We investigated the effects of calcination temperature(950-1450℃),steel slag content,and the total chromium content of steel slag on the Cr^(6+)contents of clinker samples produced using steel slags with different ch...We investigated the effects of calcination temperature(950-1450℃),steel slag content,and the total chromium content of steel slag on the Cr^(6+)contents of clinker samples produced using steel slags with different chromium contents.Additionally,the reactions of chromium in clinker(produced using steel slag)during calcination were studied.It is found that Cr^(6+)conversion increases with increasing calcination temperature to 1250℃,reaching a maximum of 43%-79%,before decreasing to 18%-42%at 1450℃.Cr^(6+)is mainly formed by the oxidation of trivalent chromium(Cr^(3+))during the solid-phase reaction stage of clinker calcination.Furthermore,the Cr^(6+)content of a clinker sample is proportional to the chromium content of its raw meal precursor and is mainly in the form of water-insoluble calcium chromate(CaCrO_(4)).The chromium in clinker is mainly distributed in tricalcium aluminate and tetracalcium aluminoferrite,however,some is present in silicate minerals.We expect to inform the monitoring and control of the Cr^(6+)content of clinker(produced using steel slag)and resulting cement.展开更多
Considering the fact that free calcium oxide content is an important parameter to evaluate the quality of cement clinker, it is very significant to predict the change of free calcium oxide content through adjusting th...Considering the fact that free calcium oxide content is an important parameter to evaluate the quality of cement clinker, it is very significant to predict the change of free calcium oxide content through adjusting the parameters of processing technique. In fact, the making process of cement clinker is very complex. Therefore, it is very difficult to describe this relationship using the conventional mathematical methods. Using several models, i e, linear regression model, nonlinear regression model, Back Propagation neural network model, and Radial Basis Function （RBF） neural network model, we investigated the possibility to predict the free calcium oxide content according to selected parameters of the production process. The results indicate that RBF neural network model can predict the free lime content with the highest precision （1.3%） among all the models.展开更多
A new composition of Portland cement clinker was studied, in which KH, SM and IM was 0.98,2.4 and 2.4 respectively as well as its meal added 1%CuO （in mass）. Fired at 1 200℃,1 350℃,1 400℃ and 1 450℃ for 30 min, ...A new composition of Portland cement clinker was studied, in which KH, SM and IM was 0.98,2.4 and 2.4 respectively as well as its meal added 1%CuO （in mass）. Fired at 1 200℃,1 350℃,1 400℃ and 1 450℃ for 30 min, the resultant mineral phases component and mineral morphology were analyzed. The performances of the cement which was made of clinker burned at 1 450℃ and fly ash were determined. By means of QXRD, XRD and optical microscopy, it is shown that the clinker burnt at 1 450℃ has the larger size crystals and distinct crystal interface, in which the C3S content is 73.37% and the mineral phases is dominantly C3S, following by minor C2S, C3A and tetracalcium aluminoferrite. The results reveal that a new type of high C3S content clinker can completely be made by traditional temperature-time schedule. The performances of the cement produced from this clinker with addtion of 50% fly ash and 5% gupsum were in agreement with the 32.5 strength grade of Portland fly-ash cement. The results also show that the clinker has a significant effect of saving energy and utilizing waste slag.展开更多
The effect of CuO on the clinkering process and mineral structure, components and morphology of high C3S cement clinker was studied. One reference mixture was prepared according to the potential mineral phase componen...The effect of CuO on the clinkering process and mineral structure, components and morphology of high C3S cement clinker was studied. One reference mixture was prepared according to the potential mineral phase components C3S=75%, C3A=7%, C4AF=18% and then was mixed, respectively, with 0.5%, 1%, 1.5%, 2%, 2.5% and 4% CuO. All samples were heated at a rate of 10°C/min to the design temperatures and then maintained for 40 min. Analyses by the glycerol-ethanol method, XRD and SEM-EDS show that the minimum of free lime （f-CaO） content was related to temperature and CuO amount. The higher the temperature, the lower the amount of CuO corresponding to the f-CaO minimum content. CuO promotes the formation and growth of C3S and C4AF and a new compound is found. In addition, these phenomena are discussed theoretically. In conclusion, CuO alters the burnability and the formation and structure of C3S in a high C3S cement system.展开更多
