High alumina fly ash(FAHAl)is a kind of bulk solid waste unique to China,whose availability of high-value aluminum and the threat to the environment makes its high-value utilization urgent.In this work,the alumina con...High alumina fly ash(FAHAl)is a kind of bulk solid waste unique to China,whose availability of high-value aluminum and the threat to the environment makes its high-value utilization urgent.In this work,the alumina containing leaching solution obtained from Na_(2)CO_(3) roasting and HCl leaching of FAHAl was used as the mother liquor to prepare layered boehmite in situ.The preparation process with AlCl_(3) as the raw material was also compared.The formation process and mechanism of boehmite,the choice of solvent,along with the adsorption capability of Congo red were analyzed by X-ray diffraction,scanning electron microscopy,Fourier transform infrared spectroscopy,Brunauer-Emmett-Teller method and adsorption experiments.Results showed that during the preparation of layered boehmite,the precursor Al(OH)_(3) from the reaction of Al^(3+) and OH-is transformed into boehmiteγ-AlOOH.The existence of ethanol is beneficial to regulate and promote the growth of boehmite crystal effectively.When water and ethanol are mixed with a volume ratio of 2:1 and used as the solvent,the maximum specific surface area of the boehmite is obtained at 135.7 m^(2)·g^(-1),and 99.16%of Congo red can be absorbed after 10 min when AlCl3 is used as a raw material.As purified leaching solution is used as the mother liquid,the crystallinity of boehmite decreases slightly when the pH value decreases from 12.5 to 11.When pH is 11,the removal efficiency of Congo red reaches a maximum of 72.25%.This process not only achieves the extraction of aluminum and high-value utilization of FAHAl but also provides a thought to prepare layered boehmite with adsorption properties.展开更多
The precipitation of spherical boehmite was studied by surface energy calculations, measurements of precipitation ratios, Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, and t...The precipitation of spherical boehmite was studied by surface energy calculations, measurements of precipitation ratios, Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The surface energy calculation results show that the(001) and(112) planes of gibbsite surfaces are remarkably stable because of their low surface energies. In addition, the(010) plane of boehmite grows preferentially during precipitation because of its low surface energy. Thus, we propose a method to precipitate spherical boehmite from a supersaturated sodium aluminate solution by adding gibbsite as seed in a heterogeneous system. In this method, gibbsite acts as the preliminary seed and saturation modifier. The results show that the fine boehmite first nucleates on the(001) and(112) planes of gibbsite and then grows vertically on the(001) and(112) basal planes of gibbsite via self-assembly, thereby forming spherical boehmite. Simultaneously, gibbsite is dissolved into the aluminate solution to maintain the saturation for the precipitation of boehmite. The precipitation ratio fluctuates(forming an M-shaped curve) because of gibbsite dissolution and boehmite precipitation. The mechanism of boehmite precipitation was further discussed on the basis of the differences in surface energy and solubility between gibbsite and boehmite. This study provides an environmentally friendly and economical method to prepare specific boehmite in a heterogeneous system.展开更多
Boehmites(Al2O3·xH2O)were hydrothermally prepared from aluminum alkoxide.The effect of temperature on preparation was studied in the range of 100-180℃.The XRD analysis shows that with temperature increasing,the ...Boehmites(Al2O3·xH2O)were hydrothermally prepared from aluminum alkoxide.The effect of temperature on preparation was studied in the range of 100-180℃.The XRD analysis shows that with temperature increasing,the transformation of pseudo-boehmite into well-crystallized boehmite takes place.The micro-morphologies change also from irregular clew to thin cubic platelets.From the mass loss of the samples prepared at different temperatures,the value of x is estimated to vary between 1.06 and 1.67.γ-Al2O3 obtained by subsequent calcination of boehmite at 600℃is also characterized by XRD and its morphology remains unchanged.展开更多
The sub-micron sized YAG ： Ce phosphors were synthesized via a modified sol-gel method by peptizing nano-pesudoboehmite particulate. It is found that YAG phase from the dried gel powders appears at 1000 ℃ then the p...The sub-micron sized YAG ： Ce phosphors were synthesized via a modified sol-gel method by peptizing nano-pesudoboehmite particulate. It is found that YAG phase from the dried gel powders appears at 1000 ℃ then the pure YAG phase exists at a relatively lower sintering temperature of 1400 ℃. The smaller sizes of phosphors in the ranges of 1 - 3 μm are obtained due to the contribution of seeding effects of nano-sized alumina particles to strengthen each step of the processes. Both the excitation and emission spectra of photoluminescence of the phosphor obtained at 1400 ℃ meet well with the spectroscopic requirements of the WLED phosphors.展开更多
