearing dust(IBD)which contains much Fe_(2)O_(3) and CaO component to investigate,and got the same effects.Therefore,the IBD is a potential option for catalytic PC combustion in BF process.
文摘The relationship between two-dimensional radiant image and three-dimensional radiant energy in blast furnace raceway was studied by numerical simulation of combustion process. Taking radiant image as radiant boundary for numerical simulation of combustion process, the uneven radiation parameter can be calculated. A method to examine three-dimensional temperature distribution in blast furnace raceway was put forward by radiant image processing. The numeral temperature field matching the real combustion can be obtained by proposed numeric image processing technique.
基金Funded by the National Natural Science Foundation of China and Iron & Steel Unite Research Funds (50374085).
文摘In order to establish correlativity between pulverized coal combustion in a blast furnace raceway and its radiant image, we investigated the relationships between two dimensional radiant images and three dimensional radiant energy in a blast furnace raceway, focusing on the correlativity of the numerical simulation of combustion processes with the connection of radiant images information and space temperature distribution. We calculated the uneven radiate characteristic parameterby taking radiant images as a kind of radiative boundary for numerical simulation of combustion processes, and put fonward a method to examine three-dimensional temperatures distribution in blast furnace raceway by radiant image processing. The numeral temperature fields matching the real combustion can be got by the numeric image processing technique.
基金Sponsored by National Key Technology Research and Development Program in 12th Five-year Plan of China(2011BAC01B02)
文摘The mechanism of microwave modification or： facilitating the combustion properties of pulverized coal （PC） was investigated. Experimental researches on granularity and functional group as well as combustion properties of PC before and after modification were carried out. Micromorphology observation indicated that the size of PC par- ticles was relatively small, which was in accordance with the results of granularity analysis of PC. FT-IR （Fourier- transform infrared） spectra of two PCs indicated that the proportion of the functional groups with high activity in- creased after microwave irradiation. Furthermore, no valid effect of microwave was found on carbon matrix except small variations in PC particle size, which only led to subtle improvement in combustion of residual coke. Activation energies of Yungang and Yangquan PCs in temperature zone between 450--650 ℃ were reduced by 12.00% and 10.13%, respectively, which meant that microwave modification might effectively facilitate the combustion proper- ties of PC. Nevertheless, decrease in activation energies of residual cokes was 3.560% and 3.67% respectively, which was subtle and can be regarded as the result of smaller particle size produced by microwave irradiation.
基金Supported by the Research and Development Project of Experimental Technology,China University of Mining and Technology(Study on mineral occurrence in coal based on SEM and EDS,S2023Y018)the National Natural Science Foundations of China under Grant 62371451.
文摘An important index to evaluate the process efficiency of coal preparation is the mineral liberation degree of pulverized coal,which is greatly influenced by the particle size and shape distribution acquired by image segmentation.However,the agglomeration effect of fine powders and the edge effect of granular images caused by scanning electron microscopy greatly affect the precision of particle image segmentation.In this study,we propose a novel image segmentation method derived from mask regional convolutional neural network based on deep learning for recognizing fine coal powders.Firstly,an atrous convolution is introduced into our network to learn the image feature of multi-sized powders,which can reduce the missing segmentation of small-sized agglomerated particles.Then,a new mask loss function combing focal loss and dice coefficient is used to overcome the false segmentation caused by the edge effect.The final comparative experimental results show that our method achieves the best results of 94.43%and 91.44%on AP50 and AP75 respectively among the comparison algorithms.In addition,in order to provide an effective method for particle size analysis of coal particles,we study the particle size distribution of coal powders based on the proposed image segmentation method and obtain a good curve relationship between cumulative mass fraction and particle size.
基金thank the National Natural Science Foundation of China(Nos.51374166,51704224)for funding this research.
文摘Substantial semi-coke has been produced through the industrialized low-temperature pyrolysis process,which has great potential as an alternative fuel for pulverized coal injection(PCI)and iron ore sintering.X-ray diffraction,Raman spectroscope,and thermal analysis were used to compare the carbon chemical structure and combustion reactivity of semi-coke,pulverized coal,and coke breeze.The results show that the average volatile matter content in 46 types of semi-cokes is 8.94 wt.%.The fluctuation range of the characteristic parameters of the semi-coke chemical structure is d_(002)=(0.352–0.379)nm and A_(D1)/A_(G)=(2.51–7.92),while the fluctuation range of the characteristic parameters of pulverized coal is d_(002)=(0.348–0.373)nm and A_(D1)/A_(G)=(1.71–9.03)(where d_(002)means the interlayer spacing between the aromatic planes,and A_(D1)/A_(G)is an index that characterizes the degree of disorder of the char structure through the area ratio of the defect peak band D1 to the perfect graphite peak band G);the overlap between these ranges is relatively high.Contrarily,the fluctuation range of the characteristic parameters of coke breeze is d_(002)=(0.343–0.350)nm and A_(D1)/A_(G)=(0.75–2.51),which is markedly different from that of semi-coke.Semi-coke combustion reactivity is close to that of pulverized coal,but considerably better than that of coke breeze.In terms of chemical structure and combustion reactivity,semi-coke can be used as an alternative fuel for PCI;however,when used for sintering alternative fuel,matching of the heat supply and demand in the later sintering stage must be scrupulously analyzed.