The paper reports the development of cement clinker-supported nickel （with metal loadings of 5 wt%, 10 wt%, 15 wt% and 20 wt%） catalysts for glycerol dry （CO2） reforming reaction. XRF results showed that CaO const...The paper reports the development of cement clinker-supported nickel （with metal loadings of 5 wt%, 10 wt%, 15 wt% and 20 wt%） catalysts for glycerol dry （CO2） reforming reaction. XRF results showed that CaO constituted 62.0% of cement clinker. The physicochemical characterization of the catalysts revealed 32-folds increment of BET surface area （SBET） with the addition of nickel metal into the cement clinker, which was also corroborated by FESEM images. Significantly, XRD results suggested different types of Ni oxides formation with Ni loading, whilst Ca3SiO5 and Ca2Al0.67Mn0.33FeO5 were the main crystallite species for pure cement clinker. Temperature-programmed reduction analysis yielded three domains of H2 reduction peaks, viz. centered at approximately 750 K referred to as type-Ⅰ peaks, another peaks at 820 K denoted as type-Ⅱ peaks and the highest reduction peaks, type-Ⅲ recorded at above 1000 K. 20 wt% Ni was found to be the best loading with the highest XG and H2 yield, whilst the lowest methanation activity. Syngas with lower H2/CO ratios （0.6 to 1.5） were readily produced from glycerol dry reforming at CO2-to-Glycerol feed ratio （CGR） of unity. Nonetheless, carbon deposit comprised of whisker type （Cv） and graphitic-like type （Cc） species were found to be in majority on 20 wt%Ni/CC catalysts.展开更多
Cement clinker is burnt at the rapid heating rate has the obvious effect of saving energy due to the low burning temperature and short burning time. This kind of technique is being researched actively in recent years,...Cement clinker is burnt at the rapid heating rate has the obvious effect of saving energy due to the low burning temperature and short burning time. This kind of technique is being researched actively in recent years, but the systematical theory investigation about the formation mechanism of clinker minerals under this condition has not been reported. In this paper, the formation mechanism of Portland cement clinker minerals in rapid burning was studied by means of DTA, SEM, EPMA, XRD and other conventional testing methods by using a special burning equipment.展开更多
In this paper for saving energy two different burning methods of cement clinker formation have been studied.One is the rapid burning method and the other is ordinary burning method simulating rotary kiln,and they are ...In this paper for saving energy two different burning methods of cement clinker formation have been studied.One is the rapid burning method and the other is ordinary burning method simulating rotary kiln,and they are compared by the kinetic point of view.The result reveals that the activation energy of rapid burning is much lower than ordinary burning.For looking into the cause, the main raw material—lime stone was burnt by the same two methods and the structure of product CaO has been detected.It can be found that the microstructure of CaO produced by rapid burning is looser;lattices constants are greater;crystal defects are more and particle size is smaller than that produced by ordinary burning.These cause the chemical reaction more active.So the activation energy of clinker formation of rapid burning is much lower than that of the ordinary burning.展开更多
The relation between the melting point of Portland cement raw meal and its heating rate have been studied. The raw meal was burnt at different heating rate ranging from 10 similar to 900 degrees C/min Dy the following...The relation between the melting point of Portland cement raw meal and its heating rate have been studied. The raw meal was burnt at different heating rate ranging from 10 similar to 900 degrees C/min Dy the following methods: (A) in electric resistance furnace; (B) in DTA-TG analyzer with infrared ray focused heating; (C) in high temperature microscope with electron stream heating. Based on thermal analysis theory and melt theory and the tests above, it is found that melting point T-m of cement raw meal decreases with the increased heating rate Phi during burning in the following relation: T-m=1280-0.107 empty set.展开更多
