The Experts below are selected from a list of 285 Experts worldwide ranked by ideXlab platform
Gabrie M.h. Meesters - One of the best experts on this subject based on the ideXlab platform.
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Characterization and modeling of a sub-micron milling process limited by agglomeration phenomena
Chemical Engineering Science, 2012Co-Authors: Stephen L. A. Hennart, M.c. Domingues, W.j. Wildeboer, P. Van Hee, V. Drouet, Gabrie M.h. MeestersAbstract:Abstract The objective of this work was to characterize a sub-micron Grinding process in a wet ball mill including the agglomeration of fines inside the Grinding chamber. To do so a population balance model has been developed. A Dynomill ball mill was used and the Grinding Medium consisted of zirconium oxide beads. The product under investigation was poorly water-soluble. The particle size distribution of the initial powder ranged from 1 to 100 um. Laser diffraction was used to analyze the particle size distribution. During Grinding the average particle diameter of a particulate product is reduced to a minimum value. These Grinding experiments showed that for a specific product this minimum value is a fixed constant within the range of tested operating conditions. This minimum average particle diameter could be influenced by modification of the particle surface properties with surface active agents. The minimum mass mean particle diameter is a result of Grinding and simultaneous agglomeration of broken particles. To build a representative model, a dynamic population balance model was developed. The crystallite size as measured with X-Ray diffraction was chosen as the minimum achievable particle size by Grinding. Simulations showed that the applied population balance model is an adequate tool to forecast the evolution of the particle size reduction process and the time required to reach the final product specifications. The product could be defined as “very brittle” using the approach from Kwade et al. (1996b) and Stadler et al. (1990) . The shear induced by the translation movements of the Grinding Medium beads was thus enough to break the particles. The median particle size of the broken particles ( x 50 ) was plotted as function of the number of stress events (SN) in the mill. This number of stress events was calculated for one initial product particle. That is the representative number of stresses that needs to be applied on an initial particle to break it into fractions with the desired fine particle size. SN is proportional to the number of media contacts and their frequency, and the probability that a media contact leads to particle breakage. That frequency of media contact is defined as the angular rotation speed ( ω ) of the mill corrected by an efficiency factor ( γ F ). The stress number SN is characteristic of the ground product. The efficiency factor γ F describes the efficiency with which the impellor transfers its energy to the Grinding Medium. γ F was a function of the mill design and more specifically the impellor shape. Factor γ F is taken as the surface of the impellor in contact with the Grinding media. This approach leads to a general representation of the Grinding profile of the studied product in a stirred media mill.
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Study of the process of stirred ball milling of poorly water soluble organic products using factorial design
Powder Technology, 2010Co-Authors: Stephen L. A. Hennart, M.c. Domingues, W.j. Wildeboer, P. Van Hee, Gabrie M.h. MeestersAbstract:Abstract The objective of this work was to investigate the mechanism of very fine Grinding in a wet ball mill as a function of process parameters, i.e. rotation speed of the mill and Grinding Medium bead size. The ball mill used was a Dynomill and the Grinding Medium consisted of zirconium oxide beads. The product is a poorly water-soluble organic compound. Laser diffraction was used to analyze the particle size distribution. During Grinding the average particle diameter of the product was reduced to a minimum size, which was constant within the range of tested operating conditions. The Grinding parameters were studied to control the Grinding process with respect to the required Grinding time for reaching the minimum particle size and wear of the set-up. The Grinding time was strongly dependent on the Grinding Medium bead size and on the rotation speed. The Grinding process became faster when the rotation speed increased and the Grinding Medium bead size decreased. The wear of the set-up, and therefore the contamination of the final product with heavy metals, strongly increased with the rotation speed. A similar trend was observed with an increase of Grinding Medium bead size. The degradation rate of the product was not significant in the range of Grinding parameters studied.
Jian Zhou - One of the best experts on this subject based on the ideXlab platform.