文摘Aiming at the optimization of the operation condition, a general numerical method for calculating pulverized coal combustion in a full scale furnace fired tangentially at four corners is adopted. “ k ε ” turbulence model is used for the gas phases and a stochastic approach based on the Lagrangian technique is used for particle phases. Two competing reactions model for the coal devolatilization and PDF (the probability density function) method for the combustion of the gas phases are employed. In the numerical simulations, assuming the air distribution of second port level is of pagoda, waist drum and uniform type. The results show that pagoda type air distribution is advantageous to ignition and smooth combustion of pulverized coal, and suitable to inferior coal combustion in practice. In the present furnace, the igniting distance at 1st and 3rd corner is longer than that at 2nd and 4th corner. The results from numerical calculations are in good agreement with those of observed in practice.
基金Item Sponsored by National Basic Research Program of China(2012CB720401)National Key Technology Research and Development Program in 12th Five-Year Plan of China(2011BAC01B02)National Natural Science Foundation of China(51134008)
文摘The efficiency of coal combustion is an important factor for the blast furnace process.The influence of low xO/xC on coal combustion performance under nitrogen free blast furnace condition was researched through the self-developed pulverized coal burning device.The results show that the coal combustion rate reduces with xO/xC decreasing,and the combustion rate of bituminous coal is higher than that of anthracite.The coal combustion rate ascends with the rise of volatile matter,but when volatile matter of pulverized coal is more than 18%,the combustion rates will not increase correspondingly.Small amount of CaCO3 and CO2 additions can promote coal combustion,and the effect of CaCO3 is more apparent,which can increase the pulverized coal combustion rate by 15%-18% or so.
基金the National Natural Science Foundation of China(Nos.51704224 and 51574189)the Natural Science Foundation of Shaanxi,China(No.2016JQ5041)the Ministry of Education Services Local Scientific Research Program,Shaanxi,China(No.201刀F012),and Yulin Government of Science and Technology.
文摘Pyrolysis chars have potential as fuels for pulverized coal injection(PCI);however,their proper and efficient utilization requires evaluation of char combustion kinetics.The combustion characteristics of two chars(F-char and M-char)and two pulverized coals(H-PCI and P-PCI)were analyzed herein using thermogravimetric analysis–mass spectrometry.The apparent activation energy(Ea)of the sample under non-isothermal combustion conditions was obtained using the Flynn–Wall–Ozawa and Kissinger–Akahira–Sunose methods,and the reaction mechanism for the fuels was established using the Malek method.Additionally,changes in the microscopic pore structure and carbon chemical structure of the fuels at different stages of combustion were characterized using N2 adsorption and X-ray diffraction to analyze the relationship between microstructural evolution and Ea.The results suggested that Ea of the sample first rapidly decreased and then became stabilized during combustion.Compared with pulverized coals,the two chars presented more developed micro-scopic pore structure,less-ordered carbon chemical structure and lower Ea during reaction.During combustion,the stacking height of the aromatic layer first decreased and then increased,whereas the specific surface area first increased and then decreased.The volatile content significantly influenced Ea only during the initial stage of combustion.During the middle stage,Ea was controlled more by the microscopic pore structure and the carbon chemical structure,and those influences disappeared in the later stage.The transition point of the structures affecting Ea occurred at a combustion rate between 52.9%and 72.0%.In general,the microscopic pore structure and the carbon chemical structure influenced kinetic parameters more than the volatile content.
基金supported by the Key Technical Research Plan of Ministry of Public Security (No. 2017JSYJA13)Independent Innovation Fund of Tianjin University (No. 1706)
文摘The imbibition ability of extinguishant is an important factor influencing the extinguishing effect for smoldering fire in pulverized coals. The coal particle size, bulk compactness, and aqueous solution properties significantly affect the imbibition ability of extinguishment. This work aims to reveal the influence of the properties of pulverized coals and aqueous solution on the imbibition ability of extinguishant for smoldering fire through experiments and capillary theories. The imbibition height and rate were adopted to evaluate the imbibition ability of extinguishment. The results showed that a relatively small bulk compactness and a fine coal particle size negatively influenced the extinguishing process dominantly because of its high surface energy and low wettability. An additive was used to adjust the properties of aqueous solution. The liquid with a larger surface tension, a smaller contact angle, and a lower viscosity induced a better imbibition ability of extinguishment.
