Atomization performance of petroleum coke and coal water slurries from a twin fluid atomizer

Abstract

This paper presents the atomization performance of a sub-bituminous coal and petroleum coke water slurries from an internally mixed twin fluid swirl atomizer. Solid fuel water slurry (SFWS) atomization involves interactions between three different phases; solid, liquid and the atomizing gas. The geometrical properties of the nozzle play an important role in determining the atomization characteristics of slurry fuels. Geometric characteristics of the nozzle, the density ratio between the liquid and the atomizing gas, injection pressure differential with respect to ambient conditions (ΔP), the working fluid temperature, slurry viscosity and the solid particle size distribution are some of these properties that affect the SFWS spray characteristics. In this study, the SFWS spray is characterized using a combination of Phase Doppler Anemometry (Dantec Dynamics, Ramsey, NJ) and a Mie scattering technique in an optically accessible pressure vessel. The vessel’s ambient pressure was set at 15bars and the flow rates of the slurry and atomizing gas was 80kg/h and 40kg/h, respectively. A method of image processing was developed in order to quantify the time resolved spray angle. The Mie scattering images confirmed the asymmetry of the spray. The petroleum coke water slurry was found to produce the best atomization performances as the hollow spray angle was found to be steadier than the coal SFWS. The droplet SMD of the petroleum coke and coal slurry was found to be 218 and 198μm, respectively. The droplet size class also demonstrates how the injection track of droplets increases with the size class. A Rosin–Rammler size distribution is fitted to both fuels tested in this study. The petroleum coke size distribution was found to be more dispersed and demonstrated larger size statistics than the coal water slurry. The spray velocity field suggests a wider spray angle for the petroleum coke while larger spray velocities were identified in the coal slurry. Both PDA and Mie scattering spray angles are in agreement with each other.