The reaction behaviours of A1203 and SiO2 in high alumina coal fly ash under various alkali hydrothermal conditions were studied. The means of XRD, XRF, FTIR and SEM were used to measure the mineral phase and morpholo...The reaction behaviours of A1203 and SiO2 in high alumina coal fly ash under various alkali hydrothermal conditions were studied. The means of XRD, XRF, FTIR and SEM were used to measure the mineral phase and morphology of the solid samples obtained by different alkali hydrothermal treatments as well as the leaching ratio of SiO2 to A1203 in alkali solution. The results showed that with the increase of the hydrothermal treating temperature from 75 to 160 ~C, phillipsite-Na, zeolite A, zeolite P, and hydroxysodalite were produced sequentially while the mullite and corundum phase still remained. Zeolite P was massively formed at low-alkali concentration and the hydroxysodalite was predominantly obtained at high-alkali concentration. By the dissolution of aluminosilicate glass and the formation of zeolites together, the leaching efficiency of SiO2 can reach 42.13% with the mass ratio of A1203/SIO2 up to 2.19：1.展开更多
A novel method was developed for extracting alumina （Al2O3） from fly ash using an ammonium hydrogen sulfate （NH4HSO4） roasting process, and the thermodynamics and kinetics of this method were investigated. The the...A novel method was developed for extracting alumina （Al2O3） from fly ash using an ammonium hydrogen sulfate （NH4HSO4） roasting process, and the thermodynamics and kinetics of this method were investigated. The thermodynamic results were verified experi-mentally. Thermodynamic calculations show that mullite present in the fly ash can react with NH4HSO4 in the 298-723 K range. Process op-timization reveals that the extraction rate can reach up to 90.95% when the fly ash reacts with NH4HSO4 at a 1：8 mole ratio of Al2O3/NH4HSO4 at 673 K for 60 min. Kinetic analysis indicates that the NH4HSO4 roasting process follows the shrinking unreacted core model, and inner diffusion through the product layer is the rate-controlling step. The activation energy is calculated to be 16.627 kJ/mol;and the kinetic equation can be expressed as 1-（2/3）α-（1-α）2/3=0.0374t exp[-16627/（RT）], whereαis the extraction rate and t is the roasting temperature.展开更多
In this paper, an experimental study was conducted in order to test the feasibility of sintering mullite directly from the high-alumina fly ash, without adding any extra material. The results show that the mullite con...In this paper, an experimental study was conducted in order to test the feasibility of sintering mullite directly from the high-alumina fly ash, without adding any extra material. The results show that the mullite contents in most sintered samples are over 70%. The samples sintered from the beneficiated fly ash have a higher content of mullite than those from the as-received fly ash under the same synthetic conditions. To obtain an equal amount of mullite, a higher sintering temperature is needed for the beneficiated fly ash than for the as-received fly ash. Considering the physical properties of sintered mullite, the favorable sintering temperature is 1400℃ for the as-received fly ash and 1500℃ for the beneficiated fly ash. A higher sintering temperature and a shorter holding time are profitable to sintering mullite. The orthogonal test confirmed that the dominant factor affecting mullite synthesis is sintering temperature, and that the most profitable matching conditions are 200 MPa-1500℃-3 h for the as-received fly ash and 200 MPa-1500 ℃-4 h for the beneficiated fly ash.展开更多
A new developed technology for extracting alumina from coal fly ash was studied in this paper. In this technology, coal fly ash is first sintered with ammonium sulfate, forming ammonium aluminum sulfate in the resulta...A new developed technology for extracting alumina from coal fly ash was studied in this paper. In this technology, coal fly ash is first sintered with ammonium sulfate, forming ammonium aluminum sulfate in the resultant product, where alumina can be easily leached without using any strong acid or alkali. The products obtained under different sintering conditions were characterized by X-ray diffractometry. Alumina extraction efficiency of these products was also investigated. The results show that the sintering temperature and time substantially influence the phase composition and alumina extraction efficiency of sintered products, while the heating rate has little influence. The optimal sintering condition is 400 °C for 3 h in air with a heating rate of 6 °C·min-1.Under the optimal sintering condition, the alumina extraction efficiency from as-sintered coal fly ash can reach 85% or more.展开更多