A series of pseudo-boehmite samples with their sulfate radicals(SO2-4) concentration ranging from 0.9% to 3.0% were prepared by the reaction of Na Al O2 solution on Al2(SO4)3 solution. The existing form of sulfate rad...A series of pseudo-boehmite samples with their sulfate radicals(SO2-4) concentration ranging from 0.9% to 3.0% were prepared by the reaction of Na Al O2 solution on Al2(SO4)3 solution. The existing form of sulfate radicals was investigated. Results have shown that sulfates in pseudo-boehmite included two parts, the soluble sulfate radicals and the insoluble sulfate radicals, which accounted for 99% of the total amount of sulfate radicals. XRD, low-temperature N2-adsorption, and TEM were used to characterize the properties of these pseudo-boehmite samples. Results have shown that the relative crystallinity and crystal size of pseudo-boehmite decreased with the increase of sulfate radicals in the support. In the meanwhile, the bound water content in pseudo-boehmite increased. The TEM images of pseudo-boehmite indicated that the pseudoboehmite was prone to become amorphous hydrated alumina. However, the effect of sulfate content on the specific surface area and pore structure of aluminium oxide was insignificant.展开更多
Hydrogen peroxide(H2O2)precipitation from sodium aluminate(SA)solution at close-ambient temperature is an efficient method to synthesize boehmite and its derived alumina with high surface area,but the precipitation yi...Hydrogen peroxide(H2O2)precipitation from sodium aluminate(SA)solution at close-ambient temperature is an efficient method to synthesize boehmite and its derived alumina with high surface area,but the precipitation yield of Al2O3 is usually below 50%in highly alkaline SA solutions.Here the synthesis of boehmite is enhanced through a precarbonization-assisted H2O2 route in highly alkaline SA solutions.It is found that the crystal structure of the precipitation product is evidently influenced by the precipitation conditions.As the precipitation temperature increases from 273 to 325 K,a small amount of gibbsite by-product is formed.As the aging temperature increases from 301 to 333 K,the crystallinity of boehmite decreases and part of the boehmite dissolves due to an increase in the pH value.Based on the above results,a precarbonization-assisted H2O2 route is proposed to obtain pure boehmite with more complete recovery of Al2O3 from highly alkaline SA solutions.The route includes a controllable precarbonization step of SA solutions with a molar ratio of Na2O to Al2O3 higher than 2:1,followed by the H2O2-precipitated step with a molar ratio of H2O2 to Al2O3 less than 7:1.Because of its facile operation conditions,no extraneous impurity,time saving and a possible recycle of the filtrate,the route has great potential to be an alternative method for preparation of boehmite and its derived alumina.展开更多
Colloidal boehmite particles have been included into a polyethylene terephthalate matrix by in situ polymerization. Boehmite nanoparticles were produced by the controlled hydrolysis of aluminium isopropylate. The nano...Colloidal boehmite particles have been included into a polyethylene terephthalate matrix by in situ polymerization. Boehmite nanoparticles were produced by the controlled hydrolysis of aluminium isopropylate. The nanoparticles were characterized using Transmitted Electronic Microscopy (TEM) and X-ray Diffraction (XRD), which revealed the particles of magnitude about 10 nm. The particles have been used without any surface modification. Characterization of the nanocomposite has been carried out using TEM and differential scanning calorimetry (DSC). TEM images indicate that the particles have been homogeneously dispersed in the polymer. DSC results show that the presence of boehmite affects the process of crystallization of polyethylene terephthalate.展开更多
Pseudo-boehmite (PB) and γ-Al2O3 support are prepared by neutralization ofNaAlO2 solution with CO2(mixed gases) on bench scale. PB, typically loosely packed, fibrous particle/aggregate, is obtained by adjustingconcen...Pseudo-boehmite (PB) and γ-Al2O3 support are prepared by neutralization ofNaAlO2 solution with CO2(mixed gases) on bench scale. PB, typically loosely packed, fibrous particle/aggregate, is obtained by adjustingconcentration and flow rate of CO2 and concentration of NaAlO2 solution at a pH level lower than that commonlyassumed during neutralization. After calcination at different temperatures, γ-Al2O3 supports with different pore vol-ume and different pore size are prepared at different conditions.展开更多
Boehmite nanorods were synthesized by a solvothermal method using AICl3·6H2O in mixed solvents of water and aniline. The solvothermal time, heating temperature and the concentration of aniline have effects on the...Boehmite nanorods were synthesized by a solvothermal method using AICl3·6H2O in mixed solvents of water and aniline. The solvothermal time, heating temperature and the concentration of aniline have effects on the morphology of boehmite. γ-alumina nanorods were prepared by a simple thermal transformation of boehmite nanorods. A rational mechanism based on the oriented attachment is proposed for the formation of boehmite nanorods. The products were characterized by X-ray powder diffraction （XRD） and transmission electron microscopy （TEM）. Photoluminescence （PL） spectrum of the boehmite nanorods was also investigated.展开更多
