A new electric arc furnace （EAF） steelmaking process with increasing hot metal charging ratio and improving slagging regime simultaneously was developed and applied in a 50 t electric arc furnace for more than a yea...A new electric arc furnace （EAF） steelmaking process with increasing hot metal charging ratio and improving slagging regime simultaneously was developed and applied in a 50 t electric arc furnace for more than a year at No. 1 Steelmaking Plant of Shanxi Taigang Stainless Corporation Limited. The essential fact of the new EAF steelmaking process was to charge hot metal in two portions or steps： firstly, 35wt%-40wt% hot metal was pretreated by blowing oxygen in a specially designed reactor for decar burization and improving hot metal temperature and melting premelted slag; secondly, 30wt% hot metal was charged into EAF with high basicity refining slags from ladle furnace （LF）-vacuum degassing furnace （VD） refining process. The results show that the hot metal charging ratio can reach to about 65wt%-70wt% for the new EAF steelrnaking process; meanwhile, the tap-to-tap time of a 50 t EAF can shorten by 5-10 min, the electricity consumption can decrease by 35-50 kW·h/t, the lime consumption can reduce by 10.5 kg/t of molten steel, and the content of harmful heavy metals in molten steel can be easily controlled to less than the upper limits of aimed steel specification or grade compared with the traditional EAF steelmaking process. In addition, the dephosphorization ability shows a slight strengthening, however, a small degree of lessening for desulphurization ability is observed for the new EAF steelmaking process, but the weakness of desulphurization ability cannot become an obstacle to its further application since a stronger desulphurization ability can be achieved during secondary refining of LF coupled with VD after EAF steelmaking process.展开更多
High-alkali species in coal are notorious for causing ash slagging and fouling incidents.In this paper,four high-alkali coals were individually subject to hydrothermal pretreatment(HTP),within a batch-type autoclave a...High-alkali species in coal are notorious for causing ash slagging and fouling incidents.In this paper,four high-alkali coals were individually subject to hydrothermal pretreatment(HTP),within a batch-type autoclave at 300 -C for 1 h,and the treated coals were analyzed,along with the oxygen-containing functional groups determined by Fourier transform infrared spectrometer(FT-IR).Then the alkali species and other components in the coal ash were quantified by X-ray fluorescence(XRF)for evaluating the ash slagging and fouling tendency.Apart from this,FactSage was adopted to simulate the occurrence and transformation of alkali species during coal thermal conversion ending at various temperatures.The findings indicate that the treated coals are superior to the parent ones in terms of certain remarkable changes via HTP.The moisture,oxygen and sulfur of the hydrothermally treated coals decline obviously,while the calorific value rises sharply.HTP could reduce the alkali species to less than 2%(%,by weight,equivalent to Na2O in dry ash),with a maximum removal ratio of 88.9%,lowering the ash slagging and fouling tendency.The proposed mechanism of HTP was that the alkali species in coal matrix became released due to the breakage of the coal functional groups and micropores during HTP.展开更多
Slagging is a major problem in boilers,especially the low-rank coal applied in boilers.In this study,the influence of heat transfer surface on the slagging characteristics of a pilot-scale furnace was investigated.Ni ...Slagging is a major problem in boilers,especially the low-rank coal applied in boilers.In this study,the influence of heat transfer surface on the slagging characteristics of a pilot-scale furnace was investigated.Ni coatings were applied in modifying the deposition surface to control slagging.The growth characteristics of the slag were studied using an online digital image technique.Scanning electron microscopy linked with energy-dispersive X-ray analysis and X-ray diffraction(XRD)were applied to investigate the microstructure,semi-quantitative chemical composition,and mineralogy of slag samples.Ni coating demonstrated a positive effect on the mitigation of slagging.Results revealed that the thicknesses of the slag initially increased with experimental time and then inclined toward stable values for both cases(Case 1:substrate material;Case 2:modified surface).The stable thicknesses for Cases 1 and 2 were 4.91 mm and 3.95 mm,respectively.The heat transfer efficiency was improved by approximately 18.2%with the application of Ni coating for probe surface modification.The mechanism of the mitigation of slagging was investigated in this study.XRD results revealed that the content of alkali reduced when the surface was coated with Ni.The alkali significantly affected the adhesion behavior of the deposition.Hence,Ni coating showed potential in reducing slagging and increasing the efficiency of boilers.The overall study makes a contribution to a deep understanding of the effect of Ni coating on the growth characteristics of the slag.展开更多
The slagging/fouling due to the accession of fireside deposits on the steam boilers decreases boiler efficiency and availability which leads to unexpected shut-downs. Since it is inevitably associated with the three m...The slagging/fouling due to the accession of fireside deposits on the steam boilers decreases boiler efficiency and availability which leads to unexpected shut-downs. Since it is inevitably associated with the three major factors namely the fuel characteristics, boiler operating conditions and ash behavior, this serious slagging/fouling may be reduced by varying the above three factors. The research develops a generic slagging/fouling prediction tool based on hybrid fuzzy clustering and Artificial Neural Networks (FCANN). The FCANN model presents a good accuracy of 99.85% which makes this model fast in response and easy to be updated with lesser time when compared to single ANN. The comparison between predictions and observations is found to be satisfactory with less input parameters. This should be capable of giving relatively quick responses while being easily implemented for various furnace types.展开更多
This paper applies digital image techniques to observe the slagging characteristics of blended coals in a pilot-scale furnace. Collected deposit samples were analyzed by scanning electron microscopy linked with energy...This paper applies digital image techniques to observe the slagging characteristics of blended coals in a pilot-scale furnace. Collected deposit samples were analyzed by scanning electron microscopy linked with energy-dispersive X-ray analysis （SEM-EDX）, X-ray diffraction （XRD）, and X-ray Fluorescence （XRF） to acquire the microstructure, chemical composition, and mineralogy. The deposit thickness of three blends was analyzed between their parent coal A （Datong） and coal B （Shan）, and we noted that the time to reach a stable stage decreased with the ratio of coal B. The addition of coal A into coal B could remarkably restrained the growth and thickness of ash deposits. The results of XRD analysis indicated the initial layer was predominantly comprised of the crystalline minerals quartz, anorthite, or albite except for coal B. All of the blends and coals contained quartz and Ca- to Al-silicates （Ca0.68Na0.32）（All.68Si0.32）Si2O8 in the slag layer where iron-bearing minerals （e.g., ilvaite） were altered into an amorphous phase. The result of SEM-EDX suggested that there was an elemental disparity between the coal ash and deposit.展开更多