The forming temperature of Clinker melt underdifferent burning conditions has been studied by appearance examination and thermal shrinker determination, and the viscosity of melt has been discussed by studying the coo...The forming temperature of Clinker melt underdifferent burning conditions has been studied by appearance examination and thermal shrinker determination, and the viscosity of melt has been discussed by studying the coordination number of Al^(3+) and Fe^(3+) in cement clinker burned by different method with x^- ray fluorescence analysis and Moss- bauer spectroscopy. The results show that the clin- ker melt under rapid burning may come into exis- tence at lower temperature and It's viscosity is lower. So the forming processes of clinker may be different at rapid burning from ordinary burning. They are probably an important factor to promote the formation of clinker burned at lower temperature with rapid burning method.展开更多
Ferrochrome slag is a kind of industrial waste containing Cr^(6+)and is produced in the process of silico ferrochrome smelting.On the basis of analyzing the chemical composition and mineral composition of ferrochrome ...Ferrochrome slag is a kind of industrial waste containing Cr^(6+)and is produced in the process of silico ferrochrome smelting.On the basis of analyzing the chemical composition and mineral composition of ferrochrome slag,this paper has put forward a technology of green portland cement clinker calcinated from ferrochrome slag.In the experiment,physical chemical changes of cement clinker in the burning process of ferrochrome slag were investigated.The effects of calcinating temperature and clinker cooling rate on the solubility value of Cr^(6+)were analyzed.The results indicated that when the calcinating temperature is above 1450℃,and the cooling rate is beyond 120℃/min,Cr^(6+)in cement clinker is almost insoluble.展开更多
Based on the sandwich test, adherence mechanisms of cement clinker on various basic bricks were tackled by microstructural observations with help of cathodolumi-nescence technique. Doloma based bricks offer sufficient...Based on the sandwich test, adherence mechanisms of cement clinker on various basic bricks were tackled by microstructural observations with help of cathodolumi-nescence technique. Doloma based bricks offer sufficient lime to react with clinker, forming C3S rich layer and initializing superior adherence. However, clinker with low silica ratio leads to MgO agglomeration at the interface of doloma bricks, which reduces adherence strength. On magnesia spinel bricks , fine, crystalline spinel easily reacts with lime containing phases from clinker to form low-melting phases and belite zone, which shows high adherence performance. Lack of fine spinel in magnesia spinel bricks results in poor adherence.展开更多
The decomposition speed and mechanism of alite in Portland cement clinker are studied by means of optical microscopy, EPMA, XRD and chemical analysis. The results show that alite in portland cement clinker decomposes...The decomposition speed and mechanism of alite in Portland cement clinker are studied by means of optical microscopy, EPMA, XRD and chemical analysis. The results show that alite in portland cement clinker decomposes at the maximum speed when the temperature is at 1025 to approximately 1175 degree C. It takes about 40 hours for the alite in clinker burnt in the rotary kiln to completely decompose at 1175 degree C, and about 68 hours for the alite burnt in RSP-kiln. The presence of CaF//2 or CaSO//4 greatly affects the decomposition speed of alite. The former resists alite to decompose but the latter accelerates it and enables alite to decompose completely within 6 hours or less. (Author abstract) 3 Refs.展开更多
Clinker has long been regarded as a critical factor for cement hydration and solidification.α-C2S and β-C2S in 2CaO·SiO2（C2S） phase and C3S Monoclinic 1（C3S M1） and C3S Monoclinic 3 （C3S M3） in 3CaO·...Clinker has long been regarded as a critical factor for cement hydration and solidification.α-C2S and β-C2S in 2CaO·SiO2（C2S） phase and C3S Monoclinic 1（C3S M1） and C3S Monoclinic 3 （C3S M3） in 3CaO·SiO2 （C3S） phase were clearly recorded in the 29Si MAS NMR spectra.The content of C3S phase in the clinker deduced from the fine peak analysis coincides with the phase quantification analysis calculated by the Taylor-Bogue method based on XRF,which also accords to the statistical data in industrial production.NMR provides a proof that C3S M1 and β-C2S phases have a prior reaction in the early age hydration of clinker,and demonstrates that aluminum coordination changes from tetracoordinated 4CaO·Al2O3·Fe2O3（C4AF） to hexacoordinated [Ca2Al（OH）6]（SO4）0.3·3H2O（Aft） in one day hydration and changes to the 3CaO·Al2O3·CaSO4·nH2O （Afm） in a seven-day hydration.展开更多