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Effect of Y2O3 additives on the wet abrasion resistance of an alumina-based Grinding Medium
Wear, 2016Co-Authors: Jian Zhou, Yuan XiongAbstract:Abstract The purpose of this work was to improve the wear resistance of an alumina ceramic Grinding Medium used in water-based ball milling procedures. High alumina ceramics (>97 wt% Al 2 O 3 ) composed of Al 2 O 3 –CaCO 3 –SiO 2 –MgO–Y 2 O 3 and designated as ACSMY have been investigated. The content of Y 2 O 3 was varied from 0.0 to 1.6 wt%. Tests were performed in a ball milling apparatus in a water environment, and according to a Chinese standard test method. The compositions and microstructure of four compositions, as well as the effects of sintering temperature on wear rate are discussed. It is found that Y 2 O 3 can refine grain size, enhance density, improve bonding strength of grain boundaries, and promote the crystallization of the CaAl 12 O 19 phase. In addition, Y 3 Al 5 O 12 and alkaline earth metal ions (Ca 2+ or Mg 2+ ) can form solid solutions to purify the grain boundaries. The role of Y 2 O 3 is discussed in detail, and the mechanisms responsible for wear resistance of ACSMY ceramics are revealed.
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Effect of rare-earth Lu2O3 on the wear resistance of alumina ceramics for Grinding media
Powder Technology, 2016Co-Authors: Jian Zhou, Junchang LiuAbstract:Abstract Wear resistance of Grinding media is crucial for the quality of powders. The purpose of this work is to improve the wear resistance of Grinding Medium in an Al 2 O 3 -CaCO 3 -SiO 2 -MgO-Lu 2 O 3 (ACSML) system. The effect of Lu 2 O 3 content on bulk density and wear rate is discussed. The phase composition and microstructure of this material are analyzed. The results show that adding a trace amount of Lu 2 O 3 to alumina can evidently improve wear resistance by grain refinement and enhancing density. The wear rate of Grinding Medium is as low as 0.00044‰, and the wear resistance has been improved by 31% than the sample without Lu 2 O 3 . However, excessive Lu 2 O 3 can lead to deterioration of wear resistance, which due to grain growth and existence of Al 5 Lu 3 O 12 .
Junchang Liu - One of the best experts on this subject based on the ideXlab platform.
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Effect of rare-earth Lu2O3 on the wear resistance of alumina ceramics for Grinding media
Powder Technology, 2016Co-Authors: Jian Zhou, Junchang LiuAbstract:Abstract Wear resistance of Grinding media is crucial for the quality of powders. The purpose of this work is to improve the wear resistance of Grinding Medium in an Al 2 O 3 -CaCO 3 -SiO 2 -MgO-Lu 2 O 3 (ACSML) system. The effect of Lu 2 O 3 content on bulk density and wear rate is discussed. The phase composition and microstructure of this material are analyzed. The results show that adding a trace amount of Lu 2 O 3 to alumina can evidently improve wear resistance by grain refinement and enhancing density. The wear rate of Grinding Medium is as low as 0.00044‰, and the wear resistance has been improved by 31% than the sample without Lu 2 O 3 . However, excessive Lu 2 O 3 can lead to deterioration of wear resistance, which due to grain growth and existence of Al 5 Lu 3 O 12 .
Stephen L. A. Hennart - One of the best experts on this subject based on the ideXlab platform.
