“…It can also be seen from a comparison with reported mean pore sizes of typical SGAs produced with industrial flash calciners ( presented as the open symbols in Fig. 10), 28,32,34 the solar process generates larger values of d pore for a given value of X than does the conventional process. Extrapolation suggests that d pore will continue to increase with X, so that solar-processed alumina has potential to achieve a larger mean pore size than the majority of conventionally-processed aluminas, noting the exception for two SGAs with pore size larger than 8 nm.…”
“…Table 3b presents the parameters used to characterise the product quality for the present alumina product with greatest X (run #14), together with typical properties of SGA produced in industrial flash calciners as reported in the literature. 24,28,29,[31][32][33][34] This shows that the minimum LoI 1273 of 1.20% achieved in the present investigation is somewhat higher than the typical value of alumina produced in industrial flash calciners. However, given that extent of conversion increases with τ, it can be deduced that the LoI 1273 would decrease to <1% with scale up of the solar reactor, which would comply with industrial requirements.…”
Section: Projection To a 50 Mw Solar Vortex Transport Reactor And Comparison Of The Product Quality With The Conventional Processmentioning
confidence: 71%
“…where, n Al 2 O 3 and n Al(OH) 3 are the molar quantities of alumina product and unreacted Al(OH) 3 in the solar-processed alumina (as determined from LoI X ). The ISO standard for reporting alumina moisture content is by the LoI 1273 , evaluated over the temperature range 573-1273 K. 30,34,38 However, it has been shown that the reactant Al(OH) 3 begins to decompose at temperatures below 573 K, which means that the LoI 1273 underestimates the amount of unreacted Al(OH) 3 . This provides justification for the use of LoI ads and LoI X in the present investigation.…”
Section: Product Characterisationmentioning
confidence: 99%
“…Also shown with open symbols are the typical mean pore diameter of nine SGAs produced with industrial calciners as reported in the literature. 28,32,34 Fig. 11 Specific surface area, SSA, of the present solar-produced aluminas as a function of the extent of chemical conversion, X, for experimental runs 1 to 17.…”
“…Hence the final α-alumina has the lowest SSA of the various alumina phases, 6,7,23,33 and there is a trade-off between the desire to obtain both a low residual water content and a high SSA. 29,34 It has been proposed, however, that under rapid heating, such as tends to occur with flash calcination, the structural rearrangement of the gibbsite calcination sequence can be decoupled from the water removal. 33 The high heating rates possible with directly irradiated CST therefore offer the potential to produce alumina with both favourable residual moisture content and favourable microstructural properties.…”
“…It can also be seen from a comparison with reported mean pore sizes of typical SGAs produced with industrial flash calciners ( presented as the open symbols in Fig. 10), 28,32,34 the solar process generates larger values of d pore for a given value of X than does the conventional process. Extrapolation suggests that d pore will continue to increase with X, so that solar-processed alumina has potential to achieve a larger mean pore size than the majority of conventionally-processed aluminas, noting the exception for two SGAs with pore size larger than 8 nm.…”
“…Table 3b presents the parameters used to characterise the product quality for the present alumina product with greatest X (run #14), together with typical properties of SGA produced in industrial flash calciners as reported in the literature. 24,28,29,[31][32][33][34] This shows that the minimum LoI 1273 of 1.20% achieved in the present investigation is somewhat higher than the typical value of alumina produced in industrial flash calciners. However, given that extent of conversion increases with τ, it can be deduced that the LoI 1273 would decrease to <1% with scale up of the solar reactor, which would comply with industrial requirements.…”
Section: Projection To a 50 Mw Solar Vortex Transport Reactor And Comparison Of The Product Quality With The Conventional Processmentioning
confidence: 71%
“…where, n Al 2 O 3 and n Al(OH) 3 are the molar quantities of alumina product and unreacted Al(OH) 3 in the solar-processed alumina (as determined from LoI X ). The ISO standard for reporting alumina moisture content is by the LoI 1273 , evaluated over the temperature range 573-1273 K. 30,34,38 However, it has been shown that the reactant Al(OH) 3 begins to decompose at temperatures below 573 K, which means that the LoI 1273 underestimates the amount of unreacted Al(OH) 3 . This provides justification for the use of LoI ads and LoI X in the present investigation.…”
Section: Product Characterisationmentioning
confidence: 99%
“…Also shown with open symbols are the typical mean pore diameter of nine SGAs produced with industrial calciners as reported in the literature. 28,32,34 Fig. 11 Specific surface area, SSA, of the present solar-produced aluminas as a function of the extent of chemical conversion, X, for experimental runs 1 to 17.…”
“…Hence the final α-alumina has the lowest SSA of the various alumina phases, 6,7,23,33 and there is a trade-off between the desire to obtain both a low residual water content and a high SSA. 29,34 It has been proposed, however, that under rapid heating, such as tends to occur with flash calcination, the structural rearrangement of the gibbsite calcination sequence can be decoupled from the water removal. 33 The high heating rates possible with directly irradiated CST therefore offer the potential to produce alumina with both favourable residual moisture content and favourable microstructural properties.…”
In the aluminium industry today, smelters often have to rely on more than one alumina supplier. This creates diversity in the properties of smelter grade alumina (SGA). A method has been developed to compare the HF formation from aluminas containing different amounts of water. The water content of the different aluminas was determined by loss on ignition tests (LOI) and thermal gravimetric analysis (TGA). Further, the aluminas were added to a cryolitic melt kept in a gas tight furnace with a constant nitrogen flow rate. The HF concentration in the off gas during the alumina additions was measured in-situ using a tunable diode laser. A correlation between the quantity of water found from LOI characterisation and the amount of HF formed has been found. It was also found that in this laboratory setup, all types of water contribute to HF formation; structural hydroxyl, physisorbed and chemisorbed water.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.