Quantitative phase analysis of Portland cement clinker samples was performed using an adaptation of the Rietveld method.The Rietveld quantitative analysis program,originally in Fortran 77 code,was significantly modifi...Quantitative phase analysis of Portland cement clinker samples was performed using an adaptation of the Rietveld method.The Rietveld quantitative analysis program,originally in Fortran 77 code,was significantly modified in visual basic code with windows 9X graph user interface,which is free from the constraint of direct utilizable memory 640 k,and can be conveniently operated under the windows environment.The Rietveld quantitative method provides numerous advantages over conventional XRD quantitative method,especially in the intensity anomalies and superposition problems.Examples of its use are given with the results from other methods.It is concluded that,at present,the Rietveld method is the most suitable one for quantitative phase analysis of Portland cement clinker.展开更多
When raw materials were preheated to 1000-1300 ℃ by electricity and microwave was inputted for 1 min 5 s-4 mins, then alunminate clinkers were obtained. The f-CaO contents,XRD patterns and lithofacies analysis show t...When raw materials were preheated to 1000-1300 ℃ by electricity and microwave was inputted for 1 min 5 s-4 mins, then alunminate clinkers were obtained. The f-CaO contents,XRD patterns and lithofacies analysis show that the microwave processing accelerates the clinkering reaction,and Fe_2O_3 is contributed to the aluminate cement clinkering. The appearance of liquid phase in process of microwave heating increases the microwave absorbability of materials greatly.展开更多
Two different methods of burning ce- ment clinker, a rapid burningmethod and an ordinary burning method used in rotary kiln,respectively, were compared in the laboratory. By means ofdetermining f_cao in the clinkers, ...Two different methods of burning ce- ment clinker, a rapid burningmethod and an ordinary burning method used in rotary kiln,respectively, were compared in the laboratory. By means ofdetermining f_cao in the clinkers, rate constant K_r and diffusionactivation en- ergy E_a in the two processes of clinker formationwere cal- culated by using Ginstling-Brounshtein diffusion equationand Arrhenius equation.展开更多
In this paper ,how and why MgO acts on the burning of white cement clinker and increases the whiteness were found by means of common detection and EPMA. It was shown that MgO is a kind of effective mineralizer and bri...In this paper ,how and why MgO acts on the burning of white cement clinker and increases the whiteness were found by means of common detection and EPMA. It was shown that MgO is a kind of effective mineralizer and brightener.展开更多
Managers of cement plants are gradually becoming aware of the need for soft sensors in product quality assessment. Cement clinker quality parameters are mostly measured by offline laboratory analysis or by the use of ...Managers of cement plants are gradually becoming aware of the need for soft sensors in product quality assessment. Cement clinker quality parameters are mostly measured by offline laboratory analysis or by the use of online analyzers. The measurement delay and cost, associated with these methods, are a concern in the cement industry. In this study, a regression-based model was developed to predict the clinker quality parameters as a function of the raw meal quality and the kiln operating variables. This model has mean squared error, coefficient of determination, worst case relative error and variance account for (in external data) given as 8.96 × 10<sup>–7</sup>, 0.9999, 2.17% and above 97%, respectively. Thus, it is concluded that the developed model can provide real time estimates of the clinker quality parameters and capture wider ranges of real plant operating conditions from first principle-based cement rotary kiln models. Also, the model developed can be utilized online as soft sensor since they contain only variables that are easily measured online.展开更多
