Numerical and experimental investigation on heat and mass transfer characteristics during nozzle spray drying of active cathode material

Abstract

Spray drying technique is used to produce dry powder by rapid evaporation of atomized solution or slurry under a hot gaseous ambient. Due to the improved particle shape, small particle size, and quick drying of the solution, the technique has attracted considerable interest. Depending on the product, spray drying can be performed either in continuous or intermittent mode. Under continuous mode, the chamber temperature continuously decreases, and the chamber tends to achieve an equilibrium temperature gradient. The wet-bulb temperature of the carrier gas at the chamber exit may fall below the temperature of the dried particles, leading to the re-hydration of dried particles and collapse of the entire process. Under intermittent drying, the feed solution is sprayed intermittently and the chamber can regain its temperature during the non-spray period. Conventionally, intermittency in the drying process is achieved by pulsating the properties of the carrier gas medium, whereas in this work the same is achieved by pulsating the properties of the nozzle spray. Though there is a large amount of research work available with respect to the characteristics of the end-dried product, the research work related to heat and mass transfer characteristics during the process is minimal. It is needless to mention that the overall performance of the process and the quality of the dried product depends on the mechanism of heat and mass transfer.