Slagging coal gasification process became a highlight of coal chemical industry in China during the last decade. Refractory lining＇ s life of slagging gasifiers is one of the most critical factors for a cost - effect...Slagging coal gasification process became a highlight of coal chemical industry in China during the last decade. Refractory lining＇ s life of slagging gasifiers is one of the most critical factors for a cost - effective operation. The paper introduces current status of coal gasification in China, lining structure of slagging gasifiers and performance of refractory lining. It also summarizes the major factors impacting on refractory wear in slagging coal gasifiers in four Chinese chemical plants, based on ten years of industrial experience. The utilizability is discussed in terms of cost -effectiveness of high chromia refractories and possibility of the alternatives.展开更多
In order to study the slagging characteristics of boiler combustion liners during pulverized coal stream combustion, the slag samples on the surface of combustion liner were investigated by X-ray diffractometry, scan ...In order to study the slagging characteristics of boiler combustion liners during pulverized coal stream combustion, the slag samples on the surface of combustion liner were investigated by X-ray diffractometry, scan electron microscopy and energy dispersive X-ray analysis, and the transformation characteristics of the compositions and crystal phases were studied. The results show that the size of slag granules decreases as the slagging temperature increases; the crystallinity of coal ash I reduces to about 48.6% when the temperature is increased up to 1 350 ℃, and that of the coal ash II reduces to about 65% when the temperature is increased up to 1 500 ℃; the encroachment of molten coal ash to the combustion liner is strengthened. At the same time, the diffusion and the segregation of the compositions in combustion liners have selectivity, which is in favor of enhancing the content of crystal phases, weakening the conglutination among molten slag compositions and combustion liner, and avoiding yielding big clinkers. But the diffusion of the compositions in combustion liners increases the porosity and decreases the mechanical intensity of combustion liner, and makes the slag encroachment to the liner become more serious.展开更多
Wear of the spent high chrome brick in slagging gasifier was studied. The result shows that erosion and spalling are the m, ain wear mechanism of high chrome brick and the CaO content of coal slag is crucial to wear o...Wear of the spent high chrome brick in slagging gasifier was studied. The result shows that erosion and spalling are the m, ain wear mechanism of high chrome brick and the CaO content of coal slag is crucial to wear of high chrome brick.展开更多
In this paper a brief introduction on design features,process of hot-fire check out testsand typical testing results of a 20 MWt coal-fired MHD slagging combustor is presented.Onthe basis of the testing results we con...In this paper a brief introduction on design features,process of hot-fire check out testsand typical testing results of a 20 MWt coal-fired MHD slagging combustor is presented.Onthe basis of the testing results we conclude that all the design requirements of the combustorare satisfied.Analysis on the experimental results is also made.The reasons that causeslower rate of slag rejection are discussed,and the ways of raising slag rejection rate are con-sidered.展开更多
The slagging characteristic of coal effects the safe operation of boiler unit directly, the study on coal slagging is paid more and more attention by scholars of the world. Because of the complexity of coal characteri...The slagging characteristic of coal effects the safe operation of boiler unit directly, the study on coal slagging is paid more and more attention by scholars of the world. Because of the complexity of coal characteristic, the blending coals slagging characteristic is more complex than single coal. The study method of blending coals characteristic is the same as the single coal method, but the simple method can’t distinguish the blending coals slagging characteristic well and truly. This paper gives the new distinguish method of blending coals slagging characteristic based on experimentation condition, it is the rate of slag and furnace refuse. The rate of slagging on furnace wall and the refuse on furnace bottom has utilized to distinguish the slagging characteristic of coal. The result shows that the rate of slag and furnace refuse method has better veracity.展开更多
The type selection of burning equipment for boilers is affected significantly by the slagging characteristics of coal. Based on the engineering statistics method, the designed furnace parameters are obtained from the ...The type selection of burning equipment for boilers is affected significantly by the slagging characteristics of coal. Based on the engineering statistics method, the designed furnace parameters are obtained from the 600-MW and 1 000-MW boilers with tangential firing and wall firing. The power and arrangement of the burners are analyzed. Their impacts on slagging on heating surfaces and the carbon contents in the ash and cinders are also discussed. Thermal parameters of furnace are recommended for boilers of 600 MW and 1 000 MW firing slagging coal in the design. The static or rotary classifier should be the first choice for the pulverizing system.展开更多
During secondary refining of molten steel, reaction of steel-slag has great influence on the quality of steel. Taking high aluminium steel ([Al]≥0.8%) for instance, reaction control of 4[Al]+3(SiO2) = 2(Al2O3)+3[Si] ...During secondary refining of molten steel, reaction of steel-slag has great influence on the quality of steel. Taking high aluminium steel ([Al]≥0.8%) for instance, reaction control of 4[Al]+3(SiO2) = 2(Al2O3)+3[Si] was discussed by both thermodynamics calculation and industrial experiments. The results show that content of silicon increased sharply when content of SiO2 in slag exceeded 10%. In order to prevent the increment of silicon content and reoxidation for high aluminium steel, reasonable component range of LF refining slag is: %CaO/%Al2O3=1.6-1.9, %SiO2 【10. Results of the industrial experiments indicate that the CaO-Al2O3 based refining slag has strong ability of desulfurization and inclusion absorption. Average desulfurization rate is 80%, and T[O] reduces above 50% after refining, with the average sulfur content and T[O] about 0.0025% and 11×10-6,respectively, which can meet the requirements of secondary refining and obtain good castability of steel in continuous casting process.展开更多
