Fluidization characteristics of lithium-titanate in gas-solid fluidized bed

Experiments were conducted to investigate the hydrodynamic behaviour of lithium titanate (Li2TiO3) in gas-solid fluidized bed. The objective of the study was to study the fluidization properties of Li2TiO3 particles. These studies will be useful to find the applicability of fluidization to increase the effective thermal conductivity and wall to bed heat transfer coefficient of Li2TiO3 particulate bed in test blanket module of fusion reactor. Li2TiO3 was synthesized by solid state reaction process and different particle sizes were classified. Experiments were conducted in a cylindrical column of 90 mm diameter and 650 mm height in perspex material with metallic distributor plate. Dry compressed air was used as fluidizing medium. From the experiments it was observed that Li2TiO3 is fluidizable, but severe slugging and bubbling were observed in the fluidized bed. Minimum fluidization and bubbling velocity of Li2TiO3 particles were determined and compared to that of white sand of similar particle size and density. The experimental details and observations are discussed in this paper.

► The hydrodynamic behaviour of Li2TiO3 particles in gas fluidized bed was studied. Minimum fluidization and minimum bubbling velocity of different particle sizes were investigated. The ratios of the minimum bubbling velocity to the minimum fluidization velocity are close to one, and so Li2TiO3 particles of studied ranges fall under Geldart Group B, as the particle size to be used higher than 100μm, particle density >2500 kg/m3 and fluidized behaviour similar to the particles of Group B as described by Geldart [22]. Hydrodynamic behaviour of Li2TiO3 is quite similar to that of white sand. Though the Li2TiO3 has higher particle density than that of white sand, the former has less umf for higher particle sizes. At higher operating velocity, less pressure fluctuation was observed in the fluidized bed of Li2TiO3 particles compared to that of white sand.
► The experimental findings show that Li2TiO3 particles are fluidizable. The fluidization technique may be applicable to enhance heat transfer characteristics as discussed earlier. However, as the Li2TiO3 particles fall under Geldart-B category, helium velocity in TBM is restricted, and high packing density is desirable the packed fluidization may be applicable for effective enhancement of the heat transfer properties.
► In the study air was used as the fluidizing medium. However, in TBM, helium will be used as coolant as well as fluidizing medium and helium has different properties than air. Similar study with helium is required though similar hydrodynamic behaviour is expected. From the study it can be concluded that fluidization technique may be applicable for the effective heat removal from particulate bed of Li2TiO3 in TBM and to be found experimentally. However, the operating fluidization velocity, bed voidage etc. are the major issues and need to be considered.