Boehmite was prepared under heat treatment in water vapour, and the phase transformation of gibbsite heat-treated at various temperatures was investigated. The sample was characterized by scanning electron microscopy(...Boehmite was prepared under heat treatment in water vapour, and the phase transformation of gibbsite heat-treated at various temperatures was investigated. The sample was characterized by scanning electron microscopy(SEM), X-ray diffraction (XRD), thermogravimetry and differential thermalanalysis (TG-DTA), fourier transform infrared (FTIR),and BET surface area.Effect of temperature on preparation was studied in the range of 155°–195°.With the increase in temperature, transformation of gibbsite into crystalline boehmites took place as indicated by the X-ray diffraction (XRD). The shape of the grains in the prepared sample was cube-like morphology.In water vapour gibbsite transform into boehmite by a dissolution - precipitation mechanism.展开更多
Gibbsite is the usual precipitation product from alumina refineries with either Bayer or sintering process.However,the advantage of boehmite precipitation over gibbsite precipitation is the significant energy saving i...Gibbsite is the usual precipitation product from alumina refineries with either Bayer or sintering process.However,the advantage of boehmite precipitation over gibbsite precipitation is the significant energy saving in the subsequent calcination step.The current investigation takes a pragmatic approach to measure precipitation ratios,determine product phase,morphology and particle size distribution,and assess the impacts and adjustment capability of main parameters such as seed,temperature,ethanol medium,and supersaturation on the precipitation kinetics and alumina hydrate type during co-precipitation process.The results clarify that gibbsite and boehmite both can be precipitated from supersaturated sodium aluminate solutions simultaneously,and the competitive formation between Al(OH)3 and γ-AlOOH determines the main precipitate phases from pregnant liquor.Boehmite seeds,high temperature and ethanol addition can promote the boehmite precipitation and improve the mass fraction of boehmite in products.Co-precipitation changes the multimodal distribution of seeds to a normal and well distribution of products,and the particle size is more than several times that of seeds.展开更多
Boehmite powders with various particle sizes have been prepared by hydrothermal method and the α-Al2O3 powders yielded after subsequent calcination have been studied. Dispersive crystalline boehmite powders of 30-100...Boehmite powders with various particle sizes have been prepared by hydrothermal method and the α-Al2O3 powders yielded after subsequent calcination have been studied. Dispersive crystalline boehmite powders of 30-100 nm, 0.4-0.6μm and 1μm in size were obtained respectively by changing the hydrothermal precursors and the pH value of hydrothermal slurry. Calcination of boehmite powders of 30-100 nm at 1250℃ for 1h resulted in the formation of single-phase α-Al2O3 , and the products consisted of vermicular particles. The boehmite powders of 0.4-0.6μm were also fully converted to α-Al2O3 at 1250℃, and the products consisted of plate-like particles with the same size of 0.4-0.6μm. The boehmite powders of 1μm calcined at 1350℃ for 2h were still composed of a little proportions of transition aluminas besides α-Al2O3, and the particles sintered severely. The reaction processes for the formation of crystalline boehmites under hydrothermal conditions and α-Al2O3 powders during calcination have been discussed.展开更多
The efficiency and irreversibility defined based on the second law of thermodynamics provide a new path for heat exchangers design and make performance analysis more straightforward and elegant.The second law of therm...The efficiency and irreversibility defined based on the second law of thermodynamics provide a new path for heat exchangers design and make performance analysis more straightforward and elegant.The second law of thermodynamics is applied in a Straight Microchannel Printed Circuit heat exchanger to determine the thermal performance of different shapes of Boehmite Alumina compared to Al2O3 aluminum oxide.The various forms of non-spherical Boehmite Alumina are characterized dynamically and thermodynamically through dynamic viscosity and thermal conductivity,using empirical coefficients.The non-spherical shape includes platelet,cylindrical,blades,and bricks forms.Graphical results are presented for thermal efficiency,thermal irreversibility,heat transfer rate,and nanofluid exit temperature.The non-spherical shapes of Boehmite Alumina show different thermal characteristics concerning the spherical shape when there are variations in fluid flow rates and the nanoparticles fraction.Furthermore,it was theoretically demonstrated that non-spherical particles have higher heat transfer rates than spherical particles,emphasizing platelets and cylindrical shapes for the low volume fraction of nanoparticles and bricks and blades for high volume fraction.展开更多
基金supported by the National Natural Science Foundation of China(52174277,52204309 and 52374300).