Coal is one of the main sources of energy in many parts of the world and has one of the largest reserves/production ratios amongst all the non-renewable energy sources. Gasification of coal is one among the advanced t...Coal is one of the main sources of energy in many parts of the world and has one of the largest reserves/production ratios amongst all the non-renewable energy sources. Gasification of coal is one among the advanced technologies that has potential to be used in a carbon constrained economy. However, gasification availability at several commercial demonstrations had run into problems associated with fouling of syngas coolers due to unpredictable flyash formation and unburnt carbon losses. Computer models of gasifiers are emerging as a powerful tool to predict gasifier performance and reliability, without expensive testing. Most computer models used to simulate gasifiers tend to model coal as a homogenous entity based on bulk properties. However, coal is a heterogeneous material and comminution during feedstock preparation produces particle classes with different physical and chemical properties. It is crucial to characterize the heterogeneity of the feedstocks used by entrained flow gasifiers. To this end, a low ash US bituminous coal that could be used as a gasifier feedstock was segregated into density and size fractions to represent the major mineral matter distributions in the coal. Float and sink method and sieving were employed to partition the ground coal. The organic and inorganic content of all density fractions was characterized for particle size distribution, heating value, ultimate analysis, proximate analysis, mineral matter composition, ash composition, and petrographic components, while size fractions were characterized for heating value, ash composition, ultimate and proximate analysis. The proximate, ultimate and high heating value analysis showed that variation in these values is limited across the range of size fractions, while the heterogeneity is significant over the range of density fractions. With respect to inorganics, the mineral matter in the heavy density fractions contribute significantly to the ash yield in the coal while contributing very little to its heating value. The ash yield across the size fractions exhibits a bimodal distribution. The heterogeneity is also significant with respect to the base-to-acid ratio across the size and density fractions. The results indicate that the variations in organic and inorganic content over a range of density and size classes are significant, even in the low ash, vitrinite rich coal sample characterized here. Incorporating this information appropriately into particle population models used in gasifier simulations will significantly enhance their accuracy of performance predictions.展开更多
In order to mitigate the slagging risks of high-alkali coal (HAC) gasification while optimizing the operating temperatures for practical application,the experimental and calculational works were performed on the horiz...In order to mitigate the slagging risks of high-alkali coal (HAC) gasification while optimizing the operating temperatures for practical application,the experimental and calculational works were performed on the horizontal tubular furnace system and the FactSage 7.2 software,respectively.The slagging tendencies of three HACs were anticipated by applying different indexes of ash chemistry characteristics prior to experiments,but the determined results were found inconsistent.The relationship between Na retained ratio (RNa) and the ash fusion temperatures (AFTs) of gasification residues demonstrated that the AFTs of coal with high RNa are low,while AFTs of coal with low RNa are high.Nevertheless,when the residues contained a large number of calcium-containing silicates and aluminosilicates,the ATFs were reduced significantly even if its RNa stayed at a low level.Furthermore,the operating temperatures of the three coals (in order of Mulei coal,Shaerhu coal,and Tietou coal) were suggested to be controlled below 1150℃,1100℃,and 950℃,respectively.展开更多
Some ash related problems,such as slagging at furnace bottom and fouling at the air pre-heater surface,are frequently encountered during circulating fluidized bed gasification(CFBG)of Zhundong coal.Low ash fusion temp...Some ash related problems,such as slagging at furnace bottom and fouling at the air pre-heater surface,are frequently encountered during circulating fluidized bed gasification(CFBG)of Zhundong coal.Low ash fusion temperatures(AFTs)and intense sodium release should be responsible for those problems.In industry,coal blending is deemed to be a feasible method to both improve AFTs and control sodium release.In this work,Wuhai coal was selected as blending coal.The ratio is varied from 0%to 40%by mass with 10%interval.The mixed samples were gasified by steam at 950°C in a lab-scale furnace.Some key indices,such as sodium release behaviors,ash slagging characteristics and char gasification performances,were investigated by ICP-OES,AFTs,XRD and TG analyzers,respectively.The results indicated that coal blending could significantly decrease sodium release behaviors.For ash slagging characteristics,it is surprised to find that three out of four AFTs(deformation temperature,softening temperature,hemispherical temperature)show an U-shaped correlation with blending ratio,indicating that a low ratio possibly causes more severe ash slagging problem.It is ascribed to the formation of substantial percentage of fusible Na-containing silicates and aluminosilicates.In addition,coal blending greatly increases ST-DT,implying that the ability of resistance to bed temperature fluctuation is markedly enhanced.Due to the high level of alkali and alkaline species,the synergistic effect is clearly observed during co-gasification.Taking all key indices into consideration,30%blending ratio of Wuhai coal is recommended.展开更多
As a low-value solid waste fuel,asphalt rock is prone to slagging even under fluidized bed condition.The purpose of this study is to improve the slagging characteristics of asphalt rock by adding the mineral additives...As a low-value solid waste fuel,asphalt rock is prone to slagging even under fluidized bed condition.The purpose of this study is to improve the slagging characteristics of asphalt rock by adding the mineral additives CaCO_(3),MgO,and Kaolin.The results showed that the K,Al,Ca salts in asphalt rock ash will evolve at different temperatures and exist mainly as K_(2)SO_(4),KAlSiO_(4),Al_(2)O_(3)·SiO_(2),Al_(2)O_(3),CaSO_(4),and CaSiO_(3).The CaSO_(4)formed from sulfur oxides and calcium-containing compounds is the main factor in asphalt rock slagging and can be facilitated by CaSiO_(3)with a small amount of CaCO_(3).The MgO can form MgCa(SiO_(3))_(2)with a high melting point and helps raise the ash fusion temperatures.In addition,the Kaolin will promote the formation of low-temperature eutectics,resulting in a slight decrease in ash fusion temperatures.Through optimization,it was found that with the addition of 9.0%MgO+9.0%Kaolin+2.0%CaCO_(3)(in weight),the slagging ratio and pressure difference of asphalt rock under fluidized bed conditions decreased from 6.5%to 4.2%and from 6.0 Pa to 4.0 Pa,respectively.By combining simulation and experimental methods,it has been shown that appropriate mineral additives of CaCO_(3),MgO,and Kaolin can effectively improve the slagging characteristics of asphalt rock.展开更多