Fly ash was used to prepare alumina and silica white, The 3 stages of the process are as follows: ammonium sulfate calcining, acid leaching and alkali dissolution. The optimum conditions for the experiments to determi...Fly ash was used to prepare alumina and silica white, The 3 stages of the process are as follows: ammonium sulfate calcining, acid leaching and alkali dissolution. The optimum conditions for the experiments to determine are as follows: molar ratio of (NH4)2SO4/Al2O3 is 6, the calcining time is 2h, he H2SO4 concentration is 20%, the leaching temperature is 80℃ and dissolution duration is 2h, the ratio of solution and solid reaction material is 6 for ammonium sulfate calcining and acid leaching stage, reaction time 30min, ratio of liquid to ore 5∶1, alkali concentration 45% and reaction temperature 95 ℃for the alkali dissolution stage. Under these conditions, the total leaching efficiencies of Al2O3 and SiO2 are 78.86% and 95%, respectively. The quality of the main products alumina and silica white can meet the national standards of GB/T24487-2009 and GB10517-89, respectively.展开更多
By desilication treatment,the Al2O3/SiO2 molar ratio of coal fly ash could be improved to the range of 1.63-2.0.The desilicated coal fly ash(DSCFA)was enriched in alumina extraction.A processing technology was develop...By desilication treatment,the Al2O3/SiO2 molar ratio of coal fly ash could be improved to the range of 1.63-2.0.The desilicated coal fly ash(DSCFA)was enriched in alumina extraction.A processing technology was developed for alumina extraction from the DSCFA with the lime sintering process.Ca/(SiO2+TiO2)molar ratio,and NaO/Al2O3 molar ratio,sintering time,and temperature were the most significant parameters impacting on the aluminum extraction efficiency.The optima aluminum extraction efficiency was obtained under conditions of Ca/(SiO2+TiO2)molar ratio of 2.0,NaO/Al2O3 molar ratio of 0.98,and sintering at 1 200 ℃for 60 min.Astandard industrial dissolution method was used under conditions of caustic ratio(αk=n(NaO)/n(Al2O3)of 2.0,Al2O3 concentration of 50 g/L,sodium hydroxide concentration(Nk)of 60.78 g/L,Na2CO3 concentration of 10 g/L,temperature of 85℃, and dissolution duration of 10 min.The final aluminum extraction efficiency was 90%.展开更多
基金Project(2652014017) supported by the Fundamental Research Funds for the Central Universities,China
文摘The reaction behaviours of A1203 and SiO2 in high alumina coal fly ash under various alkali hydrothermal conditions were studied. The means of XRD, XRF, FTIR and SEM were used to measure the mineral phase and morphology of the solid samples obtained by different alkali hydrothermal treatments as well as the leaching ratio of SiO2 to A1203 in alkali solution. The results showed that with the increase of the hydrothermal treating temperature from 75 to 160 ~C, phillipsite-Na, zeolite A, zeolite P, and hydroxysodalite were produced sequentially while the mullite and corundum phase still remained. Zeolite P was massively formed at low-alkali concentration and the hydroxysodalite was predominantly obtained at high-alkali concentration. By the dissolution of aluminosilicate glass and the formation of zeolites together, the leaching efficiency of SiO2 can reach 42.13% with the mass ratio of A1203/SIO2 up to 2.19：1.
基金financially supported by the National Basic Research Priorities Program of China(No.2007CB613603)the China Postdoctoral Science Foundation(No.2013M530934)
文摘A novel method was developed for extracting alumina （Al2O3） from fly ash using an ammonium hydrogen sulfate （NH4HSO4） roasting process, and the thermodynamics and kinetics of this method were investigated. The thermodynamic results were verified experi-mentally. Thermodynamic calculations show that mullite present in the fly ash can react with NH4HSO4 in the 298-723 K range. Process op-timization reveals that the extraction rate can reach up to 90.95% when the fly ash reacts with NH4HSO4 at a 1：8 mole ratio of Al2O3/NH4HSO4 at 673 K for 60 min. Kinetic analysis indicates that the NH4HSO4 roasting process follows the shrinking unreacted core model, and inner diffusion through the product layer is the rate-controlling step. The activation energy is calculated to be 16.627 kJ/mol;and the kinetic equation can be expressed as 1-（2/3）α-（1-α）2/3=0.0374t exp[-16627/（RT）], whereαis the extraction rate and t is the roasting temperature.
