Heat and mass transfer characteristics during spray drying of Na2Fe0.6Mn0.4PO4F/C cathode material for Na-ion batteries

Abstract

The paper presents a detailed experimental investigation on heat and mass transfer characteristics during the synthesis of Na2Fe0.6Mn0.4PO4F/C using intermittent spray drying. The drying process is carried out in a custom-made spray dryer. The novelty of the work is the study of the effect of intermittency on the spray drying process heat and mass transfer characteristics using a volumetric approach. The nozzle orifice diameter, spray duration, and spray pressure are operating parameters of the process that are varied between 0.2 and 0.4 mm at 10 and 40 sand 4 and 7 bar. An increase in nozzle orifice diameter and pumping pressure improves the heat transfer significantly; however, an increase in spray time diminishes the heat transfer. Under considered operating conditions, the volumetric heat transfer coefficient varied between 1.5 and 3.5 kW/m3K. The volumetric mass transfer coefficient ranges between 2.5 and 5.0 s−1. Based on the study, correlations for heat and mass transfer coefficients have been developed that relate the thermophysical properties of both the carrier gas and the precursor fluid in terms of Ohnesorge number and Reynolds number.