The viscosity of refining slags plays a critical role in metallurgical processes.However,obtaining accurate viscosity data remains challenging due to the complexities of high-temperature experiments,often relying on e...The viscosity of refining slags plays a critical role in metallurgical processes.However,obtaining accurate viscosity data remains challenging due to the complexities of high-temperature experiments,often relying on empirical models with limited predictive capabilities.This study focuses on the influence of optical basicity on viscosity in CaO-Al_(2)O_(3)-based refining slags,leveraging machine learning to address data scarcity and improve prediction accuracy.An automated framework for algorithm integration,parameter tuning,and evaluation ranking framework(Auto-APE)is employed to develop customized data-driven models for various slag systems,including CaO-Al_(2)O_(3)-SiO_(2),CaO-Al_(2)O_(3)-CaF_(2),CaO-Al_(2)O_(3)-SiO_(2)-MgO,and CaO-Al_(2)O_(3)-SiO_(2)-MgO-CaF_(2).By incorporating optical basicity as a key feature,the models achieve an average validation error of 8.0%to 15.1%,significantly outperforming traditional empirical models.Additionally,symbolic regression is introduced to rapidly construct domain-specific features,such as optical basicity-like descriptors,offering a potential breakthrough in performance prediction for small datasets.This work highlights the critical role of domain-specific knowledge in understanding and predicting viscosity,providing a robust machine learning-based approach for optimizing refining slag properties.展开更多
A full-sectional microstructure characterization method was developed to investigate the formation of coarse slag rims during the continuous casting of hypo-peritectic steel.The cross-sectional microstructural analysi...A full-sectional microstructure characterization method was developed to investigate the formation of coarse slag rims during the continuous casting of hypo-peritectic steel.The cross-sectional microstructural analysis of typical slag rims for two highly crystalline powders revealed that their formation was primarily driven by the solidification of the liquid slag.Distinct differences were observed in the microstructures of slag rims from the two powders.Powder A(characterized by a higher breaking temperature and viscosity)displayed alternating lamellar microstructures of coarse and fine phases,with the coarse phases composed of akermanite-gehlenite transition phases.In contrast,powder B(with a lower breaking temperature and viscosity)predominantly comprised regular akermanite-gehlenite crystals interspersed with a certain amount of glassy phases.Numerical simulations of a three-phase fluid flow coupled with heat transfer indicate that slag rim formation correlates with mold oscillation.Solidification of the liquid slag at the slag rim front predominantly occurs during the negative stroke of the mold oscillation.The average heating rate during the ascending stage of the mold reaches approximately 100 K·s^(−1),whereas the average cooling rate during the descending stage attains 400 K·s^(−1).This temperature variation leads to the formation of lamellar microstructures,whereas the ascending stage promotes the formation of coarse structures and thicker slag rims.Based on the powder properties,two distinct formation pathways exist for highly crystalline mold powders.For the powders with a higher breaking temperature,higher viscosity,and narrower solidification range(powder A),coarse microstructures and thicker slag rims were preferentially formed.For powders with lower breaking temperature and viscosity and wider solidification ranges(powder B),the liquid slag resisted rapid solidification,and the extended mushy zone allowed the partial liquid slag to persist at the slag rim front,promoting the formation of a thin slag rim.This study enhances the understanding of slag rim formation in highly crystalline mold powders and provides critical insights into the control of longitudinal surface cracks in hypo-peritectic steel.展开更多
Manganese is a major impurity in acidic vanadium-bearing leaching solutions,but its effects on vanadium precipitation via hydrolysis and acidic ammonium salts remain unclear.In this study,vanadium-bearing leachates wi...Manganese is a major impurity in acidic vanadium-bearing leaching solutions,but its effects on vanadium precipitation via hydrolysis and acidic ammonium salts remain unclear.In this study,vanadium-bearing leachates with varying manganese concentrations(VL-cMn)were prepared through calcium,a calcium-manganese composite,and manganese-based roasting of vanadium slag(VS)to investigate the influence of manganese on vanadium precipitation behavior during hydrolysis precipitation(HP)and ammonium salt precipitation(AP),as well as the microscopic characteristics and purity of the resulting V_(2)O_(5) products.The results showed that increasing the pH mitigated the negative effects of Mn on the V precipitation rate during HP.However,as the manganese concentration increased from 5.69 to 15.38 g/L,the V precipitation rate gradually declined at higher temperatures and longer reaction times.The precipitates exhibited increased microstructural density,which might had contributed to the formation of Mn-bearing phases.Additionally,the average grain size of V_(2)O_(5) was reduced and the particles were increasingly agglomerated,leading to a 2.55%decrease in product purity.For AP,as manganese concentration increased,raising the pH counteracted the negative impact of Mn on the V precipitation rate and reduced the required amount of ammonium sulfate.Moreover,Mn was unevenly adsorbed on the surface of the precipitates.Although V_(2)O_(5) grains gradually shrank and became denser,there was no significant effect on the final product purity,which remained above 99.3%.In conclusion,roasting with added manganese salts influenced the hydrolysis of vanadium but had no significant effect on acidic ammonium salt precipitation.展开更多