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Characterization and modeling of a sub-micron milling process limited by agglomeration phenomena
Chemical Engineering Science, 2012Co-Authors: Stephen L. A. Hennart, M.c. Domingues, W.j. Wildeboer, P. Van Hee, V. Drouet, Gabrie M.h. MeestersAbstract:Abstract The objective of this work was to characterize a sub-micron Grinding process in a wet ball mill including the agglomeration of fines inside the Grinding chamber. To do so a population balance model has been developed. A Dynomill ball mill was used and the Grinding Medium consisted of zirconium oxide beads. The product under investigation was poorly water-soluble. The particle size distribution of the initial powder ranged from 1 to 100 um. Laser diffraction was used to analyze the particle size distribution. During Grinding the average particle diameter of a particulate product is reduced to a minimum value. These Grinding experiments showed that for a specific product this minimum value is a fixed constant within the range of tested operating conditions. This minimum average particle diameter could be influenced by modification of the particle surface properties with surface active agents. The minimum mass mean particle diameter is a result of Grinding and simultaneous agglomeration of broken particles. To build a representative model, a dynamic population balance model was developed. The crystallite size as measured with X-Ray diffraction was chosen as the minimum achievable particle size by Grinding. Simulations showed that the applied population balance model is an adequate tool to forecast the evolution of the particle size reduction process and the time required to reach the final product specifications. The product could be defined as “very brittle” using the approach from Kwade et al. (1996b) and Stadler et al. (1990) . The shear induced by the translation movements of the Grinding Medium beads was thus enough to break the particles. The median particle size of the broken particles ( x 50 ) was plotted as function of the number of stress events (SN) in the mill. This number of stress events was calculated for one initial product particle. That is the representative number of stresses that needs to be applied on an initial particle to break it into fractions with the desired fine particle size. SN is proportional to the number of media contacts and their frequency, and the probability that a media contact leads to particle breakage. That frequency of media contact is defined as the angular rotation speed ( ω ) of the mill corrected by an efficiency factor ( γ F ). The stress number SN is characteristic of the ground product. The efficiency factor γ F describes the efficiency with which the impellor transfers its energy to the Grinding Medium. γ F was a function of the mill design and more specifically the impellor shape. Factor γ F is taken as the surface of the impellor in contact with the Grinding media. This approach leads to a general representation of the Grinding profile of the studied product in a stirred media mill.
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Study of the process of stirred ball milling of poorly water soluble organic products using factorial design
Powder Technology, 2010Co-Authors: Stephen L. A. Hennart, M.c. Domingues, W.j. Wildeboer, P. Van Hee, Gabrie M.h. MeestersAbstract:Abstract The objective of this work was to investigate the mechanism of very fine Grinding in a wet ball mill as a function of process parameters, i.e. rotation speed of the mill and Grinding Medium bead size. The ball mill used was a Dynomill and the Grinding Medium consisted of zirconium oxide beads. The product is a poorly water-soluble organic compound. Laser diffraction was used to analyze the particle size distribution. During Grinding the average particle diameter of the product was reduced to a minimum size, which was constant within the range of tested operating conditions. The Grinding parameters were studied to control the Grinding process with respect to the required Grinding time for reaching the minimum particle size and wear of the set-up. The Grinding time was strongly dependent on the Grinding Medium bead size and on the rotation speed. The Grinding process became faster when the rotation speed increased and the Grinding Medium bead size decreased. The wear of the set-up, and therefore the contamination of the final product with heavy metals, strongly increased with the rotation speed. A similar trend was observed with an increase of Grinding Medium bead size. The degradation rate of the product was not significant in the range of Grinding parameters studied.
Jouko Niinimäki - One of the best experts on this subject based on the ideXlab platform.
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Ultrafine Grinding of Limestone with Sodium Polyacrylates as Additives in Ordinary Portland Cement Mortar
Chemical Engineering & Technology, 2014Co-Authors: Katja Ohenoja, Sandra Breitung-faes, Paivo Kinnunen, Mirja Illikainen, Juha Saari, Arno Kwade, Jouko NiinimäkiAbstract:Sodium polyacrylates permit a higher solids concentration during Grinding, reducing the resulting particle size and/or specific energy consumption. Their impact on fine and ultrafine Grinding of limestone was studied. Sodium polyacrylate with a low polydispersity index was found to be the most effective Grinding aid for limestone and consequently applied for further nano-Grinding experiments. Nano-Grinding was most energy-efficient with the smallest Grinding Medium size. These ground nano-sized CaCO3 particles with sodium polyacrylate on the surface accelerated the hydration of ordinary Portland cement cement paste.