文摘High alumina fly ash(FAHAl)is a kind of bulk solid waste unique to China,whose availability of high-value aluminum and the threat to the environment makes its high-value utilization urgent.In this work,the alumina containing leaching solution obtained from Na_(2)CO_(3) roasting and HCl leaching of FAHAl was used as the mother liquor to prepare layered boehmite in situ.The preparation process with AlCl_(3) as the raw material was also compared.The formation process and mechanism of boehmite,the choice of solvent,along with the adsorption capability of Congo red were analyzed by X-ray diffraction,scanning electron microscopy,Fourier transform infrared spectroscopy,Brunauer-Emmett-Teller method and adsorption experiments.Results showed that during the preparation of layered boehmite,the precursor Al(OH)_(3) from the reaction of Al^(3+) and OH-is transformed into boehmiteγ-AlOOH.The existence of ethanol is beneficial to regulate and promote the growth of boehmite crystal effectively.When water and ethanol are mixed with a volume ratio of 2:1 and used as the solvent,the maximum specific surface area of the boehmite is obtained at 135.7 m^(2)·g^(-1),and 99.16%of Congo red can be absorbed after 10 min when AlCl3 is used as a raw material.As purified leaching solution is used as the mother liquid,the crystallinity of boehmite decreases slightly when the pH value decreases from 12.5 to 11.When pH is 11,the removal efficiency of Congo red reaches a maximum of 72.25%.This process not only achieves the extraction of aluminum and high-value utilization of FAHAl but also provides a thought to prepare layered boehmite with adsorption properties.
基金financially supported by the National Natural Science Foundation of China (No.51274242)the Fundamental Research Funds for the Central Universities of Central South University (No.2016zzts038)
文摘The precipitation of spherical boehmite was studied by surface energy calculations, measurements of precipitation ratios, Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The surface energy calculation results show that the(001) and(112) planes of gibbsite surfaces are remarkably stable because of their low surface energies. In addition, the(010) plane of boehmite grows preferentially during precipitation because of its low surface energy. Thus, we propose a method to precipitate spherical boehmite from a supersaturated sodium aluminate solution by adding gibbsite as seed in a heterogeneous system. In this method, gibbsite acts as the preliminary seed and saturation modifier. The results show that the fine boehmite first nucleates on the(001) and(112) planes of gibbsite and then grows vertically on the(001) and(112) basal planes of gibbsite via self-assembly, thereby forming spherical boehmite. Simultaneously, gibbsite is dissolved into the aluminate solution to maintain the saturation for the precipitation of boehmite. The precipitation ratio fluctuates(forming an M-shaped curve) because of gibbsite dissolution and boehmite precipitation. The mechanism of boehmite precipitation was further discussed on the basis of the differences in surface energy and solubility between gibbsite and boehmite. This study provides an environmentally friendly and economical method to prepare specific boehmite in a heterogeneous system.
基金Project(50974026)supported by the National Natural Science Foundation of China
文摘Boehmites(Al2O3·xH2O)were hydrothermally prepared from aluminum alkoxide.The effect of temperature on preparation was studied in the range of 100-180℃.The XRD analysis shows that with temperature increasing,the transformation of pseudo-boehmite into well-crystallized boehmite takes place.The micro-morphologies change also from irregular clew to thin cubic platelets.From the mass loss of the samples prepared at different temperatures,the value of x is estimated to vary between 1.06 and 1.67.γ-Al2O3 obtained by subsequent calcination of boehmite at 600℃is also characterized by XRD and its morphology remains unchanged.