Gasification or combustion of coal and biomass is the most important form of power generation today.However,the use of coal/biomass at high temperatures has an inherent problem related to the ash generated.The formati...Gasification or combustion of coal and biomass is the most important form of power generation today.However,the use of coal/biomass at high temperatures has an inherent problem related to the ash generated.The formation of ash leads to a problematic phenomenon called slagging.Slagging is the accumulation of molten ash on the walls of the furnace,gasifier,or boiler and is detrimental as it reduces the heat transfer rate,and the combustion/gasification rate of unburnt carbon,causes mechanical failure,high-temperature corrosion and on occasions,superheater explosions.To improve the gasifier/combustor facility,it is very important to understand the key ash properties,slag characteristics,viscosity and critical viscosity temperature.This paper reviews the content,compositions,and melting characteristics of ashes in differently ranked coal and biomass,and discusses the formation mechanism,characteristics,and structure of slag.In particular,this paper focuses on low-rank coal and biomass that have been receiving increased attention recently.Besides,it reviews the available methodologies and formulae for slag viscosity measurement/prediction and summarizes the current limitations and potential applications.Moreover,it discusses the slagging behavior of different ranks of coal and biomass by examining the applicability of the current viscosity measurement methods to these fuels,and the viscosity prediction models and factors that affect the slag viscosity.This review shows that the existing viscosity models and slagging indices can only satisfactorily predict the viscosity and slagging propensity of high-rank coals but cannot predict the slagging propensity and slag viscosity of low-rank coal,and especially biomass ashes,even if they are limited to a particular composition only.Thus,there is a critical need for the development of an index,or a model or even a measurement method,which can predict/measure the slagging propensity and slag viscosity correctly for all low-rank coal and biomass ashes.展开更多
文摘A new electric arc furnace （EAF） steelmaking process with increasing hot metal charging ratio and improving slagging regime simultaneously was developed and applied in a 50 t electric arc furnace for more than a year at No. 1 Steelmaking Plant of Shanxi Taigang Stainless Corporation Limited. The essential fact of the new EAF steelmaking process was to charge hot metal in two portions or steps： firstly, 35wt%-40wt% hot metal was pretreated by blowing oxygen in a specially designed reactor for decar burization and improving hot metal temperature and melting premelted slag; secondly, 30wt% hot metal was charged into EAF with high basicity refining slags from ladle furnace （LF）-vacuum degassing furnace （VD） refining process. The results show that the hot metal charging ratio can reach to about 65wt%-70wt% for the new EAF steelrnaking process; meanwhile, the tap-to-tap time of a 50 t EAF can shorten by 5-10 min, the electricity consumption can decrease by 35-50 kW·h/t, the lime consumption can reduce by 10.5 kg/t of molten steel, and the content of harmful heavy metals in molten steel can be easily controlled to less than the upper limits of aimed steel specification or grade compared with the traditional EAF steelmaking process. In addition, the dephosphorization ability shows a slight strengthening, however, a small degree of lessening for desulphurization ability is observed for the new EAF steelmaking process, but the weakness of desulphurization ability cannot become an obstacle to its further application since a stronger desulphurization ability can be achieved during secondary refining of LF coupled with VD after EAF steelmaking process.
基金the National Key Basic Research Program of China (No. 2014CB238905)
文摘High-alkali species in coal are notorious for causing ash slagging and fouling incidents.In this paper,four high-alkali coals were individually subject to hydrothermal pretreatment(HTP),within a batch-type autoclave at 300 -C for 1 h,and the treated coals were analyzed,along with the oxygen-containing functional groups determined by Fourier transform infrared spectrometer(FT-IR).Then the alkali species and other components in the coal ash were quantified by X-ray fluorescence(XRF)for evaluating the ash slagging and fouling tendency.Apart from this,FactSage was adopted to simulate the occurrence and transformation of alkali species during coal thermal conversion ending at various temperatures.The findings indicate that the treated coals are superior to the parent ones in terms of certain remarkable changes via HTP.The moisture,oxygen and sulfur of the hydrothermally treated coals decline obviously,while the calorific value rises sharply.HTP could reduce the alkali species to less than 2%(%,by weight,equivalent to Na2O in dry ash),with a maximum removal ratio of 88.9%,lowering the ash slagging and fouling tendency.The proposed mechanism of HTP was that the alkali species in coal matrix became released due to the breakage of the coal functional groups and micropores during HTP.
基金Supported by the National Natural Science Foundation of China(51476137)National Science Fund for Distinguished Young Scholars(51825605)
文摘Slagging is a major problem in boilers,especially the low-rank coal applied in boilers.In this study,the influence of heat transfer surface on the slagging characteristics of a pilot-scale furnace was investigated.Ni coatings were applied in modifying the deposition surface to control slagging.The growth characteristics of the slag were studied using an online digital image technique.Scanning electron microscopy linked with energy-dispersive X-ray analysis and X-ray diffraction(XRD)were applied to investigate the microstructure,semi-quantitative chemical composition,and mineralogy of slag samples.Ni coating demonstrated a positive effect on the mitigation of slagging.Results revealed that the thicknesses of the slag initially increased with experimental time and then inclined toward stable values for both cases(Case 1:substrate material;Case 2:modified surface).The stable thicknesses for Cases 1 and 2 were 4.91 mm and 3.95 mm,respectively.The heat transfer efficiency was improved by approximately 18.2%with the application of Ni coating for probe surface modification.The mechanism of the mitigation of slagging was investigated in this study.XRD results revealed that the content of alkali reduced when the surface was coated with Ni.The alkali significantly affected the adhesion behavior of the deposition.Hence,Ni coating showed potential in reducing slagging and increasing the efficiency of boilers.The overall study makes a contribution to a deep understanding of the effect of Ni coating on the growth characteristics of the slag.
文摘The slagging/fouling due to the accession of fireside deposits on the steam boilers decreases boiler efficiency and availability which leads to unexpected shut-downs. Since it is inevitably associated with the three major factors namely the fuel characteristics, boiler operating conditions and ash behavior, this serious slagging/fouling may be reduced by varying the above three factors. The research develops a generic slagging/fouling prediction tool based on hybrid fuzzy clustering and Artificial Neural Networks (FCANN). The FCANN model presents a good accuracy of 99.85% which makes this model fast in response and easy to be updated with lesser time when compared to single ANN. The comparison between predictions and observations is found to be satisfactory with less input parameters. This should be capable of giving relatively quick responses while being easily implemented for various furnace types.