Optimization of the content of tricalcium silicate（C 3 S）of high cementing clinker was investigated.The content of free-CaO（f-CaO）,mineral composite,the content of C 3 S in the clinker and the hydration product we...Optimization of the content of tricalcium silicate（C 3 S）of high cementing clinker was investigated.The content of free-CaO（f-CaO）,mineral composite,the content of C 3 S in the clinker and the hydration product were analyzed by chemical analysis and X-ray diffraction（XRD）.＂K Value＂method of QXRD was selected as a quantitative analysis way to measure the content of C 3 S,and the strength of cement paste was determined.The results show that at a water cement ratio of 0.29,the strength of cement paste with 73%C 3 S can be up to 97.5 MPa at 28 days age.The strength at 28 d of cement with 73%C 3 S is 16%higher than that with 78%C 3 S at water requirement for normal consistency.The relationship between the strength of high cementing Portland cement and the content of C 3 S in the clinker is nonlinear.According to the strength of cement paste,the optimal content of C 3 S in cement clinker is around 73%in this paper.展开更多
文摘We investigated the effects of calcination temperature(950-1450℃),steel slag content,and the total chromium content of steel slag on the Cr^(6+)contents of clinker samples produced using steel slags with different chromium contents.Additionally,the reactions of chromium in clinker(produced using steel slag)during calcination were studied.It is found that Cr^(6+)conversion increases with increasing calcination temperature to 1250℃,reaching a maximum of 43%-79%,before decreasing to 18%-42%at 1450℃.Cr^(6+)is mainly formed by the oxidation of trivalent chromium(Cr^(3+))during the solid-phase reaction stage of clinker calcination.Furthermore,the Cr^(6+)content of a clinker sample is proportional to the chromium content of its raw meal precursor and is mainly in the form of water-insoluble calcium chromate(CaCrO_(4)).The chromium in clinker is mainly distributed in tricalcium aluminate and tetracalcium aluminoferrite,however,some is present in silicate minerals.We expect to inform the monitoring and control of the Cr^(6+)content of clinker(produced using steel slag)and resulting cement.
基金NSFC (No. 60808024)the Fundamental Research Funds for the Central Universities (Wuhan University of Technology)
文摘Considering the fact that free calcium oxide content is an important parameter to evaluate the quality of cement clinker, it is very significant to predict the change of free calcium oxide content through adjusting the parameters of processing technique. In fact, the making process of cement clinker is very complex. Therefore, it is very difficult to describe this relationship using the conventional mathematical methods. Using several models, i e, linear regression model, nonlinear regression model, Back Propagation neural network model, and Radial Basis Function （RBF） neural network model, we investigated the possibility to predict the free calcium oxide content according to selected parameters of the production process. The results indicate that RBF neural network model can predict the free lime content with the highest precision （1.3%） among all the models.
基金Funded by 973 National Key Scientific Project Foundation (No.001CB610701) the University Key Laboratoty Foundation of Jiangshu Province (No.KJS03021)the Sixth Outstanding Talents Foundation.
文摘A new composition of Portland cement clinker was studied, in which KH, SM and IM was 0.98,2.4 and 2.4 respectively as well as its meal added 1%CuO （in mass）. Fired at 1 200℃,1 350℃,1 400℃ and 1 450℃ for 30 min, the resultant mineral phases component and mineral morphology were analyzed. The performances of the cement which was made of clinker burned at 1 450℃ and fly ash were determined. By means of QXRD, XRD and optical microscopy, it is shown that the clinker burnt at 1 450℃ has the larger size crystals and distinct crystal interface, in which the C3S content is 73.37% and the mineral phases is dominantly C3S, following by minor C2S, C3A and tetracalcium aluminoferrite. The results reveal that a new type of high C3S content clinker can completely be made by traditional temperature-time schedule. The performances of the cement produced from this clinker with addtion of 50% fly ash and 5% gupsum were in agreement with the 32.5 strength grade of Portland fly-ash cement. The results also show that the clinker has a significant effect of saving energy and utilizing waste slag.