文摘The sub-micron sized YAG ： Ce phosphors were synthesized via a modified sol-gel method by peptizing nano-pesudoboehmite particulate. It is found that YAG phase from the dried gel powders appears at 1000 ℃ then the pure YAG phase exists at a relatively lower sintering temperature of 1400 ℃. The smaller sizes of phosphors in the ranges of 1 - 3 μm are obtained due to the contribution of seeding effects of nano-sized alumina particles to strengthen each step of the processes. Both the excitation and emission spectra of photoluminescence of the phosphor obtained at 1400 ℃ meet well with the spectroscopic requirements of the WLED phosphors.
基金financially supported by the SINOPEC(Contact No.111010)
文摘A series of pseudo-boehmite samples with their sulfate radicals(SO2-4) concentration ranging from 0.9% to 3.0% were prepared by the reaction of Na Al O2 solution on Al2(SO4)3 solution. The existing form of sulfate radicals was investigated. Results have shown that sulfates in pseudo-boehmite included two parts, the soluble sulfate radicals and the insoluble sulfate radicals, which accounted for 99% of the total amount of sulfate radicals. XRD, low-temperature N2-adsorption, and TEM were used to characterize the properties of these pseudo-boehmite samples. Results have shown that the relative crystallinity and crystal size of pseudo-boehmite decreased with the increase of sulfate radicals in the support. In the meanwhile, the bound water content in pseudo-boehmite increased. The TEM images of pseudo-boehmite indicated that the pseudoboehmite was prone to become amorphous hydrated alumina. However, the effect of sulfate content on the specific surface area and pore structure of aluminium oxide was insignificant.
基金Supported by the China Postdoctoral Science Foundation （20080440142）. ACKNOWLEDGEMENTS We thank Dr. Stacy M. Morris, Kent State University, for her reviews and improvement of the manuscript.
文摘Hydrogen peroxide(H2O2)precipitation from sodium aluminate(SA)solution at close-ambient temperature is an efficient method to synthesize boehmite and its derived alumina with high surface area,but the precipitation yield of Al2O3 is usually below 50%in highly alkaline SA solutions.Here the synthesis of boehmite is enhanced through a precarbonization-assisted H2O2 route in highly alkaline SA solutions.It is found that the crystal structure of the precipitation product is evidently influenced by the precipitation conditions.As the precipitation temperature increases from 273 to 325 K,a small amount of gibbsite by-product is formed.As the aging temperature increases from 301 to 333 K,the crystallinity of boehmite decreases and part of the boehmite dissolves due to an increase in the pH value.Based on the above results,a precarbonization-assisted H2O2 route is proposed to obtain pure boehmite with more complete recovery of Al2O3 from highly alkaline SA solutions.The route includes a controllable precarbonization step of SA solutions with a molar ratio of Na2O to Al2O3 higher than 2:1,followed by the H2O2-precipitated step with a molar ratio of H2O2 to Al2O3 less than 7:1.Because of its facile operation conditions,no extraneous impurity,time saving and a possible recycle of the filtrate,the route has great potential to be an alternative method for preparation of boehmite and its derived alumina.
基金Supported by Ningbo Natural Science Foundation (No.2006A610067)
文摘Colloidal boehmite particles have been included into a polyethylene terephthalate matrix by in situ polymerization. Boehmite nanoparticles were produced by the controlled hydrolysis of aluminium isopropylate. The nanoparticles were characterized using Transmitted Electronic Microscopy (TEM) and X-ray Diffraction (XRD), which revealed the particles of magnitude about 10 nm. The particles have been used without any surface modification. Characterization of the nanocomposite has been carried out using TEM and differential scanning calorimetry (DSC). TEM images indicate that the particles have been homogeneously dispersed in the polymer. DSC results show that the presence of boehmite affects the process of crystallization of polyethylene terephthalate.
文摘Pseudo-boehmite (PB) and γ-Al2O3 support are prepared by neutralization ofNaAlO2 solution with CO2(mixed gases) on bench scale. PB, typically loosely packed, fibrous particle/aggregate, is obtained by adjustingconcentration and flow rate of CO2 and concentration of NaAlO2 solution at a pH level lower than that commonlyassumed during neutralization. After calcination at different temperatures, γ-Al2O3 supports with different pore vol-ume and different pore size are prepared at different conditions.