基金the National Natural Science Foundation of China
文摘This paper applies digital image techniques to observe the slagging characteristics of blended coals in a pilot-scale furnace. Collected deposit samples were analyzed by scanning electron microscopy linked with energy-dispersive X-ray analysis （SEM-EDX）, X-ray diffraction （XRD）, and X-ray Fluorescence （XRF） to acquire the microstructure, chemical composition, and mineralogy. The deposit thickness of three blends was analyzed between their parent coal A （Datong） and coal B （Shan）, and we noted that the time to reach a stable stage decreased with the ratio of coal B. The addition of coal A into coal B could remarkably restrained the growth and thickness of ash deposits. The results of XRD analysis indicated the initial layer was predominantly comprised of the crystalline minerals quartz, anorthite, or albite except for coal B. All of the blends and coals contained quartz and Ca- to Al-silicates （Ca0.68Na0.32）（All.68Si0.32）Si2O8 in the slag layer where iron-bearing minerals （e.g., ilvaite） were altered into an amorphous phase. The result of SEM-EDX suggested that there was an elemental disparity between the coal ash and deposit.
文摘Slagging coal gasification process became a highlight of coal chemical industry in China during the last decade. Refractory lining＇ s life of slagging gasifiers is one of the most critical factors for a cost - effective operation. The paper introduces current status of coal gasification in China, lining structure of slagging gasifiers and performance of refractory lining. It also summarizes the major factors impacting on refractory wear in slagging coal gasifiers in four Chinese chemical plants, based on ten years of industrial experience. The utilizability is discussed in terms of cost -effectiveness of high chromia refractories and possibility of the alternatives.
基金Project(50576005) supported by the National Natural Science Foundation of China
文摘In order to study the slagging characteristics of boiler combustion liners during pulverized coal stream combustion, the slag samples on the surface of combustion liner were investigated by X-ray diffractometry, scan electron microscopy and energy dispersive X-ray analysis, and the transformation characteristics of the compositions and crystal phases were studied. The results show that the size of slag granules decreases as the slagging temperature increases; the crystallinity of coal ash I reduces to about 48.6% when the temperature is increased up to 1 350 ℃, and that of the coal ash II reduces to about 65% when the temperature is increased up to 1 500 ℃; the encroachment of molten coal ash to the combustion liner is strengthened. At the same time, the diffusion and the segregation of the compositions in combustion liners have selectivity, which is in favor of enhancing the content of crystal phases, weakening the conglutination among molten slag compositions and combustion liner, and avoiding yielding big clinkers. But the diffusion of the compositions in combustion liners increases the porosity and decreases the mechanical intensity of combustion liner, and makes the slag encroachment to the liner become more serious.
文摘Wear of the spent high chrome brick in slagging gasifier was studied. The result shows that erosion and spalling are the m, ain wear mechanism of high chrome brick and the CaO content of coal slag is crucial to wear of high chrome brick.
基金Supported by the High Technology Research and Development Programme of China.
文摘In this paper a brief introduction on design features,process of hot-fire check out testsand typical testing results of a 20 MWt coal-fired MHD slagging combustor is presented.Onthe basis of the testing results we conclude that all the design requirements of the combustorare satisfied.Analysis on the experimental results is also made.The reasons that causeslower rate of slag rejection are discussed,and the ways of raising slag rejection rate are con-sidered.
文摘The slagging characteristic of coal effects the safe operation of boiler unit directly, the study on coal slagging is paid more and more attention by scholars of the world. Because of the complexity of coal characteristic, the blending coals slagging characteristic is more complex than single coal. The study method of blending coals characteristic is the same as the single coal method, but the simple method can’t distinguish the blending coals slagging characteristic well and truly. This paper gives the new distinguish method of blending coals slagging characteristic based on experimentation condition, it is the rate of slag and furnace refuse. The rate of slagging on furnace wall and the refuse on furnace bottom has utilized to distinguish the slagging characteristic of coal. The result shows that the rate of slag and furnace refuse method has better veracity.
文摘The type selection of burning equipment for boilers is affected significantly by the slagging characteristics of coal. Based on the engineering statistics method, the designed furnace parameters are obtained from the 600-MW and 1 000-MW boilers with tangential firing and wall firing. The power and arrangement of the burners are analyzed. Their impacts on slagging on heating surfaces and the carbon contents in the ash and cinders are also discussed. Thermal parameters of furnace are recommended for boilers of 600 MW and 1 000 MW firing slagging coal in the design. The static or rotary classifier should be the first choice for the pulverizing system.
文摘During secondary refining of molten steel, reaction of steel-slag has great influence on the quality of steel. Taking high aluminium steel ([Al]≥0.8%) for instance, reaction control of 4[Al]+3(SiO2) = 2(Al2O3)+3[Si] was discussed by both thermodynamics calculation and industrial experiments. The results show that content of silicon increased sharply when content of SiO2 in slag exceeded 10%. In order to prevent the increment of silicon content and reoxidation for high aluminium steel, reasonable component range of LF refining slag is: %CaO/%Al2O3=1.6-1.9, %SiO2 【10. Results of the industrial experiments indicate that the CaO-Al2O3 based refining slag has strong ability of desulfurization and inclusion absorption. Average desulfurization rate is 80%, and T[O] reduces above 50% after refining, with the average sulfur content and T[O] about 0.0025% and 11×10-6,respectively, which can meet the requirements of secondary refining and obtain good castability of steel in continuous casting process.