基金This work was financed by the National Natural Science Foundation of China （Grant No. 40672103 , 40575065） the Program for New Century Excellent Talents in University of the Chinese Ministry of Education. The authors sincerely thank Professor Li Kaiqi for his constructive suggestions and useful discussions.
文摘In this paper, an experimental study was conducted in order to test the feasibility of sintering mullite directly from the high-alumina fly ash, without adding any extra material. The results show that the mullite contents in most sintered samples are over 70%. The samples sintered from the beneficiated fly ash have a higher content of mullite than those from the as-received fly ash under the same synthetic conditions. To obtain an equal amount of mullite, a higher sintering temperature is needed for the beneficiated fly ash than for the as-received fly ash. Considering the physical properties of sintered mullite, the favorable sintering temperature is 1400℃ for the as-received fly ash and 1500℃ for the beneficiated fly ash. A higher sintering temperature and a shorter holding time are profitable to sintering mullite. The orthogonal test confirmed that the dominant factor affecting mullite synthesis is sintering temperature, and that the most profitable matching conditions are 200 MPa-1500℃-3 h for the as-received fly ash and 200 MPa-1500 ℃-4 h for the beneficiated fly ash.
基金Supported by the Special Project for High-end CNC Machine Tools and Basic Manufacturing Equipment of China(2012ZX04007-021)Liaoning Excellent Talents in University(LR2014004)the National Natural Science Foundation of China(51004071,50804031)
文摘A new developed technology for extracting alumina from coal fly ash was studied in this paper. In this technology, coal fly ash is first sintered with ammonium sulfate, forming ammonium aluminum sulfate in the resultant product, where alumina can be easily leached without using any strong acid or alkali. The products obtained under different sintering conditions were characterized by X-ray diffractometry. Alumina extraction efficiency of these products was also investigated. The results show that the sintering temperature and time substantially influence the phase composition and alumina extraction efficiency of sintered products, while the heating rate has little influence. The optimal sintering condition is 400 °C for 3 h in air with a heating rate of 6 °C·min-1.Under the optimal sintering condition, the alumina extraction efficiency from as-sintered coal fly ash can reach 85% or more.
文摘Fly ash was used to prepare alumina and silica white, The 3 stages of the process are as follows: ammonium sulfate calcining, acid leaching and alkali dissolution. The optimum conditions for the experiments to determine are as follows: molar ratio of (NH4)2SO4/Al2O3 is 6, the calcining time is 2h, he H2SO4 concentration is 20%, the leaching temperature is 80℃ and dissolution duration is 2h, the ratio of solution and solid reaction material is 6 for ammonium sulfate calcining and acid leaching stage, reaction time 30min, ratio of liquid to ore 5∶1, alkali concentration 45% and reaction temperature 95 ℃for the alkali dissolution stage. Under these conditions, the total leaching efficiencies of Al2O3 and SiO2 are 78.86% and 95%, respectively. The quality of the main products alumina and silica white can meet the national standards of GB/T24487-2009 and GB10517-89, respectively.
基金Project(YFZX(0804))supported by Science Foundation of the Pingshuo Coal Industry Company,China
文摘By desilication treatment,the Al2O3/SiO2 molar ratio of coal fly ash could be improved to the range of 1.63-2.0.The desilicated coal fly ash(DSCFA)was enriched in alumina extraction.A processing technology was developed for alumina extraction from the DSCFA with the lime sintering process.Ca/(SiO2+TiO2)molar ratio,and NaO/Al2O3 molar ratio,sintering time,and temperature were the most significant parameters impacting on the aluminum extraction efficiency.The optima aluminum extraction efficiency was obtained under conditions of Ca/(SiO2+TiO2)molar ratio of 2.0,NaO/Al2O3 molar ratio of 0.98,and sintering at 1 200 ℃for 60 min.Astandard industrial dissolution method was used under conditions of caustic ratio(αk=n(NaO)/n(Al2O3)of 2.0,Al2O3 concentration of 50 g/L,sodium hydroxide concentration(Nk)of 60.78 g/L,Na2CO3 concentration of 10 g/L,temperature of 85℃, and dissolution duration of 10 min.The final aluminum extraction efficiency was 90%.