基金the National Natural Science Foundation of China(50772124,50472014)the Program of Shanghai Subject Chief Scientist(07XD14031)the Key Project for Innovative Research and Director Fund of Biomaterials Research Center from Shanghai Institute of Ceramics
文摘Boehmite nanorods were synthesized by a solvothermal method using AICl3·6H2O in mixed solvents of water and aniline. The solvothermal time, heating temperature and the concentration of aniline have effects on the morphology of boehmite. γ-alumina nanorods were prepared by a simple thermal transformation of boehmite nanorods. A rational mechanism based on the oriented attachment is proposed for the formation of boehmite nanorods. The products were characterized by X-ray powder diffraction （XRD） and transmission electron microscopy （TEM）. Photoluminescence （PL） spectrum of the boehmite nanorods was also investigated.
文摘Boehmite was prepared under heat treatment in water vapour, and the phase transformation of gibbsite heat-treated at various temperatures was investigated. The sample was characterized by scanning electron microscopy(SEM), X-ray diffraction (XRD), thermogravimetry and differential thermalanalysis (TG-DTA), fourier transform infrared (FTIR),and BET surface area.Effect of temperature on preparation was studied in the range of 155°–195°.With the increase in temperature, transformation of gibbsite into crystalline boehmites took place as indicated by the X-ray diffraction (XRD). The shape of the grains in the prepared sample was cube-like morphology.In water vapour gibbsite transform into boehmite by a dissolution - precipitation mechanism.
基金Projects(50704030) supported by the National Natural Science Foundation of ChinaProject(KGCX2-YW-321-2) supported by the Knowledge Innovation Program of the Chinese Academy of Sciences
文摘Gibbsite is the usual precipitation product from alumina refineries with either Bayer or sintering process.However,the advantage of boehmite precipitation over gibbsite precipitation is the significant energy saving in the subsequent calcination step.The current investigation takes a pragmatic approach to measure precipitation ratios,determine product phase,morphology and particle size distribution,and assess the impacts and adjustment capability of main parameters such as seed,temperature,ethanol medium,and supersaturation on the precipitation kinetics and alumina hydrate type during co-precipitation process.The results clarify that gibbsite and boehmite both can be precipitated from supersaturated sodium aluminate solutions simultaneously,and the competitive formation between Al(OH)3 and γ-AlOOH determines the main precipitate phases from pregnant liquor.Boehmite seeds,high temperature and ethanol addition can promote the boehmite precipitation and improve the mass fraction of boehmite in products.Co-precipitation changes the multimodal distribution of seeds to a normal and well distribution of products,and the particle size is more than several times that of seeds.
文摘Boehmite powders with various particle sizes have been prepared by hydrothermal method and the α-Al2O3 powders yielded after subsequent calcination have been studied. Dispersive crystalline boehmite powders of 30-100 nm, 0.4-0.6μm and 1μm in size were obtained respectively by changing the hydrothermal precursors and the pH value of hydrothermal slurry. Calcination of boehmite powders of 30-100 nm at 1250℃ for 1h resulted in the formation of single-phase α-Al2O3 , and the products consisted of vermicular particles. The boehmite powders of 0.4-0.6μm were also fully converted to α-Al2O3 at 1250℃, and the products consisted of plate-like particles with the same size of 0.4-0.6μm. The boehmite powders of 1μm calcined at 1350℃ for 2h were still composed of a little proportions of transition aluminas besides α-Al2O3, and the particles sintered severely. The reaction processes for the formation of crystalline boehmites under hydrothermal conditions and α-Al2O3 powders during calcination have been discussed.
文摘The efficiency and irreversibility defined based on the second law of thermodynamics provide a new path for heat exchangers design and make performance analysis more straightforward and elegant.The second law of thermodynamics is applied in a Straight Microchannel Printed Circuit heat exchanger to determine the thermal performance of different shapes of Boehmite Alumina compared to Al2O3 aluminum oxide.The various forms of non-spherical Boehmite Alumina are characterized dynamically and thermodynamically through dynamic viscosity and thermal conductivity,using empirical coefficients.The non-spherical shape includes platelet,cylindrical,blades,and bricks forms.Graphical results are presented for thermal efficiency,thermal irreversibility,heat transfer rate,and nanofluid exit temperature.The non-spherical shapes of Boehmite Alumina show different thermal characteristics concerning the spherical shape when there are variations in fluid flow rates and the nanoparticles fraction.Furthermore,it was theoretically demonstrated that non-spherical particles have higher heat transfer rates than spherical particles,emphasizing platelets and cylindrical shapes for the low volume fraction of nanoparticles and bricks and blades for high volume fraction.