文摘Coal is one of the main sources of energy in many parts of the world and has one of the largest reserves/production ratios amongst all the non-renewable energy sources. Gasification of coal is one among the advanced technologies that has potential to be used in a carbon constrained economy. However, gasification availability at several commercial demonstrations had run into problems associated with fouling of syngas coolers due to unpredictable flyash formation and unburnt carbon losses. Computer models of gasifiers are emerging as a powerful tool to predict gasifier performance and reliability, without expensive testing. Most computer models used to simulate gasifiers tend to model coal as a homogenous entity based on bulk properties. However, coal is a heterogeneous material and comminution during feedstock preparation produces particle classes with different physical and chemical properties. It is crucial to characterize the heterogeneity of the feedstocks used by entrained flow gasifiers. To this end, a low ash US bituminous coal that could be used as a gasifier feedstock was segregated into density and size fractions to represent the major mineral matter distributions in the coal. Float and sink method and sieving were employed to partition the ground coal. The organic and inorganic content of all density fractions was characterized for particle size distribution, heating value, ultimate analysis, proximate analysis, mineral matter composition, ash composition, and petrographic components, while size fractions were characterized for heating value, ash composition, ultimate and proximate analysis. The proximate, ultimate and high heating value analysis showed that variation in these values is limited across the range of size fractions, while the heterogeneity is significant over the range of density fractions. With respect to inorganics, the mineral matter in the heavy density fractions contribute significantly to the ash yield in the coal while contributing very little to its heating value. The ash yield across the size fractions exhibits a bimodal distribution. The heterogeneity is also significant with respect to the base-to-acid ratio across the size and density fractions. The results indicate that the variations in organic and inorganic content over a range of density and size classes are significant, even in the low ash, vitrinite rich coal sample characterized here. Incorporating this information appropriately into particle population models used in gasifier simulations will significantly enhance their accuracy of performance predictions.
基金This work was financially supported by Beijing Municipal Science and Technology Commission(No.Z181100005118006).
文摘In order to mitigate the slagging risks of high-alkali coal (HAC) gasification while optimizing the operating temperatures for practical application,the experimental and calculational works were performed on the horizontal tubular furnace system and the FactSage 7.2 software,respectively.The slagging tendencies of three HACs were anticipated by applying different indexes of ash chemistry characteristics prior to experiments,but the determined results were found inconsistent.The relationship between Na retained ratio (RNa) and the ash fusion temperatures (AFTs) of gasification residues demonstrated that the AFTs of coal with high RNa are low,while AFTs of coal with low RNa are high.Nevertheless,when the residues contained a large number of calcium-containing silicates and aluminosilicates,the ATFs were reduced significantly even if its RNa stayed at a low level.Furthermore,the operating temperatures of the three coals (in order of Mulei coal,Shaerhu coal,and Tietou coal) were suggested to be controlled below 1150℃,1100℃,and 950℃,respectively.
基金financially supported by National Natural Science Foundation of China(No.22008236)。
文摘Some ash related problems,such as slagging at furnace bottom and fouling at the air pre-heater surface,are frequently encountered during circulating fluidized bed gasification(CFBG)of Zhundong coal.Low ash fusion temperatures(AFTs)and intense sodium release should be responsible for those problems.In industry,coal blending is deemed to be a feasible method to both improve AFTs and control sodium release.In this work,Wuhai coal was selected as blending coal.The ratio is varied from 0%to 40%by mass with 10%interval.The mixed samples were gasified by steam at 950°C in a lab-scale furnace.Some key indices,such as sodium release behaviors,ash slagging characteristics and char gasification performances,were investigated by ICP-OES,AFTs,XRD and TG analyzers,respectively.The results indicated that coal blending could significantly decrease sodium release behaviors.For ash slagging characteristics,it is surprised to find that three out of four AFTs(deformation temperature,softening temperature,hemispherical temperature)show an U-shaped correlation with blending ratio,indicating that a low ratio possibly causes more severe ash slagging problem.It is ascribed to the formation of substantial percentage of fusible Na-containing silicates and aluminosilicates.In addition,coal blending greatly increases ST-DT,implying that the ability of resistance to bed temperature fluctuation is markedly enhanced.Due to the high level of alkali and alkaline species,the synergistic effect is clearly observed during co-gasification.Taking all key indices into consideration,30%blending ratio of Wuhai coal is recommended.
基金the Natural Science Foundation of China(Nos.52176187,51976075)the National Natural Science Funds for Distinguished Young Scholar(No.52125601).
文摘As a low-value solid waste fuel,asphalt rock is prone to slagging even under fluidized bed condition.The purpose of this study is to improve the slagging characteristics of asphalt rock by adding the mineral additives CaCO_(3),MgO,and Kaolin.The results showed that the K,Al,Ca salts in asphalt rock ash will evolve at different temperatures and exist mainly as K_(2)SO_(4),KAlSiO_(4),Al_(2)O_(3)·SiO_(2),Al_(2)O_(3),CaSO_(4),and CaSiO_(3).The CaSO_(4)formed from sulfur oxides and calcium-containing compounds is the main factor in asphalt rock slagging and can be facilitated by CaSiO_(3)with a small amount of CaCO_(3).The MgO can form MgCa(SiO_(3))_(2)with a high melting point and helps raise the ash fusion temperatures.In addition,the Kaolin will promote the formation of low-temperature eutectics,resulting in a slight decrease in ash fusion temperatures.Through optimization,it was found that with the addition of 9.0%MgO+9.0%Kaolin+2.0%CaCO_(3)(in weight),the slagging ratio and pressure difference of asphalt rock under fluidized bed conditions decreased from 6.5%to 4.2%and from 6.0 Pa to 4.0 Pa,respectively.By combining simulation and experimental methods,it has been shown that appropriate mineral additives of CaCO_(3),MgO,and Kaolin can effectively improve the slagging characteristics of asphalt rock.
基金supported by the National Key Research and Development Program of China(No.2023YFB3712401),the National Natural Science Foundation of China(No.52274301)the Aeronautical Science Foundation of China(No.2023Z0530S6005)the Ningbo Yongjiang Talent-Introduction Programme(No.2022A-023-C).