基金Funded by Chinese 973 National Key Scientific Projects (Nos.2009CB623102 and 2009Cb623104)
文摘The effect of CuO on the clinkering process and mineral structure, components and morphology of high C3S cement clinker was studied. One reference mixture was prepared according to the potential mineral phase components C3S=75%, C3A=7%, C4AF=18% and then was mixed, respectively, with 0.5%, 1%, 1.5%, 2%, 2.5% and 4% CuO. All samples were heated at a rate of 10°C/min to the design temperatures and then maintained for 40 min. Analyses by the glycerol-ethanol method, XRD and SEM-EDS show that the minimum of free lime （f-CaO） content was related to temperature and CuO amount. The higher the temperature, the lower the amount of CuO corresponding to the f-CaO minimum content. CuO promotes the formation and growth of C3S and C4AF and a new compound is found. In addition, these phenomena are discussed theoretically. In conclusion, CuO alters the burnability and the formation and structure of C3S in a high C3S cement system.
基金supported by Ministry of Education,Malaysia through MTUN(No.RDU121216)
文摘The paper reports the development of cement clinker-supported nickel （with metal loadings of 5 wt%, 10 wt%, 15 wt% and 20 wt%） catalysts for glycerol dry （CO2） reforming reaction. XRF results showed that CaO constituted 62.0% of cement clinker. The physicochemical characterization of the catalysts revealed 32-folds increment of BET surface area （SBET） with the addition of nickel metal into the cement clinker, which was also corroborated by FESEM images. Significantly, XRD results suggested different types of Ni oxides formation with Ni loading, whilst Ca3SiO5 and Ca2Al0.67Mn0.33FeO5 were the main crystallite species for pure cement clinker. Temperature-programmed reduction analysis yielded three domains of H2 reduction peaks, viz. centered at approximately 750 K referred to as type-Ⅰ peaks, another peaks at 820 K denoted as type-Ⅱ peaks and the highest reduction peaks, type-Ⅲ recorded at above 1000 K. 20 wt% Ni was found to be the best loading with the highest XG and H2 yield, whilst the lowest methanation activity. Syngas with lower H2/CO ratios （0.6 to 1.5） were readily produced from glycerol dry reforming at CO2-to-Glycerol feed ratio （CGR） of unity. Nonetheless, carbon deposit comprised of whisker type （Cv） and graphitic-like type （Cc） species were found to be in majority on 20 wt%Ni/CC catalysts.
文摘Cement clinker is burnt at the rapid heating rate has the obvious effect of saving energy due to the low burning temperature and short burning time. This kind of technique is being researched actively in recent years, but the systematical theory investigation about the formation mechanism of clinker minerals under this condition has not been reported. In this paper, the formation mechanism of Portland cement clinker minerals in rapid burning was studied by means of DTA, SEM, EPMA, XRD and other conventional testing methods by using a special burning equipment.
文摘In this paper for saving energy two different burning methods of cement clinker formation have been studied.One is the rapid burning method and the other is ordinary burning method simulating rotary kiln,and they are compared by the kinetic point of view.The result reveals that the activation energy of rapid burning is much lower than ordinary burning.For looking into the cause, the main raw material—lime stone was burnt by the same two methods and the structure of product CaO has been detected.It can be found that the microstructure of CaO produced by rapid burning is looser;lattices constants are greater;crystal defects are more and particle size is smaller than that produced by ordinary burning.These cause the chemical reaction more active.So the activation energy of clinker formation of rapid burning is much lower than that of the ordinary burning.