文摘The viscosity of refining slags plays a critical role in metallurgical processes.However,obtaining accurate viscosity data remains challenging due to the complexities of high-temperature experiments,often relying on empirical models with limited predictive capabilities.This study focuses on the influence of optical basicity on viscosity in CaO-Al_(2)O_(3)-based refining slags,leveraging machine learning to address data scarcity and improve prediction accuracy.An automated framework for algorithm integration,parameter tuning,and evaluation ranking framework(Auto-APE)is employed to develop customized data-driven models for various slag systems,including CaO-Al_(2)O_(3)-SiO_(2),CaO-Al_(2)O_(3)-CaF_(2),CaO-Al_(2)O_(3)-SiO_(2)-MgO,and CaO-Al_(2)O_(3)-SiO_(2)-MgO-CaF_(2).By incorporating optical basicity as a key feature,the models achieve an average validation error of 8.0%to 15.1%,significantly outperforming traditional empirical models.Additionally,symbolic regression is introduced to rapidly construct domain-specific features,such as optical basicity-like descriptors,offering a potential breakthrough in performance prediction for small datasets.This work highlights the critical role of domain-specific knowledge in understanding and predicting viscosity,providing a robust machine learning-based approach for optimizing refining slag properties.
基金supported by the National Natural Science Foundation of China(No.52274318).
文摘A full-sectional microstructure characterization method was developed to investigate the formation of coarse slag rims during the continuous casting of hypo-peritectic steel.The cross-sectional microstructural analysis of typical slag rims for two highly crystalline powders revealed that their formation was primarily driven by the solidification of the liquid slag.Distinct differences were observed in the microstructures of slag rims from the two powders.Powder A(characterized by a higher breaking temperature and viscosity)displayed alternating lamellar microstructures of coarse and fine phases,with the coarse phases composed of akermanite-gehlenite transition phases.In contrast,powder B(with a lower breaking temperature and viscosity)predominantly comprised regular akermanite-gehlenite crystals interspersed with a certain amount of glassy phases.Numerical simulations of a three-phase fluid flow coupled with heat transfer indicate that slag rim formation correlates with mold oscillation.Solidification of the liquid slag at the slag rim front predominantly occurs during the negative stroke of the mold oscillation.The average heating rate during the ascending stage of the mold reaches approximately 100 K·s^(−1),whereas the average cooling rate during the descending stage attains 400 K·s^(−1).This temperature variation leads to the formation of lamellar microstructures,whereas the ascending stage promotes the formation of coarse structures and thicker slag rims.Based on the powder properties,two distinct formation pathways exist for highly crystalline mold powders.For the powders with a higher breaking temperature,higher viscosity,and narrower solidification range(powder A),coarse microstructures and thicker slag rims were preferentially formed.For powders with lower breaking temperature and viscosity and wider solidification ranges(powder B),the liquid slag resisted rapid solidification,and the extended mushy zone allowed the partial liquid slag to persist at the slag rim front,promoting the formation of a thin slag rim.This study enhances the understanding of slag rim formation in highly crystalline mold powders and provides critical insights into the control of longitudinal surface cracks in hypo-peritectic steel.
基金supported by National Natural Science Foundation of China(Nos.52204309,52174277 and 52374300)Fundamental Funds for the Central Universities(No.N2425026)。
文摘Manganese is a major impurity in acidic vanadium-bearing leaching solutions,but its effects on vanadium precipitation via hydrolysis and acidic ammonium salts remain unclear.In this study,vanadium-bearing leachates with varying manganese concentrations(VL-cMn)were prepared through calcium,a calcium-manganese composite,and manganese-based roasting of vanadium slag(VS)to investigate the influence of manganese on vanadium precipitation behavior during hydrolysis precipitation(HP)and ammonium salt precipitation(AP),as well as the microscopic characteristics and purity of the resulting V_(2)O_(5) products.The results showed that increasing the pH mitigated the negative effects of Mn on the V precipitation rate during HP.However,as the manganese concentration increased from 5.69 to 15.38 g/L,the V precipitation rate gradually declined at higher temperatures and longer reaction times.The precipitates exhibited increased microstructural density,which might had contributed to the formation of Mn-bearing phases.Additionally,the average grain size of V_(2)O_(5) was reduced and the particles were increasingly agglomerated,leading to a 2.55%decrease in product purity.For AP,as manganese concentration increased,raising the pH counteracted the negative impact of Mn on the V precipitation rate and reduced the required amount of ammonium sulfate.Moreover,Mn was unevenly adsorbed on the surface of the precipitates.Although V_(2)O_(5) grains gradually shrank and became denser,there was no significant effect on the final product purity,which remained above 99.3%.In conclusion,roasting with added manganese salts influenced the hydrolysis of vanadium but had no significant effect on acidic ammonium salt precipitation.
基金This work was financially supported by the Australian Research Council(ARC)under its Industrial Research Training Hub(IH170100009)scheme for the joint project between Monash University and Shanghai Boiler Works Co Ltd.Md Tanvir Alam would like to thank Monash University for his Ph.D Scholarship。
文摘Gasification or combustion of coal and biomass is the most important form of power generation today.However,the use of coal/biomass at high temperatures has an inherent problem related to the ash generated.The formation of ash leads to a problematic phenomenon called slagging.Slagging is the accumulation of molten ash on the walls of the furnace,gasifier,or boiler and is detrimental as it reduces the heat transfer rate,and the combustion/gasification rate of unburnt carbon,causes mechanical failure,high-temperature corrosion and on occasions,superheater explosions.To improve the gasifier/combustor facility,it is very important to understand the key ash properties,slag characteristics,viscosity and critical viscosity temperature.This paper reviews the content,compositions,and melting characteristics of ashes in differently ranked coal and biomass,and discusses the formation mechanism,characteristics,and structure of slag.In particular,this paper focuses on low-rank coal and biomass that have been receiving increased attention recently.Besides,it reviews the available methodologies and formulae for slag viscosity measurement/prediction and summarizes the current limitations and potential applications.Moreover,it discusses the slagging behavior of different ranks of coal and biomass by examining the applicability of the current viscosity measurement methods to these fuels,and the viscosity prediction models and factors that affect the slag viscosity.This review shows that the existing viscosity models and slagging indices can only satisfactorily predict the viscosity and slagging propensity of high-rank coals but cannot predict the slagging propensity and slag viscosity of low-rank coal,and especially biomass ashes,even if they are limited to a particular composition only.Thus,there is a critical need for the development of an index,or a model or even a measurement method,which can predict/measure the slagging propensity and slag viscosity correctly for all low-rank coal and biomass ashes.