文摘The relation between the melting point of Portland cement raw meal and its heating rate have been studied. The raw meal was burnt at different heating rate ranging from 10 similar to 900 degrees C/min Dy the following methods: (A) in electric resistance furnace; (B) in DTA-TG analyzer with infrared ray focused heating; (C) in high temperature microscope with electron stream heating. Based on thermal analysis theory and melt theory and the tests above, it is found that melting point T-m of cement raw meal decreases with the increased heating rate Phi during burning in the following relation: T-m=1280-0.107 empty set.
文摘The forming temperature of Clinker melt underdifferent burning conditions has been studied by appearance examination and thermal shrinker determination, and the viscosity of melt has been discussed by studying the coordination number of Al^(3+) and Fe^(3+) in cement clinker burned by different method with x^- ray fluorescence analysis and Moss- bauer spectroscopy. The results show that the clin- ker melt under rapid burning may come into exis- tence at lower temperature and It's viscosity is lower. So the forming processes of clinker may be different at rapid burning from ordinary burning. They are probably an important factor to promote the formation of clinker burned at lower temperature with rapid burning method.
基金Scientific and Technological Key Task Project of Hunan Province(Code:95-19516)
文摘Ferrochrome slag is a kind of industrial waste containing Cr^(6+)and is produced in the process of silico ferrochrome smelting.On the basis of analyzing the chemical composition and mineral composition of ferrochrome slag,this paper has put forward a technology of green portland cement clinker calcinated from ferrochrome slag.In the experiment,physical chemical changes of cement clinker in the burning process of ferrochrome slag were investigated.The effects of calcinating temperature and clinker cooling rate on the solubility value of Cr^(6+)were analyzed.The results indicated that when the calcinating temperature is above 1450℃,and the cooling rate is beyond 120℃/min,Cr^(6+)in cement clinker is almost insoluble.
文摘Based on the sandwich test, adherence mechanisms of cement clinker on various basic bricks were tackled by microstructural observations with help of cathodolumi-nescence technique. Doloma based bricks offer sufficient lime to react with clinker, forming C3S rich layer and initializing superior adherence. However, clinker with low silica ratio leads to MgO agglomeration at the interface of doloma bricks, which reduces adherence strength. On magnesia spinel bricks , fine, crystalline spinel easily reacts with lime containing phases from clinker to form low-melting phases and belite zone, which shows high adherence performance. Lack of fine spinel in magnesia spinel bricks results in poor adherence.
文摘The decomposition speed and mechanism of alite in Portland cement clinker are studied by means of optical microscopy, EPMA, XRD and chemical analysis. The results show that alite in portland cement clinker decomposes at the maximum speed when the temperature is at 1025 to approximately 1175 degree C. It takes about 40 hours for the alite in clinker burnt in the rotary kiln to completely decompose at 1175 degree C, and about 68 hours for the alite burnt in RSP-kiln. The presence of CaF//2 or CaSO//4 greatly affects the decomposition speed of alite. The former resists alite to decompose but the latter accelerates it and enables alite to decompose completely within 6 hours or less. (Author abstract) 3 Refs.
基金Funded by National Basic Research Program of China(No.2009CB623100)
文摘Clinker has long been regarded as a critical factor for cement hydration and solidification.α-C2S and β-C2S in 2CaO·SiO2（C2S） phase and C3S Monoclinic 1（C3S M1） and C3S Monoclinic 3 （C3S M3） in 3CaO·SiO2 （C3S） phase were clearly recorded in the 29Si MAS NMR spectra.The content of C3S phase in the clinker deduced from the fine peak analysis coincides with the phase quantification analysis calculated by the Taylor-Bogue method based on XRF,which also accords to the statistical data in industrial production.NMR provides a proof that C3S M1 and β-C2S phases have a prior reaction in the early age hydration of clinker,and demonstrates that aluminum coordination changes from tetracoordinated 4CaO·Al2O3·Fe2O3（C4AF） to hexacoordinated [Ca2Al（OH）6]（SO4）0.3·3H2O（Aft） in one day hydration and changes to the 3CaO·Al2O3·CaSO4·nH2O （Afm） in a seven-day hydration.
文摘Quantitative phase analysis of Portland cement clinker samples was performed using an adaptation of the Rietveld method.The Rietveld quantitative analysis program,originally in Fortran 77 code,was significantly modified in visual basic code with windows 9X graph user interface,which is free from the constraint of direct utilizable memory 640 k,and can be conveniently operated under the windows environment.The Rietveld quantitative method provides numerous advantages over conventional XRD quantitative method,especially in the intensity anomalies and superposition problems.Examples of its use are given with the results from other methods.It is concluded that,at present,the Rietveld method is the most suitable one for quantitative phase analysis of Portland cement clinker.
文摘When raw materials were preheated to 1000-1300 ℃ by electricity and microwave was inputted for 1 min 5 s-4 mins, then alunminate clinkers were obtained. The f-CaO contents,XRD patterns and lithofacies analysis show that the microwave processing accelerates the clinkering reaction,and Fe_2O_3 is contributed to the aluminate cement clinkering. The appearance of liquid phase in process of microwave heating increases the microwave absorbability of materials greatly.
文摘Two different methods of burning ce- ment clinker, a rapid burningmethod and an ordinary burning method used in rotary kiln,respectively, were compared in the laboratory. By means ofdetermining f_cao in the clinkers, rate constant K_r and diffusionactivation en- ergy E_a in the two processes of clinker formationwere cal- culated by using Ginstling-Brounshtein diffusion equationand Arrhenius equation.
文摘In this paper ,how and why MgO acts on the burning of white cement clinker and increases the whiteness were found by means of common detection and EPMA. It was shown that MgO is a kind of effective mineralizer and brightener.
文摘Managers of cement plants are gradually becoming aware of the need for soft sensors in product quality assessment. Cement clinker quality parameters are mostly measured by offline laboratory analysis or by the use of online analyzers. The measurement delay and cost, associated with these methods, are a concern in the cement industry. In this study, a regression-based model was developed to predict the clinker quality parameters as a function of the raw meal quality and the kiln operating variables. This model has mean squared error, coefficient of determination, worst case relative error and variance account for (in external data) given as 8.96 × 10<sup>–7</sup>, 0.9999, 2.17% and above 97%, respectively. Thus, it is concluded that the developed model can provide real time estimates of the clinker quality parameters and capture wider ranges of real plant operating conditions from first principle-based cement rotary kiln models. Also, the model developed can be utilized online as soft sensor since they contain only variables that are easily measured online.
基金Funded by National Basic Research Program of China(No. 2009CB623100)National Eleventh Five-Year Scientific and Technical Support Plans(No.2006BAF02A24)+2 种基金Natural Science Fund for Colleges and Universities in Jiangsu Province(No.08KJB430006)Open Fund for the Key Laboratory of Inorganical and Composite Materials in Jiangsu Province(No. wjjqfhxc1200801)Innovation Fund of Doctoral Dissertation of Nanjing University of Technology(No.BSCX200705)
文摘Optimization of the content of tricalcium silicate（C 3 S）of high cementing clinker was investigated.The content of free-CaO（f-CaO）,mineral composite,the content of C 3 S in the clinker and the hydration product were analyzed by chemical analysis and X-ray diffraction（XRD）.＂K Value＂method of QXRD was selected as a quantitative analysis way to measure the content of C 3 S,and the strength of cement paste was determined.The results show that at a water cement ratio of 0.29,the strength of cement paste with 73%C 3 S can be up to 97.5 MPa at 28 days age.The strength at 28 d of cement with 73%C 3 S is 16%higher than that with 78%C 3 S at water requirement for normal consistency.The relationship between the strength of high cementing Portland cement and the content of C 3 S in the clinker is nonlinear.According to the strength of cement paste,the optimal content of C 3 S in cement clinker is around 73%in this paper.
